Can Obesity Alone Increase Fasting Serum Insulin, Fasting Serum C-Peptide and Insulin Resistance?

Abstract

Introduction Obesity is becoming an epidemic all over the world, and it is considered to increase fasting serum glucose, serum insulin, insulin resistance (IR) and C-peptide levels. Objectives To compare the fasting serum insulin, fasting serum C-peptide and IR in a selected non-diabetic population of obese and non-obese individuals. Methods This study was conducted at Faculty of Medical Sciences, University of Sri Jayewardenepura as a case control study with non-diabetics (fasting serum glucose < 100 mg/dL, n = 100) aged 20-40 years, consisting obese (BMI ≥ 25 kgm-2, n = 50) and non-obese (BMI < 25 kgm-2, n = 50) individuals. Venous blood sample (4 mL), was obtained. Fasting serum glucose (GOD/POD method), fasting serum insulin (ELISA) insulin resistance (HOMA-IR) and fasting serum (-peptide (ELISA)were assessed. Student t-test was used to compare variables. Results In the obese and non-obese subgroups, the mean fasting serum glucose levels were 79.99± 7.75 mg/dL and 76.9±4.91 mg/dL, the fasting serum insulin levels were 14.36±8.85 µIU/mL and 10.24±5.39 µIU/mL, the fasting serum C-peptide levels were 4.76±1.66 ng/ mL and 4.04 ±1.02 ng/mL and IR values were 2.82±1.86 and 1.91±0.99 respectively. All these biochemical parameters were significantly higher in obese group compared to that of non-obese group (p < 0.05). Conclusions Even though the study population had fasting serum glucose < 100 mg/dL (non-diabetic), their fasting serum insulin, IR and fasting serum C-peptide levels are significantly higher in obese compared to non-obese group. Therefore obesity alone could elevate the above parameters leading to development of metabolic syndrome.