Artykuły w czasopismach na temat „Sin1 Isoforms”

The mTOR (mammalian target of rapamycin) protein kinase is an important regulator of cell growth. Two complexes of mTOR have been identified: complex 1, consisting of mTOR–Raptor (regulatory associated protein of mTOR)–mLST8 (termed mTORC1), and complex 2, comprising mTOR–Rictor (rapamycininsensitive companion of mTOR)–mLST8–Sin1 (termed mTORC2). mTORC1 phosphorylates the p70 ribosomal S6K (S6 kinase) at its hydrophobic motif (Thr389), whereas mTORC2 phosphorylates PKB (protein kinase B) at its hydrophobic motif (Ser473). In the present study, we report that widely expressed isoforms of unstudied proteins termed Protor-1 (protein observed with Rictor-1) and Protor-2 interact with Rictor and are components of mTORC2. We demonstrate that immunoprecipitation of Protor-1 or Protor-2 results in the co-immunoprecipitation of other mTORC2 subunits, but not Raptor, a specific component of mTORC1. We show that detergents such as Triton X-100 or n-octylglucoside dissociate mTOR and mLST8 from a complex of Protor-1, Sin1 and Rictor. We also provide evidence that Rictor regulates the expression of Protor-1, and that Protor-1 is not required for the assembly of other mTORC2 subunits into a complex. Protor-1 is a novel Rictor-binding subunit of mTORC2, but further work is required to establish its role.

The mTOR (mammalian target of rapamycin) protein kinase is an important regulator of cell growth and is a key target for therapeutic intervention in cancer. Two complexes of mTOR have been identified: complex 1 (mTORC1), consisting of mTOR, Raptor (regulatory associated protein of mTOR) and mLST8 (mammalian lethal with SEC13 protein 8) and complex 2 (mTORC2) consisting of mTOR, Rictor (rapamycin-insensitive companion of mTOR), Sin1 (stress-activated protein kinase-interacting protein 1), mLST8 and Protor-1 or Protor-2. Both complexes phosphorylate the hydrophobic motifs of AGC kinase family members: mTORC1 phosphorylates S6K (S6 kinase), whereas mTORC2 regulates phosphorylation of Akt, PKCα (protein kinase Cα) and SGK1 (serum- and glucocorticoid-induced protein kinase 1). To investigate the roles of the Protor isoforms, we generated single as well as double Protor-1- and Protor-2-knockout mice and studied how activation of known mTORC2 substrates was affected. We observed that loss of Protor-1 and/or Protor-2 did not affect the expression of the other mTORC2 components, nor their ability to assemble into an active complex. Moreover, Protor knockout mice display no defects in the phosphorylation of Akt and PKCα at their hydrophobic or turn motifs. Strikingly, we observed that Protor-1 knockout mice displayed markedly reduced hydrophobic motif phosphorylation of SGK1 and its physiological substrate NDRG1 (N-Myc downregulated gene 1) in the kidney. Taken together, these results suggest that Protor-1 may play a role in enabling mTORC2 to efficiently activate SGK1, at least in the kidney.

Sinn, Patrick L., and Curt D. Sigmund. Identification of three human renin mRNA isoforms from alternative tissue-specific transcriptional initiation. Physiol Genomics 3: 25–31, 2000.—We have reported that mice transgenic for 140- and 160-kb P1 phage artificial chromosomes (PACs) containing the human renin gene express the gene in a highly tissue-restricted and regulated manner. Herein, we demonstrate that the transgene is also expressed appropriately throughout development. In the course of this investigation, we identified the existence of three transcriptional isoforms of human renin mRNA derived from the utilization of alternative transcription start sites. The first isoform is the kidney-specific isoform, which utilizes the classic renin promoter. The second is a brain-specific isoform, which when previously identified in rats and mice was due to a transcription initiation site within intron A. However, the start site in the human gene resides ∼1,325 bp upstream of the classic promoter and encodes a new exon 1 (termed exon 1b) that splices directly to exon 2. The third isoform is lung specific and is due to transcriptional initiation 79 bp directly upstream of exon 2, fusing additional DNA within intron A (termed exon 1c) directly to exon 2 without splicing. Importantly, the alternative first exons observed in the PAC transgenic mice were identical to those used to transcribe renin in human fetal kidney, brain, and lung, suggesting these sites are bona fide isoforms of human renin mRNA and not artifacts of transgenesis. Moreover, the subtle differences in tissue-specific transcriptional initiation observed in the renin gene of rats and humans can be faithfully and accurately emulated in a transgenic model.

The real-time quantification of target engagement (TE) by small-molecule ligands in living cells remains technically challenging. Systematic quantification of such interactions in a high-throughput setting holds promise for identification of target-specific, potent small molecules within a pathophysiological and biologically relevant cellular context. The salt-inducible kinases (SIKs) belong to a subfamily of the AMP-activated protein kinase (AMPK) family and are composed of three isoforms in humans (SIK1, SIK2, and SIK3). They modulate the production of pro- and anti-inflammatory cytokines in immune cells. Although pan-SIK inhibitors are sufficient to reverse SIK-dependent inflammatory responses, the apparent toxicity associated with SIK3 inhibition suggests that isoform-specific inhibition is required to realize therapeutic benefit with acceptable safety margins. Here, we used the NanoBRET TE intracellular kinase assay, a sensitive energy transfer technique, to directly measure molecular proximity and quantify TE in HEK293T cells overexpressing SIK2 or SIK3. Our 384-well high-throughput screening of 530 compounds demonstrates that the NanoBRET TE intracellular kinase assay was sensitive and robust enough to reveal differential engagement of candidate compounds with the two SIK isoforms and further highlights the feasibility of high-throughput implementation of NanoBRET TE intracellular kinase assays for target-driven small-molecule screening.

RAS proteins are molecular switches that interact with effector proteins when bound to guanosine triphosphate, stimulating downstream signaling in response to multiple stimuli. Although several canonical downstream effectors have been extensively studied and tested as potential targets for RAS-driven cancers, many of these remain poorly characterized. In this study, we undertook a biochemical and structural approach to further study the role of Sin1 as a RAS effector. Sin1 interacted predominantly with KRAS isoform 4A in cells through an atypical RAS-binding domain that we have characterized by X-ray crystallography. Despite the essential role of Sin1 in the assembly and activity of mTORC2, we find that the interaction with RAS is not required for these functions. Cells and mice expressing a mutant of Sin1 that is unable to bind RAS are proficient for activation and assembly of mTORC2. Our results suggest that Sin1 is a bona fide RAS effector that regulates downstream signaling in an mTORC2-independent manner.

ABSTRACT The highly related mammalian Sin3A and Sin3B proteins provide a versatile platform for chromatin-modifying activities. Sin3-containing complexes play a role in gene repression through deacetylation of nucleosomes. Here, we explore a role for Sin3 in myogenesis by examining the phenotypes resulting from acute somatic deletion of both isoforms in vivo and from primary myotubes in vitro. Myotubes ablated for Sin3A alone, but not Sin3B, displayed gross defects in sarcomere structure that were considerably enhanced upon simultaneous ablation of both isoforms. Massively parallel sequencing of Sin3A- and Sin3B-bound genomic loci revealed a subset of target genes directly involved in sarcomere function that are positively regulated by Sin3A and Sin3B proteins. Both proteins were coordinately recruited to a substantial number of genes. Interestingly, depletion of Sin3B led to compensatory increases in Sin3A recruitment at certain target loci, but Sin3B was never found to compensate for Sin3A loss. Thus, our analyses describe a novel transcriptional role for Sin3A and Sin3B proteins associated with maintenance of differentiated muscle cells.

PGC1α is a transcriptional coactivator in peripheral tissues, but its function in the brain remains poorly understood. Various brain-specific Pgc1α isoforms have been reported in mice and humans, including two fusion transcripts (FTs) with non-coding repetitive sequences, but their function is unknown. The FTs initiate at a simple sequence repeat locus ∼570 Kb upstream from the reference promoter; one also includes a portion of a short interspersed nuclear element (SINE). Using publicly available genomics data, here we show that the SINE FT is the predominant form of Pgc1α in neurons. Furthermore, mutation of the SINE in mice leads to altered behavioural phenotypes and significant up-regulation of genes in the female, but not male, cerebellum. Surprisingly, these genes are largely involved in neurotransmission, having poor association with the classical mitochondrial or antioxidant programs. These data expand our knowledge on the role of Pgc1α in neuronal physiology and suggest that different isoforms may have distinct functions. They also highlight the need for further studies before modulating levels of Pgc1α in the brain for therapeutic purposes.

Abstract Glucose metabolism plays a key role in thymocyte development. The mammalian target of rapamycin complex 2 (mTORC2) is a critical regulator of cell growth and metabolism, but its role in early thymocyte development and metabolism has not been fully studied. We show here that genetic ablation of Sin1, an essential component of mTORC2, in T lineage cells results in severely impaired thymocyte development at the CD4−CD8− double negative (DN) stages but not at the CD4+CD8+ double positive (DP) or later stages. Notably, Sin1-deficient DN thymocytes show markedly reduced proliferation and glycolysis. Importantly, we discover that the M2 isoform of pyruvate kinase (PKM2) is a novel and crucial Sin1 effector in promoting DN thymocyte development and metabolism. At the molecular level, we show that Sin1–mTORC2 controls PKM2 expression through an AKT-dependent PPAR-γ nuclear translocation. Together, our study unravels a novel mTORC2−PPAR-γ−PKM2 pathway in immune-metabolic regulation of early thymocyte development.

The salt-inducible kinases (SIKs) control a novel molecular switch regulating macrophage polarization. Pharmacological inhibition of the SIKs induces a macrophage phenotype characterized by the secretion of high levels of anti-inflammatory cytokines, including interleukin (IL)-10, and the secretion of very low levels of pro-inflammatory cytokines, such as tumour necrosis factor α. The SIKs, therefore, represent attractive new drug targets for the treatment of macrophage-driven diseases, but which of the three isoforms, SIK1, SIK2 or SIK3, would be appropriate to target remains unknown. To address this question, we developed knock-in (KI) mice for SIK1, SIK2 and SIK3, in which we introduced a mutation that renders the enzymes catalytically inactive. Characterization of primary macrophages from the single and double KI mice established that all three SIK isoforms, and in particular SIK2 and SIK3, contribute to macrophage polarization. Moreover, we discovered that inhibition of SIK2 and SIK3 during macrophage differentiation greatly enhanced the production of IL-10 compared with their inhibition in mature macrophages. Interestingly, macrophages differentiated in the presence of SIK inhibitors, MRT199665 and HG-9-91-01, still produced very large amounts of IL-10, but very low levels of pro-inflammatory cytokines, even after the SIKs had been reactivated by removal of the drugs. Our data highlight an integral role for SIK2 and SIK3 in innate immunity by preventing the differentiation of macrophages into a potent and stable anti-inflammatory phenotype.

