Induced Glucose Intolerance Research Articles

Maternal Supplementation with β-Carotene During Pregnancy Disturbs Lipid Metabolism and Glucose Homoeostasis in F1 Female Mice.

β-Carotene (BC), a substitute for vitamin A, is widely used for its benefits. The present study investigates whether in-utero BC administration can alter lipid and glucose homoeostasis in offspring. Pregnant mice are supplemented with BC (1 mg kg-1 weight) by oral gavage once every 3 days, for a total of six doses. Increased visceral fat may be caused by up-regulated PPARγ (peroxisome proliferator-activated receptor gamma) and RXRα/β (retinoid X receptors) in liver and adipose tissue, and glucose intolerance is observed in F1 adult females prenatally supplemented with BC, while F1 males do not exhibit these symptoms. In females, increased serum leptin, resistin, and IL-6 and reduced adiponectin, caused by visceral obesity, may result in downregulated insulin receptor signaling in muscle and further account for glucose intolerance. Increased pancreatic β-cell mass might compensate for the downregulated insulin gene (ins2). Increased glucagon and α-cell mass, accompanied by upregulated glucagon gene (gcg), might also be risk factors for the development of diabetes. Maternal supplementation with BC disturbs lipid metabolism and induces glucose intolerance in F1 female mice, suggesting that BC supplementation during pregnancy should be used with caution.

Abstract WP153: Prenatal Alcohol Exposure Induces Glucose Intolerance and Exacerbates Stroke Severity in Middle-Aged Rats

Background and Purpose: Metabolic disorders and cardiovascular diseases in post-natal life have been linked to adverse prenatal environment. There is very little information on the developmental origin of adult diseases, particularly fetal alcohol exposure and stroke outcomes. The present study tested the hypothesis that fetal alcohol exposure induces glucose intolerance and leads to greater stroke severity in middle-aged rats. Methods: Timed-pregnant Sprague Dawley rats (GD12) purchased from Envigo laboratories were intragastrically gavaged with ethanol (3g/kg/bwt) or water twice per day from GD12 through 15. Fetal alcohol exposed (FAE) progeny (10 mo. old) were injected with glucose (1g/kg.bwt) and tested for glucose intolerance (glucose clearance rate at 15, 30 and 60 min.) Animals were subjected to endothelin-1 induced MCAo and outcomes evaluated after 2 and 5 days. Stroke induced disabilities were assessed from behavioral assays (adhesive removal, Vibrissae evoked fore-limb placement and circling) and infarct volume. Results: Glucose tolerance test showed elevated blood glucose levels in both control and FAE group at 15 and 30 min but FAE animals exhibited prolonged elevation of blood glucose (60 min., p< 0.017) compared to control animals. At 2 day post-stroke, FAE animals exhibited greater neurological deficit as determined by their higher score on circling behavior (lack of muscle control, p<0.031) compared to controls. No mortality was seen in the control group while MCAo resulted in 25% mortality in the FAE group. Among the survivors, brain damage assessed by infarct volume at post-stroke 5 day was not significantly different between the two groups. Conclusions: The present findings support the hypothesis that prenatal exposure to alcohol contributes to long-lasting adverse effects on adult health as indicated by poor glucose tolerance and worse neurological outcomes during the acute stage of stroke.

High-glucose administration induces glucose intolerance in mice: a critical role of toll-like receptor 4.

Glucose converted from a diet has been considered a high-risk factor of type 2 diabetes mellitus (T2DM). However, it is not clear how it increases the risk of T2DM. Here, we investigated the effect of high-glucose administration on glucose tolerence in wild-type and toll-like receptor 4 (TLR4) knockout mice. Mice were intragastrically administered with high-glucose. The level of fasting blood glucose, insulin and intraperitoneal glucose tolerance were measured, and insulinogenic index and HOMA-IR were calculated at 1 week. To understand mechanism of glucose action, we also assessed blood glucose, glucagon-like peptide-1 and inflammatory cytokines levels at different time windows following high-glucose load. Our results show that 20 g/kg glucose load leads to glucose tolerance impairment and insulin resistance in wild-type mice. Following 20 g/kg glucose load, the levels of plasma interlukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) increased significantly in wild-type mice, but not in TLR4 knockout mice. Moreover, 20 g/kg glucose load also impaired glucose-induced GLP-1 secretion in wild-type and TLR4 knockout mice. Our results indicate that high-glucose load leads to glucose intolerance with insulin resistance through impairment of GLP-1 secretion, increase of blood glucose levels via activating TLR4 and increasing levels of IL-6 and TNF-α in mice.

