Differential effect of gastric bypass versus sleeve gastrectomy on insulinotropic action of endogenous incretins.

OBJECTIVE: Prandial hyperinsulinemia after Roux-en-Y gastric bypass surgery (GB), and to lesser degree after sleeve gastrectomy (SG), has been attributed to rapid glucose flux from the gut and increased insulinotropic gut hormones. However, ß-cell sensitivity to exogenous incretin is reduced after GB. This study examines the effect of GB versus SG on prandial glycemia and ß-cell response to increasing concentrations of endogenous incretins. METHODS: Glucose kinetics, insulin secretion rate (ISR), and incretin responses to 50-g oral glucose ingestion were compared between ten nondiabetic participants with GB versus nine matched individuals with SG and seven nonoperated normal glucose tolerant control individuals (CN) with and without administration of 200 mg of sitagliptin. RESULTS: Fasting glucose and hormonal levels were similar among three groups. Increasing plasma concentrations of endogenous incretins by two- to three-fold diminished prandial glycemia and increased ß-cell secretion in all three groups (p < 0.05), but insulin secretion per insulin sensitivity (i.e., disposition index) was increased only in GB (p < 0.05 for interaction). However, plot of the slope of ISR (from premeal to peak values) versus plasma glucagon-like peptide-1 concentration was smaller after GB compared with SG and CN. CONCLUSIONS: After GB, increasing incretin activity augments prandial ß-cell response whereas the ß-cell sensitivity to increasing plasma concentrations of endogenous incretin is diminished.

Bariatric Surgery Alters the Postprandial Recovery From Hypoglycemia, Mediated by Cholinergic Signal.

Roux-en-Y gastric bypass (GB) and sleeve gastrectomy (SG) surgeries increase prandial insulin and glucagon secretion but reduce the endogenous glucose production (EGP) response to hypoglycemia in comparison with control subjects who had not undergone gastric surgery (CN), suggesting that parasympathetic nervous system (PNS) plays a role. Here, we investigated the effect of acute PNS blockade on the post-meal counterregulatory response to insulin-induced hypoglycemia in GB and SG compared with CN. Glucose kinetics and islet cell secretion were measured in nine subjects without diabetes with GB and seven with SG and five CN during hyperinsulinemic-hypoglycemic clamp (∼3.2 mmol/L) combined with meal ingestion on two separate days with and without intravenous atropine infusion. Glucose and hormonal levels were similar at baseline and during steady-state hypoglycemia before meal ingestion in three groups and unaffected by atropine. Atropine infusion diminished prandial systemic appearance of ingested glucose (RaO) by 30%, EGP by 40%, and glucagon response to hypoglycemia by 90% in CN. In GB or SG, blocking PNS had no effect on the RaO or meal-induced hyperglucagonemia but increased EGP in SG without any effect in GB (P < 0.05 interaction). These findings indicate that cholinergic signal contributes to the recovery from hypoglycemia by meal consumption in humans. However, bariatric surgery dissipates PNS-mediated physiologic responses to hypoglycemia in the fed state. ARTICLE HIGHLIGHTS: Rerouted gut after Roux-en-Y gastric bypass (GB) and, to a lesser degree, after sleeve gastrectomy (SG) leads to larger glucose excursion and lower nadir glucose, predisposing individuals to hypoglycemia. Despite prandial hyperglucagonemia, endogenous glucose production response to hypoglycemia is reduced after GB or SG. Parasympathetic nervous system (PNS) activity plays a key role in regulation of glucose kinetics and islet cell function. We examined the effect of acute PNS blockade on counterregulatory glucose and islet cell response to meal ingestion during insulin-induced hypoglycemia among GB, SG, and control subjects who had not had gastric surgery. Our findings demonstrate that cholinergic signal is critical in the recovery from hypoglycemia by meal ingestion in humans who have not had gastric surgery, although prandial PNS-mediated physiologic responses to hypoglycemia are differentially changed by GB and SG.

Insulinotropic effect of endogenous incretins is greater after gastric bypass than sleeve gastrectomy despite diminished beta-cell sensitivity to plasma incretins.