Six putative α-galactosidase genes (α-Gals), three acid forms (CsGAL1, CsGAL2, CsGAL3) and three alkaline forms (CsAGA1, CsAGA2, CsAGAL3), were found in the cucumber genome. It is interesting to know the expression pattern and possible function of these α-Gals in the cucumber plant since it is a stachyose-translocating species. In this study, full-length cDNAs of six α-Gals were cloned and heterologously expressed. The result showed that all recombinant proteins revealed acid or alkaline α-Gal activities with different substrate specificities and pH or temperature responding curves, indicating their distinct roles in cucumber plants. Phylogenetic analysis of collected α-Gal amino acid sequences from different plants indicated that the ancestor of both acid and alkaline α-Gals existed before monocots and dicots separated. Generally, six α-Gal genes are universally expressed in different cucumber organs. CsGAL2 highly expressed in fasting-growing leaves, fruits and germinating seeds; CsGAL3 mainly distributes in vacuoles and significantly expressed in cucumber fruits, senescent leaves and seeds during late stage germination; The expression of CsAGA1 increased from leaf 1 to leaf 3 (sink leaves) and then declined from leaf 4 to leaf 7 (source leaves), and this isoform also highly expressed in male flowers and germinating seeds at early stage; CsAGA2 significantly expressed in cucumber leaves and female flowers; CsAGA3 is localized in plastids and also actively expressed in senescent leaves and germinating seeds; The role of CsGAL1 in cucumber plants is now unclear since its expression was relatively low in all organs. According to their expression patterns, subcellular localizations and previously reported functions of these isoforms in other plants, combining the data of soluble sugars contents in different tissues, the possible functions of these α-Gals were discussed.

Activity of mushroom polyphenol oxidase (PPO) toward 6 substrates and inhibitory effect of cysteine, 2-mercaptoethanol, benzoic acid and sodium metabisulphite were determined. The o-diphenols which appeared to be the best substrates were: catechin, DOPA (L-3,4-dihydro-xyphenylalanine) and chlorogcnic acid. Affinity of PPO crude preparation substrates to enzyme, expressed as inverse value of Michaelis constant was lower then affinity of catechol. Inhibitory effect depended on specifity of inhibitors and their concentration. Electrophoretic patterns of PPO of mushrooms reveals slow and fast moving 4 isoforms when DOPA was used as a substrate, 2 bands for catechin and chlorogenic acid while only one band showed activity toward tyrosine and p-cresol.

cAMP responsive element binding protein (CREB)-regulated transcription coactivators (CRTCs) regulate gene transcription in response to an increase in intracellular cAMP or Ca2+ levels. To date, three isoforms of CRTC have been identified in mammals. All CRTCs are widely expressed in various regions of the brain. Numerous studies have shown the importance of CREB and CRTC in energy homeostasis. In the brain, the paraventricular nucleus of the hypothalamus (PVH) plays a critical role in energy metabolism, and CRTC1 and CRTC2 are highly expressed in PVH neuronal cells. The single-minded homolog 1 gene (Sim1) is densely expressed in PVH neurons and in some areas of the amygdala neurons. To determine the role of CRTCs in PVH on energy metabolism, we generated mice that lacked CRTC1 and CRTC2 in Sim1 cells using Sim-1 cre mice. We found that Sim1 cell-specific CRTC1 and CRTC2 double-knockout mice were sensitive to high-fat diet (HFD)-induced obesity. Sim1 cell-specific CRTC1 and CRTC2 double knockout mice showed hyperphagia specifically for the HFD, but not for the normal chow diet, increased fat mass, and no change in energy expenditure. Interestingly, these phenotypes were stronger in female mice than in male mice, and a weak phenotype was observed in the normal chow diet. The lack of CRTC1 and CRTC2 in Sim1 cells changed the mRNA levels of some neuropeptides that regulate energy metabolism in female mice fed an HFD. Taken together, our findings suggest that CRTCs in Sim1 cells regulate gene expression and suppress excessive fat intake, especially in female mice.

Abstract The emergence of new genes and functions is of paramount importance in the emergence of new animal species. For example, the insertion of the mobile element Tigger 2 into the sequence of the functional gene POU2F1 in primates led to the formation of a new chimeric primate-specific isoform POU2F1Z, the translation of which is activated under cellular stress. Its mRNA was found in all species of monkeys, starting with macaques. Analysis of the fragments of the Tigger2 copy corresponding to the human exon Z showed that the splicing sites of exon Z are homologous in humans and in most monkeys, with the exception of lemurs and galagos. The stop codon introduced into the mRNA by the Tigger2 sequence is present in all primates, starting with macaques. The internal ATG codon is also present in all primates, with the exception of lemurs and galagos. In the course of evolution, other MGEs, mainly of the SINE type, were inserted into the Tigger2 copy. In the course of evolution, both the location and the number of mobile SINE elements within the POU2F1 gene changed. Starting with macaques, the pattern of the arrangement of SINE elements within the Tigger2 copy in the studied region of the POU2F1 gene was fixed and then remained unchanged in other primates and humans, which may indicate its functional significance.

Epigenetic gene silencing is one of the fundamental mechanisms for ensuring proper gene expression patterns during cellular differentiation and development. Histone deacetylases (HDACs) are evolutionally conserved enzymes that remove acetyl modifications from histones and play a central role in epigenetic gene silencing. In cells, HDAC forms a multiprotein complex (HDAC complex) in which the associated proteins are believed to help HDAC carry out its cellular functions. Though each HDAC complex contains distinct components, the presence of isoforms for some of the components expands the variety of complexes and the diversity of their cellular roles. Recent studies have also revealed a functional link between HDAC complexes and specific histone demethylases. In this paper, we summarize the distinct and cooperative roles of four class I HDAC complexes, Sin3, NuRD, CoREST, and NCoR/SMRT, with respect to their component diversity and their relationship with specific histone demethylases.

ZusammenfassungLipoprotein (a) (Lp[a]) ist ein Apolipoprotein-B-haltiges Lipoprotein, welches dem Low Density Lipoprotein (LDL) sehr ähnlich ist, zusätzlich jedoch noch ein charakteristisches Protein, das Apo-a, enthält. Letzteres weist eine große Homologie zu Plasminogen auf. Lp(a) verhält sich stoffwechselmäßig deutlich anders als LDL und gilt heute als das atherogenste Lipoprotein. Seine Funktion ist noch weitgehend unbekannt, und Personen ohne nachweisbare Mengen Lp(a) im Blut sind vollständig gesund.Apo-a hat ein sehr hohes Molekulargewicht und kommt in mehr als 10 Isoformen vor, welche sich durch die Anzahl der Kringel-4-Repeats unterscheiden. Diese Strukturen sind auch dafür verantwortlich, daß Lp(a) die Aktivierung von Plasminogen zu Plasmin auf verschiedenste Weise inhibiert. Trotzdem konnte bis heute in vivo noch keine Korrelation der Plasma-LP(a)-Konzentrationen mit der fibrinolytischen Aktivität im Plasma nachgewiesen werden.

ZusammenfassungFür eine optimale visuelle Funktion ist eine Augenoberfläche mit einem vitalen Epithelverband und stabilen Tränenfilm erforderlich. Eine Vielzahl von endogenen und externen Faktoren kann die empfindliche Homöostase der Augenoberfläche beeinflussen und zu einem „trockenen Auge“ führen. Studien im letzten Jahrzehnt haben gezeigt, dass Ca2+ ein wichtiger Faktor bei der Kontrolle der Epithelfunktion der Augenoberfläche ist. Dabei konnten insbesondere transiente Rezeptorpotenzialkanäle (TRPs) als wichtige Komponenten in Hornhaut- und Bindehautzellen identifiziert werden. Die TRPs sind nicht selektive Kationenkanäle, die als molekulare Sensoren wärme-, nozi- bzw. osmosensibel sind. Unsere Ca2+-Imaging- und Patch-Clamp-Studien zeigen, dass die Aktivität von 2 TRP-Isoformen, TRPV1 und TRPM8, durch Änderungen der Osmolarität, der Außentemperatur und einiger endogener Substrate moduliert werden kann. Diese TRPs werden sowohl an nicht neuronalen als auch an neuronalen Hornhautzellen exprimiert. Darüber hinaus beeinflussen diese Wechselwirkungen die Expression von Zytokinen, die inflammatorische Prozesse fördern oder hemmen und damit einen wichtigen Beitrag zur Physiologie des Trockenen Auges leisten. Zusammengenommen führen diese Ergebnisse nicht nur zu einem besseren Verständnis der Pathophysiologie von Schmerz- und Entzündungsreaktionen der Augenoberfläche. Diese Studien können auch neue Wege aufzeigen, um die Pathophysiologie der Krankheit zu verstehen und die Entwicklung neuer therapeutischer Angriffspunkte beim Syndrom des Trockenen Auges fördern.

ZusammenfassungIrinotecan wird seit mehr als zwei Jahrzehnten in unterschiedlichen Arzneiformen, auch in Kombination mit anderen Arzneistoffen, zur Behandlung einiger Tumorerkrankungen eingesetzt. Irinotecan, ein Prodrug, wird über die Butyrylcholinesterase und über die Carboxylesterasen CES1 und CES2 in die aktive Form SN-38 (7-Ethyl-10-hydroxycamptothecin) verstoffwechselt. SN-38 ist ein starker Topoisomerase-I-Inhibitor. Aufgrund des komplexen Metabolisierungsweges von Irinotecan und wegen der engen therapeutischen Breite des Arzneistoffes ist die klinische Relevanz einer Interaktion zwischen bioaktiven Sekundärmetaboliten und Irinotecan von vielen unterschiedlichen Einflussfaktoren abhängig und kann daher nur im Rahmen einer individualmedizinischen Betreuung Bedeutung haben. Sowohl die Butyrylcholinesterase und die Carboxylesterasen CES1, CES2 als auch CYP3A4, CYP3A5, UGT1A-Isoforme und Transportproteine sind an der Verstoffwechselung und Eliminierung von Irinotecan beteiligt und limitieren die Verfügbarkeit des aktiven Metaboliten SN-38. Inhibition oder Induktion dieser Enzyme durch bioaktive Sekundärmetabolite könnten die therapeutische Wirksamkeit des Irinotecan-Metaboliten SN-38 beeinflussen und für die Ausbildung von Nebenwirkungen ursächlich sein. Der folgende Artikel versucht, einige mögliche Interaktionen abzuschätzen und aufzuzeigen.

Previous experiments using heat exchangers (liquid cooled blocks) to chill a portion of plant stem have shown a transient stoppage in phloem translocation and an increase in measured phloem pressure. Although a chilled-induced stoppage of phloem transport has been known for over 100 years, the mechanism of this phenomenon is still poorly understood. Recently, work has highlighted that aquaporins occur within the plasma membrane of the sieve tubes along the entire source-to-sink pathway, and that isoforms of these water channel proteins may change dynamically. Aquaporins show regulatory roles in controlling tissue and cellular water status in response to environmental hardships. Thus, we tested if protein localization and mRNA transcript abundance changes occur in response to chilling in balsam poplar (Populus balsamifera) using immunohistochemistry and qrtPCR. The results of the immunolocalization experiments show that the labeling intensity of the sieve elements treated for only 2 min of chill time significantly increased for PIP2. After 10 min of chilling, this signal declined significantly to lower than that of the pre-chilled sieve elements. Overall, the abundance of mRNA transcript increased for the tested PIP2s following cold application. We discuss the implication that aquaporins are responsible for the alleviation of sieve tube pressure and the resumption of flow following a cold-induced blockage event.

