Promotes Insulin Sensitivity Research Articles

Oxidative Stress Modulation by Cameroonian Spice Extracts in HepG2 Cells: Involvement of Nrf2 and Improvement of Glucose Uptake.

Oxidative stress plays a relevant role in the progression of chronic conditions, including cardiometabolic diseases. Several Cameroonian plants, including spices, are traditionally used as herbal medicines for the treatment of diseases where oxidative stress contributes to insulin resistance, like type 2 diabetes mellitus. This study evaluated the antioxidant capacity and the effects on oxidative-stress-induced impairment of glucose uptake of 11 Cameroonian spice extracts. H2O2-induced reactive oxygen species (ROS) production by human HepG2 cells was significantly reduced by 8/11 extracts. The most effective extracts, Xylopia parviflora, Echinops giganteus, and Dichrostachys glomerata, showed a concentration-dependent ROS-scavenging activity, which involved Nrf2 translocation into the nucleus. Xylopia parviflora, Tetrapleura tetraptera, Dichrostachys glomerata, Aframomum melegueta, and Aframomum citratum extracts showed the highest antioxidant capacity, according to oxygen radical absorbance capacity (ORAC) (2.52–88 μM Trolox Eq/g of extract), ferric-reducing antioxidant power (FRAP) (40.23–233.84 mg gallic acid Eq/g of extract), and total phenol (8.96–32.96% mg gallic acid Eq/g of extract) assays. In HepG2 cells, glucose uptake was stimulated by 4/11 extracts, similarly to insulin and metformin. H2O2-induced oxidative stress reduced glucose uptake, which was rescued by pretreatment with Xylopia aethiopica, Xylopia parviflora, Scorodophloeus zenkeri, Monodora myristica, and Dichrostachys glomerata extracts. The ROS-scavenging ability of the spice extracts may reside in some secondary metabolites observed by phytochemical profiling (reverse-phase high-performance liquid chromatography coupled to a diode array detector (HPLC-UV-DAD)). Further studies are needed to better clarify their biological activities and potential use to control oxidative stress and promote insulin sensitivity.

Upregulation of IL-4 signaling contributes to aerobic exercise-induced insulin sensitivity

Insulin resistance (IR) is an important pathological basis of obesity, diabetes and cardiovascular diseases, and emerging evidence demonstrates aerobic exercise as an efficient therapeutical tool in the management of IR and IR-related metabolic disease. Interleukin-4 (IL-4), an important anti-inflammatory cytokine, was recently proved to be involved in regulation of IR, yet the effect of IL-4 on exercise-induced insulin sensitivity and underlying mechanism was less investigated. In this study, using a mouse model of swimming exercise training (60 min/day, 5 days/week for 8 weeks), we found that long-term swimming exercise promoted insulin sensitivity compared with sedentary groups as indexed by the homeostasis model assessment of insulin resistance (HOMA-IR), glucose and insulin tolerance test. Accompanying with increased insulin sensitivity, swimming exercise increased serum IL-4 levels as well as insulin receptor substrate 1 (IRS-1) and protein kinase B (Akt) phosphorylation. Mechanistically, IL-4 treatment increased insulin-stimulated glucose uptake and Akt phosphorylation in skeletal muscle C2C12 cells, and inhibition of IL-4 signaling via ruxolitinib, a Janus kinase (JAK) inhibitor, attenuated IL-4-induced insulin sensitivity. Taken together, our results demonstrated IL-4 as a novel exercise factor contributing to exercise-induced insulin sensitivity, providing a potential therapeutical target of IR and related metabolic disease.

Combined Soluble Fiber-Mediated Intestinal Microbiota Improve Insulin Sensitivity of Obese Mice.

