Glucose Intolerance In Mice Research Articles

Vascepa protects against high-fat diet-induced glucose intolerance, insulin resistance, and impaired β-cell function

SummaryOmega-3 fatty acid prescription drugs, Vascepa (≥96% eicosapentaenoic acid [EPA] ethyl ester) and Lovaza (46.5% EPA and 37.5% docosahexaenoic acid ethyl ester) are known therapeutic regimens to treat hypertriglyceridemia. However, their impact on glucose homeostasis, progression to type 2 diabetes, and pancreatic beta cell function are not well understood. In the present study, mice were treated with Vascepa or Lovaza for one week prior to six weeks of high-fat diet feeding. Vascepa but not Lovaza led to reduced insulin resistance, reduced fasting insulin and glucose, and improved glucose intolerance. Vascepa improved beta cell function, reduced liver triglycerides with enhanced expression of hepatic fatty acid oxidation genes, and altered microbiota composition. Vascepa has protective effects on diet-induced insulin resistance and glucose intolerance in mice.

227-LB: GLP-1 Activation of HCN Channels Increases Glucose-Stimulated β- and δ- Cell Ca2+ Oscillation Frequency

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels control human β-cell insulin secretion. Here, we examined if HCN channels impact glucagon-like-peptide 1 (GLP-1) receptor modulation of islet Ca2+ handling. We found that Liraglutide (100nM LIRA), a GLP-1 analog, increased mouse β-cell Ca2+ oscillation frequency and cAMP levels in high (11 mM) but not low glucose. Similarly, a subset of human β-cells (65%) show LIRA-induced elevations in Ca2+ oscillation frequency (by 70%, P<0.001) under stimulatory glucose (7 mM) conditions. While mouse islet HCN inhibition (20 μM ivabradine) did not alter glucose-stimulated (9 mM) Ca2+ oscillation frequency, it prevented LIRA-induced changes of islet Ca2+ fluctuations. As LIRA is used to treat type-2-diabetes, we examined and demonstrated that islets from high fat diet-fed, glucose intolerant mice also responded to LIRA with increased Ca2+ oscillation frequency (by 93%, P<0.01). These changes in β-cell Ca2+ handling may contribute to LIRA-mediated increased insulin secretion, which could also play a role in LIRA inhibition of glucagon secretion. However, as somatostatin also inhibits glucagon secretion, we next investigated the influence of LIRA on 𝛿;-cells. Interestingly, LIRA increased Ca2+ oscillation frequency equivalently in β- and 𝛿;-cells (by 85%, P<0.0001), which showed synchronized Ca2+ fluctuations. To establish the origin of synchronization cues, we ablated either β- or δ-cells and determined the LIRA-mediated effect on Ca2+ handling in remaining δ- or β-cells, respectively. Although δ-cell ablation did not affect the LIRA-mediated elevations in β-cell Ca2+ oscillation frequency, β-cell ablation interfered with glucose- and LIRA-mediated δ-cell Ca2+ fluctuations. As the kinetics of pulsatile insulin secretion dictate insulin sensitivity, the data presented here suggests that GLP-1 stimulation of islet HCN channels may improve peripheral insulin sensitivity in diabetics treated with LIRA. Disclosure K. E. Zaborska: None. K. L. Jordan: None. P. Dadi: None. M. Dickerson: None. S. M. Graff: None. D. Jacobson: None.

Vitamin B6 deficiency disrupts serotonin signaling in pancreatic islets and induces gestational diabetes in mice

In pancreatic islets, catabolism of tryptophan into serotonin and serotonin receptor 2B (HTR2B) activation is crucial for β-cell proliferation and maternal glucose regulation during pregnancy. Factors that reduce serotonin synthesis and perturb HTR2B signaling are associated with decreased β-cell number, impaired insulin secretion, and gestational glucose intolerance in mice. Albeit the tryptophan-serotonin pathway is dependent on vitamin B6 bioavailability, how vitamin B6 deficiency impacts β-cell proliferation during pregnancy has not been investigated. In this study, we created a vitamin B6 deficient mouse model and investigated how gestational deficiency influences maternal glucose tolerance. Our studies show that gestational vitamin B6 deficiency decreases serotonin levels in maternal pancreatic islets and reduces β-cell proliferation in an HTR2B-dependent manner. These changes were associated with glucose intolerance and insulin resistance, however insulin secretion remained intact. Our findings suggest that vitamin B6 deficiency-induced gestational glucose intolerance involves additional mechanisms that are complex and insulin independent.

