Rozprawy doktorskie na temat „Nutritionally induced diseases”

Thesis (MTech (Biomedical Technology))--Cape Peninsula University of Technology, 2010
Consumption of sucrose with a meal containing oxidised and oxidisable lipids cause an increase in oxidative stress which is referred to as postprandial oxidative stress. The modulating effect on postprandial oxidative stress by an antioxidant-rich beverage, fermented rooibos (Aspalathus linearis) was compared to that of a commercial soft drink (soda). Both study beverages contained sucrose and were consumed with a standardised fat meal. The study consisted of two parts, a pilot study (Phase One) where participants consumed either a standardised fat meal with water (control group n = 5) or a standardised fat meal with a sucrose-containing commercial soda (treatment group n = 8) using a parallel design, and the experimental study (Phase Two) where participants (n = 14) consumed the standardised fat meal with the commercial soda (control group) or the rooibos beverage (treatment group) using a crossover design. Specific analytical techniques and methods for determination of plasma glucose, serum insulin, lipid profile, an inflammatory indicator (high sensitive C-reactive protein), plasma antioxidant capacity, whole blood redox status and plasma lipid oxidation biomarkers were used. Results from the pilot study indicated significantly (P<0.05) higher postprandial levels of glucose in the control group at 4 hr and 6hr postprandially. The inflammatory biomarker and triglyceride levels were significantly (P<0.05) elevated in both groups when compared to their respective baselines. Results also showed the total antioxidant capacity and total glutathione levels in the plasma of both groups to be significantly (P<0.05) lowered when compared to the baseline values. The level of lipid oxidation biomarkers in the plasma was significantly (P<0.05) higher at 2 hr, 4 hr and 6 hr post time intervals for thiobarbituric acid reactive substances and 4 hr post time interval for conjugated dienes in the participants consuming the standardised fat meal with soda when compared to the baseline value, while this was reflected only at 2 hr post time interval for thiobarbituric acid reactive substances, with the conjugated dienes levels being significantly (P<0.05) lowered at 6 hr post time interval in the control group. No differences were shown on inter group level for the pilot study. On inter group level, results from Phase Two showed significant (P<0.05) lower levels of plasma glucose at 6 hr post time interval in the treatment group when compared to the control group, with insulin levels being significantly (P<0.05) higher in the control group at 4 hr post time interval.

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2015.
It has recently been confirmed that people consuming 7+ portions of fruit and vegetables daily have a lower risk of mortality from any cause. With a fifth of the population of South Africa falling below the poverty line, it has been found that rural adults have a very low daily intake of fruit and vegetables; at the same time rural children are consuming a primarily maize-based diet. This low dietary diversity translates into a higher level of infectious diseases in children younger than five years. Interventions at national level included promoting the growing of underexploited traditional indigenous vegetables and fruits in home gardens, in the hope that rural households would help themselves in diversifying their cereal-based diet, while using crops they are accustomed to in their environment. Ten indigenous South African fruits found in the Western Cape were evaluated for their potential to make a positive contribution to the diet of rural communities and were compared with Blueberry and Cranberry, the North American ‘gold standards’. The following determinations were carried out on 12 samples: Total Phenolic Content, Total Flavanols and Total Monomeric Anthocyanins were analysed using the Folin-Ciocalteu, Mazza and pH Differential methods. Total Antioxidant Capacity was assessed using the Trolox Equivalent Antioxidant Capacity (TEAC), DPPH and Molybdenum Reduction assays. The Oxygen Radical Absorbance Capacity (ORACFL) was also determined. Iron Chelating Activity, one of the methods recommended to reflect other antioxidant mechanisms, was also investigated. The fruits possessing the highest concentration of Total Phenolic Content (Mazza) were Christmas berry, Bietou, Wild Olive and Wild Plum, at levels significantly higher than those of the two control berries, Blueberry and Cranberry. The fruits yielding the highest results for the TEAC assay were Wild Plum, Wild Olive, Tortoise berry, Christmas berry and Colpoon. The fruits giving the highest results for the DPPH assay were Wild Plum, Colpoon, Wild Olive, and Christmas berry. The fruits showing the highest results for the Molybdenum Reduction assay were Wild Olive, Wild Plum, Christmas berry, and Tortoise berry. The fruits yielding the highest results for the ORAC Total Antioxidant Capacity assay were Colpoon, Christmas berry, Wild Olive, Crossberry, Wild Plum, Waterberry followed by Blueberry and Cranberry. The results from the Iron Chelating Activity assay revealed a ranking of Christmas berry, Blueberry, followed by Num-num. On combining the results of eight assays, namely TPC (Mazza), TF, TA, TEAC, DPPH, TAC, TPC (FCR), ICA to give an Antioxidant Potency Composite Index, the fruits with the highest iv rankings were (1) Wild Plum, (2) Wild Olive, (3) Colpoon, and (4) Christmas berry. By comparison the northern hemisphere control berries ranked (5) Blueberry and (9) Cranberry. These findings show that by introducing even small servings of indigenous fruits into the diet, an important and inexpensive source of natural antioxidants could be accessed and the mean daily ORAC intake could thereby be boosted significantly by about 4,000 µmol Trolox Equivalents to bring the Total ORAC consumed to within optimum levels (6,000 µmol Trolox Equivalents and above). These bioactive plant compounds have the potential to deliver immense benefits to health to impoverished South African adults, as well as rural children, well beyond basic nutrition.

