Mifepristone improves adipose tissue insulin sensitivity in insulin resistant individuals.

BACKGROUND Increased tissue cortisol availability has been implicated in abnormal glucose and fat metabolism in patients with obesity, metabolic syndrome, and type 2 diabetes (T2DM). Our objective was to evaluate whether blockade of glucocorticoid receptor (GR) with mifepristone ameliorates insulin resistance (IR) in overweight/obese subjects with glucose intolerance. METHODS We conducted a randomized, double-blinded, placebo-controlled, cross-over study in overweight/obese individuals (n=16, 44% female) with pre-diabetes or mild T2DM but not clinical hypercortisolism. Mifepristone (50 mg every 6 hours) or placebo was administered for 9 days, followed by crossover to the other treatment arm after a washout period of 6 to 8 weeks. At baseline and following each treatment, oral glucose tolerance test (OGTT) and frequently sampled intravenous glucose tolerance test (FSIVGTT) were performed. Insulin sensitivity was measured using FSIVGTT (primary outcome: insulin sensitivity index; SI) and OGTT (Matsuda index, MI, and oral glucose insulin sensitivity index, OGIS). Hepatic and adipose insulin resistance were assessed using hepatic insulin resistance index (HIRI), and adipose tissue insulin sensitivity index (Adipo-SI) and adipo-IR, derived from the FSIVGTT. RESULTS Mifepristone administration did not alter whole-body glucose disposal indices of insulin sensitivity (SI, MI, and OGIS). GR blockade significantly improved Adipo-SI (61.7±32.9 vs. 42.8±23.9; p=0.002) and reduced Adipo-IR (49.9±45.9 vs. 65.5±43.8; p=0.004), and HIRI (50.2±38.7 vs. 70.0±44.3; p=0.08). Mifepristone increased insulin clearance but did not affect insulin secretion or β-cell glucose sensitivity. CONCLUSION Short-term mifepristone administration improves adipose and hepatic insulin sensitivity among obese individuals with hyperglycemia without hypercortisolism.