Obesity-associated exosomal miRNAs modulate glucose and lipid metabolism in mice

Obesity is frequently associated with metabolic disease. Here, we show that obesity changes the miRNA profile of plasma exosomes in mice, including increases in miR-122, miR-192, miR-27a-3p, and miR-27b-3p Importantly, treatment of lean mice with exosomes isolated from obese mice induces glucose intolerance and insulin resistance. Moreover, administration of control exosomes transfected with obesity-associated miRNA mimics strongly induces glucose intolerance in lean mice and results in central obesity and hepatic steatosis. Expression of the candidate target gene Ppara is decreased in white adipose tissue but not in the liver of mimic-treated (MIMIC) mice, and this is accompanied by increased circulating free fatty acids and hypertriglyceridemia. Treatment with a specific siRNA targeting Ppara transfected into exosomes recapitulates the phenotype induced by obesity-associated miRNAs. Importantly, simultaneously reducing free fatty acid plasma levels in MIMIC mice with either the lipolysis inhibitor acipimox or the PPARα agonist fenofibrate partially protects against these metabolic alterations. Overall, our data highlight the central role of obesity-associated exosomal miRNAs in the etiopathogeny of glucose intolerance and dyslipidemia.

Knockout of TRPV1 Exacerbates Left Ventricular Diastolic Dysfunction Induced by A High-fat Diet in Mice.

Transient Receptor Potential Vanilloid 1 (TRPV1) channels in sensory nerves have anti-oxidative properties and counteract obesity and diabetes that are associated with diastolic dysfunction with preserved ejection fraction. We tested the hypothesis that TRPV1 knockout exacerbates high-fat diet (HFD)-induced glucose intolerance and diastolic dysfunction. Trpv1-/- and wild-type (WT) mice were fed chow diet or HFD for 20 weeks. Then, we performed the intraperitoneal glucose tolerance test, measured the heart function through transthoracic echocardiography and Langendorff heart perfusion system, analyzed cardiac histology, and measured the myocardial superoxide production and the expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases. HFD increased body weight, heart weight, and levels of fasting glucose, insulin, and leptin in both strains, with no differences between two strains. HFD impaired glucose tolerance in both strains with a more profound effect on Trpv1-/- than WT mice. HFD increased left ventricular (LV) internal diameter in diastole in both strains, while increased LV posterior wall thickness in diastole in Trpv1-/- but not in WT mice. HFD increased LV end-diastolic pressure in both strains with a further increase in Trpv1-/- mice, while decreased -dP/dt in Trpv1-/- but not in WT mice. HFDinduced cardiac collagen deposition and superoxide production were enhanced in Trpv1-/- mice. HFD upregulated cardiac p22phox in both strains, while increased p47phox in Trpv1-/- but not in WT mice. In summary, TRPV1 knockout exacerbates HFD-induced glucose intolerance, cardiac oxidative stress and collagen deposition, leading to aggravated LV diastolic dysfunction.

TDP-43 Regulates Early-Phase Insulin Secretion Via Cav1.2-Mediated Exocytosis in Pancreatic Islets

Nuclear depletion of TAR DNA-binding protein 43 kDa (TDP-43), encoded by TARDBP, is the histopathological hallmark of amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disorder affecting motor neurons. Besides motor symptoms, ALS patients often develop non-neuronal signs including glucose intolerance, but the underlying pathomechanism is still controversial, i.e., impaired insulin and/or insulin resistance. Here, we show that ALS subjects have reduced early-phase insulin secretion and loss of TDP-43 in the nuclei of pancreatic islets. Loss of TDP-43 inhibited exocytosis by down-regulating Cav1.2 calcium channels, thereby reducing early-phase insulin secretion in a cultured β cell line (MIN6). Furthermore, β cell-specific TDP-43 knock-out induced glucose intolerance via suppression of early-phase insulin secretion in mice. These results suggest that TDP-43 regulates cellular exocytosis mediated by L-type voltage dependent calcium channels and thus plays an important role in the early-phase of insulin secretion by pancreatic islets. Funding: This work was supported by Grants-in-Aid (KAKENHI) from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan: Nos. 16K09742, 16K15480, 17H04195, and 17K08547 (M.K.); and 16K09392 and 16K09393 (H.I.). This work was partly supported by grants from the Japan Agency of Medical Research and Development (AMED): JP17dm0107105h0002 and JP16kk0205009h0001 (M.Y.). This work was also supported by Grants-in-Aid from the Research Committee of CNS Degenerative Diseases, Research on Policy Planning and Evaluation for Rare and Intractable Diseases, Health, Labor and Welfare Sciences Research Grants, the Ministry of Health, Labor and Welfare, Japan (M.Y.), a grant from the Naito Foundation (M.K.), and a grant from Hori Sciences & Arts Foundation (M.K.). Declaration of Interest: S.M. owns equity in a gene therapy company (Gene Therapy Research Institution) that commercializes the use of AAV vectors for gene therapy applications. To the extent that the work in this manuscript increases the value of these commercial holdings, S.M. has a conflict of interest. Ethical Approval: This study adhered to the Ethics Guidelines for Human Genome/gene Analysis Research and those for Medical and Health Research Involving Human Subjects endorsed by the Japanese government, and approved by the Ethics Committees of Nagoya University Graduate School of Medicine. All participants provided their written informed consent. Experimental procedures involving human subjects were conducted in conformance with the principles expressed in the Declaration of Helsinki.

