Influence of obesity, weight loss, and free fatty acids on skeletal muscle clock gene expression

Am J Physiol Endocrinol Metab. 2020 Jan 1;318(1):E1-E10. doi: 10.1152/ajpendo.00289.2019. Epub 2019 Oct 15.


The molecular circadian clock plays a role in metabolic homeostasis. We tested the hypothesis obesity and systemic factors associated with insulin resistance affect skeletal muscle clock gene expression. We determined clock gene expression in skeletal muscle of obese women (n = 5) and men (n = 18) before and 6 mo after Roux-en-Y gastric bypass (RYGB) surgery and normal-weight controls (women n = 6, men n = 8). Skeletal muscle clock gene expression was affected by obesity and weight loss. CRY1 mRNA (P = 0.05) was increased and DBP mRNA (P < 0.05) was decreased in obese vs. normal weight women and restored to control levels after RYGB-induced weight loss. CLOCK, CRY1, CRY2, and DBP mRNA (P < 0.05) was decreased in obese men compared with normal weight men. Expression of all other clock genes was unaltered by obesity or weight loss in both cohorts. We correlated clock gene expression with clinical characteristics of the participants. Among the genes studied, DBP and PER3 expression was inversely correlated with plasma lipids in both cohorts. Circadian time-course studies revealed that core clock genes oscillate over time (P < 0.05), with BMAL1, CIART, CRY2, DBP, PER1, and PER3 expression profiles altered by palmitate treatment. In conclusion, skeletal muscle clock gene expression and function is altered by obesity, coincident with changes in plasma lipid levels. Palmitate exposure disrupts clock gene expression in myotubes, indicating that dyslipidemia directly alters the circadian program. Strategies to reduce lipid overload and prevent elevations in nonesterified fatty acid and cholesterol levels may sustain circadian clock signals in skeletal muscle.

Keywords: circadian rhythm; clock genes; free fatty acids; insulin resistance; obesity; skeletal muscle; weight loss.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ARNTL Transcription Factors / genetics
  • Adult
  • CLOCK Proteins / genetics
  • Case-Control Studies
  • Cryptochromes / genetics
  • DNA-Binding Proteins / genetics
  • Enzyme Inhibitors / pharmacology
  • Fatty Acids, Nonesterified / metabolism
  • Female
  • Gastric Bypass
  • Gene Expression
  • Healthy Volunteers
  • Humans
  • Male
  • Middle Aged
  • Muscle Fibers, Skeletal / drug effects
  • Muscle Fibers, Skeletal / metabolism
  • Muscle, Skeletal / metabolism*
  • Obesity / genetics*
  • Obesity / metabolism
  • Obesity / surgery
  • Palmitic Acid / pharmacology
  • Period Circadian Proteins / genetics
  • Primary Cell Culture
  • RNA, Messenger / metabolism*
  • Transcription Factors / genetics
  • Weight Loss*


  • ARNTL Transcription Factors
  • BMAL1 protein, human
  • CRY1 protein, human
  • CRY2 protein, human
  • Cryptochromes
  • DBP protein, human
  • DNA-Binding Proteins
  • Enzyme Inhibitors
  • Fatty Acids, Nonesterified
  • PER1 protein, human
  • PER3 protein, human
  • Period Circadian Proteins
  • RNA, Messenger
  • Transcription Factors
  • Palmitic Acid
  • CLOCK Proteins
  • CLOCK protein, human