Effects Of Mechanical Loading And Hormones Of Bone Metabolism On Exercise Promoting Bone Formation

As a serious health problem, patients with osteoporosis are bearing pains and a huge financial burden, which influent the quality of their life. Exercise is an effective way in preventing and treating osteoporosis. It can regulate bone remobilization and bone mass accumulation. There are many comparative studies about what kinds of exercise mode or exercise intensity can improve bone density and prevent osteoporosis. But these conclusions have huge difference in these studies. The explanations for the differences are more contradictious. This shows that our knowledge is not enough for understanding the underlying causes of exercise regulating bone metabolism. In the influence of exercise promoting bone formation, whether the mechanical forces from exercise or the exercise-induced endocrine changes plays the major role? Or the synergistic effect of both? Whether the improvement of glucose metabolism can promote the increase of bone formation and the improvement of bone quality or not? We start our research with the curiosity for these questions.ObjectiveFirst study:(1) Compare and evaluate effects of mechanical forces and anabolic metabolism hormone and catabolism hormone on biochemical index of bone metabolism and osteogenic index; (2) Evaluate the effect of intermittent exercise on Bone metabolism biochemical index and osteogenic index.Second study:(1) Compare and evaluate the influence of different exercise timing and mode on biochemical index of bone metabolism and osteogenic index; (2) Compare and evaluate the influence of different exercise timing and mode on mechanical forces and its osteogenesis response; (3) Compare and evaluate the influence of different exercise timing and mode on hormones and their osteogenesis response; (4) Compare and evaluate the influence of different exercise timing and mode on hormones regulating glucose metabolism and their osteogenesis response. (5) Compare and evaluate osteogenesis response between Ground reactive forces and hormones.MethodsFirst study:According our research goal and literature, we designed two kinds of exercise mode:downhill exercise with lower exercise intensity and uphill exercise with higher exercise intensity. Then according the difference on intermission,40min exercise has been finished in a single bout or two bouts spaceing 40min exercise for 7h. So we have five different exercise condition:sedentary condition (SED),40 minutes of uphill(40U) or downhill(40D) exercise, and 20-minute bouts (20/20) of uphill(20/20U) or downhill(20/20D) exercise separated by 7 h, total 5 study condition.40 healthy postmenopausal women were randomly assigned to one of five study condition.Second study:According our last study and literature, Four exercise experimental trials will apply two independent variables, exercise mode and exercise timng, in orthogonal direction for our research goal. So we have five experiment condition:sedentary(SED), uphill exercise before meal(UBM), downhill exercise before meal(DBM), uphill exercise after meal(UAM), downhill exercise after meal(DAM). To minimize the number of subjects needed to achieve statistical power (0.8 power at alpha p<0.05), we recruit 15 postmenopausal women with typeⅡdiabetes mellitus. These subjects will be randomly assigned to two trials carried out one week apart. The two trials will consist of different combinations of five trial.Peak forces will be measured with a Novel Pedar system; CICP and CTX will be measured with enzymatic immunoassays; GH, PTH and OC will be measured by Luminex(?) xMAP(?) technology; Insulin, leptin and cortisol will be measured by radioactive immune technology; Serum calcium and Glucose will be measured by automatic biochemical analyzer.ResultFirst study:(1) Compare with 40U group and 20/20U group with medium exercise intensity,40D group and 20/20D group generate more ground reactive forces(GRFs) and induced secreting less anabolic hormones with lower exercise intensity. But 40U group and 20/20U group generate lesser GRFs, on the contrary, higher GH and PTH (2) Compare bone formation marker—ICP and osteogenesis index—ICP/CTX ratio,40D group increased serum CICP and CICP/CTX ratio, and have significant difference with SED,40U and 20/20U group(P<0.01); (3) Increased serum CICP and the osteogenic CICP/CTX ratio were associated with higher GRFs but not with GH and PTH increases.Second study:(1) Downhill exercise with lower exercise intensity generate Significantly greater than uphill exercise with high exercise intensity; (2) Exercise before meal induce the secretion of bone anabolic hormones and insulin increase. Especially, UBM group have significant difference with other groups; (3) Compare bone formation marker—CICP and osteogenesis index—CICP/CTX ratio, DAM group increased serum CICP and CICP/CTX ratio, and have significant difference with SED and DBM group (P<0.01). Compare osteogenesis index of 12:00, DAM group have significant difference with SED, UBM, DBM and UAM group; (4) Increased serum CICP and the osteogenic CICP/CTX ratio were associated with higher GRFs and insulin increase but not with GH increases, a negative correlation with PTH increase; CICP、CTX、OC and glucose have negative correlation with leptin.ConclusionFirst study:(1) Osteogenic index is more responsive to mechanical stimulation than to anabolic hormones, (2) Osteogenic index may be suppressed by increased exercise-associated cortisol release; and (3) A 40-minute consolidated bout of downhill exercise is more osteogenic than two 20-minute bouts of exercise separated by seven hours.Second study:(1) Downhill exercise after meal can induce more increase on osteogenic responses. There are two reason:on one hand, generate higher GRFs relative to uphill exercise before meal and uphill exercise after meal; on the other hand, osteogenic response of exercise coincide with the influence of biological clock on bone metabolism. So this kind ogf exercise mode can increase osteogenic responses. (2) Downhill exercise can generate more GRFs than uphill exercise. GRFs are significantly associated with osteogenic index, and play the important role on bone formation and improve bone metabolism; (3)GH, PTH and insulin more significantly increase in uphill exercise before meal than downhill exercise before meal and uphill exercise after meal. This result induces a little osteogenic response without the effect of GRFs, and increase bone formation and improve bone metabolism. (4) Cortisol generat interference effect on osteogenic response of GRFs. Although downhill exercise before meal can generat higher GRFs, exercise in fasting induce cortisol increase. So this kind of exercise mode didn’t increase osteogenic response.