Dissertationen zum Thema „Energy metabolism“

Ames dwarf mice have a spontaneous homozygous Prophet of Pituitary Factor 1 (Prop1) loss-of-function mutation. The Prop1 mutation results in a lack of differentiation of lactotrophs, thyrotrophs, and somatotrophs in the anterior pituitary. Without these endocrine cell types, Ames dwarf mice have essentially no circulating levels of growth hormone (GH), thyroid-stimulating hormone (TSH), and prolactin, and exhibit downstream hormonal deficiencies including insulin-like growth factor 1 (IGF-1), 3’,3,5-triiodothyronine (T3), and thyroxine (T4). Ames dwarf mice are exceptionally long-lived (40% to over 60% depending on sex and diet). They are also extremely insulin sensitive, have a delayed incidence of cancer, and have improved energy metabolism. While the extended lifespan and the many characteristics of an extended healthspan have been known for some time in Ames dwarf mice, the revelation that dwarf mice have improved energy metabolism was less than a decade ago. This finding came about at the molecular level (improved efficiency of the electron transport chain) and at the whole-animal level (increased oxygen consumption and decreased respiratory quotient). To date, however, few studies have been directed at furthering our understanding of the possible mechanism(s) by which Ames dwarf mice have altered energy metabolism. The goal of the studies presented in this dissertation is to delineate these mechanisms and to lay the groundwork for future studies that broaden our understanding of the role(s) of energy metabolism in the aging process. Project 1 examines the effects of early-life T4 replacement therapy in Ames dwarf mice. Previous work established that life-long T4 replacement therapy shortens lifespan in Snell dwarf mice (these mice have endocrine deficits that are essentially identical to those of Ames dwarf mice), while short-term replacement therapy during the early postnatal period of Ames dwarf mice does not. We hypothesized that T4 replacement therapy causes transient impairment of energy metabolism, which is why long-term T4 replacement therapy shortens longevity, and short-term replacement therapy does not. Supporting our hypothesis, we showed that short-term T4 replacement therapy during the early postnatal period transiently impaired energy metabolism as measured by indirect calorimetry. Following early-life T4 replacement therapy, we also observed an accelerated rate of sexual development, as well as lasting effects on bone physiology. Project 2 continued our investigation of energy metabolism by examining a highly metabolic tissue: brown adipose tissue (BAT), which is responsible for non-shivering thermogenesis. Our laboratory has already demonstrated functional alterations in visceral adipose tissue of Ames dwarf mice, and given the altered energy metabolism of Ames dwarf mice, we hypothesized that BAT may also be functionally unique compared to their normal littermates. Supporting our hypothesis, we observed alterations in gene expression, relative weight, and histological structure of BAT in Ames dwarf mice. Moreover, surgical removal of the interscapular BAT depot resulted in a unique physiological response, where Ames dwarf mice lost adiposity in their subcutaneous, perirenal, and epididymal white adipose tissue depots, thus contrasting with normal mice that gained adiposity. Project 3 built upon the findings of our second study, where we continued to examine the role of non-shivering thermogenesis and core body temperature in Ames dwarf mice. To further understand the role of non-shivering thermogenesis in glucose homeostasis and energy metabolism, we housed a cohort of Ames dwarf mice and their normal littermates at room temperature (23˚C), and another cohort at thermoneutrality (for mice this is 30˚C). We found that Ames dwarf mice placed at thermoneutrality had impaired glucose homeostasis and energy metabolism. This is an important finding because we and others believe both of these metabolic processes are important factors for longevity. Taken together, these studies indicate that the improved energy metabolism in Ames dwarf mice is dependent upon several factors, including a loss of thyroid hormone signaling and improved non-shivering thermogenesis.

Zasadnicznym celem przeprowadzonych badań była ocena skuteczności wykorzystania danych z okresowej kontroli użytkowości mlecznej w typowaniu krów z zaburzeniami metabolizmu energetycznego i wpływie opóżnienia u nich terminu pierwszej inseminacji na wskaźniki rozrodcze stada
The aim of the research was to assess the effectiveness of the use of data from periodic control of dairy utility in the selection of cows with energy metabolism disturbances and the impact of their delay in the first insemination on the reproductive indicators of the herd

Thesis advisor: Thomas N. Seyfried
It has long been posited that all cancer cells are dependent on glucose for energy, termed the "Warburg Effect". As a result of an irreversible injury to the mitochondria, cancer cells are less efficient in aerobic respiration. Therefore, calorie restriction was thought to be a natural way to attenuate tumor growth. Calorie restriction lowers blood glucose, while increasing the circulation of ketone bodies. Ketone bodies are metabolized via oxidative phosphorylation in the mitochondria. Only cells that are metabolically capable of aerobic respiration will thus be able to acquire energy from ketone bodies. To date, calorie restriction has been shown to greatly reduce tumor growth and angiogenesis in the murine CT2A, EPEN, and human U87 brain tumor models. Using the novel VM-M3 model for invasive brain cancer and systemic metastatic cancer, I found that though calorie restriction had some efficacy in reducing brain tumor invasion and primary tumor size, metastatic spread was unaffected. Using a bioluminescent-based ATP assay, I determined the viability of metastatic mouse VM-M3 tumor cells grown in vitro in serum free medium in the presence of glucose alone (25 mM), glutamine alone (4 mM), or in glucose + glutamine. The VM-M3 cells could not survive on glucose alone, but could survive in glutamine alone indicating an absolute requirement for glutamine in these metastatic tumor cells. Glutamine could also maintain viability in the absence of glucose and in the presence of the F1 ATPase inhibitor oligomycin. Glutamine could not maintain viability in the presence of the Krebs (TCA) cycle enzyme inhibitor, 3-nitropropionic acid. The data indicate that glutamine can provide ATP for viability in the metastatic VM-M3 cells through Krebs cycle substrate level phosphorylation in the absence of energy from either glycolysis or oxidative phosphorylation. I therefore developed a metabolic therapy that targeted both glucose and glutamine metabolism using calorie restriction and 6-diazo-5-oxo-L-norleucine (DON), a glutamine analog. Primary tumor growth was about 20-fold less in DON treated mice than in untreated control mice. I also found that DON treatment administered alone or in combination with CR inhibited metastasis to liver, lung, and kidney as detected by bioluminescence imaging and histology. Although DON treatment alone did not reduce the incidence of tumor metastasis to spleen compared to the controls, DON administered together with CR significantly reduced the incidence of metastasis to the spleen, indicating a diet/drug synergy. In addition, the phagocytic capabilities of the VM-M3 tumor cells were enhanced during times of energy stress. This allowed for the digestion of engulfed material to be used in energy production. My data provide proof of concept that metabolic therapies targeting both glucose and glutamine metabolism can manage systemic metastatic cancer. Additionally, due to the phagocytic properties of the VM-M3 cell line also seen in a number of human metastatic cancers, I suggest that a unique therapy targeting metabolism and phagocytosis will be required for effective management of metastatic cancer
Thesis (PhD) — Boston College, 2010
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Biology

