Trehalose alleviated hepatic cholesterol accumulation via inhibiting transformation from glucose-derived acyl-CoA to cholesterol synthesis in Nile tilapia

Trehalose has been identified as an autophagy enhancer with atheroprotective properties in mammals that reduces cholesterol accumulation in the body. However, such effects have been rarely explored in aquatic animals. This study examined the effects of trehalose supplementation in a high-cholesterol diet on liver cholesterol accumulation and the related mechanisms in Nile tilapia (Oreochromis niloticus). The fish were fed high cholesterol (1.6%) diets supplemented with different levels (0, 1.5, 3 and 4.5%) of trehalose for eight weeks. The results showed that inclusion of 3% trehalose in high-cholesterol diet led to the significant reduction of viscerosomatic index (VSI), hepatosomatic index (HSI) and total and free cholesterol (TC and FC) accumulation in the serum and liver of fish. Moreover, 3% trehalose supplementation decreased serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities, indicating the alleviation of high-cholesterol diet-induced liver impairment. Surprisingly, such beneficial effects did not correlate with autophagy activity since dietary inclusion of 3% trehalose inhibited the expression of autophagy-related genes and proteins (atg5/12, autophagy related gene 5/12; Lc3, microtubule-associated protein 1 light chain 3 and Beclin protein). Also, the same group inhibited the expression of genes related to hepatic cholesterol synthesis, glycogen metabolism, glycolysis, and glucose oxidative phosphorylation. These results indicated that trehalose treatment reduced the capability of glucose catabolism in the liver of high-cholesterol diet-fed fish. In the primary hepatocytes of Nile tilapia, which were cultured in a medium containing high cholesterol concentration, the [1-¹⁴C]-glucose tracking test showed that trehalose treatment resulted in decreased cellular retention of ¹⁴C-glucose and unaltered release of ¹⁴CO₂. Likewise, the trehalose treatment inhibited the expression of genes associated with glucose uptake and catabolism, cholesterol synthesis. Also, the inhibited autophagy activities were found in the primary hepatocytes treated with trehalose. Overall, trehalose treatment alleviated high-cholesterol diet-induced hepatic and serum cholesterol accumulation in Nile tilapia, but such effect was not associated with the autophagy activities. Alternatively, our results suggested that trehalose exerted a cholesterol-lowering effect via inhibiting the transformation from glucose-mediated acyl-CoA to cholesterol synthesis in the liver of fish. This is the first study revealing the cholesterol-lowering function of trehalose in fish and could contribute to developing new strategies for maintaining liver health in fish.