Bitter melon extracts suppressed differentiation and triglyceride content of 3T3-L1 adipocytes

Abstract

Bitter melon (BM; Momordica charantia) supplementation slows weight gain and tissue fat accumulation in fat diet-induced obese rat. Liver and muscle carnitine palmitoyl transferase-I expression was enhanced in BM rats, suggesting increased lipid oxidation. This study was designed to determine if extracts from BM juice can suppress triglyceride (TG) content in the 3T3-L1 cell line. 3T3-L1 pre-adipocytes were induced to differentiate in the presence or absence of an ethanol-water extract of BM juice. The latter was obtained by stepwise gradient elution of an organic extract of BM juice. Two fractions (eluted by 10% & 30% ethanol respectively and then freeze-dried; F2 at 350μg/mL & F3 at 50μg/mL) were found to reduce TG content on day 10 (p<0.01, F3) & day 12 (p<0.01, both); and GPDH activity on day 10 & 12 (p<0.01, both) of a 12-day study. Two-way ANOVA indicated reduced mRNA expression of fatty acid synthase (p<0.001), acetyl CoA carboxylase 1 (p<0.01) and Glut-4 (p<0.01) in BM-treated adipocytes. With F3, these effects primarily occurred between days 8–10. Downregulation of PPARγ (p<0.001) and SREBP-1c (p<0.001) mRNA expression was observed in F3-treated cells on day 12. The data suggest that bioactive ingredient(s) in BM may suppress TG synthesis in 3T3-L1 cells through suppressing the expression of certain lipogenic genes and transcription factors. (Supported by the Faculty Development Fund, HKU)