ABSTRACT: Nonalcoholic fatty liver disease (NAFLD) plays a crucial role in type 2 diabetes and hepatocellular carcinoma. The major underlying pathogenesis is hepatic insulin resistance. The aim of the present study was to characterize patients with NAFLD with paradoxically normal hepatic insulin sensitivity relative to patients with NAFLD with hepatic insulin resistance. We recruited 26 patients with NAFLD and divided them into three groups ranked by the level of hepatic insulin sensitivity (HIS; high-HIS, mid-HIS, low-HIS), as assessed by the hyperinsulinemic-euglycemic clamp studies using stable isotope. Hepatic insulin sensitivity of the high-HIS group was identical to that of the non-NAFLD lean control (clamped percent suppression of endogenous glucose production, 91.1% ± 5.2% versus 91.0% ± 8.5%, respectively) and was significantly higher than that of the low-HIS group (66.6% ± 7.5%; P < 0.01). Adiposity (subcutaneous, visceral, intrahepatic, and muscular lipid content), hepatic histopathology, and expression levels of various genes by using liver biopsies, muscle, and adipose tissue insulin sensitivity, plasma metabolites by metabolomics analysis, putative biomarkers, and lifestyles were assessed and compared between the high-HIS and low-HIS groups. Among these, adipose tissue insulin sensitivity assessed by clamped percent suppression of free fatty acid, serum high molecular weight adiponectin, and plasma tricarboxylic acid cycle metabolites, such as citric acid and cis-aconitic acid, were significantly higher in the high-HIS group compared to the low-HIS group. In contrast, there were no differences in adiposity, including intrahepatic lipid content assessed by proton magnetic resonance spectroscopy (28.3% ± 16.1% versus 20.4% ± 9.9%, respectively), hepatic histopathology, other putative biomarkers, and lifestyles. Conclusion: High levels of adipose tissue insulin sensitivity, serum high molecular weight adiponectin, and plasma tricarboxylic acid cycle metabolites are unique characteristics that define patients with hepatic insulin-sensitive NAFLD regardless of intrahepatic lipid content. (Hepatology Communications 2017;1:634-647).
