Tilorone attenuates high-fat diet-induced hepatic steatosis by enhancing BMP9-Smad1/5/8 signaling

The prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) is rapidly increasing and is caused by excessive fat deposition in the liver due to non-alcoholic factors. Aging is a major risk factor for the development and progression of MASLD. In this study, we investigated the metabolic effects of tilorone, a synthetic small molecule, in a high-fat diet (HFD) mouse model, with a focus on the liver function and signaling. We demonstrate that tilorone attenuated HFD-induced steatosis by restoring bone morphogenetic protein 9 (BMP9)-Smad1/5/8 signaling and upregulating peroxisome proliferator-activated receptor gamma (PPARγ) expression. Tilorone reduced HFD-induced increases in body weight, adipose tissue and liver weight, and blood glucose levels, and improved glucose tolerance in HFD mice. PET/MRI imaging demonstrated enhanced ¹⁸FDG (¹⁸F-fluoro-2-deoxyglucose) uptake in liver, skeletal muscle, adipose tissue, and myocardium of tilorone-treated HFD animals. Histological analysis showed that tilorone reduced the HFD-induced diffuse, macrovesicular steatosis (S3/3), and machine learning-based image analysis revealed a decrease in lipid droplet size and lipid content. HFD caused the disappearance of liver glycogen, but tilorone increased glycogen levels. High-resolution respirometry indicated that tilorone reduced HFD-induced increases in mitochondrial complex II-linked oxidative phosphorylation and complex IV activity. These findings revealed the beneficial effects of tilorone on HFD and highlight its therapeutic potential in MASLD, particularly given that tilorone is a synthetic small molecule and can be administered orally. Further studies are required to explore its clinical application.