[Truncated abstract] This thesis examines the potential role of dietary intake in the development of two common conditions affecting the prostate gland; prostate cancer and benign prostatic hyperplasia (BPH). Diet is of interest as a potential risk factor for prostate cancer because of geographical variations in prostate cancer incidence and increased prostate cancer risks associated with migration from Asian to western countries. Some geographical variation has been suggested for BPH, but this is less certain. However, both prostate cancer and BPH have potential links with diet through their positive associations with sex hormone levels, metabolic syndrome, increased insulin levels and chronic inflammation. In addition, zinc is an essential dietary micronutrient required for semen production in the prostate gland. The original work for this thesis is presented in six manuscripts of which, four have been published in peer-reviewed journals (at the time of thesis completion). BPH investigated in this thesis is defined as surgically-treated BPH. The following hypotheses were investigated. Regarding foods, nutrients and the risk of prostate cancer and BPH: 1. Increasing intakes of fruits, vegetables and zinc are inversely associated with the risk of prostate cancer and BPH 2. Increasing intakes of total fat and calcium are positively associated with the risk of prostate cancer and BPH. 3. Dietary patterns characterised by high meat, processed meat, calcium and fat content are positively associated with the risk of prostate cancer and BPH. 4. Dietary patterns characterised by high fruit and vegetable and low meat content are inversely associated with the risk of prostate cancer and BPH. v Regarding methodological issues related to the study of diet-disease relationships: 5. Dietary patterns (overall diet) elicited from principal components analysis yield stronger diet-disease associations than when studying isolated nutrients. 6. Remotely recalled dietary intake is reliable enough to be used in studies of chronic disease with long latency periods, such as prostate cancer and BPH. Methods: Data from two studies was used to address the hypotheses above. ... Based on the literature reviewed and the original work for this thesis, the most important dietary risk factors for prostate cancer and BPH appear to be those common to western style diets, i.e. diets high in red meat, processed meat, refined grains, dairy products, and low in fruit and vegetables. This type of diet is likely to result in marginal intakes of antioxidants and fibre, excess intakes of fat and possibly, moderate intakes of carcinogens associated with processed meat and meat cooked at high temperatures. These dietary factors have been linked with biomarkers of inflammation, and they support the hypotheses that chronic inflammation is involved in the development of both prostate cancer and BPH. In addition, this work builds on evidence that zinc is an important factor in prostate health. There is scope for more investigation into the reliability of dietary patterns and the use of nutrient patterns as an alternative to focussing on single food components. Further studies on the reliability of remote dietary intake would also be useful. Because of the latency of chronic disease, it can be theorised that remote dietary recall may uncover more robust diet-disease relationships.

The main aim of this thesis was to examine the hypothesis that the A/J strain variant of H55N substitution affects citrate synthase (CS) enzyme activity and metabolic health in mice fed a high fat diet (HFD). C57BL/6J (B6) mice and congenic B6.A-(rs3676616-D10Utsw1)/KjnB6 (B6.A) mice, a strain which carries the A/J allele of Cs on the B6 strain background, were fed a HFD (45% kcal from fat) for 12 weeks. CS activity, but not that of ß-hydroxyacyl-coenzyme dehydrogenase was lower in the gastrocnemius muscle of B6.A mice compared to B6 mice (P< 0.001). During HFD feeding the glucose tolerance of mice decreased progressively and to a greater extent in B6.A females compared to B6 females, with males showing a similar trend. Interestingly, after 12 weeks of HFD feeding only B6.A males showed increases (P< 0.05) in their resting metabolic rate; moreover; core body temperature were also increased (P< 0.05) for congenic B6.A of both sexes by the end of the study. However, body weight and fat gain did not differ between B6.A and B6 mice. The second aim of the thesis was to test the hypothesis that low CS activity promotes palmitate-induced lipotoxicity in muscle cells. After 18 hours of incubation in 0.8 mM palmitate, C2C12 muscle cells with a ~50% reduction in CS activity showed low (P< 0.001) viability, increased (P< 0.001) levels of cleaved Caspase-3, high levels of AMP-activated protein kinase and acetyl-CoA carboxylase phosphorylation (P< 0.05), low levels of protein kinase B phosphorylation, high mitogen-activated protein kinases activation (P< 0.001) compared to the control shRNA cells. This was coupled with higher levels of mitochondrial proteins (P< 0.05), which are involved in oxidative phosphorylation. C2C12 cells with reduced CS activity also showed high reactive oxygen species production (P< 0.05), low intracellular ATP levels (P< 0.05), and lower basal mitochondrial respiration (P< 0.001). In summary, the A/J strain variant of H55N is associated with low CS enzyme activity and impaired metabolic health when fed HFD. Palmitate has a lipotoxic effect on Cs shRNA transfected cells and can lead to cell death.

