Metabolic and anthropometric evaluation of insulin resistance in nondiabetic patients with nonalcoholic steatohepatitis

Abstract

Objectives Insulin resistance is nearly universal in patients with nonalcoholic steatohepatitis (NASH) when tested by glucose tolerance tests or clamp methods. However, the pattern of insulin resistance in these patients after a physiological challenge is unknown. We conducted a study to characterize the metabolic response to a mixed meal in nondiabetic patients with NASH (NDN) and to identify anthropometric determinants of insulin resistance in these patients. Methods Serum insulin, C-peptide, glucose, and free fatty acid (FFA) levels were measured at 0, 30, 60, 90, and 120 min after a 500-kcal standard meal in 18 NDN and 18 age-, gender-, and body mass index (BMI)-matched controls. Correlations were made between insulin resistance and various anthropometric, calorimetric, and serological variables. Results Compared with controls, NDN had significantly higher levels of insulin and C-peptide at baseline and after the mixed meal. However, glucose levels were not different either at baseline or after the meal. NDN had higher fasting levels of FFA than the controls (459 ± 190 vs 339 ± 144 μmol/L, respectively, p = 0.03); however, meal-induced suppression in lipolysis was similar between the two groups (39 ± 113% vs 46 ± 60%, p = 0.8). Insulin resistance was significantly correlated with BMI ( r = 0.39, p = 0.02) and visceral fat ( r = 0.50, p = 0.004). Whereas BMI, percent total body fat, and subcutaneous abdominal fat were similar between the groups, the NASH group had significantly higher percent visceral fat compared with controls (28 ± 10% vs 22 ± 14%, p = 0.02). Conclusion NDN are significantly hyperinsulinemic, both at fasting and after the mixed meal; however, their glucose homeostasis and suppression in lipolysis after a meal challenge are maintained. Insulin resistance in these patients is likely related to their higher visceral fat mass.