Bitter melon (Momordica charantia) triterpenoid extract reduces preadipocyte viability, lipid accumulation and adiponectin expression in 3T3-L1 cells

Bitter melon (Momordica charantia) contains a variety of potentially bioactive compounds which includes two classes of saponins known as cucurbitane and oleanane-type triterpenoids. A bitter melon (BM) extract was investigated for the potential to reduce cell viability, reduce lipid accumulation in differentiating 3T3-L1 cells and affect subsequent adiponectin expression. BM extract contained at least five different triterpenoids and reduced preadipocyte viability with an LC50 concentration after 24 h determined to be 0.402 ± 0.04 mg/mL, 0.314 ± 0.01 mg/mL for 48 h and 0.310 ± 0.01 mg/mL for 72 h. BM treatment increased the release of lactate dehydrogenase (LDH) from cells and significantly (p < 0.05) increased cells in the G2/M while reducing cells in the G1 phase of the cell cycle. BM treatment of 3T3-L1 cells resulted in a decreased in lipid accumulation and significantly (p < 0.05) decreased intracellular triglyceride amount compared to untreated control cells. PPARγ expression was significantly (p < 0.05) down-regulated. Adiponectin expression was significantly (p < 0.05) decreased after 12 and 24 h of treatment and was increased in response to troglitazone, a positive control. BM extract reduced preadipocyte proliferation by a G2/M arrest of the cell cycle and reduced lipid accumulation of the adipocyte.