Dietary sodium chloride attenuates increased β-cell mass to cause glucose intolerance in mice under a high-fat diet.

Excessive sodium salt (NaCl) or fat intake is associated with a variety of increased health risks. However, whether excessive NaCl intake accompanied by a high-fat diet (HFD) affects glucose metabolism has not been elucidated. In this study, C57BL/6J male mice were fed a normal chow diet (NCD), a NCD plus high-NaCl diet (NCD plus NaCl), a HFD, or a HFD plus high-NaCl diet (HFD plus NaCl) for 30 weeks. No significant differences in body weight gain, insulin sensitivity, and glucose tolerance were observed between NCD-fed and NCD plus NaCl-fed mice. In contrast, body and liver weights were decreased, but the weight of epididymal white adipose tissue was increased in HFD plus NaCl-fed compared to HFD-fed mice. HFD plus NaCl-fed mice had lower plasma glucose levels in an insulin tolerance test, and showed higher plasma glucose and lower plasma insulin levels in an intraperitoneal glucose tolerance test compared to HFD-fed mice. The β-cell area and number of islets were decreased in HFD plus NaCl-fed compared to HFD-fed mice. Increased Ki67-positive β-cells, and increased expression levels of Ki67, CyclinB1, and CyclinD1 mRNA in islets were observed in HFD-fed but not HFD plus NaCl-fed mice when compared to NCD-fed mice. Our data suggest that excessive NaCl intake accompanied by a HFD exacerbates glucose intolerance, with impairment in insulin secretion caused by the attenuation of expansion of β-cell mass in the pancreas.

Fortifying Butterfat with Soybean Oil Attenuates the Onset of Diet-Induced Non-Alcoholic Steatohepatitis and Glucose Intolerance.

The addition of plant oils such as soybean oil (S) to a diet rich in saturated fatty acids is discussed as a possible route to prevent or diminish the development of metabolic disease. Here, we assessed whether a butterfat-rich diet fortified with S affects the development of early non-alcoholic steatohepatitis (NASH) and glucose intolerance. Female C57BL/6J mice were fed a standard-control diet (C); a fat-, fructose-, and cholesterol-rich diet (FFC, 25E% butterfat, 50% (wt./wt.) fructose, 0.16% (wt./wt.) cholesterol); or FFC supplemented with S (FFC + S, 21E% butterfat + 4E% S) for 13 weeks. Indicators of liver damage, inflammation, intestinal barrier function, and glucose metabolism were measured. Lipopolysaccharide (LPS)-challenged J774A.1 cells were incubated with linolenic and linoleic acids (ratio 1:7.1, equivalent to S). The development of early NASH and glucose intolerance was significantly attenuated in FFC + S–fed mice compared to FFC-fed mice associated with lower hepatic toll-like receptor-4 mRNA expression, while markers of intestinal barrier function were significantly higher than in C-fed mice. Linolenic and linoleic acid significantly attenuated LPS-induced formation of reactive nitrogen species and interleukin-1 beta mRNA expression in J774A.1 cells. Our results indicate that fortifying butterfat with S may attenuate the development of NASH and glucose intolerance in mice.

The metabesity factor HMG20A potentiates astrocyte survival and reactive astrogliosis preserving neuronal integrity.