Background/Aims: Prandial hyperinsulinemia after Roux-en Y gastric bypass surgery (GB), and to lesser degree after sleeve gastrectomy (SG), has been attributed to rapid glucose flux from the gut and increased insulinotropic gut hormones. However, ß-cell sensitivity to exogenous incretin is markedly reduced after GB. This study examines the effect of GB versus SG on prandial glycemia and ß-cell response to increasing concentrations of endogenous incretins. Methods: Glucose kinetics, insulin secretion rate (ISR), and incretin responses to 50-gram oral glucose ingestion were compared between 10 non-diabetic subjects with GB versus 9 matched individuals with SG and 7 non-operated normal glucose tolerant controls (CN) on two days with and without administration of 200 mg sitagliptin. Results: Fasting glucose and hormonal levels were similar among 3 groups. Increasing plasma concentrations of endogenous incretins by 2-3-fold diminished post-OGTT glycemia and increased ß-cell secretion in all 3 groups (p<0.05), but insulin secretion per insulin sensitivity (i.e., disposition index) was increased only in GB (p<0.05 for interaction). As a result, sitagliptin administration led to hypoglycemia in 3 of 10 GB. Yet, plot of the slope of ISR versus the increase in endogenous incretin concentration was smaller after GB compared to both SG and CN. Conclusion: Augmented glycemic-induced ß-cell response caused by enhanced incretin activity is unique to GB and not shared with SG. However, the ß-cell sensitivity to increasing concentrations of endogenous incretin is smaller after bariatric surgery, particularly after GB, compared to non-operated controls, indicating a long-term adaptation of gut-pancreas axis after these procedures. HIGHLIGHTS: What is known?: Glycemic effects of gastric bypass (GB) and sleeve gastrectomy (SG) is attributed to rapid nutrient flux and enhanced insulinotropic effects of gut hormones but ß-cell sensitivity to exogenous GLP-1 or GIP is diminished after GB. What the present findings add?: Post-OGTT ß-cell sensitivity to enhanced endogenous incretins by DPP4i is markedly reduced in bariatric subjects versus non-operated controls, and yet insulin secretory response (disposition index) is increased leading to hypoglycemia in GB and not SG. Significance?: Blunted sensitivity to GLP-1 may represent ß-cell adaptation to massive elevation in GLP-1 secretion following bariatric surgery to protect against hypoglycemia.The differential effect of enhanced concentrations of incretins on post-OGTT insulin response (disposition index) among GB versus SG highlights a distinct adaptive process among the two procedures.Augmented insulinotropic effects of gut hormones on postprandial insulin secretory response after GB despite a reduced beta-cell sensitivity to plasma concentrations of GLP-1 makes a case for non-hormonal mechanisms of GLP-1 action after GB.Better understanding of long-term effects of bariatric surgery on gut-pancreas axis activity is critical in development of GLP-1-based strategies to address glucose abnormalities (both hyperglycemia and hypoglycemia) in these settings.

Pioglitazone corrects dysregulation of skeletal muscle mitochondrial proteins involved in ATP synthesis in type 2 diabetes.

CONTEXT: In this study, we aimed to identify the determinants of mitochondrial dysfunction in skeletal muscle (SKLM) of subjects with type 2 diabetes (T2DM), and to evaluate the effect of pioglitazone (PIO) on SKLM mitochondrial proteome. METHODS: Two different groups of adults were studied. Group I consisted of 8 individuals with normal glucose tolerance (NGT) and 8 with T2DM, subjected to SKLM mitochondrial proteome analysis by 2D-gel electrophoresis followed by mass spectrometry-based protein identification. Group II included 24 individuals with NGT and 24 with T2DM, whose SKLM biopsies were subjected to immunoblot analysis. Of the 24 subjects with T2DM, 20 were randomized to receive placebo or PIO (15 mg daily) for 6 months. After 6 months of treatment, SKLM biopsy was repeated. RESULTS: Mitochondrial proteomic analysis on Group I revealed that several mitochondrial proteins involved in oxidative metabolism were differentially expressed between T2DM and NGT groups, with a downregulation of ATP synthase alpha chain (ATP5A), electron transfer flavoprotein alpha-subunit (ETFA), cytochrome c oxidase subunit VIb isoform 1 (CX6B1), pyruvate dehydrogenase protein X component (ODPX), dihydrolipoamide dehydrogenase (DLDH), dihydrolipoamide-S-succinyltransferase (DLST), and mitofilin, and an up-regulation of hydroxyacyl-CoA-dehydrogenase (HCDH), 3,2-trans-enoyl-CoA-isomerase (D3D2) and delta3,5-delta2,4-dienoyl-CoA-isomerase (ECH1) in T2DM as compared to NGT subjects. By immunoblot analysis on SKLM lysates obtained from Group II we confirmed that, in comparison to NGT subjects, those with T2DM exhibited lower protein levels of ATP5A (-30%, P = 0.006), ETFA (-50%, P = 0.02), CX6B1 (-30%, P = 0.03), key factors for ATP biosynthesis, and of the structural protein mitofilin (-30%, P = 0.01). T2DM was associated with a reduced abundance of the enzymes involved in the Krebs cycle DLST and ODPX (-20%, P ≤ 0.05) and increased levels of HCDH and ECH1, enzymes implicated in the fatty acid catabolism (+30%, P ≤ 0.05). In subjects with type 2 diabetes treated with PIO for 6 months we found a restored SKLM protein abundance of ATP5A, ETFA, CX6B1, and mitofilin. Moreover, protein levels of HCDH and ECH1 were reduced by -10% and - 15% respectively (P ≤ 0.05 for both) after PIO treatment. CONCLUSION: Type 2 diabetes is associated with reduced levels of mitochondrial proteins involved in oxidative phosphorylation and an increased abundance of enzymes implicated in fatty acid catabolism in SKLM. PIO treatment is able to improve SKLM mitochondrial proteomic profile in subjects with T2DM.

