Ceramide-mediated mitochondrial dysfunction in nonobese nonalcoholic fatty liver disease: A regulatory role for serine palmitoyltransferase subunit 2.

This study investigated the pathological relevance of the serine palmitoyltransferase long chain base subunit 2 (Sptlc2)-ceramide axis in nonobese nonalcoholic fatty liver disease (NAFLD), focusing on hepatic steatosis, inflammation, oxidative stress, and mitochondrial dysfunction. A nonobese NAFLD rat model was established using a high-temperature dry-fried soybean diet. Integrated liquid chromatography-mass spectrometry-based proteomic and metabolomic analyses were used to identify candidate pathways. Sptlc2 function was validated by AAV2/8-mediated liver-directed knockdown in vivo, lentiviral knockdown in primary hepatocytes, and C2-ceramide rescue experiments. Multi-omics profiling identified Sptlc2 as a sphingolipid metabolism-related candidate in the model. Sptlc2 knockdown reduced long-chain ceramide accumulation, hepatic lipid deposition, inflammatory cytokine expression, oxidative stress, and hepatocyte injury. In primary hepatocytes, Sptlc2 silencing improved mitochondrial respiration, membrane potential, calcium and reactive oxygen species homeostasis, and mitochondrial ultrastructure. These protective effects were partially reversed by C2-ceramide in vitro and in vivo. The Sptlc2-ceramide axis contributes to ceramide accumulation, hepatic lipotoxicity, inflammatory activation, and mitochondrial dysfunction in this nonobese NAFLD model, suggesting its potential relevance as a therapeutic target for further investigation.