Excess maternal vitamin B12 supplementation increases oxidative stress and differentially influences fatty acids profile in a rat model.

Vitamin B12 status during pregnancy is an important determinant for non-communicable disease risk in later life. Vitamin B12 and fatty acid are interlinked in one carbon cycle. The effect of vitamin B12 deficiency on adverse pregnancy outcomes and fatty acid status is well known. However, the effects of excess vitamin B12 supplementation during pregnancy are less explored. This study investigates the influence of prenatal excess vitamin B12 supplementation on pregnancy outcome, fatty acids, oxidative stress, inflammation and cardiometabolic variables in Wistar rats. Female rats were divided (pre-pregnancy to pregnancy) into 3 groups as control (0.375 μg/day of vitamin B12), intermediate group (1.5 μg/day) and excess group (120 μg/day). At d20 of gestation, dams were sacrificed to collect blood and placenta for biochemical estimation. We found higher plasma vitamin B12 levels in the intermediate group and excess group (p < 0.01 for both), while folate and homocysteine levels were found to be similar across groups. The pregnancy outcome was similar between groups. We found higher erythrocyte saturated fatty acids, lower omega-6 fatty acids, omega-6/omega-3 fatty acid ratio, and Δ5 desaturase index (p < 0.05 for all) in excess group in comparison with the control group. In comparison with the control group, higher placental Δ6 desaturase index (p < 0.05) and plasma malondialdehyde levels were found (p < 0.01) in excess group. Our study demonstrates that supplementation of excess maternal vitamin B12 during pregnancy leads to increased oxidative stress and differentially influences various fatty acid levels.