Relationship between Insulin Sensitivity and Body Fat Composition, and Leptin Sensitivity in Non-Obese and Overweight/Obese Adults

Abstract

Both insulin and leptin are major contributors for the body energy balance. Obesity is a state of energy imbalance and is also associated with changes in both insulin sensitivity and leptin sensitivity. The aim of this study was to find out the relationship between insulin sensitivity and body fat composition, and leptin sensitivity in non-obese and obese adults. A total of 86 adults participated: 42 non-obese and 44 over-weight/obese. Body fat (BF) percent was determined by skinfold method. Fasting plasma glucose was analyzed by glucose oxidase-phenol and 4 aminophenazone (GOD-PAP) method using spectro-photometer, fasting serum insulin and leptin concentrations by direct sandwich ELISA method and resting energy expenditure (REE) by indirect calorimetry. Leptin sensitivity index and insulin sensitivity were expressed as REE : Leptin ratio and homeostatic model assessment-insulin resistance (HOMA-IR), respectively. It was found that median value of HOMA-IR was significantly higher [2.93 vs 1.72, p<0.01] and leptin sensitivity was significantly lower [116.76 vs 265.66, p<0.001] in the overweight/obese adults than the non-obese adults, indicating that insulin sensitivity and leptin sensitivity were markedly reduced in overweight/obese adults in compare to non-obese adults. There was a moderate degree of positive relationship between HOMA-IR and BF only in the overweight/obese (ρ=0.509, n=44, p<0.001) and all adults (ρ=0.39, n=86, p<0.001). Similarly, a weak negative relationship between leptin sensitivity index and HOMA-IR was found in the overweight/obese (ρ=-0.328, n=44, p<0.05) and all adults (ρ=-0.35, n=86, p<0.01). It can be concluded that the insulin sensitivity was adiposity dependent, but, it did not depend on leptin sensitivity.