Dietary fiber, an important regulator of intestinal microbiota, is a promising tool for preventing obesity and related metabolic disorders. However, the functional links between dietary fiber, intestinal microbiota, and obesity phenotype are still not fully understood. Combined soluble fiber (CSF) is a synthetic mixture of polysaccharides and displays high viscosity, water-binding capacity, swelling capacity, and fermentability. We found that supplementing high-fat diet (HFD) with 6% CSF significantly improved the insulin sensitivity of obese mice without affecting their body weight. Replacing the HFD with normal chow basal diet (NCD), the presence of CSF in the feed significantly enhanced satiety, decreased energy intake, promoted weight and fat loss, and augmented insulin sensitivity. CSF also improved the intestinal morphological integrity, attenuated systemic inflammation, promoted intestinal microbiota homeostasis, and stabilized the production of short-chain fatty acids (SCFAs) that was perturbed during HFD-induced obesity, and these stabilizing effects were more prominent when the basal diet was switched to NCD. The enrichment of bacteria of the S24-7 family and Allobaculum genus increased markedly in the intestine following 6% CSF supplementation- and correlated with decreased adiposity and insulin resistance. Five bacterial genera that were decreased by CSF, including Oscillospira, unclassified Lachonospitaceae, unclassified Clostridiales, unclassified Desulfovibrionaceae, and unclassified Ruminococcae, were subjected to co-occurrence network analysis and were positively correlated to adiposity and insulin resistance, indicating a key role in the microbial response to CSF. Thus, CSF has a potential to promote insulin sensitivity and even reduce obesity via beneficial regulation of the gut microecosystem.

Bis(ethylmaltolato)oxidovanadium(iv) inhibited the pathogenesis of Alzheimer's disease in triple transgenic model mice.

Vanadium compounds have been reported to mimic the anti-diabetes effects of insulin on rodent models, but their effects on Alzheimer's disease (AD) have rarely been explored. In this paper, 9-month-old triple transgenic AD model mice (3×Tg-AD) received bis(ethylmaltolato)oxidovanadium(iv) (BEOV) at doses of 0.2 mmol L-1 (68.4 μg mL-1) and 1.0 mmol L-1 (342 μg mL-1) for 3 months. BEOV at both doses was found to improve contextual memory and spatial learning in AD mice. It also improved glucose metabolism and protected neuronal synapses in the AD brain, as evidenced respectively by 18F-labeled fluoro-deoxyglucose positron emission tomography (18F-FDG-PET) scanning and by transmission electron microscopy. Inhibitory effects of BEOV on β-amyloid (Aβ) plaques and neuronal impairment in the cortex and hippocampus of fluorescent AD mice were visualized three-dimensionally by applying optical clearing technology to brain slices before confocal laser scanning microscopy. Western blot analysis semi-quantitatively revealed the altered levels of Aβ42 in the brains of wildtype, AD, and AD treated with 0.2 and 1.0 mmol L-1 BEOV mice (70.3%, 100%, 83.2% and 56.8% in the hippocampus; 82.4%, 100%, 66.9% and 42% in the cortex, respectively). The mechanism study showed that BEOV increased the expression of peroxisome proliferator-activated receptor γ (PPARγ) (140%, 100%, 142% and 160% in the hippocampus; 167%, 100%, 124% and 133% in the cortex) to inactivate the JAK2/STAT3/SOCS-1 pathway and to block the amyloidogenesis cascade, thus attenuating Aβ-induced insulin resistance in AD models. BEOV also reduced protein tyrosine phosphatase 1B (PTP1B) expression (74.8%, 100%, 76.5% and 53.8% in the hippocampus; 71.8%, 100%, 94.2% and 81.8% in cortex) to promote insulin sensitivity and to stimulate the PI3K/Akt/GSK3β pathway, subsequently reducing tau hyperphosphorylation (phosphorylated tau396 levels were 51.1%, 100%, 56.1% and 50.2% in the hippocampus; 22.2%, 100%, 36.1%, and 24% in the cortex). Our results suggested that BEOV reduced the pathological hallmarks of AD by targeting the pathways of PPARγ and PTP1B in 3×Tg AD mice.

Sestrins are evolutionarily conserved mediators of exercise benefits

Exercise is among the most effective interventions for age-associated mobility decline and metabolic dysregulation. Although long-term endurance exercise promotes insulin sensitivity and expands respiratory capacity, genetic components and pathways mediating the metabolic benefits of exercise have remained elusive. Here, we show that Sestrins, a family of evolutionarily conserved exercise-inducible proteins, are critical mediators of exercise benefits. In both fly and mouse models, genetic ablation of Sestrins prevents organisms from acquiring metabolic benefits of exercise and improving their endurance through training. Conversely, Sestrin upregulation mimics both molecular and physiological effects of exercise, suggesting that it could be a major effector of exercise metabolism. Among the various targets modulated by Sestrin in response to exercise, AKT and PGC1α are critical for the Sestrin effects in extending endurance. These results indicate that Sestrin is a key integrating factor that drives the benefits of chronic exercise to metabolism and physical endurance.