Rationale: We recently demonstrated that the 'Metabesity' factor HMG20A regulates islet beta-cell functional maturity and adaptation to physiological stress such as pregnancy and pre-diabetes. HMG20A also dictates central nervous system (CNS) development via inhibition of the LSD1-CoREST complex but its expression pattern and function in adult brain remains unknown. Herein we sought to determine whether HMG20A is expressed in the adult CNS, specifically in hypothalamic astrocytes that are key in glucose homeostasis and whether similar to islets, HMG20A potentiates astrocyte function in response to environmental cues.Methods: HMG20A expression profile was assessed by quantitative PCR (QT-PCR), Western blotting and/or immunofluorescence in: 1) the hypothalamus of mice exposed or not to either a high-fat diet or a high-fat high-sucrose regimen, 2) human blood leukocytes and adipose tissue obtained from healthy or diabetic individuals and 3) primary mouse hypothalamic astrocytes exposed to either high glucose or palmitate. RNA-seq and cell metabolic parameters were performed on astrocytes treated or not with a siHMG20A. Astrocyte-mediated neuronal survival was evaluated using conditioned media from siHMG20A-treated astrocytes. The impact of ORY1001, an inhibitor of the LSD1-CoREST complex, on HMG20A expression, reactive astrogliosis and glucose metabolism was evaluated in vitro and in vivo in high-fat high-sucrose fed mice.Results: We show that Hmg20a is predominantly expressed in hypothalamic astrocytes, the main nutrient-sensing cell type of the brain. HMG20A expression was upregulated in diet-induced obesity and glucose intolerant mice, correlating with increased transcript levels of Gfap and Il1b indicative of inflammation and reactive astrogliosis. Hmg20a transcript levels were also increased in adipose tissue of obese non-diabetic individuals as compared to obese diabetic patients. HMG20A silencing in astrocytes resulted in repression of inflammatory, cholesterol biogenesis and epithelial-to-mesenchymal transition pathways which are hallmarks of reactive astrogliosis. Accordingly, HMG20A depleted astrocytes exhibited reduced mitochondrial bioenergetics and increased susceptibility to apoptosis. Neuron viability was also hindered in HMG20A-depleted astrocyte-derived conditioned media. ORY1001 treatment rescued expression of reactive astrogliosis-linked genes in HMG20A ablated astrocytes while enhancing cell surface area, GFAP intensity and STAT3 expression in healthy astrocytes, mimicking the effect of HMG20A. Furthermore, ORY1001 treatment protected against obesity-associated glucose intolerance in mice correlating with a regression of hypothalamic HMG20A expression, indicative of reactive astrogliosis attenuation with improved health status.Conclusion: HMG20A coordinates the astrocyte polarization state. Under physiological pressure such as obesity and insulin resistance that induces low grade inflammation, HMG20A expression is increased to induce reactive astrogliosis in an attempt to preserve the neuronal network and re-establish glucose homeostasis. Nonetheless, a chronic metabesity state or functional mutations will result in lower levels of HMG20A, failure to promote reactive astrogliosis and increase susceptibility of neurons to stress-induced apoptosis. Such effects could be reversed by ORY1001 treatment both in vitro and in vivo, paving the way for a new therapeutic approach for Type 2 Diabetes Mellitus.

LRRK2 Inhibition Ameliorates Dexamethasone-Induced Glucose Intolerance via Prevents Impairment in GLUT4 Membrane Translocation in Adipocytes.

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are associated with Parkinson's disease. LRRK2 is a large protein with multiple functional domains, including a guanosine 5'-triphosphate (GTP)-binding domain and a protein kinase domain. Recent studies indicated that the members of the Rab GTPase family, Rab8a and Rab10, which are involved in the membrane transport of the glucose transporter type 4 (GLUT4) during insulin-dependent glucose uptake, are phosphorylated by LRRK2. However, the physiological role of LRRK2 in the regulation of glucose metabolism is largely unknown. In the present study, we investigated the role of LRRK2 using dexamethasone (DEX)-induced glucose intolerance in mice. LRRK2 knockout (KO) mice exhibited suppressed glucose intolerance, even after treatment with DEX. The phosphorylation of LRRK2, Rab8a and Rab10 was increased in the adipose tissues of DEX-treated wild-type mice. In addition, inhibition of the LRRK2 kinase activity prevented the DEX-induced inhibition of GLUT4 membrane translocation and glucose uptake in cultured 3T3-L1 adipocytes. These results suggest that LRRK2 plays an important role in glucose metabolism in adipose tissues.