A number of signal transduction pathways are activated during Acute Kidney Injury (AKI). Of particular interest is the Salt Inducible Kinase (SIK) signaling network, and its effects on the Renal Proximal Tubule (RPT), one of the primary targets of injury in AKI. The SIK1 network is activated in the RPT following an increase in intracellular Na+ (Na+in), resulting in an increase in Na,K-ATPase activity, in addition to the phosphorylation of Class IIa Histone Deacetylases (HDACs). In addition, activated SIKs repress transcriptional regulation mediated by the interaction between cAMP Regulatory Element Binding Protein (CREB) and CREB Regulated Transcriptional Coactivators (CRTCs). Through their transcriptional effects, members of the SIK family regulate a number of metabolic processes, including such cellular processes regulated during AKI as fatty acid metabolism and mitochondrial biogenesis. SIKs are involved in regulating a number of other cellular events which occur during AKI, including apoptosis, the Epithelial to Mesenchymal Transition (EMT), and cell division. Recently, the different SIK kinase isoforms have emerged as promising drug targets, more than 20 new SIK2 inhibitors and activators having been identified by MALDI-TOF screening assays. Their implementation in the future should prove to be important in such renal disease states as AKI.

Starch is the most widespread and abundant storage carbohydrate in plants. We depend upon starch for our nutrition, exploit its unique properties in industry, and use it as a feedstock for bio-ethanol production. Starch is stored in the form of osmotically inactive, water-insoluble granules in amyloplasts (storage starch) and chloroplasts (transitory starch). The biosynthesis of starch involves not only the production of the composite glucans but also their arrangement into an organized form within the starch granule. Understanding the specific functions played by individual isoforms of enzymes involved in starch biosynthesis pathways will provide important basis for regulation of starch production in plant. A transcript-level analysis of the genes which encode starch-synthesis enzymes is fundamental for assessment of enzyme function and the regulatory mechanism for starch biosynthesis in source and sink organs. In this work, the expression level of the genes encoding ADP-glucose pyrophosphorylase (AGPase) in two local varieties Do Dia Phuong (Do DF) and Trang Hoa Binh (Trang HB) as well as two imported varieties KM94 (Rayong1 X Rayong 90) and KM140 (KM98-1 x KM36) with different starch contents were evaluated by quantitative real-time PCR method. The result of transcript level analysis made the expression profiles of cassava AGPS and AGPL genes (encoding AGPase small and large subunits) during three development periods, 90, 180 and 270 DAP (day after planting). The transcriptional activities of these genes exhibited tissue-specific expression patterns. In particular, AGPS2 and AGPL1 transcripts were predominant in leaves, whereas expression of AGPS1, AGPL2, and AGPL3 appeared to be mostly confined to storage roots. Despite of having disparities between development stages, expression patterns of both AGPS2 and AGPL1 in leaves did not show significant differences amongst investigated cassava varieties. In contrast, transcriptional activities of AGPS1 and AGPL3 in tubers had patterns directly related to the starch contents of the cultivars. These results indicated that AGPS1 and AGPL3 genes likely play an important role in the starch biosynthesis pathway and have potential for regulation of starch production in cassava.

Invertases are key enzymes in carbon partitioning in higher plants. They gain additional importance in the distribution of carbohydrates in the event of wounding or pathogen attack. Although many researchers have found an increase in invertase activity upon infection, only a few studies were able to determine whether the source of this activity was host or parasite. This article analyzes the role of invertases involved in the biotrophic interaction of the rust fungus Uromyces fabae and its host plant, Vicia faba. We have identified a fungal gene, Uf-INV1, with homology to invertases and assessed its contribution to pathogenesis. Expression analysis indicated that transcription began upon penetration of the fungus into the leaf, with high expression levels in haustoria. Heterologous expression of Uf-INV1 in Saccharomyces cerevisiae and Pichia pastoris allowed a biochemical characterization of the enzymatic activity associated with the secreted gene product INV1p. Expression analysis of the known vacuolar and cell-wall-bound invertase isoforms of V. faba indicated a decrease in the expression of a vacuolar invertase, whereas one cell-wall-associated invertase exhibited increased expression. These changes were not confined to the infected tissue, and effects also were observed in remote plant organs, such as roots. These findings hint at systemic effects of pathogen infection. Our results support the hypothesis that pathogen infection establishes new sinks which compete with physiological sink organs.

The neural isoforms of agrin can stimulate transcription of the acetylcholine receptor (AChR) ε subunit gene in electrically active muscle fibers, as does the motor neuron upon the formation of a neuromuscular junction. It is not clear, however, whether this induction involves neuregulins (NRGs), which stimulate AChR subunit gene transcription in vitro by activating ErbB receptors. In this study, we show that agrin- induced induction of AChR ε subunit gene transcription is inhibited in cultured myotubes overexpressing an inactive mutant of the ErbB2 receptor, demonstrating involvement of the NRG/ErbB pathway in agrin- induced AChR expression. Furthermore, salt extracts from the surface of cultured myotubes induce tyrosine phosphorylation of ErbB2 receptors, indicating that muscle cells express biological NRG-like activity on their surface. We further demonstrate by RT-PCR analysis that muscle NRGs have Ig-like domains required for their immobilization at heparan sulfate proteoglycans (HSPGs) of the extracellular matrix. In extrasynaptic regions of innervated muscle fibers in vivo, ectopically expressed neural agrin induces the colocalized accumulation of AChRs, muscle-derived NRGs, and HSPGs. By using overlay and radioligand-binding assays we show that the Ig domain of NRGs bind to the HSPGs agrin and perlecan. These findings show that neural agrin can induce AChR subunit gene transcription by aggregating muscle HSPGs on the muscle fiber surface that then serve as a local sink for focal binding of muscle-derived NRGs to regulate AChR gene expression at the neuromuscular junction.

ABSTRACT The retinoblastoma binding protein 1 (RBP1) appears to be an important factor in the repression of E2F-dependent transcription by the retinoblastoma protein (pRB) family. The recent identification of the breast carcinoma associated antigen (BCAA) as an RBP1-like protein led us to investigate its biological properties and compare them to RBP1. Like RBP1, BCAA contains a carboxy-terminal R2 domain that elicits histone deacetylase (HDAC)-dependent transcriptional repression via interactions with the SAP30 subunit of the Sin3/HDAC complex. Each RBP1 family member also contains two HDAC-independent repression activities within a region termed R1, which can be subdivided into a SUMOylated moiety (R1σ) and a predicted α-helical region (R1α). R1α is embedded within the ARID region and represses basal transcription only, whereas R1σ represses both basal and activated transcription and depends on SUMOylation. Overexpression of either RBP1 or BCAA, but not the truncated BCAAMCF-7 isoform that is overexpressed in breast cancer cells, caused a profound inhibition of cell proliferation and induced expression of a senescence marker. In each case the presence of both R1 and R2 was necessary for suppression of cell growth, suggesting that both R1 and R2 transcriptional repression activities play a role in RBP1 family protein-mediated regulation of cellular proliferation.

Expression of the cellular prion protein PrPC is sine qua none for the development of transmissible spongiform encephalopathy and thus for the accumulation of the illness-associated conformer PrPSc. Therefore, the tissue distribution of PrPC at the protein level in both quantitative and qualitative terms was investigated. PrPC was quantified using a two-site enzyme immunometric assay which was calibrated with purified ovine recombinant prion protein (rPrP). The most PrPC-rich tissue was the brain, followed by the lungs, skeletal muscle, heart, uterus, thymus and tongue, which contained between 20- and 50-fold less PrPC than the brain. The PrPC content of these tissues seems to be comparable between sheep. Other organs, however, showed different, but low, levels of the protein depending on the animal examined. This was also the case for tissues from the gastrointestinal tract. The tissue containing the lowest concentration of PrPC was shown to be the liver, where PrPC was found to be between 564- and 16000-fold less abundant than in the brain. PrPC was concentrated from crude cellular extracts by immunoprecipitation using several monoclonal and polyclonal anti-ovine PrP antibodies. Interestingly, it was observed that the isoform profile of PrPC was tissue-specific. The most atypical electrophoretic profile of PrPC was found in the skeletal muscle, where two polypeptides of 32 and 35 kDa were detected.

ABSTRACT The highly conserved 14-3-3 proteins participate in many biological processes in different eukaryotes. The BMH1 and BMH2 genes encode the two functionally redundant Saccharomyces cerevisiae 14-3-3 isoforms. In this work we provide evidence that defective 14-3-3 functions not only impair the ability of yeast cells to sustain DNA replication in the presence of sublethal concentrations of methyl methanesulfonate (MMS) or hydroxyurea (HU) but also cause S-phase checkpoint hyperactivation. Inactivation of the catalytic subunit of the histone acetyltransferase NuA4 or of its interactor Yng2, besides leading to S-phase defects and persistent checkpoint activation in the presence of genotoxic agents, is lethal for bmh mutants. Conversely, the lack of the histone deacetylase subunit Rpd3 or Sin3 partially suppresses the hypersensitivity to HU of bmh mutants and restores their ability to complete DNA replication in the presence of MMS or HU. These data strongly suggest that reduced acetyltransferase functionality might account for the S-phase defects of bmh mutants in the presence of genotoxic agents. Consistent with a role of 14-3-3 proteins in acetyltransferase and deacetylase regulation, we find that acetylation of H3 and H4 histone tails is reduced in temperature-sensitive bmh mutants shifted to the restrictive temperature. Moreover, Bmh proteins physically interact, directly or indirectly, with the Esa1 acetyltransferase throughout the cell cycle and with the Rpd3 deacetylase specifically during unperturbed S phase and after HU treatment. Taken together, our results highlight a novel role for 14-3-3 proteins in the regulation of histone acetyltransferase and deacetylase functions in the response to replicative stress.

Although it has been recently shown that nitric oxide (NO) and its congeners (NO(x)), including nitrosothiols, may modify catecholamine turnover in the brain, it is not known whether NO(x) affect norepinephrine (NE) uptake by sympathetic neurons. The nitrosothiol NO donor S-nitroso-acetylpenicillamine (SNAP, 100 microM for 1 h) elicited a concentration-dependent reduction in desipramine-sensitive [3H]NE uptake into PC-12 cells (66 +/- 3%; P < 0.01) or cultured rat superior cervical ganglia (74 +/- 5%; P < 0.001), whereas desipramine-insensitive [3H]NE uptake was unaffected, indicating a selective effect on uptake-1-mediated transport. Short-term coculture of PC-12 cells with microvascular endothelial cells expressing the cytokine-inducible NO synthase (NOS2) also exhibited a reduction in [3H]NE uptake (33 +/- 3%, P < 0.001) that could be prevented by the addition of the NOS inhibitor N-monomethyl-L-arginine (L-NMMA, 1 mM). Endogenous production of NO(x) by nerve growth factor-pretreated PC-12 cells also exhibited an L-NMMA-inhibitable reduction in [3H]NE uptake. Whereas SNAP resulted in a 10-fold elevation of PC-12 guanosine 3',5'-cyclic monophosphate (cGMP) content (P < 0.01), its effect on [3H]NE uptake was not mimicked by exposure to 8-bromo-cGMP. However, the inhibitory effect of SNAP on uptake-1-mediated [3H]NE transport could be attenuated by 1 mM cysteine, a sulfhydryl compound that could act as a sink for NO(x)-mediated nitrosation reactions, although cysteine did not affect the increase in intracellular cGMP with SNAP. These data suggest that an endogenous NO(x) source(s) modifies the activity of the uptake-1 catecholamine transporter in postganglionic sympathetic neurons, which, as we demonstrate, express both NOS1 and NOS3 isoforms, possibly by S-nitrosothiol-mediated nitrosation of regulatory sites on the transporter.