Reduced skeletal muscle phosphocreatine concentration in type 2 diabetic patients: a quantitative image-based phosphorus-31 MR spectroscopy study.

Mitochondrial function has been examined in insulin-resistant (IR) states including type 2 diabetes mellitus (T2DM). Previous studies using phosphorus-31 magnetic resonance spectroscopy (31P-MRS) in T2DM reported results as relative concentrations of metabolite ratios, which could obscure differences in phosphocreatine ([PCr]) and adenosine triphosphate concentrations ([ATP]) between T2DM and normal glucose tolerance (NGT) individuals. We used an image-guided 31P-MRS method to quantitate [PCr], inorganic phosphate [Pi], phosphodiester [PDE], and [ATP] in vastus lateralis (VL) muscle in 11 T2DM and 14 NGT subjects. Subjects also received oral glucose tolerance test, euglycemic insulin clamp, 1H-MRS to measure intramyocellular lipids [IMCL], and VL muscle biopsy to evaluate mitochondrial density. T2DM subjects had lower absolute [PCr] and [ATP] than NGT subjects (PCr 28.6 ± 3.2 vs. 24.6 ± 2.4, P < 0.002, and ATP 7.18 ± 0.6 vs. 6.37 ± 1.1, P < 0.02) while [PDE] was higher, but not significantly. [PCr], obtained using the traditional ratio method, showed no significant difference between groups. [PCr] was negatively correlated with HbA1c ( r = -0.63, P < 0.01) and fasting plasma glucose ( r = -0.51, P = 0.01). [PDE] was negatively correlated with Matsuda index ( r = -0.43, P = 0.03) and M/I ( r = -0.46, P = 0.04), but was positively correlated with [IMCL] ( r = 0.64, P < 0.005), HbA1c, and FPG ( r = 0.60, P = 0.001). To summarize, using a modified, in vivo quantitative 31P-MRS method, skeletal muscle [PCr] and [ATP] are reduced in T2DM, while this difference was not observed with the traditional ratio method. The strong inverse correlation between [PCr] vs. HbA1c, FPG, and insulin sensitivity supports the concept that lower baseline skeletal muscle [PCr] is related to key determinants of glucose homeostasis.

The potential role of the osteopontin-osteocalcin-osteoprotegerin triad in the pathogenesis of prediabetes in humans.

AIMS: To examine the relationship between hormones involved in bone remodeling and glucose metabolism alterations in prediabetes. METHODS: Individuals (n = 43) with NGT (BMI = 31.1 ± 1.1 kg/m2) and individuals (n = 79) with impaired glucose regulation (IGR) (BMI = 31.9 ± 1.2 kg/m2) including subjects with IFG, IGT, and IFG-IGT underwent OGTT and DXA. Osteopontin (OPN), osteocalcin (OCN), osteoprotegerin (OPG), and PTH levels were measured at fasting. Beta-cell function was calculated using C-peptide deconvolution. Dynamic indexes of insulin sensitivity were calculated from OGTT. A subgroup underwent to a euglycemic hyperinsulinemic clamp with 3-3H-glucose to estimate the endogenous glucose production (EGP) and insulin-mediated body glucose disposal (TGD/SSPI). RESULTS: OPN was higher in IGR compared to NGT (5.3 ± 0.5 vs. 3.3 ± 0.2 µg/mL; p = 0.008) and in isolated IGT compared to IFG and IFG-IGT (6.3 ± 0.5 vs. 4.5 ± 0.3 and 5.4 ± 0.5 µg/mL; p = 0.02). OCN was similar in IFG and NGT but lower in IGT and IFG-IGT compared to NGT (7.2 ± 0.3 and 5.4 ± 0.2 vs. 8.3 ± 0.3 ng/mL; p < 0.01). OPN was positively correlated with HbA1c, fasting and 2 h plasma glucose and PTH. OCN was negatively correlated with body fat, 2 h plasma glucose, insulin and positively correlated with Stumvoll index. OPG correlated with TGD/SSPI (r = - 0.29; p < 0.05), EGP, and hepatic insulin resistance index in IGR (r = 0.51, r = 0.43; p < 0.01). There was no correlation between PTH and insulin sensitivity or Beta-cell function parameters. CONCLUSIONS: In prediabetes, hormones known to be involved in bone remodeling may affect glucose metabolism before overt T2DM occurs with tissue-specific mechanisms.

