Browsing by Subject "Glucose Intolerance"

Now showing 1 - 5 of 5
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    12-Lipoxygenase Promotes Obesity-Induced Oxidative Stress in Pancreatic Islets
    (American Society for Microbiology (ASM), 2014-10) Tersey, Sarah A.; Maier, Bernhard; Nishiki, Yurika; Maganti, Aarthi V.; Nadler, Jerry L.; Mirmira, Raghavendra G.; Department of Pediatrics, IU School of Medicine
    High-fat diets lead to obesity, inflammation, and dysglycemia. 12-Lipoxygenase (12-LO) is activated by high-fat diets and catalyzes the oxygenation of cellular arachidonic acid to form proinflammatory intermediates. We hypothesized that 12-LO in the pancreatic islet is sufficient to cause dysglycemia in the setting of high-fat feeding. To test this, we generated pancreas-specific 12-LO knockout mice and studied their metabolic and molecular adaptations to high-fat diets. Whereas knockout mice and control littermates displayed identical weight gain, body fat distribution, and macrophage infiltration into fat, knockout mice exhibited greater adaptive islet hyperplasia, improved insulin secretion, and complete protection from dysglycemia. At the molecular level, 12-LO deletion resulted in increases in islet antioxidant enzymes Sod1 and Gpx1 in response to high-fat feeding. The absence or inhibition of 12-LO led to increases in nuclear Nrf2, a transcription factor responsible for activation of genes encoding antioxidant enzymes. Our data reveal a novel pathway in which islet 12-LO suppresses antioxidant enzymes and prevents the adaptive islet responses in the setting of high-fat diets.
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    Comparison of β-Cell Function Between Overweight/Obese Adults and Adolescents Across the Spectrum of Glycemia
    (American Diabetes Association, 2018-02) Chen, Melinda E.; Chandramouli, Aaditya G.; Considine, Robert V.; Hannon, Tamara S.; Mather, Kieren J.; Pediatrics, School of Medicine
    OBJECTIVE: Type 2 diabetes is a growing health problem among both adults and adolescents. To better understand the differences in the pathogenesis of diabetes between these groups, we examined differences in β-cell function along the spectrum of glucose tolerance. RESEARCH DESIGN AND METHODS: We evaluated 89 adults and 50 adolescents with normal glucose tolerance (NGT), dysglycemia, or type 2 diabetes. Oral glucose tolerance test results were used for C-peptide and insulin/glucose minimal modeling. Model-derived and direct measures of insulin secretion and insulin sensitivity were compared across glycemic stages and between age-groups at each stage. RESULTS: In adolescents with dysglycemia, there was marked insulin resistance (insulin sensitivity index: adolescents, median [interquartile range] 1.8 [1.1-2.4] × 10-4; adults, 5.0 [2.3-9.9]; P = 0.01). The nature of β-cell dysfunction across stages of dysglycemia differed between the groups. We observed higher levels of secretion among adolescents than adults (total insulin secretion: NGT, 143 [103-284] × 10-9/min adolescent vs. 106 [71-127], P = 0.001); adults showed stepwise impairments in static insulin secretion (NGT, 7.5 [4.0-10.3] × 10-9/min; dysglycemia, 5.0 [2.3-9.9]; type 2 diabetes, 0.7 [0.1-2.45]; P = 0.003), whereas adolescents showed diabetes-related impairment in dynamic secretion (NGT, 1,905 [1,630-3,913] × 10-9; dysglycemia, 2,703 [1,323-3,637]; type 2 diabetes, 1,189 [269-1,410]; P = 0.001). CONCLUSIONS: Adults and adolescents differ in the underlying defects leading to dysglycemia, and in the nature of β-cell dysfunction across stages of dysglycemia. These results may suggest different approaches to diabetes prevention in youths versus adults.
