Methylglyoxal (MG) is a reactive metabolite presents in all biological systems. The accumulation of MG in diabetic patients and animals has been long recognized. Recently, studies have shown that MG levels are elevated in hypertensive rats. However, the pathological effects of MG in diabetes and related insulin resistance syndrome such as obesity are currently unknown. In the present study, the role of MG in the pathogenesis of insulin resistance was investigated.<p> First, it was observed that MG induced structural and functional changes of insulin. Incubation of human insulin with MG in vitro yielded MG-insulin adducts, as evidenced by additional peaks observed upon mass spectrometric (MS) analysis. Tandem MS analysis of insulin B-chain adducts confirmed attachment of MG at an arginine residue. [3H]-2-deoxyglucose uptake ([3H]-2-DOG) by 3T3-L1 adipocytes was significantly and concentration-dependently decreased after treatment with MG-insulin adducts, in comparison with the effect of native insulin at the same concentration. A significant decrease of glucose uptake induced by MG-insulin adducts was also observed in L8 skeletal muscle cells. Unlike native insulin, MG-insulin adducts did not inhibit insulin release from pancreatic â-cells. The degradation of MG-insulin by cultured liver cells was also decreased. In conclusion, MG modifies insulin by attaching to internal arginine residue in the â-chain of insulin. The formation of this MG-insulin adduct decreases insulin-mediated glucose uptake, impairs autocrine control of insulin secretion, and decreases insulin clearance. These structural and functional abnormalities of the insulin molecule may contribute to the pathogenesis of insulin resistance.<p> Second, the effects of MG on the insulin signaling pathway were investigated. After 9 weeks of fructose treatment, an insulin resistant state was developed in Sprague-Dawley (SD) rats, demonstrated as increased triglyceride and insulin levels, elevated blood pressure, and decreased insulin-stimulated glucose uptake by adipose tissue. A close correlation between insulin resistance and the elevated MG accumulation in adipose and skeletal muscle tissues was observed. The insulin resistant state and the elevated MG level were reversed by the MG scavenger, N-acetyl cysteine (NAC) and metformin. In cultured adipose cells, MG treatment impaired insulin signaling as measured by decreased tyrosine phosphorylation of insulin-receptor substrate-1 (IRS-1) and the decreased kinase activity of phosphatidylinositol 3-kinase (PI3K). The ability of NAC to block MG-impairment of PI3K activity and IRS-1 phosphorylation further confirmed the role of MG in the development of insulin resistance. In cultured skeletal muscle cells, MG treatment significantly reduced the expression of IRS-1 and PI3K at the mRNA level. Similar to adipose cells, MG also decreased tyrosine phosphorylation of IRS-1 and PI3K activity. We also examined the mechanism of metformin to inhibit AGEs. Using mass spectrometry, stable metformin-MG adducts were identified.<p> In addition, we investigated the causative effect of MG in the pathogenesis of obesity, another form of insulin resistance. This study revealed a previously unrecognized effect of MG in stimulating adipogenesis by up-regulating Akt signaling. In Zucker fatty rats, dramatically increased MG accumulations in serum and different tissues were identified. The serum MG level increased age. In 10 and 12 week-old obese rats, MG was 144±50% and 171±15% of the age-matched control Zucker rats; this value increased to 241±7 % and 329±10% by 14 and 16 weeks (P<0.05, n=4). Further study suggested that MG accumulation stimulates the phosphorylation of Akt and its effectors p21 and p27. The activated Akt pathway then increased the activity of Cdk2 and accelerates the cell cycle progression and proliferation of pre-adipocytes. The effects of MG were efficiently reversed by both alagebrium, and Akt inhibitor SH-6.<p> Overall, the current study investigated the effect of MG during the pathogenesis of insulin resistance syndrome. MG, as the most potent precursor of AGEs, impairs the activity of insulin signaling pathway by glycating the insulin molecule and other insulin signaling proteins. Moreover, this study observed a previously unrecognized causative effect of MG in the proliferation of adipocytes by up-regulating the Akt signaling pathway. The results from this study offer new mechanisms to explain the development of insulin resistance and to prevent the related diseases.

