Effects of Enzymatic Hydrolysates from Protaetia brevitarsis Larvae on Glucose and Lipid Metabolism in High-Fat Diet-Fed Mice

There have been few studies to date on physiologically active peptides derived from Protaetia brevitarsis larvae (PBL). This study aimed to examine the effects of PBL enzyme hydrolysates on glucose and lipid metabolism in mice fed a high-fat diet. Four-week-old male C57BL/6J mice were acclimated for one week. They were then divided into three groups: the normal fat diet-fed group (ND; n = 5), the high-fat diet-fed group (HD; n = 6), and the high-fat diet-fed group that was orally administered PBL enzyme hydrolysate (200 mg/kg/day, 7 times/week) (HDP; n = 6). After 7 weeks on the experimental diet, dietary intake decreased significantly in the HD group compared with the ND group, but it was not significant in the HDP group. Low-density lipoprotein cholesterol (LDL-C) and triglyceride (TG) were significantly increased in the HD group compared with the ND group but were not reduced in the HDP group. In the oral glucose tolerance test (OGTT) glucose levels at 30 minutes were significantly higher in the HD group than in the ND group and tended to decrease in the HDP group. Tumor necrosis factor-alpha ( TNF-α) mRNA expression was significantly increased in the HD group compared with the ND group, but tended to decrease in the HDP group compared with the HD group. In conclusion, in mice fed a high-fat diet, PBL enzyme hydrolysate inhibited the rise in blood glucose during the initial 30 minutes of OGTT and showed a tendency to lower expression of TNF-α genes in the liver tissue. Further studies are needed to clarify the concentration-specific and long-term effects of PBL enzyme hydrolysate on metabolic improvement in mice fed a high-fat diet.