84,369 research outputs found
Serum IgG2 levels are specifically associated with whole-body insulin-mediated glucose disposal in non-diabetic offspring of type 2 diabetic individuals. a cross-sectional study
.Preclinical studies suggested that IgG2c isotype may specifically impair skeletal muscle insulin
sensitivity in mice. In this study we investigated the association between serum levels of the four IgG
subclasses and insulin sensitivity in non-diabetic individuals. Total IgG, IgG1, IgG2, IgG3 and IgG4
levels were measured in 262 subjects. Whole-body insulin sensitivity was assessed by euglycemic
hyperinsulinemic clamp. IgG2 levels were positively correlated with BMI, waist circumference, 2-h postload
glucose levels and complement C3. Serum IgG2, but not IgG1, IgG3 and IgG4 levels were negatively
correlated with whole-body insulin sensitivity (r = −0.17; P = 0.003) and muscle insulin sensitivity index
(r = −0.16; P = 0.03) after adjustment for age and gender. No significant correlation was found between
IgG2 levels and hepatic insulin resistance assessed by HOMA-IR and liver IR index. In a multivariable
regression analysis including variables known to affect insulin sensitivity such as age, gender, BMI,
smoking, lipids, inflammatory markers, fasting and 2-h post-load glucose levels, IgG2 levels were
independently associated with insulin-stimulated glucose disposal (β = −0.115, 95% CI: −0.541 to
−0.024; P = 0.03). These data demonstrate the independent association between higher levels of IgG2
and decreased whole-body insulin sensitivity, thus confirming in humans the animal-based evidence
indicating the pathogenic role of IgG2 in insulin resistance
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Adipocyte JAK2 Regulates Hepatic Insulin Sensitivity Independently of Body Composition, Liver Lipid Content, and Hepatic Insulin Signaling.
Disruption of hepatocyte growth hormone (GH) signaling through disruption of Jak2 (JAK2L) leads to fatty liver. Previously, we demonstrated that development of fatty liver depends on adipocyte GH signaling. We sought to determine the individual roles of hepatocyte and adipocyte Jak2 on whole-body and tissue insulin sensitivity and liver metabolism. On chow, JAK2L mice had hepatic steatosis and severe whole-body and hepatic insulin resistance. However, concomitant deletion of Jak2 in hepatocytes and adipocytes (JAK2LA) completely normalized insulin sensitivity while reducing liver lipid content. On high-fat diet, JAK2L mice had hepatic steatosis and insulin resistance despite protection from diet-induced obesity. JAK2LA mice had higher liver lipid content and no protection from obesity but retained exquisite hepatic insulin sensitivity. AKT activity was selectively attenuated in JAK2L adipose tissue, whereas hepatic insulin signaling remained intact despite profound hepatic insulin resistance. Therefore, JAK2 in adipose tissue is epistatic to liver with regard to insulin sensitivity and responsiveness, despite fatty liver and obesity. However, hepatocyte autonomous JAK2 signaling regulates liver lipid deposition under conditions of excess dietary fat. This work demonstrates how various tissues integrate JAK2 signals to regulate insulin/glucose and lipid metabolism
Effect of Progressive Weight Loss on Lactate Metabolism: A Randomized Controlled Trial.
