Diet-induced Glucose Intolerance Research Articles

Selenoprotein F knockout leads to glucose and lipid metabolism disorders in mice.

Selenoprotein F (Selenof), an endoplasmic reticulum (ER)-resident protein, is considered to be involved in glycoprotein folding and quality control in the ER. However, its function has not yet been thoroughly addressed. In this study, proteomics analysis revealed that Selenof deficiency in mice led to the differential expression of hepatic proteins associated with glucose and lipid metabolism. The phenotype analysis revealed that Selenof knockout mice showed glucose intolerance and insulin reduction, even with a normal diet. Additionally, Selenof knockout exacerbated high-fat diet-induced obesity, hyperglycemia, glucose intolerance, and hepatic steatosis. Furthermore, lipoprotein lipase and carboxylesterase 1D, two glycoproteins involved in lipid metabolism, were significantly decreased in the liver of Selenof knockout mice with a normal or high-fat diet. Collectively, these findings suggested that Selenof deficiency might cause the perturbation of glycoprotein quality control and thus contribute to glucose and lipid metabolism disorders, implying a novel biological function of Selenof.

Neuronatin regulates whole-body metabolism: is thermogenesis involved?

Neuronatin (NNAT) was originally discovered in 1995 and labeled as a brain developmental gene due to its abundant expression in developing brains. Over the past 25 years, researchers have uncovered NNAT in other tissues; notably, the hypothalamus, pancreatic β‐cells, and adipocytes. Recent evidence in these tissues indicates that NNAT plays a significant role in metabolism whereby it regulates food intake, insulin secretion, and adipocyte differentiation. Furthermore, genetic deletion of Nnat in mice lowers whole‐body energy expenditure and increases susceptibility to diet‐induced obesity and glucose intolerance; however, the underlying cellular mechanisms remain unknown. Based on its sequence homology with phospholamban, NNAT has a purported role in regulating the sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA) pump. However, NNAT also shares sequence homology with sarcolipin, which has the unique property of uncoupling the SERCA pump, increasing whole‐body energy expenditure and thus promoting adaptive thermogenesis in states of caloric excess or cold exposure. Thus, in this article, we discuss the accumulating evidence suggestive of NNAT’s role in whole‐body metabolic regulation, while highlighting its potential to mediate adaptive thermogenesis via SERCA uncoupling.

Myricetin derivative-rich fraction from Syzygium malaccense prevents high-fat diet-induced obesity, glucose intolerance and oxidative stress in C57BL/6J mice

Aim A high-fat diet (HFD) can lead to obesity and related metabolic disorders. This study evaluated the preventive efficacy of myricetin derivative-rich fraction (MD) from Syzygium malaccense leaf extract against HFD-induced obesity, hyperglycaemia, and oxidative stress in C57BL/6J mice. Methods HFD-fed mice were administered MD (50 mg/kg, 100 mg/kg, and 150 mg/kg) or 2 mg/kg metformin (positive control) orally for 16 weeks. Normal diet and HFD-fed control groups received normal saline. Results MD dose of 50 mg/kg was better than 100 mg/kg and 150 mg/kg in significantly reducing weight-gain, glucose intolerance, insulin resistance, lipid accumulation in liver and kidney, and improving the serum lipid profile. Lowered protein carbonyls and lipid hydroperoxides in urine and tissue homogenates and elevated reduced glutathione, ferric reducing antioxidant power (FRAP), and Trolox equivalent antioxidant capacity (TEAC) levels in tissue homogenates indicated amelioration of oxidative stress. Conclusion MD has therapeutic value in the prevention and management of obesity, hyperglycaemia, and oxidative stress.

Exploring the Mediators that Promote Carotid Body Dysfunction in Type 2 Diabetes and Obesity Related Syndromes.

