Fatty Liver Has Stronger Association With Insulin Resistance Than Visceral Fat Accumulation in Nonobese Japanese Men

CONTEXT: Asians have a high prevalence of insulin resistance, even in the nonobese state. Whereas both visceral fat accumulation (VFA) and fatty liver (FL) have been shown to be associated with insulin resistance, it is still unclear which is a better marker to predict insulin resistance in nonobese Asians. OBJECTIVE: The aim of this study was to investigate the relation between VFA or FL and insulin resistance in nondiabetic nonobese Japanese men who do not have diabetes. DESIGN AND PARTICIPANTS: We studied 87 nonobese (body mass index <25 kg/m(2)) Japanese men without diabetes. Using a two-step hyperinsulinemic euglycemic clamp, we evaluated insulin sensitivity in adipose tissue, muscle, and liver. Intrahepatic lipid and abdominal visceral fat area were measured by (1)H-magnetic resonance spectroscopy and MRI, respectively. Subjects were divided into four groups based on the presence or absence of VFA (visceral fat area ≥100 cm(2)) and FL (intrahepatic lipid ≥ 5%): control (non-VFA, non-FL; n = 54), VFA only (n = 18), FL only (n = 7), and VFA plus FL (n = 8). RESULTS: Subjects in the FL only and VFA plus FL groups had insulin resistance in adipose tissue and muscle, as well as relatively lower hepatic insulin sensitivity. The specific insulin sensitivities in these organs were comparable in the VFA only and control groups. CONCLUSIONS: In nonobese Japanese men without diabetes, subjects with FL only or VFA plus FL but not VFA only had insulin resistance, suggesting that FL may be a more useful clinical marker than VFA to predict insulin resistance in nonobese Japanese men without diabetes.