OBJECTIVE:Lactate is an intermediate of glucose metabolism that has been implicated in the pathogenesis of insulin resistance. This study evaluated the relationship between glucose kinetics and plasma lactate concentration ([LAC]) before and after manipulating insulin sensitivity by progressive weight loss. METHODS:Forty people with obesity (BMI = 37.9 ± 4.3 kg/m2 ) were randomized to weight maintenance (n = 14) or weight loss (n = 19). Subjects were studied before and after 6 months of weight maintenance and before and after 5%, 11%, and 16% weight loss. A hyperinsulinemic-euglycemic clamp procedure in conjunction with [6,6-2 H2 ]glucose tracer infusion was used to assess glucose kinetics. RESULTS:At baseline, fasting [LAC] correlated positively with endogenous glucose production rate (r = 0.532; P = 0.001) and negatively with insulin sensitivity, assessed as the insulin-stimulated glucose disposal (r = -0.361; P = 0.04). Progressive (5% through 16%) weight loss caused a progressive decrease in fasting [LAC], and the decrease in fasting [LAC] after 5% weight loss was correlated with the decrease in endogenous glucose production (r = 0.654; P = 0.002) and the increase in insulin sensitivity (r = -0.595; P = 0.007). CONCLUSIONS:This study demonstrates the interrelationships among weight loss, hepatic and muscle glucose kinetics, insulin sensitivity, and [LAC], and it suggests that [LAC] can serve as an additional biomarker of glucose-related insulin resistance
Improved insulin sensitivity following a short-term whole body vibration intervention
Background and Objective: Despite being recommended for reducing the risk of type 2 diabetes (T2D) the majority of the population do not partake in the advised amount of regular exercise. While high intensity type training has been shown to produce improvements in insulin sensitivity its uptake in high risk populations has been questioned. Contrastingly, whole body vibration training (WBVT) is reported to benefit a range of outcomes in a variety of populations. Limited data exists regarding this training modality on insulin sensitivity. Current study assessed the effect of WBVT on oral glucose tolerance response. Method: Following institutional ethics approval, five young healthy sedentary individuals undertook oral glucose tolerance test (OGTT) prior to and on completion of 5-week progressive WBVT. Result: There were no changes in fasting plasma glucose concentrations before and after the 6 weeks of WBVT. Both pre- and post-training OGTT revealed no significant changes in plasma glucose concentrations over time. There was a 9% reduction in plasma glucose area under the curve (AUC) post training. The Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) decreased by 21% and Cederholm index of insulin sensitivity was increased by 18% following WBVT. Conclusion: Results suggest WBVT is associated with improved insulin sensitivity and could produce clinically relevant effects on fat metabolism in sedentary young people. Large-scale studies are now necessary to assess the effectiveness of WBVT in diabetic populations
FAM13A and POM121C are candidate genes for fasting insulin: functional follow-up analysis of a genome-wide association study
Aims/hypothesis: By genome-wide association meta-analysis, 17 genetic loci associated with fasting serum insulin (FSI), a
marker of systemic insulin resistance, have been identified. To define potential culprit genes in these loci, in a cross-sectional
study we analysed white adipose tissue (WAT) expression of 120 genes in these loci in relation to systemic and adipose tissue
variables, and functionally evaluated genes demonstrating genotype-specific expression in WAT (eQTLs).
Methods: Abdominal subcutaneous adipose tissue biopsies were obtained from 114 women. Basal lipolytic activity was measured
as glycerol release from adipose tissue explants. Adipocytes were isolated and insulin-stimulated incorporation of
radiolabelled glucose into lipids was used to quantify adipocyte insulin sensitivity. Small interfering RNA-mediated knockout
in human mesenchymal stem cells was used for functional evaluation of genes.
Results: Adipose expression of 48 of the studied candidate genes associated significantly with FSI, whereas expression of 24, 17
and 2 genes, respectively, associated with adipocyte insulin sensitivity, lipolysis and/or WAT morphology (i.e. fat cell size relative
to total body fat mass). Four genetic loci contained eQTLs. In one chromosome 4 locus (rs3822072), the FSI-increasing allele
associated with lower FAM13A expression and FAM13A expression associated with a beneficial metabolic profile including
decreased WAT lipolysis (regression coefficient, R = −0.50, p = 5.6 × 10−7). Knockdown of FAM13A increased lipolysis by ~1.5-
fold and the expression of LIPE (encoding hormone-sensitive lipase, a rate-limiting enzyme in lipolysis). At the chromosome 7
locus (rs1167800), the FSI-increasing allele associated with lower POM121C expression. Consistent with an insulin-sensitising
function, POM121C expression associated with systemic insulin sensitivity (R = −0.22, p = 2.0 × 10−2), adipocyte insulin sensitivity
(R = 0.28, p = 3.4 × 10−3) and adipose hyperplasia (R = −0.29, p = 2.6 × 10−2). POM121C knockdown decreased expression
of all adipocyte-specific markers by 25–50%, suggesting that POM121C is necessary for adipogenesis.
