Insulin Sensitivity In Obese Subjects Research Articles

Changing the dietary composition improves inflammation but not adipocyte thermogenesis in diet-induced obese mice

Pronounced weight loss was shown to improve adipocyte dysfunction and insulin sensitivity in obese subjects. While bariatric surgery is frequently accompanied by adverse side effects, weight loss due to caloric restriction is often followed by weight regain. Here we aimed to determine whether switching the diet from a metabolically harmful Western type diet to a balanced standard diet is sufficient to reverse adipocyte dysfunction in diet-induced obese mice.Male C57BL/6 mice were fed a Western diet for 10 weeks and afterwards switched to a standard diet for eight more weeks (WD/SD mice) or continued to be fed a Western diet (WD/WD mice) ad libitum. Mice fed SD for 18 weeks served as control group (SD/SD). Insulin sensitivity was similar in WD/SD and SD/SD mice despite increased body weight in WD/SD mice. Beiging markers Ucp-1, Cidea and Cox8b were drastically reduced in subcutaneous adipose tissue of WD/SD mice when compared with SD/SD mice. Also, in brown adipose tissue morphologic features and markers of thermogenesis were still altered in both WD/SD and WD/WD mice. However, adipocyte size, Hif1α and macrophage infiltration were significantly lower in both, brown and white adipose tissues of WD/SD compared to WD/WD mice and additionally, a shift toward anti–inflammatory M2 phenotype was found in WD/SD mice only.In conclusion our data suggest that switching the diet is sufficient to improve adipose tissue inflammation, while western diet negatively affects thermogenic capacity of brown adipose tissue, and inhibits beiging of white adipose tissue in the long-term.

Exercise‐linked FNDC5/Irisin attenuates macrophage‐mediated renal inflammation in type 1 diabetes in aged mice

Diabetes is associated with chronic low-grade inflammation in the kidney. Both classically and alternately activated macrophages play key roles in diabetic nephropathy by mediating inflammatory processes and anti-inflammatory responses respectively. Physical activity is known to modulate innate immune function, indeed exercise training is reported to reduce low-grade inflammation and improve insulin sensitivity in obese subjects. FNDC5 is a myokine secreted by skeletal muscles during exercise and the cleavage of its extracellular domain yields Irisin. In vitro studies have demonstrated that Irisin exhibits anti-inflammatory properties in adipose tissues and RAW 264.7 cells. The purpose of our study was to investigate the effect of exercise induced FNDC5/Irisin on inflammation and damage of aged kidney in type I diabetes. C57BL/6-Ins2Akita/J (Type 1 diabetes, Akita) and C57BL/6J (Wild type, WT) mice aged 54 - 56 weeks underwent 16-week exercise training of 280 m run on treadmill at speed of 7m/min. for 5 days/week for 2 weeks and increased to 12 m/min. for the remaining 14 weeks. FNDC5/Irisin was upregulated in the kidneys of WT and Akita exercise groups but to a greater magnitude in the WT. Sedentary Akita mice kidneys showed increased macrophage recruitment and M1 macrophages (CCL2, CXCL2, and CD86+/CD40+ cells) and inflammatory cytokine production. In contrast, Akita mice undergoing exercise training increased anti-inflammatory profile and M2 phenotype polarization (CD206+ cells). Exercise induced changes were associated with robust activation of AMPK and MAPK signaling in Akita mice. In comparison to sedentary group, exercise training reduced renal resistive index, improved cortical blood flow and glomerular filtration rate in WT and Akita mice. Taken together, our results suggest that exercise training and Irisin secretion protects the aged kidney from type 1 diabetes induced damage by reducing macrophage-mediated inflammation.

The effects of 3 weeks of oral glutathione supplementation on whole body insulin sensitivity in obese males with and without type 2 diabetes: a randomized trial.

The effect of oral glutathione (GSH) supplementation was studied in obese subjects with and without type 2 diabetes (T2DM) on measures of glucose homeostasis and markers of oxidative stress. Twenty subjects (10 patients with T2DM and 10 obese subjects) were recruited for the study, and randomized in a double-blinded placebo-controlled manner to consume either 1000 mg GSH per day or placebo for 3 weeks. Before and after the 3 weeks insulin sensitivity was measured with the hyperinsulinemic-euglycemic clamp and a muscle biopsy was obtained to measure GSH and skeletal muscle mitochondrial hydrogen peroxide (H2O2) emission rate. Whole body insulin sensitivity increased significantly in the GSH group. Skeletal muscle GSH was numerically increased (∼19%) in the GSH group; no change was seen in GSH to glutathione disulfide ratio. Skeletal muscle mitochondrial H2O2 emission rate did not change in response to the intervention and neither did the urinary excretion of the RNA oxidation product 8-oxo-7,8-dihydroguanosine or the DNA oxidation product 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), although 8-oxodG decreased as a main effect of time. Oral GSH supplementation improves insulin sensitivity in obese subjects with and without T2DM, although it does not alter markers of oxidative stress. The study has been registered in clinicaltrials.gov (NCT02948673). Novelty: Reduced glutathione supplementation increases insulin sensitivity in obese subjects with and without T2DM. H2O2 emission rate from skeletal muscle mitochondria was not affected by GSH supplementation.

