Obese Type 2 Diabetes Subjects Research Articles

1426-P: Increased Insulin Secretion and Glucose Effectiveness Result in Improved Glucose Tolerance in Obese Subjects Two Months after Gastric Bypass and Sleeve

The early effects of bariatric surgery on insulin secretion and action in obese subjects with type 2 diabetes (T2D) remains poorly investigated. Here we assessed the mechanisms resulting in improved glucose intolerance using the oral minimal model approach. An oral glucose tolerance test was performed before and 2 months after bariatric surgery in 16 obese T2D subjects (9 bypass, 7 gastric sleeve) and in 8 healthy control subjects. For each visit, body mass index (BMI) was measured, and the oral glucose and the insulin and C-peptide minimal models were used to estimate insulin sensitivity (SI) , glucose effectiveness (GE) , total β-cell responsiveness (Φtot) , disposition index (DI) and total hepatic insulin extraction (HE) . Bariatric surgery resulted in a significant reduction (similar between bypass and sleeve groups) in BMI by 14% (from 42±5 to 36±4 kg/m2) . Glucose tolerance increased comparably after bypass and sleeve, but remained impaired compared to the control group (Figure 1) : GE, Φtot, DI and HE were equally increased following bariatric surgery, whereas insulin action (SI) remained unaltered in the two groups. These results suggest that improved glucose tolerance in obese T2D subjects 2 months after bariatric surgery is attributable mainly to an increase in insulin secretion and glucose effectiveness rather than an improvement in insulin action. Disclosure R. Visentin: Research Support; Becton, Dickinson and Company, MannKind Corporation, Sanofi-Aventis Deutschland GmbH. K. Brodersen: None. N. Moller: None. C. Dalla Man: Research Support; Becton, Dickinson and Company, Sanofi-Aventis Deutschland GmbH. M.F. Nielsen: None. Funding Novo Nordisk Foundation

Rationale for an anti‐inflammatory insulin sensitizer in a phase 3 Alzheimer's disease trial

AbstractBackgroundNE3107 (3α‐ethynyl‐androst‐5‐ene‐3β,7β,17β‐triol), shows safety, antiinflammatory and insulin‐sensitizing activities in vitro, in animals, and humans. NE3107 binds ERK1/2 and inhibits inflammatory, but not homeostatic NFkB/ERK signaling in vitro, in animals and in humans. NE3107 is blood‐brain permeable, and does not affect neurotransmitter receptors. NE3107 inhibits TNFα‐stimulated NFκB transcription in human macrophages. It also inhibits NFκB nuclear translocation and LPS‐stimulated inflammatory signal transduction. NE3107 prevented IκBα proteolysis in murine macrophages. NE3107 decreased EAE optic nerve microglia, and increased nuclear NFκB in collicular and retinal neurons (homeostatic), but decreased optic nerve head glial nuclear NFκB (inflammatory) in a glaucoma model. NE3107 preserved dopaminergic neurons in MPTP‐treated mice and marmosets. In obese impaired glucose tolerance (IGT) humans, NE3107 decreased CRP, which is involved in AD inflammation and tissue damage, and increased antiinflammatory HDL, which decreases risk of AD pathogenesis. NE3107 increased adiponectin, which suppresses insulin resistance, inflammation, and AD pathology. In obese, inflamed IGT and type 2 diabetes (T2D) subjects, NE3107 decreased insulin resistance, which drives neurodegeneration and AD. Importantly, in obese inflamed T2D subjects, NE3107 decreased inflammation‐driven systems deregulation, known to contribute to AD progression.MethodSafety and activity data from preclinical, toxicology, human clinical trials, and a protocol synopsis for a pivotal trial in AD were submitted, and the FDA allowed NeurMedix to proceed with the NM101 trial.ResultA Phase 3, Double Blind, Randomized, Placebo Controlled, Parallel Group, Multicenter Study of NE3107 in Subjects Who Have Mild to Moderate Alzheimer's Disease (NCT04669028) will evaluate safety and efficacy of oral 20 mg BID NE3107 vs. placebo in 316 subjects with mild to moderate AD. Two coprimary outcome measures ADAS Cog12 and ADCS CGIC will be evaluated as the change from Baseline to Week 30. Secondary endpoints include measures of neuropsychological deficits, functional performance, glycemic control and resource utilization. A subset of patients may volunteer for exploratory vMRI and FDG‐PET scans at baseline and week 30.ConclusionInflammation and insulin resistance drive AD. NE3107 decreases these insults that drive systems dysregulation in AD. This trial is well‐positioned to examine the effects of NE3107 on progression of AD dementia, affecting more than 40 million people globally.