Substitution of linoleic acid with \u03b1-linolenic acid or long chain n-3 polyunsaturated fatty acid prevents Western diet induced nonalcoholic steatohepatitis

Imbalance in the n-6 polyunsaturated fatty acids (PUFA) and n-3 PUFA in the Western diet may increase the risk of nonalcoholic fatty liver disease (NAFLD). This study investigates the impact of substitution of linoleic acid with α-linolenic acid (ALA) or long chain (LC) n-3 PUFA and hence decreasing n-6:n-3 fatty acid ratio on high fat, high fructose (HFHF) diet induced nonalcoholic steatohepatitis (NASH). Male Sprague-Dawley rats were divided into four groups and fed control diet, HFHF diet (n-6:n-3 ratio of 200), HFHF diet with ALA (n-6:n-3 ratio of 2) or HFHF diet with LC n-3 PUFA (n-6:n-3 ratio of 5) for 24 weeks. Rats fed HFHF diet with n-6:n-3 ratio of 200 resulted in hepatic steatosis, induced glucose intolerance, insulin resistance and oxidative stress accompanied by increase in markers of inflammation, plasma lipids and aminotransferase levels. Histopathological examination of liver further confirmed the establishment of NASH. ALA and LC n-3 PUFA supplementation prevented hepatic steatosis and dyslipidemia by inhibiting lipogenesis and increasing insulin sensitivity. Furthermore, n-3 PUFA supplementation attenuated hepatic oxidative stress by restoring antioxidant status, decreased inflammation and preserved hepatic architecture. These finding suggest that decreasing n-6:n-3 ratio prevented HFHF induced NASH by attenuating oxidative stress and inflammation.

Mechanisms of sleep deprivation-induced hepatic steatosis and insulin resistance in mice.

Sleep deprivation is associated with increased risk for type 2 diabetes mellitus. However, the underlying mechanisms of sleep deprivation-induced glucose intolerance remain elusive. The aim of this study was to investigate the mechanisms of sleep deprivation-induced glucose intolerance in mice with a special focus on the liver. We established a mouse model of sleep deprivation-induced glucose intolerance using C57BL/6J male mice. A single 6-h sleep deprivation by the gentle handling method under fasting condition induced glucose intolerance. Hepatic glucose production assessed by a pyruvate challenge test was significantly increased, as was hepatic triglyceride content (by 67.9%) in the sleep deprivation group, compared with freely sleeping control mice. Metabolome and microarray analyses were used to evaluate hepatic metabolites and gene expression levels and to determine the molecular mechanisms of sleep deprivation-induced hepatic steatosis. Hepatic metabolites, such as acetyl coenzyme A, 3β-hydroxybutyric acid, and certain acylcarnitines, were significantly increased in the sleep deprivation group, suggesting increased lipid oxidation in the liver. In contrast, fasted sleep-deprived mice showed that hepatic gene expression levels of elongation of very long chain fatty acids-like 3, lipin 1, perilipin 4, perilipin 5, and acyl-CoA thioesterase 1, which are known to play lipogenic roles, were 2.7, 4.5, 3.7, 2.9, and 2.8 times, respectively, those of the fasted sleeping control group, as assessed by quantitative RT-PCR. Sleep deprivation-induced hepatic steatosis and hepatic insulin resistance seem to be mediated through upregulation of hepatic lipogenic enzymes.

Dietary Supplementation with Galactooligosaccharide (GOS) Attenuates High-Fat, High-Cholesterol Containing Western Diet (WD)–Induced Glucose Intolerance

WD induces the development of type 2 diabetes (T2DM). In addition to the direct effects on gut dysbiosis, we have shown that WD also affect intestinal barrier function leading to increased release of LPS into circulation resulting in chronic inflammation that underlies the development of T2DM; oral supplementation with curcumin attenuate these WD-induced effects. Herein we examined the effects of GOS supplementation on WD induced changes. C57BL/6 mice were either fed a standard chow or WD or WD+GOS or WD+Curcumin (WD+C) for 16 weeks. Glucose tolerance tests were performed and while no significant differences were seen in female mice (Panels A and C), WD-induced glucose intolerance was significantly attenuated by GOS or curcumin supplementation in male mice (Panels B and D). Although plasma LPS levels were not significantly affected, a significant decrease in circulating macrophages (Panel E) as well as neutrophils (Panel F) was noted with GOS or Curcumin supplementation indicating a reduction in systemic inflammation. Gene expression and histological changes in the ileum and colon indicate GOS or curcumin-mediated increase in mucin production and maintenance of mucous layer integrity. Dietary supplementation with GOS or Curcumin, therefore, represents a simple strategy to ameliorate the metabolic/diabetogenic effects of WD. Disclosure H. He: None. S.S. Ghosh: None. P.J. Yannie: None. J. Wang: None. S. Ghosh: None.

