Alpha-tocopherol concentration in fetal and maternal tissues of pregnant rats supplemented with alpha-tocopherol

Modulated phases of phospholipid bilayers induced by tocopherols

The influence of α-, γ- and δ-tocopherols on the structure and phase behavior of dipalmitoyl phosphatidylcholine (DPPC) bilayers has been determined from X-ray diffraction studies on oriented multilayers. In all the three cases the main-transition temperature (T(m)) of DPPC was found to decrease with increasing tocopherol concentration up to around 25 mol%. Beyond this the main transition is suppressed in the case of γ-tocopherol, whereas T(m) becomes insensitive to composition in the other two cases. The pre-transition is found to be suppressed over a narrow tocopherol concentration range between 7.5 and 10 mol% in DPPC-γ-tocopherol and DPPC-δ-tocopherol bilayers, and the ripple phase occurs down to the lowest temperature studied. In all the three cases a modulated phase is observed above a tocopherol concentration of about 10 mol%, which is similar to the P(β) phase reported in DPPC-cholesterol bilayers. This phase is found to occur even in excess water conditions at lower tocopherol concentrations, and consists of bilayers with periodic height modulation. These results indicate the ability of tocopherols to induce local curvature in membranes, which could be important for some of their biological functions.

α-Tocopheryl phosphate--an activated form of vitamin E important for angiogenesis and vasculogenesis?

Vitamin E was originally discovered as a dietary factor essential for reproduction in rats. Since then, vitamin E has revealed many important molecular properties such as the scavenging of reactive oxygen and nitrogen species or the modulation of signal transduction and gene expression in antioxidant and nonantioxidant manners. A congenital disease, ataxia with vitamin E deficiency, which is characterized by impaired enrichment of α-tocopherol (αT) in plasma due to mutations in the α-tocopherol transfer protein gene, has been discovered. An effect of vitamin E on angiogenesis and vasculogenesis has been observed in several studies, and recently, it has been demonstrated in the placenta of pregnant ewes, possibly involving the stimulation of vascular endothelial growth factor (VEGF) expression. We recently observed that the phosphorylated form of αT, α-tocopheryl phosphate (αTP), increases the expression of VEGF. We propose that the stimulatory effect of αT on angiogenesis and vasculogenesis is potentiated by phosphorylation to αTP, which may act as a cofactor or active lipid mediator increasing VEGF expression. Increased VEGF expression and consequent enhanced angiogenesis and vasculogenesis induced by αTP may explain not only the essential roles of vitamin E on reproduction, but also its beneficial effects against pre-eclampsia, ischemia/reperfusion injury, and during wound healing. It may also serve as a survival factor for brain and muscle cells. The finding that αTP may regulate vasculogenesis may indicate potential, important pathophysiological implications.

Molecular associations of vitamin E

To understand how vitamin E fulfills its functions in membranes and lipoproteins, it is necessary to know how it associates with the lipid components of these structures and the effects its presence has on their structure and stability. Studies of model membrane systems containing vitamin E have proved to be an informative approach to address these questions. A review of the way vitamin E interacts with phospholipid bilayers, how it distributes within the structure, its motional diffusion characteristics, and orientation has been undertaken. The effect of vitamin E on membrane stability and permeability has been described. The tendency of vitamin E to form complexes with certain phospholipids is examined as is the way modulation of protein functions takes place. Finally, recent evidence relevant to the putative role of vitamin E in protecting membranes from free radical attack and the consequences of lipid oxidation in lipoproteins and membranes is examined.

