Introduction. Pima Indians living in the United States (U.S.) have the highest prevalence of type 2 diabetes mellitus in the world. Their Mexican counterparts, living a traditional lifestyle in the mountain of Sonora, Mexico, have at least five times less diabetes than the U.S. Pima Indians. The effects of a traditional lifestyle in reducing type 2 diabetes risk factors and the association of factors to type 2 diabetes were evaluated in a sample of 1211 genetically related Pima Indians living different lifestyles (224 from Mexico and 887 from U.S.). Subsets of these populations were used to address specific questions. First, differences in insulin resistance between subjects with normal glucose tolerance (194 Mexican versus 449 U.S. Pima) were evaluated. Second, the effect of physical activity and obesity explaining differences in metabolic syndrome prevalence were evaluated in 224 and 447 Mexican and U.S. Pima Indians. Third, factors associated with type 2 diabetes were evaluated in each Pima Indian population (224 from Mexico and 887 from U.S.).Methods. Demographic, physical, biochemical, and lifestyle factors were measured in 1996 in a cross-sectional study of Pima Indians 20 years of age or older living in Maycoba, Sonora Mexico and contrasted to results from a sample of U.S. Pima Indians participating in an ongoing epidemiological study that used similar methods and selection criteria. Insulin resistance was estimated by both fasting insulin and homeostasis model assessment-insulin resistance (HOMA-IR). Metabolic syndrome was defined using the Third Report of the National Cholesterol Education Program's Adult Treatment Panel III (NCEP III) criteria. Body mass index (BMI) was calculated by dividing weigh in kilograms by the square of height in meters (Kg/m2). Physical activity was measured using a questionnaire developed for the U.S. Pima Indians and adapted to the Mexican Pima Indian population. Type 2 diabetes was defined according to the 1999 WHO criteria after an oral glucose tolerance test. Multiple linear regression analysis was used to answer the first question (related to differences in insulin resistance) and multiple logistic regressions analysis to answer the second (related with differences in metabolic syndrome) and third questions (related to factors associated with type 2 diabetes).Results. Insulin resistance was much lower in the Mexican Pima Indians than in genetically related U.S. counterparts, even after controlling for differences in obesity, age and sex. In addition, the unadjusted prevalence of metabolic syndrome was 24.1% and 56.6 % in the Mexican and U.S. Pima Indians, respectively. However, most of the difference in metabolic syndrome prevalence was explained by differences in obesity and physical activity. Furthermore, in Mexican Pima Indians, type 2 diabetes was independently associated with age, fasting insulin, and waist circumference. In the U.S. Pima Indians, type 2 diabetes was associated with with age, sex, fasting insulin, total cholesterol, blood pressure and physical activity.Conclusion. The findings underscore the importance of lifestyle in the prevention of type 2 diabetes risk factors, such as insulin resistance and metabolic syndrome, even in individuals with high propensity to develop diabetes.

Orem's Self-Care Deficit Theory was used to inform hypotheses of associations between perceived severity of illness, working memory and self-care among adults (>45 years of age) with Type 2 Diabetes Mellitus (T2DM). Working memory capacity was examined as a foundational capability using Orem's theory. Measures include the modified Diabetes Care Profile section on Health Status Composite (HSC) providing information on severity of illness, the Working Memory Index (WMI) from the Wechsler Adult Intelligence Scale (WAIS-III), the Self-Care Inventory Revised (SCI-R) and hemoglobin A1c. Sixty-seven adults with a mean age of 62.9 years who were primarily Caucasian (92.5%) were involved. There were 30 men and 37 women. Mean body mass index was 35.11 reflecting the majority of participants were obese. Findings indicate that HSC is significantly associated with WMI (r = .54, p < .01) and associated with both indicators of self-care, the SCI-R and HgA1c (r = .23, p<.05, r = -.37, p < .01). Working memory was examined as a mediator between severity of illness and the indicators of self-care (SCI-R and HgA1c) with no evidence for mediation. Findings are discussed in relationship to Orem's Theory of Self-Care Deficit.

