The l-arginine/nitric oxide pathway is impaired in overweight/obese pregnant women

Objective: To evaluate the l-arginine/NO system and its role in insulin signaling and endothelial function during the pregnancy of women of different BMI categories.

Study design: Twelve women with BMI⩾25 were compared with 10 normal-weight women in a fasting condition after the infusion of l-arginine (20g in 3h) and after the evaluation of the flow-mediated vasodilation (FMD) of the brachial artery between the 9th-12th and 24th-27th weeks. Blood samples for insulin and nitrite/nitrate (NOx) were collected at baseline and after 1, 2 and 3h after initiating the infusion.

Results: In both trimesters, the baseline NOx levels were similar among groups. In the 1st trimester of the lean women, there was a NOx increase in response to l-Arg (AUC: 1328; 3, 3173), which had increased by the 2nd trimester (AUC: 3884; 1905, 7686); in overweight/obese women, no responses to l-Arg were found in the 1st or 2nd trimesters. In the 1st trimester, the insulin levels were significantly reduced in both groups after l-Arg infusion. Although the insulin levels in all BMI categories were higher in the 2nd trimester, such levels during weeks 24-27 were suppressed only in normal-weight women after l-Arg infusion. The FMD was higher during both trimesters in the lean controls and was impaired in the overweight/obese subjects.

Conclusions: NO availability is impaired in overweight/obese women during pregnancy, which affects endothelial functioning and interferes with insulin regulation. These mechanisms could be involved in the development of hypertensive disorders and glucose intolerance in this population.