181-OR: Effect of Sevelamer and a Synbiotic on Insulin Sensitivity in Obese Individuals

The human gut and its microbial content (microbiome) may contribute to the pathogenesis of obesity, insulin resistance and type 2 diabetes. Possible mechanisms include altered bacterial profile, increased intestinal permeability, and elevated bacterial lipopolysaccharide (LPS) leading to low-grade systemic inflammation termed metabolic endotoxemia. We hypothesized that two interventions with putative LPS-lowering effects, sevelamer and a synbiotic (combination pre- and probiotic), would improve peripheral insulin sensitivity in obese subjects. Based upon pre-clinical studies, sevelamer is reported to sequester LPS in the GI tract, whereas a synbiotic of Bifidobacterium longum plus oligofructose can improve intestinal barrier integrity. We randomized 22, normal glucose tolerant (NGT), lean (15F/7M, BMI=23.0, age=45.4yr, A1c=5.3%) and 28 NGT, obese subjects (20F/8M, BMI=32.7, age=51.9yr, A1c=5.5%) to receive oral sevelamer, synbiotic or placebo daily for 28 days. Insulin sensitivity (euglycemic clamp), cholesterol, endotoxemia (LPS, LBP, CD14), and intestinal permeability (lactulose/mannitol ratio, zonulin) were assessed before and after intervention. Obese subjects had reduced baseline insulin sensitivity compared to lean subjects (M value, -28.6%, p=0.0001 based on 2-sample t-test). Generalized estimating equation analysis showed that sevelamer increased insulin sensitivity (M value, +25.6%, p=0.022) and lowered plasma LDL (-16.4%, p=0.016) in obese subjects compared to placebo-treated obese subjects. Synbiotic did not significantly alter insulin sensitivity or lipids compared to placebo in obese subjects. Lean subjects saw no change in insulin sensitivity with either treatment. Neither treatment significantly altered plasma LPS or intestinal permeability in lean or obese subjects. In conclusion, sevelamer improves insulin sensitivity and LDL in obese subjects, and this effect is mostly independent of parameters of endotoxemia and intestinal permeability. Disclosure E. Baeuerle: None. H. Liang: None. V. Ganapathy: None. R. Fernandez: None. N. Sathavarodom: None. C. Wang: None. S.E. Espinoza: None. N. Musi: None. Funding American Diabetes Association (7-13-GSK-01 to N.M.); National Institutes of Health (T32GM113896)

Hypoxia and exercise interactions on skeletal muscle insulin sensitivity in obese subjects with metabolic syndrome: results of a randomized controlled trial.

Physical activity improves insulin sensitivity in obesity. Hypoxia training is claimed to augment this effect. We tested the hypothesis that normobaric hypoxia training would improve insulin sensitivity in obese patients with metabolic syndrome. In a randomized controlled trial, 23 obese men with metabolic syndrome who were not informed of the FiO2 conditions underwent a 6-week physical exercise intervention under ambient (n = 11; FiO2 21%) conditions or hypoxia (n = 12; FiO2 15%) using a normobaric hypoxic chamber. Three 60-min sessions of interval training were performed each week at 60% of individual V̇O2max. Assessment of myocellular insulin sensitivity by euglycemic hyperinsulinemic clamp was performed in 21 of these subjects before and after 6 weeks of training. Comprehensive phenotyping also included biopsies of subcutaneous adipose tissues. The intermittent moderate physical exercise protocol did not substantially change the myocellular insulin sensitivity within 6 weeks under normoxic conditions (ISIClamp: 0.035 (IQR 0.016-0.075) vs. 0.037 (IQR 0.026-0.056) mg* kg-1 *min-1/(mU* l-1); p = 0.767). In contrast, ISIClamp improved during hypoxia training (0.028 (IQR 0.018-0.035) vs. 0.038 (IQR 0.024-0.060) mg * kg-1 *min-1/(mU *l-1); p < 0.05). Between group comparison of ISIClamp change revealed a small difference between groups (Cohen's d = 0.26). Within the hypoxic group, improvement of ISIClamp during training was associated with individual increase of circulating vascular endothelial growth factor (VEGF) levels (r = 0.678, p = 0.015), even if mean VEGF levels were not modified by any training condition. Atrial natriuretic peptide (ANP) system components were not associated with increased ISIClamp during hypoxic training. Physical training under hypoxic conditions could partially augment the favorable effects of exercise alone on myocellular insulin sensitivity in obese men with metabolic syndrome. Concomitant changes in VEGF might represent an underlying pathophysiological mechanism.