Background and Methods: The involvement of iron in the risk for, and complications of, type 2 diabetes has generated substantial interest over the past 15 years, initially sparked by an association with raised serum ferritin, and the observation that people with iron overload diseases frequently develop diabetes. Considerable advances have since been made in understanding the effect glucose has on molecules, cells, and tissues; and the role that oxidative stress plays in the development of the pathologies of long-term diabetes. Poorly liganded iron is potentially both a contributor to, and consequence of, these complications. In vitro experiments with glucose-incubated transferrin by earlier workers have demonstrated loss of function with increasing glycation, leading to the suggestion that the failure of this key iron-binding protein may contribute to diabetic pathology, via the presence of redox active non-transferrin-bound iron (NTBI). In vitro glycated transferrin is examined here by ultrafiltration, to assess loss of function and possible oxidative fragmentation. Mass spectrometry is used to identify a range of amino acid glycation sites on in vitro glycated transferrin for the first time. Finally, several groups have previously measured NTBI in people with diabetes, finding little agreement in results. NTBI is measured here in a cohort of people with type 2 diabetes, using a new adaptation of earlier NTBI assays. NTBI is also assessed in pre-dialysis chronic kidney disease (CKD) stages I to III for the first time. Results and Conclusions: Experiments with glycated transferrin in vitro demonstrate oxidative fragmentation, explaining the loss of function reported by earlier groups. In vitro glycated transferrin examined by mass spectrometry reveals a substantial number and range of amino acids subject to glycation. Comparison with in vivo glycated transferrin suggests that many of the in vitro glycation sites are not glycated in vivo, and that there are many oxidized methionine residues which are potential artefacts, or likely to be repaired by methionine sulphoxide reductases in vivo. A study of people with type 2 diabetes finds no direct association between NTBI and protein glycation. Unexpected correlations between NTBI and LDL, and LDL and haemoglobin with increasing protein glycation, are reported for the first time. NTBI is suggested to be iron sourced from haemoglobin or haem, from erythrocyte haemolysis prior to sample collection. In people with pre-dialysis CKD stages I to III no significant difference in NTBI level compared to controls is seen, or correlations with markers of renal function. No link between NTBI and kidney function at this stage of disease is indicated.

The deleterious effects of Type 2 diabetes on the brain have been shown to result in a greater prevalence of age-associated cognitive impairment and an enhanced risk of age-related cognitive decline in older diabetic populations. Type 2 diabetes is a complex metabolic disorder. Apart from the negative impact of abnormalities intrinsic to diabetes, diabetes-associated cerebral microvascular disease may contribute to this accelerated cognitive ageing. Direct in vivo evaluation of the cerebral microcirculation is difficult in humans and the vessels themselves are too small to permit detailed visualisation with current neuroimaging methods. The microvasculature of the retina may offer a window into such vascular status of the brain as there is considerable homology between the retina and cerebral microcirculations. Moreover, the retinal vasculature is known to be affected by a wide range of systemic pathologies and is unique in that it is the only vasculature that can be directly visualised and photographed. Retinal microvascular abnormalities (RMAs) have been understudied risk factors in cognitive ageing epidemiological research. Few reports have comprehensively examined cognitive function in relation to diabetic retinopathy. Also the relationship between cognitive function and quantitative aspects of retinal vascular network geometry has not been investigated in people with Type 2 diabetes. The results of a systematic review reported in this thesis showed inconsistent findings on the importance of the association between retinal microvascular abnormalities and cognitive dysfunction in predominantly non-diabetic populations. This may have reflected substantial differences between studies regarding the choice of population under study, the methods applied for measuring and defining RMAs, the types of neuropsychological tests administered for assessing cognitive function, and the approach taken in data analysis. The principal aim of the original research described in this thesis was to examine the associations of cognitive test performance with severity of diabetic retinopathy and quantitative parameters of retinal vascular network in a population-based sample of older people with Type 2 diabetes. Objective, reproducible and computerized