Early Nutrition and Lifestyle Factors by Asim K. Duttaroy & Sanjay Basak

Author:Asim K. Duttaroy & Sanjay Basak
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

6.4 Vitamin E and Placentation

Vitamin E is originally discovered as an essential factor for reproduction. Isolation of vitamin E by Evans and Bishop is evidenced first time with their wheat germ feeding experiment in rats. Vitamin E is named as tocopherol, from the Greek words “tocos” (birth), and “pherin” (to carry) with the ending “-ol” indicating its status as a chemical alcohol. Vitamin E comprises eight isomers α-, β -, γ-, and δ- tocopherols and the α-, β -, γ-, and δ- tocotrienol occur naturally as RRR-stereoisomers. RRR-α-tocopherol is selectively enriched by the liver in plasma by the α-tocopherol transfer protein (α-TTP), and remaining isoforms are not enriched in plasma (therefore level below 1 μM) but metabolized. Mean plasma value of α-tocopherol is normally about 23.2 μM with a plasma level below 11.6 μM regarded as deficient. In human, premature babies are often characterized by vitamin E deficiency, with plasma α-tocopherol levels lower than 5 μg/mL (11.6 μM).

The prominent understanding of vitamin E action as antioxidant is well established. Generally, during vitamin E deficiency, lipid peroxidation occurs which leads to oxidative chain reactions with a production of free radicals that ultimately participate in nonspecific reactions with functional and structural compounds. Vitamin E can reduce lipid peroxides or scavenge free radicals from chain reactions. The role of vitamin E is similar with the enzyme glutathione peroxidase system for their antioxidative action. However, antioxidative action of vitamin E and glutathione peroxidase operates in different subcellular location, e.g., glutathione peroxidase operates in cytosol, whereas vitamin E is mainly located in the membranes of the cell (Veen and Grimbergen 1975). Interestingly, fat-soluble vitamin E is the least accumulated vitamin among the fat-soluble vitamins A, D, and K. The need for vitamin E is increased during pregnancy when the diet is rich in PUFA. Increased amounts of vitamin E are needed in low-birth-weight (LBW) infants fed with diets rich in PUFA. Accumulation of lipid-soluble vitamins in fetal tissue occurs mostly in the third trimester of gestation. Due to this, preterm infant stores less of vitamin E as compared to full term. It could also possible that lipid-soluble vitamins are mostly utilized during early trimesters of pregnancy to provide optimum nourishment for the feto-placental unit (Orzalesi and Colarizi 1982).

α-TTP is a cytosolic protein mostly present in the liver that specifically binds α-tocopherol (Dutta-Roy 1997). Expression of α-TTP is increased after implantation. Data shows that uterine α-TTP may contribute an important role in supplying vitamin E. Mice placentas of pregnant α-TTP(-/-) show disrupted growth of labyrinthine trophoblasts which is possibly due to inadequate supply of antioxidant vitamin E. Excess α-tocopherol prevented placental failure and allowed full-term pregnancies (Jishage et al. 2001). α-TTP is expressed in human placenta in different subcellular compartment that includes in cytosol but predominantly in the nuclear fraction of the trophoblast and endothelium fetal capillaries. α-TTP knockout mice are infertile and exhibit similar symptom as with severe vitamin E deficiency (Muller-Schmehl et al. 2004). Vitamin E is critically required during the early stages of life that span from conception to the postnatal development of the offspring.

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