Comparing glycine and serine kinetics in adolescent girls and adult women during early and late pregnancy

Abstract

During pregnancy, glycine (Gly) and serine (Ser) becomes more important because they are the primary suppliers of methyl groups for synthesis of fetal DNA and Gly is also required for collagen synthesis. The objective of this study was to measure and compare Gly and Ser kinetics of pregnant adolescent girls and adult women in the first (13.0±0.4 wk of gestation) and third trimesters (28.8±0.4 wk of gestation). Measurements were made in the fasted state by continuous intravenous infusions of 2H2‐Gly and 15N‐Ser in 11 adolescent girls (17.4±0.1 y of age) and in 10 adult women (25.8±0.5 y of age) for 6 h. Adult women Adolescent girls Flux 1st trimester 3rd trimester 1st trimester 3rd trimester μmol/kg/h Gly 156±14 136±9 165±11 142±7* Ser 129±15 119±13 133±11 111±6 Gly→Ser 4.2±0.6 4.2±0.5 4.3±0.5 4.8±0.4 Ser→Gly 62±9 57±7 70±7 54±3* Different vs. trimester 1 value, P<0.05, paired t‐test. Adolescent girls had significantly slower glycine flux and made less glycine from serine in the 3rd trimester (P < 0.05). Baby's birth length was significantly shorter in adolescent girl (P = 0.04), and baby's birth weight was 7% less compared with mean values of adult women. These findings suggest that pregnant adolescents could not maintain Gly production in late pregnancy compared to early pregnancy, which makes their fetus more vulnerable to impaired cartilage synthesis, hence linear growth. Supported by USDA Grant # 58–6250‐6001