Fecal Microbiota Transplantation: a Future Therapeutic Option for Obesity/Diabetes?

The aim of this review is to summarize the current data available on the metabolic effects of fecal microbiota transplantation (FMT) including obesity and glucose metabolism in humans. Gut microbiota dysbiosis is a frequent characteristic observed in obesity and related metabolic diseases. Pieces of evidence mostly generated in mouse models suggest that rescuing this dysbiosis associates with improved metabolism. In humans, dietary or bariatric surgery interventions are often accompanied by complete or partial restoration of this dysbiosis together with weight reduction and metabolic amelioration. FMT is an interesting option to modify gut microbiota and has been associated with improved clinical outcomes, albeit only used in routine care for Clostridium difficile infection. However, there are only limited data on using FMT in the metabolic context. FMT from lean donors significantly improves insulin sensitivity in obese subjects with metabolic syndrome. However, there is a wide range of clinical responses. Interestingly in subjects with high microbial gene richness at baseline and when FMT donors that are metabolically compromised are used, no metabolic improvement is seen. Moreover, more studies evaluating the effect of FMT in patients with overt type 2 diabetes are warranted. Furthermore, interventions (in the receiver prior to FMT) aiming to enhance FMT response also need evaluation.

2102-P: Upregulation of Adipose Tissue APOE Expression by ω3PUFA Supplementation Associates with Decreased Plasma FFA Levels and Improves Insulin Sensitivity in Obese Subjects

Inflammation of adipose tissue (AT) is key for the development of insulin resistance (IR) in obesity. We previously showed that 3 months supplementation of fish oil (FO, 4g/day), a well-known anti-inflammatory agent, induced 25% improvement in glucose disposal during euglycemic-hyperinsulinemic clamp in 13 obese, insulin resistant subjects (ADA abstract Hernandez J., et al 2017). To explore the mechanism(s) linked to this improvement, we first performed a microarray analysis of subcutaneous (SC) AT samples pre and post FO supplementation. Functional analysis indicated anti-inflammatory pathways as the principal pathways to be enriched after FO supplementation. We identified APOE (1.87 Fold Change (FC) Post vs. Pre-FO, P=0.004) among the most significantly enhanced genes, as APOE was common to the top 5 enriched anti-inflammatory pathways. RT-PCR analysis confirmed the changes in expression levels of several genes in these pathways including APOE, APOC1, MS4A6E, MMP9, MMP7, DEFB132, C1QTNF7, and POPDC3, thereby validating the microarray findings. Plasma and SC AT RT-PCR analysis showed significantly decreased inflammatory markers (IL1B: -0.28 FC, P=0.04, MCP1: -0.44 FC, P=0.04, CD68: -0.36 FC P=0.01) post vs. pre-FO. Additionally, mRNA adiponectin levels increased (FC +0.45 Post vs. Pre, P=0.02), while leptin decreased (FC -.030 Post vs. Pre, P=0.02). Furthermore, ω3PUFA supplementation significantly reduced plasma FFA levels (Post-FO: 0.578+0.061mM vs. Pre-FO: 0.719 +0.055mM P&amp;lt;0.05). Taken together, our data suggests that ω3PUFA supplementation-induced improvement of insulin sensitivity in obese, insulin resistant subjects is attributed to the reduction of plasma FFA levels. This then associates with inhibition of inflammatory processes mediated by APOE. Additional studies are needed to further analyze the mechanism(s) linking FO to AT APOE gene expression, inflammation and insulin sensitivity. Disclosure C. Rau: None. T. Li: None. J.D. Hernandez: None. M.Y. Masuda: None. X. Zhang: None. P. Wang: None. D.K. Coletta: None. E. DeFilippis: None. Funding Arizona Department of Health Services (14-00003606); Kathryn H. and Roger Penske Career Development Award

The Shape of the Glucose Response Curve during an Oral Glucose Tolerance Test Was Associated with Muscle Insulin Sensitivity and Visceral Fat Accumulation in Nonobese Healthy Men