Obesity is an increasing health problem which is causally associated with insulin resistance and type 2 diabetes. Oxidative stress, i.e. overproduction of reactive oxygen species, is associated with insulin resistance and obesity and may be a major risk factor in the onset and progression of diabetes. Bernlohr Lab at University of Minnesota have study oxidative stress in adipocytes by silencing the enzyme glutathione S-transferase A-4 (GSTA4), an enzyme detoxifying 4-hydroxynonenal formed during oxidative stress. Their results indicate that lysine acetylation, an important post-translational modification, may be involved during oxidative stress. In this study lysine acetylation has been investigated in condition of oxidative stress in 3T3-L1 adipocytes and subcutaneous adipose tissue from mice using SDS-PAGE gel electrophoresis and western blot. Lysine acetylation was analyzed in different compartments of the cell such as in cytoplasm, mitochondria as well as in whole cell extracts. Silencing of GSTA4 and stimulation by TNF-α in 3T3-L1 adipocytes resulted in an increase of lysine acetylation in cytoplasm. Furthermore, stimulation by IL-6 did not have any effect on lysine acetylation. Surprisingly, subcutaneous adipose tissue from mice fed on a high-fat diet showed a decrease of lysine acetylation in cytoplasm compare to mice fed on a chow diet. In conclusion, lysine acetylation seems to change during oxidative stress and may be an important factor during insulin resistance, type 2 diabetes and obesity. Therefore, studying lysine acetylation and enzymes modulating acetylation may potentially increase our understanding of insulin resistance, type 2 diabetes and obesity and could lead to new therapies.

Atherosclerotic cardiovascular disease (ASCVD) is currently the most common cause of death in the United States. Some dietary factors contribute importantly to ASCVD and other factors can reduce risk of ASCVD. Oleic acid is a monounsaturated fatty acid (MUFA). Dietary patterns in which oleic acid contributes to a majority of dietary fatty acids are associated with reduced ASCVD risk. These beneficial effects are due to MUFA-induced lipoprotein profile changes such as decreases in low density lipoprotein (LDL) and increases in high density lipoprotein (HDL). LDL oxidation plays a central role in atherosclerosis development as it both initiates and propagates atherosclerosis. HDL is anti-atherogenic as it can attenuate LDL oxidation. HDLs are a class of diverse lipoprotein that varies in protein and enzymatic composition. The paraoxonase (PON) family of enzymes, especially PON1, is primarily expressed in the liver; PON activity in the circulatory system is associated with HDL. Both PON and HDL have been documented to be anti-atherogenic. Other factors such as homocysteine and C-reactive protein (CRP) can also be considered risk factors for ASCVD. However, studies of risk factors in healthy men who consume ground beef with a different content of MUFA are lacking; hence, no conclusive evidence has established whether consuming a high amount of MUFA in the form of ground beef alters the development of atherosclerosis. The overall purpose of this study was to investigate whether the provision of ground beef with a fractionally higher MUFA content could lower or improve several ASCVD risk factors in men who consume ground beef. These risk factors include the metabolic indices of glucose, insulin and homeostasis model assessment (HOMA), inflammation risk factors of CRP and homocysteine and anti-risk factor of paraoxonase. The concentration of homocysteine was determined spectrophotometrically following separation by high pressure liquid chromatography (HPLC). Enzyme-linked imminosorbent assay kits that measured the CRP and insulin concentration in plasma. The significance of the results was determined by subjecting the data to ANOVA using the general linear model for repeated measurement (P<0.05). From this study, it can be concluded that MUFA has a beneficial effect of lowering risks as determined by metabolic indices and lipoprotein profile. Moreover, our study showed that different concentrations of MUFA in ground beef has no effect on PON1 activity, but that increased beef consumption generally reduces PON1 in association with increases in homocysteine concentration while improving indicators of glucose tolerance.

This study determined the effects of gestational obesity on the long-term metabolic status of the mother and if obesity management during or after pregnancy could attenuate these effects. At 120 days prior to estrus, 8 ewes received 100 percent of NRC nutrient requirements (control group) and 24 ewes had free access to feed (obesity induction). Beginning on day 42 of gestation, 8 obese ewes were restricted to 65 percent of NRC nutrient requirements. Following parturition, controls and all but one group of obese ewes were fed 100 percent of NRC nutrient requirements. At postpartum days (PPD) 1 and 150, glucose tolerance tests were administered to ewes. At both PPD1 and PPD150, obesity resulted in insulin resistance, impairment of whole-body glucose utilization, increased levels of circulating leptin, and altered profiles of amino acids in plasma; however, these effects were diminished in ewes receiving obesity management during or after gestation. Additionally at PPD150, obesity increased the circulating levels of ammonia and urea in ewes, which was prevented by realimentation to 100 percent NRC requirements. These results indicate that weight reduction in obese dams during pregnancy or after parturition can beneficially ameliorate the adverse effects of gestational obesity on the mother.

No description available.

Thesis (Ph.D.)--East Carolina University, 2009. / Presented to the faculty of the Department of Exercise and Sports Science. Advisor: Joseph A. Houmard. Title from PDF t.p. (viewed Apr. 30, 2010). Includes bibliographical references.

