Augmenter of liver regeneration alleviates lipid accumulation in MASLD through ATF3-CD36 axis

Metabolic dysfunction-associated steatotic liver disease (MASLD) is characterized by excessive lipid deposition in hepatocytes. Augmenter of liver regeneration (ALR, encoded by the Gfer gene), a survival factor in liver cells, protects the liver against various injuries, whereas downregulation of ALR expression accelerates MASLD progression in mice. CD36 functions as a long chain free fatty acid transporter, playing a crucial role during pathogenesis of MASLD. Herein, the expression level of CD36 was found to significantly decrease in ALR-transfected (ALR-Tx) HepG2 cells and upregulated in shRNA-ALR (shALR) cells after oleic acid/palmitic acid treatment. Furthermore, CD36 expression was markedly elevated in MASLD model mice with heterozygous Gfer knockdown (Gfer^+/-) fed a high-fat diet,as well as model mice with liver-specific Gfer knockout (Gfer-CKO). Lipid uptake increased and lipophagy was suppressed in shALR HepG2 cells, and conversly, lipid uptake reduced and lipophagy was promoted in ALR-Tx HepG2 cells. After downregulation of CD36 expression by siRNA-CD36 in shALR cells, lipid accumulation markedly decreased, and lipophagy was stimulated. Further, the mRNA and protein expression of ATF3 (Activating Transcription Factor 3) were found to substantially elevated and decreased in ALR-Tx cells and shALR cells respectively, and CD36 expression was induced after ATF3 was knock down. Our results thus suggest that lack of ALR aggravates lipid deposition in MASLD partly through the ATF3-CD36 axis.