Previous studies reported that the shape of glucose response curve during an oral glucose tolerance test (OGTT) could be a marker of insulin sensitivity in obese subjects. The biphasic response curve was defined by a second rise in glucose concentration of &amp;gt;4.5mg/dl after the decline in glucose during OGTT and subjects with biphasic response curve were insulin sensitive and had low risk of type 2 diabetes compared with subjects with monophasic response curve. While type 2 diabetes is often developed in non-obese Asians, it is still unclear whether the subjects with biphasic response curve are also insulin sensitive in non-obese healthy men. To clarify this, we studied 49 non-obese (BMI&amp;lt;25 kg/m2) healthy Japanese men. We evaluated insulin sensitivity in muscle and liver by 2-step hyperinsulinemic euglycemic clamp. We also measured ectopic fat in muscle and liver and subcutaneous and viscera fat areas by 1H-MRS and MRI, respectively. Based on the shape of glucose response curve during OGTT, we divided the subjects into monophasic (n=31) and biphasic group (n=18). The 60- and 90-min glucose levels were significantly lower in biphasic group than monophasic group (60-min:157.5±30.9 vs. 126.4±31.3mg/dl, p&amp;lt;0.01, 90-min:123.4±23.4 vs. 103.8±20.6mg/dl, p&amp;lt;0.01), while glucose levels at other time points and insulinogenic index were comparable between the groups. In addition, biphasic group showed lower visceral fat area (82.7±27.8 vs. 62.6±24.2 cm2, P=0.014) and higher muscle insulin sensitivity (0.22±0.vs. 0.27±0.09 mg/kg FFM·min-1 ·μU-1·ml, P&amp;lt;0.020) compared with monophasic group. Ectopic fat accumulation in muscle and liver, subcutaneous fat area and hepatic insulin sensitivity were comparable between the groups. In conclusion, biphasic glucose response curve is a marker of elevated muscle insulin sensitivity with less visceral fat in non-obese Japanese healthy men. Disclosure H. Kaga: None. Y. Tamura: None. K. Takeno: None. S. Kakehi: None. Y. Someya: None. R. Suzuki: None. S. Kadowaki: None. D. Sugimoto: None. Y. Furukawa: None. T. Funayama: None. R. Kawamori: None. H. Watada: Advisory Panel; Self; AstraZeneca. Consultant; Self; Astellas Pharma US, Inc., AstraZeneca, Boehringer Ingelheim GmbH, Daiichi Sankyo Company, Limited, Sumitomo Dainippon Pharma Co., Ltd., Eli Lilly and Company, Kissei Pharmaceutical Co., Ltd., Kowa Pharmaceuticals America, Inc., Kyowa Hakko Kirin Co., Ltd., Merck Sharp &amp; Dohme Corp., Mitsubishi Tanabe Pharma Corporation, Novo Nordisk A/S, Novartis AG, Ono Pharmaceutical Co., Ltd., Sanofi, Sanwa Kagaku Kenkyusho Co., Ltd., Takeda Development Center Asia, Pte. Ltd.. Research Support; Self; Abbott, Astellas Pharma US, Inc., AstraZeneca, Bayer AG, Benefit One Health Care Co., Ltd., Boehringer Ingelheim GmbH, Bristol-Myers Squibb Company, Daiichi Sankyo Company, Limited, Sumitomo Dainippon Pharma Co., Ltd., Eli Lilly and Company, Kissei Pharmaceutical Co., Ltd., Kowa Pharmaceuticals America, Inc., Kyowa Hakko Kirin Co., Ltd., Johnson &amp; Johnson Diabetes Institute, LLC., Merck Sharp &amp; Dohme Corp., Mitsubishi Tanabe Pharma Corporation, Mochida Pharmaceutical Co., Ltd., Nitto Boseki Co., Ltd., Novartis AG, Novo Nordisk A/S, Ono Pharmaceutical Co., Ltd., Pfizer Inc., Sanofi, Sanwa Kagaku Kenkyusho Co., Ltd., Taisho Pharmaceutical Co., Ltd., Takeda Development Center Asia, Pte. Ltd., Terumo Medical Corporation.

