Diet induced MASH with Fibrosis is Associated with Skeletal Bone Loss and Proinflammatory Joint Changes in Male Mice

Non alcoholic fatty liver disease (NAFLD) and metabolic syndrome (MetS) have been linked to osteoporosis and osteoarthritis (OA). Many individuals with NAFLD also exhibit MetS, a condition that is now termed metabolic dysfunction associated steatotic liver disease (MASLD). MASLD spans from simple hepatic steatosis to hepatocyte ballooning and inflammation, termed metabolic dysfunction associated steatohepatitis (MASH), which may occur with or without fibrosis.To delineate the contribution of liver injury to skeletal deterioration within the context of MetS, we fed male mice either a high fat, cholesterol, and fructose (HFCF) diet that is able to induce MASH and liver fibrosis associated with moderate obesity, without profound insulin resistance. A nutrient matched diet with high carbohydrates but low in fat, cholesterol, and fructose (LFCF) which induced steatosis in middle aged mice was used as a control. Micro CT analysis of the femur of HFCF fed mice, that developed MASH with fibrosis, revealed significant cortical thinning (reduced bone area and thickness), decreased trabecular thickness, and lower bone mineral density compared to LFCF fed mice, with no liver fibrosis. In the knee joint, MASH with fibrosis was associated with subchondral bone loss, medial cartilage erosion, and elevated chondrocyte expression of iNOS, NLRP3, and B galactosidase. Bulk RNAseq of knee tissue identified 152 differentially expressed genes, interferon related (Oas3, Nlrc5, Zbp1) and stress response (Slc6a4, Alox12, Cirbp, Trpc6, Tap1, Ubash3, Nrg1) pathways were up regulated, while extracellular matrix organization pathways were down regulated. These results highlight mechanistic links between the severity of hepatic injury and skeletal integrity, which may be distinct from the level of systemic metabolic dysfunction, suggesting that targeting shared inflammatory and senescence pathways could preserve bone mass and prevent OA in patients with MASLD or MASH.