SUN-116 The Restored Activity of Betaine-Homocysteine S-Methyltransferase (BHMT) in Hepatocytes Reduces the Progression of Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD)

Abstract I. Hawro: None. M. Sierra-Cruz: None. S.M. Lee: None. J. Cordoba-Chacon: None. Metabolic dysfunction-associated liver disease (MASLD) is the leading cause of chronic liver disease and has an alarming prevalence in patients with obesity and insulin resistance. MASLD is characterized by the accumulation of triglycerides in hepatocytes that can progress to metabolic dysfunction-associated steatohepatitis (MASH) with inflammation, hepatocyte ballooning, and fibrosis. Interestingly, MASLD is associated with increased plasma homocysteine (Hcy) levels, which correlate with hepatic inflammation and fibrosis. Hcy is primarily produced in the liver in the S-adenosylmethionine-dependent transmethylation pathway (in the methionine cycle). In hepatocytes, Hcy is remethylated to methionine by the betaine-homocysteine S-methyltransferase (BHMT). Our group has reported that hepatocyte peroxisome proliferator-activated receptor γ (PPARγ) expression is associated with the downregulation of hepatic BHMT expression, the accumulation of hepatic Hcy, and the progression of MASH in mice fed a high fat, cholesterol, and fructose (HFCF) diet. In this study, we sought to determine whether the hepatocyte-specific knockout of PPARγ (PpargΛHep) or the restoration of Bhmt expression in hepatocytes (BhmtHep) of mice with pre-established diet-induced MASH improves liver histology and reduces MASLD progression. To this end, adult Pparg-floxed male mice were fed for 20 weeks with an HFCF diet that induces MASH. Then, a single injection of AAV8-TBG-Cre or AAV8-TBG-Bhmt was used to generate PpargΛHep or BhmtHep mice, respectively. We followed the changes in plasma ALT levels for 8 weeks, assessed the progression of MASLD with histological analysis of liver sections, and measured hepatic gene expression and metabolite levels. In control mice, the HFCF diet increased plasma ALT, liver weight, hepatic triglyceride content, and clearly induced MASH, as we previously reported. This was associated with the upregulation of hepatic PPARγ expression, downregulation of BHMT expression, and an increase of the levels of hepatic Hcy. Only 8 weeks of PpargΛHep was enough to reduce plasma ALT, liver weight, hepatic triglyceride content, MASH progression, and the levels of Hcy in the liver. This positive effect of PpargΛHep was associated with increased expression of hepatic BHMT. Interestingly, the restoration of hepatocyte BHMT in the last 8 weeks of diet in BhmtHep mice did not alter plasma ALT. However, it reduced hepatic triglyceride content, the progression of MASH, and the levels of Hcy in the liver. The anti-steatogenic effect of BhmtHep in PPARγ-intact mice was also associated with reduced expression of the steatogenic factor CIDEA, a PPARγ-target gene that is induced by HFCF diet and reduced in PpargΛHep mice. Overall, our results show the protective effect of BHMT in hepatocytes, which likely is endogenously downregulated in a PPARγ-dependent manner in the progression of MASH. Sunday, June 2, 2024