Serum Retinol Binding Protein 4 Was Positively Associated with Insulin Resistance and Decreased after Laparoscopic Sleeve Gastrectomy in Chinese Obese Patients

Retinol binding protein 4 (RBP4) is implicated in the regulation of energy metabolism and insulin sensitivity. Laparoscopic sleeve gastrectomy (LSG) has been proven effectively in treating T2DM and other obesity-related comorbidities. We aimed to investigate the association between RBP4 with insulin resistance and the change of RPB4 levels after laparoscopic sleeve gastrectomy (LSG) in Chinese obese patients. Eighty-two obese patients (34 males and 48 females) were enrolled and 30 subjects (10 males and 20 females) underwent LSG in this study. Anthropometric and glucose metabolic parameters were measured. Serum RBP4 levels were detected by enzyme-link immunosorbent assay. In all subjects, serum RBP4 levels were positively associated with BMI, OGTT blood glucose at 0, 30, 120, 180mins, fasting insulin, fasting C-peptide and HOMA-IR at baseline (all P&amp;lt;0.05). Moreover, HOMA-IR was significantly decreased at 3 and 6 months after LSG (all P&amp;lt;0.001). Intriguingly, serum RBP4 levels were also reduced from baseline to 3 and 6 months after LSG (from 43.20±14.27mg/l to 33.00±12.35mg/l to 31.87±9.90mg/l, all P&amp;lt;0.01). In conclusion, RBP4 is closely associated with glucose metabolism and insulin resistance in Chinese obese patients. The decreased RBP4 levels may partly account for the improved insulin sensitivity in obese subjects after LSG. Disclosure X. Wang: None. L. Li: None. C. Zhu: None. J. Gao: None. S. Qu: None.

Effects of Chronic Ethanol Intake on High‐Fat Diet Induced Metabolic Dysfunction in Mice

High‐fat diet (HFD) induced obesity is associated with insulin resistance and is a major risk factor for numerous co‐morbidities such as type II diabetes. Conflicting clinical and preclinical evidence suggests that moderate alcohol consumption improves insulin sensitivity in obese subjects, and therefore may act to protect against obesity‐related metabolic comorbidities. However, the impact of free choice ethanol (EtOH) intake and HFD consumption on insulin action and glucose homeostasis in animal models remains unclear. Therefore, the overall goal of these studies was to determine if long‐term EtOH intake may alter insulin and glucose function in a mouse model of HFD induced obesity. Six‐week old male C57Bl/6J mice were given ad libitum access to HFD (n=10; 60% calories from fat) or control diet (Chow, n=10; 10% calories from fat) for two weeks. Mice were then given increasing volumes of EtOH (3%, 7%, and 10%) over one week as an EtOH‐ramp initiation period for subsequent 24‐hour access to a two‐bottle choice of water or 10% EtOH (vol/vol, in water). Body mass, EtOH and water intake, and EtOH preference was assessed every 24 hours for six weeks. HFD mice had significantly higher body mass compared to Chow mice (p&lt;0.001). By the end of the study, Chow mice consumed significantly more EtOH than mice on HFD (p&lt;0.001) and had higher preference towards EtOH (p&lt;0.001). At the end of treatment, we measured 4‐hour fasting glucose levels and performed insulin tolerance tests (to examine the ability of intraperitoneal insulin to suppress blood glucose levels) in half of the mice in each group. These metabolic data were compared to weight and aged matched mice given HFD or Chow without EtOH access. Insulin sensitivity was significantly reduced in HFD mice (p=0.003; two‐way ANOVA), and EtOH consumption did not alter HFD‐induced insulin resistance. Furthermore, there appeared to be a trend for increased 4 hour fasting glucose levels in HFD (185.8±9.4), HFD+EtOH (176±25.9) and Chow+EtOH (177.8±21.6) groups compared to Chow alone (156.4±6.2). Together, these results suggest that moderate EtOH drinking in a two‐bottle choice model does not improve insulin sensitivity in HFD mice, but that higher levels of EtOH intake in control diet mice may cause impaired glucose homeostasis that may not be due to changes in insulin sensitivity.Support or Funding InformationPenn State Dept of Neural and Behavioral Science, NIH grants AA022937 and HL122507This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effect of caloric restriction with or without n-3 polyunsaturated fatty acids on insulin sensitivity in obese subjects: A randomized placebo controlled trial

BackgroundCaloric restriction and n-3 polyunsaturated fatty acid (PUFA) supplementation protect from some of the metabolic complications. The aim of this study was to assess the influence of a low calorie diet with or without n-3 PUFA supplementation on glucose dependent insulinotropic polypeptide (GIP) output and insulin sensitivity markers in obese subjects. MethodsObese, non-diabetic subjects (BMI 30–40kg/m2) and aged 25–65yr. were put on low calorie diet (1200–1500kcal/day) supplemented with either 1.8g/day n-3 PUFA (DHA/EPA, 5:1) (n=24) or placebo capsules (n=24) for three months in a randomized placebo controlled trial. Insulin resistance markers and GIP levels were analysed from samples obtained at fasting and during an oral glucose tolerance test (OGTT). ResultsCaloric restriction with n-3 PUFA led to a decrease of insulin resistance index (HOMA-IR) and a significant reduction of insulin output as well as decreased GIP secretion during the OGTT. These effects were not seen with caloric restriction alone. Changes in GIP output were inversely associated with changes in red blood cell EPA content whereas fasting GIP level positively correlated with HOMA-IR index. Blood triglyceride level was lowered by caloric restriction with a greater effect when n-3 PUFA were included and correlated positively with fasting GIP level. ConclusionsThree months of caloric restriction with DHA+EPA supplementation exerts beneficial effects on insulin resistance, GIP and triglycerides. General significanceCombining caloric restriction and n-3 PUFA improves insulin sensitivity, which may be related to a decrease of GIP levels.