Identification of macrophage activation-related biomarkers in obese type 2 diabetes that may be indicative of enhanced respiratory risk in COVID-19

Hyperactivation of the immune system through obesity and diabetes may enhance infection severity complicated by Acute Respiratory Distress Syndrome (ARDS). The objective was to determine the circulatory biomarkers for macrophage activation at baseline and after serum glucose normalization in obese type 2 diabetes (OT2D) subjects. A case-controlled interventional pilot study in OT2D (n = 23) and control subjects (n = 23). OT2D subjects underwent hyperinsulinemic clamp to normalize serum glucose. Plasma macrophage-related proteins were determined using Slow Off-rate Modified Aptamer-scan plasma protein measurement at baseline (control and OT2D subjects) and after 1-h of insulin clamp (OT2D subjects only). Basal M1 macrophage activation was characterized by elevated levels of M1 macrophage-specific surface proteins, CD80 and CD38, and cytokines or chemokines (CXCL1, CXCL5, RANTES) released by activated M1 macrophages. Two potent M1 macrophage activation markers, CXCL9 and CXCL10, were decreased in OT2D. Activated M2 macrophages were characterized by elevated levels of plasma CD163, TFGβ-1, MMP7 and MMP9 in OT2D. Conventional mediators of both M1 and M2 macrophage activation markers (IFN-γ, IL-4, IL-13) were not altered. No changes were observed in plasma levels of M1/M2 macrophage activation markers in OT2D in response to acute normalization of glycemia. In the basal state, macrophage activation markers are elevated, and these reflect the expression of circulatory cytokines, chemokines, growth factors and matrix metalloproteinases in obese individuals with type 2 diabetes, that were not changed by glucose normalisation. These differences could potentially predispose diabetic individuals to increased infection severity complicated by ARDS.Clinical trial reg. no: NCT03102801; registration date April 6, 2017.

Glucagon and Liver Fat are Downregulated in Response to Very Low-calorie Diet in Patients with Obesity and Type-2 Diabetes.

In patients with obesity and type-2 diabetes, short-time very low-calorie diet may ameliorate hyperglycemia and hepatic steatosis. Whether this also implies the glucose-regulating hormone glucagon remains to be elucidated. This study investigated the effects of a very low-calorie diet on plasma levels of glucagon and liver fat in obese patients with type-2 diabetes. Ten obese patients with type-2 diabetes, 6 men and 4 women, were included. At baseline, fasting plasma glucagon, insulin and glucose were determined, and liver fat and stiffness evaluated by transient elastography. The subjects were then prescribed a very low-calorie diet of maximum 800 kcal/day for 7 weeks and reexamined after 7 weeks and 12 months. At baseline, BMI was 42±4 kg/m2 and fasting glucose 10.6±3.4 mmol/l. All patients had hepatic steatosis. Plasma glucagon was strongly related to liver fat (r2=0.52, p=0.018). After 7 weeks of very low-calorie diet, plasma glucagon was significantly decreased by nearly 30% (p=0.004) along with reductions of BMI (p<0.0001), glucose (p=0.02), insulin (p=0.03), liver fat (p=0.007) and liver stiffness (p=0.05). At 12 months follow-up, both glucagon and liver fat increased and were not different to basal levels, despite persistent reductions of BMI (p<0.002) and glucose (p=0.008). In obese type-2 diabetic subjects, plasma glucagon and liver fat are correlated and similarly affected by a very low-calorie diet, supporting a role of hepatic steatosis in glucagon metabolism.

Different β-cell secretory phenotype in non-obese compared to obese early type 2 diabetes.