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    Membrane cholesterol balance in exercise and insulin resistance
    (2009-10) Habegger, Kirk M.; Elmendorf, Jeffrey S.; Roach, Peter J.; Brozinick, Joseph T.; Sturek, Michael S.; Considine, Robert V.
    Study has shown that plasma membrane (PM) cholesterol and cortical filamentous actin (F-actin) influence skeletal muscle glucose transport. Of fundamental and clinical interest is whether diabetogenic insults promote membrane/cytoskeletal dysfunction amendable for therapy. As exposure to excess fatty acid (FA)s induce glucose intolerance by mechanisms imperfectly understood, we tested if PM cholesterol/F-actin changes could contribute to FA-induced glucose transporter GLUT4 dysregulation in skeletal muscle. High-fat fed, insulin-resistant animals displayed elevated levels of skeletal muscle PM cholesterol and a loss in cortical F-actin, compared to normal-chow fed animals. Consistent with a PM cholesterol component of glucose intolerance, human skeletal muscle biopsies revealed an inverse correlation between PM cholesterol and whole-body glucose disposal. Mechanistically, exposure of L6 myotubes to the saturated FA palmitate induced an increase in PM cholesterol that destabilized actin filaments and decreased insulin-stimulated PM GLUT4 and glucose transport, which could be reversed with cholesterol lowering. Next, study tested if the lipid-lowering action of the antidiabetic AMP-activated protein kinase (AMPK) had a beneficial influence on PM cholesterol balance. Consistent with AMPK inhibition of 3-hydroxy-3-methylglutaryl CoA reductase, a rate-limiting enzyme of cholesterol synthesis, we found that AMPK activation promoted a significant reduction in PM cholesterol and amplified basal and insulin-stimulated GLUT4 translocation. A similar loss of PM cholesterol induced by β-cyclodextrin caused an analogous enhancement of GLUT4 regulation. Interestingly, PM cholesterol replenishment abrogated the AMPK effect on insulin, but not basal, regulation of GLUT4 translocation. Conversely, AMPK knockdown prevented the enhancement of both basal and insulin-stimulated GLUT4 translocation. As a whole these studies show PM cholesterol accrual and cortical F-actin loss uniformly in skeletal muscle from glucose-intolerant mice, swine, and humans. In vivo and in vitro dissection demonstrated this membrane/cytoskeletal derangement induces insulin resistance and is promoted by excess FAs. Parallel studies unveiled that the action of AMPK entailed lowering PM cholesterol that enhanced the regulation of GLUT4/glucose transport by insulin. In conclusion, these data are consistent with PM cholesterol regulation being an unappreciated aspect of AMPK signaling that benefits insulin-stimulated GLUT4 translocation during states of nutrient excess promoting PM cholesterol accrual.
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    Metabolic syndrome components and their response to lifestyle and metformin interventions are associated with differences in diabetes risk in persons with impaired glucose tolerance
    (Wiley Blackwell (Blackwell Publishing), 2014-04) Florez, Hermes; Temprosa, Marinella G.; Orchard, Trevor J.; Mather, Kieren J.; Marcovina, Santica M.; Barrett-Connor, Elizabeth; Horton, Edward; Saudek, Christopher; Pi-Sunyer, Xavier F.; Ratner, Robert E.; Goldberg, Ronald B.; Department of Medicine, IU School of Medicine
    AIMS: To determine the association of metabolic syndrome (MetS) and its components with diabetes risk in participants with impaired glucose tolerance (IGT), and whether intervention-related changes in MetS lead to differences in diabetes incidence. METHODS: We used the National Cholesterol Education Program/Adult Treatment Panel III (NCEP/ATP III) revised MetS definition at baseline and intervention-related changes of its components to predict incident diabetes using Cox models in 3234 Diabetes Prevention Program (DPP) participants with IGT over an average follow-up of 3.2 years. RESULTS: In an intention-to-treat analysis, the demographic-adjusted hazard ratios (95% confidence interval) for diabetes in those with MetS (vs. no MetS) at baseline were 1.7 (1.3-2.3), 1.7 (1.2-2.3) and 2.0 (1.3-3.0) for placebo, metformin and lifestyle groups, respectively. Higher levels of fasting plasma glucose and triglycerides at baseline were independently associated with increased risk of diabetes. Greater waist circumference (WC) was associated with higher risk in placebo and lifestyle groups, but not in the metformin group. In a multivariate model, favourable changes in WC (placebo and lifestyle) and high-density lipoprotein cholesterol (placebo and metformin) contributed to reduced diabetes risk. CONCLUSIONS: MetS and some of its components are associated with increased diabetes incidence in persons with IGT in a manner that differed according to DPP intervention. After hyperglycaemia, the most predictive factors for diabetes were baseline hypertriglyceridaemia and both baseline and lifestyle-associated changes in WC. Targeting these cardiometabolic risk factors may help to assess the benefits of interventions that reduce diabetes incidence.