retinal image analysis was used to quantify retinal vessel calibres and arteriolar bifurcation geometry in order to detect subtle changes in retinal vascular network. A valid estimation of peak prior cognitive ability allowed the further exploration of the impact of retinal microvascular abnormalities on imputed cognitive decline from best-ever levels of cognitive function to that measured in old age. The analysis was based on a cohort of 547 men and 519 women aged 60-75 years with Type 2 diabetes, randomly sampled from the Lothian Diabetes Register, Scotland, in 2006/2007 (the Edinburgh Type 2 Diabetes Study). A battery of seven cognitive tests was administered and standard 7-field binocular digital retinal photography undertaken. The Mill Hill Vocabulary Scale was used to estimate pre-morbid cognitive ability. Diabetic retinopathy was evaluated independently by two optometrists using a standardised grading protocol (a modification of the Early Treatment of Diabetic Retinopathy Scale). Quantitative retinal vascular parameters were measured by myself from a digital image of field 1 using semi-automated, computer-based methods. Retinal vessel calibres were summarised as the central retinal arteriolar and venular equivalents (CRAE and CRVE, respectively) and arterio-venous ratio (AVR). Retinal arteriolar bifurcation geometry was expressed as arteriolar bifurcation angles (BA), arterial branching coefficient (BC), and sub-optimality (degree of deviation from optimality) of the retinal arteriolar angles. The statistical analyses were based on the 1,044 study participants who had both gradable retinal images and cognitive testing. Both general cognition, as indexed by a general cognitive factor reflecting the variance common to all the cognitive tests used, and most of the individual cognitive tests were negatively affected in participants with diabetic retinopathy relative to those without. These cognitive measures also showed a significant relationship with increasing severity of diabetic retinopathy (none, mild, and moderate-severe). Those with moderate-severe diabetic retinopathy had worst performances on general cognitive function, executive function, information processing speed, non-verbal memory and mental flexibility. When lifetime decline was estimated from peak, prior cognitive level, severity of diabetic retinopathy was significantly associated with a greater decline in information processing speed, non-verbal memory and mental flexibility and, in men for general cognition and executive function. The associations of severity of diabetic retinopathy with general cognition, executive function and information processing speed were independent of socio-demographic characteristics, cardiovascular risk factors, macrovascular disease, mood and hyperglycaemia. The associations with estimated decline in specific cognitive measures resulted principally from the impact of diabetic retinopathy on general cognitive ability. The study also showed that larger retinal arteriolar and venular calibres were both significantly associated with lower test scores on verbal memory in men. Multiple linear regression analyses demonstrated larger retinal arteriolar calibre was associated with a significantly greater decline in verbal memory after possible confounding by retinal venular calibre and vascular risk factors and disease was taken into account. In contrast, the study did not support an independent association between retinal venular calibre and cognitive decline in men or in women with Type 2 diabetes. Parameters of retinal arteriolar bifurcation geometry were not associated with cognitive outcome. Overall, these findings support the hypothesis that cerebral microvascular disease associated with Type 2 diabetes, reflected by the presence and severity of diabetic retinopathy, may exacerbate the effects of ageing on cognitive function. In particular, alterations in the blood-brain barrier may be an important pathophysiological mechanism in the occurrence of cognitive dysfunction in diabetic patients. They further may be added to the knowledge that gained from previous pathologic and brain imaging investigations demonstrating a relationship between markers of cerebral microvascular disease and cognitive dysfunction in diabetes. The role of quantitative parameters of retinal vascular network geometry in diabetes-related cognitive impairment is less clear. Prospective studies are required to clarify the temporal sequence of these associations and the eventual clinical significance of these small, early cognitive function changes. Such a follow-up project involving the present study population is underway. From a clinical perspective, if the above findings are substantiated, diabetes-associated cognitive dysfunction may be amenable to treatment and preventive strategies specifically targeted at protecting the cerebral microvasculature and reducing the risk of developing even mild microvascular disease in an ageing diabetic population.