Mechanisms of Hepatic Steatosis and Insulin Resistance Induced by Sleep Deprivation in Mice

Sleep is an important life style component and its deprivation is a risk for type 2 diabetes. However, the underlying mechanisms and the therapeutic target of sleep deprivation induced glucose intolerance are unclear. The aim of this study was to investigate the mechanisms of sleep deprivation induced glucose intolerance focusing on liver. We established a mouse model of sleep deprivation induced glucose intolerance using C57BL/6J male mice. Single 6 hours sleep deprivation by gentle handling method in fasted condition induced glucose intolerance. Interestingly, hepatic glucose production assessed by pyruvate challenge test was significantly increased, and hepatic triglyceride content was also increased in 67% in the sleep deprivation mice compared to freely sleeping control mice. To explore the molecular mechanisms of sleep deprivation induced hepatic steatosis, hepatic metabolites and gene expressions were comprehensively evaluated using metabolome and microarray analyses. Hepatic metabolites such as acetyl CoA, 3β-hydroxybutyric acid, and some acylcarnitines were significantly increased in sleep deprivation group, suggesting increased lipid oxidation in the liver. In contrast, hepatic gene expressions of Elovl3, Lpin1, Plin4, Plin5 and Acot1 that play a lipogenic role were significantly increased 2.7, 4.5, 3.7, 2.9, and 2.8 times respectively in sleep deprivation group compared to control group, confirmed by quantitative RT-PCR. The increased lipogenic gene expressions may partly explain the sleep deprivation induced hepatic steatosis. Conclusion: Single 6 hours sleep deprivation caused hepatic steatosis and hepatic insulin resistance in fasted C57BL/6J mice. Increased hepatic lipogenic enzymes raised above may be potential therapeutic targets for the sleep deprivation induced hepatic steatosis and hepatic insulin resistance. Disclosure F. Shigiyama: None. N. Kumashiro: Speaker's Bureau; Self; Novo Nordisk Inc.. F. Yoshikawa: None. Y. Tsuneoka: None. H. Funato: None. T. Hirose: Research Support; Self; AstraZeneca. Speaker's Bureau; Self; AstraZeneca. Research Support; Self; Bayer Yakuhin, Ltd., Novartis Pharma K.K.. Speaker's Bureau; Self; Novartis Pharma K.K.. Research Support; Self; Takeda Development Center Asia, Pte. Ltd.. Speaker's Bureau; Self; Takeda Development Center Asia, Pte. Ltd.. Research Support; Self; Ono Pharmaceutical Co., Ltd., Eli Lilly and Company. Speaker's Bureau; Self; Eli Lilly and Company. Research Support; Self; MSD K.K.. Speaker's Bureau; Self; MSD K.K.. Research Support; Self; Sanofi K.K.. Speaker's Bureau; Self; Sanofi K.K.. Research Support; Self; Mitsubishi Tanabe Pharma Corporation. Speaker's Bureau; Self; Mitsubishi Tanabe Pharma Corporation. Research Support; Self; Daiichi Sankyo Company, Limited. Speaker's Bureau; Self; Daiichi Sankyo Company, Limited. Research Support; Self; Sumitomo Dainippon Pharma Co., Ltd.. Speaker's Bureau; Self; Sumitomo Dainippon Pharma Co., Ltd.. Research Support; Self; Novo Nordisk Inc.. Speaker's Bureau; Self; Novo Nordisk Inc.. Research Support; Self; Boehringer Ingelheim Pharmaceuticals, Inc.. Speaker's Bureau; Self; Boehringer Ingelheim Pharmaceuticals, Inc..

Hyperproinsulinemia in OGlcNAc Transferase Deficient Mice Is Associated with Loss of CPE and eIF4G1, but ß-Cell Deletion of eIF4G1 Induces Glucose Intolerance Independent of CPE Dysregulation