Low prolactin levels are associated with visceral adipocyte hypertrophy and insulin resistance in humans.

Low prolactin (PRL) serum levels are associated with glucose intolerance and type 2 diabetes in adults, and with metabolic syndrome and obesity in children. In obese rodents, PRL treatment promotes insulin sensitivity by maintaining adipose tissue fitness, and lack of PRL signaling exacerbates obesity-derived metabolic alterations. Since adipose tissue dysfunction is a key factor triggering metabolic alterations, we evaluated whether PRL serum levels are associated with adipocyte hypertrophy (a marker of adipose tissue dysfunction), insulin resistance, and metabolic syndrome in lean, overweight, and obese adult men and women. Samples of serum and adipose tissue from 40 subjects were obtained to evaluate insulin resistance index (homeostasis model assessment of insulin resistance (HOMA-IR)), signs of metabolic syndrome (glucose levels, high-density lipoproteins, triglycerides, blood pressure, and waist circumference), as well as adipocyte size and gene expression in fat. Lower PRL serum levels are associated with adipocyte hypertrophy, in visceral but not in subcutaneous fat, and with a higher HOMA-IR. Furthermore, low systemic PRL levels together with high waist circumference predict an elevated HOMA-IR whereas low serum PRL values in combination with high blood glucose predicts visceral adipocyte hypertrophy. In agreement, visceral fat from insulin resistant subjects shows reduced expression of prolactin receptor. However, there is no association between PRL levels and obesity or signs of metabolic syndrome. Our results support that low levels of PRL are markers of visceral fat dysfunction and insulin resistance, and suggest the potential therapeutic value of medications elevating PRL levels to help maintain metabolic homeostasis.

Adiponectin links maternal metabolism to uterine contractility.

Adiponectin is secreted by adipose tissue and promotes insulin sensitivity. Low circulating adiponectin is associated with increased risk for preterm labor, but the influence of adiponectin on uterine myometrial physiology is unknown. We hypothesized that adiponectin receptors (AdipoRs) decrease myometrial contractility via AMPK to promote uterine quiescence in pregnancy. Using quantitative RT-PCR, we found that nonpregnant or pregnant human and mouse myometrium express AdipoR1 and AdipoR2 mRNAs. We confirmed AdipoR2 protein expression in human and mouse myometrium, with increased abundance in late mouse pregnancy. Both recombinant adiponectin and a pharmacologic AdipoR agonist, AdipoRon, potently inhibited uterine myometrial strip contractions in physiologic organ bath. The relaxation was independent of contractile stimulus (oxytocin, KCl, U46619). AdipoR agonists increased AMPK phosphorylation in pregnant mouse myometrium, and the direct AMPK activator A769662 also relaxed myometrial strips. However, the AMPK inhibitor dorsomorphin (compound C) blocked AMPK phosphorylation but did not abolish relaxation with either AdipoRon or A769662. In summary, adiponectin inhibits myometrial contractility consistent with the possibility that it is a previously unrecognized link between maternal metabolism and pregnancy maintenance. We also identify a separate role for AMPK regulating myometrial contractions that may influence labor onset.-Vyas, V., Guerra, D. D., Bok, R., Powell, T., Jansson, T., Hurt, K. J. Adiponectin links maternal metabolism to uterine contractility.

Adipocyte PU.1 knockout promotes insulin sensitivity in HFD-fed obese mice

Insulin resistance is a key feature of obesity and type 2 diabetes. PU.1 is a master transcription factor predominantly expressed in macrophages but after HFD feeding PU.1 expression is also significantly increased in adipocytes. We generated adipocyte specific PU.1 knockout mice using adiponectin cre to investigate the role of PU.1 in adipocyte biology, insulin and glucose homeostasis. In HFD-fed obese mice systemic glucose tolerance and insulin sensitivity were improved in PU.1 AKO mice and clamp studies indicated improvements in both adipose and liver insulin sensitivity. At the level of adipose tissue, macrophage infiltration and inflammation was decreased and glucose uptake was increased in PU.1 AKO mice compared with controls. While PU.1 deletion in adipocytes did not affect the gene expression of PPARg itself, we observed increased expression of PPARg target genes in eWAT from HFD fed PU.1 AKO mice compared with controls. Furthermore, we observed decreased phosphorylation at serine 273 in PU.1 AKO mice compared with fl/fl controls, indicating that PPARg is more active when PU.1 expression is reduced in adipocytes. Therefore, in obesity the increased expression of PU.1 in adipocytes modifies the adipocyte PPARg cistrome resulting in impaired glucose tolerance and insulin sensitivity.