We have previously shown, using the Caco-2 clone PF11, that glucose represses transcription of the human sucrase-isomaltase (SI) gene and that the -370/+30 fragment of the SI gene conferred glucose-regulated expression on a heterologous gene. Different fragments beginning at the already characterized SI footprint (SIF) 1 (-53/-37), SIFR (-153/-129) or SIF3 (-176/-156) elements [Wu, Chen, Forslund and Traber (1994) J. Biol. Chem. 269, 17080–17085] were tested, in comparison with the -370/+30 fragment, for their capacity to inhibit reporter gene expression under high-glucose (25 mM) conditions. Unlike SIF1 and SIFR, the addition of the HNF (hepatocyte nuclear factor)-1-binding element SIF3 to the promoter fragment was required for repression under high-glucose conditions. This effect was enhanced when the SI promoter was extended to position -370, indicating that the -370/-176 region contains elements that may co-operate with SIF3 to increase the metabolic control of the SI promoter. We have characterized an additional HNF-1-binding site near to and upstream from SIF3; SIF4. By mutagenesis of the three HNF-1-binding elements we show that the two distal HNF-1-recognition sites are the most important for the glucose regulation of the SI gene. Moreover, this glucose regulation was abolished in PF11 cells overexpressing vHNF-1C (variant HNF, an isoform of the HNF-1 family). We thus propose that the differential binding of HNF-1-family proteins to their DNA targets on the SI promoter constitutes the molecular mechanism that controls the glucose regulation of the SI gene transcription.

Intrauterine growth restriction (IUGR) leads to obesity, glucose intolerance, and type 2 diabetes mellitus in the adult. To determine the mechanism(s) behind this “metabolic imprinting” phenomenon, we examined the effect of total calorie restriction during mid- to late gestation modified by postnatal ad libitum access to nutrients (CM/SP) or nutrient restriction (SM/SP) vs. postnatal nutrient restriction alone (SM/CP) on skeletal muscle and white adipose tissue (WAT) insulin-responsive glucose transporter isoform (GLUT4) expression and insulin-responsive translocation. A decline in skeletal muscle GLUT4 expression and protein concentrations was noted only in the SM/SP and SM/CP groups. In contrast, WAT demonstrated no change in GLUT4 expression and protein concentrations in all experimental groups. The altered in utero hormonal/metabolic milieu was associated with a compensatory adaptation that persisted in the adult and consisted of an increase in the skeletal muscle basal plasma membrane-associated GLUT4 concentrations. This perturbation led to no further exogenous insulin-induced GLUT4 translocation, thereby disabling the insulin responsiveness of the skeletal muscle but retaining it in WAT. These changes, which present at birth, collectively maximize basal glucose transport to the compromised skeletal muscle with a relative resistance to exogenous/postprandial insulin. Preservation of insulin responsiveness in WAT may serve as a sink that absorbs postprandial nutrients that can no longer efficiently access skeletal muscle. We speculate that, in utero, GLUT4 aberrations may predict type 2 diabetes mellitus, whereas postnatal nutrient intake may predict obesity, thereby explaining the heterogeneous phenotype of the IUGR adult offspring.

Abstract B-cell precursor acute lymphoblastic leukemia (BCP-ALL) is accompanied by genomic mutations and rearrangements that commonly affect cytokines, transcription factors or signalling molecules that drive B-cell development or contribute to the pre-B cell receptor (pre-BCR) checkpoint. Deletions of the long arm of chromosome 6 [del(6q)] occur in ~10% of BCP-ALL and are also frequent in mature B and T-cell malignancies. Loss of function of the 6q genes EPHA7 and PRDM1, have been implicated in the genesis of lymphoma and BACH2, as a mediator of pre-BCR negative selection, is functionally a candidate tumour suppressor gene. However loss of these or other 6q genes have not been demonstrated, for example through biallelic inactivation, to contribute to BCP-ALL. Analysis of our own and published SNP6.0 data from ALL patients defined 5 focal recurrent regions of deletion on 6q, 4 mapping to 6q15-6q21, coincident with previously published common regions of deletion in ALL. These 4 regions contain 22 candidate genes, including EPHA7 but not BACH2 or PRDM1, which nevertheless mapped close to focal deletions and were also classed as candidate tumour suppressors. To develop the clone tracking assay, we adapted the SIN-SIEW lentiviral construct that expresses EGFP under the control of a spleen focus forming virus (SFFV) promoter. Candidate gene consensus coding sequence (CCDS) or a control luciferase cDNA were cloned between the promoter and an internal ribosomal entry site immediately upstream of EGFP. Transduction of the control (pSLIEW) or candidate gene SIN-SIEW-CCDS constructs consistently expressed EGFP in 697, a BCP-ALL cell line with del(6)(q14.1-22.3). For clone tracking, SIN-SIEW-CCDS constructs were assigned to 4 pools that also included pSLIEW. Pools were transduced into 697 cells that were both cultured in vitro and transplanted by intra-femoral injection into NOD/LtSz-scid IL2Rƴ null (NSG) mice. DNA was isolated from transduced cells immediately before transplant and then at 3 to 5 day intervals from cultured cells or from cells recovered from mouse bone marrow, spleen or liver at end stage disease. The pSLIEW construct facilitated monitoring of disease progression by in vivo imaging and also served as a control to measure CCDS construct copy number changes against. To quantify changes in integrated SIN-SIEW-CCDS, we developed a multiplex targeted Illumina sequencing approach. In vitro, highly significant (p<0.01) reductions in copy number relative to pSLIEW over time, occurred for constructs expressing FOXO3, POU3F2, SIM1, PRDM13, C6orf168 and both α and β isoforms of PRDM1 (Fig 1a). With the exception of C6orf168, these genes also strongly suppressed leukemia development in vivo in all tissues analysed (Fig 1b). The known tumour suppressor genes, BACH2 and EPHA7, had no effect on cell growth in vitro. In vivo a moderate reduction for one of two EPHA7 CCDS was observed though curiously cells expressing BACH2 increased in relative copy number by approximately 3 fold. RNA sequencing data from 697 and published array data for normal pre-B cells and cases of BCP-ALL showed no, or extremely low, levels of expression for POU3F2, SIM1, PRDM13 and C6orf168 making it unlikely that they function as tumour suppressor genes in BCP-ALL. However significant expression of the transcription factors FOXO3 and PRDM1 were seen across data sets. Western blot confirmed expression of FOXO3 and PRDM1 in 697 and other BCP-ALL cell lines and demonstrated substantial increases in the corresponding proteins after transduction of 697 with FOXO3 and PRDM1 SIN-SIEW CCDS constructs. Over-expression of FOXO3 and both isoforms of PRDM1 decreased the proportion of cells in S and G2 phases of the cell cycle, but failed to induce apoptosis as measured by Annexin-5 staining. Comparison of total mRNA sequencing profiles of 697 cells, FACS sorted for ectopic expression of FOXO3, PRDM1 or control construct, showed distinctive patterns of up or down regulated mRNA. The roles of FOXO3 and PRDM1 in early B-cell development are currently undefined but notably our data suggests they influence expression of components of the pre-BCR and related signalling pathways and therefore may contribute to the pre-BCR checkpoint. Disclosures No relevant conflicts of interest to declare.

Objective: Air pollution is one of the most severe environmental problems of developing cities which adversely affects both plant and human life. However, roadside plants in the urban locations help in reducing the pollution level from the air through foliar surface and act as pollution sink. In this work, an attempt was made to understand the impact of air pollution on urban roadside plants which act as bio indicator.Methods: A study was conducted to check the impact of urbanization on air pollution by analyzing anatomical and biochemical aspects of Thevetia peruviana L. For anatomical analysis, the transverse sections of leaves were observed under a microscope; whereas for biochemical analysis, the estimation of chlorophyll, carotenoid and protein were determined by spectrophotometric methods. On the other hand, antioxidant enzyme assays, as well as specific activity staining, were performed to study the antioxidant potential. To investigate the antioxidant activity of the leaf extracts, an assay for catalase (CAT), guaiacol peroxidase (GPX) and superoxide dismutase (SOD) were performed. Isoforms of CAT, GPX and SOD were separated using native polyacrylamide gel electrophoresis (PAGE) and their activities were analyzed.Results: Analysis of data revealed that the anatomical disturbances significantly occurred in exposed plants of various sites. Among biochemical parameters, photosynthetic pigments such as chlorophyll a, chlorophyll b, total chlorophyll and carotenoid content were found to be decreased. A maximum (7.65±0.51, 3.78±0.56,11.43±0.91, 5.63±0.55 mg/g, respectively) decrement was noticed in leaves of the Pokhariput plant in comparison to Khorda NH5 (19.44±1.08, 10.12±1.03, 29.56±2.32, 10.22±1.21 mg/g, respectively) which is taken as control one. To determine the effect of air pollution on proteins, leaf extracts were analyzed by the Lowry method and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The substantial decrement of total protein and alteration in polypeptides were noticed in polluted sites. Meanwhile, the enhancement of antioxidant enzyme activities such as CAT, GPX and SOD were also detected.Conclusion: The increment of antioxidant enzymes and alteration of proteins, suggesting the activation of defensive mechanisms in selected plants under air pollution stress and also the plants made physiological and biochemical adjustments to overcome the oxidative damage.