Carotid bodies (CBs) are peripheral chemoreceptors that sense changes in blood O2, CO2, and pH levels. Apart from ventilatory control, these organs are deeply involved in the homeostatic regulation of carbohydrates and lipid metabolism and inflammation. It has been described that CB dysfunction is involved in the genesis of metabolic diseases and that CB overactivation is present in animal models of metabolic disease and in prediabetes patients. Additionally, resection of the CB-sensitive nerve, the carotid sinus nerve (CSN), or CB ablation in animals prevents and reverses diet-induced insulin resistance and glucose intolerance as well as sympathoadrenal overactivity, meaning that the beneficial effects of decreasing CB activity on glucose homeostasis are modulated by target-related efferent sympathetic nerves, through a reflex initiated in the CBs. In agreement with our pre-clinical data, hyperbaric oxygen therapy, which reduces CB activity, improves glucose homeostasis in type 2 diabetes patients. Insulin, leptin, and pro-inflammatory cytokines activate the CB. In this manuscript, we review in a concise manner the putative pathways linking CB chemoreceptor deregulation with the pathogenesis of metabolic diseases and discuss and present new data that highlight the roles of hyperinsulinemia, hyperleptinemia, and chronic inflammation as major factors contributing to CB dysfunction in metabolic disorders.

Genetic ablation of Fas-activated serine/threonine kinase ameliorates obesity-related hepatic glucose and lipid metabolic disorders via sirtuin-1 signaling

Obesity has become a worldwide pandemic and is associated with various metabolic diseases such as type 2 diabetes mellitus and non-alcoholic fatty liver disease. Fas-activated serine/threonine kinase (Fastk) is a multifunctional protein localized in the mitochondrion; however, the role of Fastk in obesity-related metabolic disorders remains unexplored. Here we found that Fastk expression was specifically induced in livers of high fat (HF) diet-fed mice and in saturated fatty acid (such as palmitate)-loaded hepatocytes. Genetic ablation of Fastk ameliorated HF diet-induced insulin resistance, glucose intolerance, and hepatic steatosis. Further studies confirmed that Fastk knockout suppressed hepatic gluconeogenesis and lipogenesis in HF diet-stressed livers and in palmitate-loaded hepatocytes. Mechanistically, Fastk ablation significantly preserved sirtuin-1 (SIRT1) expression and activity in livers of HF diet-fed mice and in palmitate-loaded hepatocytes. Inhibition of SIRT1 activity by EX-527 (a specific inhibitor of SIRT1) totally abolished the suppressive effects of Fastk knockout on gluconeogenesis and lipogenesis in cultured hepatocytes. In conclusion, these data for the first time demonstrate that Fastk critically controls hepatic gluconeogenesis and lipogenesis mainly through modulating SIRT1 signaling. Intervening Fastk expression or activity might be a promising therapeutic strategy for the treatment of obesity-associated metabolic diseases.

Reduced Nogo expression inhibits diet-induced metabolic disorders by regulating ChREBP and insulin activity

Chronic overconsumption of a high-carbohydrate diet leads to steatosis and its associated metabolic disorder and, eventually, to non-alcoholic fatty liver disease. Carbohydrate-responsive element binding protein (ChREBP) and insulin regulate de novo lipogenesis from glucose. Herein, we studied the effect of reticulon-4 (Nogo) expression on diet-induced metabolic disorders in mice. Nogo-deficient (Nogo-/-) and littermate control [wild-type (WT)] mice were fed a high-glucose or high-fructose diet (HGD/HFrD) to induce metabolic disorders. The effects of Nogo small interfering (si) RNA (siRNA) on HFrD-induced metabolic disorders were investigated in C57BL/6J mice. HGD/HFrD induced steatosis and its associated metabolic disorders in WT mice by activating ChREBP and impairing insulin sensitivity. They also activated Nogo-B expression, which in turn inhibited insulin activity. In response to HGD/HFrD feeding, Nogo deficiency enhanced insulin sensitivity and energy metabolism to reduce the expression of ChREBP and lipogenic molecules, activated AMP-activated catalytic subunit α, peroxisome proliferator activated receptor α and fibroblast growth factor 21, and reduced endoplasmic reticulum (ER) stress and inflammation, thereby blocking HGD/HFrD-induced hepatic lipid accumulation, insulin resistance and other metabolic disorders. Injection of Nogo siRNA protected C57BL/6J mice against HFrD-induced metabolic disorders by ameliorating insulin sensitivity, ChREBP activity, ER stress and inflammation. Our study identified Nogo as an important mediator of insulin sensitivity and ChREBP activity. Reduction of Nogo expression is a potential strategy for the treatment of high-carbohydrate diet-induced metabolic complications. Nogo deficiency blocks high-carbohydrate diet-induced glucose intolerance and insulin resistance, while increasing glucose/lipid utilisation and energy expenditure. Thus, reduction of Nogo expression protects against high-carbohydrate diet-induced body-weight gain, hepatic lipid accumulation and the associated metabolic disorders, indicating that approaches inhibiting Nogo expression can be applied for the treatment of diseases associated with metabolic disorders.