Thesis (MNutr (Human Nutrition))--University of Stellenbosch, 2005.
A diet high in fat results in dietary-related diseases, which have reached epidemic proportions in South Africa. Nutritional labelling has the potential to alter consumers’ knowledge of attitude and behaviour towards their fat intake. The purpose of the study was to investigate the effects of nutritional labelling on the population’s fat-intake through a systematic literature review. Electronic databases, reference lists of relevant studies and the Internet were searched, to identify studies that could help to answer the problem statement. Relevant citations were independently identified by two investigators based on the established inclusion-criteria. After this the full text of the selected citations were obtained and filtered independently by each investigator based on the inclusion- and exclusion criteria. The characteristics of each study was recorded in specially developed data extraction forms by the investigator herself and was checked by a second investigator. The primary objective of the study was to investigate nutritional labelling on food packaging. Two other forms of labelling were included to gain a more concise perception of consumers’ knowledge and practices regarding information on fat. These other forms were point-of-sale labelling (in supermarkets, in restaurants, by vending machines) and experimental labelling (labels spesifically designed to indicate the fat-content of a food item). A total of 59 relevant studies were included based on the inclusion-criteria. Although only a few studies assessed the effect of labelling on diet, there was evidence that the use of labels resulted in lower fat intake. Women older than 35 years with higher education levels, who used nutritional supplements, and who were in the maintenance stage of change to a lower fat diet, and who believed in the importance of nutrition, were between 50% to 80% higher users of information about fat than their counterparts. Fat is the food component which was most looked at on the food label (50% to 80%). Small changes in fat intake occured due to point-of-sale labelling, but labelling programmes which combined labelling with additional information on fat (e.g. pamphlets), increased visibility and nutrition education programmes, were more successful. People generally perceived products lower in fat as less pleasant, but sensory judgement of the products labelled with a low fat content were related to a person’s beliefs and concerns towards fat. Nutritional labelling can be an effective measure, which can be used to reduce the population’s fat intake; however, more research is needed to assess the effect of labelling on fat content of their diet. Regulations and education is needed to enhance the consumer’s trust in and capability in the use of labelling to make better food choices and to alter their diet. The success of labelling is dependant on a well-educated and motivated population, as well as the necessary information in a format which is understandable to the consumer.

Thesis (Mnutr)--Stellenbosch University,2003.
ENGLISH ABSTRACT: Most of the risk factors for coronary heart disease (CHD) such as hypertension, dyslipidaemia, smoking, non-insulin dependent diabetes mellitus (NIDDM), obesity, physical inactivity and heredity are common in South African populations, with Indians ranking among those with the highest prevalence in the country. Little published literature is available on eating patterns in pre-school children in the Indian population. Therefore, this study a ims to assess the nutritional status of a group of Indian pre-school children in Howick West (a small suburb in the Kwa-Zulu Natal Midlands). Methods: This was a cross-sectional study of 50 Indian pre-school children between the ages of 1-5 years, randomly selected from a total of 632 available Indian households in Howick West. Written, informed consent was obtained from the mother/caregiver of each child that participated in the study. Standardized and validated 24-hour-recall (24-H-R) and quantitative food frequency questionnaires (QFFQ), used in the National Food Consumption Survey (NFCS) of 1999, were adapted and used to assess habitual intake and eating patterns of the 50 Indian pre-school children. Height and weight measurements using standardized methodology were used to assess the anthropometric status of the children. Results: The prevalence of underweight was 14%. Stunting affected only 8% of the children, and 2% were at risk of overweight. The mean energy intakes of the children were above that recommended for age. A high fat intake was observed, with total fat contributing 42% to the daily total energy (TE) intake. The contributions of total carbohydrate and protein to TE intake were 45% and 10%, respectively. Low mean intakes of the following micronutrients were observed (less than 67% of the RDA): Calcium (22% of the children), Vitamin D (90%), Zinc (56%) and Iodine (90%), respectively. Based on the 24-H-R, the intakes of the remaining micronutrients were either above or equivalent to that recommended for age when compared to the 1989 RDAs. Conclusions: Despite a relatively high prevalence of underweight compared to overweight in these preschoolers, dietary analysis has indicated adequate dietary intakes in terms of total energy recommended for the age groups studied. However, total fat intake which represented 42% of TE, was high, with saturated fat (SF) contributing 15% to TE intake. This finding is cause for concern as excessive consumption of dietary fat has been implicated in the aetiology of CVD, obesity and some forms of cancer, and CHD is one of the main causes of morbidity and mortality in South Africa, especially among the Indian segment of the population.
AFRIKAANSE OPSOMMING: Meeste van die risikofaktore vir koronêre hartsiektes (KHS) soos hipertensie, dislipidemie, rook, nie-insulien afhanklike diabetes (NIADM), vetsug, fisiese onaktiwiteit en oorerflikheid, kom algemeen onder Suid-Afrikaanse bevolkingsgroepe voor, met Indiërs onder dié met die hoogste voorkoms in die land. Min gepubliseerde inligting is beskikbaar oor die eetgewoontes van voorskoolse kinders onder die Indiër bevolking. Die doel van hierdie studie was dus 0 m die voedingstatus van 'n groep Indiër voorskoolse kinders in Howick Wes ('n klein voorstad in die Kwa-Zulu Natal Middellande) te bepaal. Metodes: Dit was 'n dwarssnit studie van 50 voorskoolse Indiër kinders tussen die ouderdomme van 1-5 jaar, ewekansig geselekteer uit 632 beskikbare Indiër huishoudings in Howick Wes. Geskrewe en ingeligte toestemming is ontvang van die moeder/versorger van elke kind wat aan die studie deelgeneem het. Gestandaardiseerde en gevalideerde 24-uur herroep (24-H-R) en voedsel frekwensie vraelyste (QFFQ) soos gebruik in die Nasionale Voedsel Inname Studie (NFCS) van 1999, is aangepas en gebruik om gewoontelike inname en eetgewoontes van die 50 Indiër voorskoolse kinders te bepaal. Lengte en gewig is m.b.v. standaad tegnieke bepaal om die antropometriese status van die kinders te evalueer. Resultate: Die voorkoms van ondergewig was 14%. Dwerggroei het slegs 8% van die kinders geaffekteer en 2% het 'n risiko vir oorgewig getoon. Die gemiddelde energie inname van die kinders was hoër as wat aanbeveel word vir hierdie ouderdomsgroep. 'n Hoë vetinname is gevind, met 'n totale vet bydrae van 42% tot die daaglikse totale energie (TE) inname. Die bydrae van koolhidrate en proteïen tot TE was 45% en 10% respektiewelik. Lae gemiddelde innames van die volgende mikrovoedingstowwe is gevind (minder as 67% van die RDA): kalsium (22% van die kinders), vitamien D (90%), sink (56%) en jodium (90%), respektiewelik. Gebasseer op die 24-H-R, was die inname van die oorblywende mikrovoedingstowwe óf hoër óf gelyk aan wat aanbeveel word vir die betrokke ouderdomsgroep wanneer vergelyk word met die 1989 RDA. Gevolgtrekkings: Ten spyte van 'n relatiewe hoë voorkoms van ondergewig in vergelyking met oorgewig in hierdie voorskoolse kinders, was dieetinname voldoende in terme van totale aanbevole energie vir die ouderdomsgroep. Totale vetinname, wat 42% van TE uitgemaak het, was egter hoog en versadigde vette het 15% van TE bedra. Hierdie verskynsel is 'n rede tot kommer aangesien oormatige vetinname reeds geïmpliseer is in die etiologie van KHS, vetsug en sommige vorms van kanker, en KHS is een van die belangrikste oorsake van morbiditeit en mortaliteit in Suid Afrika, veralonder die Indiër bevolking.