Abstract Mantle cell lymphoma (MCL), which overexpresses cyclin-D1 through an alteration in the t(11;14)(q13;q32) chromosomal region, is associated with brief disease-free and overall survival durations characteristic of aggressive B-cell lymphomas. Bruton tyrosine kinase (BTK) has been identified as a key component of the B-cell antigen receptor (BCR) signaling pathway and is implicated in the pathogenesis of certain B-cell malignancies. Phase III clinical trials of BKT inhibitor ibrutinib in MCL patients have demonstrated clinical responses characterized by mobilization of tissue-resident MCL cells into the peripheral blood. However, since the time to maximum response with ibrutinib is relatively long and patients may become resistant to BTK inhibition, combination regimens that accelerate time to remission and increase depth of remission are of considerable interest. We hypothesized that combinations of ibrutinib with proapoptotic drugs that function independently of BCR signaling could yield synergistic anti-lymphoma interactions. Thus we investigated the antitumor effects and molecular mechanisms of simultaneous treatment with ibrutinib and selexinor, an oral selective inhibitor of nuclear export (SINE)(KPT-330, Karyopharm), or ABT-199, a selective Bcl-2 inhibitor. SINE agents exhibit antiproliferative and proapoptotic activities against MCL cells via inhibition of nuclear export of tumor suppresor proteins, transcription factors and oncogenic mRNAs and repression of ribosomal biogenesis (Tabe et al. ASH 2013). Selinexor showed promising anti tumor activity in agrresive lymphoma as part of ongoing Phase 1 study (ASCO 2014). ABT-199 has promising proapoptotic activity in relapsed/refractory CLL and NHL without inducing thrombocytopenia. In this study, we utilized four MCL cell lines: MINO, Z138, Jeko-1, and JVM2. Inhibition of BTK activity by ibrutinib resulted in reduction of cell proliferation in a dose-dependent manner with G0/G1 cell cycle arrest but no apoptosis induction (IC50 at 48 hrs by MTT: 5.4 mM for MINO, 3.5 mM for Z138, 0.5 mM for Jeko-1, 3.1 mM for JVM2). Western blot analysis demonstrated ibrutinib-induced downregulation of phospho-(p-)BTK, p-Akt, mTORC1 substrates p-S6K and p-4EBP1, and cyclin D1 expression. Single-agent selinexor induced cell growth inhibition with G0/G1 cell cycle arrest in a dose-dependent manner (IC50 ranging from 10 nM to 130 nM). The ibrutinib/selinexor combination resulted in further decrease of p-4EBP1 and cyclin D1 expression and downregulation of p-Rb, c-Myc, and Mcl-1, which translated into synergistic reduction of cell proliferation in three of the four tested cell lines (combination index [CI]: 0.4 for MINO, 0.2 for Jeko-1, 0.2 for JVM2). ABT-199 inhibited cell proliferation with apoptosis induction in MINO and Z138 cells (IC50: 1.5 nM for MINO, 17.5 nM for Z138), which synergistically enhanced the antiproliferative effects of ibrutinib (CI: 0.6 for MINO, 0.8 for Z138) with striking reductions of p-4EBP1, cyclin D1, p-Rb, and c-Myc expression along with induction of Bax and cleaved caspase-3. To investigate the molecular modifications of the cellular pathway network in response to BTK blockade by ibrutinib alone or in combination with selinexor or ABT-199, we employed the proteomic technology of isobaric tags for relative and absolute quantitation (iTRAQ). In MINO cells, iTRAQ identified 1,401 unique proteins. Ibrutinib induced downregulation of isoform BTK (p=0.02) and the cell cycle initiation of mitosis pathway (p=0.003) with decreases of ribosomal proteins and elongation factors. Combination with selinexor upregulated the apoptosis and oxidative stress–associated pathways with increases of cytochrome c, voltage-dependent anion channels, HSP10, and histone H1, all of which function as dynamic initiators of mitochondria-mediated apoptosis (p < 0.05). ABT-199 by itself induced upregulation of the apoptosis and oxidative stress–associated pathways (p < 0.001), and these effects were significantly enhanced by combination with ibrutinib. Taken together, our findings suggest that treatment with combinations of ibrutinib and selinexor or ABT-199 exerts synergistic antiproliferative effects through inhibition of mTOR signaling, downregulation of ribosomal biosynthesis, and induction of mitochondria-mediated apoptosis. These combinations warrant further evaluation in clinical trials in MCL patients. Disclosures Andreeff: Karyopharm: Research Funding.