Islet amyloid polypeptide response to maximal hyperglycemia and arginine is altered in impaired glucose tolerance and type 2 diabetes mellitus.

AIMS: Pancreatic islet amyloid deposition is a characteristic feature of type 2 diabetes mellitus (T2DM). Islet amyloid polypeptide (IAPP) is co-secreted with insulin, but its secretion profile and relationship to insulin and C-peptide in response to glucose and non-glucose stimuli has not been clearly defined. METHODS: Forty subjects (13 NGT, 12 IGT and 15 T2DM) participated in an OGTT and two-step hyperglycemic (225 and 400 mg/dl) clamp (80 min/step) followed by an IV arginine bolus. Acute insulin (AIR), C-peptide (ACPR) and IAPP (AIAR) responses during each hyperglycemic step and following arginine (AIRArg) were assessed. RESULTS: AIR and ACPR during both hyperglycemic steps and after arginine progressively decreased from NGT to IGT to T2DM. Fasting IAPP concentrations were higher in T2DM compared to NGT and IGT subjects. The acute IAPP0-10 was markedly decreased only in T2DM, while the acute IAPP80-90 response during the second step (80-160 min) of hyperglycemic clamp and in response to arginine was markedly impaired in both IGT and T2DM. The ratio of IAPP/C-peptide during the first (225 mg/dl) and second step (400 mg/dl), and in response to arginine, was decreased in T2DM versus both NGT and IGT (p < 0.01). The acute IAPP0-10 correlated with ACPR0-10 (r = 0.665, p < 0.001) and AIR0-10 (r = 0.543, p < 0.001). CONCLUSIONS: Basal IAPP secretion is higher in T2DM and IGT versus NGT but is reduced in response to hyperglycemia and arginine. The IAPP/C-peptide ratio is reduced with prolonged and more severe hyperglycemia in T2DM individuals. CLINICAL TRIAL REGISTRATION: NCT00845182.

Exenatide improves both hepatic and adipose tissue insulin resistance: A dynamic positron emission tomography study.

Glucagon-like peptide 1 (GLP-1) receptor agonists (GLP-1-RAs) act on multiple tissues, in addition to the pancreas. Recent studies suggest that GLP-1-RAs act on liver and adipose tissue to reduce insulin resistance (IR). Thus, we evaluated the acute effects of exenatide (EX) on hepatic (Hep-IR) and adipose (Adipo-IR) insulin resistance and glucose uptake. Fifteen male subjects (age = 56 ± 8 years; body mass index = 29 ± 1 kg/m2 ; A1c = 5.7 ± 0.1%) were studied on two occasions, with a double-blind subcutaneous injection of EX (5 µg) or placebo (PLC) 30 minutes before a 75-g oral glucose tolerance test (OGTT). During OGTT, we measured hepatic (HGU) and adipose tissue (ATGU) glucose uptake with [18 F]2-fluoro-2-deoxy-D-glucose/positron emission tomography, lipolysis (RaGly) with [U-2 H5 ]-glycerol, oral glucose absorption (RaO) with [U-13 C6 ]-glucose, and hepatic glucose production (EGP) with [6,6-2 H2 ]-glucose. Adipo-IR and Hep-IR were calculated as (FFA0-120min ) × (Ins0-120min ) and (EGP0-120min ) × (Ins0-120min ), respectively. EX reduced RaO, resulting in reduced plasma glucose and insulin concentration from 0 to 120 minutes postglucose ingestion. EX decreased Hep-IR (197 ± 28 to 130 ± 37; P = 0.02) and increased HGU of orally administered glucose (23 ± 4 to 232 ± 89 [µmol/min/L]/[µmol/min/kg]; P = 0.003) despite lower insulin (23 ± 5 vs. 41 ± 5 mU/L; P < 0.02). EX enhanced insulin suppression of RaGly by decreasing Adipo-IR (23 ± 4 to 13 ± 3; P = 0.009). No significant effect of insulin was observed on ATGU (EX = 1.16 ± 0.15 vs. PLC = 1.36 ± 0.13 [µmol/min/L]/[µmol/min/kg]). CONCLUSION: Acute EX administration (1) improves Hep-IR, decreases EGP, and enhances HGU and (2) reduces Adipo-IR, improves the antilipolytic effect of insulin, and reduces plasma free fatty acid levels during OGTT. (Hepatology 2016;64:2028-2037).

Exenatide Regulates Cerebral Glucose Metabolism in Brain Areas Associated With Glucose Homeostasis and Reward System.

