The Association Between Maternal Serum Osteocalcin And Vitamin D Status And Premature Birth: Based On Guangxi Birth Cohort Study

OBJECTIVE: Preterm birth is the main reason for the increased prevalence and mortality of newborns.The incidence of preterm birth is 5%-12%,which seriously affects the birth quality of the population and aggravates the global social medical burden.Preterm birth as a result of pregnancy combined with a variety of socio-economic and environmental factors,understanding the risk factors of premature birth is a prerequisite for intervention in preterm birth.In recent years,a large number of studies have shown that osteocalcin is not only a marker of bone turnover,but also an endocrine hormone with the function of regulating the metabolism of carbohydrate and lipids.Growing evidence supports the role of osteocalcin(OC)in enhancing the production and secretion of insulin.Meanwhile,OC can bind to GPRC6 a receptor and increase the production of adiponectin in adipocyte,thus enhance the insulin sensitivity.Therefore,OC plays an important role in regulating the metabolism of carbohydrates and lipids in the body.However,maternal serum OC concentrations during pregnancy are lower than non-pregnant.The expression of osteocalcin is not consistent with other bone turnover markers.Therefore osteocalcin is possibly to be involved in the regulation of energy metabolism during pregnancy,leading to poor outcome of pregnancy.OC can be stimulated and regulated by vitamin D.And vitamin D deficiency during pregnancy has received extensive attention from domestic and foreign researchers.We surmised that low vitamin D concentrations increasing the risk of preterm birth through immunity and inflammatory cytokines.The purpose of this study was to investigate the association between maternal serum OC and vitamin D levels and preterm birth.METHODS: A nested case-control study in Guangxi Birth Cohort Study at six cities of Southern China was conducted from July 2015 to September 2015.Among 6,203 recruited women,206 cases of preterm birth were matched to 412 controls on fetus gender,maternal age,gestational age at blood collection,and birthplace.According to the outcome of preterm delivery,participants were divided into preterm delivery group(PTB)and premature ruptured premature birth group(PPROM).Concentrations of maternal serum OC and 25-hydroxyvitamin D [25(OH)D] were measured by automated chemiluminescence system.Conditional logistic regression models were performed to estimate the relationship between serum OC levels and the risk of preterm birth.RESULTS: The highest quartile of OC measured at ≤ 20 weeks was obviously associated with an increased risk of PTB(OR,2.124;95% CI,1.111-4.059)and PPROM(OR,2.732;95% CI,1.029-7.254).Maternal 25(OH)D deficiency(< 50 nmol/L)was not associated with PTB(OR,0.817;95% CI,0.445-1.503)and premature rupture of membranes(OR,1.355;95% CI,0.581-3.161)compared with the sufficient levels(> 75 nmol/L).CONCLUSION: Our study found that the expression of osteocalcin and vitamin D during pregnancy changes with the increase of gestational age.Higher maternal serum OC at 20 gestation weeks or earlier was associated with higher premature birth risk in a Chinese population.It suggested that high levels of osteocalcin during early pregnancy were associated with abnormal energy metabolism and glucose metabolism in pregnant women.