Conclusions/interpretation: Gene expression and adipocyte functional studies support the notion that FAM13A and POM121C
control adipocyte lipolysis and adipogenesis, respectively, and might thereby be involved in genetic control of systemic insulin
sensitivity
Special Article: Physical Activity, Physical Fitness, and Cardiovascular Risk Factors in Childhood
In adults, physical activity and exercise training are associated with reduced cardiovascular morbidity and mortality, a reduced likelihood of developing adverse cardiovascular risk factors, and improved insulin sensitivity. In childhood, participation in appropriate physical activity may prevent the development of cardiovascular risk factors in the future and complement treatment of existing cardiovascular risk factors, including hypertension, dyslipidemia, and overweight. Exercise in children can also significantly improve insulin sensitivity independent of weight loss. These e fects are mediated in overweight children by increases in lean body mass relative to fat mass and associated improvements in inflammatory mediators, endothelial function, and the associated adverse hormonal milieu
Metabolic effects of diets differing in glycaemic index depend on age and endogenous GIP
Aims/hypothesis
High- vs low-glycaemic index (GI) diets unfavourably affect body fat mass and metabolic markers in rodents. Different effects of these diets could be age-dependent, as well as mediated, in part, by carbohydrate-induced stimulation of glucose-dependent insulinotrophic polypeptide (GIP) signalling.
Methods
Young-adult (16 weeks) and aged (44 weeks) male wild-type (C57BL/6J) and GIP-receptor knockout (Gipr −/− ) mice were exposed to otherwise identical high-carbohydrate diets differing only in GI (20–26 weeks of intervention, n = 8–10 per group). Diet-induced changes in body fat distribution, liver fat, locomotor activity, markers of insulin sensitivity and substrate oxidation were investigated, as well as changes in the gene expression of anorexigenic and orexigenic hypothalamic factors related to food intake.
Results
Body weight significantly increased in young-adult high- vs low-GI fed mice (two-way ANOVA, p < 0.001), regardless of the Gipr genotype. The high-GI diet in young-adult mice also led to significantly increased fat mass and changes in metabolic markers that indicate reduced insulin sensitivity. Even though body fat mass also slightly increased in high- vs low-GI fed aged wild-type mice (p < 0.05), there were no significant changes in body weight and estimated insulin sensitivity in these animals. However, aged Gipr −/− vs wild-type mice on high-GI diet showed significantly lower cumulative net energy intake, increased locomotor activity and improved markers of insulin sensitivity.
Conclusions/interpretation
The metabolic benefits of a low-GI diet appear to be more pronounced in younger animals, regardless of the Gipr genotype. Inactivation of GIP signalling in aged animals on a high-GI diet, however, could be beneficial
Reduction in BACE1 decreases body weight, protects against diet-induced obesity and enhances insulin sensitivity in mice
Insulin resistance and impaired glucose homoeostasis are important indicators of Type 2 diabetes and are early risk factors of AD (Alzheimer's disease). An essential feature of AD pathology is the presence of BACE1 (β-site amyloid precursor protein-cleaving enzyme 1), which regulates production of toxic amyloid peptides. However, whether BACE1 also plays a role in glucose homoeostasis is presently unknown. We have used transgenic mice to analyse the effects of loss of BACE1 on body weight, and lipid and glucose homoeostasis. BACE1−/− mice are lean, with decreased adiposity, higher energy expenditure, and improved glucose disposal and peripheral insulin sensitivity than wild-type littermates. BACE1−/− mice are also protected from diet-induced obesity. BACE1-deficient skeletal muscle and liver exhibit improved insulin sensitivity. In a skeletal muscle cell line, BACE1 inhibition increased glucose uptake and enhanced insulin sensitivity. The loss of BACE1 is associated with increased levels of UCP1 (uncoupling protein 1) in BAT (brown adipose tissue) and UCP2 and UCP3 mRNA in skeletal muscle, indicative of increased uncoupled respiration and metabolic inefficiency. Thus BACE1 levels may play a critical role in glucose and lipid homoeostasis in conditions of chronic nutrient excess. Therefore strategies that ameliorate BACE1 activity may be important novel approaches for the treatment of diabetes
Associations of Adiponectin with Adiposity, Insulin Sensitivity, and Diet in Young, Healthy, Mexican Americans and Non-Latino White Adults.
