Location: Children's Nutrition Research CenterTitle: Comparing the in vivo glycine fluxes of adolescent girls and adult women during early and late pregnancy Author
Submitted to: British Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2010
Publication Date: 8/1/2010
Citation: Thame, M., Fletcher, H., Baker, T., Jahoor, F. 2010. Comparing the in vivo glycine fluxes of adolescent girls and adult women during early and late pregnancy. British Journal of Nutrition. 104(4):498-502. Interpretive Summary: Glycine is an amino acid (the basic component of protein) that is used by a fetus to make other amino acids, DNA (the genetic code), and collagen, the building block of skin and organs. Adolescent girls give birth to lower weight babies than adult women. This may be related to a shortage of glycine. In this study, we compared the production of glycine in fasting adolescent girls and adult women in their first and third trimesters of pregnancy. Maternal age was an important factor influencing the production of glycine over the course of pregnancy. Whereas, adult women had an increase in glycine production from the first to third trimesters of pregnancy, adolescent girls actually had a decrease in glycine production. In the third trimester, the adolescent girls also had a slower production of glycine than the adult women. This suggests that adolescent girls who are fasting may not have adequate supply of glycine to meet the needs of the growing fetus, thus leading to lower weight babies compared to adult women.
Technical Abstract: During pregnancy, growth of the fetus depends on an adequate glycine supply because it is needed for synthesis of fetal DNA, collagen, and serine. Since pregnant adolescent girls give birth to lower birth weight babies, it is possible that they do not produce sufficient glycine to meet overall demands as their adult counterparts, especially after an overnight fast. The objective of the study was to measure and compare the flux of glycine, among adolescents and adult women in the first and third trimesters of pregnancy. Glycine flux was measured by continuous intravenous infusion of (2) H (2)-glycine in eight overnight fasted adolescents and in eight adult women in the first and third trimesters of pregnancy. There was a significant interaction between subject's age and time of pregnancy (P = 0.02), as weight-specific glycine flux decreased by 39% from trimesters 1 to 3 in the adolescents, but increased by approximately 5% in the adults. Whole body glycine flux also decreased significantly in the adolescent group (P < 0.05) from trimesters 1 to 3, and this was associated with a significant reduction in plasma glycine concentration. In trimester 3, there was a positive correlation between glycine flux and the subject's age indicating that younger subjects had slower fluxes. These findings suggest that after a brief period of food deprivation, the pregnant adolescent cannot maintain glycine production as her adult counterpart in late pregnancy. It is possible that this inability to maintain endogenous glycine production makes her fetus more vulnerable to impaired growth if food deprivation becomes more frequent or is prolonged.