Type 2 diabetes (T2D) is characterized by impaired tissue sensitivity to insulin action (ie, insulin resistance) and impaired β-cell insulin secretion. Because obesity contributes importantly to the development of insulin resistance, we sought to determine whether insulin secretory defects would predominate in non-obese compared to obese T2D. We measured β-cell function and secretory capacity using the glucose-potentiated arginine test in T2D subjects early in the disease course classified as non-obese (BMI <30; n = 12) or obese (BMI ≥30 kg/m2 ; n = 28) and additionally compared responses from non-obese T2D with a non-diabetic control group (n = 12). The acute insulin response to glucose potentiation of arginine-induced insulin release was less in non-obese T2D than in controls and associated with impaired β-cell sensitivity to glucose (PG50 ). Proinsulin secretory ratios were increased in non-obese T2D when compared to obese T2D. Obese T2D subjects had reduced insulin sensitivity (M/I) while non-obese T2D subjects had insulin sensitivity that was comparable to controls. In non-obese T2D, insulin secretory defects predominate with impaired β-cell sensitivity to glucose and proinsulin processing in the absence of insulin resistance. Future studies should consider whether different β-cell secretory phenotypes and tissue sensitivity to insulin explain the varying responsiveness to T2D interventions.

Aerobic exercise training improves hepatic and muscle insulin sensitivity, but reduces splanchnic glucose uptake in obese humans with type 2 diabetes

BackgroundAerobic exercise training is known to have beneficial effects on whole-body glucose metabolism in people with type 2 diabetes (T2D). The responses of the liver to such training are less well understood. The purpose of this study was to determine the effect of aerobic exercise training on splanchnic glucose uptake (SGU) and insulin-mediated suppression of endogenous glucose production (EGP) in obese subjects with T2D.MethodsParticipants included 11 obese humans with T2D, who underwent 15 ± 2 weeks of aerobic exercise training (AEX; n = 6) or remained sedentary for 15 ± 1 weeks (SED; n = 5). After an initial screening visit, each subject underwent an oral glucose load clamp and an isoglycemic/two-step (20 and 40 mU/m2/min) hyperinsulinemic clamp (ISO-clamp) to assess SGU and insulin-mediated suppression of EGP, respectively. After the intervention period, both tests were repeated.ResultsIn AEX, the ability of insulin to suppress EGP was improved during both the low (69 ± 9 and 80 ± 6% suppression; pre-post, respectively; p < 0.05) and high (67 ± 6 and 82 ± 4% suppression, respectively; p < 0.05) insulin infusion periods. Despite markedly improved muscle insulin sensitivity, SGU was reduced in AEX after training (22.9 ± 3.3 and 9.1 ± 6.0 g pre-post in AEX, respectively; p < 0.05).ConclusionsIn obese T2D subjects, exercise training improves whole-body glucose metabolism, in part, by improving insulin-mediated suppression of EGP and enhancing muscle glucose uptake, which occur despite reduced SGU during an oral glucose challenge.

Comparison of Sleeve Gastrectomy and Conservatory Treatment Effect on Biochemical and Hormonal Profile of Obese Type 2 Diabetes Subjects: CREDOR Randomized Controlled Study Results

Metabolic surgery is the most efficacious method for the treatment of morbid obesity and was recently included among the antidiabetes treatments recommended in obese type 2 diabetes (T2D) patients. The aim of this study was to compare in a randomized controlled trial the effect of sleeve gastrectomy (SG) to that of intensive lifestyle intervention plus pharmacologic treatment on some markers of insulin resistance and beta cell function as well as some appetite controlling hormones in a group of male obese T2D subjects. The study groups comprised 20 subjects for SG and 21 control subjects. Fasting blood glucose, insulin, proinsulin, adiponectin, leptin, ghrelin, HOMA-IR, HOMA-%B, proinsulin-to-insulin ratio and proinsulin-to-adiponectin ratio were evaluated at baseline and after one year follow-up. Overall, patients in the SG group lost 78.98% of excess weight loss (%EWL) in comparison with 9.45% in the control group. This was accompanied by a significant improvement of insulin resistance markers, including increase of adiponectin and decrease of HOMA-IR, while no changes were recorded in the control group. Weight loss was also associated with a significant improvement of proinsulin-to-insulin and proinsulin-to-adiponectin ratio, both surrogate markers of beta cell dysfunction. These also improved in the control group, but were only marginally significant. Our findings suggest that improved insulin resistance and decreased beta cell dysfunction after sleeve gastrectomy might explain diabetes remission associated with metabolic surgery.

