(P11-040-23) Placental mRNA Expression of Calcium Transport-Related Proteins May Differ Between Korean Singletons and Twins

Objectives: The mechanism by which calcium (Ca) is transported to the fetus during pregnancy is unclear, especially in Asians. In addition, twins may have a different mechanism compared to singletons as fetuses may compete for Ca. Therefore, we compared the mRNA expression of Ca transport-related proteins in the placenta of Korean singletons and twins.

Methods: Eighty-four placentas (singleton group [SG] n = 61, twin group [TG] n = 24) were collected after delivery. Real time-PCR was performed for TRPV6, CaBP_28k, PMCA1, and NCX1 mRNA. Ca and phosphorus (P) concentrations in placenta were measured by ICP-OES. Maternal characteristics, maternal nutrient intake during late pregnancy, and birth outcomes of the infant were collected from medical charts and interviews. Spearman’s rank correlation and linear regression was used. Adjustments were made for maternal age, pre-pregnancy BMI, Ca or P intake, birth weight, gestational age, complications, placenta weight, parity, number of fetuses and sex of the infant.

Results: Placental expression of TRPV6 mRNA was positively associated with number of fetuses (β: 0.664, p=0.002). CaBP_28k was positively associated with NCX1 (r: 0.656, p< 0.0001), but negatively associated with PMCA1 (r: –0.372, p< 0.0001) in SG. In contrast, no associations among mRNAs were observed in TG. TG had lower placental P concentrations (means: 7283.7 ± 663.9 ppm, p< 0.0001) and tended to have lower Ca concentrations (means: 1617.1 ± 916.5 ppm, p< 0.054) compared to SG. Placental Ca and P concentrations were not associated with mRNA expression in SG. However, placental Ca concentration was positively associated with NCX1 in TG (β: 0.616, p=0.003). Ca and P intakes during the 3^rd trimester were not associated with mRNA expression in SG and TG.

Conclusions: In conclusion, compared to SG, TG placentas have higher expression of TRPV6 mRNA, lower P concentrations, and a trend toward lower Ca concentration which was positively associated with NCX1. Maternal Ca intakes were not associated with placental Ca concentration in both SG and TG. Placentas of twins may upregulate Ca transport-related mechanisms compared to singletons to efficiently utilize limited sources of calcium.

Funding Sources: This research was supported by the National Research Foundation of Korea.