Transcription-based circadian mechanism controls the duration of molecular clock states in response to signaling inputs

The molecular oscillator of the mammalian circadian clock consists in a dynamical network of genes and proteins whose main regulatory mechanisms occur at the transcriptional level. From a dynamical point of view, the mechanisms leading to an oscillatory solution with an orderly protein peak expression and a clear day/night phase distinction remain unclear. Our goal is to identify the essential interactions needed to generate phase opposition between the activating CLOCK:BMAL1 and the repressing PER:CRY complexes and to better distinguish these two main clock molecular phases relating to rest/activity and fast/feeding cycles. To do this, we develop a transcription-based mathematical model centered on linear combinations of the clock controlled elements (CCEs): E-box, R-box and D-box. Each CCE is responsive to activators and repressors. After model calibration with single-cell data, we explore entrainment and period tuning via interplay with metabolism. Variation of the PER degradation rate γp, relating to the tau mutation, results in asymmetric changes in the duration of the different clock molecular phases. Time spent at the state of high PER/PER:CRY decreases with γp, while time spent at the state of high BMAL1 and CRY1, both proteins with activity in promoting insulin sensitivity, remains constant. This result suggests a possible mechanism behind the altered metabolism of tau mutation animals. Furthermore, we expose the clock system to two regulatory inputs, one relating to the fast/feeding cycle and the other to the light-dependent synchronization signaling. We observe the phase difference between these signals to also affect the relative duration of molecular clock states. Simulated circadian misalignment, known to correlate with insulin resistance, leads to decreased duration of BMAL1 expression. Our results reveal a possible mechanism for clock-controlled metabolic homeostasis, whereby the circadian clock controls the relative duration of different molecular (and metabolic) states in response to signaling inputs.

The Effects of Metformin on Age-Related Changes in the Liver Sinusoidal Endothelial Cell.

Age-related changes in the liver sinusoidal endothelium, particularly the reduction in fenestrations, contribute to insulin resistance in old age. Metformin impacts on the aging process and improves insulin resistance. Therefore, the effects of metformin on the liver sinusoidal endothelium were studied. Metformin increased fenestrations in liver sinusoidal endothelial cells isolated from both young and old mice. Mice administered metformin in the diet for 12 months had increased fenestrations and this was associated with lower insulin levels. The effect of metformin on fenestrations was blocked by inhibitors of AMP-activated protein kinase (AMPK), endothelial nitric oxide synthase, and myosin light chain kinase phosphorylation. Metformin led to increased transgelin expression and structural changes in the actin cytoskeleton but had no effect on lactate production. Metformin also generated fenestration-like structures in SK-Hep1 cells, a liver endothelial cell line, and this was associated with increased ATP, cGMP, and mitochondrial activity. In conclusion, metformin ameliorates age-related changes in the liver sinusoidal endothelial cell via AMPK and endothelial nitric oxide pathways, which might promote insulin sensitivity in the liver, particularly in old age.

2094-P: Decreased Human Adipose Tissue-Resident Eosinophils in Obese Subjects Is Associated with Increased Insulin Resistance