β cell loss of OGlcNAc transferase (βOGTKO), the sole enzyme that adds OGlcNAc post-translational modification onto target proteins impacting their function and stability, leads to diabetes and islet failure in mice. βOGTKO mice present hyperproinsulinemia, typified by increased serum proinsulin/insulin ratio. Here, we show that βOGTKO islets have reduced carboxypeptidase E protein but not mRNA (CPE, an exopeptidase that converts proinsulin to insulin), independent of sex, age and glucose levels. We identified that CPE is neither the target nor a binding partner of OGT. Eukaryotic initiation factor 4 gamma 1 (eIF4G1), previously shown to regulate CPE in vitro, is reduced at the protein level, but not mRNA, in βOGTKO islets. We identified that eIF4G1 is OGlcNAc-modified in β cells and mutation of the putative OGlcNAc site at serine 61 to alanine led to decreased protein stability, but not on CPE translation. To assess the role of eIF4G1 on CPE regulation in vivo, we generated mice with β cell specific deletion of eIF4G1 (RIPCre; eIF4G1flox/flox (βeIF4G1KO)), in R1207H eIF4G1 (eIF4G1) background. At 6 weeks of age in normal chow diet, glucose intolerance was evident between βeIF4G1KO and littermate control eIF4G1 mice, without alteration in peripheral insulin sensitivity. Surprisingly, no apparent insulin processing deficit was observed between βeIF4G1KO and eIF4G1 mice, consistent with the observed normal level of CPE protein among islets of βeIF4G1 KO, eIF4G1 or wild type mice via immunofluorescence, and comparable serum proinsulin/insulin ratio in βeIF4G1 KO and eIF4G1 mice. Significant reduction in the average β cell size and increased number of α cells was evident in βeIF4G1KO vs. eIF4G1 mice, hinting at loss in β cell mass. Together, these data unveil the regulation of OGT on eIF4G1, and underscore the novel role of eIF4G1 on glucose homeostasis and modulation of β cell size. Disclosure S. Jo: None. A.D. Lockridge: None. E. Alejandro: None.

New Prebiotics to Ameliorate High-Fat Diet-Induced Obesity and Diabetes via Modulation of Microbiome-Gut-Brain Axis

Role of gut microbiome in obesity and diabetes became apparent from several independent studies, indicating that gut microbiome modulators like prebiotics may improve microbiome perturbations (dysbiosis) to ameliorate metabolic derangements. We isolated water soluble, non-digestible polysaccharides from 5 foods (acorn, quinoa, sunflower, pumpkin and sago seeds) and assessed their impact on amelioration of high fat diet (HFD)-induced obesity and diabetes in mice and human microbiome using fecal slurry culture model. During isolation, purification, biochemical and digestion resistance characterization, and fermentation pattern by human fecal microbiome, we selected acorn and sago derived prebiotics, on the basis of purity, protein contamination and yield. All prebiotics increased short chain fatty acid (SCFA) production along with enhanced microbial diversity. Feeding of acorn and sago derived prebiotics supplemented HFD (5%) for 8 weeks, significantly reduced diet induced glucose intolerance and insulin resistance, without affecting adiposity. Beneficial effects of acorn and sago derived prebiotics were superior than inulin-feeding. Feeding of both prebiotics and inulin increased diversity of gut microbiome and enhanced SCFA production into the mice gut. Metabolic function was positively correlated with increased food conversion ratio indicating enhanced whole body metabolic rate by prebiotic feeding. Gastrointestinal motility was enhanced without changing food intake, after probiotic intervention. Hypothalamic energy signaling in terms of increased pro-opiomelanocortin and decreased agouti-related peptide and neuropeptide Y expression, was modulated by prebiotics administration. These results indicate that newly isolated prebiotics ameliorate HFD-induced defects of glucose metabolism via modulating microbiome-gut-brain axis, and can be used to prevent/treat diet induced obesity and diabetes. Disclosure S. Ahmadi: None. R.K. Nagpal: None. S. Wang: None. H. Yadav: None.

Deletion of SLC4A4 in Pancreatic ß Cells Protects from High-Fat Diet–Induced Glucose Intolerance and ß-Cell Dysfunction

Islet failure in type 2 diabetes (T2DM) is characterised by loss of glucose-stimulated insulin secretion (GSIS) attributed in part to β-cell dedifferentiation (e.g., mis-expression of alpha cell-specific genes). Recent single cell transcriptomics studies identified SLC4A4 (a gene encoding an electrogenic Na+-nHCO3- cotransporter, NBCe1) as one of the mis-expressed genes in β-cells of patients with T2DM. Thus, we set out to test the hypothesis that mis-expression of SLC4A4 in β-cells contributes to loss of GSIS and impaired glucose homeostasis in T2DM. To address this hypothesis, we first confirmed induction of robust SLC4A4 protein expression in β-cells of patients with T2DM utilizing immunofluorescence staining of autopsy-derived human pancreas specimens. We next generated β-cell-specific slc4a4 knockout (β-slc4a4-/-) and corresponding control (β-slc4a4+/+) mice through crossing of slc4a4 loxP/loxP and Ins2-Cre mouse models. Adult (3 month old) β-slc4a4-/- mice displayed normal body weight, glycaemia, glucose tolerance and insulin sensitivity under standard chow fed conditions (p>0.vs. β-slc4a4+/+). In contrast, β-slc4a4-/- mice exhibited enhanced glucose tolerance and in vivo glucose-stimulated insulin response under conditions of metabolic stress induced by ad libitum intake of 60% high fat diet (HFD) for 8 weeks (p<0.vs. β-slc4a4+/+ HFD). Interestingly, improved glucose tolerance in β-slc4a4-/-mice was also associated with a tendency for expansion of β-cells mass (82%, p=0.09 vs. β-slc4a4+/+ HFD) and increased β-cells proliferation (26%, p=0.11 vs. β-slc4a4+/+ HFD). These results suggest that β-cell mis-expression of the Na+-nHCO3- cotransporter encoded by SLC4A4 contributes to induction of β-cell failure under conditions of metabolic stress and T2DM. Disclosure M. Brown: None. H.L. Holmes: None. K. Rakshit: None. M.F. Romero: None. A. Matveyenko: None.