Thesis (MTech (Biomedical Technology))--Cape Peninsula University of Technology, 2006
Research has shown that the activation of the NO-cGMP pathway leads to myocardial protection from oxidative stress conditions, such as ischaemia and reperfusion. Few of these studies have however combined diet induced oxidative stress with ischaemia/reperfusion injury. Although little is known about the effects of supplements such as red palm oil (RPO) on the NO-cGMP pathway, research has shown that dietary RPO-supplementation improved reperfusion aortic output recovery through mechanisms that may include activation of the NO-cGMP- and inhibition of the cAMP pathway. RPO is an antioxidant-rich oil containing ~carotene and Vitamin E (tocopherols and tocotrienols). The aims of this study were to determine: 1) whether RPO-supplementation of an oxidative risk induced diet (ORD) and a high saturated fat diet (HFD) offers protection against ischaemia/reperfusion injury in the isolated perfused rat heart and 2) the possible mechanisms for this protection. Male Wistar rats were randomly divided into four groups for a period of 14 weeks according to the dietary supplementation they received. The control groups received either an oxidative risk induced diet (ORD) or a high saturated fat diet (HFD), while the experimental groups received an ORD supplemented with RPO (ORD+RPO) or a HFD supplemented with RPO (HFD+RPO).

Infertility is one of the major complications of obesity. Studies have shown that administration of leptin modulated the expression of Β-catenin in the ovary and reversed obesity-induced infertility in rats. Coenzyme Q10 (CoQ10), an antioxidant, supplies the energy used for ovulation, oocyte and embryo development and prevents DNA damage that causes infertility. We hypothesized that leptin when combined with CoQ10 could greatly improve fertility. Twenty-one female Sprague-Dawley rats were used in this study and divided into five treatments groups. Group I rats was fed rat chow diet (RCD) while groups II to V were fed High-fat diet (HFD) for 14 weeks to induce infertility. Group 1 RCD and group II HFD control rats received 1 ml of saline intraperitoneally (i.p.) twice daily for 2 days, group III HFD rats received 1 ml of 100 µg of leptin i.p. twice daily for 2 days, group IV HFD rats received 10 mg/kg of CoQ10 i.p. for 2 weeks plus saline twice daily for 2 days. Group V HFD rats received 1 ml of 100 µg of leptin i.p. twice daily for 2 days plus 10 mg/kg of CoQ1o i.p. for 2 weeks. Estrous cycle was checked daily and food intake and body weight measured twice weekly before and after treatments. Fourteen days post treatment, all the animals were sacrificed. The blood and tissues were collected for analysis. The results show a significant decrease in food intake and body weight and regular estrous cycle restored in groups III and V rats. There was significant (p < 0.05) increase in spleen weight in groups IV and V. FSH level increased significantly (p < 0.05) in the leptin plus CoQ10 treated group while CoQ10 level was increased significantly (p < 0.05) in the leptin-treated group. Β-catenin expression was decreased in group IV and V, suggesting that Β-catenin expression may be downregulated by COQ10 administration. These results indicate that synergistic action of leptin and CoQ10 could delay the onset of obesity-induced infertility exhibited by the reduction of food intake and body weight. In conclusion, combinations of CoQ10 with leptin can improve fertility in obese infertile female rats and could provide a novel therapeutic strategy for the treatment of female infertility.