Liraglutide shows superior cardiometabolic benefits than lorcaserin in a novel free choice diet-induced obese rat model

Lorcaserin (LORCA) and liraglutide (LIRA) were evaluated in a novel diet-induced obese (DIO) rat model fed a free choice (FC) diet, that presents rats with the options between control chow (CC) or high fat/cholesterol (HFC) diet, and normal water (NW) or 10% fructose water (FW).After 8 weeks of FC diet-induced obesity/insulin resistance, rats were maintained on FC diet and treated daily for 5 weeks with vehicle, LORCA 18 mg/kg orally or LIRA 0.4 mg/kg subcutaneously.Compared to CC diet, FC diet resulted in higher intake of HFC and FW, and significantly higher caloric intake and overweight. LIRA induced a lower HFC/FW and higher CC/NW intake, a 12% body weight loss (P < 0.01 vs. FC) and 40% lower visceral fat mass (P < 0.001). LORCA only reduced HFC intake and body weight gain (P < 0.001 vs. FC).FC diet raised HOMA-IR index and plasma leptinemia by 66% and 165% (both P < 0.05 vs. CC), which were 50% and 70% lower with LIRA (both P < 0.05 vs. FC), but unchanged by LORCA.LIRA and LORCA significantly improved FC diet-induced glucose intolerance. Only LIRA reduced liver fatty acids, triglycerides, and cholesterol by 68, 71 and 51% (all P < 0.001). FC diet also induced a diastolic dysfunction with reduced E/A ratio (P < 0.01 vs. CC), which was improved by LIRA and LORCA (both P < 0.01 vs. FC). LIRA also raised fractional shortening (P < 0.01 vs. FC).Overall, LIRA showed superior cardiometabolic benefits than LORCA in DIO rats under the FC diet, a model that will be useful to evaluate novel drugs targeting obesity and co-morbidities.

Impact of human visceral and glutealfemoral adipose tissue transplant on glycemic control in a mouse model of diet-induced obesity.

Regional distribution of adipose tissue is an important factor in conferring cardiometabolic risk and obesity-related morbidity. We tested the hypothesis that human visceral adipose tissue (VAT) impairs glucose homeostasis, whereas subcutaneous glutealfemoral adipose tissue (GFAT) protects against the development of impaired glucose homeostasis in mice. VAT and GFAT were collected from patients undergoing bariatric surgery and grafted onto the epididymal adipose tissue of weight- and age-matched severe, combined immunodeficient mice. SHAM mice underwent surgery without transplant of tissue. Mice were fed a high-fat diet after xenograft. Energy homeostasis, glucose metabolism, and insulin sensitivity were assessed 6 wk later. Xenograft of human adipose tissues was successful, as determined by histology, immunohistochemical evaluation of collagen deposition and angiogenesis, and maintenance of lipolytic function. Adipose tissue transplant did not affect energy expenditure, food intake, whole body substrate partitioning, or plasma free fatty acid, triglyceride, and insulin levels. Fasting blood glucose was significantly reduced in GFAT and VAT compared with SHAM, whereas glucose tolerance was improved only in mice transplanted with VAT compared with SHAM mice. This improvement was not associated with differences in whole body insulin sensitivity or plasma insulin between groups. Together, these data suggest that VAT improves glycemic control and GFAT does not protect against the development of high-fat diet-induced glucose intolerance. Hence, the intrinsic properties of VAT and GFAT do not necessarily explain the postulated negative and positive effects of these adipose tissue depots on metabolic health.