Tumor metabolism is a highly dysregulated process that is identified as a unique target for therapy. Current philosophy proposes that tumor metabolism is a plastic and flexible process which sustains proliferative and survival advantages. Tumors employ an anaerobic glycolytic pathway resulting in the overproduction of lactate. Additional thinking suggests that the conversion of pyruvate to lactate regenerates the NAD+ pool in the cell, maintaining a sustainable oxidative environment. Regardless of the reasons for lactate overproduction, its excretion and build up in the microenvironment results in acidic tumor microenvironments. Tumor acidosis has been measured with several different methods, but consistently averages from pH 6.6 to 7.0. Tumor acidity can thus be measured as a biomarker for tumor metabolism. This work examines the commonly explored energy pathways available to the cancer cell and a non-invasive MRI method to measure the efficacy of the tumor metabolism targeting agent. Appendix A is an introduction to tumor metabolism pathways and the large list of candidate therapies in interfering with energy production. Glucose, fatty acid, and glutamine metabolisms are all discussed along with PI3K/AKT/mTOR and HIF growth signals and ion transport. Magnetic resonance imaging and positron emission tomography are examined as imaging methods for non-invasively interrogating tumor acidosis. Appendix B presents the findings in a study where tumor metabolism was targeted with an mTOR inhibitor, where tumor growth rate was initially decreased and accompanied by an early, acute increase in tumor extracellular pH with acidoCEST MRI. Chapter 2 discusses the combination of a lactate dehydrogenase inhibitor in conjunction with doxorubicin in a breast cancer model. Tumor extracellular pH was shown to increase when measured with acidoCEST MRI, and an increase in cell death was measured. Chapter 4 discusses the studies and experimental designs that can be done in the near future.

Cada cop més evidencies suggereixen que els astròcits participen en les altes funcions cerebrals, controlant des de la transmissió sinàptica fins a les ones cerebrals globals i els processos d’aprenentatge i memòria. Diferents mecanismes han sigut proposats com a responsables d’aquests processos mediats per astròcits, entre ells, l’alliberació de gliotransmissors a partir de les senyals de calci així com la de lactat semblen els principals efectors. L’existència d’aquest control de les funcions cerebrals per part dels astròcits suggereix que aquestes cèl·lules poden regular les funcions cerebrals en resposta a experiència tan com les neurones, constituint el fenomen de plasticitat astrocitària. En neurones s’ha demostrat que el conegut factor de transcripció CREB, coordina les plasticitats sinàptica i intrínseca. El fet que, en astròcits, l’activació de CREB també està regulada per activitat cerebral, situa aquest factor de transcripció com a la diana ideal per promoure canvis dependents d’activitat en astròcits. En aquesta tesi hem analitzat l’efecte de l’activació de la transcripció depenent de CREB en astròcits, centrant-nos en l’excitabilitat del calci i en el metabolisme d’aquestes cèl·lules. Hem demostrat que l’activació de la transcripció depenent de CREB redueix les senyals citosòliques de calci a través del mitocondri a la vegada que augmenta l’alliberació de lactat, dos canvis que poden tenir impacte en la transmissió sinàptica. Una altra contribució important d’aquest estudi es l’anàlisi molecular dels mitocondris dels astròcits, que ha revelat que aquestes cèl·lules poden utilitzar metabòlits que no són glucosa, com ara àcids grassos, per respondre a les necessitats metabòliques energètiques. Els nostres resultats estableixen el CREB en astròcits con un eix de la plasticitat astrocitària i revelen la interacció entre la plasticitat i el metabolisme energètic en astròcits. Aquests descobriments constitueixen un avenç mecanístic i conceptual en el coneixement de la biologia dels astròcits i com aquestes cèl·lules poden controlar l’aprenentatge i la memòria.
An increasing body of evidence suggests that astrocytes participate in higher-brain functions, controlling from synaptic transmission to global brain waves and learning and memory processes. Different mechanisms have been proposed to mediate these astrocyte-dependent processes, astrocytic lactate release and calcium-dependent gliotransmission being the main known effectors. The existence of control of brain functions by astrocytes suggests that astrocytes may shape brain functions in response to experience as much as neurons, thus constituting the phenomenon of astrocyte plasticity. In neurons, the transcription factor CREB is the best known coordinator of synaptic and intrinsic plasticity. The fact that, in astrocytes, CREB activation is also activity-dependent, positions CREB as an ideal target to promote plasticity-related changes in astrocytes, too. In this thesis, we have analyzed the effect of the activation of CREB-dependent transcription in astrocytes, specifically regarding calcium signals and metabolism. We have demonstrated that activation of CREB-dependent transcription reduces cytosolic calcium events via mitochondria and increases in lactate release, which may have impact on synaptic transmission. An important contribution of the study is the molecular analysis of astrocytic mitochondria, which has revealed that astrocytes may use fuels other than glucose such as fatty acids to meet basic energy metabolic demands. Taken together, our results establish astrocytic CREB as a hub in astrocyte-plasticity and shed light on the interplay between plasticity and energy metabolism in astrocytes; these findings constitute a conceptual and mechanistic advance in the knowledge of astrocytic biology and how these cells may control learning and memory.