NOD mice model human type 1 diabetes and have been used to investigate tolerance induction protocols for islet transplantation in a setting of autoimmunity. Costimulation blockade-based tolerance protocols that induce prolonged skin and permanent islet allograft survival in non-autoimmune mice have failed in NOD mice. To investigate the underlying mechanisms, we generated NOD hematopoietic chimeras. We were able to show that dendritic cell maturation defects seen in NOD mice are partially corrected in mixed hematopoietic chimeras. Furthermore, skin allograft survival was dependent upon the phenotype of the bone marrow donor, demonstrating that in the NOD the resistance to tolerance induction resides in the hematopoietic compartment. In addition, we studied congenic NOD mice bearing insulin dependent diabetes (Idd) loci that reduce diabetes incidence. The incidence of diabetes is reduced in NOD.B6 Idd3 mice, and virtually absent in NOD.B6 Idd3Idd5 mice. Islet allograft survival in NOD.B6 Idd3 mice is prolonged as compared to NOD mice, and in NOD.B6 Idd3Idd5 mice islet allograft survival is similar to that achieved in C57BL/6 mice. Alloreactive CD8 T cell depletion in NOD mice treated with costimulation blockade is impaired, but is partially restored in NOD.B6 Idd3 mice, and completely restored in NOD.B6 Idd3Idd5 mice. Idd3 results from variations in Il2 gene transcription. We hypothesized insufficient levels of IL-2 in NOD mice contributes to impaired deletion of alloreactive CD8 T cells and shortened islet allograft survival. We observed using synchimeric mice that co-administration of exogenous IL-2 to NOD mice treated with costimulation blockade led to deletion of alloreactive CD8 T cells comparable to that in C57BL/6 mice and prolonged islet allograft survival. However, some Idd loci impaired the induction of transplantation tolerance. These data suggest that Idd loci can facilitate or impair induction of transplantation tolerance by costimulation blockade, and that Idd3 (IL-2) is critical component in this process.

Several viral infections have been associated with human type 1 diabetes (T1D), although it has proven difficult to unequivocally establish them as causative agents. In rodent models, however, viruses have definitely been established to cause T1D. The treatment of weanling BBDR rats with the combination of a TLR3 ligand, pIC, and an ssDNA parvovirus, KRV, precipitates T1D in nearly 100% of rats within a short, predictable timeframe. In this dissertation, we utilized the BBDR rat model to (1) identify early serum biomarkers that could predict T1D precipitated by viral induction and (2) test the efficacy of leptin, a therapeutic agent, which may have the ability to prevent diabetes onset, reverse new onset diabetes and prevent autoimmune recurrence of diabetes in rats transplanted with syngeneic islet grafts. Identification of biomarkers has long served as an invaluable tool for disease prediction. In BBDR rats, we identified an acute phase response protein, haptoglobin, as a potential biomarker for pIC + KRV induced T1D using the global proteomic profiling techniques, 2D gel analysis and iTRAQ. Upon validating this biomarker, we determined that haptoglobin was sensitive in predicting T1D in the pIC + KRV model, in which nearly 100% of the rats become diabetic, but not in models where diabetes expression was variable (KRV only or RCMV only models). However, analysis of the serum kinetics of haptoglobin and its functional capacity in the blood has given us insights into the potential role of early phase reactants in modulating virally mediated T1D. An alternative means of regulating T1D pathogenesis is through leptin. Leptin is a hormone with pleotropic roles in the body, particularly affecting energy metabolism and immune regulation. These characteristics make leptin an intriguing candidate for therapeutic testing in T1D models. Our studies have determined that high doses of leptin delivered via an adenovirus (AdLeptin) or alzet pump delivery system can prevent diabetes in > 90% of rats treated with pIC + KRV. We further showed that serum hyperleptinemia was associated with decreased body weight, decreased non-fasting serum insulin levels and lack of islet insulitis in pIC + KRV treated rats pretreated with AdLeptin compared with those pretreated with PBS. We discovered that hyperleptinemia induced a profound decrease in splenic weight and splenic cellularity, including reductions in CD4+ and CD8+ T cells, DC/MACs and B cells. These findings indicate a potential mechanism whereby hyperleptinemia protects rats from virally induced T1D through the promotion of peripheral immunosuppression. Among pIC + KRV treated rats, we have also found that leptin therapy can reverse hyperglycemia in a subset of new onset diabetics for up to 20 days. In the absence of exogenous insulin, leptin treatment of new onset diabetics prevented the rapid weight loss associated with osmotic diuresis, as well as the ketosis observed in vehicle treated diabetic rats. Overall, these findings point to the therapeutic value of leptin in maintaining glycemic control and preventing ketosis in an insulin deficient state, in the absence of exogenous insulin therapy. Additionally, we have also determined that AdLeptin treatment can prolong the survival of syngeneic islets transplanted into diabetic BBDR rats for up to 50 days post transplant. Although hyperleptinemia generated by AdLeptin was unable to prevent insulitis into islet grafts, this insulitis did not appear to be destructive as islet grafts continued to stain positively for insulin when compared with control rats whose grafts succumbed to recurrent autoimmunity. In the various therapeutic settings in which we have tested leptin treatment, we have found this hormone to have significant beneficial effects. These findings merit further evaluation of leptin as a therapeutic agent in human T1D.