The adaptor protein APPL2 controls glucose-stimulated insulin secretion via F-actin remodeling in pancreatic β-cells

Filamentous actin (F-actin) cytoskeletal remodeling is critical for glucose-stimulated insulin secretion (GSIS) in pancreatic β-cells, and its dysregulation causes type 2 diabetes. The adaptor protein APPL1 promotes first-phase GSIS by up-regulating soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein expression. However, whether APPL2 (a close homology of APPL1 with the same domain organization) plays a role in β-cell functions is unknown. Here, we show that APPL2 enhances GSIS by promoting F-actin remodeling via the small GTPase Rac1 in pancreatic β-cells. β-cell specific abrogation of APPL2 impaired GSIS, leading to glucose intolerance in mice. APPL2 deficiency largely abolished glucose-induced first- and second-phase insulin secretion in pancreatic islets. Real-time live-cell imaging and phalloidin staining revealed that APPL2 deficiency abolished glucose-induced F-actin depolymerization in pancreatic islets. Likewise, knockdown of APPL2 expression impaired glucose-stimulated F-actin depolymerization and subsequent insulin secretion in INS-1E cells, which were attributable to the impairment of Ras-related C3 botulinum toxin substrate 1 (Rac1) activation. Treatment with the F-actin depolymerization chemical compounds or overexpression of gelsolin (a F-actin remodeling protein) rescued APPL2 deficiency-induced defective GSIS. In addition, APPL2 interacted with Rac GTPase activating protein 1 (RacGAP1) in a glucose-dependent manner via the bin/amphiphysin/rvs-pleckstrin homology (BAR-PH) domain of APPL2 in INS-1E cells and HEK293 cells. Concomitant knockdown of RacGAP1 expression reverted APPL2 deficiency-induced defective GSIS, F-actin remodeling, and Rac1 activation in INS-1E cells. Our data indicate that APPL2 interacts with RacGAP1 and suppresses its negative action on Rac1 activity and F-actin depolymerization thereby enhancing GSIS in pancreatic β-cells.

Intestinal Dysbiosis Correlates With Sirolimus-induced Metabolic Disorders in Mice.

Long-time use of pharmacological immunosuppressive agents frequently leads to metabolic disorders. Most studies have focused on islet toxicity leading to posttransplantation diabetes mellitus. In contrast, the link between intestinal dysbiosis and immunosuppressive drug-induced metabolic disorders remains unclear. We established a mouse model of metabolic abnormality via sirolimus treatment. Fecal microbiota was examined using 16S rRNA gene MiSeq sequencing. Intestinal barrier function was assessed using fluorescein isothiocyanate-dextran assay and mucus immunostaining. Systemic inflammation was determined using a multiplexed fluorescent bead-based immunoassay. Sirolimus induced dyslipidemia and glucose intolerance in mice in a dose-dependent manner. Interestingly, the clinical-mimicking dose of sirolimus altered the intestinal microbiota community, which was characterized by the enrichment of Proteobacteria, depletion of Akkermansia, and potential function shifts to those involved in lipid metabolism and the immune system. In addition, the clinical-mimicking dose of sirolimus reduced the thickness of the intestinal mucosal layer, increased the intestinal permeability, and enriched the circulating pro-inflammatory factors, including interleukin (IL)-12, IL-6, monocyte chemotactic protein 1, granulocyte-macrophage colony stimulating factor, and IL-1β. Our results showed a close association between intestinal dysbiosis, intestinal barrier failure, systemic inflammation, and metabolic disorders. Furthermore, we demonstrated that oral intervention in the gut microbiota by Lactobacillus rhamnosus HN001 protected against intestinal dysbiosis, especially by depleting the lipopolysaccharide-producing Proteobacteria, and attenuated the sirolimus-induced systemic inflammation, dyslipidemia, and insulin resistance. Our study demonstrated a potentially causative role of intestinal dysbiosis in sirolimus-induced metabolic disorders, which will provide a novel therapeutic target for transplant recipients.

