10 In order to explore whether serum adiponectin levels were functionally relevant for hepatic lipid metabolism, the authors demonstrated a correlation between hepatic adiponectin staining and AMPK and acetyl-CoA carboxylase 1 and 2 (ACC1/ACC2) phosphorylation. Notably, phosphorylation of ACC2, the main ACC isoform in human liver, inhibits this enzyme and reduces its product, malonylCoA,

a CPT1α inhibitor, therefore indirectly promoting FA oxidation.11 Previous studies in patients with NASH revealed that adipoRI expression was stable, while adipoRII was reduced concomitantly with reduced hepatic see more adiponectin expression.12 Given the specific roles of adipoRI and RII, their relative amounts in advanced NASH may be important to estimate the net response. Since adipoRI remains stable and regulates AMPK, ALK targets it is also remarkable that FA synthesis and its main regulator SREBP1c are inhibited in burned-out NASH patients.13 It is thus possible that adiponectin activation of adipoRI leads to AMPK activation which subsequently inhibits

SREBP1c expression by phosphorylation of a serine residue near the cleavage site of SREBP1c, thereby repressing endogenous FA synthesis and forcing lipid droplet catabolism in the liver (Fig. 1). Conversely, low adipoRII expression may concomitantly promote oxidative stress and inflammation (Fig. 1). Unfortunately, potential changes of hepatic adipoRI or RII receptors expressions were not addressed in the current study. A key question concerns potential mechanisms which might cause elevated adiponectin levels in advanced NASH. Adiponectin levels are known to be elevated in experimental models and patients with liver cirrhosis,14 with the highest levels being observed in cholestasis,15 suggesting a potential link to biliary constituents such as BAs. Previous studies established that adiponectin levels correlated with fibrotic markers such as transient elastography, hyaluronate, and serum BA.16 Serum BA levels are increased

Janus kinase (JAK) in NASH patients and correlate with disease progression.17 Adiponectin is secreted into the bile, which represents an important way of elimination, as reflected by increased levels in cholestatic patients and bile duct-ligated mice.15 It is therefore plausible that parallel increases of serum adiponectin and BA levels might simply reflect progressive liver dysfunction leading to burnt-out NASH. Apart from their detergent properties in lipid digestion, BAs have more recently been recognized to possess additional hormonal actions that control a range of metabolic and immune functions throughout the body by way of the farnesoid X receptor (FXR) and the G-protein coupled BA receptor (GPBAR1/TGR5).18 As such, BA-activating FXR and TGR5 regulate cholesterol, triglyceride and glucose metabolism, as well as energy expenditure.