Background: Liver fat is an important determinant of insulin requirements during insulin therapy. Peroxisome proliferator-activated receptor (PPAR)-gamma agonists reduce liver fat. We therefore hypothesized that type 2 diabetic patients using exceptionally high doses of insulin might respond well to addition of a PPARgamma agonist.
Methods: We determined the effect of the PPARgamma agonist rosiglitazone on liver fat and directly measured hepatic insulin sensitivity in 14 patients with type 2 diabetes (aged 51 +/- 3 yr, body mass index 36.7 +/- 1.1 kg/m2), who were poorly controlled (glycosylated hemoglobin A 1c (HbA 1c) 8.9 +/- 0.4%) despite using high doses of insulin (218 +/- 22 IU/d) in combination with metformin. Liver fat content (1H-magnetic resonance spectroscopy), hepatic insulin sensitivity [6 h hyperinsulinemic euglycemic clamp (insulin 0.3 mU/kg.min) combined with [3-3H]glucose], body composition (magnetic resonance imaging), substrate oxidation rates (indirect calorimetry), clinical parameters, and liver enzymes were measured before and after rosiglitazone treatment (8 mg/d) for 8 months.
Results: During rosiglitazone, HbA(1c) decreased from 8.9 +/- 0.4% to 7.8 +/- 0.3% (P = 0.007) and insulin requirements from 218 +/- 22 to 129 +/- 20 IU/d (P = 0.002). Liver fat content decreased by 46 +/- 9% from 20 +/- 3% to 11 +/- 3% (P = 0.0002). Hepatic insulin sensitivity, measured from the percent suppression of endogenous glucose production by insulin, increased from -40 +/- 7% to -89 +/- 12% (P = 0.001). The percent change in liver fat correlated with the percent decrease in HbA 1c (r = 0.53, P = 0.06), insulin dose (r = 0.66, P = 0.014), and suppression of endogenous glucose production (r = 0.76, P = 0.003).
Conclusions: Our results suggest that rosiglitazone may be particularly effective in type 2 diabetic patients who are poorly controlled despite using high insulin doses. The mechanism is likely to involve reduced liver fat and enhanced hepatic insulin sensitivity.