Impact of different fructose concentrations on metabolic and behavioral parameters of male and female mice

Clinical evidence has shown that a high consumption of sugar-sweetened beverages is a risk factor for developing obesity and metabolic syndrome. There has also been increasing interest in the potential effects of high-fructose intake on behavior. The present study evaluated sex differences in behavioral and metabolic characteristics in response to chronic fructose intake in mice. Swiss mice (3-months-old) had access to tap water or fructose-water solution (at 15% or 30% w/v) ad libitum for nine weeks. After the 8 weeks, the mice were submitted to a battery of behavioral tests. A glucose tolerance test was performed one day after these behavioral tests, and the next day blood was collected for biochemical analysis. At a 15% concentration, fructose-intaking resulted in higher plasma cholesterol levels and glucose intolerance in mice that paralleled with a passive stress-coping behavior in the female mice and lower self-care behavior in the male and the female mice. At a 30% concentration, fructose-intaking resulted in higher body mass gain and higher plasma cholesterol and triglycerides levels in the male and the female mice, whereas glucose intolerance was more pronounced in the male mice. Spatial memory impairments and lower self-care behavior were observed in the male and the female mice, while passive stress-coping behavior was observed only in the female mice. Collectively, high-fructose intake induces metabolic and behavioral alterations in mice, with the males being more susceptible to glucose metabolism dysfunctions and the females to depressive-like endophenotypes.

Comparative study of the effects of diosmin and diosmetin on fat accumulation, dyslipidemia, and glucose intolerance in mice fed a high-fat high-sucrose diet.

This study compared the effects of diosmin and its aglycone, diosmetin, on body weight, liver fat, serum cholesterol, and glucose intolerance in male C57BL/6 mice fed a high‐fat high‐sucrose (HFHS) diet for 12 weeks. The mice were divided into four groups that received the following diets: normal diet (ND), HFHS diet, HFHS diet with 0.5% diosmin, and HFHS diet with 0.5% diosmetin. The body weight increased significantly in the HFHS diet group but decreased significantly in the HFHS diet with 0.5% diosmin group. The diosmin and diosmetin treatment inhibited fat accumulation in liver and epididymal tissues, and improved glucose intolerance by lowering glucose levels during a glucose tolerance test; these effects were greater in the diosmin group than those in the diosmetin group. Furthermore, only diosmin significantly ameliorated dyslipidemia, by reducing TC and LDL‐C levels, while diosmetin had little effect on these parameters. Taken together, the results showed that diosmin and diosmetin can prevent fat accumulation and glucose intolerance; however, diosmin was more effective and also showed an antidyslipidemic effect.

Liver-specific ceramide reduction alleviates steatosis and insulin resistance in alcohol-fed mice

Alcohol’s impairment of both hepatic lipid metabolism and insulin resistance (IR) are key drivers of alcoholic steatosis, the initial stage of alcoholic liver disease (ALD). Pharmacologic reduction of lipotoxic ceramide prevents alcoholic steatosis and glucose intolerance in mice, but potential off-target effects limit its strategic utility. Here, we employed a hepatic-specific acid ceramidase (ASAH) overexpression model to reduce hepatic ceramides in a Lieber-DeCarli model of experimental alcoholic steatosis. We examined effects of alcohol on hepatic lipid metabolism, body composition, energy homeostasis, and insulin sensitivity as measured by hyperinsulinemic-euglycemic clamp. Our results demonstrate that hepatic ceramide reduction ameliorates the effects of alcohol on hepatic lipid droplet (LD) accumulation by promoting VLDL secretion and lipophagy, the latter of which involves ceramide cross-talk between the lysosomal and LD compartments. We additionally demonstrate that hepatic ceramide reduction prevents alcohol’s inhibition of hepatic insulin signaling. These effects on the liver are associated with a reduction in oxidative stress markers and are relevant to humans, as we observe peri- LD ASAH expression in human ALD. Together, our results suggest a potential role for hepatic ceramide inhibition in preventing ALD.

Exposure to Low Doses of Dechlorane Plus Promotes Adipose Tissue Dysfunction and Glucose Intolerance in Male Mice.