Fortifying diet with rapeseed oil instead of butterfat attenuates the progression of diet-induced non-alcoholic fatty liver disease (NAFLD) and impairment of glucose tolerance

BackgroundAbsolute dietary fat intake but even more so fatty acid pattern is discussed to be critical in the development of non-alcoholic fatty liver disease (NAFLD). Here, we determined if switching a butterfat enriched diet to a rapeseed oil (RO) enriched diet affects progression of an existing NAFLD and glucose intolerance in mice. MethodsFor eight weeks, female C57Bl/6J mice were either fed a liquid control (C) or a butterfat-, fructose- and cholesterol-rich diet (BFC, 25E% butterfat) to induce early signs of steatohepatitis and glucose intolerance in mice. For additional five weeks mice received either BFC or C or a fat-, fructose- and cholesterol-rich and control diet, in which butterfat was replaced with RO (ROFC and CRO). Markers of glucose metabolism, liver damage and intestinal barrier were assessed. ResultsExchanging butterfat with RO attenuated the progression of BFC diet-induced NAFLD and glucose intolerance. Beneficial effects of RO were associated with lower portal endotoxin levels and an attenuation of the induction of the toll-like receptor-4-dependent signaling cascades in liver. Peroxisome proliferator-activated receptor γ activity was induced in small intestine of ROFC-fed mice. ConclusionTaken together, exchanging butterfat with RO attenuated the progression of diet-induced steatohepatitis and glucose intolerance in mice.

2058-P: Single-Cell Transcriptome Atlas of the Aging Mouse Pancreatic Islet Reveals Resilience to Diet-Induced Obesity

Aging is a key risk factor for type 2 diabetes (T2D). We examined aging mouse pancreatic islets by single-cell RNA-seq sampled across young (1 month), middle (13 months) to old (24 months) age groups. By applying single-cell Western blotting, we further verified that aged mice had increased islet beta-cell percentage, which was accompanied by an increased in vivo insulin secretion. Young and old groups were fed with a six-month high-fat diet. Age-associated enhancements in insulin secretion prevented old mice from diet-induced glucose intolerance. Together, this single-cell atlas allows a comprehensive exploration of all transcriptional states in the aging islets and provides insight into the pathogenesis of T2D. Importantly, our findings indicate that age-dependent hyperinsulinemia protects against diet-induced obesity in mice and exhibit the resilience of the islet in response to stressors. Disclosure J. Nie: None. N. Musi: None. Funding American Federation for Aging Research; San Antonio Claude D. Pepper Older Americans Independence Center (P30AG044271)

Blueberries effects in experimental diet-induced prediabetes: a focus on renal impairment

Abstract Introduction Benefits arising from blueberry (BB) consumption are well-described in type 2 diabetes evolution and inherent complications. Lending further support to this thesis, previous work from our group unequivocally demonstrates BB supplementation efficacy to manage prediabetic hepatic liver steatosis. Whether a similar effect also holds truth in early renal impairment is an unsolved issue. Objectives To address blueberry juice (BJ) ability to exert renoprotective effects in experimental prediabetes. Methodology Diet-induced prediabetes [high-sucrose (35% Hsu) and high-fat (60% HF)] was developed in adult male Wistar rats through the ingestion of HSu for 9 weeks supplemented by HF for another 14 weeks (HSuHF, n = 16). On W9, half of the former animals orally received BJ (25g/kg BW, HSuHF+BJ). Control animals (n = 8) received standard diet during the entire protocol. Functional [serum and urinary creatinine, uric acid, glucose; glomerular filtration rate (GFR)], structural [H&amp;E and Oil Red O staining] and molecular [triglycerides content and inflammation (RT-qPCR, WB)] markers of renal injury were assessed along with metabolic profile. Results Even though diet-induced glucose intolerance, insulin insensitivity and plasmatic hypertriglyceridemia were significantly ameliorated upon BJ treatment, this nutraceutical intervention was unable to halt or slow down renal lipidosis and glomerular crescent-like lesions apart from a slight amelioration of both GFR and IL-6 levels in HSuHF-treated rats. Conclusion Unlike previous results clearly demonstrating the ability of BJ nutraceutical intervention to afford protection against metabolic impairment and hepatic steatosis evolution in experimentally diet-induced prediabetes, only a modest renoprotective effect was observed in functional and morphological renal endpoints. Future studies are warranted to dissect the divergent effects of BJ on early liver and kidney impairment.

