Body mass index correlates positively with insulin resistance and secretion but inversely with insulin sensitivity in gestational diabetes

Aim. To assess fasting C-peptide and insulin indices using homeostatic model assessment (HOMA) in gestational diabetes mellitus (GDM). Methods. Gestational diabetes mellitus (n = 64, age: 27.02 ± 0.53 years, BMI: 26.3 ± 0.5 kg/m 2 ; mean ± SEM) and normal glucose tolerance NGT (n = 56, age: 26.11 ± 0.55 years, BMI: 24.4 ± 0.4 kg/m2; mean ± SEM) screened according to WHO 2013 criteria. Glucose was measured by oxidase method whereas fasting insulin and C-peptide by ELISA. HOMA-IR, HOMA-B and HOMA-%S were calculated. Results. C-peptide was found higher in GDM compared to NGT without any significant difference (p = 0.465). Fasting insulin (p = 0.063) and HOMA-IR (p < 0.001) were significantly higher while HOMA-B (p = 0.015) and HOMA-%S (p = 0.012) were significantly lower in GDM than those of NGT. BMI, bad obstetric history, multiparity and blood glucose were higher (p ≤ 0.05) in GDM while age, duration of gestation, family history of DM did not differ (p = NS). C-peptide (0.185 ± 0.06 vs 0.331 ± 0.44; p < 0.05), fasting insulin (4.88 ± 0.74 vs 10.37 ± 0.74; p < 0.01) and HOMA-IR (1.04 ± 0.14 vs 2.48 ± 0.18; p < 0.011) as well as HOMA-B were found lower in GDM having BMI < 23 kg/m2 than those of GDM with BMI ≥ 23. Conversely, HOMA-%S (115.52 ± 14.63 vs 50.62 ± 3.39; p < 0.011) was higher in the subgroup with BMI < 23 than the rest. Fasting blood glucose (FBG) (p < 0.01) and fasting insulin (p < 0.05) were independent predictors for GDM. Conclusions. Fasting C-peptide do not differ between GDM and NGT. BMI was positively related with resistance and secretion of insulin but inversely with sensitivity. HOMA model analyses revealed decreased insulin sensitivity and secretory capacity in GDM than NGT.