Sympathetic nervous system activity and anti-lipolytic response to iv-glucose load in subcutaneous adipose tissue of obese and obese type 2 diabetic subjects.

The study aim was to investigate the effect of endogenous insulin release on lipolysis in subcutaneous adipose tissue after adrenergic stimulation in obese subjects diagnosed with type 2 diabetes (T2D). In 14 obese female T2D subjects, or 14 obese non-T2D controls, glycerol concentration was measured in response to the α1,2,ß-agonist norepinephrine, the α1-agonist norfenefrine and the ß2-agonist terbutaline (each 10−4 M), using the microdialysis technique. After 60 minutes of stimulation, an intravenous glucose load (0.5 g/kg lean body mass) was given. Local blood flow was monitored by means of the ethanol technique. Norepinephrine and norfenefrine induced a four and three fold rise in glycerol dialysate concentration (p<0.001, each), with a similar pattern in adipose tissue. Following agonist stimulation and glucose infusion, endogenous insulin release inhibited lipolysis in the presence of norepinephrine, which was more rapid and pronounced in healthy obese controls than in T2D subjects (p = 0.024 obese vs T2D subjects). Insulin-induced inhibition of lipolysis in the presence of norfenefrine was similar in all study participants. In the presence of terbutaline the lipolysis rate increased two fold until the effect of endogenous insulin (p<0.001). A similar insulin-induced decrease in lipolysis was observed for each of the norfenefrine groups and the terbutaline groups, respectively. Adipose tissue blood flow remained unchanged after the iv-glucose load. Both norepinephrine and norfenefrine diminished blood flow slightly, but insulin reversed this response (p<0.001 over the entire time). Terbutaline alone and terbutaline plus increased endogenous insulin augmented local blood flow (p<0.001 over the entire time). In conclusion, a difference in insulin-induced inhibition of lipolysis was observed in obese T2D subjects compared to obese healthy controls following modulation of sympathetic nervous system activity and is assumed to be due to ß1-adrenoceptor mediated stimulation by norepinephrine.

Increased ANGPTL3, 4 and ANGPTL8/betatrophin expression levels in obesity and T2D

BackgroundHypertriglyceridemia is associated with increased risk for cardiovascular diseases and type 2 diabetes (T2D). Angiopoietin like proteins particularly 3, 4 and recently 8 are well established regulators of plasma triglyceride level through regulating the activity of lipoprotein lipase. Plasma level and association between ANGPTL3, 4 and 8 is not well established in human subjects. This study was designed to establish the level of these proteins in plasma and adipose tissues and investigate the association between ANGPTL8 with ANGPTL3 and 4 in T2D and non-diabetics subjects.MethodsA total of 235 subjects were enrolled in this study, 144 non-diabetics and 91 T2D. ANGPTL 3, 4 and 8 levels were measured in plasma by ELISA and using real time RT-PCR in adipose tissues.ResultsIn this study, we showed that ANGPTL3, 4 and 8 were higher in T2D subjects. Dividing the non-diabetic subjects according to their BMI showed higher level of ANGPTL3, 4 and 8 in obese subjects compared to non-obese subjects. No significant difference was observed between the T2D subjects. ANGPTL8 was showed positive correlation with ANGPTL3 in the non-diabetic subjects in the non-obese (r = 0.2437, p-Value = 0.0543) and obese subjects (r = 0.418, p-Value = 0.0125). No association was observed in the T2D subjects. On the other hand, ANGPTL4 was positively associated with the obese subjects in both the non-diabetics (r = 0.3322, p-Value = 0.0316) and the obese T2D subjects (r = 0.3161, p-Value = 0.0211).ConclusionIn conclusion, our data shows that ANGPTL3, 4 and 8 are increased in obesity and T2D. ANGPTL8 associates with ANGPTL3 in the non-diabetic subjects while it associated more with ANGPTL4 in the obese and T2D subjects. Taken together, this data highlight the role of these proteins in metabolic diseases and how they interact with each other’s under different physiological and pathophysiological conditions.

