Evaluation of Insulin Resistance in Type 2 Diabetic Nigerians

Background: The link between Insulin Resistance (IR) and type 2 Diabetes Mellitus (T2DM) has been well recognized for well over half a century. Not only is it the most powerful predictor of future development of type 2 diabetes mellitus, it is also a therapeutic target once hyperglycaemia is present. The current study seeks to evaluate Insulin Resistance in type 2 Diabetic subjects and proffer a reference range for insulin resistance in the ABUTH, Zaria area. Materials and Methods: Serum insulin resistance, insulin, lipids, fasting plasma glucose, glycated haemoglobin and anthropometric parameters were measured in 180 type 2 diabetic and 180 control subjects. Insulin resistance was calculated using the Homeostasis Model Assessment (HOMA) method. Serum insulin was measured using the ELISA method while spectrophotometric methods were used for blood glucose, glycated haemoglobin and serum lipids. The results were analysed statistically using the two-tailed student’s t-test and the one way analysis of variance (ANOVA). Results: Mean serum insulin resistance levels were significantly higher in the type 2 diabetic group than in the control group (P < 0.05). Mean FPG, HBA1C and serum insulin levels were also significantly higher in the diabetic group than in the control group (P < 0.05). Mean TC, LDL-C and TC/HDL-C levels were higher but not significantly in the diabetics than in the controls (P > 0.05). Mean TG level was significantly higher in the diabetic group than in the control group (P < 0.05) while mean HDL-C level was nonsignificantly lower in the diabetic group than in the control group (P > 0.05). Mean values for anthropometric parameters (BMI and SBP) were significantly higher in the type 2 diabetic subjects than in the control subjects (P < 0.05) while mean DBP was higher in the diabetic group but not significantly (P > 0.05). A significant positive correlation was observed between insulin resistance and insulin (r = 0.817, P < 0.000), FPG (r = 0.560, P < 0.000) and HBA1c (r = 0.275, P < 0.000) in the entire study, but only with FPG (r =0.482, P <0.000) and insulin (r = 0.803, P < 0.000) in the diabetic group. The results of the current study show an increased insulin resistance level in type 2 diabetic subjects compared to the control group and reference range for insulin resistance was obtained as 0.51 – 2.27. Conclusion In view of the importance of insulin resistance as a powerful predictor of future T2DM, a periodic measurement of insulin resistance is suggested for all.