Introducción: La enfermedad renal crónica asociada a la obesidad (ERC-AO) es una enfermedad con aumento en la prevalencia en las últimas décadas. Se caracteriza por un exceso de desequilibrios hormonales adipocíticos (adipoquinas), desregulación del sistema de equilibrio energético y desequilibrios en la homeostasis metabólica. Propósito de la revisión: El objetivo de la revisión es delinear el papel de los diferentes mecanismos fisiopatológicos para el desarrollo de enfermedad renal funcional o anatómica en pacientes con obesidad. Buscamos reportes actualizados en donde se incluye los resultados de mejor supervivencia para los pacientes con ERC-AO. Recientes hallazgos: Actualmente sabemos la ERC-AO tiene un comportamiento pro inflamatorio crónico. La obesidad y sobrepeso se asocian alteraciones hemodinámicas, estructurales e histopatológicas en el riñón, así como alteraciones metabólicas y bioquímicas que predisponen a la enfermedad renal, aun cuando la función renal y las pruebas convencionales sean normales. Conclusiones: Clasificamos a la ERC-AO en Tipo 1: Obesidad y alteraciones funcionales potencialmente reversibles. Tipo 2: Obesidad y alteraciones estructurales histopatológicas potencialmente no reversibles (Incluye la Glomerulopatía asociada a obesidad y glomeruloesclerosis focal y segmentaria). Tipo 3: Obesidad en relacionada con enfermedades crónicas (Diabetes, Hipertensión, Hipertensión pulmonar. Insuficiencia Cardíaca). Tipo 4: Obesidad en el paciente con terapia sustitutiva de la función renal. Recibido: Agosto 03, 2022 Aceptado: Septiembre 30, 2022 Publicado: Septiembre 30, 2022 Editor: Dr. Franklin Mora Bravo. Introducción La obesidad es una enfermedad en crecimiento con un aumento en su prevalencia en las últimas décadas, asociándose a un elevada carga asistencial y económica para los sistemas sanitaros derivado de su relación con enfermedades cardiovasculares, endocrinas, psicológicas, renales entre otras [1, 2]. El incremento en las tasas de obesidad en distintos grupos etarios, desde niños hasta adultos jóvenes conlleva a asumir que en el futuro veremos más enfermedad renal relacionada con la obesidad (ERC-AO) en la población general, con implicaciones relevantes para los sistemas de atención [3]. Por ello el conocimiento y comprensión de esta interacción podría tener implicaciones en la prevención y tratamiento de las enfermedades renales. Dentro de la población general la obesidad se asocia a incremento en el riesgo de diversas condiciones patológicas, como la hipertensión arterial crónica (HTA), enfermedad renal crónica (ERC), artrosis, infecciones, síndrome de apnea hipopnea obstructiva del sueño (SAHOS) y diabetes mellitus (DM) entre otras [3]. No obstante, en el escenario de la ERC, la obesidad juega un rol dual y paralelo en el desarrollo de la enfermedad, tradicionalmente se ha denominado “paradoja de la obesidad”, donde por un lado actúa como un factor de riesgo modificable para el desarrollo de la enfermedad renal crónica (ERC) y por otro se ha asocia de manera consistente con mejores resultados de supervivencia en pacientes con enfermedad renal terminal [1]. Por lo anterior, en las próximas páginas describimos aspectos fisiopatológicos que involucran la obesidad en el desarrollo de la ERC. Definición y epidemiología La obesidad es una condición que se caracteriza por la acumulación anormal o excesiva de tejido adiposo con consecuencias patológicas adversas e incremento del riesgo cardiovascular [4]. Utilizando para su definición y diagnostico un indicador simple como es la relación entre el peso y la talla denominado índice de masa corporal (IMC), se calcula dividiendo el peso de una persona en kilos por el cuadrado de su talla en metros (kg/m2). Un IMC entre 18.5 y 25 kg/m2 es considerado por la Organización Mundial de la Salud (OMS) como peso normal, un IMC entre 25 y 30 kg/m2 como sobrepeso y un IMC > 30 kg/m2, como obesidad [5-7]. Además, la obesidad puede ser clasificada en tres niveles de severidad: clase I (IMC 30.0 – 34.9), clase II (IMC 35.0 – 39.9) y clase III (IMC > 40) [8]. Durante las últimas tres décadas, la prevalencia de adultos con sobrepeso y obesidad (IMC ≥ 25 kg/m2) en todo el mundo ha aumentado sustancialmente, convirtiendo a la obesidad en una epidemia y se prevé que su prevalencia crezca un 40% en la próxima década [6]. Actualmente, el problema de obesidad se ha visto en mayor aumento debido al incremento en la afectación en niños, lo que ocasiona una mayor prevalencia de patologías a edad temprana. En 2016, según las estimaciones de la OMS unos 41 millones de niños menores de cinco años tenían sobrepeso o eran obesos [7]. Esto afectando a todos los países, independiente de su nivel de ingresos [7]. La prevalencia del sobrepeso y la obesidad en niños y adolescentes (de 5 a 19 años) ha aumentado de forma espectacular, del 4% en 1975 a más del 18% en 2016. Este aumento ha sido similar en ambos sexos: un 18% de niñas y un 19% de niños con sobrepeso en 2016. Mientras que en 1975 había menos de un 1% de niños y adolescentes de 5 a 19 años con obesidad, en 2016 eran 124 millones (un 6% de las niñas y un 8% de los niños) [7]. La creciente prevalencia de la obesidad tiene implicaciones para las enfermedades cardiovasculares (ECV) y también para la ERC. Un IMC alto es uno de los factores de riesgo más fuertes para la ERC de nueva aparición [6]. Epidemiología de la enfermedad renal crónica asociada a obesidad (ERC-AO) La enfermedad renal crónica (ERC) es una condición de interés en salud pública, asociada a una elevada morbilidad y mortalidad a nivel mundial. Las guías KDIGO (Kidney Disease: Improving Global Outcomes), definen la ERC como la presencia de alteraciones en la estructura o función renal durante al menos tres meses y con implicaciones para la salud [9, 10]. Los principales elementos clasificatorios para definir la presencia de ERC son la tasa de filtración glomerular (TFG) estimada (G1 a G5) utilizando como umbral definitorio una TFG 60 ml/min/1,73m2 y la tasa de excreción de albúmina en orina (A1 a A3) según el cociente albúmina/creatinina en una muestra aislada de orina sea < 30, 30-300 o > 300 mg/g, respectivamente [9, 10]. Si bien inicialmente existía cierta controversia sobre el uso de la TFG para el diagnóstico de la ERC en fases iniciales, trabajos recientes han puesto en evidencia que tanto una TFG< 60 ml/min/1.73 m2 como un cociente albúmina/creatinina (CAC) ≥ 1.1 mg/mmol (10 mg/g) son predictores independientes del riesgo de mortalidad e insuficiencia renal terminal (IRT) en población general [11, 12]. En consecuencia, debido a estas categorías podemos determinar el pronóstico de cada paciente. Los datos globales sugieren que la prevalencia de la ERC se encuentra entre el 10 y el 16 %, pero la información sobre la prevalencia de la población por categoría de TFG y ACR es escasa [13]. La ERC es una afección asociada a una elevada carga de morbilidad, mortalidad y enfermedad cardiovascular (ECV). A medida que disminuye la función renal, surgen trastornos metabólicos y hemodinámicos que aumentan las tasas de hospitalización, ECV y muerte [4]. El conjunto de factores de riesgo conocidos para la progresión de la ERC es relativamente pequeño, y las terapias y estrategias efectivas para retrasar la progresión de la ERC son limitadas [14]. Por lo cual resulta necesario conocer y entender los diferentes factores de riesgo y su impacto en el daño renal, en aras de lograr minimizar la progresión del mismo, sobre todo en aquellos en los cuales se puede realizar intervenciones activas, evaluables, controlables y con seguimiento continuo como es la obesidad. A la fecha existe suficiente evidencia para asociar la obesidad con el desarrollo y progresión de la enfermedad renal crónica. Los datos granulares sobre la prevalencia de la obesidad en personas con ERC son limitados pero consistentes en todo el espectro de la enfermedad renal. En la Encuesta Nacional de Examen de Salud y Nutrición de 2011–2014, el 44.1 % de los pacientes con ERC en los Estados Unidos también tenían obesidad (21.9 % con obesidad de clase 1 y 11.1 % con clase 2 y obesidad clase 3, habiéndose incrementado el porcentaje global un 5% en los últimos 12 años [15]. La glomeruloesclerosis focal y segmentaria (GEFS) es el tipo de glomerulonefritis que se asocia con mayor frecuencia a la obesidad [16]. La enfermedad glomerular habitualmente asociada a la obesidad se denomina glomerulopatía relacionada con la obesidad (GRO). Esta condición suele presentarse con síndrome nefrótico y pérdida progresiva de la función renal. Con la epidemia mundial de obesidad, se produjo un aumento progresivo de la GRO del 0.2% entre 1986 y 1990 al 2% entre 1996 y 2000, y se ha convertido en un tema emergente en el ámbito de la nefrología [15]. Etiología y patogénesis de la ERC-AO La obesidad se caracteriza por un exceso de desequilibrios hormonales adipocíticos (adipoquinas), desregulación del sistema de equilibrio energético y desequilibrios en la homeostasis metabólica [12]. Hay dos tipos de tejido adiposo presentes en los humanos: tejido adiposo blanco (WAT) y tejido adiposo marrón (BAT) [17-19]. El depósito de grasa ectópica primariamente ocurre en lugares donde no se almacena fisiológicamente, como el hígado, el páncreas, el corazón y el músculo esquelético; secundariamente hay un cambio en la distribución del tejido adiposo visceral con almacenamiento de tejido adiposo en los espacios intraperitoneal y retroperitoneal; luego se presenta la desregulación inflamatoria y de adipoquinas; y por último la resistencia a la insulina [20]. Tejido adiposo blanco (WAT) El tejido adiposo blanco (WAT) se caracteriza por ser un tejido blanco o amarillo con menor vascularización e inervación que el tejido marrón. Las células grasas tienen un tamaño que oscila entre 20 y 200 µm y contienen una única vacuola lipídica (uniloculares). En dicha vacuola se almacenan lípidos para su uso cuando hay demanda energética. De la totalidad de los lípidos que abarca la vacuola lipídica del adipocito blanco, del 90 al 99% son triacilgliceroles. El tejido adiposo blanco genera una gran cantidad de adipocinas y lipocinas. Las adipocinas son péptidos que actúan como hormonas o mensajeros que regulan el metabolismo. El tejido adiposo blanco se localiza en el tejido omental, mesentérico, retroperitoneal, perirrenal, gonadal y pericárdico [19]. Este tejido al igual que el tejido adiposo de otros sitios, está compuesto por una variedad de células que incluyen macrófagos, neutrófilos, células T CD4 y CD8, células B, neutrófilos, mastocitos, células T reguladoras y células T asesinas naturales (NK) [21, 22]. El tejido adiposo es responsable de la secreción de muchas moléculas de señalización, incluidas adipocinas, hormonas, citocinas y factores de crecimiento, como leptina, adiponectina, resistina, factor de necrosis tumoral-α (TNF-α), interleucina 6 (IL-6), monocito, proteína quimioatrayente-1 (MCP-1), factor de crecimiento transformante-β (TGF-β) y angiotensina II [23]. Tejido adiposo marrón o pardo (BAT) La coloración marrón del tejido adiposo se debe a que está más vascularizado y tiene un alto contenido de mitocondrias, las células grasas que componen el tejido adiposo pardo son multiloculares o tienen varias vacuolas lipídicas. Estas células tienen forma poligonal y miden de 15 a 50 µm. A diferencia del tejido adiposo blanco, el tejido marrón no tiene la función de almacenar energía, sino que la disipa a través de la termogénesis. Para lograr la regulación de la temperatura corporal, el tejido adiposo pardo se localiza en sitios superficiales y profundos [18]. Clasificación de la ERC-AO Se ha establecido que la obesidad es una enfermedad con un comportamiento pro inflamatorio crónico con múltiples comorbilidades asociadas [19]. El tejido adiposo como se describió previamente funciona como un órgano con actividad endocrina y esta infiltrado por diferentes poblaciones celulares que incluyen macrófagos y otras células con actividad inmune como linfocitos T, B y células dendríticas [19]. La mayor parte de la grasa corporal total, se considera como un sistema de órganos endocrinos, la perturbación de este tejido tiene como resultado una respuesta patológica al balance calórico positivo en individuos susceptibles que directa e indirectamente contribuye a la enfermedad cardiovascular y metabólica, se tiene conocimiento de tres principales mecanismos de disfunción del tejido adiposo “adiposopatía” [20]. Estos mecanismos incluyen alteraciones hemodinámicas, metabólicas e inflamatorias, lo que es la base de la clasificación de la ERC-AO propuesta en esta revisión (Tabla 1). ERC-AO tipo 1 La obesidad produce un daño renal de forma directa a través de alteraciones hemodinámicas, inflamatorias, y desregulación de factores de crecimiento y adipocitoquinas, además de aumento de leptina y disminución de adiponectina, aun cuando la función renal y las pruebas convencionales sean normales [16]. La obesidad desencadena una serie de eventos, que incluyen resistencia a la insulina, intolerancia a la glucosa, hiperlipidemia, aterosclerosis e hipertensión, todos los cuales están asociados con un mayor riesgo cardiovascular [4, 16] (Figura 1). La obesidad conduce a un incremento en la reabsorción tubular de sodio, alterando la natriuresis y provocando una expansión de volumen extracelular debido a la activación del sistema nervioso simpático (SNS) y el sistema renina-angiotensina-aldosterona (SRAA)(16). El aumento en la reabsorción tubular de sodio y la consiguiente expansión de volumen extracelular es un evento central en el desarrollo de HTA en la obesidad [4, 16]. Algunos estudios sugieren que se produce un aumento de la reabsorción de sodio en algunos segmentos además del túbulo proximal, posiblemente en el asa de Henle. Además, hay un aumento del flujo sanguíneo renal, la tasa de filtración glomerular (TFG) y la fracción de filtración [16]. La hiperfiltración glomerular, asociada con el aumento de la presión arterial y otras alteraciones metabólicas como la resistencia a la insulina y la DM, finalmente resultan en daño renal y disminución del filtrado glomerular [16]. Por otro lado, la activación del SNS también contribuye a la hipertensión relacionada con la obesidad [4]. Hay evidencia de que la denervación renal reduce la retención de sodio y la hipertensión en la obesidad, lo que sugiere que la activación del SNS inducida por la obesidad aumenta la presión arterial principalmente debido al estímulo de retención de sodio, más que a la vasoconstricción [16]. Los mecanismos que conducen a la activación del SNS en la obesidad aún no se conocen por completo, pero se han propuesto varios factores como desencadenantes de este estímulo, entre ellos la hiperinsulinemia, la hiperleptinemia, el aumento de los niveles de ácidos grasos, los niveles de angiotensina II y las alteraciones del reflejo barorreceptor. El aumento de los niveles de leptina está asociado a la activación del SNS y su efecto sobre el aumento de los niveles de presión arterial incluye también la inhibición de la síntesis de óxido nítrico (potente vasodilatador) [16, 24, 25].También se ha descrito un aumento de la producción de endotelina-1 en sujetos obesos, lo que contribuye aún más a la elevación de los niveles de presión arterial y, en consecuencia, a la disfunción renal. Estudios recientes han demostrado que la endotelina-1 está aumentada en pacientes con hipertensión intradiálisis, lo que sugiere que esta sustancia juega un papel clave en la génesis de la hipertensión en pacientes con ERC y posiblemente esté asociada con la hipertensión en pacientes obesos [16, 25]. Por lo anterior, las alteraciones hemodinámicas en los pacientes con obesidad conllevan a progresión de la ERC e incremento del riesgo cardiovascular derivado del desarrollo de enfermedades adicionales como la HTA, potencialmente estos cambios son reversibles con el control de la obesidad. ERC-AO Tipo 2 Mantener el estado de obesidad más allá de los efectos renales funcionales produce cambios estructurales irreversibles a nivel glomerular [25]. El estudio de pacientes con ERC y obesidad ha permitido identificar la presencia de enfermedad glomerular asociada a la obesidad, denominada glomerulopatía relacionada con la obesidad (GRO). En esta condición la hipertrofia glomerular parece ser la lesión inicial que estimula el borramiento de los podocitos y desencadena la respuesta inflamatoria local [25, 26]. Es relevante mencionar que las señales profibrogénicas inducen la formación de depósitos en la matriz extracelular de las nefronas, que conduce al engrosamiento de la membrana basal glomeruloesclerosis y fibrosis tubulointersticial [26]. Dentro del curso patogénico de la enfermedad la expansión de la superficie glomerular conduce a que los podocitos sean incapaces de cubrirla, esto lleva a disfunción y borramiento de los mismos, generando ruptura de la barrera de filtración glomerular con sobrecarga de las células restantes, lo que finalmente conduce a hiperfiltración y proteinuria [25, 26]. No obstante, no todos los pacientes con obesidad o IMC aumentado desarrollan ERC, lo cual sugiere que el incremento del IMC por sí solo no genera aumento en la incidencia o progresión de la ERC, ameritando alteraciones metabólicas adicionales. En los siguientes apartados se describen algunas de estas vías fisiopatológicas comunes a todos los tipos de ERC-AO. ERC-AO Tipo 3 La obesidad produce daño renal de forma secundaria ya que aumenta el riesgo de diabetes mellitus, hipertensión y daño cardiovascular, estas patologías causan enfermedad renal diabética (ERD), nefroangioesclerosis, y glomerulopatía asociada a hipertensión pulmonar e insuficiencia cardíaca. La mortalidad no solo se ve afectada por la presencia de la obesidad sino por la presencia de diabetes tipo 2, hipertensión arterial, hipertensión pulmonar e insuficiencia cardíaca. Los peores resultados en supervivencia lo padecen los pacientes con falla cardíaca, obesidad e insuficiencia renal. ERC-AO Tipo 4 En pacientes en hemodiálisis los niveles más elevados de adiponectina se asocian paradójicamente con tres veces más riesgo de muerte [24]. La obesidad se asocia a niveles muy bajos adiponectina por lo que la obesidad en el grupo poblacional que se realiza hemodiálisis es un fuerte factor protector con mejores resultados de supervivencia a 3 años comparados con pacientes con índice de masa corporal normal o baja. Mecanismos fisiopatológicos comunes en la ERC-AO Lipotoxicidad derivada del tejido adiposo En pacientes obesos el exceso de energía conduce a un microambiente sometido a estrés crónico, lo cual resulta en hipertrofia del tejido adiposo hasta que los adipocitos alcanzan su límite de crecimiento [25]. En ese momento, el exceso de especies toxicas lipídicas se acumula ectópicamente en diferentes órganos, induciendo un efecto nocivo conocido como lipotoxicidad; especialmente a nivel renal [27]. La lipotoxicidad se asocia a cambios estructurales y funcionales de las células mesangiales, podocitos y células tubulares proximales [28]. En los podocitos, esto interferiría con la vía de la insulina, crítica para la supervivencia y el mantenimiento de la estructura de los podocitos, lo que conduciría a la apoptosis de los podocitos e induciría una respuesta hipertrófica compensatoria en los podocitos restantes [25]. En el riñón, los depósitos de lípidos ectópicos contribuyen tanto a la inflamación local como al estrés oxidativo [27]. En modelos de ERD, la dislipidemia puede favorecer la acumulación de lípidos ectópicos e intermediarios lipídicos, no solo en el riñón sino también en tejidos extrarrenales como hígado, páncreas y corazón [27]. La acumulación de lípidos en el parénquima renal, genera daño en varias poblaciones celulares, incluídos podocitos, células epiteliales tubulares proximales y el tejido tubulointersticial a través de distintos mecanismos descritos en las siguientes apartados, pudiendo general compromiso a largo plazo de la función renal [27]. El tejido adiposo es una fuente importante de producción de diferentes factores proteicos activos, conocidos como adipocitocinas, las cuales participan en diferentes procesos metabólicos. Alteraciones en la secreción y señalización de moléculas derivadas del tejido adiposo durante la obesidad en gran medida puede mediar en la patogenia de los trastornos metabólicos [25]. A continuaciones se describe el rol de las adipocinas en la patogenia de la ERC y obesidad. Adiponectina La adiponectina es una proteína secretada principalmente por los adipocitos WAT, las principales funciones biológicas de la adiponectina incluyen una mayor biosíntesis de ácidos grasos y la inhibición de la gluconeogénesis hepática [17]. Es probablemente la adipocina secretada más abundantemente, forma alrededor del 0.05 % de las proteínas séricas y mide de 3 a 30 mg/ml en humanos, para su activación utiliza dos isoformas del receptor (AdipoR1 y AdipoR2) son receptores de siete transmembranas y tienen una homología del 66.7 % en su estructura [17]. Sin embargo, AdipoR1 y AdipoR2 son estructural y funcionalmente distintos de los receptores acoplados a proteína G porque su terminal N es intracelular, mientras que el terminal C es extracelular [29, 30]. La señalización de adiponectina se basa principalmente en interacciones de tipo receptor-ligando, en las que la adiponectina se une a sus receptores afines e inicia la activación de varias cascadas de señalización intracelular a través de las vías AMPK, mTOR, NF-κB, STAT3 y JNK [17]. La adiponectina inicia la activación de la señalización de AMPK mediada por la proteína adaptadora APPL1, que se une al dominio intracelular de AdipoR. Eso produce la activación de la biosíntesis de moléculas, otras proteínas reguladoras e importantes factores de transcripción. AMPK es un regulador que participa principalmente en la proliferación celular [17]. Hay dos tipos de macrófagos, M1 participan en la estimulación de los factores pro inflamatorios e induce la resistencia a la insulina y M2 bloquean una respuesta inflamatoria y promueve el metabolismo oxidativo; En los macrófagos, la adiponectina promueve la diferenciación celular de monocitos a macrófagos M2 y suprime su diferenciación a macrófagos M1, lo que muestra efectos pro inflamatorios y antiinflamatorios. Además, también activa los factores antiinflamatorios IL-10 pero reduce las citoquinas pro inflamatorias como IFN-γ, IL-6 y TNF-α en los macrófagos humanos [17]. Los pacientes con ERC muestran niveles elevados de proteína C reactiva (PCR), IL-6 y TNF-α y tienen una activación aberrante de receptor tipo toll (TLR)-4 [25]; en un estudio realizado en el año 2005 en 29 pacientes con ERC no diabéticos en etapa 5 y 14 controles sanos, se identificó que los pacientes con ERC tenían una expresión elevada del gen y la proteína TLR4, la estimulación de TLR-4 in vitro indujo la activación de TNF-α y NF-κB en células C2C12. Esto sugiere indirectamente que la activación de TLR-4 podría promover la inflamación muscular de los pacientes con ERC [31]. Los niveles de adiponectina se consideran predictivos de ERC, dado que estos se encuentran aumentados en pacientes con etapa pre diálisis [17, 29, 32]. Adicionalmente, en un estudio prospectivo realizado en el año 2008 en pacientes con ERC primaria no diabética identificó niveles elevados de adiponectina como un predictor novedoso de progresión de la ERC en hombres [33]. En estudios realizados en animales (ratones) muestran que la deficiencia de adiponectina se relaciona con varias alteraciones histológicas, incluida la fusión segmentaria procesos podocitarios, albuminuria y aumento del estrés oxidativo en los riñones [34]. Por otro lado, en pacientes obesos la producción de adiponectina se encuentra disminuida por lo que se cree que puede generar una función protectora sobre el riñón [29]. No obstante, paradójicamente, algunos estudios muestran que los pacientes con ERC y enfermedad renal crónica en diálisis (ERCT) tienen altos niveles de adipocinas, las explicaciones a esta situación son controversiales, se ha planteado podrían corresponder a un mecanismo compensatorio, otras consideraciones sugieren una disminución de la sensibilidad a la adiponectina o una reducción en el aclaramiento de la misma [35]. Leptina En pacientes con ERC independiente de la presencia de obesidad o no, se asocian a niveles elevados de leptina sérica. La leptina es una proteína de 167 aminoácidos, con una masa molecular de aproximadamente 16 kDa que está codificada por el gen LEP [23] secretada principalmente por los adipocitos, es una adipocina pleiotrópica. La leptina circulante llega a los órganos diana, donde se une a receptores específicos (conocidos como ObR, LR o LEPR), se conocen cinco isoformas del receptor de leptina en humanos (ObRa, ObRb, ObRc, ObRd y ObRe), de estas solo la isoforma ObRb (isoforma larga) se considera un receptor completamente activo, ya que es capaz de transducir completamente una señal de activación en la célula. Esta isoforma se encuentra altamente expresada en el sistema nervioso central (SNC), especialmente en el hipotálamo, donde participa en la regulación de la actividad secretora de este órgano. Los efectos de la leptina están mediados por cinco vías principales de señalización. Estas vías incluyen las vías de señalización JAK-STAT, PI3K, MAPK, AMPK y mTOR [23]. Por esta razón la principal función fisiológica de la leptina es transmitir información al hipotálamo sobre la cantidad de energía almacenada, como la masa de tejido adiposo, e influir en el gasto de energía al reducir el apetito. Regula el metabolismo energético, tiene efecto sobre la ingesta de alimentos, procesos de coagulación, angiogénesis, funciones relacionadas con la insulina y la remodelación vascular, además funciona como un pro inflamatorio molecular [36]. La leptina tiene efectos sobre el apetito y se ha demostrado que la hiperleptinemia contribuye a la hipertensión asociada a la obesidad por sobre activación del sistema nervioso simpático [37]. En cuanto al curso de la ERC, la leptina puede modular diferentes vías de señalización en el riñón, debido a que las células endoteliales glomerulares y mesangiales expresan abundantes receptores de leptina [25]. La leptina inducirá un incremento en la expresión de genes profibróticos, como TGF-β1 y citocinas pro inflamatorias [25]. El aumento en la expresión de TGF-β1, también contribuirá al desarrollarlo de la fibrosis renal, al unirse a receptores específicos a nivel renal, estimulara la expresión de factores profibróticos en un ciclo de retroalimentación positiva. Además, TGF-β1 es un potente iniciador de proliferación de células mesangiales renales [25]. Debido a su tamaño relativamente pequeño, la leptina atraviesa libremente el filtro glomerular de los riñones y luego se reabsorbe en la parte proximal de los túbulos contorneados [23]. Por lo que el estado elevado de leptina puede indicar una función renal deficiente [36]. Promueve la inflamación y trastorno de los lípidos, que contribuyen al riesgo de ERC [36]; se considera como “toxina urémica”, estando implicada tanto en la progresión de la enfermedad renal a través de efectos pro-hipertensivos y profibróticos, como en el desarrollo de complicaciones relacionadas con la ERC (inflamación crónica, pérdida de proteínas) [38]. Como se mencionó previamente, la leptina estimula la proliferación de células endoteliales glomerulares renales y aumenta la expresión de TGF-β1, un mediador clave de la hidrogénesis en estas células, el aumento de los niveles de leptina también contribuye al aumento de la expresión de colágeno tipo IV en el riñón, induce la proliferación de células mesangiales glomerulares mediante la activación de la vía PI3K, la hipertrofia de las células mesangiales aumenta la cantidad de proteína filtrada y albúmina que llega a las células del túbulo proximal y, como resultado, activa las vías inflamatorias y la fibrosis [23]. Puede presentarse un aumento en la síntesis del receptor TGFβ-1 secretado por las células endoteliales, este actúa de manera parácrina sobre el mesangio uniéndose a su receptor y activando la síntesis de proteínas de la matriz extracelular (ECM), incluyendo colágeno, fibronectina, tenazina y proteoglicanos; consiguientemente, un aumento en el nivel de TGFβ-1 conduce a la acumulación de MEC y, en consecuencia, a fibrosis glomerular y glomeruloesclerosis. En los podocitos, la leptina contribuye a la disminución de la expresión de las proteínas responsables de la filtración glomerular adecuada, incluidas la podocina, la nefrina, la podoplanina y la podocalixina. En las células del túbulo contorneado proximal (PTC), la leptina reduce la actividad metabólica de las células al activar la vía de señalización de mTOR [23]. Por otro lado, la leptina inhibe el apetito y aumenta el gasto de energía conduciendo a anorexia y desnutrición en pacientes con ERC, particularmente en casos de hemodiálisis de mantenimiento [36]. Por ende, una elevación de la leptina no solo nos indicaría daño renal, sino que además nos indica mayor progresión de complicaciones secundarias [39]. La obesidad aumenta la carga sobre los riñones y es un factor de riesgo de lesión renal, además de contribuir en los trastornos metabólicos asociados. Por lo que, teniendo en cuenta los efectos inhibitorios de la leptina sobre la obesidad, se puede considerar que puede proteger contra la lesión renal [39, 40]. Un estudio experimental publicado en el año 2017 demostró que la leptina disminuyó la ingesta calórica y los niveles de glucosa en ratas diabéticas [41], ese mismo año se publicó un estudio retrospectivo donde demostraron que la metreleptina, una metionil leptina humana recombinante, reduce el peso corporal y la dosis diaria de insulina en la diabetes mellitus tipo 1 [42]. La metreleptina ejerce efectos terapéuticos en la lipodistrofia [43], lo que indica que es probable que la leptina se aplique en los trastornos metabólicos [36]. Otras adipocinas Las principales adipocinas corresponden a la adiponectina y leptina como se ha descrito previamente. Además de estas, se distinguen la actividad de la visfatina y resistina, las cuales muestran propiedades pro-inflamatorias y efectos aterogénicos [25]. La visfatina estimula la expresión de TGF-β1, inhibidor del activador del plasminógeno-1 (PAI-1) y colágeno tipo I, los cuales han demostrado un rol importante como agentes profibróticos. Por otro lado, la resistina estimula la producción de las moléculas de adhesión como la molécula de adhesión intracelular 1 (ICAM-1) y la proteína de adhesión celular vascular 1 (VCAM-1) y promueve la activación del sistema renal simpático. Los niveles de estas adipocinas están marcadamente elevados en la obesidad y ERC correlacionándose con parámetros proinflamatorios y disminución de la tasa de filtración glomerular (TFG) [25, 37]. Durante el curso de la obesidad se presenta una sobre activación del SRAA, el tejido adiposo también estaría involucrado en la producción o estimulación de algunos de los componentes del RAS. Por ello la sobre estimulación del SRAA en obesos, asociado a la glomerulomegalia y desregulación de la reabsorción de sodio/glucosa, generalmente conlleva a hipertensión glomerular e hiperfiltración [25]. Otra adipocina a considerar, es la actividad de la adipocina proinflamatoria lipocalina 2 (LCN2), también denominada lipocalina asociada con la gelatinasa de neutrófilo (NGAL), estudiada como biomarcador funcional tanto para la enfermedad renal aguda como ERC(25). LCN2 es conocido por su papel en la respuesta inmune innata a través de su unión a sideróforos derivados de una infección bacteriana. Sin embargo, LCN2 no es secretada únicamente por neutrófilos sino también por otros tejidos como hígado, pulmones y de interés para este artículo, a nivel renal [25]. Se han informado niveles elevados de LCN2 en suero y orina en la lesión renal, debido a una expresión aumentada de LCN2 en el túbulo distal renal y una reabsorción alterada en el túbulo proximal [44]. El tejido adiposo, también puede producir factores angiogénicos como el factor de crecimiento del endotelio vascular (VEGF). Este elemento podría inducir la formación de novo de capilares glomerulares en gran parte defectuosos dentro del riñón, lo que contribuye a la hipertrofia glomerular característica de GRO [25] (Figura 2). Conclusiones La obesidad y el sobrepeso se asocian a alteraciones hemodinámicas, estructurales e histopatológicas en el riñón, así como alteraciones metabólicas y bioquímicas que predisponen a la enfermedad renal, aun cuando la función renal y las pruebas convencionales sean normales. Por lo tanto, los efectos renales de la obesidad son estructurales y funcionales. Hay varios mecanismos actualmente descritos que involucran a la obesidad como generador de alteraciones renales. Teniendo en cuenta las bases fisiopatológicas, proponemos una clasificación de la ERC-AO basadas en 4 tipos. Abreviaturas ERC: enfermedad renal crónica. ERC-AO: enfermedad renal crónica-asociada a enfermedad. VEGF: factor de crecimiento del endotelio vascular. OR: Odds ratio. Información suplementaria Materiales suplementarios no han sido declarados. Agradecimientos No aplica. Contribuciones de los autores Jorge Rico-Fontalvo: Conceptualización, Curación de datos, Análisis formal, Adquisición de fondos, Investigación, Metodología, Administración de proyecto, Recursos, Software, Escritura – borrador original. Rodrigo Daza-Arnedo: Conceptualización, Supervisión, Validación, Visualización, Redacción: revisión y edición. Tomás Rodríguez-Yanez: Metodología, validación, supervisión, redacción: Revisión y edición. Washington Osorio: Conceptualización, Supervisión, Validación, Visualización, Redacción: revisión y edición. Beatriz Suarez-Romero: Conceptualización, Supervisión, Validación, Visualización, Redacción: revisión y edición. Oscar Soto: Conceptualización, Supervisión, Validación, Visualización, Redacción: revisión y edición. Juan Montejo-Hernandez: Conceptualización, Supervisión, Validación, Visualización, Redacción: revisión y edición. María Cardona-Blanco: Conceptualización, Supervisión, Validación, Visualización, Redacción: revisión y edición. Juan Camilo Gutiérrez: Conceptualización, Supervisión, Validación, Visualización, Redacción: revisión y edición. Todos los autores leyeron y aprobaron la versión final del manuscrito. Financiamiento Los autores proveyeron los gastos de la investigación. Disponibilidad de datos o materiales Los conjuntos de datos generados y analizados durante el estudio actual no están disponibles públicamente debido a la confidencialidad de los participantes, pero están disponibles a través del autor correspondiente a pedido académico razonable. Declaraciones Aprobación del comité de ética y consentimiento para participar No aplica para revisiones narrativas. Consentimiento para publicación No aplica cuando no se publican imágenes o fotografías del examen físico o radiografías/tomografías/resonancias de pacientes. Conflictos de interés Los autores reportan no tener conflictos de interés. 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Abstract: Histone deacetylases (HDACs) are essential for maintaining homeostasis by catalyzing histone deacetylation. Aberrant expression of HDACs is associated with various human diseases. Although HDAC inhibitors are used as effective chemotherapeutic agents in clinical practice, their applications remain limited due to associated side effects induced by weak isoform selectivity. HDAC1 displays unique structure and cellular localization as well as diverse substrates and exhibits a wider range of biological functions than other isoforms. HDAC1 displays a unique structure primarily found in the nucleus and involved in epigenetic and transcriptional regulation.HDAC1 is ubiquitously expressed and associated with Sin3, NuRD, and CoRest transcription repressive complexes responsible for distinct cellular processes like cell proliferation and survival.HDAC1 inhibitors have been effectively used to treat various cancers such as gastric, breast, colorectal, prostate, colon, lung, ovarian, pancreatic, and inflammation reactions without exerting significant toxic effects. In this review, we summarize four major structural classes of HDAC1 inhibitors (i.e., hydroxamic acid derivatives, benzamides, hydrazides, and thiols) with their structural activity relationship. This review is a comprehensive work on HDAC1 inhibitors to achieve deep insight of knowledge about the structural information of HDAC1 inhibitors. It may provide up-to-date direction for the development of new selective HDAC1 inhibitors as anticancer agents.