Effects of glucagon-like peptide-1 on the differentiation and metabolism of human adipocytes.

Glucagon-like peptide-1 (GLP-1) analogues improve glycaemic control in type 2 diabetic (T2D) patients and cause weight loss in obese subjects by as yet unknown mechanisms. We recently demonstrated that the GLP-1 receptor, which is present in adipocytes and the stromal vascular fraction of human adipose tissue (AT), is up-regulated in AT of insulin-resistant morbidly obese subjects compared with healthy lean subjects. The aim of this study was to explore the effects of in vitro and in vivo administration of GLP-1 and its analogues on AT and adipocyte functions from T2D morbidly obese subjects. We analysed the effects of GLP-1 on human AT and isolated adipocytes in vitro and the effects of GLP-1 mimetics on AT of morbidly obese T2D subjects in vivo. GLP-1 down-regulated the expression of lipogenic genes when administered during in vitro differentiation of human adipocytes from morbidly obese patients. GLP-1 also decreased the expression of adipogenic/lipogenic genes in AT explants and mature adipocytes, while increasing that of lipolytic markers and adiponectin. In 3T3-L1 adipocytes, GLP-1 decreased free cytosolic Ca2+ concentration ([Ca2+]i). GLP-1-induced responses were only partially blocked by GLP-1 receptor antagonist exendin (9–39). Moreover, administration of exenatide or liraglutide reduced adipogenic and inflammatory marker mRNA in AT of T2D obese subjects. Our data suggest that the beneficial effects of GLP-1 are associated with changes in the adipogenic potential and ability of AT to expand, via activation of the canonical GLP-1 receptor and an additional, as yet unknown, receptor.

Monocytes play different roles in stimulating T cells in obese diabetic individuals.

Type 2 diabetes (T2D) is a chronic metabolic disorder, which was also found to involve a series of inflammatory disorders, including accumulation of macrophages and T cells in the adipose tissue, increased proinflammatory cytokine production, shifting of macrophage composition toward M1-type, and skewing of peripheral blood T cells toward IL-17 productions. However, these studies were primarily conducted in obese mouse models and/or human subjects with higher BMI, and may not reflect the role of the immune system in non-obese T2D pathogenesis. Here, we examined T cell and monocyte cytokine expression and function in both non-obese and obese T2D patients. We found that IFN-g production by circulating T cells were increased in both non-obese and obese T2D subjects, while IL-17 is only upregulated in obese T2D subjects. Also, circulating monocytes from obese T2D subjects had significantly higher IL-6 production than their counterparts in non-obese T2D subjects. Moreover, monocytes from non-obese T2D subjects could support IFN-g but not IL-17 production in vitro, while that from obese T2D subjects supported both IFN-g and IL-17 production. Together, our results revealed that the role immune system plays in T2D pathogenesis is more complicated than previously thought, and is affected by the person's BMI.

Tissue factor expression in obese type 2 diabetic subjects and its regulation by antidiabetic agents.

Objective. Increased coagulation activation may contribute to the high incidence of cardiovascular complications observed in obese and type 2 diabetes (T2D) subjects. Although tissue factor (TF), the primary initiator of coagulation is increased in obesity, its expression in adipose tissues and its association with metabolic parameters are unclear. We sought to compare TF expression in plasma and adipose tissues of obese subjects with and without T2D, its correlation with metabolic parameters, and regulation in response to antidiabetic drugs. Methods Subjects were recruited from diabetes clinics and adipose tissue was obtained by needle biopsy of lower subcutaneous abdominal depot. For the intervention study, subjects were randomized into treatment groups with rosiglitazone or metformin for 4 months. Results. Plasma TF antigen, activity, and adipose TF mRNA were greater in obese T2D subjects compared with obese nondiabetics. Plasma TF activity correlated with fasting insulin, glucose, and free fatty acids, (FFAs), and adipose TF mRNA correlated with plasma FFA. Plasma TF activity was reduced by metformin and increased with rosiglitazone treatment. Conclusions. Specific diabetes-related metabolic parameters, but not obesity per se, are correlated with TF expression. Regulation of TF activity by different classes of antidiabetic drugs may relate to protective or adverse cardiovascular outcomes.