Aspects of the resting respiration rate, specific dynamic action (SDA) and components of the total energy budget of 55 - 80g common carp were studied in the laboratory. The resting respiratory rate was monitored in computer operated metabolic chambers under different photoperiods. Common carp showed a crepuscular respiratory rhythm with peaks at dawn and dusk during a 12L : 12D photoperiod, with a mean oxygen consumption of 152 mg/kg/h. When acclimated to longer or shorter photoperiods respiration was also cyclic but with a lower mean respiratory rate. In continuous light or darkness respiratory rhythm was suppressed with no significant peakings. In carp fed with three diets containing 20,35 and 50% protein at a ration level of 0.40 to 1.00% body weight per day, SDA coefficient varied from 8.99 to 15.94% and was dependent on dietary protein but not on ration levels. SDA magnitude and post-feeding peak oxygen consumption varied significantly with both dietary protein content and total daily ration level. SDA duration was only related to ration size. The pattern of food energy allocation between the major components of the energy budget varied with dietary protein content and ration levels. The energy lost as heat of metabolism was found to increase with dietary protein level and total ration. Energy lost as faeces 'F' varied from 19 - 24% of 'C' and did not appear to be related to either protein content or ration levels. Nitrogenous excretion increased with an increase of dietary protein but decreased with an increase of ration level in the diet. Regression equations were developed from the data to allow prediction of respiratory energy loss 'R', faecal energy loss 'F' and energy lost through excretion 'U' from the food ingested V. Complete energy budget models compiled from experiments conducted over a 17 days period and using different diets did not successfully predict the actual growth. The energy budget balance was between 66.04% and 81.96%. Observed growth was less than predicted growth in every trial and it is suggested that this difference might have been due to short-term cyclic growth regulation and other minor experimental features. The data presented form the basis for the first reported study of total energy budgets in Cyprinus carpio.

The purpose of this study was to examine the caloric intake and energy output of swimmers and runner during normal daily activities and training. Daily and energy expenditure of twenty college varsity swimmers and runners were measured. Four groups of subjects were categorized as male runners, female runners, male swimmers, and female swimmers with five subjects in each group. An additional twenty runners and swimmers recorded only dietary intake. Despite a large difference in body weight and body fat, the mean daily caloric intake was similar for the two groups (male swimmers: 3377 Kcal/d-1, male runners: 3463 Kcal/d-1, female swimmers: 2491 Kcal/d-1, female runners: 2037 Kcal/d-1). Comparison of data normalized for body weight showed that male runners were more active than swimmers. Male runners burned more calories (53.3 Kcal/kg. d-1) in a twenty four hour period than swimmers (47.6 Kcal/kg.d-1). In the case of the females, the trend was reversed. Female swimmers expended more calories (45 Kcal/kg .d-1) than runners (38.9 Kcal/kg.d-1) despite a lower food intake. Consequently, caloric intake and life style does not seem to explain body fat difference between runners and swimmers. The data in this study suggest that the greater body fat found in swimmers may be related to a physiological adaptation induced by swim training.

L’objectiu d’aquesta tesis es desenvolupar una nova estratègia preventiva i terapèutica que requereixi les mínimes modificacions dels hàbits dietètics simultàniament efectiva en contra de l’obesitat i les seves malalties associades. Per aquest estudi s’han seleccionat compostos alimentaris presents en una dieta sana on el seus efectes beneficiosos han estat documentats tant en la obesitat com el risc de patir malalties cardiovasculars. S’inclou els polifenols com l’epigallocatechin gallate (EGCG) i les proantocyanidines i també els àcids grassos poliinsaturats omega 3 (PUFAs) o l’àcid docosahexaenoic (DHA). El treball esta enfocat en el funcionament mitocondrial del múscul, el teixit mes important de l’organisme en el control del balanç de nutrients. Els nostres resultats indiquen que hi ha una millora postprandial amb un increment de la capacitat d’oxidació dels àcids grassos millorant el perfil lipídic i la flexibilitat metabòlica.
El objetivo principal de esta tesis es desarrollar una nueva estrategia preventiva y terapéutica que requiera les mínimas modificaciones de los hábitos dietéticos simultáneamente efectiva en contra de la obesidad y sus enfermedades asociadas. Para este estudio se han seleccionado compuestos alimentarios presentes en una dieta sana dónde sus efectos beneficiosos han estado documentados tanto en la obesidad como en el riesgo de desarrollar enfermedades cardiovasculares. Se incluyen los polifenoles como el epigalocatequin galato (EGCG) y las proantocianidinas; también los ácidos grasos poliinsaturados omega 3 (PUFAs) y el acido docosahexaenoico (DHA). El trabajo está enfocado en el funcionamiento mitocondrial de musculo, el tejido más importante del organismo en el control del balance de nutrientes. Nuestros resultados indican que hay una mejora postprandial con un incremento de la capacidad de oxidación de los ácidos grasos mejorando el perfil lipídico y la flexibilidad metabólica.
The global goal of the present thesis is the development of a new preventative and therapeutic strategy that requires only minor modifications of dietary habits and simultaneously effective against obesity and its major associated diseases. For this study, we have selected food ingredients characteristic in healthy diets which has been documented beneficial effects on obesity or cardiovascular disease risk. These include plant polyphenols, epigallocatechin gallate (EGCG) and proanthocyanidins as well as the sea fish omega-3 polyunsaturated fatty acids (PUFAs) and docosahexaenoic acid (DHA). Our work is focused on the mitochondrial function of skeletal muscle, a major player in the body’s overall nutrient balance, and adipose tissue, which is the key regulator of energy homeostasis in the organism affected by obesity and related diseases. Our results indicate a postprandial improvement with an increase of the fatty acid oxidation capacity, improving lipid profile and metabolic flexibility.

Thesis (Ph. D.)--University of Missouri-Columbia, 2005.
Title from title screen of research.pdf file (viewed on December 22, 2006). The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. "May 2005" Vita. Includes bibliographical references.