Hypertension is related to alterations of sodium homeostasis that promote abnormal accumulation of water in the intravascular compartment leading to blood pressure elevation. This process can been associated with increased heart mass resulting in cardiac hypertrophy. At cellular level, the concentration and active transport of Na+ is regulated by Na+,K+-ATPase enzyme (NK). In vitro studies have shown a correlation between high blood pressure, NK and SIK activities. Increases in intracellular Na+ are paralleled by elevations in intracellular Ca2+ via NCX1, leading to the activation of SIK1 by a Ca2+/calmodulin-dependent kinase. Activation of SIK1 results in the dephosphorylation of the NK α-subunit and an increase in its catalytic activity. Accordingly, the aim of the present study was to evaluate the cardiac Na+ sensing network changes associated with hypertension in aging hypertensive rats. Systolic and diastolic blood pressures, determined by the tail-cuff method, were significantly higher in 3, 13 and 21-month old SHR than in age-matched WKY. In the SHR, ageing was associated with increases in cardiac mass, gene expression of hypertrophic (α-skeletal muscle actin and β-myosin heavy chain) markers as well as inflammatory cytokine (IL-6). The decreased expression of heart SIK isoforms, SIK1 and SIK3, was associated with downregulation of transcription factors Snail2, Zeb1, MFAT5c and KLF4, in 13 and 21-month old SHR. Cardiac α2-isoform of NK was found to be decreased in 21 month old SHR. Whereas, NKα1, NHE3 and NCX1 showed no differences between age-matched SHR and WKY. Na+-dependent ASCT2 and Na+-independent LAT1 amino acid transporter transcript levels of were significantly higher in 21 month old SHR than in WKY. In the aged SHR, cardiac hypertrophy was associated with dysregulation of several elements of the intracellular Na+ sensing network. Downregulation of SIK1 and transcription factors is correlated with expression of NKα2, suggesting impaired sodium handling. It is proposed that, cardiac hypertrophy is not exclusively the consequence of mechanical stress but also of other factors associated with elevated blood pressure such as abnormal cell sodium homeostasis.Supported by grant PIC/IC/83204/2007.