No difference in insulin stimulated AKT and AS160 phosphorylation but decreased insulin effect on FoxO4 abundance in skeletal muscle of obese and obese type 2-diabetic subjects

No difference in insulin stimulated AKT and AS160 phosphorylation but decreased insulin effect on FoxO4 abundance in skeletal muscle of obese and obese type 2-diabetic subjects

FA1 Induces Pro-Inflammatory and Anti-Adipogenic Pathways/Markers in Human Myotubes Established from Lean, Obese, and Type 2 Diabetic Subjects but Not Insulin Resistance

Aims: Delta like 1/fetal antigen 1 (Dlk1/FA1) is a protein secreted by hormone producing cells in adult human and mice that is known to inhibit adipogenesis. Recent studies demonstrated the role of Dlk1/FA1 in inducing insulin resistance in mice. To investigate the involvement of circulating Dlk1/FA1 in insulin resistance and type 2 diabetes in human subjects, we studied the effects of chronic FA1 on the intermediary metabolism in myotubes established from lean, obese, and type 2 diabetic (T2D) subjects.Methods: Myotube cultures were established from lean and obese control subjects, and obese T2D subjects and treated with soluble FA1 for 4 days supplemented with/without palmitate (PA). Lipid- and glucose metabolism were studied with labeled precursors while quantitative expression of genes was analyzed using real-time PCR.Results: Diabetic myotubes express significantly reduced insulin stimulated glucose metabolism compared to lean myotubes and a significantly decreased basal PA oxidation. Chronic FA1 exposure did not affect the intermediary metabolism in myotubes. Insulin sensitivity of glucose and lipid metabolism was not affected by chronic FA1 exposure in myotubes established from lean, obese, and T2D subjects. Instead, chronic FA1 exposure induced pro-inflammatory cytokines expression (IL-6 and CCL2) in association with reducing adipogenic markers (ADD1, AP2, CD36, and PPARg2) in myotubes. Consistent with this observation, addition of FA1 to cultured myotubes was show to significantly inhibit their differentiation into adipocyte.Conclusion: Our results exclude direct effects of FA1 on glucose and lipid metabolism in cultured myotubes established from lean, obese, and T2D subjects. Therefore, the pathogenesis of FA1-induced IR might mainly be mediated via the FA1-induced stimulation of pro-inflammatory cytokines, which on turn inhibit adipogenesis in human myotubes.

Low Macrophage Accumulation in Skeletal Muscle of Obese Type 2 Diabetics and Elderly Subjects

In addition to adipose tissue, recent studies suggest that skeletal muscle may also be a source of low grade inflammation, particularly in inactive and/or overweight individuals. The aim of this study was to examine the presence of macrophages in skeletal muscle from obese subjects with type 2 diabetes (T2D) before and after a 9-month exercise program (vs. a non-exercising control group) (Study 1) and in young vs. elderly subjects (Study 2). In both studies, CD68+ macrophages in vastus lateralis biopsies were determined by immunohistochemistry and inflammation gene expression measured. Macrophage content (%) was calculated by the number of macrophages per 100 muscle fibers. In Study 1, we found relatively low numbers (2–3%) of CD68+ macrophages in skeletal muscle in obese T2D subjects (BMI= 37.3 ± 5.2kg/m2), which were unchanged after a 9-month exercise program (P=0.42). Similarly, in Study 2 (BMI=27.1 ± 2.5kg/m2), CD68+ macrophages were relatively low in muscle (4–5%) and were not different between young and elderly individuals (P=0.42). However, elderly subjects had 2-fold higher CD68 and CD206 gene expression (both P<0.002) than young participants. In both studies, CD68+ muscle macrophages were not associated with BMI. In conclusion, we found little evidence of macrophage accumulation in skeletal muscle in obese T2D subjects or in elderly individuals. A 9-month exercise program was not associated with a decrease in macrophage content.

