Development of a silkworms-based evaluation system for the extracts and compounds for their obesity and lipid metabolism improving activity.

As lifestyle-related diseases like obesity, dyslipidemia, and non-alcoholic fatty liver disease are increasing globally, the demand for developing therapeutic agents and health foods remains high. However, there is a growing concern worldwide regarding the use of animals for biological testing. Herein, we developed a method using the silkworm, Bombyx mori, to evaluate the effects of compounds on improving obesity and lipid metabolism. A silkworm obesity and lipid metabolism disorder (SOLD) model, fed a 10% glucose diet for 72 h showed increased fat body weight and accumulation of neutral fat in the hemolymph and fat body. Administration of fenofibrate reduced neutral fat levels in the hemolymph, and epigallocatechin gallate reduced neutral fat levels in the hemolymph and fat body. Silkworms with improved lipid metabolism, exhibited activation of lipoprotein lipase in muscle tissue, and decreased activities of acetyl-CoA carboxylase, and activation of AMPK in the fat body. Furthermore, enhanced fatty acid beta-oxidation contributed to the promotion of lipolysis. These effects and mechanisms of action observed in silkworms are similar to those found in mammals. These results demonstrate the usefulness of the evaluation system in screening materials for their anti-obesity and lipid metabolism improvement effects using the SOLD model.