The Role of Osteocalcin in Placental Function in Gestational Diabetes Mellitus

Evidence for the role of osteocalcin in glucose metabolism is increasing. The aim of this study was to examine the associations between osteocalcin and gestational diabetes mellitus. Thirteen discovery study subjects and 76 reduplication study subjects were recruited from the Maternal and Child Health Hospital Guangxi Zhuang Autonomous Region from May 2018 to August 2018. Total osteocalcin and biochemical indices of maternal serum and umbilical vein serum were analyzed. Placental tissue samples were used for transcriptome sequencing. For the discovery study subjects, the total osteocalcin concentration in umbilical vein serum was significantly higher than that in maternal serum and umbilical artery serum (55.32 ng/mL ± 17.37 vs. 12.06 ng/mL ± 5.42 [P < 0.001] vs. 38.31 ng/mL ± 11.52 [P < 0.01]), suggesting that trophoblasts may synthesize osteocalcin. In a reduplication subject study, the gestational diabetes mellitus group had lower umbilical vein serum total osteocalcin (51.46 ng/mL ± 24.29 vs. 67.00 ng/mL ± 25.33, P = 0.008), lower adiponectin (1099.72 μg/L ± 102.65 vs. 1235.85 μg/L ± 94.63, P < 0.001). Spearman's correlation analysis showed that umbilical vein serum total osteocalcin levels were closely correlated with leptin (r = -0.456, P = 0.007). A coexpression model of the placental RNA sequence was constructed. Two modules were correlated with osteocalcin, and the Gene ontology pathways of these modules were rich in glucose and lipid metabolism. In conclusion, the placenta may synthesize osteocalcin by itself, and a lower osteocalcin level in umbilical vein serum is associated with gestational diabetes mellitus.