Eosinophils (EOS) have been shown to play a major role in animal adipose tissue (AT) metabolism by promoting insulin sensitivity (IS) through an increase in alternatively activated macrophages (M2). Additionally, AT EOS are known to be decreased in obese mice. Currently, translational evidence is lacking for the role of EOS in human AT metabolism and IS. We investigated whether human AT-resident EOS numbers, as in animal models, are decreased in obese subjects and correlate with their degree of insulin resistance (IR). To date, we have studied 16 lean subjects (F15/M1, age 43 +2 years old; BMI 22.5+0.4kg/m2; HOMA-IR: 0.99 +0.38) and 22 obese, IR subjects (17F/5M, age 42 +1.3 years old; BMI: 38.9 +1.0kg/m2; HOMA-IR:5.0 +1.6) undergoing elective laparoscopic surgery. During surgical procedure, subcutaneous (SC) and omental (OM) fat was harvested. Stromal vascular fraction (SVF) was isolated after collagenase digestion of the fat samples. SVF was subjected to FACS analysis using BD Biosciences FACSAria III Cell Sorter with EOS count normalized as percent of CD45+ cells. Viable EOS were isolated and cytospin preparation was stained with a Diff-Quik. EOS isolated from SC AT of lean(L) subjects were found to significantly outnumber those obtained from obese (Ob) subjects by a 2.1:1 ratio (SC L:2.34 +0.29 vs. SC Ob: 1.11 +0.21, P<0.03). A similar, but non-significant, trend was observed in OM. Furthermore, the number of SC AT-EOS was significantly inversely correlated with BMI, % fat and QUICKI index. qPCR analysis of SC AT mRNA revealed significantly increased classically activated macrophage markers (M1) (IL-1, IL-6, TNFα) in Ob vs. L, respectively while M2 markers (ARG-1, CCL24, CCL26) were significantly decreased in Ob vs. L. Based on these results we propose that, as in animal models, AT-resident EOS mediate AT metabolism and potentially IS by preserving an anti-inflammatory milieu within lean AT. Further studies are needed to elucidate the mechanism(s) involved. Disclosure J.D. Hernandez: None. T. Li: None. C. Rau: None. M.Y. Masuda: None. J.A. Madura: None. E.A. Jacobsen: None. E. DeFilippis: None. Funding Arizona Department of Health Services (14-00003606); Arizona Biomedical Research Commission; Kathryn H. and Roger Penske Career Development Award

143-LB: Calorie Restriction in Combination with GABA Ameliorates Type 2 Diabetes

Dysfunction of adipocytes and β-cells are crucial in the progression of obesity-related insulin resistance and type 2 diabetes (T2D). γ-Aminobutyric Acid (GABA) is a key neurotransmitter and is secreted by β-cells. It exerts protective and regenerative effects on β-cells. At the metabolic level, Calorie Restriction (CR) has been shown to improve insulin sensitivity, reduces Fasting Blood Glucose (FBG) and increases insulin levels. GABA and CR are speculated to show an additive effect on insulin secretion and β-cell regeneration via GABA signaling and enhance insulin sensitivity ameliorating T2D manifestations. We have evaluated the effect of GABA and CR combination on β-cell regeneration and insulin sensitivity in High Fat Diet (HFD) and streptozotocin (STZ) induced late stage T2D mouse model. Our results show favorable changes in the measured parameters. GABA+CR group showed reduced FBG levels and improved whole-body insulin responsiveness indicated by increased insulin levels, insulin sensitivity, and glucose tolerance. The combination therapy improved the lipid profile by significantly reducing triglycerides, total cholesterol, and LDL levels and increased HDL levels. The transcript expression profile of metabolic enzymes in the liver indicates a significant decrease in gluconeogenesis and glycogenolysis. The transcript levels indicate decreased lipolysis and increased fatty acid synthesis in the adipose tissue. The transcript levels of mitochondrial biogenesis in the skeletal muscle indicate increased effect of combination therapy, thereby promoting insulin sensitivity. Also, combination therapy promoted β-cell proliferation. In conclusion, calorie restriction in combination with GABA ameliorates T2D in the mouse model by inducing β-cell regeneration mediated by GABA and increased insulin sensitivity by CR diet. Disclosure N.N. Rathwa: None. R. Patel: None. S. Pramanik: None. N.R. Parmar: None. R. A.v.: None. R. Begum: None. Funding Department of Biotechnology, New Delhi, India (BT/PR21242/MED/30/1750/2016)

Consumption of Whole Eggs Promotes Insulin Sensitivity in Db/db Mice (OR34-01-19)