The objectives of this research were to: 1) evaluate the accuracy of the Molly cow model predictions of ruminal metabolism and nutrient digestion when simulating dairy and beef cattle diets, 2) advance representations of N recycling between blood and the gut and urinary N excretion in the model, 3) improve the representation of pH and to refit parameters related to ruminal metabolism and nutrient digestion in the model, 4) investigate how ruminal pH affects the microbial community, expression of carbohydrate-active enzyme transcripts (CAZymes), fiber degradation, and short chain fatty acid (SCFA) concentrations. To achieve the first objective, a total of 229 studies (n = 938 treatments) including dairy and beef cattle data, published from 1972 through 2016, were collected from the literature and used to assess the model accuracy and precision based on root mean squared errors (RMSE) and concordance correlation coefficients (CCC). Only slight mean and slope bias were exhibited for ruminal outflow of NDF, starch, lipid, total N, and non-ammonia N, and for fecal output of protein, NDF, lipid, and starch. However, ruminal pH was poorly simulated and contributed to problems in ruminal nutrient degradation and VFA production predictions. To achieve the second objective, representations including ruminal ammonia outflow, intestinal urea entry, microbial protein synthesis in the hindgut, and fecal urea N excretion, were added in the model. Total urea entry, gut urea entry, and urinary urea elimination rates collected from 15 published urea kinetics studies were used to derive related parameters. Significant improvements in predictions of variables describing ruminal N metabolism, blood urea metabolism and urinary N secretion were exhibited after the modifications. To achieve the third objective, a dataset assembled from the literature containing 284 peer reviewed studies with 1223 treatment means was used to derive parameter estimates for ruminal metabolism and nutrient digestions. After refitting the parameters, the model is even more robust in representing ruminal nutrient degradation compared to the initial model. Adding ammonia concentration as a driver to the pH equation increased the precision of predicted ruminal pH, and thereby, the precision of predicted VFA concentrations due to an improved representation of pH regulation of VFA production rates. To achieve the fourth objective, six cannulated Holstein heifers with an initial BW of 362 ± 22 kg (mean ± SD) were subjected to 2 treatments in a cross-over design. The treatments were 10 days of intraruminal infusions of both 1) distilled water (Control), and 2) a dilute blend of hydrochloric and phosphoric acids to achieve a pH reduction of 0.5 units (LpH). Statistical analyses indicated 19 bacterial genera and 4 protozoal genera were affected by low ruminal pH. We observed significant correlations between 54 microbes (43 bacterial and 11 protozoal genera) and 25 enzymes, of which 8 key enzymes participated in reactions leading to SCFA production, suggesting that the ruminal microbial community alters fiber catalysis and fermentation in response to altered pH through a shift in carbohydrate-active enzyme transcripts (CAZymes) expression. Overall, after the modifications and reparameterizations, 19.7 to 37.5% of RMSE with essentially no slope bias and minor mean bias were exhibited for of ruminal and fecal outflow of ADF, NDF, fat, and protein, suggesting the model is properly to represent nutrient degradation and digestion in the bovine. Considering ruminal microbes and CAZymes in predicting ruminal volatile fatty acid concentrations could explain more variance of observations.
Ph. D.
The purpose of this research was to improve ruminal nutrient metabolism and nutrient digestion representations in the Molly cow model. First, the model accuracy and precision were assessed using a dataset including 229 studies (n = 938 treatments) conducted with dairy and beef cattle. The model evaluation results indicated the mechanisms encoded in the model relative to ruminal and total tract nutrient digestion are properly represented. However, ruminal pH was very poorly represented in the model with a RMSE of 4.6% and a concordance correlation coefficient (CCC) of 0.0. Although VFA concentrations had negligible mean (2.5% of MSE) and slope (6.8% of MSE) bias, the CCC was 0.28 implying that further modifications with respect to VFA production and absorption are required to improve model precision. As identified by the residual analyses, the representations of N recycling between blood and the gut were improved by considering ruminal ammonia outflow, intestinal urea entry, microbial protein synthesis in the hindgut, and fecal urea N excretion in the model. Observations of total urea entry, gut urea entry, and urinary urea elimination rates were collected from 15 published urea kinetics studies were used to derive related parameters. After the modifications, prediction errors for ruminal outflows of total N, microbial N, and non-ammonia non-microbial N were 39.5, 27.8 and 35.9% of the respective observed mean values. Prediction errors of each were approximately 10% units less than the corresponding values before model modifications and fitting due primarily to decreased slope bias. The revised model predicted ruminal ammonia and blood urea concentrations with substantially decreased overall error and reductions in slope and mean bias. After that, ammonia concentration as a driver was added to the pH equation, and a dataset assembled from the literature containing 284 peer reviewed studies with 1223 treatment means was used to derive parameter estimates for ruminal metabolism and nutrient digestions. Refitting the parameters significantly improved the accuracy and precision of the model predictions for ruminal nutrient outflow (ADF, NDF, total N, microbial N, non-ammonia N, and non-ammonia, non-microbial N), ammonia concentrations, and fecal nutrient outflow (protein, ADF, and NDF). Therefore, the improved model can be used to simulate nutrient degradation and digestion in the bovine. Although minor mean and slope bias were observed for ruminal pH and VFA concentrations, the small values for concordance correlations indicated much of the observed variation in these variables remains unexplained. To further explain variance in ruminal metabolism and understand how ruminal pH affects the microbial community, expression of carbohydrate-active enzyme transcripts (CAZymes), fiber degradation, and short chain fatty acid (SCFA) concentrations, six cannulated Holstein heifers with an initial BW of 362 ± 22 kg (mean ± SD) were subjected to 2 treatments in a cross-over design. We observed 19 bacterial genera and 4 protozoal genera were affected by low ruminal pH, and significant correlations between 54 microbes (43 bacterial and 11 protozoal genera) and 25 enzymes, of which 8 key enzymes participated in reactions leading to SCFA production. In summary, after the modifications and reparameterizations, the model is even more robust to represent nutrient degradation and digestion in bovine compared to the initial model. More variance of observations of ruminal volatile fatty acid concentrations could be explained by considering ruminal microbes and CAZymes expressions in further study.

