Effect of dietary omega-3 supplementation on plasma phospholipids, neutral lipids fatty acids and antioxidant status of pregnant women with gestational diabetes and their neonates
Background: Gestational diabetes mellitus (GDM) has adverse effects on the level of docosahexaenoic acid (DHA) in phospholipids of maternal and cord red blood cells and cord plasma. This finding was of major concern because DHA is vital for maternal wellbeing and health, and for optimal development of foetal brain and retina. GDM is also associated with increased oxidative stress. There is controversy about omega-3 LCPUFA supplementation and oxidative damage. This ambiguity needs to be explored to reveal its role as modulator of oxidative stress in GDM. Specific Aims: To investigate if (1) GDM adversely affects the plasma omega-3 and omega-6 long-chain polyunsaturated fatty acid (LCPUFA) levels in pregnant women. (2) High BMI is associated with adverse plasma fatty acid profile in GDM women. (3) Supplementation with DHA-enriched formula, enhances the level of the nutrient in the GDM women and their neonates. (4) Antioxidant vitamins status is enhanced by DHA-enriched supplementation in GDM women and their newborns. Methods: Women with (n = 142; 72 active-group, 70 placebo) and without gestational diabetes (n = 28; 10 active-group, 18 placebo) were supplemented from the recruitment (at Newham University Hospital, London) until delivery. Both active- and placebo-groups received 2 capsules of either DHA-enriched formula or high oleic acid sunflower seed oil respectively. Each active supplement capsule contained 300 mg of DHA, 42 mg of eicosapentaenoic acid (EPA) and 8.4 mg of AA, and placebo 721 mg of oleic acid. Blood samples taken from the mothers at recruitment and delivery (maternal and cord) were analysed for plasma fatty acid composition and antioxidant vitamins levels. Results: At recruitment, no significant difference was found in the DHA level in plasma phospholipids (CPG, 4.9% vs. 4.4%, P > 0.05) and neutral lipids (CE, 0.9% vs. 0.9%, P > 0.05), (TG, 0.9% vs. 0.9%, P > 0.05) between healthy pregnant and GDM women respectively. When categorized on the basis of their BMI, obese and over-weight GDM women had lower omega-3 (ALA, P < 0.05) and higher omega-6 PUFA (AA, P < 0.05) levels as compared to normal-weight GDM women. A total of 140 women completed the trial. GDM active-group compared with GDM placebo-group had significantly higher percentage of DHA in plasma CPG (4.4% vs. 3.7%, P < 0.05), CE (1.1% vs. 0.9%, P < 0.05), and TG (1.2% vs. 0.8%, P < 0.05) at delivery. There was no significant difference in the cord plasma [CPG (5.4% vs. 5.8%, P > 0.05), CE (1.1% vs. 1.0%, P > 0.05), TG (2.9% vs. 3.3%, P > 0.05)] DHA between GDM placebo and active-treatment groups. Though not significantly, the levels of vitamin A and β-carotene were reduced, however, the level of vitamin E was comparable between GDM and healthy pregnant women, at recruitment (P > 0.05). At delivery, no significant difference was found in maternal plasma vitamin A (21.1 µg/dl vs. 18.0 µg/dl, P > 0.05), vitamin E (1.4 mg/dl vs. 1.4 mg/dl, P > 0.05) and β-carotene (16.1 µg/dl vs. 11.1 µg/dl, P > 0.05) levels between GDM placebo- and active-treatment groups. Neonatal plasma antioxidant vitamins levels were also comparable between GDM active-treatment and placebo groups (P > 0.05). Conclusion: The present study shows that the plasma DHA and AA levels are not compromised by gestational diabetes in pregnant women. It may be that the comparable plasma DHA and AA levels observed in the GDM women is linked to a failure to incorporate these fatty acids into the phospholipids of the red cell membrane and/or impaired placental transport. Moreover, the majority of samples were collected during the third trimester (between 28-32 weeks), so it is plausible that the duration of the diabetes was very short to produce an obvious adverse effect on the plasma DHA and AA levels. Additionally, this study shows that higher pre-pregnancy BMI is associated with higher n-6 PUFA and lower n-3 PUFA levels in GDM women. However, it is difficult to establish whether BMI causes adverse fatty acids profile, or whether the direction of this association is reversed. This unique study also demonstrated that supplementation with a daily dose of DHA (600mg) from diagnosis until delivery was effective in enhancing the level of the nutrient in plasma of GDM women but not foetal. The inefficacy of the supplement to improve foetal status suggests that the transfer of DHA across the placenta may be impaired in the GDM women. This finding has implications for the management of neonates born to GDM women because they are born with a lower level of DHA and the condition is considered to be linked with a risk of neuro-developmental deficit. We suggest that the provision of a DHA supplement should be integrated with the antenatal care of pregnant women with gestational diabetes to optimize foetal development and avert maternal DHA depletion in pregnancy. Also, the babies of the GDM women, particularly those not sucking mother’s milk, similar to those who born prematurely require formula milk containing a higher level of DHA. This study demonstrates that DHA-enriched supplement did not improve yet not deteriorate the antioxidant vitamins status in GDM women. This may be because of small dose and short duration of supplementation. We can allude that the moderate amounts of omega-3 LCPUFA in dietary intake for longer duration may reduce the incidence and complications associated with oxidative stress in diabetic pregnancy.
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