Effects of sucralose on insulin and glucagon-like peptide-1 secretion in healthy subjects: a randomized, double-blind, placebo-controlled trial.

Emerging evidence shows that non-nutritive sweeteners might induce glucose intolerance. This study aims to determine the effects of chronic exposure to sucralose on glycemic response, insulin secretion and sensitivity, and glucagon-like peptide-1 (GLP-1) release in healthy subjects. Healthy volunteers who did not use non-nutritive sweeteners and were normoglycemia after oral glucose tolerance test (OGTT) were recruited. Subjects underwent a 75-g OGTT on two separate occasions, preceded by blindly consuming pills containing either 200 mg sucralose or placebo for 4 wk in a randomized crossover trial. Plasma glucose, insulin, and active GLP-1 levels were obtained after ingesting 75-g glucose. On the following day, intravenous glucose tolerance test (IVGTT) was performed to evaluate the acute insulin response (AIR). Fifteen participants (11 females, age 31.9 ± 10 y, body mass index 23.1 ± 3 kg/m2) participated in the study. AIR was lower after exposure to sucralose than placebo (58.9 ± 48.61 versus 69.94 ± 73.81 µU/mL, P < 0.001). Whole-body insulin sensitivity (estimated using the Matsuda index) was lower in sucralose than placebo (4.69 ± 1.67 versus 5.31 ± 2.56, P < 0.005). AUC of active GLP-1 was significantly higher in the sucralose than placebo (23.16 ± 18.86 versus 18.5 ± 22.22 pmol/L ⋅ 120 min, P < 0.001). The continuous exposure to sucralose reduced AIR, decreased insulin sensitivity, and enhanced GLP-1 release in healthy subjects. However, the clinical significance of these results needs to be investigated in longer follow-up studies.

Novel role of GLP-1 receptor signaling in energy expenditure during chronic high fat diet feeding in rats

ObjectiveGlucagon-like peptide-1 (GLP-1) secreted from intestinal L-cells plays a major role in meal termination and glucose-dependent insulin secretion. Several lines of evidence indicate, however, that the acute satiating and incretin effects of GLP-1 are attenuated with high fat diet (HFD) exposure. Here we tested the hypothesis that endogenous GLP-1 differentially affects energy balance and glucose homeostasis dependent on whether rats are fed chow or HFD (60% energy from fat). MethodsWe blocked GLP-1 receptor (GLP-1R) signaling by daily intraperitoneal (IP) injection of the GLP-1R antagonist exendin (9–39) (Ex9, 10 μg/kg) or vehicle for 5 weeks in male Sprague-Dawley rats fed either chow or HFD, recorded body weight (BW) and food intake throughout, and assessed energy expenditure (3rd week) and glucose tolerance (4th week). ResultsFive week daily Ex9 injections reduced BW gain in HFD-fed rats, but did not affect BW in chow-fed rats. On the other hand, chronic Ex9 treatment did not affect daily food intake in either chow or HFD-fed rats during the entire study. The reduced BW gain in HFD-fed rats was associated with an increase in energy expenditure. Interestingly, chronic Ex9 treatment induced glucose intolerance in chow-fed rats, but not in HFD-fed rats, suggesting a differential role of GLP-1R signaling in glucose metabolism during chow and HFD feeding. ConclusionsOur findings reveal a novel role of GLP-1R signaling, modulating energy expenditure rather than eating behavior during HFD feeding. Furthermore, these results suggest a previously unrecognized contribution of GLP-1R signaling to the pathophysiology of obesity.

