Leptin-dependent fat accumulation triggers autophagy in metabolic dysfunction-associated steatohepatitis model

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a metabolic syndrome characterized by increased fat storage in hepatocytes. In the hepatocytes, autophagy protects against cytotoxic stress and harmful cellular conditions. In the hepatic stellate cells (HSCs), autophagy exerts pro-fibrotic properties and promotes the release of pro-inflammatory metabolites. We investigated the modulation of autophagy as a therapeutic approach for MASLD.

Murine liver tissue and human hepatic cells were analyzed by reverse transcription quantitative polymerase chain reaction (RT-qPCR) and Western blot. Real time fluorescence was performed to monitor the autophagy maturation process. Accumulation of fat was detected by Oil Red O staining. Collagen fibers were detected by picrosirius staining under polarized light.

The loss of leptin in obese mice affected by metabolic dysfunction-associated steatohepatitis (MASH) promoted the over-expression of Becn1, Map1lc3b, Sqstm1, Uvrag and Prkaa1_2 and the accumulation of their proteins. The oleic acid caused an accumulation of fat, followed by the reduction of the autophagy proteins and the increase of the P-AMPK-α in LEP^-/- HepG2 cells and the maturation of autophagosome vesicles in LEP^-/- Hep3B cells. Oleic acid increased the accumulation of fat in human HSCs and the COL1A1 transcript level, but not the collagen I fibers. BECN1 and MAP1LC3B were up-regulated. Instead, all the autophagy proteins were downregulated, but not P-AMPK-α. Instead, the treatment with caffeine prompted neither the transactivation nor the autophagy.

Leptin loss contributes to the autophagy process in obese mice. The administration of oleic acid in LEP^-/- cells prompted autophagy not only in hepatocyte-like cells but also in human HSCs.