Aging is associated with a loss of proliferation of the insulin-secreting beta cell, a possible contributing factor to the greatly increased rate of type-2 diabetes in the elderly. A landmark study from our lab previously illustrated that mild endoplasmic reticulum (ER) stress drives beta cell proliferation specifically through ATF6α, one arm of the tripartite Unfolded Protein Response (UPR). It is unknown if old beta cells differ from young beta cells in UPR signaling or proliferative response to ER stress or ATF6α activation. To investigate, young and old mouse islets were cultured ex vivo in high glucose, and beta cell proliferation was quantified by BrdU incorporation after treatment with low dose thapsigargin or activation of overexpressed ATF6α. In addition, levels of UPR signaling were compared by semi-quantitative Xbp1 splicing assay. Interestingly, although old beta cells displayed reduced proliferation in glucose compared to young beta cells, their proliferative response to low-dose thapsigargin and ATF6α activation were nearly identical, and no difference was found in Xbp1 splicing under high glucose or high ER stress conditions. These results suggest that the aged mouse beta cell does not have impaired UPR-responsive proliferation or aberrant UPR signaling when cultured ex vivo

The NOD mouse is a widely studied model of type 1 diabetes. The loss of self-tolerance leading to autoimmune diabetes in NOD mice involves at least 27 genetic loci. Curing type I diabetes in mice and humans by islet transplantation requires overcoming both allorejection and recurrent autoimmunity. This has been achieved with systemic immunosuppression, but tolerance induction would be preferable. In addition to their genetic defects in self-tolerance, NOD mice resist peripheral transplantation tolerance induced by costimulation blockade using donor-specific transfusion and anti-CDl54 antibody. Failure has been attributed to the underlying autoimmunity, assuming that autoimmunity and resistance to transplantation tolerance have a common basis. Hypothesizing that these two abnormalities might be related, we investigated whether they had a common genetic basis. Diabetes-resistant NOD and C57BL/6 stocks congenic for various reciprocally introduced Idd loci were assessed for their ability to be tolerized. Surprisingly, in NOD congenic mice that are almost completely protected from diabetes, costimulation blockade failed to prolong skin allograft survival. In reciprocal C57BL/6 congenic mice with NOD-derived Idd loci, skin allograft survival was readily prolonged by costimulation blockade. Unexpectedly, we observed that (NOD x C57BL/6)F1 mice, which have no diabetes, nonetheless resist induction of tolerance to skin allografts. Further analyses revealed that the F1 mice shared the dendritic cell maturation defects and abnormal CD4+ T cell responses of the NOD but had lost its defects in macrophage maturation and NK cell activity. Finally, using a genome wide scan approach, we have identified four suggestive markers in the mouse genome that control the survival of skin allografts following DST and anti-CD154 mAb therapy. We suggest that mechanisms controlling autoimmunity and transplantation tolerance in NOD mice are not completely overlapping and are potentially distinct, or that the genetic threshold for normalizing the transplantation tolerance defect is higher than that for preventing autoimmune diabetes. We conclude that resistance to allograft tolerance induction in the NOD mouse is not a direct consequence of overt autoimmunity and that autoimmunity and resistance to costimulation blockade-induced transplantation tolerance phenotypes in NOD mice are not under identical genetic control.

