Hydroxysteroid 17-beta dehydrogenase 13(Hsd17b13)knockdown attenuates liver steatosis in high-fat diet obese mice

Hydroxysteroid 17-beta dehydrogenase 13 ( HSD17B13 ) loss-of-function gene variants are associated with decreased risk of ‘metabolic dysfunction-associated steatotic liver disease’ (MASLD). Our RNA-seq analysis of steatotic liver from obese mice -/+ Fenretinide treatment identified major beneficial effects of Fenretinide on hepatic gene expression including Hsd17b13 . We sought to determine the relationship between Hsd17b13 expression and MASLD and to validate it as a therapeutic target by liver-specific knockdown. Hsd17b13 expression, which is unique to hepatocytes and associated with the lipid-droplet, was elevated in multiple models of MASLD and normalised with prevention of obesity and steatotic liver. Direct, liver- specific, shRNA-mediated knockdown of Hsd17b13 ( shHsd17b13 ) in high-fat diet (HFD)-obese mice, markedly improved hepatic steatosis with no effect on body weight, adiposity or glycaemia. shHsd17b13 decreased elevated serum ALT, serum FGF21 levels and markers of liver fibrosis e.g. Timp2 . shHsd17b13 knockdown in HFD-obese mice and Hsd17b13 overexpression in cells reciprocally regulated expression of lipid metabolism genes e.g. Cd36 . Global lipidomic analysis of liver tissue revealed a major decrease in diacylglycerols (e.g. DAG 34:3) with shHsd17b13 and an increase in phosphatidylcholines containing polyunsaturated fatty acids (PUFA) e.g. PC 34:3 and PC 42:10. Expression of key genes involved in phospholipid and PUFA metabolism e.g. Cept1 , were also reciprocally regulated suggesting a potential mechanism of Hsd17b13 biological function and role in MASLD. In conclusion, Hsd17b13 knockdown in HFD-obese adult mice was able to alleviate MASLD via regulation of fatty acid and phospholipid metabolism, thereby confirming HSD17B13 as a genuine therapeutic target for MASLD and development of liver fibrosis. KEY POINTS HSD17B13 loss-of-function gene variants are associated with decreased risk of metabolic dysfunction-associated (MA) steatotic liver disease and steatohepatitis (MASLD and MASH). RNA-seq analysis of steatotic liver identified beneficial effects of Fenretinide on hepatic gene expression including downregulation of Hsd17b13 . Liver-specific shRNA knockdown of Hsd17b13 in obese mice markedly improved hepatic steatosis and markers of liver health e.g. serum ALT, serum Fgf21 levels. Hsd17b13 influenced expression of lipid/phospholipid metabolism genes e.g. Cd36 and Cept1 and phosphatidylcholines PC 34:3 and PC 42:10. Our study suggests a mechanism of HSD17B13’s biological function and the strong rationale behind targeting HSD17B13 for MASLD/MASH.