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    SAT-158 Offspring Exposed to Maternal High Fat Diet Exhibits Systemic Inflammation and Pancreatic Islet Dysfunction
    (Oxford University Press, 2019-04-15) Casasnovas, Jose; Pineros, Annie; Jarrell, James; Kua, Kok Lim; Pediatrics, School of Medicine
    Offspring born to overweight mothers are more likely to develop dysregulated immune response1, obesity1 and pancreatic islet dysfunction2. These offspring have increased inflammation at birth3 and at least until childhood4. We hypothesize that heightened inflammation in offspring of overweight mothers increases offspring risks of pancreatic islet dysfunction. We induced maternal overweight by providing 45% high fat diet (HFD) to female mice 2 - 4 weeks before pregnancy until weaning. When compared to controls, P21 weanlings of HFD mothers had impaired glucose tolerance in dose and gender dependent manner [GTT AUC: male 2-week HFD* 30 ± 6% higher; male 4-week HFD* 37± 3% higher: 9-11/group; female 2-week HFD 13 ± 5% higher; female 4-week HFD* 22 ± 3% higher: 3-9/group, *p<0.05 compared to controls]. Glucose intolerance persisted in 8-week-old male from 2-week HFD mothers (p<0.05, n=6-9/group), with decreased pancreatic islets glucose induced calcium response measured using Fura-2AM calcium imaging (F1/F0 Con:2.00 ± 0.06, HFD2W: 1.69±0.12*, HFD4w: 0.71±0.09*, n =3/group). Cytokines production in the serum, macrophage response and metabolic phenotypes of offspring were assessed on postnatal day 21 (P21) and at 8 weeks old. Compared to control pups, weanling of HFD mothers had elevated serum/plasma IL-1b level along with increased polarization of M1 macrophages and decreased M2 macrophages, as well as an increase of IL-1b secretion in LPS-stimulated macrophages. At 8 weeks of age, HFD male offspring had increased activation markers of splenic dendritic cells indicating a development of systemic inflammatory response early in life. Taken together, our findings suggest that mice offspring from HFD mothers have pancreatic dysfunction, and an inflammatory response. This work is funded by the Riley Children’s Foundation. 1. Kelishadi, R., Roufarshbaf, M., Soheili, S., Payghambarzadeh, F. & Masjedi, M. Association of Childhood Obesity and the Immune System: A Systematic Review of Reviews. Child. Obes. Print 13, 332-346 (2017). 2. Graus-Nunes, F. et al. Pregestational maternal obesity impairs endocrine pancreas in male F1 and F2 progeny. Nutrition 31, 380-387 (2015). 3. Dosch, N. C. et al. Maternal Obesity Affects Inflammatory and Iron Indices in Umbilical Cord Blood. J. Pediatr. 172, 20-28 (2016). 4. Leibowitz, K. L. et al. Maternal obesity associated with inflammation in their children. World J. Pediatr. WJP 8, 76-79 (2012).