Association of osteocalcin, insulin resistance and oxidative stress during noncomplicated pregnancy

Background: The aim of this study was to explore longitudinal changes of serum osteocalcin during normal, uncomplicated pregnancy and after delivery, and its correlations with parameters of glucose homeostasis, lipid status, and oxidative status in late pregnancy. Methods: Osteocalcin, glucose, insulin, lipid status parameters, total oxidative status (TOS), and total antioxidant capacity (TAC) were measured in sera of 38 healthy pregnant women. The sera were collected at the midpoint of the 1st, in the 2nd and 3rd trimester, and after delivery. Homeostatic model assessment (HOMA) indices were calculated and used as surrogate markers of insulin resistance. Results: Repeated measures analysis of variance showed a progressive increase in total cholesterol, triglycerides, and low density lipoprotein (LDL)-cholesterol, with a postpartum decrease. High density lipoprotein (HDL)-cholesterol increased in the 2nd trimester and decreased after delivery. Total oxidative status (TOS) increased significantly in the 3rd trimester (p < 0.001). TAC showed a significant increase after delivery (p < 0.05). Insulin showed a significant increase in the 3rd trimester (p < 0.05). Homeostatic model assessment (HOMA)-%B increased significantly in the 3rd trimester (p < 0.001). Osteocalcin showed a decrease in the 2nd trimester, and a marked increase in the 3rd - trimester and postpartum (p < 0.001). Osteocalcin was significantly positively correlated with BMI, insulin, HOMA of insulin resistance (HOMA-IR), HOMA-%B, TAC (p < 0.05), triglycerides and uric acid (p < 0.001). Multiple regression analysis showed that TAC is independently associated with osteocalcin level during 3rd trimester (p < 0.05). Conclusions: We observed the changes in pregnancy that may lead towards atherogenic, prooxidant and insulin resistant state, which are possibly counterbalanced by various protective systems, one of which might be osteocalcin.