Oxidative stress and metabolic syndrome: Effects of a natural antioxidants enriched diet on insulin resistance

Oxidative stress (OS) could play a role in metabolic syndrome-related manifestations contributing to insulin resistance (IR). The aim of the present study was to gain insight the relationships between OS, IR and other hormones involved in caloric balance, explaining the effects of a natural antioxidant-enriched diet in patients affected by metabolic syndrome. We investigated the effects of dietary antioxidants on IR, studying 53 obese (20 males and 33 females, 18-66 years old, BMI 36.3±5.5kg/m2), with IR evaluated by Homeostasis Model Assessment (HOMA)-index, comparing 4 treatments: hypocaloric dietalone (group A) or plus metformin 1000mg/daily (group B), natural antioxidants-enriched hypocaloric dietalone (group C) or plus metformin (group D). A personalized program, with calculated antioxidant intake of 800-1000mg/daily, from fruit and vegetables, was administered to group C and D. The glycemic and insulinemic response to oral glucose load, and concentrations of total-, LDL- and HDL-cholesterol, triglycerides, uric acid, C reactive protein, fT3, fT4, TSH, insulin-like growth factor 1 were evaluated before and after 3-months. Plasma Total antioxidant capacity was determined by H2O2-metmyoglobin system, which interacting with the chromogen ABTS generates a radical with latency time (LAG) proportional to antioxidant content. Despite a similar BMI decrease, we found a significant decrease of HOMA and insulin peak only in group B and D. Insulin response (AUC) showed the greatest decrease in group D (25.60±8.96%) and was significantly lower in group D vs B. No differences were observed in glucose response, lipid metabolism and TAC (expressed as LAG values). TSH values were significantly suppressed in group D vs B. These data suggest that dietary antioxidants ameliorate insulin-sensitivity in obese subjects with IR by enhancing the effect of insulin-sensitizing drugs albeit with molecular mechanisms which remain yet to be elucidated.

Effect of Plasma Uric Acid on Antioxidant Capacity, Oxidative Stress, and Insulin Sensitivity in Obese Subjects

Oxidative stress is purported to be involved in the pathogenesis of obesity-associated insulin resistance. We evaluated whether alterations in levels of circulating uric acid (UA), a systemic antioxidant, affects the following: 1) systemic (plasma and saliva) nonenzymatic antioxidant capacity (NEAC); 2) markers of systemic (urinary 8-iso-prostaglandin-F2α) and muscle (carbonylated protein content) oxidative stress; and 3) whole-body insulin sensitivity (percentage increase in glucose uptake during a hyperinsulinemic-euglycemic clamp procedure). Thirty-one obese subjects (BMI 37.1 ± 0.7 kg/m2) with either high serum UA (HUA; 7.1 ± 0.4 mg/dL; n = 15) or normal serum UA (NUA; 4.5 ± 0.2 mg/dL; n = 16) levels were studied; 13 subjects with HUA levels were studied again after reduction of serum UA levels to 0 by infusing a recombinant urate oxidase. HUA subjects had 20–90% greater NEAC, but lower insulin sensitivity (40%) and levels of markers of oxidative stress (30%) than subjects in the NUA group (all P < 0.05). Acute UA reduction caused a 45–95% decrease in NEAC and a 25–40% increase in levels of systemic and muscle markers of oxidative stress (all P < 0.05), but did not affect insulin sensitivity (from 168 ± 25% to 156 ± 17%, P = NS). These results demonstrate that circulating UA is a major antioxidant and might help protect against free-radical oxidative damage. However, oxidative stress is not a major determinant of insulin action in vivo.

PS6 - 3. Plasma acylcarnitine levels have limited predictive value for metabolic characteristics as insulin sensitivity and energy expenditure

Acylcarnitines have been implicated in diet-induced insulin resistance and type 2 diabetes mellitus. Here acylcarnitines correlate with fasting glucose levels and HbA1c. We investigated plasma acylcarnitines in relation to energy metabolism and insulin sensitivity in obese subjects before and after weight loss.