292-OR: Treg Cells Control Systemic Lipid and Iron Metabolism via the OGT-STAT5 Axis

Adipose tissue-resident regulatory T (Treg) cells have been proposed to exert metabolic roles in controlling inflammation, insulin sensitivity and thermogenesis. However, it is still largely unclear how Treg cells integrate immunological and metabolic signals to maintain systemic energy balance. Here we show that the glucose-sensitive O-linked N-Acetylglucosamine (O-GlcNAc) post-translational modification in Treg cells is activated by T cell receptor signaling. Through modifying the STAT5 protein and IL-2 signaling, protein O-GlcNAcylation supports the lineage stability and effector function of Treg cells, while loss of O-GlcNAc transferase (OGT) in Treg cells leads to systemic inflammation in mice. When fed with high fat diet, heterozygous Foxp3-OGT knockout females gain more fat mass as a result of reduced energy expenditure. On the other hand, constitutively active STAT5-mediated Treg-cell expansion and activation protect mice from diet-induced obesity and glucose intolerance. Mechanistically, Treg cells inhibit fatty acid uptake and regulate iron cycling in the adipose tissue. Taken together, we propose that the OGT-STAT5 axis enables Treg cells to maintain systemic lipid and iron homeostasis. Disclosure O.C. Salgado Barrero: None. H. Ruan: None. Funding American Diabetes Association (1-18-IBS-167 to H-B.R.); National Institutes of Health (R01AI139420)

1808-P: Hepatocyte Traf Family Members Link Inflammation to Liver Steatosis and Insulin Resistance

Obesity is associated with chronic inflammation that exacerbates insulin resistance and metabolic disease. Inflammation drives the pathogenesis of nonalcoholic fatty liver disease (NAFLD), hepatic manifestations of obesity. Hepatic inflammatory microenvironments are believed to induce reprogramming of metabolic pathways; however, intracellular molecules coupling inflammation to metabolism remain poorly understood. Cytokines, damage-associated (DAMPs) and pathogen-associated molecular patterns (PAMPs) are known to activate Traf family members that in turn activate the NF-κB and other inflammatory pathways. We previously reported that hepatic Traf2 and Traf3 augment hepatic glucose production. Here, we demonstrate that hepatocyte Traf2, Traf3 and Traf6 act in concert to promote liver steatosis and insulin resistance. We ablated hepatocyte Traf2, Traf3, and Traf6 individually and in combination (Traf2,3,6Δhep) in adult Traf2flox/flox, Traf3flox/flox, Traf6flox/flox, and Traf2,3,6flox/flox mice, respectively, using AAV-TBG-Cre vectors. Metabolic abnormality was more severe in Traf2,3,6Δhep mice relative to Traf2Δhep, Traf3Δhep and Traf6Δhep mice. Remarkably, Traf2,3,6Δhep mice were resistant to high fat diet-induced liver steatosis, insulin resistance, and glucose intolerance. Hepatic PPARα, a master regulator of fatty acid β oxidation, was substantially elevated in Traf2,3,6Δhep mice. Conversely, in primary hepatocytes, overexpression of Traf3 markedly decreased PPARα stability and protein levels. Traf3 coimmunoprecipitated with PPARα and decreased PPARα transcriptional activity. In primary hepatocytes, ablation of Traf2, Traf3 and Traf6 significantly increased fatty acid β oxidation, and overexpression of Traf3 had the opposite effects. Together, our results unveil an unrecognized hepatocyte Traf/PPARα/fatty acid β oxidation pathway that couples inflammation to liver steatosis and insulin resistance in obesity. Disclosure Z. Zhang: None. H. Lin: None. X. Zhong: None. L. Rui: None.

1964-P: Slug Epigenetically Represses Adipose Thermogenic Programs

Thermogenic fat, such as brown adipose tissue (BAT) and beige fat, gains increasing attention due to its ability to protect against obesity and type 2 diabetes. Brown adipocytes and beige adipocytes contain dense mitochondria that burn glucose and free fatty acids to produce heat, and mitochondrial Ucp1 mediates heat production. Coactivator PGC1α is a master regulator of mitochondrial biogenesis and Ucp1 expression, and profoundly influences the energy expenditure capability of thermogenic fat. We attempted to delineate transcriptional regulators that govern thermogenic fat activity through PGC1α, and identified transcriptional repressor Slug. Both human and mouse PGC1α promoters contain multiple Slug binding motifs. Slug potently suppressed the activity of PGC1α promoter luciferase reporters but not mutant PGC1α promoters lacking Slug motifs. Consistently, Slug physically bound to the PGC1α promoter and decreased the levels of PGC1α promoter H3K9 acetylation, a transcriptionally-active epigenetic mark, presumably by recruiting HDAC1/2 to the promoter. In line with this notion, treatment with HDAC1/2 inhibitor trichostatin A abrogated the ability of Slug to suppress PGC1α promoter luciferase reporters. Remarkably, deletion of Slug substantially increased expression of PGC1α and Ucp1 in both BAT and inguinal fat in mice, and increased H3K9 acetylation levels on the PGC1α promoter in BAT. Slug-deficient BAT had increased O2 consumption rates and thermogenesis capability. Slug knockout mice were resistant to high fat diet-induced obesity, insulin resistance, glucose intolerance, and fatty liver disease. Likewise, adipocyte-specific deletion of Slug also ameliorated HFD-induced glucose intolerance. Unlike global Slug knockout mice, adipocyte-specific Slug knockout mice displayed mild metabolic phenotypes. In conclusion, our data suggest that Slug regulates thermogenic fat energy expenditure at least in part by epigenetically suppressing the PGCα-mitochondria axis. Disclosure Q. Kang: None. L. Jiang: None. L. Rui: None.

