Vitamin D metabolism, insulin resistance, TNF-? and IL-6 levels in pubertal obese children

Children must have a healthy nutrition in order to achieve a good physical, cognitive and psychological development. Nowadays, several health issues due to nutrition disorders are seen in children. Obesity, one of these nutrition problems, is increasing in frequency each day and it brings along many other health problems. Studies show insulin resistance and vitamin D deficiency are common in the obese children. Vitamin D does not only act on calcium and bone metabolism but also has effects on insulin secretion. Our study was done in order to investigate the relationship between vitamin D and other parameters such as, insulin resistance, TNF-? and IL-6 levels in pubertal obese children and the effects of weight loss on these parameters.Study was performed between January-June 2009. 84 obese and 28 healthy children were included in this study. The serum levels of fasting blood sugar, insulin, calcium, phosphorous, alkaline phosphatase, 25-OH vitamin D, 1.25(OH)2 vitamin D, PTH, TNF- ?, IL-6 were analyzed. In the insulin resistant group 25-OH vitamin D deficiency was seen in 7.9% of the cases, 25-OH vitamin D insufficiency was seen in 15.8% of the cases where as in the insulin non-resistant group 25-OH vitamin D deficiency was found to be 15.2% and insufficiency was found to be 10.9%. In the control group 25-OH vitamin D deficiency was seen in 3.6% of the cases and insuficiency was seen in 21.4% of the cases. No relationship between insulin resistance and vitamin D was observed in obese cases. TNF- ? levels found to be lower in the obese group while no relationship was detected between vitamin D deficiency and IL-6 levels. Weight loss caused an increase in vitamin D levels, decrease in HOMA-IR levels, a parameter showing insulin resistance and increase in QICKI levels were found. However long term studies are necessary in order to investigate the relationship between vitamin D levels, insulin resistance and cytokine levels.Key words: Obesity, Vitamin D, TNF-?, IL-6