Several hypotheses have been proposed to explain the etiology of adipose tissue dysfunction in obesity.25-30 A genetic link to adipose tissue IR is suggested by the observation that nonobese subjects with a strong family history of T2DM already

have early defects in adipose tissue function,25, 31 although these studies have not focused on the effect of adipose tissue on hepatic steatosis. Although MHO subjects had a much worse BMI, their metabolic profile was similar to that of lean insulin-sensitive subjects. LBH589 purchase However, it was not completely normal because there was already a trend toward worsening hepatic insulin sensitivity (Table 1) and a significant reduction in plasma adiponectin, insulin suppression of plasma FFA, and established muscle insulin resistance (Fig. 4B). Nevertheless, this reduction was not as severe as in Q1. Patients in Q1 already had significant signs of metabolic distress with higher AST/ALT (Fig. 2), dyslipidemia (i.e., high TG/low HDL-C) (Fig. 3), liver and muscle IR (Fig. 4), hepatic steatosis (Table 2) and NASH (Fig. 6). Of note, visceral fat was not different across quartiles and failed to explain the Sirolimus price metabolic and histological differences. This is consistent with recent work suggesting that hepatic fat is more closely associated with the metabolic abnormalities in NAFLD than visceral fat.32 Though the metabolic disturbances described here

cannot be entirely ascribed to dysfunctional adipose tissue, their strong association with dysfunctional fat suggests an important role in the pathogenesis of metabolic/histological defects in NAFLD. It also suggests that lipotoxicity has a low threshold in NAFLD and that its impact varies among target tissues. Skeletal muscle appeared rapidly affected by dysfunctional adipose tissue (Q1-Q3), whereas it was more gradual at the level of the liver (Fig. 4). However, at the extreme

of adipose tissue IR (Q4), all metabolic variables (i.e., AST/ALT, TG/HDL-C, and hepatic/muscle IR) further deteriorated, suggesting that target tissues continue to be affected and susceptible to worsening lipotoxicity. This has clinical implications for lipotoxicity in the development and treatment of steatohepatitis and fibrosis. The lack of an association between an exacerbation medchemexpress of adipose tissue IR and steatohepatitis (Fig. 6) does not mean that, upon reversal of adipose tissue IR with a TZD, there cannot be a marked improvement in steatohepatitis, as previously reported.9 Indeed, the low threshold for steatohepatitis (already observed in Q1) would suggest that even modest reversal of adipose tissue IR may be beneficial in NASH. In our hands, reversal of adipose tissue IR by a TZD had the closest correlation with necroinflammation (r = 0.47, P < 0.01), but also was associated with changes in steatosis (r = 0.29; P = 0.049) and, to a lesser degree, fibrosis (0.