VEGF is indirectly associated with NO production and acutely increases in response to hyperglycaemia1

Eur J Clin Invest 2012; 42 (9): 967–973AbstractBackground Increased levels of vascular endothelial growth factor (VEGF) have been observed in patients with metabolic syndrome (MetS). Nitric oxide (NO) formation is reduced in MetS, but its relationship to VEGF production remains poorly defined. We evaluated the association between VEGF/NO synthesis and insulin sensitivity in obese subjects and investigated the secretory response of VEGF to an acute elevation of glucose.Materials and methods Seven healthy normal‐weight subjects, seven obese subjects without MetS and seven obese subjects with MetS were recruited. Anthropometry, body composition and cardiometabolic functions (blood pressure, glucose, insulin, triglycerides, total cholesterol, HDL‐C and VEGF) were measured, and a novel stable isotope method was used to assess in vivo rates of NO production. A frequent sampling intravenous glucose tolerance test was performed to study the dynamics of VEGF release.Results Fasting VEGF levels were significantly higher in the two obese groups compared to the control group (P for trend = 0·02), but the difference was not significant after adjustment for age. Vascular endothelial growth factor levels were associated with systolic blood pressure (ρ = 0·54; P = 0·01) and NO production (ρ = −0·44; P = 0·04). Vascular endothelial growth factor levels increased in response to acute hyperglycaemia in normal‐weight and obese subjects (P &lt; 0·001).Conclusions Vascular endothelial growth factor levels rapidly increase during hyperglycaemia and are inversely related to NO production at steady state. The potential link between the acute secretion of VEGF and atherosclerotic risk in subjects with poorly controlled glycaemia as well as the potential of lowering elevated VEGF levels by increasing NO production and/or availability warrants further investigation.

NF-κB-Inducing Kinase (NIK) Mediates Skeletal Muscle Insulin Resistance: Blockade by Adiponectin

Enhanced levels of nuclear factor (NF)-κB-inducing kinase (NIK), an upstream kinase in the NF-κB pathway, have been implicated in the pathogenesis of chronic inflammation in diabetes. We investigated whether increased levels of NIK could induce skeletal muscle insulin resistance. Six obese subjects with metabolic syndrome underwent skeletal muscle biopsies before and six months after gastric bypass surgery to quantitate NIK protein levels. L6 skeletal myotubes, transfected with NIK wild-type or NIK kinase-dead dominant negative plasmids, were treated with insulin alone or with adiponectin and insulin. Effects of NIK overexpression on insulin-stimulated glucose uptake were estimated using tritiated 2-deoxyglucose uptake. NF-κB activation (EMSA), phosphatidylinositol 3 (PI3) kinase activity, and phosphorylation of inhibitor κB kinase β and serine-threonine kinase (Akt) were measured. After weight loss, skeletal muscle NIK protein was significantly reduced in association with increased plasma adiponectin and enhanced AMP kinase phosphorylation and insulin sensitivity in obese subjects. Enhanced NIK expression in cultured L6 myotubes induced a dose-dependent decrease in insulin-stimulated glucose uptake. The decrease in insulin-stimulated glucose uptake was associated with a significant decrease in PI3 kinase activity and protein kinase B/Akt phosphorylation. Overexpression of NIK kinase-dead dominant negative did not affect insulin-stimulated glucose uptake. Adiponectin treatment inhibited NIK-induced NF-κB activation and restored insulin sensitivity by restoring PI3 kinase activation and subsequent Akt phosphorylation. These results indicate that NIK induces insulin resistance and further indicate that adiponectin exerts its insulin-sensitizing effect by suppressing NIK-induced skeletal muscle inflammation. These observations suggest that NIK could be an important therapeutic target for the treatment of insulin resistance associated with inflammation in obesity and type 2 diabetes.

Reproducibility of glucose, fatty acid and VLDL kinetics and multi-organ insulin sensitivity in obese subjects with non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is associated with abnormalities in basal glucose and free fatty acid (FFA) metabolism, multi-organ insulin resistance and alterations in lipoprotein kinetics. These metabolic outcomes can be evaluated in vivo by using stable isotopically labeled tracer methods. An understanding of the reproducibility of these measures is necessary to ensure adequate statistical power in studies designed to evaluate metabolic function in subjects with NAFLD. We determined the degree of intra-individual variability of skeletal muscle, adipose tissue, and hepatic insulin sensitivity and basal plasma glucose, FFA, and very-low-density lipoprotein triglyceride and apolipoprotein B-100 (apoB-100) kinetics in eight obese subjects with NAFLD (age: 44 ± 3 years; body mass index: 38.2 ± 1.7 kg m(-2); intrahepatic triglyceride content: 24.5 ± 3.9%), by using the hyperinsulinemic-euglycemic clamp technique and stable isotope-labeled tracer methods and mathematical modeling on two separate occasions ∼2 months apart. The intra-individual variability (coefficient of variation) ranged from 6% for basal glucose production to 21% for insulin-stimulated glucose disposal (percentage increase from basal). We estimated that a 25% difference in any outcome measure can be detected with a sample size of ≤ 8 subjects for paired studies and ≤ 15 subjects per group for unpaired studies, assuming an α value of 0.05 and a β value of 0.20 (that is, 80% power). These results demonstrate that only a small number of subjects are needed to detect clinically relevant effects in insulin sensitivity and hepatic lipoprotein metabolism in obese subjects with NAFLD, and will be useful to determine appropriate sample size for future metabolic studies.