Glucagon-like peptide 1 receptors (GLP-1Rs) have been found in the brain, but whether GLP-1R agonists (GLP-1RAs) influence brain glucose metabolism is currently unknown. The study aim was to evaluate the effects of a single injection of the GLP-1RA exenatide on cerebral and peripheral glucose metabolism in response to a glucose load. In 15 male subjects with HbA1c of 5.7 ± 0.1%, fasting glucose of 114 ± 3 mg/dL, and 2-h glucose of 177 ± 11 mg/dL, exenatide (5 µg) or placebo was injected in double-blind, randomized fashion subcutaneously 30 min before an oral glucose tolerance test (OGTT). The cerebral glucose metabolic rate (CMRglu) was measured by positron emission tomography after an injection of [(18)F]2-fluoro-2-deoxy-d-glucose before the OGTT, and the rate of glucose absorption (RaO) and disposal was assessed using stable isotope tracers. Exenatide reduced RaO0-60 min (4.6 ± 1.4 vs. 13.1 ± 1.7 µmol/min ⋅ kg) and decreased the rise in mean glucose0-60 min (107 ± 6 vs. 138 ± 8 mg/dL) and insulin0-60 min (17.3 ± 3.1 vs. 24.7 ± 3.8 mU/L). Exenatide increased CMRglu in areas of the brain related to glucose homeostasis, appetite, and food reward, despite lower plasma insulin concentrations, but reduced glucose uptake in the hypothalamus. Decreased RaO0-60 min after exenatide was inversely correlated to CMRglu. In conclusion, these results demonstrate, for the first time in man, a major effect of a GLP-1RA on regulation of brain glucose metabolism in the absorptive state.

Chronic reduction of plasma free fatty acid improves mitochondrial function and whole-body insulin sensitivity in obese and type 2 diabetic individuals.

Insulin resistance and dysregulation of free fatty acid (FFA) metabolism are core defects in type 2 diabetic (T2DM) and obese normal glucose tolerant (NGT) individuals. Impaired muscle mitochondrial function (reduced ATP synthesis) also has been described in insulin-resistant T2DM and obese subjects. We examined whether reduction in plasma FFA concentration with acipimox improved ATP synthesis rate and altered reactive oxygen species (ROS) production. Eleven NGT obese and 11 T2DM subjects received 1) OGTT, 2) euglycemic insulin clamp with muscle biopsy, and 3) (1)H-magnetic resonance spectroscopy of tibialis anterior muscle before and after acipimox (250 mg every 6 h for 12 days). ATP synthesis rate and ROS generation were measured in mitochondria isolated from muscle tissue ex vivo with chemoluminescence and fluorescence techniques, respectively. Acipimox 1) markedly reduced the fasting plasma FFA concentration and enhanced suppression of plasma FFA during oral glucose tolerance tests and insulin clamp in obese NGT and T2DM subjects and 2) enhanced insulin-mediated muscle glucose disposal and suppression of hepatic glucose production. The improvement in insulin sensitivity was closely correlated with the decrease in plasma FFA in obese NGT (r = 0.81) and T2DM (r = 0.76) subjects (both P < 0.001). Mitochondrial ATP synthesis rate increased by >50% in both obese NGT and T2DM subjects and was strongly correlated with the decrease in plasma FFA and increase in insulin-mediated glucose disposal (both r > 0.70, P < 0.001). Production of ROS did not change after acipimox. Reduction in plasma FFA in obese NGT and T2DM individuals improves mitochondrial ATP synthesis rate, indicating that the mitochondrial defect in insulin-resistant individuals is, at least in part, reversible.

Pioglitazone improves glucose metabolism and modulates skeletal muscle TIMP-3-TACE dyad in type 2 diabetes mellitus: a randomised, double-blind, placebo-controlled, mechanistic study.

