Vitamin D and Insulin resistance in gestational diabetes mellitus

This study was designed to demonstrate the relationship between 25-hydroxy vitamin D (25(OH)D) levels and insulin resistance (IR) in normal pregnancy and in gestational diabetes mellitus (GDM). The study included 103 pregnant women classified into two main groups: normal pregnant (n= 48) and GDM (n= 55). Further classification for each group was carried out based on 25(OH)D status (deficient, insufficient and sufficient). Serum were used for determination of fasting blood glucose (FBG), fasting insulin (FI), C-peptide, cholesterol, triacylglycerol (TAG), total Ca, 25(OH)D and parathyroid hormone (PTH). IR markers were calculated including glucose/insulin ratio (G/I), fasting insulin resistance index (FIRI), and homeostasis model assessment of insulin resistance (HOMA-IR), Log HOMA-IR, HOMAA1-% B, and HOMA β cell. Results indicated significantly increased FBG, FI, C-peptide, FIRI, HOMA-IR, Log HOMA-IR and HOMA β cell, cholesterol and TAG in GDM compared to control group. Mean values of 25(OH)D did not show significant variations between the two groups. In control group, no significant correlations were obtained between 25(OH)D and any tested parameters, however, in GDM 25(OH)D showed significant correlations with FBG and Log HOMA-IR. Results also revealed increased prevalence of 25(OH)D deficiency among healthy pregnancy and GDM (~69 and 67%, respectively) groups. Furthermore, deficient GDM had significantly higher FBG, IR markers, cholesterol and TAG compared to matched deficient normal pregnancy. Improving 25(OH)D status had significantly normalizes IR and lipid parameters, indicating that 25(OH)D may be associated with elevated IR that accompany GDM. Key words: Gestational diabetes mellitus, vitamin D, insulin resistance, calcium homeostasis.