The glucose clamp reveals an association between adiponectin gene polymorphisms and insulin sensitivity in obese subjects

Results concerning the association of adiponectin gene polymorphisms (single-nucleotide polymorphisms, SNPs) with obesity, type 2 diabetes (T2DM), metabolic disorders and insulin resistance have not lead to definite conclusions. The aim of our study was to investigate a possible association between the -11391G>A and -11377C>G SNPs of adiponectin gene and measure of insulin sensitivity evaluated by the hyperinsulinemic-euglycemic clamp in a group of 'uncomplicated' obese subjects (with no associated comorbidities) (n=99, mean age 35 years) with a history of obesity lasting at least 10 years. The study of uncomplicated obese subjects, free of possible confounding factors that could interfere with insulin sensitivity, such as pharmacological treatment, provides a good model to assess insulin sensitivity per se. We observed that subjects homozygous for the G allele at locus -11391 had lower M (mg/kg min)/fat-free mass (FFM) index and adiponectin levels compared to subjects with GA+AA genotypes (P=0.002 and P=0.03, respectively) and subjects carrying the -11377G variant had lower M (mg/kg min)/FFM index and adiponectin levels compared to noncarriers (P=0.003 and P=0.03, respectively). Our results imply that the two promoter SNPs, -11391G>A and -11377C>G, of the adiponectin gene are associated with a reduced insulin sensitivity evaluated by hyperinsulinemic-euglycemic clamp in obese subjects.

Chromium picolinate improves insulin sensitivity in obese subjects with polycystic ovary syndrome

Trivalent chromium (1000 microg), as chromium picolinate, given without change in diet or activity level, caused a 38% mean improvement in glucose disposal rate in five obese subjects with polycystic ovary syndrome who were tested with a euglycemic hyperinsulinemic clamp technique. This suggests that chromium picolinate, an over-the-counter dietary product, may be useful as an insulin sensitizer in the treatment of polycystic ovary syndrome.

The Association between Plasma Adiponectin and Insulin Sensitivity in Humans Depends on Obesity

In humans, low plasma adiponectin concentrations precede a decrease in insulin sensitivity and predict type 2 diabetes independently of obesity. However, it is possible that the contribution of adiponectin to insulin sensitivity is not equally strong over the whole range of obesity. We investigated the cross-sectional association between plasma adiponectin levels and insulin sensitivity in different ranges of body fat content [expressed as percentage of body fat (PFAT)] in a large cohort of normal glucose-tolerant subjects (n = 900). All individuals underwent an oral glucose tolerance test (OGTT), and 299 subjects additionally a euglycemic hyperinsulinemic clamp. In longitudinal analyses, the association of adiponectin at baseline with change in insulin sensitivity was investigated in a subgroup of 108 subjects. In cross-sectional analyses, the association between plasma adiponectin and insulin sensitivity, adjusted for age, gender, and PFAT, depended on whether subjects were lean or obese [p for interaction adiponectin x PFAT = <0.001 (OGTT) and 0.002 (clamp)]. Stratified by quartiles of PFAT, adiponectin did not correlate significantly with insulin sensitivity in subjects in the lowest PFAT quartile (R2 = 0.10, p = 0.13, OGTT; and R2 = 0.10, p = 0.57, clamp), whereas the association in the upper PFAT quartile was rather strong (R2 = 0.36, p < 0.0001, OGTT; and R2 = 0.48, p = 0.003, clamp). In longitudinal analyses, plasma adiponectin at baseline preceded change in insulin sensitivity in obese (n = 54, p = 0.03) but not in lean (n = 54, p = 0.68) individuals. These data suggest that adiponectin is especially critical in sustaining insulin sensitivity in obese subjects. Thus, interventions to reduce insulin resistance by increasing adiponectin concentrations may be effective particularly in obese, insulin-resistant individuals.