Type 2 diabetes mellitus (T2DM) is the most common metabolic disease in the world. Maintenance of glucose homeostasis depends on a complex interplay between the insulin responsiveness of skeletal muscle, liver, adipose tissue and glucose-stimulated insulin secretion by pancreatic beta cells. Defects in these organs are responsible for insulin resistance and progression to hyperglycemia. Understanding the integrated pathophysiology initiating the development of insulin resistance should extend our capacity to identify novel therapeutic targets for the prevention and/or treatment of T2DM. This biology remains incompletely characterized, in part, due to the interaction of multiple organ systems. The complexity of this biology is further underscored by the progressive changes in the systemic milieu including the onset of hyperinsulinemia, elevated circulating free fatty acids and triglycerides, hyperglycemia, and the activation of systemic immune system during the development of T2DM. In skeletal muscle, loss of mitochondrial function is evident in some insulin-resistant subjects years before they develop diabetes. Mitochondria are particularly important for skeletal muscle function, given the high oxidative demands imposed on this tissue by intermittent contraction. Moreover, muscle cells must maintain metabolic flexibility, defined as the ability to rapidly modulate substrate oxidation as a function of hormonal and energetic conditions. The molecular mechanisms that control mitochondrial number and function remain poorly understood, and only a few transcription factors or coactivators (e.g., PGC-1α, NRF1, Tfam) have been associated with this process. Notably, skeletal muscle differentiation and remodelling are also controlled at the epigenetic level, via transcriptional modulation of key genes in mitochondrial biogenesis and oxidative metabolism, involving enzymes, such as members of the histone deacetylase (HDAC) family, in particular those belonging to class I and class II, which modulate post-translational modifications on target proteins. The current knowledge on HDACs is that they function in general as transcriptional repressors, however their role in vivo is likely more complex. Less is known on the effects of HDACs modulators on energy metabolism, however a recent study reported that supplementation with sodium butyrate, a dietary component active as HDAC inhibitor, promotes energy expenditure and mitochondrial function in mice fed with a high fat diet212. Given the importance of skeletal muscle metabolism in insulin resistance/diabetes, and given the role of HDACs in skeletal muscle biology, it is reasonable to speculate that modulation of these enzymes would play a role in this pathology that deserves to be investigated more deeply. Based on the evidences that mitochondrial dysfunction is often associated to whole body metabolic dysregulation, aim of this study is to better understand the role of histone deacetylases in the regulation of mitochondrial biogenesis and in the modulation of all these mechanisms underlying the pathophisiology of insulin resistance. In C2C12 myotubes treated with pan and class selective HDAC inhibitors (HDACi), such as SAHA(pan-inhibitor), MS275 (Class I HDAC inhibitor) and MC1568 (Class II HDAC inhibitor), transcriptome analysis revealed an increase of OXPHOS genes and of genes encoding fatty acid catabolic enzymes, following treatment with pan or class I HDACi. Moreover, staining of myotubes treated with SAHA and MS275 showed an increase of mitochondrial density and activity, coupled with an increase in mitochondrial DNA content. In Db/Db obese and diabetic mice we observed that treatments with SAHA and MS275 reduce glycemia, triglycerides, plasma insulin land transaminases levels and improves glucose clearance and insulin sensitivity. In vivo metabolic study revealed an increase of oxygen consumption, a net decrease of the respiratory exchange ratio and an increased heat production, implying a more oxidative metabolism, in the MS275 treated group. In order to characterize the effects of HDACi in different tissues, we performed microarray analysis in skeletal muscles, liver, brown and white adipose tissues and histological analysis. In the skeletal muscle of mice treated with MS275, and with SAHA to a lesser degree, we observed a general increase in OXPHOS genes and in genes involved in lipid and glucose metabolism. These observations were also supported by the increased oxidative capacity highlighted by SDH staining in gastrocnemius sections. In brown fat we found an increased expression of brown adipocytes markers , such as PRDM16, CIDEA, UCP1, ELOVL3 and DIO2, and an induction of mitochondrial biogenesis, after MS275 administration. In parallel, adypocyte size appeared smaller respect to the adipocytes of the control group. In white adipose tissue, we observed an increase of adipocytes markers and, even in this case, an induction of mitochondrial biogenesis; adipocytes, beyond being smaller, also showed a reduced macrophages infiltration. Gene expression also revealed an increased expression of brown adipocytes markers, such as UCP1, also confirmed by immunohistochemistry assay, ADRB3, ELOVL3 and DIO2. Nevertheless, white adipocytes remained PRDM16 negative. Collectively, our results suggest that HDACs, and in particular Class I HDACs, play an unexpected role in energy metabolism, induce mitochondrial biogenesis in different tissues and may represent key regulators in diseases based on metabolic alterations.

