Location: Children's Nutrition Research CenterTitle: In vivo arginine production and nitric oxide synthesis in pregnant Indian women with normal and low body mass indices Author
Submitted to: European Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2009
Publication Date: 8/14/2009
Citation: Kurpad, A.V., Kao, C., Dwarkanath, P., Muthayya, S., Mhaskar, A., Thomas, A., Vaz, M., Jahoor, F. 2009. In vivo arginine production and nitric oxide synthesis in pregnant Indian women with normal and low body mass indices. European Journal of Clinical Nutrition. 63(9):1091-1097. Interpretive Summary: Nitric oxide (NO) is a compound produced by the body that helps to expand blood vessels and lower blood pressure. It is formed from another compound called arginine. NO plays an important role in pregnancy, when there is maternal expansion of blood vessels and increase in blood volume. Because maternal weight affects blood pressure during pregnancy, it may do so by influencing the amount of arginine and NO produced. In this study, we compared the amount of arginine and NO produced by the body in pregnant Indian women with low and normal body mass indices (BMI) during early and mid-pregnancy. We found that the production of arginine was faster in the low BMI women during the first trimester, and there was a trend for higher NO production in the low BMI women during the second trimester. There was an association between the production of arginine and NO and maternal weight. These findings suggest that maternal weight may be affecting the production of NO and may explain how weight influences blood pressure during pregnancy.
Technical Abstract: Nitric oxide (NO) has been proposed as a mediator of vascular expansion during pregnancy. Inability to increase NO synthesis and/or production of its precursor, arginine, may be a contributor to pregnancy-induced hypertension or preeclampsia. Because maternal weight is associated with blood pressure and risk of preeclampsia during pregnancy, it may also influence arginine and/or NO production. The purpose of this study was to determine the in vivo arginine production and NO synthesis rate in pregnant women with normal (n=10) and low (n=10) body mass indices (BMIs). Arginine flux and NO synthesis rate were measured in the postabsorptive state with constant infusions of 15N2-arginine and 13C,2H4-citrulline. Plasma concentrations of arginine and NO metabolites were also measured. Kinetic parameters were correlated to maternal variables, gestational age, birth weight and blood pressure. Endogenous arginine flux was significantly faster in the low-BMI compared with normal-BMI women in the first trimester (63.1 +/- 3.4 vs 50.2 +/- 2.0 umol/kg per h, P<0.01), but not in the second. Plasma NO concentration was higher (44.7 +/- 5.3 vs 30.4 +/- 1.9 umol/l, P=0.03) and its rate of synthesis trended faster in the low-BMI compared with normal-BMI group in the second trimester. Maternal weight and BMI were negatively correlated with arginine flux in both trimesters and NO synthesis in the second trimester. These findings suggest, but do not prove, that maternal BMI may be a factor in the ability to produce NO during pregnancy and may be one way by which BMI influences blood pressure during pregnancy.