Effects of Bitter Melon (Momordica charantia) Juice Powder on Lipid Metabolism in Rats

We examined the effects of dietary bitter melon juice (BMJ) freeze-dried powder (BMJ-F) on lipid metabolism in rats fed diets with low fat (Experiment 1) as well as of spray-dried powder of a mixture of BMJ and dextrin (1:1, w/w, BMJ-S) on lipid metabolism in rats fed diets with different levels of dietary fats (Experiment 2) and in those fed diets with or without dietary cholesterol (Experiment 3). In Experiment 1, we found that feeding BMJ-F markedly decreased triglyceride (TG) levels in the serum and liver of rats, while the residual fiber fraction lowered cholesterol levels in the serum of these animals. Next, the BMJ and residual fiber fractions thus obtained were freeze dried, powdered (Experiment 2), and evaluated. We confirmed in Experiment 2 that feeding BMJ-S markedly decreased hepatic TG levels, although the reduction was greater in animals fed high fat-containing diets than in those fed low fat-containing diets. In addition, BMJ-S significantly enhanced the serum levels of high-density-lipoprotein cholesterol in animals fed different levels of dietary fat. In Experiment 3, we also examined the effect of dietary BMJS on lipid metabolism in rats fed diets with or without cholesterol, and found that BMJ-S markedly decreased hepatic TG levels in rats fed diets without dietary cholesterol; this was not apparent in animals fed diets with dietary cholesterol. With regard to the mechanism(s) responsible for hepatic triglyceride, we found that feeding BMJ-S considerably upregulated the mRNA expression of the mitochondrial carnitine palmitoylacyltransferase 1 (CPT1) enzyme, but there were no effects on enzyme activity in the synthesis and oxidation of fatty acids. These results suggest that the active component(s) in BMJ may be resistant to hydrothermal treatment and is therefore useful as a functional ingredient in dietary supplements to ameliorate lipid-related metabolic disorders.