Elevated NF-κB Activation Is Conserved in Human Myocytes Cultured From Obese Type 2 Diabetic Patients and Attenuated by AMP-Activated Protein Kinase

OBJECTIVETo examine whether the inflammatory phenotype found in obese and diabetic individuals is preserved in isolated, cultured myocytes and to assess the effectiveness of pharmacological AMP-activated protein kinase (AMPK) activation upon the attenuation of inflammation in these myocytes.RESEARCH DESIGN AND METHODSMuscle precursor cells were isolated from four age-matched subject groups: 1) nonobese, normal glucose tolerant; 2) obese, normal glucose tolerant; 3) obese, impaired glucose tolerant; and 4) obese, type 2 diabetes (T2D). The level of inflammation (nuclear factor-κB [NF-κB] signaling) and effect of pharmacological AMPK activation was assessed by Western blots, enzyme-linked immunosorbent assay, and radioactive assays (n = 5 for each subject group).RESULTSNF-κB-p65 DNA binding activity was significantly elevated in myocytes from obese T2D patients compared with nonobese control subjects. This correlated to a significant increase in tumor necrosis factor-α concentration in cell culture media. In addition, insulin-stimulated glucose uptake was completely suppressed in myocytes from obese impaired glucose tolerant and T2D subjects. It is interesting that activation of AMPK by A769662 attenuated NF-κB-p65 DNA binding activity in obese T2D cells to levels measured in nonobese myocytes; however, this had no effect on insulin sensitivity of the cells.CONCLUSIONSThis work provides solid evidence that differentiated human muscle precursor cells maintain in vivo phenotypes of inflammation and insulin resistance and that obesity alone may not be sufficient to establish inflammation in these cells. It is important that we demonstrate an anti-inflammatory role for AMPK in these human cells. Despite attenuation of NF-κB activity by AMPK, insulin resistance in obese T2D cells remained, suggesting factors in addition to inflammation may contribute to the insulin resistance phenotype in muscle cells.

Paired Subcutaneous and Visceral Adipose Tissue Aquaporin-7 Expression in Human Obesity and Type 2 Diabetes: Differences and Similarities between Depots

AQP7 is considered to be the sole adipose glycerol channel, and its regulation is crucial for glycemia control. In this work, we aimed to further characterize AQP7 in human adipose tissue in obesity and type 2 diabetes (T2D): 1) to assess AQP7 expression levels in paired abdominal adipose tissue depots (sc and visceral); 2) to relate it with gene expression of genes involved in lipid metabolism; and 3) to confirm that AQP7 is mainly expressed in the adipocytes. We conducted a transversal study of gene expression in paired samples of sc adipose tissue (SAT) and visceral adipose tissue (VAT). Caucasian lean and obese subjects (n = 62, matched for age and gender) and T2D subjects (n = 11, matched for age, gender, and BMI with their control group) participated in the study. We measured AQP7 expression levels in paired SAT and VAT. We have proved the presence of AQP7 mRNA and protein in the adipocyte rather than the stromovascular fraction of adipose tissue (P = 0.001) and in mature adipocytes when differentiated in vitro. Increased AQP7 mRNA expression levels in VAT from T2D obese subjects (P < 0.05) were found. AQP7 transcript levels ratio of SAT vs. VAT changed with the presence of obesity and T2D. Interestingly, there were positive associations between AQP7 and both lipogenic and lipolytic genes in a similar manner in both adipose depots. Taken together, these data suggest a subtle regulation between adipose depots of the sole adipose aquaporin, AQP7, which is unbalanced in obesity and T2D.