ObjectivesChicken eggs have a high nutrient density. Some country guidelines recommend that people with type 2 diabetes (T2D) limit their consumption of eggs due to its high cholesterol content. However, several clinical studies showed that egg intake is associated with a lower risk of type 2 diabetes. In the current study, we sought to explore whether egg consumption improves insulin sensitivity and subsequent blood glucose management in type 2 diabetic db/db mice. MethodsSix-week-old male db/db mice were fed a low-fat diet (LFD, 10 kCal % from fat) or LFD supplemented with 1% whole eggs (Egg) for 8 weeks. At the termination of the study, mice were fasted for 3 hrs prior to euthanization. Blood and other tissues were collected for laboratory assessments. Plasma metabolic parameters and pro-inflammatory cytokines were monitored by a clinical analyzer and ELISA, respectively. Hepatic and skeletal muscle mitochondrial respiratory activity was assessed by a Seahorse XFe Analyzer. Hepatic gene expression was analyzed by transcriptomics and confirmed by real-time PCR and/or Western blot. ResultsEgg consumption significantly increased body weight gain, lowered fasting blood glucose, insulin, and IL-6 levels, and elevated total cholesterol, HDL, LDL, and GLP-1 levels. Only the basal mitochondrial respiratory activity was decreased, and the complex II respiratory activity was increased in gastrocnemius muscles in mice fed Egg. Hepatic mitochondrial activity was not altered by diet. Mechanistically, transcriptomics results revealed that hepatic genes involved in enhanced insulin sensitivity were highly expressed, but genes in endogenous cholesterol synthesis were significantly suppressed after egg consumption. ConclusionsThe results suggest that egg consumption is beneficial to blood glucose control in type 2 diabetic mice. Type 2 diabetic animal could manage the cholesterol level through suppression of de novo cholesterol synthesis when consuming a high cholesterol diet, e.g., egg diet. Funding SourcesNational egg nutrition center grant USDA NIFA grant

2030-P: BS-016, a Novel Oleanolic Acid Derivative, Exerts Antidiabetic and Anti-Obesity Effects in Preclinical Studies

There is an urgent need for innovative treatment targeting multiple pathways of type 2 diabetes such as weight loss, insulin sensitization and beta cell proliferation. Natural products have been shown to have the potential to treat diabetes. Here we develop a novel compound from oleanolic acid with improved bioavailability and efficacy. BS-016 reduces blood glucose and induces a sustained weight loss in DIO mice, producing 15% weight loss in combination study. In db/db diabetic mice, BS-016 lowers plasma glucose and improves glucose homeostasis. In vitro studies show BS-016 promotes insulin sensitivity by activating PPAR gamma and increases energy expenditure. Taken together, these results indicate BS-016 is a promising agent for treating diabetes and obesity. Disclosure Y. Du: None.

Lipids and insulin regulate mitochondrial-derived peptide (MOTS-c) in PCOS and healthy subjects.

Polycystic ovarian syndrome (PCOS) is a heterogeneous endocrine disorder associated with mitochondrial dysfunction and insulin resistance (IR). MOTS-c, a mitochondrial peptide, promotes insulin sensitivity (IS) through activating AKT and AMPK-dependent pathways. The current study was designed to examine the response of MOTS-c to lipids (intralipid) followed by insulin in PCOS and healthy subjects. All subjects underwent 5-hour intralipid/saline infusion with a hyperinsulinemic-euglycaemic clamp in the final 2hours. Plasma samples were collected to measure circulating MOTS-c using a commercial ELISA kit. Subsequently, this was repeated following an eight-week exercise intervention. Intralipid significantly increased plasma MOTS-c both in controls and PCOS subjects, whilst the insulin infusion blunted the intralipid-induced response seen for both lipids and MOT-c. Intralipid elevated plasma MOTS-c to 232±124% of basal in control (P<0.01) and to 349±206% of basal in PCOS (P<0.001) subjects. Administration of insulin suppressed intralipid-induced MOTS-c from 232±124% to 165±97% (NS) in control and from 349±206% to 183±177% (P<0.05) in PCOS subjects, respectively. Following exercise, intralipid elevated plasma MOTS-c to 305±153% of basal in control (P<0.01) and to 215±103% of basal in PCOS (P<0.01) subjects; insulin suppressed intralipid-induced MOTS-c only in controls. In conclusion, this is the first study to show increased lipid enhanced circulating MOTS-c whilst insulin attenuated the MOTS-c response in human. Further, eight weeks of moderate exercise training did not show any changes in circulating MOTS-c levels in healthy controls and in women with PCOS.

Vaspin promotes insulin sensitivity of elderly muscle and is upregulated in obesity.

