The relationship of long-chain polyunsaturated fatty acid status with blood pressure in pregnant African women : the NuPED study

Abstract

Introduction - Globally, hypertensive disorders affect 10% of pregnancies and are the most common risk factors for maternal and perinatal morbidity and mortality. Between 2011 and 2013, 14.8 % of maternal mortalities were associated with hypertensive disorders in South Africa. Adequate intake and status of n-3 long chain polyunsaturated fatty acids (LCPUFA) have been linked to improved endothelial function and reduced blood pressure. However, the South African longitudinal Prospective Urban Rural Epidemiology (PURE) study has shown a positive association between plasma n-3 LCPUFA and hypertension and a negative association between n-6 LCPUFA and hypertension. In addition, in South Africa, pregnant women are supplemented routinely with 60 mg/d of elemental iron to prevent iron deficiency. This supplementation programme may lead to oxidative stress and increased inflammation, especially in women with sufficient iron status, increasing their risk to develop gestational hypertension. This study assessed the relationship of n-3 and n-6 LCPUFA status with blood pressure in pregnant African women receiving routine iron supplementation. Methods - This was a longitudinal analysis where 250 pregnant women were recruited at <18 weeks gestation in clinics in Gauteng province, South Africa. Socio-demographic and dietary intake data were collected at <18 week’s gestation. Anthropometric and medical history were collected, and blood pressure measured at <18, 22 and 36 week’s gestation. Red blood cell phospholipid fatty acid composition, inflammation and iron status biomarkers were analysed at the three time points. Statistical analyses were performed using SPSS version 26 to assess the descriptive status of participants and determine the relationship between LCPUFA status and blood pressure. Results - The compositions of arachidonic acid (AA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and n-3 LCPUFA correlated positively with systolic blood pressure (r=0.133, p=0.044; r=0.208, p=0.002; r=0.217, p=0.001 and r=0.213, p=0.001) at 22 week’s gestation. EPA, DHA and total n-3 LCPUFA correlated positively with diastolic blood pressure (r=0.149, p=0.024; r=0.226, p=0.001 and r=0.210, p=0.001) and EPA with pulse pressure (r=0.133, p=0.045) at 22 week’s gestation. The n6/n3 LCPUFA ratio correlated negatively with both systolic blood pressure and diastolic blood pressure in week 2 of gestation (r=-0.170, p=0.010 and r= -0.175, p=0.008 respectively). Compositions of EPA, DHA, n-3 LCPUFA and the n6/n3 LCPUFA ratio (all p<0.05) were higher in the prehypertensive than in the normotensive group in the unadjusted and adjusted

linear regression models (adjusted for age, gestational age, parity, aspirin intake and mid-upper arm circumference (MUAC) and additionally for the respective individual or grouped fatty acid intake of the status marker which was assessed) at 22 week’s gestation. There was no loss of significance when additionally adjusting for alpha-1-Acid glycoprotein, C-reactive protein, ferritin or transferrin receptor at <18 week’s gestation. Conclusion - The findings of this dissertation show a positive relationship between n-3 LCPUFA status and blood pressure in the context of routine iron supplementation during pregnancy in women of African descent. Notably, the relationship was independent of dietary n-3 LCPUFA intake, therefore, we hypothesise that the higher n-3 LCPUFA may be a genetically driven metabolic response to the physiological circumstances in this predominantly black African study population.