Maximal lipid oxidation in patients with type 2 diabetes is normal and shows an adequate increase in response to aerobic training

Insulin resistance in subjects with type 2 diabetes (T2D) and obesity is associated with an imbalance between the availability and the oxidation of lipids. We hypothesized that maximal whole-body lipid oxidation during exercise (FATmax) is reduced and that training-induced metabolic adaptation is attenuated in T2D. Obese T2D (n = 12) and control (n = 11) subjects matched for age, sex, physical activity and body mass index completed 10 weeks of aerobic training. Subjects were investigated before and after training with maximal and submaximal exercise tests and euglycaemic-hyperinsulinaemic clamps combined with muscle biopsies. Training increased maximal oxygen consumption (VO(2max)) and muscle citrate synthase activity and decreased blood lactate concentrations during submaximal exercise in both groups (all p < 0.01). FATmax increased markedly (40-50%) in both T2D and control subjects after training (all p < 0.001). There were no significant differences in these variables and lactate threshold (%VO(2max)) between groups before or after training. Insulin-stimulated glucose disappearance rate (Rd) was lower in T2D vs. control subjects both before and after training. Rd increased in response to training in both groups (all p < 0.01). There was no correlation between Rd and measures of oxidative capacity or lipid oxidation during exercise or the training-induced changes in these parameters. FATmax was not reduced in T2D, and muscle oxidative capacity increased adequately in response to aerobic training in obese subjects with and without T2D. These metabolic adaptations to training seem to be unrelated to changes in insulin sensitivity and indicate that an impaired capacity for lipid oxidation is not a major cause of insulin resistance in T2D.

Reduced lipid oxidation in myotubes established from obese and type 2 diabetic subjects

To date, it is unknown whether reduced lipid oxidation of skeletal muscle of obese and obese type 2 diabetic (T2D) subjects partly is based on reduced oxidation of endogenous lipids. Palmitate (PA) accumulation, total oxidation and lipolysis were not different between myotubes established from lean, obese and T2D subjects, chronic exposed for PA. Complete oxidation from endogenous PA was reduced in diabetic and obese compared to lean myotubes while exogenous PA oxidation was reduced in diabetic compared to lean myotubes. The complete/incomplete ratio was significantly reduced in diabetic myotubes both for endogenous and exogenous lipids. Thus myotubes established from obese and obese T2D subjects express a reduced complete oxidation of endogenous lipids. Two cardinal principles govern the reduced lipid oxidation in obese and diabetic myotubes; firstly, an impaired coupling between endogenous lipid and mitochondria in obese and obese diabetic myotubes and secondly, a mismatch between β-oxidation and citric acid cycle in obese diabetic myotubes.

Tissue-specific expression and regulation of GSK-3 in human skeletal muscle and adipose tissue

Glycogen synthase kinase-3 (GSK-3) is a ubiquitous kinase implicated in both insulin action and adipogenesis. To determine how these multiple roles may relate to insulin resistance, we studied the regulation of GSK-3 protein expression and phosphorylation in skeletal muscle and isolated adipocytes from nonobese healthy control (HC), obese control (OC), and obese type 2 diabetic (OT2D) subjects. At baseline there were no differences in the GSK-3 protein expression in adipocytes. OC subjects underwent a 6-mo caloric restriction resulting in a 7% decrease in body mass index (BMI) and a 21% improvement in insulin-stimulated whole body glucose disposal rate (GDR). GSK-3alpha and GSK-3beta expression decreased in adipocytes (P < 0.05), whereas GSK-3alpha protein expression increased in skeletal muscle (P < 0.05). OT2D subjects were treated with troglitazone or metformin for 3-4 mo. After troglitazone treatment GDR improved (P < 0.05) despite an increase in BMI (P < 0.05), whereas metformin had no significant effect on GDR. There was no significant change in GSK-3 expression in adipocytes following troglitazone, whereas both GSK-3alpha and -beta were decreased in skeletal muscle (P < 0.05). Metformin treatment had no significant impact on GSK-3 protein expression in either adipocytes or skeletal muscle. Neither treatment influenced GSK-3 serine phosphorylation in skeletal muscle or adipocytes. These results suggest that there is tissue specificity for the regulation of GSK-3 in humans. In skeletal muscle GSK-3 plays a role in control of metabolism and insulin action, whereas the function in adipose tissue is less clear.