Skeletal Muscle Insulin Resistance Promotes Increased Hepatic De Novo Lipogenesis, Hyperlipidemia, and Hepatic Steatosis in the Elderly

Author:

Flannery Clare1,Dufour Sylvie2,Rabøl Rasmus1,Shulman Gerald I.123,Petersen Kitt Falk1

Affiliation:

1. Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut

2. Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut

3. Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut

Abstract

Aging is closely associated with muscle insulin resistance, hyperlipidemia, nonalcoholic fatty liver disease (NAFLD), and type 2 diabetes. We examined the hypothesis that muscle insulin resistance in healthy aging promotes increased hepatic de novo lipogenesis (DNL) and hyperlipidemia by altering the distribution pattern of postprandial energy storage. Healthy, normal weight, sedentary elderly subjects pair-matched to young subjects were given two high-carbohydrate meals followed by 13C/1H magnetic resonance spectroscopy measurements of postprandial changes in muscle and liver glycogen and lipid content, and assessment of DNL using 2H2O. Net muscle glycogen synthesis was reduced by 45% (P < 0.007) in the elderly subjects compared with the young, reflecting severe muscle insulin resistance. Net liver glycogen synthesis was similar between groups (elderly, 143 ± 23 mmol/L vs. young, 138 ± 13 mmol/L; P = NS). Hepatic DNL was more than twofold higher in the elderly than in the young subjects (elderly, 14.5 ± 1.4% vs. young, 6.9 ± 0.7%; P = 0.00015) and was associated with approximately threefold higher postprandial hepatic triglyceride (TG) content (P < 0.005) and increased fasting plasma TGs (elderly, 1.19 ± 0.18 mmol/L vs. young, 0.74 ± 0.11 mmol/L; P = 0.02). These results strongly support the hypothesis that muscle insulin resistance in aging promotes hyperlipidemia and NAFLD by altering the pattern of postprandial carbohydrate storage away from muscle glycogen and into hepatic DNL.

Publisher

American Diabetes Association

Subject

Endocrinology, Diabetes and Metabolism,Internal Medicine

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