El concepte de “pic” en les tendències de producció d’oli d’alta qualitat ja està ben establert. Això es reflecteix en la dinàmica cap a l’extracció de reserves de petroli poc convencionals i de menor qualitat que exigeixen majors fluxos de materials i energia a la via metabòlica. Al mateix temps, els països desenvolupats mantenen un compromís onerós però poc efectiu per a la substitució parcial o total de fonts fòssils per energia renovable. Aquest esforç requereix la generació d’un camp complet d’investigació complet, capaç d’aportar la informació requerida sobre la viabilitat i viabilitat biofísica d’aquestes solucions. Aquesta tesi proposa ampliar la comprensió dels problemes relacionats amb els sistemes energètics actuals. Ho fa analitzant en profunditat el rendiment de l’extracció de petroli com a font d’energia primària i la seva relació amb la societat en la producció de portadors d’energia, identificant les seves limitacions biofísiques en termes d’escassetat i pica. Aquesta tesi presenta metodologies comptables innovadores basades en aplicacions de l’esquema de comptabilitat MuSIASEM que facilita la comprensió de les implicacions biofísiques de l’extracció de petroli. Les aplicacions s’il·lustren en un anàlisi integrat a escala i integrada del sector del petroli equatorià, evitant la simplificació d’informació, pròpia del reduccionisme, trobada en estudis similars realitzats amb narracions econòmiques clàssiques. L’enfocament proposat integra la caracterització de diversos factors rellevants en una definició de criteris múltiples del rendiment d’un procés d’extracció de fonts d’energia primària. Identifica perfils d’entrades i sortides rellevants de fluxos i fons descrits mitjançant el concepte de “processadors estructurals” que es poden definir a diferents nivells d’anàlisi (és a dir, camp / bloc / àrea geogràfica). Les combinacions de processadors estructurals s’analitzen com complexos funcionals les característiques depenen de la qualitat del recurs explotat (és a dir, de producció pesada, mitjana i lleugera). D’aquesta manera, podem estudiar els canvis en el rendiment dels camps petroliers a causa del seu envelliment. Els canvis en la disponibilitat i la qualitat del petroli (i la necessitat d’aigua dolça) afecten els nivells de pressió ambiental en termes de capacitat de l’aigüera necessària: absorbir l’aigua contaminada i les emissions de GEH. Aquest enquadrament permet estudiar la relació actual i futura entre la font d’energia primària (extracció de petroli) disponible per a la societat i la seva capacitat per produir, distribuir i utilitzar productes intermedis per garantir els seus usos finals en els diferents sectors socioeconòmics. Per assolir aquesta tasca, el marc analític genera escenaris futurs que permeten la comprensió metabòlica de les activitats dels sistemes d’extracció d’oli. És a dir, permet la indentificació de les taxes metabòliques i les restriccions biofísiques tant en el costat de l’oferta (sistema d’extracció de petroli) com en el costat de la demanda (usos finals d’energia) a la societat equatoriana. A causa de la integració de l’anàlisi quantitativa a diferents dimensions i nivells d’anàlisi, els resultats d’aquest tipus d’anàlisis proporcionen informació destacada a les discussions sobre polítiques energètiques en l’àmbit tècnic, econòmic i ambiental.
El concepto de “peak oil” en las tendencias de producción de petróleo de alta calidad ahora está bien establecido. Esto se refleja en la dinámica hacia la extracción de reservas de petróleo no convencionales y de menor calidad que exigen mayores flujos de materiales y energía en la vía metabólica. Al mismo tiempo, los países desarrollados mantienen un compromiso oneroso pero ineficaz para la sustitución parcial y/o total de las fuentes fósiles por energías renovables. Este esfuerzo requiere la generación de un nuevo campo de investigación completo capaz de suministrar la información requerida sobre la viabilidad biofísica de estas soluciones. Esta tesis propone ampliar el entendimiento de los problemas que atañe a los sistemas energéticos actuales, analizando a profundidad el rendimiento de la extracción de petróleo como fuente primaria de energía y su relación con la sociedad en la producción de energy carrier para garantizar las funciones requeridas del sistema, identificando sus limitaciones biofísicas en términos de escasez y sumidero. Se presentan metodologías contables innovadoras basadas en aplicaciones del esquema contable MuSIASEM que facilitan la comprensión de las implicaciones biofísicas de la extracción de petróleo. Las aplicaciones se ilustran en un análisis multiescala e integrado del sector petrolero ecuatoriano, evitando la simplificación de la información, típica del reduccionismo, que se encuentra en estudios similares realizados con narrativas económicas clásicas. El enfoque propuesto integra la caracterización de varios factores relevantes en una definición de criterios múltiples del desempeño de un proceso de extracción de fuentes de energía primaria. Identifica perfiles de entradas y salidas para varios flujos y fondos utilizando el concepto de “procesadores estructurales” que se pueden definir en diferentes niveles de análisis, es decir, campo / bloque / área geográfica. Las combinaciones de procesadores estructurales se analizan como sistemas complejos funcionales cuyas características dependen de la calidad del recurso explotado, es decir, la producción de petróleo pesado, medio y ligero. De esta manera, se logra estudiar los cambios en el rendimiento de los campos petroleros debido a su envejecimiento. Los cambios en la disponibilidad y calidad del petróleo (y la necesidad de agua dulce) afectan los niveles de presión ambiental en términos de la capacidad de sumidero requerida para absorber el agua contaminada y las emisiones de GEI. Este marco permite estudiar la relación presente y futura entre la fuente primaria de energía (extracción de petróleo) disponible para una sociedad y su capacidad para producir, distribuir y usar productos intermedios para garantizar sus usos finales en los diversos sectores socioeconómicos. Para lograr esta tarea, el marco analítico genera escenarios futuros que permiten la comprensión metabólica de las actividades de los sistemas de extracción de petróleo. Es decir, permite la identificación de tasas metabólicas y restricciones biofísicas tanto en el lado de la oferta (sistema de extracción de petróleo) como en el lado de la demanda (usos finales de energía) en la sociedad ecuatoriana. Debido a la integración del análisis cuantitativo a través de diferentes dimensiones y niveles de análisis, los resultados de este tipo de análisis proporcionan información relevante para las discusiones sobre política energética en el ámbito técnico, económico y ambiental.
The concept of “peak” in the trends of production of high quality oil is now well established. This is reflected by the dynamics towards the extraction of unconventional and lower quality oil reserves that demand greater flows of materials and energy in the metabolic pathway. At the same time, developed countries maintain an onerous but ineffective commitment to the partial or total substitution of fossil sources with renewable energy. This effort requires the generation of a complete new field of research capable of supplying the require information over the biophysical feasibility and viability of these solutions. This thesis proposes to expand the understanding of the problems related to current energy systems. It does so by analyzing in depth the performance of oil extraction as a primary source of energy and its relationship with society in the production of energy carriers, identifying its biophysical limitations in terms of scarcity and sink. This thesis presents innovative accounting methodologies based on applications of the MuSIASEM accounting scheme facilitating the understanding of the biophysical implications of oil extraction. The applications are illustrated in a multi-scale and integrated analysis of the Ecuadorian oil sector, avoiding the simplification of information, typical of reductionism, found in similar studies carried out using classic economic narratives. The proposed approach integrates the characterization of several relevant factors into a multi-criteria definition of the performance of a process of extraction of primary energy sources. It identifies profiles of relevant inputs and outputs of flows and funds described using the concept of “structural processors” that can be defined across different levels of analysis – i.e. field / block / geographical area. Combinations of structural processors are analyzed as functional complexes whose characteristics depend on the quality of the exploited resource – i.e. heavy, medium, and light oil production. In this way, we can study changes in the performance of oil fields due to their aging. Changes in the availability and quality of oil (and the need for freshwater) do affect the levels of environmental pressure in terms of required sink capacity - to absorb polluted water and GHG emissions. This framing allows to study the present and future relation between the primary source of energy (oil extraction) available to a society and its ability to produce, distribute and use intermediate products to guarantee their end uses in the various socioeconomic sectors. To achieve this task the analytical framework generates future scenarios allowing the metabolic understanding of the activities of the oil extraction systems. That is, it allows the identification of metabolic rates and biophysical constraints both in the supply side (oil extraction system) and in the demand side (energy end uses) in the Ecuadorian society. Due to the integration of the quantitative analysis across different dimensions and levels of analysis, the results of this type of analysis provide salient information to the discussions of energy policy across the technical, economic and environmental domain.

