Combining metformin and aerobic exercise training in the treatment of type 2 diabetes and NAFLD in OLETF rats

Melissa A. Linden, Justin A. Fletcher, E. Matthew Morris, Grace M. Meers, Monica L. Kearney, Jacqueline M. Crissey, M. Harold Laughlin, Frank W. Booth, James R. Sowers, Jamal A. Ibdah, John P. Thyfault, R. Scott Rector

Research output: Contribution to journalArticlepeer-review

60 Scopus citations


Here, we sought to compare the efficacy of combining exercise and metformin for the treatment of type 2 diabetes and nonalcoholic fatty liver disease (NAFLD) in hyperphagic, obese, type 2 diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats. OLETF rats (age: 20 wk, hyperglycemic and hyperinsulinemic; n = 10/group) were randomly assigned to sedentary (O-SED), SED plus metformin (O-SED + M; 300 mg·kg-1·day-1), moderate-intensity exercise training (O-EndEx; 20 m/min, 60 min/day, 5 days/wk treadmill running), or O-EndEx + M groups for 12 wk. Long-Evans Tokushima Otsuka (L-SED) rats served as nonhyperphagic controls. O-SED + M, O-EndEx, and O-EndEx + M were effective in the management of type 2 diabetes, and all three treatments lowered hepatic steatosis and serum markers of liver injury; however, O-EndEx lowered liver triglyceride content and fasting hyperglycemia more than O-SED + M. In addition, exercise elicited greater improvements compared with metformin alone on postchallenge glycemic control, liver diacylglycerol content, hepatic mitochondrial palmitate oxidation, citrate synthase, and β-HAD activities and in the attenuation of markers of hepatic fatty acid uptake and de novo fatty acid synthesis. Surprisingly, combining metformin and aerobic exercise training offered little added benefit to these outcomes, and in fact, metformin actually blunted exercise-induced increases in complete mitochondrial palmitate oxidation and β-HAD activity. In conclusion, aerobic exercise training was more effective than metformin administration in the management of type 2 diabetes and NAFLD outcomes in obese hyperphagic OLETF rats. Combining therapies offered little additional benefit beyond exercise alone, and findings suggest that metformin potentially impairs exercise-induced hepatic mitochondrial adaptations.

Original languageEnglish (US)
Pages (from-to)E300-E310
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Issue number3
StatePublished - Feb 1 2014
Externally publishedYes


  • De novo lipogenesis
  • Exercise training
  • Hepatic mitochondria
  • Metformin
  • Nonalcoholic fatty liver disease
  • Otsuka Long-Evans Tokushima Fatty rats

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Physiology (medical)


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