Effect Of Propranolol On Preventing Bone Loss And Leptin In Ovariectomized Rats

Aims Osteoporosis is a disorder of the skeleton in which low bone mass and deterioration of bone micro architecture lead to increased bone fragility and fracture risk. It was frequently seen in menopausal women, but the mechanism isn't clear. Several studies have reported that there are interactions between osteoporosis and leptin, and sympathetic nerve system. Our objective is to investigate the effects of propranolol on bone and serum leptin, and Leptin receptor(Ob-R)in hypothalamus, find out the relationship of sympathetic never, leptin, and bone metabolism and discuss mechanism of osteoporosis.Methods Fifty virgin female SD rats of six months old were randomly divided into five groups: (1) Sham; (2) OVX+ 17B-estradial 20ug/kg d-1 SC(O+E); (3) OVX+ Propranolol 8mg/kg d-1 (O+P); (4)O+E+P (5) OVX. The administration of drugs were started one week after operation and lasting for 12 weeks. Serum samples were collected before sacrifice to determine serum leptin level. The lumbar vertebrae and femoral bone were collected for bone mineral density(BMD) and Histomorphometry analysis. Hypothalamus were collected for examine the express of Leptin receptor(Ob-R) by reverse transcriptional polymerase chain reaction(RT-PCR).Results After 12 weeks,the BMD and the Histomorphometry numerical value decreased in OVX rats (O+P group) (P<0.05). The changes of O+E group were similar to O+E group (O+E) and O+E+P group. Serum leptin level increased in O+P group and OVX group, it was similar to O+E group, and O+P group was higher than OVX group in serum leptin(P<0.01), the body weight of O+P group and OVX group are similar. The express of Ob-R and OB-Rb in hypothalamus decreased in OVX rats, treatment of OVX rats with propranolol increased the express of Ob-R in hypothalamus, the express of Ob-Rb had no significant different between OVX group and O+P group. The ratios of Ob-Rb and OB-R in O+P group decreasedsignificantly.Conclusions Propranolol prevented bone loss of ovariectomized rat. Propranolol can increased serum Leptin level and decreased the ratios of Ob-Rb and OB-R in OVX rats. The study demonstrated there are interactions between leptin, and sympathetic nerve system, and bone metabolism. These finding may be one of mechanism of osteoporosis.