P0997BLUEBERRY JUICE IMPROVED THE METABOLIC PROFILE IN A PREDIABETIC RAT MODEL INDUCED BY A HYPERCALORIC DIET WITHOUT RENOPROTECTION

Abstract Background and Aims Blueberries (BB), due to their enriched content in polyphenolics and in other compounds with potential cytoprotective properties, have been associated with beneficial effects in distinct cardiometabolic conditions. The goal of this study was to evaluate the metabolic and renal effects of long-term blueberry juice (BJ) treatment in a rat model of prediabetes induced by a hypercaloric diet. Method Prediabetes was developed in adult male Wistar rats through the ingestion of high-sucrose (35% HSu) and high-fat (60% HF) diets during 23 wks (HSuHF animals, n=16). After 9 weeks, half of the former rats received BJ orally (25g/kg BW, HSuHF+BJ group). Control animals (n=8) received standard diet during the entire protocol. Glycemic, lipidic and insulinemic profiles were evaluated throughout the protocol, as well as gut microbiota composition, gut barrier permeability, endotoxemia (LPS) and inflammation (hs-CRP). Renal function was assessed by using serum and urinary measures of creatinine, uric acid and blood urea nitrogen and calculating the glomerular filtration rate (GFR). Histological characterization of the kidney was performed by H&amp;E and lipid deposition by Oil Red O staining and quantification of triglycerides. Serum and renal tissue inflammatory markers were evaluated by Elisa (hs-CRP) and by RT-qPCR and/or WB (IL-6, TNF-α, iNOS, MMP2, TLR-4 and RAGE). The study was approved by the local animal welfare body (Ref: 9-2018). Values are presented as means ± S.E.M. and possible differences evaluated by ANOVA/post-hoc tests. Results While no major changes between groups were found for gut microbiota, gut barrier and endotoxemia/inflammation, BJ treatment was able to ameliorate hypercaloric diet-induced glucose intolerance, insulin insensitivity and plasma hypertriglyceridemia. In addition, in the HSuHF+BJ rats there was a trend to alleviate the reduction of GFR found in the HSuHF animals, as well as some early glomerular lesions, including mesangial expansion and basal membrane thickening. However, this nutraceutical intervention was unable to halt or slow down glomerular crescent-like lesions, renal lipidosis and the overexpression of renal IL-6 found in the HSuHF-treated animals. Conclusion Despite the metabolic improvement viewed by the amelioration of glucose intolerance, insulin insensitivity and hypertriglyceridemia, in this rat model of prediabetes a nutraceutical intervention with BJ presented very modest renoprotective effects. Acknowledgements: FEDER, COMPETE and FCT (CENTRO-01-0145-FEDER-000012-HealthyAging2020, UID/NEU/04539/2013, UID/NEU/04539/2019, POCI-01-0145-FEDER-007440, POCI-01-0145-FEDER-031712, PTDC/SAU-NUT/31712/2017 and SFRH/BD/109017/2015), as well as COAPE and MIRTILUSA.