The prevalence of type 2 diabetes (T2D) continues to increase worldwide. It is well established that genetic susceptibility, obesity, overnutrition and a sedentary life style are risk factors for the development of T2D. However, more recently, studies have also proposed links between exposure to endocrine-disrupting chemicals (EDCs) and altered glucose metabolism. Human exposure to environmental pollutants that are suspected to have endocrine disruptor activity is ubiquitous. One such chemical is Dechlorane Plus (DP), a flame retardant, that is now detected in humans and the environment. Here we show that exposure of mice to low, environmentally relevant doses of DP promoted glucose intolerance in mice fed a high-fat diet independent of weight gain. Furthermore, DP had pronounced effects on the adipose tissue, where it induced the development of hypertrophied white adipose tissue (WAT), and increased serum levels of resistin, leptin, and plasminogen activator inhibitor-1. In addition, DP exposure induced "whitening" of brown adipose tissue (BAT), and reduced BAT uncoupling protein 1 expression. Importantly, some of these effects occurred even when the mice were fed a regular, low-fat, diet. Finally, WAT adipogenic markers were reduced with DP treatment in the WAT. We also show that DP directly inhibited insulin signaling in murine adipocytes and human primary subcutaneous adipocytes in vitro. Taken together, our results show that the exposure to low and environmentally relevant levels of DP may contribute to the development of T2D.

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.

2078-P: APPL2 Deficiency Diminishes Glucose-Stimulated Insulin Secretion in Pancreatic Beta Cells

In response to elevated postprandial blood glucose, remodeling of F-actin enables exocytosis of insulin granules from pancreatic β cells. Dysregulation of F-actin remodeling contributes to defective glucose-stimulated insulin secretion (GSIS) in β cells and subsequent type 2 diabetes. The adaptor protein APPL1 potentiates GSIS and prevents β cell loss in diabetes, but the role of its close homolog APPL2 in β cell function remains unknown. Here we demonstrated that APPL2 controls GSIS by Rac1-mediated F-actin depolymerization via interaction with Rac GTPase activating protein 1 (RacGAP1). β-cell specific deletion of APPL2 induced defective GSIS and glucose intolerance in mice. Ex vivo study revealed a dramatic reduction in both first- and second-phase GSIS in islets, accompanied by a dysregulation of F-actin remodeling. Consistently, knockdown of APPL2 caused impaired glucose-induced F-actin remodeling and insulin secretion in INS-1E β cells. The defects were mainly due to the inactivation of Rac1- the key player controlling insulin granule secretion via F-actin remodeling. Ectopic expression of constitutively active Rac1 mutant rescued the defective GSIS and F-actin remodeling in APPL2 deficient β cells. Furthermore, we identified RacGAP1 as an interacting partner of APPL2. RacGAP1 interacted with and regulate activity of Rac1, and overexpression of RacGAP1 significantly suppressed glucose-induced F-actin depolymerization, whereas co-expression with APPL2 antagonized this suppressive effect. In addition, the defects in APPL2 knockdown β cells were largely reversed by simultaneous downregulation of RacGAP1 or co-expression of constitutively active Rac1 mutant. In summary, our study suggest that APPL2 potentiates GSIS by antagonizing the inhibitory effect of RacGAP1 on Rac1 activation and F-actin remodeling and insulin secretion in β cells, highlighting the importance of APPL2 in the regulation of GSIS in pancreatic β cells and glucose homeostasis. Disclosure H. Lin: None. Funding National Natural Science Foundation of China (81970675)

