Effects of Toona sinensis leaf extract on lipolysis in differentiated 3T3-L1 adipocytes.

The effect of substances extracted from Toona sinensis leaves with 50% alcohol solution on lipolysis was investigated in cultured 3T3-L1 differentiated adipocytes. The amount of glycerol released from cells into culture medium was used to measure lipolysis activity. Glycerol release was increased by Toona sinensis leaf extract in a dose-dependent and time-dependent manner. Following treatment of 3T3-L1 adipocyte cells with various concentrations of Toona sinensis leaf extract (0.001, 0.01, and 0.1 mg/mL) for 6 hours, the amounts of glycerol released from 3T3-L1 cells increased from a control value of 99 nmol/mg protein to 127, 144, and 154 nmol/mg protein, respectively. The lipolytic effect of Toona sinensis leaf extract was not inhibited by pretreatment of cells with cycloheximide, econazole, baicalein, or indomethacin. However, the lipolytic activity induced by Toona sinensis leaf extract was diminished by dibutyryl cyclic adenosine-5'-monophosphate (dibutyryl cAMP) and the protein kinase C inhibitor calphostin C. These results indicate that the lipolytic effect induced by Toona sinensis leaf substances may be involved in the protein kinase C pathway and may be down-regulated by cAMP.