Relationship of adipokine to insulin sensitivity and glycemic regulation in obese women--the effect of body weight reduction by caloric restriction.

BACKGROUND/AIM: Visceral fat is highly active metabolic and endocrine tissue which secretes many adipokines that act both on local and systemic level. It is believed that adipokines and "low-grade inflammatory state" represent a potential link between obesity, metabolic syndrome, insulin resistance and cardiovascular disease. Leptin and adiponectin are considered to be the most important adipokines with the potential metabolic and cardiovascular effects. Body weight loss improves insulin sensitivity and decreases risk for most complications associated with obesity. The aim of this study was to determine the effects of moderate loss of body weight on the level of leptin and adiponectin, insulin sensitivity and abnormalities of glycoregulation in obese women, to determine whether and to what extent the secretory products of adipose tissue, leptin and adiponectin contribute to insulin sensitivity, as well as to assess their relationship and influence on glycemia and insulinemia during the period of losing body weight using a calorie restricted diet.

METHODS

The study involved 90 obese female subjects (BMI > or = 30 kg/m2) of different age with weight loss no less than 5% during a six-month period by application of restricted dietary regime. The calorie range was between 1,100-1,350 kcal. Serum levels of leptin and adiponectin, fasting glucose, fasting insulinemia, and Homeostasis Model Assessment of Insulin Resistance (HOMA-R) index were determined in all the subjects initially and after weight reduction. The presence of glycemic disorders was assessed on the basis of oral glucose tolerance test--OGTT.

RESULTS

Applying a 6-month restrictive dietary regime the subjects achieved an average weight loss of 8.73 +/- 1.98 kg and 8.64 +/- 1.96%, which led to the reduction of fasting glycemia, fasting insulinemia and HOMA-R index at the maximum level of statistical significance (p < 0.001). The achieved reduction led to a statistically significant decrease of leptin level and increase of adiponectin level (p < 0.001). The correction of the established pre-diabetic disorders of glycoregulation was not statistically significant. There was a statistically significant correlation between the anthropometric parameters, leptin, adiponectin, fasting glycemia, fasting insulinemia and HOMA-R index. There was a positive correlation between leptin, fasting insulinemia and HOMA-R, as well as a statistically significant negative correlation between adiponectin, fasting insulinemia and HOMA-R index (p < 0.01).

CONCLUSION

Body weight increase and central fat accumulation lead to changes in serum levels of leptin and adiponectin, reduction of insulin sensitivity and development of glycemic dysregulation. Secretory products of adipose tissue, leptin and adiponectin contribute to the genesis of these disorders. The obtained results show that the effect of adiponectin on insulin sensitivity is more significant. The analysis of the effects of weight loss on the investigated parameters shows that moderate weight reduction by restrictive dietary regime lead to changes of investigated parameters at the maximum level of statistical significance. Such results emphasize the importance of weight reduction in obese persons, as well as the need for consistent implementation of restricted dietary regime in the process of treatment of obesity.