The energy cost of performing 1 and 3 sets of strength-type (6-8 RM) and endurance-type (30-35 RM) bench press exercise was estimated by indirect calorimetry in 10 male college students. The total net energy cost of performing 3 sets of endurance-type resistive exercise (20.57 ± 1.86 kcal) was significantly (p-1) the strength-type exercise (2.35 ± 0.19) resulted in a significantly (p

La presente Tesis se centra en la importancia que tienen los flujos de energía para explicar la evolución de las economías en el tiempo, de menor a mayor organización, de menor a mayor complejidad. El desarrollo económico es un proceso, no un objetivo final para ninguna sociedad. Está relacionado con la evolució n de los sistemas humanos así como con su interacción con el entorno. Por lo tanto, se necesita un enfoque biofísico para poder entender mejor el proceso de desarrollo. Por ello esta tesis incluye una primera parte teórica y una parte empírica.
La primera parte consiste en 5 capítulos, principalmente de contenido teórico. Esta parte trata la relación entre la teoría económica, la teoría de los sistemas complejos y la termodinámica. El Capítulo 1 presenta de forma breve la relación entre complejidad, energía y economía, que son tratadas con más detalle en el resto de la tesis. El Capítulo 2 presenta el análisis energético bajo el enfoque de las diferentes escuelas de pensamiento económico. Se da particular énfasis al retorno al interés clásico en la producció n, tal y como recientemente surge entre aquellos que se llaman "economistas ecológicos". De hecho, uno de los mayores avances de éstos ha sido la incorporación de aspectos de la termodinámica al análisis económico. En particular, se habla de la importancia de la Segunda Ley de la Termodinámica y de su resultado más importante, la irreversibilidad de los procesos, que pone de manifiesto la importancia de la Historia. El Capítulo 3 trata de forma breve los temas de complejidad y autoorganización. El Capítulo 4 usa los conceptos desarrollados en capítulos anteriores para caracterizar a los sitemas humanos (p.e. economías) como sistemas abiertos lejos del equilibrio (termodinámico). Se presentan, a su vez, sus principales características, entre las que destacan su carácter jerárquico y su funcionamiento a través de ciclos auto-catalíticos que unen los diferentes niveles del sistema. La evolución de los sistemas económicos es el tema del Capítulo 5, tanto desde una perspectiva económica tradicional como desde una evolutiva, en la que 'la historia cuenta'. La explicación se basa en el análisis termodinámico, en donde el énfasis está en la relación entre la disipación de energía y el desarrollo. La segunda parte de la tesis consiste en 4 artículos publicados en revistas internacionales (capítulos 6 a 9), y un artículo que será enviado próximamente a una revista y que será presentado en una conferencia internacional en el verano de 2005. El primero de los artículos (Capítulo 6) es todavía de tipo teórico, tratando el tema del empirismo en economía ecológica para analizar la evolución de las sociedades. El Segundo (Capítulo 7) presenta la primera aplicación que hice en 2001 de la metodología MSIASM, para analizar la evolución de la economía española en el tiempo, y ayuda al lector a familiarizarse con la metodología.
El tercer artículo (Capítulo 8) vuelve a ser de carácter teórico, pero representa un avance y desarrollo teórico, y ayuda a entender las potencialidades que presenta la metodología utilizada, por medio de la inclusión de conceptos como el 'efecto mosaico' o el 'análisis de ciclos impredicativos', que ayudan a desarrollar mejor la narrativas a usar cuando analizamos temas de sustentabilidad. El cuarto artículo (Capítulo 9) presenta otra aplicación de MSIASM. En este caso se trata de entender las posibilidades que ofrece la metodología para ayudar a explicar trayectorias pasadas de desarrollo, así como para elaborar escenarios futuros de desarrollo. El quinto artículo (Capítulo 10) es la última aplicación, hasta el momento, de la misma metodología. El artículo representa un análisis del desarrollo económico de un actor principal en la economía mundial en la actualidad, China, para ofrecer respuestas diferentes a las típicas preguntas sobre la relación entre desarrollo y disipación de energía.
The present dissertation deals with the issue of the importance of energy flows in driving the evolution of economies on time, from less to more organised structures. From less to more complex systems. Economic development is a process, not a final goal to be achieved by any society. It is related to the economic evolution of human systems as well as with their interaction with the environment. Therefore, a biophysical analysis is needed to fully understand the process. The Thesis comprises both a theoretical and an empirical part. The first one consists of Chapters 1 to 5, which are mainly of theoretical content. This is the part dealing with the relationship between economic theory, complex systems theory and thermodynamics. Chapter 1 briefly presents the relationships between complexity, energy, and economics that are developed with more detail throughout the Thesis. Chapter 2 presents energy analysis under the framework of the different schools of economic thought. Stress is given to the revival of the classical interest in production, as we can find among those who call themselves "ecological economists". In fact, one of their major advances of this school has been the incorporation of the insights of thermodynamics to economic analysis. They have mainly used the Second Law of thermodynamics and its major result, the irreversibility of processes, and therefo re the importance of History. Chapter 3 deals with the issue of complexity and self-organisation. Chapter 4 uses the concepts developed in previous chapters to characterise human systems (i.e. economies) as open complex systems far from (thermodynamic) equilibrium. Their major characteristics are presented, focusing on their hierarchical structure and their functioning via autocatalytic loops that link each level of the system. The evolution of economic systems is analysed in Chapter 5, both from a traditional economic perspective and from an evolutionary one, in which 'history counts'. The explanation is based on thermodynamic analysis, in the sense than the relation between energy dissipation and development is the focus. The second part consists of 4 published papers in international refereed journals (Chapters 6 to 9) and one paper to be submitted soon after it is presented at an international conference in July 2005 (Chapter 10). The first of the papers (Chapter 6) is still theoretical, dealing with the issue of empiricism in the field of ecological economics to analyse the evolution of societies. The second one (Chapter 7) presents the first application I made back in 2001 of the MSIASM methodology, to analyse the evolution of the Spanish economy over time, and helps the reader to be familiar with the methodology. The third paper (Chapter 8) represents a step forward in the theoretical development of the approach used, and helps in fully understanding the potentialities of such methodology, by introducing key concepts such as 'mosaic effect' or 'impredicative loop analysis', that help developing better narratives for using when analysing sustainability. The fourth paper (Chapter 9) presents another application of MSIASM, this time for understanding its possibilities to help explain past trajectories of development and to help elaborate scenarios of future development. The fifth paper (Chapter 10) is the last application of the methodology. The paper represents an analysis of the economic development of a major actor nowadays, China, by applying MSIASM to try to get different answers to the usual questions regarding the relationship between economic development and energy dissipation.

