with increased body weight and/or adiposity. However, other bloodborne and metabolic factors can infl uence SI and be more substantial predictors of SI under baseline, non-stimulated conditions. We performed a comprehensive assessment of metabolic function in healthy male dogs (total n=90) to identify key determinants of insulin sensitivity. Wholebody SI (SI clamp ), obtained from euglycemic clamp in all animals, was used as the primary outcome variable. SI was also measured independently by minimal model analysis of the IVGTT in a subset of animals (n=36). Total and regional (visceral, subcutaneous) adiposity were measured by MRI (n=90). Glucose-stimulated insulin response was measured either by stepwise hyperglycemic clamp or acute insulin response from the IVGTT (n=86 and 36, respectively). Despite similar body weight (28.7±0.3 kg), baseline trunk adiposity varied nearly 8-fold (172 to 1363 cm 3 ), refl ecting a broad range of both visceral and subcutaneous fat mass. Variability was also refl ected in SI clamp (5.9 to 75.9 dl/min per kg per μU/ml). There was an expected negative association between fasting insulin and SI clamp (p
Integrated Physiology/ Obesity POSTERS & 1675-P Investigation of the Role of Hepatic Vagus Nerve on Hepatic Glucose Metabolism by Use of [6, 6- 2 H 2 ] Glucose TAZU TAHARA, KUNPEI TOKUYAMA, NORIKAZU OGIHARA, MASATOSHI KIKU- CHI, Tokyo, Japan, Ibaraki, Japan, Saitama, Japan It has been documented that portal glucose delivery creates an important signal to enhance liver glycogen deposition. The signaling pathway has been established as a “portal signal”. We have identifi ed that hepatic glycogen phosphorylase (GP) activity is a surrogate marker of portal signal, because GP activity was immediately reduced after glucose load from portal vein, but not from peripherally. To assess the role of hepatic vagus nerve on hepatic glucose metabolism, glucose was infused into unrestrained conscious rats via either portal (Po) or peripheral (Pe) vein at a constant rate, and parameters involved in hepatic glucose metabolism such as glucose production, glucose output and glycogen deposition and GP activity were measured. Rats were subjected to hepatic vagotomy (HV) or sham operation (SO) 7 days prior to the experiment. After 24-hour fasting, tracer amount of [6, 6- 2H 2] glucose was infused for 180 minute into the peripheral vein for equilibration, and kept infusion throughout the experiment. Then, glucose was infused portally or peripherally (13.5 mg/ kg /min) for 120 minutes. Metabolic parameters were determined by the mass isotopomer distribution analysis method. In SO, hepatic glucose output was signifi cantly reduced in Po than Pe after 30 minutes glucose infusion (3.13 and 6.05 mg / kg / min), while the reduction in glucose output observed in SO was disappeared in HV, and kept higher levels (16.7 and 23.2 mg / kg / min in Po and Pe). Hepatic glycogen deposition was signifi cantly higher in Po than Pe after 120 minutes glucose infusion (57.1±2.1 vs 35.7±1.7μmol / g liver) in SO, whereas the glycogen deposition in Po was reduced in HV compared with SO during portal glucose infusion and was no siginifi cantly difference between Po and Pe (28.7±7.4vs 25.0±7.2 μmol / g liver). GP activity in SO was lower in Po than Pe after 120 minutes glucose infusion(1.04±0.21 vs 1.54±0.03μmol / g liver), but the difference in GP activity between Po and Pe was not observed in HV (0.91±0.18 and 0.93±0.17 μmol / g liver). From the data we conclude that hepatic vagus nerve is important for the regulation of hepatic glucose production and glycogen deposition. & 1676-P Control of Blood Glucose in the Absence of Hepatic Glucose Production Due to an Induction of Renal and Intestinal Gluconeogenesis by Gluca gon FABIENNE RAJAS, ELODIE MUTEL, AMANDINE GAUTIER-STEIN, AYA ABDUL- WAHED, MARTA AMIGO, ANNE STEFANUTTI, GILLES MITHIEUX, Lyon, France Since the pioneering work of Claude Bernard in the 19 th Century, the scientifi c community has considered the liver to be the major source of endogenous glucose production (EGP). We investigated the importance of the liver as a source of EGP, by using a mouse model of liver-specifi c deletion of the glucose-6 phosphatase catalytic subunit gene (LG6pc-/- mice), encoding an essential enzyme for glucose production. We previously showed that an absence of hepatic glucose release had no major effect on the fasting plasma glucose concentration. Instead, there was an early sequential induction of gluconeogenesis in the kidney and intestine, the alternative gluconeogenic organs. Here, we investigated molecular mechanisms underlying expression changes of gluconeogenic genes (Pck1 encoding phosphoenol carboxykinase and G6pc) in both kidney and intestine of LG6pc-/- mice. Male adult B6.g6pc lox/lox .SACre ERT2/+ mice were treated with tamoxifen to obtain Lg6pc-/-. Blood was withdrawn for metabolic studies from 6h-fasted mice. Chip assays were performed with phospho-CREB antibody on G6pc and Pck1 promoters. At 6h of fasting, glucagon level was higher in LG6pc-/- mice than in control mice (538±9 pg/ml vs 280±19 pg/ml in control) while LG6pc-/- mice showed lower insulin levels than that of control mice. After confi rming the presence of glucagon receptors in the kidney and intestine, we showed that P-CREB bound to the G6pc promoter in both organs. In contrast, P-CREB was only bound to the Pck1 promoter in the intestine. Interestingly, we obtained