Abstract Background and Aims ATP-dependent phosphofructokinases (PFKs) catalyse phosphorylation of the carbon-1 position of fructose-6-phosphate, to form fructose-1,6-bisphosphate. In the cytosol, this is considered a key step in channelling carbon into glycolysis. Arabidopsis thaliana has seven genes encoding PFK isoforms, two chloroplastic and five cytosolic. This study focusses on the four major cytosolic isoforms of PFK in vegetative tissues of A. thaliana. Methods We have isolated homozygous knock-out individual mutants (pfk1, pfk3, pfk6, pfk7) and two double mutants (pfk1/7 and pfk3/6) and characterized their growth and metabolic phenotypes. Key Results In contrast to single mutants and the double mutant pfk3/6 for the hypoxia-responsive isoforms, the double mutant pfk1/7 had reduced PFK activity and shows a clear visual and metabolic phenotype with reduced shoot growth, early flowering, and elevated hexose levels. This mutant also has an altered ratio of short/long aliphatic glucosinolates and an altered root-shoot distribution. Surprisingly, this mutant does not show any major changes in short-term carbon flux and in levels of hexose-phosphates. Conclusions We conclude that the two isoforms PFK1 and PFK7 are important for sugar homeostasis in leaf metabolism and apparently source/sink relations in Arabidopsis, while PFK3 and PFK6 only play a minor role under normal growth conditions.

Numerous reports have highlighted the importance of protein kinases and transcription factors in cardiogenesis and cardiac hypertrophy. The salt-inducible kinase 1 (SIK1), a protein kinase encoded by the snf1lk gene, is involved in early cardiogenesis in mice. Genotype-phenotype association studies in three Swedish and one Japanese population-based cohorts suggested that 15Ser-SIK1 variant (15Gly-Ser change, T allele), bestow augmented SIK1 activity, was associated with lower blood pressure and decreases in left ventricular (LV) mass. The present study aims to determine the potential role of SIK1 as a mediator of cardiac hypertrophic signaling pathway and to evaluate age-related changes on the cardiac expression of several elements of the SIK network associated with hypertension, in Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR). For this purpose, mRNA expression levels of skeletal actin (SkA), β-myosin heavy chain (β-MHC) and matrix metalloproteinase-9 (MMP-9) as markers for cardiac hypertrophy, SIK isoforms (SIK1, SIK2 and SIK3), and transcription factors (MEF2C, NFAT5c, KFL4, Snail1 and Snail2) were determined, using Taqman, in 13- , 52- and 91-week old SHR and their normotensive counterparts WKY. Systolic and diastolic blood pressures, determined by the tail-cuff method, were significantly higher in 3- , in 3- , 13- and 21-month old SHR than in age-matched WKY. In the SHR, increases in heart/tibia length ratio were associated to the overexpression of cardiac hypertrophic genes (SkA and β-MHC) and the underexpression of cardiac SIK3, at the age of 3- , 13- and 21-months. Ageing accompanied by a diminished mRNA expression of SIK1 in SHR, relative to WKY (both at 13- and 21-months of age). Whereas, Snail2, MFAT5c and KLF4 mRNA levels decreased with aged SHR, comparing to age-match WKY (both at 13- and 21-months of age). These results indicate that SIK1 and SIK3 isoforms might be upstream mediators of transcriptions factors implicated in the regulation of cardiac hypertrophic growth response. In conclusion, ageing in SHR is accompanied by cardiac alterations that include hypertrophy and dysfunction of the SIK signaling network. Supported by grant PIC/IC/83204/2007.

AbstractSIN3/HDAC is a multi-protein complex that acts as a regulatory unit and functions as a co-repressor/co-activator and a general transcription factor. SIN3 acts as a scaffold in the complex, binding directly to HDAC1/2 and other proteins and plays crucial roles in regulating apoptosis, differentiation, cell proliferation, development, and cell cycle. However, its exact mechanism of action remains elusive. Using the Caenorhabditis elegans (C. elegans) model, we can surpass the challenges posed by the functional redundancy of SIN3 isoforms. In this regard, we have previously demonstrated the role of SIN-3 in uncoupling autophagy and longevity in C. elegans. In order to understand the mechanism of action of SIN3 in these processes, we carried out a comparative analysis of the SIN3 protein interactome from model organisms of different phyla. We identified conserved, expanded, and contracted gene classes. The C. elegans SIN-3 interactome -revealed the presence of well-known proteins, such as DAF-16, SIR-2.1, SGK-1, and AKT-1/2, involved in autophagy, apoptosis, and longevity. Overall, our analyses propose potential mechanisms by which SIN3 participates in multiple biological processes and their conservation across species and identifies candidate genes for further experimental analysis.