1812-P: Glucagon Resistance and Decreased Susceptibility to Diabetes in a Model of Chronic Hyperglucagonemia

Elevation of glucagon levels and increase in α-cell mass are associated to states of hyperglycemia in diabetes. However, little is known about the mechanisms that control glucagon secretion and α-cell mass expansion in normal or diabetogenic conditions. The current studies investigated the effects of activation of nutrient signaling by conditional deletion of the mTORC1 inhibitor, TSC2, in α-cells (αTSC2KO), we showed that activation of mTORC1 signaling is sufficient to induce chronic hyperglucagonemia as a result of α-cell proliferation, cell size and mass expansion. Hyperglucagonemia in αTSC2KO was associated to increase in glucagon content, enhanced glucagon secretion and defective adaptation to fasting. This model allowed us to identify the beneficial effects of chronic hyperglucagonemia in glucose homeostasis by inducing insulin secretion and resistance to glucagon in the liver. Liver glucagon resistance in αTSC2KO mice was characterized by reduced expression of the glucagon receptor (GCGR), phosphoenolpyruvate carboxykinase (PEPCK) and genes involved in amino acid metabolism and urea production. Surprisingly, hyperglucagonemia in αTSC2KO mice was associated to improved glucose levels in models of Streptozotocin (STZ)-induced β-cell destruction and high fat diet-induced glucose intolerance. Contrary to our current understanding of glucagon action, these studies demonstrate that endogenous chronic hyperglucagonemia improve glucose homeostasis by augmenting insulin secretion and by inducing glucagon resistance in the liver. These novel in vivo findings support the concept that enhancing glucagon action could be used as an alternative strategy to treat hyperglycemia in diabetes. Disclosure C. Lubaczeuski: None. N. Bozadjieva: None. M. Blandino-Rosano: None. E. Bernal-Mizrachi: None. Funding U.S. Department of Veterans Affairs (IBX002728A); Diabetes Research Connection

IEX-1 deficiency in hematopoietic cells mitigates high fat diet-induced obesity and glucose intolerance

Abstract We previously showed that IEX-1 paucity in mice inhibited high fat diet (HFD)-induced obesity and insulin resistance. IEX-1 deficiency induced browning of white adipose tissue (WAT) by promoting alternative activation of macrophages (AAMs), increasing energy expenditure. We now hypothesize that IEX-1 deficiency in macrophages promotes alternative activation of adipose tissue macrophages (ATM) and induces browning to inhibit obesity. We performed reciprocal bone marrow (BM) transplantation between IEX-1 knockout (KO) and wild-type (WT) mice to generate four types of chimeras. We fed these mice with HFD for 20 weeks and monitored their body weight, glucose disposal, and determined ATM phenotype using flow cytometry. While WT+WT-BM control mice (WT mice received WT bone marrow) gained ~80% body weight on HFD, WT+KO-BM mice (WT mice received KO bone marrow) increased their body weight only by 50% (p&amp;lt;0.01). Conversely, KO+WT-BM mice (KO mice received WT bone marrow) exhibited increased weight gain on HFD as compared to KO+KO-BM control mice that remained lean (p&amp;lt;0.05). Likewise, WT+KO-BM mice displayed greater glucose disposal as compared to WT control, and KO+WT-BM mice became glucose intolerant as compared to KO control as determined by glucose tolerance test. Analysis of ATM phenotype in mice fed with HFD for 5 weeks showed that HFD increased the percentage of classically activated macrophages (CAMs) by 3–4-folds (p&amp;lt;0.01), and decreased AAMs by ~30% (P&amp;lt;0.05) in epidydmal and inguinal WAT of WT+WT-BM mice. However, these effects were markedly suppressed in WT+KO-BM mice. Collectively, these data suggest that IEX-1 in hematopoietic cells contributes to HFD-induced obesity and glucose intolerance via inhibiting AAMs polarization.

Effect of stevia on the gut microbiota and glucose tolerance in a murine model of diet-induced obesity.

Artificial sweeteners have been shown to induce glucose intolerance by altering the gut microbiota; however, little is known about the effect of stevia. Here, we investigate whether stevia supplementation induces glucose intolerance by altering the gut microbiota in mice, hypothesizing that stevia would correct high fat diet-induced glucose intolerance and alter the gut microbiota. Mice were split into four treatment groups: low fat, high fat, high fat + saccharin and high fat + stevia. After 10 weeks of treatment, mice consuming a high fat diet (60%kcal from fat) developed glucose intolerance and gained more weight than mice consuming a low fat diet. Stevia supplementation did not impact body weight or glucose intolerance. Differences in species richness and relative abundances of several phyla were observed in low fat groups compared to high fat, stevia and saccharin. We identified two operational taxonomic groups that contributed to differences in beta-diversity between the stevia and saccharin groups: Lactococcus and Akkermansia in females and Lactococcus in males. Our results demonstrate that stevia does not rescue high fat diet-induced changes in glucose tolerance or the microbiota, and that stevia results in similar alterations to the gut microbiota as saccharin when administered in concordance with a high fat diet.