AIMS/HYPOTHESIS: Pioglitazone (PIO) is a peroxisome proliferator-activated receptor (PPAR)γ agonist insulin-sensitiser with anti-inflammatory and anti-atherosclerotic effects. Our objective was to evaluate the effect of low-dose PIO (15 mg/day) on glucose metabolism and inflammatory state in obese individuals with type 2 diabetes. METHODS: A randomised, double-blind, placebo-controlled, mechanistic trial was conducted on 29 patients with type 2 diabetes treated with metformin and/or sulfonylurea. They were randomised to receive PIO or placebo (PLC) for 6 months, in a 1:1 ratio. Participants were allocated to interventions by central office. All study participants, investigators and personnel performing measurements were blinded to group assignment. At baseline and after 6 months patients underwent: (1) OGTT; (2) muscle biopsy to evaluate expression of TNF-α, tissue inhibitor of metalloproteases 3 (TIMP-3) levels, TNF-α converting enzyme (TACE) expression and enzymatic activity; (3) euglycaemic-hyperinsulinaemic clamp; (4) measurement of plasma high-sensitivity C-reactive protein (hsCRP), plasminogen activator inhibitor type-1 (PAI-1), TNF-α, IL-6, monocyte chemotactic protein-1 (MCP-1), adiponectin and fractalkine (FRK). The interventions were PIO 15 mg/day vs placebo and the main outcomes measured were absolute changes in whole-body insulin sensitivity, insulin secretion and inflammatory state. RESULTS: Fifteen participants were randomized to receive PIO and 14 participants were randomized to receive PLC. Eleven participants completed the study in the PIO group and nine participants completed the study in the PLC group and were analysed. Fasting plasma glucose and HbA1c decreased modestly (p < 0.05) after PIO and did not change after PLC. M/I (insulin-stimulated whole-body glucose disposal), adipose tissue insulin resistance (IR) index, insulin secretion/IR (disposition) index and insulinogenic index improved significantly after PIO, but not after PLC. Circulating MCP-1, IL-6, FRK, hsCRP and PAI-1 levels decreased in PIO- as compared with PLC-treated patients, while TNF-α did not change. TNF-α protein expression and TACE enzymatic activity in muscle were significantly reduced by PIO but not PLC. Adiponectin levels increased significantly after PIO as compared with PLC treatment. Given that the mean TACE enzymatic activity level at baseline in the PIO group was 0.29 ± 0.07 (fluorescence units [FU]), and at end of study decreased to 0.05 vs 0.14 in the PLC group, the power to reject the null hypothesis that the population means of the PIO and PLC groups are equal after 6 months is greater than 0.80. Given that M/I was 2.41 ± 0.35 µmol kg(-1) min(-1) (pmol/l)(-1) at baseline and increased by 0.55 in the PIO and 0.17 in the PLC groups, the power to reject the null hypothesis that the population means of the PIO and PLC groups are equal after 6 months is greater than 0.85. The type I error probability associated with this test of this null hypothesis is 0.05. No serious adverse events occurred in either group. CONCLUSIONS/INTERPRETATION: Low-dose PIO (15 mg/day) improves glycaemic control, beta cell function and inflammatory state in obese patients with type 2 diabetes. TRIAL REGISTRATION: Clinical.Trial.gov NCT01223196. FUNDING: This study was funded by TAKEDA.

Medical therapy of aortic aneurysms: a pathophysiology-based approach.

One of the critical points in the pathogenesis of aortic aneurysms (AAs) is the disruption of the balance between vascular extracellular matrix (ECM) deposition and degradation. AAs are common features in some genetically determined diseases of the connective tissue, such as Marfan and Ehlers-Danlos. Acquired factors determining an enhanced inflammatory state of the arterial wall also play a key role. Previous studies have determined the role of tumor growth factor ß (TGF-ß); as a principal mediator of the pathogenesis of the alterations of the arterial wall homeostasis in AAs. The medical management of any AA is mainly focused on the use of pharmacological agents that reduce hemodynamic stress of the aortic wall, since hypertension is the major risk factor for the enlargement and rupture of the AAs. However, this is far from being a comprehensive pathophysiology-based therapeutic approach. Drugs potentially able to reduce the release of TGF-ß may play a role in the pathogenesis of the AAs. They work by improving matrix repair, decreasing the proteolytic pattern and inhibition of angiotensin-converting enzyme (ACE) as well as preventing angiotensin II-induced angiotensin type-1 receptor (AT1R) activation. A new pathophysiology-based therapeutic approach, involving the mechanisms leading to the rupture of the AAs, could represent an additional tool in combination with the current established antihypertensive therapy.

Effect of short-term free Fatty acids elevation on mitochondrial function in skeletal muscle of healthy individuals.

CONTEXT: Mitochondrial dysfunction has been proposed as an underlying mechanism in the pathogenesis of insulin resistance and type 2 diabetes mellitus. OBJECTIVE: To determine whether mitochondrial dysfunction plays a role in the free fatty acid (FFA)-induced impairment in insulin action in skeletal muscle of healthy subjects. DESIGN: Eleven lean normal glucose tolerant individuals received 8 h lipid and saline infusion on separate days with a euglycemic insulin clamp during the last 2 h. Vastus lateralis muscle biopsies were performed at baseline and after 6 h lipid or saline infusion. Inner mitochondrial membrane potential (Psi(m)) and mitochondrial mass were determined ex vivo by confocal microscopy. RESULTS: Compared with saline infusion, lipid infusion reduced whole-body glucose uptake by 22% (P < 0.05). Psi(m) decreased by 33% (P < 0.005) after lipid infusion and the decrement in Psi(m) correlated with change in plasma FFA after lipid infusion (r = 0.753; P < 0.005). Mitochondrial content and morphology did not change after lipid infusion. No significant changes in genes expression, citrate synthase activity, and total ATP content were observed after either lipid or saline infusion. CONCLUSIONS: Short-term physiological increase in plasma FFA concentration in lean normal glucose tolerant subjects induces insulin resistance and impairs mitochondrial membrane potential but has no significant effects on mitochondrial content, gene expression, ATP content, or citrate synthase activity.

