Physical Fitness and Its Relationship to Plasma Leptin, Leptin Soluble Receptor, and Free Leptin Index in a Saudi Population: A Comparison Between Diabetic and Non-Diabetic Individuals

BACKGROUND Low physical activity is considered to be a risk factor for type 2 diabetes mellitus (T2DM). One theory suggest that leptin resistance is involved in the pathophysiology of impaired glucose metabolism. In this study we aimed to assess the correlation of physical fitness scores (PFS) with serum total leptin (TL), serum leptin soluble receptor (LSR), and free leptin index (FLI) in a group of Saudi patients with T2DM. MATERIAL AND METHODS This cross-sectional study involved 115 subjects: 52 healthy control subjects and 63 patients with T2DM. All subjects underwent body composition analysis. Blood samples were analyzed for fasting blood glucose (FBG), glycosylated hemoglobin (HbA1c), serum total leptin (TL), and serum leptin soluble receptor (LSR). Based on ideal body composition and our previous studies, physical fitness scores (PFS) were recorded for each subject. RESULTS In patients with T2DM, levels of LSR were positively correlated with PFS (r=0.281, p=0.025), while the levels of TL (r=-0.425, p=0.001) and FLI (r=-0.439, p=0.001) were negatively correlated with PFS. In control subjects, TL and FLI levels were negatively correlated (r=-0.612, p=0.001and r=-0.543, p=0.001 respectively) with PFS. In linear regression analysis, after adjustment for age and BMI, TL and FLI were independent predictors of PFS. CONCLUSIONS Serum TL and FLI were negatively correlated while LSR was positively correlated with PFS in patients with T2DM. Therefore, they may be important biomarkers for predicting the outcomes of physical fitness and exercise programs.