Heme oxygenase (HO) is an enzyme that facilitates the oxidative breakdown of free heme into equi-molar concentrations of carbon monoxide (CO), the bile pigment biliverdin IX and free iron. These products have immuno-modulatory and antioxidative properties, which may be useful in the treatment of diseases characterised by low-grade inflammation and oxidative stress, such as insulin resistance and hyperglycaemia in type 2 diabetes. In fact, HO-1 protein levels and carbon monoxide generation are down-regulated in murine models of obesity and type 2 diabetes. Two independent research teams have reported that pharmacological induction of HO activity by protoporphyrin-based compounds, such as hemin and cobalt (III) protoporphyrin IX chloride (CoPP), exerts anti-diabetic effects, including protection from weight gain, systemic inflammation and peripheral insulin resistance, in various experimental models of type 2 diabetes. However, the relative insolubility and instability of hemin in solution and the multiple side-effects of CoPP, including weight loss, preclude their use for the treatment of patients in clinic. Heme arginate (HA) is a stable and soluble composition of hemin and L-arginine (LA) in a solution containing propylene glycol, ethanol and water. Furthermore, HA is licensed for the treatment of acute porphyria in several European countries. Therefore, HA may potentially be used in clinical trials. The current PhD thesis tests the hypothesis that the heme component of HA ameliorates hyperglycaemia via induction of HO activity in the leptin receptor deficient db/db (db/db) mouse model of type 2 diabetes. A preliminary in vivo study demonstrates that the heme but not the LA component of HA exerts an anti-hyperglycaemic effect in db/db mice. In a separate in vivo study, concomitant treatment of HA with stannous (IV) mesoporphyrin IX dichloride (SM), an inhibitor of HO activity, further improves the glycaemic control despite complete abrogation of the HA-mediated increase in HO activity in db/db mice. This result is in contrast to the above stated hypothesis, and demonstrates that the antihyperglycaemic effect of HA is due to a HO activity independent mechanism. Furthermore, the ameliorative effect of HA and HA+SM treatment on hyperglycaemia in db/db mice coincides with a gain in body and visceral fat weight, a reduction in islet β-cell inflammation and the preservation of islet β-cell function. Subsequent in vitro experiments demonstrate that HA exerts anti-inflammatory effects by a HO activity independent mechanism in pro-inflammatory in vitro models such as in cytokine mix-stimulated MIN6 β-cells and in classically activated bone marrow derived macrophages (BMDMs). In conclusion, the current thesis demonstrates the novel finding that the heme component of HA can exert anti-inflammatory and anti-diabetic effects via a HO activity independent mechanism. Future work should focus on studies to test the hypothesis that the interaction of heme with the nuclear receptor Rev-erb-α is responsible for the anti-inflammatory and anti-diabetic effects of HA.

Background/Objective: Several studies have shown that a low carbohydrate diet (LCHOD) can improve glycaemic control in type 2 diabetes (T2DM). The objective of the current study was to compare two ways of administration of a LCHOD: self-prepared meals versus ready-made meals, and their effects on weight loss, glycaemic control, body composition, cardiovascular risk and resting metabolic rate over 12 months. Research design and methods: Forty-one volunteers with the mean body mass index of 38.8 kg/m2 and poorly controlled T2DM (glycosylated haemoglobin, HbA1c > 7.5%) were randomized to either protein sparing modified fast (< 40g of carbohydrate daily, self-cooked; PSMF) or Go Lower (readymade meals; GL) diet. Both groups received multivitamin supplementation and attended monthly visits. The main outcome was weight loss and its composition. Results: Fourteen (34 %) participants completed 12 months of the intervention. There were no differences in the weight or any other changes between the diet groups at 12 months. Overall, body mass and fat mass decreased (-5.5 ± 7.3 kg, P < 0.001 and -5.1 ± 6.7 kg, P < 0.001 respectively) but fat free mass did not change. There was an overall reduction in HbA1c (-0.4 ± 1.1 %, P < 0.001), increase in HDL-cholesterol (+0.07 ± 0.18 mmol/L, P < 0.001) and decrease in triacylglycerol (-0.6 ± 2.4 mmol/L, P = 0.014). Resting metabolic rate significantly decreased (-137 ± 265 kcal/d, P < 0.001). Conclusion: LCHOD, independently of the approach taken, led to weight loss and improvements in glycaemic control in obese volunteers with poorly controlled T2DM. The results confirm that lifestyle modification using LCHOD is effective for improving T2DM and suggest that the type of approach to the diet can be matched to an individual’s preferences.