Deleterious action of FA metabolites on ATP synthesis: possible link between lipotoxicity, mitochondrial dysfunction, and insulin resistance.

Insulin resistance is a characteristic feature of type 2 diabetes and obesity. Insulin-resistant individuals manifest multiple disturbances in free fatty acid (FFA) metabolism and have excessive lipid accumulation in insulin target tissues. Although much evidence supports a causal role for altered FFA metabolism in the development of insulin resistance, i.e., "lipotoxicity", the intracellular mechanisms by which elevated plasma FFA levels cause insulin resistance have yet to be completely elucidated. Recent studies have implicated a possible role for mitochondrial dysfunction in the pathogenesis of insulin resistance in skeletal muscle. We examined the effect of FFA metabolites [palmitoyl carnitine (PC), palmitoyl-coenzyme A (CoA), and oleoyl-CoA] on ATP synthesis in mitochondria isolated from mouse and human skeletal muscle. At concentrations ranging from 0.5 to 2 microM, these FFA metabolites stimulated ATP synthesis; however, above 5 microM, there was a dose-response inhibition of ATP synthesis. Furthermore, 10 microM PC inhibits ATP synthesis from pyruvate. Elevated PC concentrations (> or =10 microM) inhibit electron transport chain activity and decrease the mitochondrial inner membrane potential. These acquired mitochondrial defects, caused by a physiological increase in the concentration of FFA metabolites, provide a mechanistic link between lipotoxicity, mitochondrial dysfunction, and muscle insulin resistance.

Effect of acute physiological hyperinsulinemia on gene expression in human skeletal muscle in vivo.

This study was undertaken to test the hypothesis that short-term exposure (4 h) to physiological hyperinsulinemia in normal, healthy subjects without a family history of diabetes would induce a low grade inflammatory response independently of glycemic status. Twelve normal glucose tolerant subjects received a 4-h euglycemic hyperinsulinemic clamp with biopsies of the vastus lateralis muscle. Microarray analysis identified 121 probe sets that were significantly altered in response to physiological hyperinsulinemia while maintaining euglycemia. In normal, healthy human subjects insulin increased the mRNAs of a number of inflammatory genes (CCL2, CXCL2 and THBD) and transcription factors (ATF3, BHLHB2, HES1, KLF10, JUNB, FOS, and FOSB). A number of other genes were upregulated in response to insulin, including RRAD, MT, and SGK. CITED2, a known coactivator of PPARalpha, was significantly downregulated. SGK and CITED2 are located at chromosome 6q23, where we previously detected strong linkage to fasting plasma insulin concentrations. We independently validated the mRNA expression changes in an additional five subjects and closely paralleled the results observed in the original 12 subjects. A saline infusion in healthy, normal glucose-tolerant subjects without family history of diabetes demonstrated that the genes altered during the euglycemic hyperinsulinemic clamp were due to hyperinsulinemia and were unrelated to the biopsy procedure per se. The results of the present study demonstrate that insulin acutely regulates the levels of mRNAs involved in inflammation and transcription and identifies several candidate genes, including HES1 and BHLHB2, for further investigation.

Evidence for a potent antiinflammatory effect of rosiglitazone.

We have recently demonstrated a potent antiinflammatory effect of troglitazone, an agonist of peroxisome proliferator-activated receptor gamma (PPARgamma) and a partial agonist of PPARalpha in both the nondiabetic obese and diabetic obese subjects. We have now investigated the antiinflammatory actions of rosiglitazone, a selective PPARgamma agonist. Eleven nondiabetic obese subjects and 11 obese diabetic subjects were each given 4 mg of rosiglitazone daily for a period of 6 wk. Fasting blood samples were obtained at 0, 1, 2, 4, 6, and 12 wk (6 wk after the cessation of rosiglitazone). Eight obese subjects and five obese diabetic subjects were also included in the study as control groups. Fasting blood samples were obtained from the control groups at 0, 1, 2, 4, and 6 wk only. Nuclear factor kappaB (NFkappaB)-binding activity in mononuclear cells, plasma monocyte chemoattractant protein-1 (MCP-1), TNF-alpha, soluble intercellular adhesion molecule-1, C-reactive protein (CRP), and serum amyloid A (SAA) were measured. Blood glucose concentration changed significantly at 6 wk only in the obese diabetic subjects after rosiglitazone treatment for 6 wk, whereas insulin concentration decreased significantly at 6 wk in both groups. NFkappaB-binding activity in mononuclear cell nuclear extract fell in both obese and obese diabetic subjects (P < 0.02). Rosiglitazone treatment resulted in a reduction in plasma MCP-1 and CRP in both groups (P < 0.05). Plasma TNF-alpha and SAA concentrations were inhibited significantly in the obese group (P < 0.05) but not in the obese diabetic subjects. NFkappaB-binding activity and plasma MCP-1, CRP, SAA, and TNF-alpha did not change in the obese and obese diabetic control groups. We conclude that rosiglitazone, a selective PPARgamma agonist, exerts an antiinflammatory effect at the cellular and molecular level, and in plasma. These observations may have implications for atherogenesis in the long term in subjects treated with rosiglitazone and possibly other thiazolidinediones.