identical results in fed control mice in response of an IP injection of glucagon. Complementary data showed that Pck1 expression was mainly induced in the kidneys by metabolic acidosis observed in LG6pc-/-. In conclusion, our study provides a defi nitive quantitative estimate of the capacity of extrahepatic gluconeogenesis to sustain fasting EGP, regardless of the contribution of the liver. Moreover, glucagon plays a central role to induce gluconeogenesis in the kidney and intestine, as it is well known in the liver. Supported by: Agence Nationale de la Recherche and Association Française des glycogénoses For author disclosure information, see page 785. INTEGRATED CATEGORY PHYSIOLOGY—LIVER A456 & 1677-P Attenuation of Hepatic Steatosis Is Associated with Increased Hepatic Phospholipid Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) in Diet-Induced Obese (DIO) Rats Fed a Canola/ Flax Oil Blend DANIELLE P. HANKE, CARLA G. TAYLOR, PETER C. ZAHRADKA, Winnipeg, MB, Canada Insulin resistance is the most important pathogenic factor in the etiology of non-alcoholic fatty liver disease (NAFLD). NAFLD has been associated with reduced omega-3 (n-3) fatty acid status. It has been proposed that n-3 fatty acids may prevent hepatic steatosis and progression to NAFLD by increasing hepatic fatty acid oxidation via peroxisome proliferator activated receptor a (PPARa) and decreasing hepatic fatty acid synthesis via sterol regulatory element-binding protein-1c (SREBP-1c). Furthermore, the effi cacy of the plantbased n-3 fatty acid, α-linolenic acid (ALA), as a dietary precursor of EPA and DHA for modulating hepatic steatosis is unknown. Thus, the present study investigated hepatic steatosis, hepatic fatty acid composition and markers of fatty acid oxidation and synthesis in 6 week old Obese Prone Sprague Dawley rats fed high fat (55% energy) diets containing various fat types including high oleic canola oil, canola oil, a canola/fl ax oil blend (C/F, 3:1), saffl ower oil, soybean oil, or lard for 12 weeks. Upon completion of the study, the C/F and weight matched (WM) groups had the lowest percent liver lipid. The C/F group had the highest amount of ALA in their diet and this resulted in the highest total n-3 and EPA in hepatic PL. The C/F group also had one of the highest DHA and lowest arachidonic acid (n-6) concentrations in hepatic PL. Conversely, the type of fat or oil did not affect hepatic protein levels of PPARa and acyl-CoA oxidase or hepatic protein levels of SREBP-1c and acetyl-CoA carboxylase. In conclusion, our data indicates that the C/F diet, which was high in the plant-based n-3 ALA, can attenuate hepatic steatosis and favourably alter hepatic fatty acid concentrations of PL by increasing EPA and DHA. However, the reduction in hepatic steatosis by the canola/fl ax oil blend was not explained by the upregulation of PPARa and/or inhibition or suppression of SREBP-1c. Supported by: Canola Council of Canada & 1678-P Overexpression of SIRT1 in the Liver Deacetylates X-Box Binding Protein 1 and Attenuates Hepatic Steatosis and Insulin Resistance in ob/ob Mice YU LI, KAZUTO NAKAMURA, WALSH KENNETH, MENGWEI ZANG, Boston, MA Endoplasmic reticulum (ER) stress has been implicated in the pathophysiology of human type 2 diabetes (T2DM). Small molecular activators of SIRT1 were shown to prevent diet-induced obesity and insulin resistance. Our previous studies have indicated that SIRT1 and resveratrol regulate hepatocyte lipid metabolism through activating AMPK. To extend these fi ndings, the goal of the present study was to explore the mechanism of the therapeutic impact of NAD-dependent deacetylase SIRT1 on metabolic deterioration in T2DM. We demonstrated that adenovirus-mediated overexpression of SIRT1 in the liver of ob/ob mice attenuated hepatic steatosis, lowered hepatic lipids contents, and ameliorated glucose tolerance and systemic insulin resistance. Enhanced insulin sensitivity by SIRT1 was associated with decreased ER stress markers such as GRP78 and CHOP. Importantly, X-box binding protein 1(XBP1), a critical ER stress marker, was identifi ed as a direct target of SIRT1, since co-immunoprecipitation showed the spliced form of endogenous XBP1 physically interacted with SIRT1 in the mouse embryonic fi broblasts (MEFs). Hepatic overexpression of SIRT1 increased its interaction with spliced XBP1 and resulted in the deacetylation of spliced XBP1 in ob/ ob mouse livers, as compared to those of Ad-GFP-injected mice. Hepatic overexpression of SIRT1 also decreased SREBP-1c, key enzyme involved in lipid synthesis, in ob/ob mouse livers. In contrast, the promoter activity of SREBP-1c target, fatty acid synthase, was increased by SIRT1 -/- MEFs, compared with SIRT1 +/+ MEFs. Interestingly, serum levels of infl ammatory marker monocyte chemotactic protein-1 (MCP-1) were reduced upon SIRT1 treatment. Moreover, resveratrol decreased tunicamycin-induced NF-κB promoter activity and mRNA levels of proinfl ammatory cytokine TNFα in HepG2 cells. Taken together, our results 1) identify XBP1 as a novel target of SIRT1 through the deacetylation regulation in the liver and in vitro; 2) reveal that deacetylation of XBP1 by SIRT1 in the liver may serve as a therapeutic strategy to attenuate obesity-induced ER stress, infl ammation, hepatic steatosis, and insulin resistance. & Guided Audio Tour poster <strong>ADA</strong>-Funded Research
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