The role of ACE2/Ang 1–7/Mas axis in the white adipose tissue for the prevention of obesity and insulin resistance through aerobic exercise training

The activation of angiotensin converting enzyme 2 (ACE2)/angiotensin 1–7 (Ang 1–7)/receptor Mas axis has been associated with cardiovascular and metabolic improvement, and may represent a new therapeutic target for cardiometabolic diseases. Aerobic exercise training (AET) has been widely used for the prevention and treatment of obesity and insulin resistance (IR). In the present study we evaluated if the prevention of obesity and IR through AET is associated with changes in the ACE2/Ang (1–7)/Mas axis in the white adipose tissue (WAT). Adult male C57BL6/J mice were assigned into chow‐fed controls (C, n=5), chow‐fed trained (T, n=5), cafeteria diet (CAF, n=5), and cafeteria diet plus trained (CAFT, n=5). AET was performed simultaneously with diet and consisted of 8‐wk running session of 60 min at 60% of maximal speed, 5 days/wk. Experimental procedures were approved by Ethics Committee from Faculty of Medicine of University of São Paulo (#002/15). The body weight of the T and CAFT groups were lower from the third week of experimental protocol compared to C. The CAF group had higher retroperitoneal and subcutaneous (SC) fat pads weights compared to C, but the AET was able to prevent these increases in the CAFT group. Periepididimal (PE) fat pad weight was lower in T group compared to other groups. Cafeteria diet induced glucose intolerance and IR in CAF group (AUC: 35200± 1076 mg/dL/120 min; kITT: 2.5 ± 0.17 %/min) compared to the C group (AUC: 28333±1305 mg/dL/120 min; kITT: 3.7 ± 0.21 %/min), which were counteracted by AET in CAFT group (AUC: 28896 ± 1133 mg/dL/120 min; kITT: 3.9 ± 0.33 %/min). In the PE‐WAT, the activity of ACE2 was higher in CAF and CAFT groups compared to C and T groups, but Ang 1–7 concentration and Mas protein expression were not different among groups. In the SC‐WAT, no differences were found in ACE2 activity and Mas protein expression, but the Ang 1–7 concentration was lower in CAF and CAFT compared to C and T groups. In conclusion, the prevention of obesity and IR by AET was independent of the ACE2/Ang 1–7/Mas axis activation in the visceral and subcutaneous WAT.Support or Funding InformationSupport: FAPESP #2015/04948‐4; #2016/23783‐9.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The prevention of cardiometabolic risk factors is associated with the improvement in aerobic capacity

Physical inactivity reduces aerobic capacity and is directly associated with an increase in cardiometabolic risk factors. Here we investigated whether there is an association between increased aerobic capacity and the prevention of obesity and insulin resistance through aerobic exercise training (AET). Adult male C57BL6/J mice were assigned into chow‐fed controls (C, n=10), cafeteria diet (CAF, n=8), chow‐fed trained (T, n=9), and cafeteria diet plus trained (CAFT, n=8) groups. AET was performed simultaneously with diet and consisted of 8‐wk running session of 60 min at 60% of maximal speed, 5 days/wk. Experimental procedures were approved by Ethics Committee from School of Arts, Science and Humanities, University of Sao Paulo, Brazil (#001/2016). Both trained groups showed lower body weight at the end of protocol compared to C and CAF groups. However, only CAFT group had reduced body weight gain compared to the CAF group. Cafeteria diet induced glucose intolerance and insulin resistance in the CAF group, which was counteracted by AET in CAFT group. Indirect calorimetry measurement at rest revealed no difference in the variables oxygen uptake (VO2), carbon dioxide expiration (VCO2), respiratory exchange ratio (RER), energy expenditure (EE), carbohydrate and fat oxidation among groups. During maximal exercise tests, T and CAFT groups showed an increase in VO2máx (13% and 9.2%, p=0.07) and VO2peak (11.3% and 8.6%, p=0.07) compared to C and CAF, respectively. However no differences among groups were found for RER and rate of substrate oxidation. AET increased the time to exhaustion and maximal velocity in the T compared to C and CAF groups, and in the CAFT compared to CAF. The exercise intensity corresponding to the VO2máx (iVO2) was higher in the T group (2.30 ± 0.42 km⁄h) compared to C (1.86 ± 0.41 km/h) and CAF (1.73 ± 0.17 km/h) groups, and in the CAFT (2.23 ± 0.11 km/h) compared to CAF. Both trained groups showed late anaerobic threshold, improved the relative cost of running, and higher activity of citrate synthase and β‐HAD enzymes in the soleus muscle compared to C and CAF groups. In conclusion, these results revealed that the prevention of obesity and insulin resistance is associated with the improvement in aerobic capacity induced by AET.Support or Funding InformationFinancial Support: FAPESP # 2015/04948‐4; 2016/20659‐5.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Glucometabolic effects of single and repeated exposure to forced-swimming stressor in Sprague-Dawley rats.

