Transcriptomic analysis identifies FABP5 as a candidate regulator of lipid accumulation in metabolic dysfunction-associated fatty liver disease.

OBJECTIVE: The pathogenesis of metabolic dysfunction-associated fatty liver disease (MAFLD) is very complex, which has not been fully revealed as so far. This study aimed to identify differentially expressed genes involved in the pathogenesis of MAFLD using Oxford Nanopore Technologies (ONT) transcriptomic sequencing and to investigate the potential role of fatty acid-binding protein 5 (FABP5) in hepatic lipid accumulation. METHODS: Male C57/BL6N mice with fed either a high-fat, high-fructose (HFHF) diet for 19 weeks to induce MAFLD or a standard chow diet. Liver tissues were subjected to histological examination and ONT transcriptomic analysis and selected differentially expressed genes involved in lipid transport and metabolism were validated by quantitative reverse-transcription PCR (RT-qPCR). Serum FABP5 concentrations were measured in HFHF-fed mice and patients with MAFLD using enzyme-linked immunosorbent assay (ELISA). In vitro, Huh-7 cells were treated with different concentrations of palmitic acid (PA) to induce lipid accumulation. FABP5 was subsequently overexpressed in PA-treated cells, followed by assessment of intracellular lipid accumulation and the expression of genes involved in fatty acid oxidation. RESULT: HFHF-fed mice exhibited marked hepatic steatosis, hepatocyte ballooning, and lobular inflammation. ONT transcriptomic analysis identified 400 differentially expressed genes between the HFHF and chow groups, including 12 genes involved in lipid transport and metabolism. RT-qPCR validation showed that hepatic Fabp5 expression was significantly decreased in HFHF-fed mice, consistent with the ONT sequencing results. Serum FABP5 concentrations were significantly lower in HFHF-fed mice and patients with MAFLD than in their respective controls. PA treatment induced intracellular lipid accumulation in Huh-7 cells in a concentration-dependent manner. FABP5 overexpression attenuated PA-induced lipid accumulation and increased PPARα expression, together with changes in other genes associated with fatty acid oxidation. CONCLUSION: Hepatic Fabp5 expression and circulating FABP5 concentrations are reduced in experimental and human MAFLD. Restoration of FABP5 attenuates PA-induced lipid accumulation in hepatocyte-derived cells and is accompanied by increased expression of PPARα and other fatty acid oxidation-related genes. These findings suggest that FABP5 is a candidate regulator of hepatic lipid metabolism and warrants further investigation as a potential therapeutic target for MAFLD. Additional inhibition and rescue experiments are required to determine whether PPARα is a necessary mediator of the lipid-lowering effect of FABP5.