213-OR: Obesity-Induced Astrogliosis Is Regulated by the Diabesity Factor HMG20A

It is well established that systemic glucose homeostasis is imparted by an intricate cross-talk among several organs including the central nervous system (CNS) and pancreatic islets. In analogy to islet beta cells, hypothalamic astrocytes are glucose sensors that facilitate the CNS response to changing metabolic environment. Therefore, astrocytes and beta cells may share a common genetic signature implicated in coupling glucose metabolism to cellular output. We recently demonstrated that the diabesity factor HMG20A is essential for beta-cell functional maturity and adaptation to physiological stress (obesity, type 2 diabetes and pregnancy). As this chromatin remodelling factor also dictates CNS development, we sought to determine whether HMG20A is expressed in astrocytes and whether it potentiates astrocyte function in response to environmental cues. We found that HMG20A is expressed in hypothalamic astrocytes and is upregulated in diet-induced obesity and glucose-intolerant mice, correlating with increased transcript levels of GFAP and IL-1β, indicative of reactive astrocytes (astrogliosis). High glucose, but not lipids, transiently decreased HMG20A expression in isolated mouse primary astrocytes. HMG20A silencing in astrocytes resulted in repression of pro-inflammatory as well as lipid and glucose metabolism genes. These pathways are up-regulated in activated astrocytes (astrogliosis) to resolve stress conditions. As such astrocyte depleted of HMG20A were more susceptible to cell death. Furthermore, motor neuron viability in astrocyte conditioned media was significantly hindered after HMG20A depletion in astrocytes. We posit that HMG20A is involved in the astrocyte polarization state. Under physiological pressure such as obesity, HMG20A expression may be transiently decreased by high glucose but long-term it is increased to induce astrogliosis in an attempt to preserve the neuronal network and glucose homeostasis. Disclosure J.M. Mellado-Gil: None. E. Fuente-Martin: None. P.I. Lorenzo: None. N. Cobo-Vuilleumier: None. J.A. Guerrero-Martínez: None. S.Y. Romero-Zerbo: None. J.M. Franco: None. J. Perez-Cabello: None. M. Alvarez-Dolado: None. D. Pozo: None. F.J. Bermudez-Silva: None. J.C. Reyes: None. B.R. Gauthier: None. Funding ISCIII (PI13/00593 to B.R.G.), (PI13/00309 to F.J.B-S.); Ministerio de Economia y Competidividad/Fondos FEDER (PI10/00871, PI13/00593, BFU2017-83588-P to B.R.G.); BFU2017-85420-R (to J.C.R.); (JCI-2012-12491, IJCI-2015-26238 to E.F-M.); Consejería de Salud Junta de Andalucía (PI-0006-2016 to E.F-M.)

SUN-346 A Natural Antibody Against Oxidized Phospholipids Attenuates Age-Related Bone Loss and Prevents Age-Related Glucose Intolerance in Mice

Lipid peroxidation produces oxidized phospholipids (OxPL) such as oxidized phosphatidylcholine. These compounds react with amino groups of proteins and lipids to form adducts called oxidation specific epitopes (OSEs), which are proinflammatory moieties present on oxidized low density lipoproteins and on apoptotic cells and, unless removed, cause extensive cell damage. Natural antibodies (NAb) produced by B-1 lymphocytes, bind OxPL and prevent their inflammatory activity. E06 is a NAb that recognizes the phosphocholine moiety of OxPL. We previously showed that transgenic expression of a single chain (scFv) form of the antigen-binding domain of E06 IgM (E06-scFv) increases cancellous and cortical bone mass in both male and female mice by increasing bone formation. Age-related bone loss is characterized by a decline in osteoblast number and bone formation, associated with increased oxidative stress and lipid peroxidation. These findings, together with the evidence that serum anti-OxPL IgM titers decrease with age, suggest that increased OxPL formation and decreased anti-OxPL antibodies may contribute to age-related bone loss. Like humans, mice exhibit an age-dependent worsening in glucose tolerance, mainly due to alteration in body composition and increased fat tissue. Chronic low grade inflammation and oxidative stress are associated with development of diabetes mellitus and B-1 lymphocytes have been shown to be protective against obesity associated inflammation, glucose intolerance, and insulin resistance. We tested the hypothesis that overexpression of E06-scFv could attenuate age-related bone loss and glucose intolerance. Serial BMD measurements by DXA of both female and male C57BL/6 E06-scFv transgenic mice (and their WT littermates) up to 22 and 24 months, respectively, showed that E06-scFv attenuated age-related bone loss at the spine and femur in both sexes. As revealed by microCT analysis, this effect was due to the attenuation of the age-associated decline in cancellous bone in both sexes. Additionally, both male and female E06-scFv transgenic mice accumulated less fat mass than WT littermates during aging. Intraperitoneal glucose tolerance test, at 15 months of age, revealed that glucose tolerance was greater in both male and female E06-ScFv mice than in respective WT littermates and did not differ from the glucose tolerance of young mice, indicating that E06-scFv improves glucose metabolism. These data suggest that OxPL impair both age-related bone loss and age-related glucose intolerance. Therefore, targeting OxPL with a neutralizing antibody such as E06, represents a prototypic therapeutic intervention that may simultaneously ameliorate important age-associated diseases.

Hepatic Slug epigenetically promotes liver lipogenesis, fatty liver disease, and type 2 diabetes.