The goal of this work was to characterize avian skeletal muscle (SKM) glucose and fatty acid uptake. English sparrows (Passer domesticus) were used for the following studies: 1. Characterization of glucose uptake, 2. Identification and localization of glucose transporters, 3. Characterization of free fatty acid uptake, and 4. Reciprocal inhibition of glucose and free fatty acids. The results are summarized as follows. Isolated SKM incubated for 60 minutes with insulin, IGF-1, caffeine or AICAR demonstrated no increase in glucose transport. Interestingly, uptake was decreased in the presence of incremental unlabeled glucose suggesting the presence of glucose transporters (GLUT) and by phloretin, an inhibitor of transport proteins, decreased transport. The SKM glycogen content was low, which is supportive of the observed minimal glucose uptake. These findings suggest that GLUT expression may differ in birds as compared to mammals. GLUT1 and GLUT3 gene expression, but not GLUT4, were found in all tissues examined and share a high degree of homology with published chicken sequences. In addition, GLUT3 and GLUT4 proteins were not detected, whereas GLUT1 protein was abundant in blood-tissue barriers. Sparrows have high plasma ketone body levels suggestive of a high rate of free fatty acid (FFA) oxidation. In vitro uptake of radiolabeled oleic acid (OA) was maximal at 60 minutes and competitively inhibited by unlabeled OA suggesting a facilitative process. Radiolabeled OA uptake was not increased by IGF-1, caffeine and AICAR, whereas insulin increased uptake at 60 minutes. Inhibitors of protein-mediated substrate transport increased OA uptake by 60 minutes (DIDS and phloretin) whereas a specific inhibitor of long chain FFA transport, sulfo-N-succinimidyl oleate, decreased its uptake at 2.5 min. In reciprocal inhibition studies, 20mM unlabeled glucose and OA inhibited the uptake of their radiolabeled counterparts. Glucose (20mM) significantly decreased labeled OA uptake 36% and 20mM OA significantly decreased labeled glucose transport by 49%. These data begin to elucidate why avian skeletal muscle may not take up glucose to an appreciable extent and further, why avian skeletal muscle is insulin resistant.

Obesity, characterized by an excess of adipose tissue, is an established risk factor for cardiovascular disease and type II diabetes. Different mechanisms linking obesity with these comorbidities have been postulated but remain poorly understood. Adipose tissue secretes bioactive signaling molecules, termed adipokines, which regulate various biological functions including appetite, energy balance, glucose homeostasis, and inflammation. Chemerin is a novel adipokine that regulates adipocyte differentiation and metabolism by binding to and activating the G protein-coupled receptor chemokine like receptor-1 (CMKLR1). Herein, we have shown that serum levels of the novel adipokine chemerin are significantly elevated in mouse models of obesity/diabetes. Administration of exogenous chemerin exacerbates glucose intolerance, lowers serum insulin levels, and decreases tissue glucose uptake in obese/diabetic but not normoglycemic mice. In CMKLR1-deficient mice food consumption, total body mass, and percent body fat are lower compared to wildtype controls, regardless of diet (low or high fat). CMKLR1-/- mice also exhibited decreased hepatic and white adipose tissue TNF? and IL-6 mRNA levels coincident with decreased hepatic dendritic cell infiltration, decreased adipose CD3+ T cells and increased adipose natural killer cells. CMKLR1-/- mice were also glucose intolerant compared to wildtype mice, and this was associated with decreased glucose stimulated insulin secretion as well as decreased skeletal muscle and white adipose tissue glucose uptake. Collectively, these data provide compelling evidence that chemerin/CMKLR1 signaling influences adipose tissue development, inflammation, and glucose homeostasis and may contribute to the metabolic derangements characteristic of obesity and obesity-related diseases.

No description available.

This study was conducted to determine the level of knowledge and perceptions of Type Two Diabetes Mellitus (T2DM) among people in Rwamagana District. A quantitative descriptive design and a cluster multistage sampling technique were used in this study. Out of a sample of 355 people, 301 voluntary participated in the study and completed the anonymous questionnaires. The response rate was 85%. The questions in the questionnaire were designed to collect socio-demographic information of the participants, their knowledge of diabetes and their perceptions of diabetes. Analysis of findings revealed that the level of knowledge of diabetes was inadequate and low among participants. Very few participants were able to answer properly the questions aimed to explore their knowledge of the meaning, signs/symptoms, causes, risk factors, management and prevention of diabetes. In addition many participants answered that they had no knowledge about any of the aspects of diabetes explored in our questionnaire. The perceptions were also poor and inadequate, especially perceptions of diabetes management at the community level and of diabetes prevention. The perceived risk of developing diabetes was low and many participants felt that behaviour change was of no importance in the prevention of diabetes, since the majority reported that they were not planning any behaviour change in the future. The findings suggest that there is a need for education campaigns in Rwamagana district to raise public knowledge about all aspects of diabetes. There is a need also to train the community health workers of this district to enable them to offer proper advice at the community level about diabetes prevention and management. The findings from this study could be used to assist in the planning of diabetes prevention and management programs in Rwamagana district. / Thesis (M.N.)-University of KwaZulu-Natal, Howard College, 2010.