Glutathione S-transferase Mu 3 Mitigates Alcohol-induced Hepatic Lipid Dysregulation via PYGM Suppression

Hepatic steatosis is the most prevalent and earliest pathological change in alcoholic hepatitis and represents a critical initiating event in alcohol-associated liver disease (ALD). However, the molecular mechanisms underlying alcohol-induced hepatic lipid dysregulation remain incompletely understood. Here, we investigated the role of glutathione S-transferase Mu 3 (GSTM3) in hepatic lipid metabolism during ALD and explored its underlying mechanism. Using an ALD mouse model and ethanol (EtOH)-treated AML-12 cells, we examined the functional interaction between GSTM3 and glycogen phosphorylase, muscle associated (PYGM), which was identified as a downstream candidate through RNA sequencing (RNA-seq). We found that GSTM3 expression was markedly upregulated in primary hepatocytes isolated from ALD mice and EtOH-treated AML-12 cells, whereas GSTM3 deficiency significantly exacerbated hepatic lipid accumulation both in vivo and in vitro. Mechanistically, GSTM3 knockdown resulted in increased PYGM expression at both the mRNA and protein levels. Importantly, rescue experiments revealed that concomitant silencing of PYGM partially alleviated the enhanced lipid accumulation induced by GSTM3 deficiency, indicating that PYGM contributes to the steatotic phenotype downstream of GSTM3 loss. Collectively, these findings identify GSTM3 as a critical protective regulator of alcohol-induced hepatic steatosis and reveal a previously unrecognized GSTM3-PYGM axis that modulates lipid metabolism in ALD, suggesting GSTM3 as a potential therapeutic target for the treatment of ALD.