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Molecular phenotyping of multiple mouse strains under metabolic challenge uncovers Elovl2 as a novel regulator of glucose-induced insulin secretion

ABSTRACT: Defective insulin secretion by pancreatic β cells underlies the development of type 2 diabetes (T2D). High fat diet-fed mice are commonly used to study diabetes progression, but studies are usually limited to a single strain, such as C57Bl/6J. Here, we use a systems biology approach to integrate large phenotypic and islet transcriptomic data sets from six commonly used strains fed a high fat or regular chow diet to identify genes associated with glucose intolerance and insulin secretion. One of these genes is Elovl2, encoding very long chain fatty acid elongase 2. ELOVL2 is responsible for the synthesis of the polyunsaturated fatty acid, docosahexaenoic acid (DHA). We show that DHA rescues glucose-induced insulin secretion and cytosolic Ca2+ influx impaired by glucolipotoxicity, and that Elovl2 over-expression is able to restore the insulin secretion defect under these conditions. We propose that increased endogenous DHA levels resulting from Elovl2 up-regulation counteracts the insulin secretion defect associated with glucolipotoxicity. Although we focus our experimental validation on Elovl2, the comprehensive data set and integrative network model we used to identify this candidate gene represents an important novel resource to dissect the molecular aetiology of β cell failure in murine models.

ORGANISM(S): Mus musculus

PROVIDER: GSE78183 | GEO | 2017/04/28

SECONDARY ACCESSION(S): PRJNA312845

REPOSITORIES: GEO

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Project description:Impaired resistance to insulin, the key defect in type 2 diabetes (T2D), is associated with a low capacity to adapt fuel oxidation to fuel availability, i.e., metabolic inflexibility. The hampered metabolic adaptability triggers a further damage of insulin signaling. Since skeletal muscle is the main site of glucose uptake, effectiveness of T2D treatment depends in large on the improvement of insulin sensitivity and metabolic adaptability of the muscle. We have shown previously in mice fed an obesogenic high-fat diet that a combination treatment using n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) and thiazolidinedione (TZD) anti-diabetic drugs preserved metabolic health and synergistically improved muscle insulin sensitivity. We investigated here whether TZD rosiglitazone could elicit the additive beneficial effects on metabolic flexibility when combined with n-3 LC-PUFA. Adult male C57BL/6J mice were fed an obesogenic corn oil-based high-fat diet (cHF) for 8 weeks, or randomly assigned to various dietary treatments: (i) cHF+F, cHF with n-3 LC-PUFA concentrate replacing 15% of dietary lipids; (ii) cHF+ROSI, cHF with 10 mg rosiglitazone/kg diet; and (iii) cHF+F+ROSI, or chow-fed. Indirect calorimetry demonstrated superior preservation of metabolic flexibility to carbohydrates in response to the combination treatment. Metabolomic and gene expression analyses in the muscle suggested distinct and complementary effects of the single treatments, with rosiglitazone augmenting insulin sensitivity by the modulation of branched-chain amino acid metabolism, and n-3 LC PUFA supporting complete oxidation of fatty acids in mitochondria. These beneficial metabolic effects were associated with the activation of the switch between glycolytic and oxidative muscle fibers, especially in the cHF+F+ROSI mice. Our results further support the idea that the combination treatment using n-3 LC-PUFA and TZDs could improve the efficacy of the treatment of obese and diabetic patients. Male C57BL/6N mice had free access to water and Chow. Three-month-old mice were randomly assigned (8 animals per group) to cHF+ROSI diet (lipid content ~35% wt/wt) supplemented with 10 mg rosiglitazone/kg diet, or cHF+F+ROSI in which n-3 LC-PUFA concentrate (46% DHA, 14% EPA, wt/wt, as triglycerides; product EPAX 1050 TG) replaced 15% wt/wt of dietary lipids. The treatment lasted for 8 weeks, whereafter the animals were first fasted for 10 hours during the light phase of the day (between 8.00hr and 18.00hr), than re-fed Chow (starting at 18.00hr), and killed the following day by cervical dislocation under pentobarbital anesthesia (between 9.00hr and 11.00hr); the so-called 'diet-switch protocol'. Gastrocnemius muscle was isolated and used for total RNA isolation.

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Molecular phenotyping of multiple mouse strains under metabolic challenge uncovers Elovl2 as a novel regulator of glucose-induced insulin secretion

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