Effects Of Vitamin D On Proliferation, Differentiation Of Human Lipocyte And The Plasma Levels Of Adipoc-Yte Derived Hormone In Obese Children

Recent studies have provided new insights into the function of vitamin D. In addition to the classical effects on regulating metabolism of Calcium and phosphorus, vitamin D has been shown to be closely associated with immune system, cells differentiation and proliferation, and other endocrine glands. Low Vitamin D levels have long been linked to obesity and metabolic syndrome it causes. There is also inference about the connection between Vitamin D and obesity based on the research done showing the effects of vitamin D on preadipocyte proliferation and differentiation of human omental adipose cells. Yet no definite evidence is given about the effects of Vitamin D on human omental adipose cells and hormone level of obese children with Simple obesity.Objective:1.To explore the effects of l,25(OH)2VitD on the proliferation and differentiation of human omental adipose cells and the effects of1,25(OH)2VitD on human secreting of adipocyte adiponectin and leptin in vitro study.2. To detect the differences between the simple obesity group and the healthy control group in1,25(OH)2VitD adiponectin, and leptin, and to investigate effects of Vitamin D on the obese children with simple obesity in serum concentration of1,25(OH)2VitD, adiponectin, leptin and other related targets with prospective intervention study.Methods:1) human omental preadipocytes were isolated and cultured, which became adipocytes during induced differentiation, to observe the effects of1,25(OH)2VitD on preadipocyte proliferation by growth curve and MTT method.2) human omental preadipocyte cells were induced to differentiate by using differentiation medium with insulin, dexamethasone and IBMX to observe the effects of1,25(OH)2VitD on preadipocyte differentiation by quantitative analysis of oil red O dyeing and triglyceride. The expression of adipokine adiponectin and leptin and the effects of1,25(OH)2VitD on the result was detected by immunohistochemisty and Western blot. Clinical study:1) case-control study:46cases of children with simple obesity were gathered from clinic and health screening in the Affiliated Hospital of North China Coal Medical College. Control group consist of children aged between6to14, matched in age and gender with the children in simple obesity group biochemical indicator, the serum concentrations of adiponectin and leptin, and serum concentration of25(OH)VitD, as well as authropometry index were detected between obese children with Simple obesity and control group to evaluate whether25(OH)VitD was interrelated with adiponectin, leptin and obesity2) Prospective intervention study:all obese children received treatment with vitamin D in addition to diet control and exercise for three month. Then comparative analysis was made in the differences in BMI(body mass index), general biochemical indicator and fat source sex hormones such as adiponectin and leptin before and after the treatment.Results:Vitro experiment: The primary cultured human omental preadipocytes differentiated into adipocytes containing reflective lipid drops tested by the oil red O dyeing. Statistics showed that1,25(OH)2VitD had no influence on the number and MTT of omental preadipocytes cultured in vitro(P>0.05) in proliferation. Immunohistochemistry results demonstrated adiponectin was in diffuse expression in cytoplasm. Western blot results showed that the expression level of differentiation group was significantly higher than that of non-differentiation group. While expression level of adiponectin from differentiated adipocyte decreased gradually when treated with10-6-10-41,25(OH)2VitD with statistic significance (P<0.05) Immunohistochemistry results also showed that leptin was mainly expressed in cytoplasm with a little expression of leptin in the undifferentiated group (IOD1867.56). Western blot results demonstrated that10-6-10-41,25(OH)2VitD has inhabitation effect on differentiated adipocyte leptin (P<0.05)Clinical study:Level of BMI and leptin of obese children with simple obesity was higher than that in the healthy control group(P<0.05), whereas level of adiponectin and25(OH)VitD was lower than normal subjects(P<0.05), with statistic significance. But there was no significant difference in blood sugar, cholesterol and triglyceride(P>0.05). Multiple linear regression analysis indicates that correlation factors with BMI were25(OH)VitD adiponectin, and then leptin. BMI and adiponectin were in positive correlation, BMI and leptin,25(OH)VitD negative. After treated with vitamin D for three months,25(OH)VitD, blood sugar, cholesterol and triglyceride of children with simple obesity decreased with no significant difference, which showed vitamin D did not improve indices of blood fat, blood sugar and BMI. While the25(OH)VitD and adiponectin increased obviously and leptin decreased obviously, with significant difference.(P<0.05).Conclusion:Vitamin D has no effects on adipocyte proliferation, but inhibits adipocyte differentiation in suitable density. Vitamin D in certain density can inhibit the expression of adiponectin and leptin in the process of adipocyte differentiation. Obese children with low level of vitamin D are in lipid disorders, which can be improved if treated with proper amount of vitamin D.