Relationship of Il-5 with Th1 and Th2 Cytokines in Individuals with or without Type-2 Diabetes

Purpose: Changes in plasma levels of T-cell cytokines may result in inflammatory disorders, including metabolic disease. The changes in circulatory IL-5 levels in obesity and type-2 diabetes (T2D) and their relationship with major Th1 and Th2 cytokines are poorly understood. The aim of this study was to determine obesity/T2D-associated perturbation in plasma IL-5 levels and investigates its association with Th1/Th2 cytokine levels in the circulation. Experiment: Plasma samples were collected from 43 diabetic and 22 non-diabetic individuals selected over a wide range of body mass index (BMI), and further classified as obese (BMI=31-40 kg/cm2), overweight (BMI=26-30 kg/cm2), and lean (BMI=18-25 kg/cm2). Clinical metabolic parameters were determined using commercial kits. IL-5 and Th1/ Th2 cytokines were measured using Luminex X-MAP® technology. The data were compared using unpaired t-test and dependence between two variables was assessed by Pearson’s correlation coefficient (r). Results: In the diabetic cohort, circulatory IL-5 levels were significantly lower as compared to non-diabetic counterparts (Diabetic: 1.55 ± 0.23 pg/ml; Non diabetic: 3.31 ± 0.49 pg/ml; P=0.0004). Furthermore, we found that in diabetic individuals, plasma IL-5 levels were found to be significantly higher (P=0.036) in obese group (1.488 ± 0.21 pg/ ml) as compared with lean+overweight group (1.03 ± 0.13 pg/ml). In diabetic individuals, IL-5 levels correlated positively with Th1/Th2 cytokines including IL-12 (r=0.68, P=0.002), IL-3 (r=0.97, p=0.001) and G-CSF (r=0.57, p=0.0001). While in non-diabetic individuals, IL-5 levels correlated positively with IL-2 (r=0.83, P=0.0005), IL-12 (r=0.66, P=0.0014), IL-3 (r=0.82, P=0.0054), IL-6 (r=0.802, P=0.009), IL-9 (r=0.88, P=0.0075), IL-10 (r=0.787, P=0.008), IL-13 (r=0.84, P=0.0002), and G-CSF (r=0.82, P=0.0001). Moreover, plasma IL-5 levels in diabetic individuals associated positively with clinical metabolic indicators including BMI (r=0.54, P=0.0001), fasting blood glucose (r=0.29, P=0.05) and glycated hemoglobin (r=0.32, P=0.034). Conclusion: The changes in circulatory IL-5 levels show differential association with Th1/Th2 cytokines in diabetic and non-diabetic individuals which may have immunometabolic significance.