Diabetes mellitus is a group of metabolic disorders characterized by hyperglycemia. The pathogenesis of these diseases involves β-cell dysfunction and death. The primary function of β-cells is to tightly regulate the secretion, production, and storage of insulin in response to blood glucose levels. In order to manage insulin biosynthesis, β-cells have an elaborate endoplasmic reticulum (ER). The ER is an essential organelle for the proper processing and folding of proteins such as proinsulin. Proteins fold properly when the ER protein load balances with the ER folding capacity that handles this load. Disruption of this ER homeostasis by genetic and environmental stimuli leads to an accumulation of misfolded and unfolded proteins, a condition known as ER stress. Upon ER stress, the unfolded protein response (UPR) is activated. The UPR is a signaling network that aims to alleviate ER stress and restore ER homeostasis promoting cell survival. Hence, the UPR allows β-cells to handle the physiological fluctuations of insulin demand. However upon severe unresolvable ER stress conditions such as during diabetes progression, the UPR switches to pathological outputs leading to β-cell dysfunction and apoptosis. Severe ER stress may also trigger inflammation and accumulating evidence suggests that inflammation also contributes to β-cell failure, but the mechanisms remain elusive. In this dissertation, we demonstrate that thioredoxin interacting protein (TXNIP) mediates ER stress induced β-cell inflammation and apoptosis. During a DNA microarray analysis to identify novel survival and death components of the UPR, we identified TXNIP as an interesting proapoptotic candidate as it has been linked to glucotoxicity in β-cells. During our detailed investigation, we discovered that TXNIP is selectively expressed in β-cells of the pancreas and is strongly induced by ER stress through the IRE1α and PERK-eIF2α arms of the UPR and specifically its transcription is regulated by activating transcription factor 5 (ATF5) and carbohydrate response element binding protein (ChREBP) transcription factors. As TXNIP has been shown to activate the Nod-like receptor protein 3 (NLRP3) inflammasome leading to the production of the inflammatory cytokine interleukin-1β (IL- 1β), we hypothesized that perhaps TXNIP has a role in IL-1β production under ER stress. We show that ER stress can induce IL-1β production and that IL-1β is capable of binding to IL-1 type 1 receptor (IL-1R1) on the surface of β-cells stimulating its own expression. More importantly, we demonstrate that TXNIP does indeed play a role in ER stress mediated IL-1β production through the NLRP3 inflammasome. Furthermore, we also confirmed that TXNIP is a mediator of β-cell apoptosis under ER stress partially through IL-1β signaling. Collectively, we provide significant novel findings that TXNIP is a component of the UPR, mediates IL-1β production and autostimulation, and induces cell death under ER stress in β-cells. It is becoming clear that TXNIP has a role in the pathogenesis of diabetes and is a link between ER stress, oxidative stress and inflammation. Understanding the molecular mechanisms involved in TXNIP expression, activity, and function as we do here will shed light on potential therapeutic strategies to tackle diabetes.

Part 1 of this thesis is a descriptive epidemiological study of mortality from coronary heart disease (CHO) among men in Tasmania. Part 2 is an analytical epidemiological study which uses a case-control design to examine the relationship between dietary fatty acids and sudden unexpected cardiac death in Tasmanian men. Part 1: Mortality from CHO in Tasmanian men. In common with several Western industrialised countries, mortality from CHO has declined by more than 50% in Australia over the past 20 years. CHO now accounts for approximately 25% of all deaths. Analysis of data provided by the Australian Bureau of Statistics (ABS) showed that most of the decline in mortality from all causes in each of the six Australian States over the period 1972-1988 is due to a decline in mortality from CHO. In the island State of Tasmania, the rate of decline in mortality from all causes in both sexes was significantly less (p<0.01) than in the mainland Australian States, and the discrepancy was due to a slower rate of fall in mortality from CHO (p<0.01 ). It seems unlikely that these differences in mortality from CHO are due to artefact, as they were matched by parallel trends in mortality rates from all causes. Furthermore, in Tasmania, a cause of death coded to ICD 9 rubrics 410-414 (CHO) was found to have a sensitivity of 94% and a positive predictive value of 90% for fatal definite myocardial infarction or possible coronary death as defined by the World Health Organisation. Detailed analysis of mortality data for men over the period 1986 to 1989 for the three health regions of Tasmania revealed that the two northern regions of Tasmania which represent approximately 52% of the total population, accounted for 98% of the excess mortality from CHO in Tasmania compared with the national rate. Between 1986 and 1989, the Tasmanian rate for mortality from CHO was 17% higher than the Australian rate (p<0.001 ). The rate in the North-West Region of Tasmania was 38% higher than the national figure (p<0.001 ), while the rate for the Northern Region was 26% higher (p<0.001 ). The difference between mortality from CHO in the Southern Region of Tasmania and the national rate was not significant (p=0.99). There was evidence that the pattern of consumption of dietary fat in Tasmania differed from that for the rest of Australia, but the relevant data for a regional comparison of dietary habits within Tasmania were not available. Part 2: Sudden unexpected cardiac death and dietary fatty acids. A population based case-control study was undertaken to test the hypothesis that the ratio of polyunsaturated to saturated fatty acids in the diet is inversely related to the incidence of sudden unexpected cardiac death (SUCO), that is, cardiac death occurring within one hour of onset of symptoms in individuals with no previous history of CHO. Male cases of SUCO from between 1987 and 1989 (n=102) were matched by age and sex to 102 cases of first-ever acute myocardial infarction (AMI) and 204 controls drawn from electoral rolls. Data on risk factors for CHO, including a food frequency questionnaire, were collected via a structured interview conducted with the spouses of cases and controls. Forward step-wise multiple conditional logistic regression was used to examine the effect on risk of SUCO of various aspects of dietary intake of fat, the variables usually being treated as quartiles. Cigarette smoking, leisure-time physical activity, current treatment for hypertension, socio-economic status, consumption of alcohol, family history (FH) of CHO, relative body mass and history of diabetes mellitus were considered as potential confounding variables. When community controls were compared with cases of SUCD, significant odds ratios were found for the following risk factors: current smoking (0R=3.6), family history of CHO (0R=2.5), history of diabetes mellitus (0R=3.8), history of treated hypertension (0R=1.9) and dietary cholesterol greater than 21 O mg per day (0R=2.9). When community controls were compared with cases of first-ever AMI, significant odds ratios were found for family history of CHO (0R=7.1 ), current smoking (0R=6.4), some regular leisure-time physical exercise (0R=3.7) and dietary mono-unsaturated fat (0R=4.0-5.8). The present study found that dietary P:S ratio was not inversely related to the incidence of SUCD.