Bien que le Diabète de Type 2 soit parfois considéré comme évitable, il est généralement irréversible et les traitements actuels sont communément inefficaces pour stopper la progression inexorable de la maladie vers un mauvais contrôle glycémique et des complications dégénératives micro- et macrovasculaires. Le DT2 est caractérisé par une altération de la sécrétion d’insuline par les cellules beta pancréatiques, combinée à une absence de réponse des organes cibles à l’insuline (insulino-résistance) incluant le foie, le tissu adipeux et le muscle squelettique. Malgré 40 ans de recherches intensives, les mécanismes moléculaires sous-jacents sont toujours largement débattus à ce jour. Le DT2 est une maladie à forte composante génétique, comme l’ont montré les études de jumeaux concordants en général pour le DT2. Au moins 2% des patients atteints de DT2 ont un diabète d’origine monogénique, survenant en général pendant l’enfance ou l’adolescence. L’une de ces formes survient spécifiquement à la naissance (diabète néonatal) et 50% de ses étiologies génétiques sont connus à ce jour. Les formes communes de DT2 survenant chez l’adulte sont polygéniques, liées à l’interaction entre des variants génétiques à effet modeste et faible pénétrance, et l’environnement ; en outre, des mécanismes « épigénétiques » seraient aussi en cause. L’identification des déterminants génétiques du DT2 a été dopée par les études d’association pangénomique (GWAS pour Genome Wide Association Studies) grâce à la mise au point de puces à ADN, qui permettent d’analyser conjointement plusieurs centaines de milliers de polymorphismes nucléotidiques simples (SNPs pour Single Nucleotide Polymorphisms) chez plusieurs centaines de milliers d’individus. Les GWAS ont permis d’identifier à ce jour une trentaine de gènes associées au risque de DT2. Le diagnostic du DT2 repose sur la mesure d’un trait continu, la glycémie à jeun. A partir de 1,25g/l, un individu est considéré diabétique. La glycémie à jeun, même chez des personnes non diabétiques, est fortement héritable, c’est-à-dire que ce paramètre métabolique est sous contrôle génétique. Nous avons ainsi utilisé la méthode des GWAS pour rechercher des loci régulant la glycémie dans des populations générales comme la population française DESIR. Nous avons mis en évidence la contribution du gène MTNR1B (codant le récepteur 2 de la mélatonine) dans la sécrétion d’insuline et la régulation de l’homéostasie glycémique. La mélatonine est l’hormone clef des rythmes circadiens de l’organisme, et il a été rapporté dans plusieurs études que la perturbation de ces rythmes est nuisible à l’homéostasie glycémique. Nous avons pu ensuite préciser quelles étaient les séquences d’ADN ayant un effet dans ce contrôle glycémique. Nous avons ainsi mis en évidence des mutations non-synonymes rares qui annihilaient la voie de signalisation de la mélatonine et qui sont associées à un risque élevé de DT2. Par ailleurs, via le consortium international MAGIC, nous avons contribué à l’identification de 16 marqueurs génétiques de la glycémie à jeun, de cinq marqueurs de la glycémie après charge de glucose, et de 10 loci intervenant dans la variance de l’hémoglobine glyquée (HbA1c, qui est un marqueur communément utilisé pour évaluer le contrôle glycémique d’un diabète traité). Ce faisant, nous avons montré que si le gène HK1 codant l’hexokinase 1 est le facteur génétique ayant le plus d’effet sur les valeurs d’HbA1c, il n’intervient pas sur les mécanismes physiologiques