Effects of Yam and Diosgenin on Calpain Systems in Skeletal Muscle of Ovariectomized Rats

Abstract

Yam or diosgenin (extracted from the root of wild yam) is traditionally used for hormone replacement in menopausal women. Calpains are crucially related to the degradation of myofibrillar proteins in skeletal muscle. This study aimed to investigate the effects of yam and diosgenin on the calpain isoform expression in ovariectomized rats, a model of menopausal status. Female rats were divided into: (1) controls; (2) ovariectomized rats; (3) ovariectomized rats receiving yam (250, 750, 1,500 mg/kg/day); (4) ovariectomized rats receiving diosgenin (10, 50, 100 mg/kg/day). Yam and diosgenin were administered for 8 weeks. The expression of mu- and m-calpain in skeletal muscles was determined by reverse transcriptase-polymerase chain reaction. The mu-calpain/beta-actin and m-calpain/beta-actin ratios in the control group (0.9 and 1.09, respectively) were significantly higher than those in the ovariectomized group (0.58 and 0.72, respectively). In the yam group, the expression of mu- and m-calpain was lowest in the ovariectomized group receiving no supplementation and lower in the 250 mg group compared with the 750 and 1,500 mg groups (for 0, 250, 750 and 1,500 mg dosage groups, mu-calpain, 0.58, 0.88, 1.24 and 1.13, respectively; m-calpain, 0.72, 1.02, 1.38 and 1.47, respectively). In contrast, there were no significant differences in the expression of mu- and m-calpain mRNAs among the different diosgenin dosage groups (for 0, 10, 50 and 100 mg of diosgenin, mu-calpain, 0.58, 0.56, 0.62 and 0.58, respectively; m-calpain, 0.72, 0.58, 0.71 and 0.54, respectively). Decreased expression of mu- or m-calpain was observed in the ovariectomized group compared with the normal controls. Yam, but not its extract (diosgenin), is associated with the regulation of calpain isoforms in ovariectomized rats. Adequate yam supplements might improve the muscular calpain-related physiopathology associated with menopausal status.