De novo lipogenesis is tightly regulated by insulin and nutritional signals to maintain metabolic homeostasis. Excessive lipogenesis induces lipotoxicity, leading to nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes. Genetic lipogenic programs have been extensively investigated, but epigenetic regulation of lipogenesis is poorly understood. Here, we identified Slug as an important epigenetic regulator of lipogenesis. Hepatic Slug levels were markedly upregulated in mice by either feeding or insulin treatment. In primary hepatocytes, insulin stimulation increased Slug expression, stability, and interactions with epigenetic enzyme lysine-specific demethylase-1 (Lsd1). Slug bound to the fatty acid synthase (Fasn) promoter where Slug-associated Lsd1 catalyzed H3K9 demethylation, thereby stimulating Fasn expression and lipogenesis. Ablation of Slug blunted insulin-stimulated lipogenesis. Conversely, overexpression of Slug, but not a Lsd1 binding-defective Slug mutant, stimulated Fasn expression and lipogenesis. Lsd1 inhibitor treatment also blocked Slug-stimulated lipogenesis. Remarkably, hepatocyte-specific deletion of Slug inhibited the hepatic lipogenic program and protected against obesity-associated NAFLD, insulin resistance, and glucose intolerance in mice. Conversely, liver-restricted overexpression of Slug, but not the Lsd1 binding-defective Slug mutant, had the opposite effects. These results unveil an insulin/Slug/Lsd1/H3K9 demethylation lipogenic pathway that promotes NAFLD and type 2 diabetes.

Altered pancreas remodeling following glucose intolerance in pregnancy in mice.

Gestational diabetes mellitus increases the risk of dysglycemia postpartum, in part, due to pancreatic β-cell dysfunction. However, no histological evidence exists comparing endocrine pancreas after healthy and glucose-intolerant pregnancies. This study sought to address this knowledge gap, in addition to exploring the contribution of an inflammatory environment to changes in endocrine pancreas after parturition. We used a previously established mouse model of gestational glucose intolerance induced by dietary low protein insult from conception until weaning. Pancreas and adipose samples were collected at 7, 30 and 90 days postpartum for histomorphometric and cytokine analyses, respectively. Glucose tolerance tests were performed prior to euthanasia and blood was collected via cardiac puncture. Pregnant female mice born to dams fed a low protein diet previously shown to develop glucose intolerance at late gestation relative to controls continued to be glucose intolerant until 1 month postpartum. However, glucose tolerance normalized by 3 months postpartum. Glucose intolerance at 7 days postpartum was associated with lower beta- and alpha-cell fractional areas and higher adipose levels of pro-inflammatory cytokine, interleukin-6. By 3 months postpartum, a compensatory increase in the number of small islets and a higher insulin to glucagon ratio likely enabled euglycemia to be attained in the previously glucose-intolerant mice. The results show that impairments in endocrine pancreas compensation in hyperglycemic pregnancy persist after parturition and contribute to prolonged glucose intolerance. These impairments may increase the susceptibility to development of future type 2 diabetes.

Deconstructing circadian disruption: Assessing the contribution of reduced peripheral oscillator amplitude on obesity and glucose intolerance in mice.

Disturbing the circadian regulation of physiology by disruption of the rhythmic environment is associated with adverse health outcomes but the underlying mechanisms are unknown. Here, the response of central and peripheral circadian clocks to an advance or delay of the light-dark cycle was determined in mice. This identified transient damping of peripheral clocks as a consequence of an advanced light-dark cycle. Similar depression of peripheral rhythm amplitude was observed in mice exposed to repeated phase shifts. To assess the metabolic consequences of such peripheral amplitude depression in isolation, temporally chimeric mice lacking a functional central clock (Vgat-Cre+ Bmal1fl/fl ) were housed in the absence of environmental rhythmicity. In vivo PER2::LUC bioluminescence imaging of anesthetized and freely moving mice revealed that this resulted in a state of peripheral amplitude depression, similar in severity to that observed transiently following an advance of the light-dark cycle. Surprisingly, our mice did not show alterations in body mass or glucose tolerance in males or females on regular or high-fat diets. Overall, our results identify transient damping of peripheral rhythm amplitude as a consequence of exposure to an advanced light-dark cycle but chronic damping of peripheral clocks in isolation is insufficient to induce adverse metabolic outcomes in mice.