Low circulating adiponectin levels may contribute to higher diabetes risk among Mexican Americans (MA) compared to non-Latino whites (NLW). Our objective was to determine if among young healthy adult MAs have lower adiponectin than NLWs, independent of differences in adiposity. In addition, we explored associations between adiponectin and diet. This was an observational, cross-sectional study of healthy MA and NLW adults living in Colorado (U.S.A.). We measured plasma total adiponectin, adiposity (BMI, and visceral adipose tissue), insulin sensitivity (IVGTT), and self-reported dietary intake in 43 MA and NLW adults. Mean adiponectin levels were 40% lower among MA than NLW (5.8 ± 3.3 vs. 10.7 ± 4.2 µg/mL, p = 0.0003), and this difference persisted after controlling for age, sex, BMI, and visceral adiposity. Lower adiponectin in MA was associated with lower insulin sensitivity (R² = 0.42, p < 0.01). Lower adiponectin was also associated with higher dietary glycemic index, lower intake of vegetables, higher intake of trans fat, and higher intake of grains. Our findings confirm that ethnic differences in adiponectin reflect differences in insulin sensitivity, but suggest that these are not due to differences in adiposity. Observed associations between adiponectin and diet support the need for future studies exploring the regulation of adiponectin by diet and other environmental factors
Short communication:Supplementation of fructo-oligosaccharides does not improve insulin sensitivity in heavy veal calves fed different sources of carbohydrates
Heavy veal calves (4–6 mo old) often develop problems with insulin sensitivity. This could lead to metabolic disorders and impaired animal growth performance. Studies in various animal species have shown that the supplementation of short-chain fructo-oligosaccharides (scFOS) can improve insulin sensitivity. We therefore studied the effects of scFOS supplementation on insulin sensitivity in heavy veal calves. Forty male Holstein-Friesian calves (BW = 190 ± 2.9 kg; age = 162 ± 1.4 d at the start of the trial) were fed either a control milk replacer (MR) diet or a diet in which one-third of the lactose was replaced by glucose, fructose, or glycerol for 10 wk prior to the start of the trial. At the start of the trial, calves were subjected to a frequently sampled intravenous glucose tolerance test to assess whole-body insulin sensitivity (muscle and hepatic insulin sensitivity). Calves within each dietary treatment group were ranked based on their insulin sensitivity value. Half of the calves received scFOS (12 mg/kg of BW) with the MR for 6 wk (supplementation was equally distributed over the insulin sensitivity range). Subsequently, a second frequently sampled intravenous glucose tolerance test was conducted to assess the effect of scFOS. In addition, fasting plasma levels of glucose, insulin, triglycerides, and cholesterol were determined to calculate the quantitative insulin sensitivity check index and triglyceride:high-density lipoprotein cholesterol ratio (fasting indicators of insulin sensitivity). Whole-body insulin sensitivity was low at the start of the trial and remained low in all groups [1.0 ± 0.1 and 0.8 ± 0.1 (mU/L)−1 · min−1 on average, respectively]. Supplementation of scFOS did not improve insulin sensitivity in any of the treatment groups. The quantitative insulin sensitivity check index and the triglyceride:high-density lipoprotein cholesterol ratio also did not differ between scFOS and non-scFOS calves and averaged 0.326 ± 0.003 and 0.088 ± 0.004, respectively, at the end of the trial. We conclude that scFOS supplementation does not improve insulin sensitivity in heavy veal calves regardless of the carbohydrate composition of the MR. This is in contrast to other animals (e.g., dogs and horses), where scFOS supplementation did improve insulin sensitivity. The absence of an effect of scFOS might be related to the dosage or to metabolic differences between ruminants and nonruminants. Increasing evidence indicates that dietary interventions in veal calves have little or no effect on insulin sensitivity, possibly because of low levels of insulin sensitivity
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