de la régulation de la glycémie. C’est uniquement de par les effets des variants d’HK1 sur la fonction des globules rouges (et sur le risque d’anémie) que ce gène modifie indirectement l’HbA1c. / Type 2 Diabetes is a major health care problem responsible for early morbidities and mortality. T2D prevalence inexorably increases due to dramatic changes in our way of life. T2D is preventable but no generally curable and present medications fail to prevent the worsening of glucose control and the development of complications. T2D is a systemic disease characterized by both insulin secretion defects and by insulin resistance at the levels of several tissues. Despite more than 40 years of research the aetiologies of T2D are still elusive. T2D is a multifactorial disease with a significant genetic component. However, T2D is a polygenic disorder with the effects of multiple DNA variants having a modest effect and a weak penetrance interaction with environmental factors. The identification of T2D susceptibility genes has been transformed by Genome Wide Association Studies (GWAS) which allow the analysis of hundred of thousands Single Nucleotide Polymorphisms (SNPs) in thousands of samples. Case/control GWAS have identified about 30 loci/genes, so far. However, these loci only explain a small part of T2D inheritance. T2D is defined by the measurement of the continuous trait “glycemia”. A fasting plasma glucose (FPG) higher than 7mM is considered to be abnormal. FPG is highly genetically determined and we have reanalyzed our GWAS data obtained in non diabetic general populations to identify genes that control (normal) glucose values. We first found that SNPs at MTNR1B (encoding the melatonin 2 receptor) locus regulate both FPG and insulin secretion. Melatonin is the hormone of darkness that plays a major role in circadian rhythms. The alteration of these physiological rhythms has been shown to impair glucose homeostasis. Subsequently we have screened and functionally analysed the coding part of MTNR1B in thousands of T2D cases and controls for rare lack of function mutations that strongly increase the risk for T2D. In addition via our contribution to the international consortium MAGIC we have identified 16 genetic markers modulating FPG, five controlling blood glucose after oral glucose load, and ten involved in the variance of glycated haemoglobin (HbA1c, a clinical marker of glucose control in treated diabetic patients). In this respect, we have demonstrated that if HK1 (encoding hexokinase 1) is the most potent gene controlling HbA1c, it was not at all involved in the physiology of glucose homeostasis. Instead, variant at HK1 locus act on red cell function, increase risk for anemia, and only indirectly perturb HbA1c measurement. This study shows that GWAS findings don’t mean causality and it is always mandatory to question the physiological validity of any association found through GWAS before implying a gene as causal. In this respect, the MAGIC consortium showed that among all the genes that regulate HbA1c, a large proportion is indeed directly related to red cell function. In conclusion, during my PhD, I have contributed to achieve a map of frequent SNPs regulating the major glucose control quantitative traits that define T2D. I also showed that rare DNA variants with a stronger biological impact also contribute to T2D risk. Although still of limited value for the prediction of T2D, GWAS have proven extremely useful to make progress in T2D physiology.