Adipokines have emerged as central mediators of insulin sensitivity and metabolism, in part due to the known association of obesity with metabolic syndrome disorders such as type 2 diabetes. Recent studies in rodents have identified the novel adipokine vaspin, as playing a protective role in inflammatory metabolic diseases by functioning to promote insulin sensitivity during metabolic stress. However, at present the skeletal muscle and adipose tissue expression of vaspin in humans is poorly characterised. Furthermore, the functional role of vaspin in skeletal muscle insulin sensitivity has not been studied. Since skeletal muscle is the major tissue for insulin-stimulated glucose uptake understanding the functional role of vaspin in human muscle insulin signalling is critical in determining its role in glucose homeostasis. The objective of this study was to profile the skeletal muscle and subcutaneous adipose tissue expression of vaspin in humans of varying adiposity and to determine the functional role of vaspin in mediating insulin signalling and glucose uptake in human skeletal muscle. Our data shows that vaspin is secreted from both human subcutaneous adipose tissue and skeletal muscle, and is more highly expressed in obese older individuals compared to lean older individuals. Furthermore, we demonstrate that vaspin induces activation of the PI3K/AKT axis, independent of insulin receptor activation, promotes GLUT4 expression and translocation and sensitises older obese human skeletal muscle to insulin-mediated glucose uptake.

DOC2B promotes insulin sensitivity in mice via a novel KLC1-dependent mechanism in skeletal muscle.

Skeletal muscle accounts for >80% of insulin-stimulated glucose uptake; dysfunction of this process underlies insulin resistance and type 2 diabetes. Insulin sensitivity is impaired in mice deficient in the double C2 domain β (DOC2B) protein, while whole-body overexpression of DOC2B enhances insulin sensitivity. Whether insulin sensitivity in the skeletal muscle is affected directly by DOC2B or is secondary to an effect on other tissues is unknown; the underlying molecular mechanisms also remain unclear. Human skeletal muscle samples from non-diabetic or type 2 diabetic donors were evaluated for loss of DOC2B during diabetes development. For in vivo analysis, new doxycycline-inducible skeletal-muscle-specific Doc2b-overexpressing mice fed standard or high-fat diets were evaluated for insulin and glucose tolerance, and insulin-stimulated GLUT4 accumulation at the plasma membrane (PM). For in vitro analyses, a DOC2B-overexpressing L6-GLUT4-myc myoblast/myotube culture system was coupled with an insulin resistance paradigm. Biochemical and molecular biology methods such as site-directed mutagenesis, co-immunoprecipitation and mass spectrometry were used to identify the molecular mechanisms linking insulin stimulation to DOC2B. We identified loss of DOC2B (55% reduction in RNA and 40% reduction in protein) in the skeletal muscle of human donors with type 2 diabetes. Furthermore, inducible enrichment of DOC2B in skeletal muscle of transgenic mice enhanced whole-body glucose tolerance (AUC decreased by 25% for female mice) and peripheral insulin sensitivity (area over the curve increased by 20% and 26% for female and male mice, respectively) in vivo, underpinned by enhanced insulin-stimulated GLUT4 accumulation at the PM. Moreover, DOC2B enrichment in skeletal muscle protected mice from high-fat-diet-induced peripheral insulin resistance, despite the persistence of obesity. In L6-GLUT4-myc myoblasts, DOC2B enrichment was sufficient to preserve normal insulin-stimulated GLUT4 accumulation at the PM in cells exposed to diabetogenic stimuli. We further identified that DOC2B is phosphorylated on insulin stimulation, enhancing its interaction with a microtubule motor protein, kinesin light chain 1 (KLC1). Mutation of Y301 in DOC2B blocked the insulin-stimulated phosphorylation of DOC2B and interaction with KLC1, and it blunted the ability of DOC2B to enhance insulin-stimulated GLUT4 accumulation at the PM. These results suggest that DOC2B collaborates with KLC1 to regulate insulin-stimulated GLUT4 accumulation at the PM and regulates insulin sensitivity. Our observation provides a basis for pursuing DOC2B as a novel drug target in the muscle to prevent/treat type 2 diabetes.

MicroRNA-125b-5p improves pancreatic β-cell function through inhibiting JNK signaling pathway by targeting DACT1 in mice with type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a progressive disease, accompanied by increased insulin resistance and deteriorating β-cell function. Previous studies have revealed that microRNA (miRNA) plays a crucial role in the treatment of T2DM. Hence, we aim to investigate the role of microRNA-125b-5p (miR-125b-5p) in pancreatic β-cell function and insulin sensitivity of mice with T2DM with the involvement of Dishevelled antagonist Dapper1 (DACT1) and the c-Jun NH2-terminal kinases (JNK) signaling pathway. Firstly, a mouse model of T2DM was established by administering a high-fat diet plus low dosage of streptozotocin, and function of pancreatic β-cell and insulin sensitivity in the normal and T2DM mice were detected. Then, the pancreatic β-cells were collected from pancreatic islet tissues and treated with different mimics, inhibitors and siRNAs. After that, the relationship among miR-125b-5p, DACT1, and the JNK signaling-related factors in T2DM mice was determined. Finally, cell proliferation and apoptosis were determined. Mice with T2DM had lower pancreatic β-cell function and insulin sensitivity, as well as diminished expression of miR-125b-5p but enhanced expressions of DACT1, JNK and c-Jun. miR-125b-5p inhibited DACT1 expression and the activation of the JNK signaling pathway, as well as restrained cell proliferation and promoted cell apoptosis. The current results suggest that up-regulated miR-125b-5p promotes insulin sensitivity and enhances pancreatic β-cell function through inhibiting the JNK signaling pathway by negatively mediating DACT1.