Elevation of free fatty acids induces inflammation and impairs vascular reactivity in healthy subjects.

To test the possible acute proinflammatory effects of fatty acids, we induced an increase in plasma free fatty acid (FFA) concentrations after a lipid and heparin infusion for 4 h in 10 healthy subjects. We determined the nuclear factor-kappaB (NF-kappaB) binding activity in mononuclear cells (MNCs), the p65 subunit of NF-kappaB, reactive oxygen species (ROS) generation by MNC, and polymorphonuclear leukocytes (PMN). Brachial artery reactivity, using postischemic flow-mediated dilation, was also measured. NF-kappaB binding activity in the MNC nuclear extracts increased to 163 +/- 17% and 144 +/- 14% as compared with basal levels at 2 and 4 h (P < 0.005) and remained elevated (P < 0.05) at 6 h (2 h after cessation of lipid infusion). NF-kappaB p65 subunit protein expression in MNC homogenates also increased at 2, 4, and 6 h (P < 0.05). ROS generation by PMNs increased significantly at 2 and 4 h (P < 0.005), whereas that by MNCs increased at 4 h (P < 0.05). Plasma macrophage migration inhibitory factor increased at 2 (P < 0.05) and 4 h (P < 0.005), respectively, and declined to baseline at 6 h. The postischemic flow-mediated dilation of brachial artery decreased from 6.3 +/- 1.1% at baseline to 4.3 +/- 1.9% and 2.7 +/- 2.1% (P < 0.01) at 2, 4, and 6 h, respectively. We conclude that an increase in FFA concentration induces oxidative stress and has a proinflammatory effect; it also impairs postischemic flow-mediated vasodilation of the brachial artery.

Insulin resistance as a proinflammatory state: mechanisms, mediators, and therapeutic interventions.

Insulin resistance has been recognized as an inflammatory disease based on the scientific evidence collected over the last decade. Inflammatory markers like CRP, PAI-1, IL-6 are present in higher concentrations in insulin resistant people than in normal people. Mechanisms, linking inflammation to insulin resistance are being explored and progress has been made in this direction. TNFalpha has been shown to be responsible for insulin resistance in obese subjects. Macronutrient intake may also induce inflammation whereas fasting has anti-inflammatory effects. Insulin itself has been found to be anti-inflammatory and this action may be useful in many disease states. Thiazolidinediones, such as rosiglitazone that act primarily as insulin sensitisers, have a profound anti-inflammatory and potentially antiatherosclerotic activity. These effects may be of considerable clinical significance if sustained during long-term therapy, given the morbidity and mortality associated with atherosclerosis, the major complication of insulin resistance.

Hypogonadotropic hypogonadism in erectile dysfunction associated with type 2 diabetes mellitus: a common defect?

UNLABELLED: The objective of this study was to evaluate the gonadal function in men with type 2 diabetes with erectile dysfunction. METHODS: We examine records of 50 patients with type 2 diabetes and erectile dysfunction who had low free testosterone concentrations. All patients had plasma concentrations of luteinizing hormones (LH), follicle-stimulating hormone (FSH), and prolactin measured. RESULTS: Of the 50 patients with low free testosterone concentrations (0.97 +/- 0.4 ng/dL; reference range, 1.30-3.10), 43 had normal (inappropriately low) LH (5.9 +/- 2.9 mIU/mL), FSH (5.6 +/- 2.4 mIU/mL), and testosterone concentrations, five had elevated LH, FSH concentrations (Hypogonadotropic hypogonadism), and two had prolactinoma. Patients with hypogonadotropic hypogonadism were in their mid 50's and had experienced a decline in their testosterone levels much earlier than that expected from the normal age-related decline. Although a majority of the patients were obese, there was no relationship between testosterone (free or total) and BMI, between testosterone and HbA(1c), duration of diabetes or the age of the patient. Patients given testosterone supplementation experienced a subjective improvement in their wellbeing, but reported no significant improvement in their erectile dysfunction. CONCLUSION: We conclude that patients with erectile dysfunction require careful assessment and that the most frequent gonadal defect in these patients is that of hypogonadotropic hypogonadism, a defect not previously associated with type 2 diabetes. The mechanism underlying this defect requires investigation. The value of testosterone replacement in such patients needs to be assessed critically.