Skeletal muscle insulin resistance promotes increased hepatic de novo lipogenesis, hyperlipidemia, and hepatic steatosis in the elderly

Diabetes. 2012 Nov;61(11):2711-7. doi: 10.2337/db12-0206. Epub 2012 Jul 24.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aging / blood
  • Aging / metabolism*
  • Dietary Carbohydrates / adverse effects
  • Dietary Carbohydrates / metabolism
  • Fatty Liver / etiology
  • Fatty Liver / metabolism*
  • Female
  • Glycogen / metabolism
  • Humans
  • Hyperlipidemias / etiology
  • Hyperlipidemias / metabolism*
  • Insulin Resistance*
  • Lipogenesis*
  • Liver / metabolism*
  • Male
  • Metabolic Syndrome / physiopathology
  • Muscle, Skeletal / metabolism*
  • Non-alcoholic Fatty Liver Disease
  • Postprandial Period
  • Triglycerides / blood
  • Triglycerides / metabolism
  • Young Adult

Substances

  • Dietary Carbohydrates
  • Triglycerides
  • Glycogen