PO-029 Advances in research on hypoxia-mediated miRNAs affecting glucose metabolism

Objective This article reviews the role of miRNAs in promoting insulin sensitivity, controlling insulin synthesis, and regulating insulin resistance in hypoxia exercise, and discusses the relationship between miRNAs and glucose metabolism, and the mechanism of hypoxia-induced regulation of miRNAs in glucose metabolism. It provides a theoretical basis for better research on the prevention and treatment of disorders of glucose metabolism.&#x0D; Methods This paper uses the literature data method, collects a large number of documents and cites more than 90 articles for comprehensive statistical analysis to write this article, which provides researchers with relevant research directions.&#x0D; Results Studies have shown that miRNAs such as miR-138, miR-26b, miR-27a, miR-122, miR-802 and miR-143 have regulatory effects on obesity; some miRNAs such as miR-128, miR-7, miR-25, miR -92a, miR-375 and miR-15 family (miR-15a and miR-15b) and other miRNAs play an important role in regulating glycolipid metabolism, thereby maintaining a stable state of glycolipid metabolism. Expressions such as miR-802 and miR-143 are up-regulated in the liver of obese patients, resulting in impaired glucose tolerance.&#x0D; Conclusions By regulating the expression of target genes and maintaining the homeostasis of glucose metabolism, miRNAs can effectively improve or prevent obesity and disorders of glucose metabolism such as type 2 diabetes. Current studies have shown that miRNAs affect glucose metabolism from insulin sensitivity, insulin synthesis and insulin resistance. At the same time, studies have shown that exercise intervention can effectively improve glucose metabolism. However, the research on the metabolism of miRNAs in glucose metabolism during hypoxia is still insufficient. It is for further study. Studying the mechanism of the effects of miRNAs on glucose metabolism in hypoxic exercise can not only provide a theoretical basis for scientific hypoglycemic and weight control, but also can be used as an intervention for the prevention and control of diseases related to glucose metabolism disorders. In the future, drugs can regulate the expression of miRNAs, thereby providing a new therapeutic approach for the treatment of diseases caused by abnormal glucose and lipid metabolism.

Adiponectin and Chemerin: Contrary Adipokines in Regulating Reproduction and Metabolic Disorders.

Metabolic disorders such as obesity and type 2 diabetes are one of the most familiar risk factors in the present time among every age-group. It is associated with altered levels of adipokines such as adiponectin, chemerin, leptin, resistin, visfatin, and so on. Adiponectin is one of the adipocyte-specific protein with novel applications pertaining to metabolism by promoting insulin sensitivity and regulating glucose and fatty acid catabolism, while chemerin is considered as an inhibitor of insulin signaling and glucose catabolism. Other than these established functions, both the adipokines are intimately involved in coordinating reproductive activities, but they exhibit contrary functions. This review is an amalgamation of recent information related to adiponectin and chemerin in male and female reproduction and further its association with metabolism-related reproductive disorders. The direct effect of adiponectin and chemerin on various reproductive parameters has been investigated, but there was a rampant failure to account for in vivo data which gives a broad outlook on the regulatory mechanism of both adiponectin and chemerin related to male and female reproductive functions. Adiponectin is known to promote gonadal activities, while chemerin exerts antigonadal actions. Recent research suggests that high chemerin/low adiponectin ratio plays a vital role in causing dyslipidemia and metabolic syndrome in patients. The dysregulated ratio of adiponectin to chemerin during various metabolic disorders makes it really worthy in relation to an application for therapeutics. Still, a lot regarding both the adipokines has to be explored and brought forward in order to deal with therapeutics of metabolism-related reproductive disorders.