Loss of β‐cell Gαz protects against high‐fat diet induced glucose intolerance by preserving incretin responsiveness and enhancing insulin secretion

Cyclic‐adenosine monophosphate (cAMP) is an important secondary messenger in the insulin‐secreting pancreatic β‐cells. Intracellular production of cAMP is augmented by stimulatory heterotrimeric G proteins (Gs) and blocked by inhibitory heterotrimeric G proteins (Gi). Pancreatic expression of the unique Gi family member, Gαz, is restricted to the islet, which contains β‐cells and other endocrine cell types, including glucagon/GLP‐1‐secreting alpha cells and somatostatin‐secreting delta cells. We have previously shown that full body Gαz‐null mice are protected from hyperglycemia in several diabetes model systems. Here, we use a high fat diet (HFD) model of obesity and insulin resistance to explore the impact of loss of beta‐cell Gαz on the type 2 diabetes (T2D) phenotype of male C57BL/6J mice. We hypothesized that loss of beta‐cell Gαz in the context of HFD feeding would enhance insulin secretion, protecting mice from HFD‐induced glucose intolerance. To generate beta‐cell specific Gαz‐null and control mice, we bred Gαz flox/flox mice with rat insulin promoter RIP‐Creherr mice. At 12 weeks of age, transgenic Gαz‐null mice were fed a diet containing 45 kcal% fat or a 10 kcal% fat control diet for 26 weeks. At study end, mice were metabolically phenotyped and sacrificed for whole pancreas and islet phenotyping. Beta‐cell‐specific Gαz loss protected mice from HFD induced glucose intolerance due to a selective effect on islet insulin secretion, particularly in concert with a stable agonist of the Gs‐coupled GLP‐1 receptor. This protective effect was independent of changes in Gαz‐coupled EP3 receptor signaling, as neither EP3 expression nor production of its endogenous ligand, PGE2, were enhanced in islets from HFD‐fed mice. This protective effect was also beta‐cell autonomous, as both full‐body and beta‐cell‐specific Gαz‐null mice had enhanced GLP‐1‐positive alpha‐cells, albeit with no changes in active GLP‐1 secretion. Finally, gene microarray results confirm that Gαz loss and HFD feeding synergize to differentially regulate islet gene expression, specifically up‐regulating secretion‐centric genes, many of which are related to cAMP signaling. This study presents a novel inhibitory mechanism of receptor‐independent G‐protein signaling that may hold promise for developing beta‐cell targeted diabetes therapeutics.

Bofutsushosan improves gut barrier function with a bloom of Akkermansia muciniphila and improves glucose metabolism in mice with diet-induced obesity

Obesity and insulin resistance are associated with dysbiosis of the gut microbiota and impaired intestinal barrier function. Herein, we report that Bofutsushosan (BFT), a Japanese herbal medicine, Kampo, which has been clinically used for constipation in Asian countries, ameliorates glucose metabolism in mice with diet–induced obesity. A 16S rRNA sequence analysis of fecal samples showed that BFT dramatically increased the relative abundance of Verrucomicrobia, which was mainly associated with a bloom of Akkermansia muciniphila (AKK). BFT decreased the gut permeability as assessed by FITC-dextran gavage assay, associated with increased expression of tight-junction related protein, claudin-1, in the colon. The BFT treatment group also showed significant decreases of the plasma endotoxin level and expression of the hepatic lipopolysaccharide-binding protein. Antibiotic treatment abrogated the metabolic effects of BFT. Moreover, many of these changes could be reproduced when the cecal contents of BFT-treated donors were transferred to antibiotic-pretreated high fat diet-fed mice. These data demonstrate that BFT modifies the gut microbiota with an increase in AKK, which may contribute to improving gut barrier function and preventing metabolic endotoxemia, leading to attenuation of diet-induced inflammation and glucose intolerance. Understanding the interaction between a medicine and the gut microbiota may provide insights into new pharmacological targets to improve glucose metabolism.