Abstract
Leptin is known to regulate appetite and energy expenditure, Which may have a powerful influence on bone. There is some conflicting evidence that leptin may decrease bone formation via a central nervous system and may stimulate both bone formation and bone resorption via direct peripheral effect. We studied the relationship of effect of leptin and other factors, serum estrogen and treadmill running, on bone. Leptin receptor deficient Zucker (fa/fa) rats and lean controls were used.Twenty eight female Zucker (fa/fa) rats and twenty eight lean controls were assigned to four groups respectively: sham operated group, sham operated and exercise group. Ovariectomized group, ovariectomized and exercise group. Exercise groups were assigned to treadmill running (20 m/min), 30 min/day, 5 days/week, for 8 weeks. Right femur was used to measure bone strength determined by the three-point bending test. Bone mineral density of left femur was measured by dual energy X-ray system and that of tibia was measured by peripheral quantitative computed tomography (pQCT). In lean controls, especially, ovariectomized group, exercise increase bone strength. However, in Zucker (fa/fa) rat, bone strength was decreased in exercize group. Differences were not observed among the groups in BMD. We observed positive effect of exercise on bone in existence leptin signal, however, in Zucker (fa/fa) rats, exercise did not influence on bone. These result suggested that leptin could play important part in bone metabolism in rats. [Jpn J Physiol 54 Suppl:S252 (2004)]
