Early Hepatic Insulin Resistance Precedes the Onset of Diabetes in Obese C57BLKS-db/db Mice

Department of Medicine, University of California, Los Angeles, Los Angeles, California, USA.
Diabetes (Impact Factor: 8.1). 07/2010; 59(7):1616-25. DOI: 10.2337/db09-0878
Source: PubMed


To identify metabolic derangements contributing to diabetes susceptibility in the leptin receptor-deficient obese C57BLKS/J-db/db (BKS-db) mouse strain.
Young BKS-db mice were used to identify metabolic pathways contributing to the development of diabetes. Using the diabetes-resistant B6-db strain as a comparison, in vivo and in vitro approaches were applied to identify metabolic and molecular differences between the two strains.
Despite higher plasma insulin levels, BKS-db mice exhibit lower lipogenic gene expression, rate of lipogenesis, hepatic triglyceride and glycogen content, and impaired insulin suppression of gluconeogenic genes. Hepatic insulin receptor substrate (IRS)-1 and IRS-2 expression and insulin-stimulated Akt-phosphorylation are decreased in BKS-db primary hepatocytes. Hyperinsulinemic-euglycemic clamp studies indicate that in contrast to hepatic insulin resistance, skeletal muscle is more insulin sensitive in BKS-db than in B6-db mice. We also demonstrate that elevated plasma triglyceride levels in BKS-db mice are associated with reduced triglyceride clearance due to lower lipase activities.
Our study demonstrates the presence of metabolic derangements in BKS-db before the onset of beta-cell failure and identifies early hepatic insulin resistance as a component of the BKS-db phenotype. We propose that defects in hepatic insulin signaling contribute to the development of diabetes in the BKS-db mouse strain.

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Available from: Jason K Kim, Oct 09, 2015
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    • "Gene deletion and overexpression technology have been well established in mice for over two decades, allowing researchers to create single gene mutant mice that display phenotypes which are useful in the development of type 2 diabetes therapy [2]. There are also mouse models of type 2 diabetes that have arisen due to spontaneous mutations such as the leptin deficient ob/ob and leptin receptor deficient db/db mice [3]. The C57/BL6 mouse strain fed a high-fat diet is a commonly used animal model in the development of potential therapies for type 2 diabetes [4]. "
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    ABSTRACT: The development of new therapies for the treatment of type 2 diabetes requires robust, reproducible and well validated in vivo experimental systems. Mice provide the most ideal animal model for studies of potential therapies. Unlike larger animals, mice have a short gestational period, are genetically similar, often give birth to many offspring at once and can be housed as multiple groups in a single cage. The mouse model has been extensively metabolically characterized using different tests. This report summarizes how these tests can be executed and how arising data are analyzed to confidently determine changes in insulin resistance and insulin secretion with high reproducibility. The main tests for metabolic assessment in the mouse reviewed here are the glucose clamp, the intravenous and the oral glucose tolerance tests. For all these experiments, including some commonly adopted variants, we describe: (i) their performance; (ii) their advantages and limitations; (iii) the empirical formulas and mathematical models implemented for the analysis of the data arising from the experimental procedures to obtain reliable measurements of peripheral insulin sensitivity and beta cell function. Finally, a list of previous applications of these methods and analytical techniques is provided to better comprehend their use and the evidences that these studies yielded.
    Journal of Diabetes Research 05/2013; 2013:986906. DOI:10.1155/2013/986906 · 2.16 Impact Factor
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    • "Mutations in the leptin receptor gene cause severe obesity and insulin resistance in rodents and humans. The cause of obesity in db/db mice is associated with a deficiency of leptin receptors depending on the genetic background, and these animals exhibit most of the human characteristics of type 2 diabetes including hyperglycemia in fasting and fed states, hyperinsulinemia, and insulin resistance [23, 24]. For this reason, db/db mice are valuable as an experimental model associated with type 2 diabetes. "
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    ABSTRACT: The present study was conducted to examine whether Kangen-karyu has an ameliorative effect on diabetes-induced alterations such as oxidative stress and apoptosis in the liver of type 2 diabetic db/db mice. Kangen-karyu (100 or 200 mg/kg body weight/day, p.o.) was administered every day for 18 weeks to db/db mice and its effect was compared with vehicle-treated db/db and m/m mice. The administration of Kangen-karyu decreased the elevated serum glucose and leptin concentrations in db/db mice, and reduced the increased oxidative biomarkers including the generation of reactive oxygen species and lipid peroxidation in the liver. The db/db mice exhibited the upregulation of nicotinamide adenine dinucleotide phosphate oxidase subunits, NF-E2-related factor 2, heme oxygenase-1, nuclear factor-kappa B, cyclooxygenase-2, and inducible nitric oxide synthase levels in the liver; however, Kangen-karyu treatment significantly reduced those expressions. Moreover, the augmented expressions of apoptosis-related proteins, Bax, cytochrome c, c-Jun N-terminal kinase (JNK), phosphor-JNK, AP-1, and caspase-3, were downregulated by Kangen-karyu administration. Hematoxylin-eosin staining showed that the increased hepatocellular damage in the liver of db/db mice improved by Kangen-karyu administration. Our findings support the therapeutic evidence for Kangen-karyu ameliorating the development of diabetic hepatic complications via regulating oxidative stress and apoptosis.
    Evidence-based Complementary and Alternative Medicine 08/2012; 2012:143489. DOI:10.1155/2012/143489 · 1.88 Impact Factor
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    • "Human hepatoma HepG2 cells purchased from ATCC were grown at 37°C in 5% CO2 in DMEM medium with 10% FBS, 500 mM Hepes, glutamine, penicillin (100 U/ml) and streptomycin (100 ug/ml) (Invitrogen). Hepatic tissue was harvested from 3-mth old male C57/Bl6 mice and primary hepatic cell culture performed as previously reported [23]. At 30% confluence, HepG2 or primary hepatocyte cells were treated with glucose free DMEM with 5% FBS overnight and then incubated with glucose ( 5.5 and 11.1 mM) or fructose ( 0.55 mM) concentrations alone or fructose (0.55 mM) in combination with physiological glucose (5.5 mM) or high glucose (11.1 mM) for 72 hours. "
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    ABSTRACT: Obesity, type 2 diabetes and hyperlipidemia frequently coexist and are associated with significantly increased morbidity and mortality. Consumption of refined carbohydrate and particularly fructose has increased significantly in recent years and has paralled the increased incidence of obesity and diabetes. Human and animal studies have demonstrated that high dietary fructose intake positively correlates with increased dyslipidemia, insulin resistance, and hypertension. Metabolism of fructose occurs primarily in the liver and high fructose flux leads to enhanced hepatic triglyceride accumulation (hepatic steatosis). This results in impaired glucose and lipid metabolism and increased proinflammatory cytokine expression. Here we demonstrate that fructose alters glucose-stimulated expression of activated acetyl CoA carboxylase (ACC), pSer hormone sensitive lipase (pSerHSL) and adipose triglyceride lipase (ATGL) in hepatic HepG2 or primary hepatic cell cultures in vitro. This was associated with increased de novo triglyceride synthesis in vitro and hepatic steatosis in vivo in fructose- versus glucose-fed and standard-diet fed mice. These studies provide novel insight into the mechanisms involved in fructose-mediated hepatic hypertriglyceridemia and identify fructose-uptake as a new potential therapeutic target for lipid-associated diseases.
    Lipids in Health and Disease 01/2011; 10(1):20. DOI:10.1186/1476-511X-10-20 · 2.22 Impact Factor
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