Functional Relationships between Lipid Metabolism and Liver Regeneration

Abstract

The regenerative capacity of the liver is well known, and the mechanisms that regulate this process have been extensively studied using experimental model systems including surgical resection and hepatotoxin exposure. The response to primary mitogens has also been used to investigate the regulation of hepatocellular proliferation. Such analyses have identified many specific cytokines and growth factors, intracellular signaling events, and transcription factors that are regulated during and necessary for normal liver regeneration. Nevertheless, the nature and identities of the most proximal events that initiate hepatic regeneration as well as those distal signals that terminate this process remain unknown. Here, we review the data implicating acute alterations in lipid metabolism as important determinants of experimental liver regeneration and propose a novel metabolic model of regeneration based on these data. We also discuss the association between chronic hepatic steatosis and impaired regeneration in animal models and humans and consider important areas for future research.

Figure 1

A metabolic model of liver regeneration: the data reviewed here implicate the metabolic response to hepatic insufficiency as a source of specific signals that initiate liver regeneration. Experimental manipulations employed to alter this metabolic response that are discussed in the text are listed in the box to the left (along with their reported effects on regeneration: suppressed, augmented, and none or variable effects). Models of fatty liver disease (FLD) in which regeneration has been assessed that are discussed in the text are listed in the box to the right. (fld: fatty liver dystrophy mouse; GRKO: glucocorticoid receptor knockout; FASKOL: liver-specific fatty acid synthase knockout mouse; L-Fabp KO: Liver fatty acid binding protein knockout; MTP-IKO: intestine-specific microsomal triglyceride transfer protein knockout; PPAR: peroxisome proliferator-activated receptor).