There is concern that humans consume sodium, mostly as salt (sodium chloride, NaCl) at levels that produce significant medical risks. The current review gives an appraisal of psychologically relevant research into concerns in relation to sodium intake. Determinants of food choice, including sensory preferences, familiarity and exposure, customary level of sodium in daily diet, attitudes, and personality traits (including food neophobia) are explored, and their impact on dietary sodium is also discussed. In addition, strategies for reducing salt levels are discussed, including a reduction in salt content in food products, and the use of alternative tastants to salt. The use of glutamate salts such as monosodium glutamate (MSG) and calcium diglutamate (CDG) as alternative tastants is discussed. Finally, there is a summary of the methodological issues of the research reviewed and recommendations for future research into the area of alternative tastants is provided.

Introduction: Gastric cancer (GC) is ranked as the second most common fatal malignancy worldwide. Although Helicobacter pylori is recognized as a major predisposing factor for non-cardia GC, infection alone is not sufficient to cause cancer. This thesis aimed to determine the variation in host genetic polymorphisms in subjects from Malaysia and Singapore and to examine the role of H. pylori infection, host genetic factors and dietary factors in the etiology of non-cardia GC in Chinese subjects resident in Malaysia. Methods: Functional dyspepsia (FD) controls from three ethnic groups in Malaysia, Chinese (123), Indian (110) and Malay (84) and Singaporean Chinese (127) plus Malaysian Chinese gastric cancer cases (55)were examined. Polymorphisms in IL-1B-511, IL-1RN, IL-10 cluster, TNFA-308 and TLR5+1174 were determined by PCR-RFLP or PCR; H. pylori status by serology, dietary intake by questionnaire and gastric IL-1b levels by real time PCR. Results: 1) Significant differences existed in the frequency of all polymorphisms, except IL-1B-1473 and TNFA-308, in the three Malaysian ethnic groups and in the IL-1B-511 polymorphism in Malaysian and Singaporean Chinese FD 2) Globally, two distinct patterns of IL-1B-511, IL-1RN, IL-10-1082, IL-10-592 and TNFA-308 exist, Western and East-Asian 3) In Malaysian Malays, the IL-10 ATA haplotype was associated with H. pylori susceptibility 4) In Malaysian Chinese an increased risk of GC was associated with carriage of the IL-1B-1473 G allele {OR=4.4(1.3-15.3)} and the IL-1B-511 C allele {OR=1.8(0.8-4.1)} 5) Increased levels of IL-1b were observed in Singaporean and Malaysian Chinese FD subjects carrying the IL-1-511C and IL-1-1473G alleles 6) Malaysian Chinese not consuming fresh fruit and vegetables had the highest risk of GC {OR=10.2 (3.4-30.6)} 7) The highest risk of GC {OR=37.3(3.3-424.8)} was observed in H. pylori positive Malaysian Chinese who carried both the IL-1B-511C and IL-1B-1473G alleles and did not consume fresh fruit and vegetables. Conclusions: In Malaysian Chinese, H. pylori infection, host genetic and dietary factors all contribute to the risk of GC. However the significant difference observed in the frequency of host genetic polymorphisms within and between ethnic groups suggests that a single group of risk factors cannot be used to determine GC risk across all populations.

A dissertation submitted in partial fulfilment of the requirements for the degree of Bachelor of Arts Masters (Industrial/ Organisational Psychology) in the Faculty of Humanities, University of the Witwatersrand, Johannesburg. March, 2016
This study investigated whether the lifestyle behaviours and psychological well-being of women executives and managers predicted their ten-year risk of developing cardiovascular disease. The sample of South African women executives and managers work in a variety of industries in the cities of Johannesburg, Durban and Cape Town. The study sought to determine the predictability of the women executives and managers’ risk of developing cardiovascular disease through examining their level of alcohol consumption, level of physical exercise and the nutritional and dietary choices that they made as well as their level of depression, anxiety and stress. The data was gathered through an executive health and wellness programme and logistic regression and Chi-squared tests of association were used in conducting the analyses. The results suggested that the level of alcohol consumption and the nutritional and dietary choices made were predictive of the individual’s ten-year risk of developing cardiovascular disease. Additionally, the level of anxiety was found to be associated with the risk of developing cardiovascular disease. The results suggest that both individuals and organisations should prioritise the changing of unhealthy lifestyle behaviours, specifically excessive alcohol consumption and daily dietary choices, in order to lower their risk of developing cardiovascular disease.
MT2017

M.Tech. (Food Technology)
Coeliac disease is an autoimmune disease triggered by the ingestion of gluten; persons suffering from coeliac disease are compelled to follow a life-long gluten-free diet. Gluten-free bread, (GFB), has poor quality attributes compared to wheat bread. The effect of mageu, a traditional beverage on quality parameters of GFB with and without selected hydrocolloids was studied. Mageu produced from maize flour and commercial starter cultures were used in GFB based on sorghum, soybean flour and maize starch. It is hypothesized that mageu with or without hydrocolloids could improve GFB quality aspects. The quality parameters measured were specific volume, loaf height, bake loss, rheological attributes, crumb firmness, firming rate, onset of mould growth and sensory attributes: texture, crumb colour, crust colour, flavour and overall acceptability.....