The metabolic and biochemical factors involved in the regulation of fuel and pathway selection, at appropriate rates and times, during elevated metabolic demands remains to be resolved. Therefore, the purpose of this investigation was to examine the metabolic interrelationships involved in energy provision and its regulation during exercise at different intensities. Specifically, fuel selection and its control by adenine nucleotides and cytosolic redox and were investigated in red and white muscle of rainbow trout during various progressive intensities of exercise. The control of glycolysis was examined with respect to glycolytic enzyme disequilibrium. The effects of substrate limitations and end product accumulations were examined with regard to fatigue. Finally, the buffering capacity and various potential buffering constituents were investigated. It would appear that the energy turnovers required to perform the varied exercise intensities in this study were achieved by selecting the fiber type, fuel and pathway for optimizing ATP production rate versus substrate and proton accumulation. The purine nucleotide cycle was found to be operational within both fiber types. Fuel selection appeared to be intimately related to myofibrillar ATPase activation with free ADP acting as the metabolic signal to coordinate the phasing in of appropriate fuels/pathways at appropriate rates. HK, phos, PFK and PK were identified as regulatory enzymes in both fiber types. As well, the GPDH.PEK complex also appeared to exhibit regulation when glycogen was limiting and this regulation appeared to have been induced by a decreased ATP/ADP₊ ratio. The redox state of the NAD couple became more oxidized in both tissues when muscle glycogen was low. This finding was attributed to an induced shift in the equilibrium of LDH in the direction of NAD and lactate. The simultaneous ATP/ADP₊ induced disequilibrium of the PGK reaction would inhibit flux through the GPDH.PGK complex. Skeletal muscle buffering was found to be dominated by protein, inorganic phosphate and histidine related compounds. Thus, these metabolic and biochemical adjustments, allowed a coordinated integration of fiber type, fuel and pathway selection, to achieve the appropriate coupling of myofibrillar ATPase activity to ATP turnover, while minimizing substrate depletion and proton accumulations.
Science, Faculty of
Zoology, Department of
Graduate

In my thesis I investigate the ecology of maternal influences: the unique ability of mothers to influence, via genetic and non-genetic means, the phenotypic expression of their offspring. My research is presented as a series of standalone chapters that are introduced and then summarised by a general introduction (Chapter 1) and a general discussion (Chapter 6) respectively. One of the main components of an organism’s energy budget is its baseline level of energy metabolism. Individual differences in this cost of self-maintenance (termed in this chapter, resting metabolic rate, RMR) are substantial, but the causes and consequences of this variation are obscure. In Chapter 2, I review the published literature and show that maternal influences (along with other factors) can contribute substantially to variation in offspring RMR. Also, the RMR - fitness relationship appears to be modulated by environmental conditions (e.g. food supply), suggesting that the fitness consequences of a given RMR may be context-dependent. Thus, I propose that broad-scale variation in RMR might persist in natural populations, due to both spatial and temporal variation in environmental conditions and the trans-generational influence of mothers. To further investigate maternal influences on offspring energy metabolism, I measured the standard metabolic rate (SMR, a measure equivalent to RMR but used in reference to ectothermic animals) of juvenile brown trout (Salmo trutta) in response to intra-clutch manipulations of egg cortisol and testosterone (Chapter 3). Although, neither hormone affected offspring SMR (egg testosterone treatment resulted in a likely pharmacological dose), juveniles from cortisol-treated eggs were smaller and subordinate to individuals from control eggs. This indicates that variation in the amount of cortisol deposited in eggs by females, either among clutches or within them, is likely to affect juvenile performance. In a separate experiment (Chapter 4), I investigated if within-clutch differences in the phenotypes of juvenile brown trout were systematically related to the position where each individual developed during oogenesis. For a given egg size, siblings from dominant mothers were initially larger (but had a lower mass-corrected SMR) if they developed in the rear of the egg mass. However, heterogeneity in the size of siblings from different positions in the egg mass diminished in lower ranking females. Juvenile social status also varied according to egg mass position, although the direction of this effect depended on their age. Maternal influences on offspring are not only determined by conditions experienced by females immediately prior to reproduction. In Chapter 5, I investigated whether the juvenile growth rate and adult reproductive traits of female wild Atlantic salmon are related to the performance of their offspring in the wild. Investment in egg size was linked to both the juvenile and adult phenotypes of mothers. Even when controlling for egg size, the influence of these ‘past’ and ‘present’ maternal traits extended to offspring performance. Offspring growth was positively related to maternal investment in reproduction and the juvenile growth rate of each mother. The survival and biomass of offspring were also linked to adult reproductive traits but these relationships differed for mothers that had grown at either fast or slow rates as juveniles. Overall my thesis demonstrates that maternal influences are a substantial source of variation in offspring size, behaviour and physiology, both among and within clutches. My research also underlines the importance of maternal influences for offspring ecology and therefore maternal fitness.