Class of 2010 Abstract / OBJECTIVES: To evaluate glycemic control, therapy associated weight loss/gain, and hypoglycemic events for the newer type 2 diabetic agents pramlintide, exenatide, and sitagliptin. METHODS: The meta-analysis examined the efficacy of three currently FDA approved peptide analogues in nonpregnant adults with type 2 diabetes mellitus. All randomized, placebo controlled trials of exenatide, pramlintide, and sitagliptin that were indexed in MEDLINE or and the Cochrane Database of Systematic Reviews that fit the inclusion criteria were included. The drug treatment efficacy was analyzed in terms of HbA1c (glycosylated hemoglobin) change from baseline compared to placebo in trials lasting at least 12 weeks. Weight change from baseline per treatment group was also a primary measure. The safety of the treatments was assessed in terms of number of hypoglycemic events noted in the clinical trials. Each of these dependent variables was assessed separately for the three products. RESULTS: The meta-analysis of the six exenatide articles included in the analysis found statistically significant reductions in both HbA1c and weight when compared to placebo. However, patients were three times as likely to experience hypoglycemia with exenatide than placebo (RR= 3.01 95%CI[0.427 to 3.865]). Meta-analysis of pramlintide studies showed statistically significant lowering of HbA1c and weight. Overall pramlintide resulted in a rate of hypoglycemia nearly equal to that of placebo (RR= 0.94 95%CI[0.699 to 1.265]). Meta-analysis of sitagliptin found statistically significant reductions in HbA1c compared to placebo. However, sitagliptin use was not associated with a reduction in weight in the random effects meta-analysis model. In terms of hypoglycemic events, sitagliptin use was associated with 2.89 times greater risk of causing hypoglycemic episodes compared to placebo (RR=2.89 95%CI[0.704 to 5.877]). CONCLUSIONS: All three newer products were associated with improved glycemic control compared to placebo. Improvement in weight was associated with exenatide and pramlintide treatment. Pramlintide was not associated with an increase in hypoglycemic episodes.

Metabolic syndrome (MetS) is a group of obesity-related metabolic abnormalities that predisposes to type II diabetes mellitus (T2DM) and cardiovascular disease. The dramatic increase in incidence of obesity and MetS over the last 25 years amidst relatively constant host genetics supports the role for non-genetic factors such as gut microbiota composition as an important contributor to the development of these disorders. Microbiota can interact with the host, in a manner influenced by genetics and diet that result in low-grade chronic inflammation. A critical risk factor for the pathogenesis of obesity and its related MetS involves alteration of gut microbiota composition with increased innate immune system activation in the intestine increasing risk. Diet-induced obesity is often modeled by comparing mice fed high-fat diet (HFD), which is made from purified ingredients, vs. normal chow diet (NCD), which is a low-fat assemblage of relatively unrefined plant and animal products. The mechanism by which HFD promotes adiposity is complex but thought to involve low-grade inflammation and altered gutmicrobiota. Here, I investigated the extent to which physiological effects to which HFD-induced adiposity is driven by fat content per se vs. other factors that differentiate HFD vs. NCD or other compositionally-defined diets (CDD) and, moreover sought to define the mechanisms that drove such effects. Relative to NCD, HFD, and to a lesser but nonetheless significant extent, CDD induced increased adiposity in addition to a rapid and marked loss of cecal and colonic mass, indicating that both lipid content and other aspects of HFD are obesogenic.CDD-induced effects were not affected by adjusting dietary protein levels/types but could be largely eliminated by exchanging insoluble fiber (cellulose) for soluble fiber (inulin). Moreover, replacing cellulose with inulin in HFD protected mice against decreased intestinal mass, hyperphagia and increased adiposity. Such protective effects of inulin correlated with increased levels of short-chain fatty acids, which are the products of bacterial fermentation of inulin. Lack of a microbiota, achieved by use of germ-free mice prevented generation of SCFA and eliminated the beneficial effects of inulin. Together, these results indicate that HFD-induced obesity is promoted by its lack of soluble fiber, which, when present, supports microbiota-mediated intestinal epithelia homeostasis that prevents inflammation driving obesity and MetS.

Manitoba has the highest rate of type 2 diabetes in Canada, exceeding other provinces 12-fold. Current literature has suggested that social supports are critical to the promotion and adoption of healthy living in youth living with type 2 diabetes. As such, high quality social support has been perceived as positive and can enhance youths’ resilience against life stressors. Despite this suggestion, there is little evidence on how best to support this population. The purpose of this Masters thesis was to explore the meaning of social support among Manitoban youth living with type 2 diabetes. Guided by a constructivist grounded theory approach, youth identified the following avenues of social support: family, friends, health care professionals, school and programming. Future interventionists should be aware of the vast incongruence in patients’ and physician’s perceptions of health in type 2 diabetes and design interventions accordingly. / February 2017