In vivo regulation of SREBP-1c in skeletal muscle: effects of nutritional status, glucose, insulin, and leptin

Am J Physiol Regul Integr Comp Physiol. 2004 Jul;287(1):R218-27. doi: 10.1152/ajpregu.00377.2003. Epub 2004 Mar 4.

Abstract

Sterol regulatory element binding protein-1c (SREBP-1c), a transcription factor that is important for mediating insulin effects on metabolic gene expression in liver during the fasted-to-fed transition, is also expressed in skeletal muscle. However, the regulation and role of SREBP-1c in skeletal muscle are poorly understood. The present study compared the effects of nutritional status, physiological hyperinsulinemic clamps, and adenovirus-mediated hyperleptinemia (HLEP) in rats on expression of SREBP-1c and other metabolic genes in skeletal muscle. Three- and 6-h refeeding of 18-h-fasted animals increased levels of SREBP-1c mRNA and the SREBP-1 protein (full length and mature) in gastrocnemius muscle (P < 0.05). Fatty acid synthase (FAS) and hexokinase II (HKII) mRNA levels were also increased by refeeding, and uncoupling protein 3 (UCP3) mRNA level was decreased (all P < 0.05). Surprisingly, 3-h hyperinsulinemic clamps did not increase gastrocnemius muscle SREBP-1c and FAS mRNA levels or SREBP-1 protein levels but did increase HKII mRNA levels and decrease UCP3 mRNA levels (P < 0.05). HLEP reduced refeeding-induced increases of SREBP-1c and FAS mRNA levels but did not reduce the level of SREBP-1 protein. We conclude that 1) skeletal muscle SREBP-1c gene expression is regulated by nutritional status in a fashion similar to that observed in liver and adipose tissue, 2) physiological hyperinsulinemia is not sufficient to imitate the effects of refeeding on SREBP-1c gene expression, and 3) leptin suppresses refeeding effects on SREBP-1c mRNA levels.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Blood Glucose / physiology*
  • Blotting, Northern
  • Body Weight / drug effects
  • CCAAT-Enhancer-Binding Proteins / biosynthesis*
  • DNA Primers
  • DNA-Binding Proteins / biosynthesis*
  • Eating / drug effects
  • Gene Expression Regulation / drug effects
  • Glucose Clamp Technique
  • Hyperinsulinism / metabolism
  • Insulin / blood
  • Insulin / physiology*
  • Leptin / blood
  • Leptin / physiology*
  • Liver / metabolism
  • Male
  • Muscle, Skeletal / metabolism*
  • Nutritional Status / physiology*
  • RNA, Messenger / biosynthesis
  • Rats
  • Rats, Wistar
  • Sterol Regulatory Element Binding Protein 1
  • Transcription Factors*

Substances

  • Blood Glucose
  • CCAAT-Enhancer-Binding Proteins
  • DNA Primers
  • DNA-Binding Proteins
  • Insulin
  • Leptin
  • RNA, Messenger
  • Srebf1 protein, rat
  • Sterol Regulatory Element Binding Protein 1
  • Transcription Factors