We aimed to evaluate the effects of a single (acute) and repeated (chronic) exposure to forced-swimming stressor on glucose tolerance, insulin sensitivity, lipid profile and glycogen content in male rats. Thirty adult male Sprague-Dawley rats (12 weeks old) were divided randomly into five groups: control group, single exposure (SE) to forced-swim stressor, repeated exposure to forced-swim stressor for 7 days (RE7), 14 days (RE14) and 28 days (RE28). Glucose tolerance test and Homeostatic Model Assessment-Insulin Resistance (HOMA-IR) were undertaken on fasting rats to obtain glucose and insulin profiles. ELISA was performed to assess plasma insulin and corticosterone levels. Total cholesterol, triglyceride, high- and low-density lipoproteins, hepatic and skeletal glycogen content were also determined. Repeated exposure to stressor induced glucose intolerance and insulin resistance in the experimental rats. Results showed that all RE groups exhibited a significantly higher area under the curve compared with others (p=0.0001); similarly, HOMA-IR increased (p=0.0001) in all RE groups compared with control. Prolonged exposure to stressor significantly increased the plasma insulin and corticosterone levels but decreased the glycogen content in the liver and skeletal muscle when compared with the control group. Additionally, chronic stressor significantly increased the total cholesterol and triglyceride levels, however, acute stressor produced significantly elevated high-density lipoproteins level. In conclusion, repeated exposure to forced-swimming stressor induced glucose intolerance and insulin resistance in rats by disrupting the insulin sensitivity as well as heightening the glycogenolysis in the liver and skeletal muscle. Acute stressor was unable to cause glucose intolerance and insulin resistance but it appears that may have a positive effect on the lipid metabolism.

Loss of ovarian function in association with a high-fat diet promotes insulin resistance and disturbs adipose tissue immune homeostasis

Loss of ovarian function, as occurs in menopause or after ovariectomy (OVX), is associated with insulin resistance. Adipose tissue inflammation is suggested to be a key component of obesity-induced insulin resistance in male rodents. However, little is known about the effect of OVX and diet on insulin resistance in association with immune homeostasis. Thus, we conducted this study to determine how high-fat diet (HFD) and OVX, alone or in combination, impacted adipose tissue inflammation and insulin resistance. Nine-week-old sham and OVX-treated C57Bl/6 mice were fed low-fat diet (LFD) or HFD (60%) up to 16 weeks. Glucose metabolism was assessed, and adipose tissue and spleen were characterized for tissue inflammation and immune cell populations. First, we found that HFD induced glucose intolerance in both OVX mice and, to a lesser extent, sham mice. OVX mice fed LFD showed no difference in glucose intolerance compared to sham mice. Additionally, OVX mice only when exposed to HFD displayed a proinflammatory profile in adipose tissue: increased macrophages together with dominant M1-like phenotype and also increased T cells, B cells and NK cells compared to those with intact ovarian function. Together, our findings indicate that loss of ovarian function coupled with an HFD intake promotes insulin resistance and adipose tissue inflammation by disturbing adipose tissue immune homeostasis. These findings have a clinical implication in the dietary guidance for menopausal women.

Metabolic Inflexibility Is an Early Marker of Bed-Rest-Induced Glucose Intolerance Even When Fat Mass Is Stable.

ContextThe effects of energy-balanced bed rest on metabolic flexibility have not been thoroughly examined.ObjectiveWe investigated the effects of 21 days of bed rest, with and without whey protein supplementation, on metabolic flexibility while maintaining energy balance. We hypothesized that protein supplementation mitigates metabolic inflexibility by preventing muscle atrophy.Design and SettingRandomized crossover longitudinal study conducted at the German Aerospace Center, Cologne, Germany.Participants and InterventionsTen healthy men were randomly assigned to dietary countermeasure or isocaloric control diet during a 21-day bed rest.Outcome MeasuresBefore and at the end of the bed rest, metabolic flexibility was assessed during a meal test. Secondary outcomes were glucose tolerance by oral glucose tolerance test, body composition by dual energy X-ray absorptiometry, ectopic fat storage by magnetic resonance imaging, and inflammation and oxidative stress markers.ResultsBed rest decreased the ability to switch from fat to carbohydrate oxidation when transitioning from fasted to fed states (i.e., metabolic inflexibility), antioxidant capacity, fat-free mass (FFM), and muscle insulin sensitivity along with greater fat deposition in muscle (P < 0.05 for all). Changes in fasting insulin and inflammation were not observed. However, glucose tolerance was reduced during acute overfeeding. Protein supplementation did not prevent FFM loss and metabolic alterations.ConclusionsPhysical inactivity triggers metabolic inflexibility, even when energy balance is maintained. Although reduced insulin sensitivity and increased fat deposition were observed at the muscle level, systemic glucose intolerance was detected only in response to a moderately high-fat meal. This finding supports the role of physical inactivity in metabolic inflexibility and suggests that metabolic inflexibility precedes systemic glucose intolerance.