Vitamin E Biochemistry and Function: A Case Study in Male Rabbit

Vitamin E supplementation has become a common procedure to promote growth and health and improve the qualitative characteristics of farm animals. It has been demonstrated to be an efficient strategy for improving their reproductive function. Germ cells are particularly vulnerable to oxidative damage and may thus require additional antioxidant protection. The aim of this review is to give a comprehensive overview of the current knowledge of the biochemistry and physiology of vitamin E; successively, the effect of this compound on the reproductive activity of rabbit buck is accurately described. In particular, this review examines studies on the effects of animal age, dose and duration of vitamin E supplementation, as well as the co-supplementation with selenium, vitamin C and polyunsaturated fatty acids. Several investigations have shown beneficial effects in bucks supplemented with vitamin E levels higher than the standard dietary requirement (50 mg/kg) particularly when the semen is stored. However, the exact dietary intake of vitamin E should be decided according to specific tissue needs for the individual vitamin E forms and the specific saturation markers.

Effects of peroxidation products in thermoxidised dietary oil in female rats during rearing, pregnancy and lactation on their reproductive performance and the antioxidative status of their offspring

The present study was performed to investigate whether lipid peroxidation products in thermoxidised dietary oil fed during rearing, pregnancy and lactation influences the reproductive performance of female rats and the antioxidant status of their offspring. Twenty-four female rats were divided into two groups at 4 weeks of age. They were fed diets containing fresh or oxidised oil (the latter prepared by heating at a temperature of 50°C for 16 d) for 14 weeks. At the age of 12 weeks female rats were mated. The number of total pups and pups born alive was not different between both groups. However, individual pups and litters of dams fed oxidised oil were lighter at birth and gained less weight during the suckling period than those of dams fed fresh oil (P>0·05). Pups of dams fed oxidised oil contained less protein and more fat in their carcasses than those of dams fed fresh oil (P>0·05). The milk of dams fed oxidised oil had a lower concentration of triacylglycerols and a lower energy content than that of dams fed the fresh oil (P>0·05). The pups of dams fed oxidised oil had higher concentrations of lipid peroxidation products in the liver at birth and day 19 of lactation than those of dams fed fresh oil (P>0·05). In conclusion, the present study shows that feeding oxidised oil with a high concentration of lipid peroxidation products to female rats during rearing, pregnancy and lactation influences the development and antioxidant status of fetus and suckling pups.

Relationship between Alpha-Tocopherol Content in the Different Lipoprotein Fractions in Term Pregnant Women and in Umbilical Cord Blood

AIMS

To determine the concentration of vitamin E in normal maternal and umbilical cord blood pairs, and to study the relationship between vitamin E content in maternal lipoprotein fractions and umbilical cord blood.

METHODS

Fifty healthy pregnant women were recruited randomly at term and blood samples were drawn from the mothers at delivery and cord blood was obtained immediately postpartum. Vitamin E was determined by HPLC in plasma, in the different lipoprotein fractions and in the placenta. Plasma levels of triglycerides and cholesterol were also measured.

RESULTS

The concentration of vitamin E in umbilical cord plasma was 250 microg/dl, lower than in maternal plasma (1,460 microg/dl) (p < 0.001). A positive correlation was found between the vitamin E concentration in maternal plasma, LDL and VLDL and in the umbilical cord plasma. In contrast, no correlation was found between maternal HDL concentration and umbilical cord blood.

CONCLUSION

These results show that the concentration of vitamin E in umbilical cord blood is lower than in maternal plasma. LDL and VLDL seem to be the main source of vitamin E for the fetus.

Antioxidant vitamin levels in term and preterm infants and their relation to maternal vitamin status

BACKGROUND

Lipid peroxidation plays a vital role in the pathogenesis of many neonatal complications. Preterm babies are especially predisposed to lung diseases and retinopathy, probably due to a deficiency in their antioxidant systems. Vitamins E, A, and C are part of the natural antioxidant defense systems. We aimed to determine the levels of vitamins E, A, and C in maternal and cord blood plasma of term and preterm infants and to investigate the relationships between these levels.

METHODS

In the present study we determined vitamin E, A, and C levels in the umbilical cord blood of term (n = 30) and preterm (n = 22) infants and their mothers by HPLC. Blood samples were taken during delivery.

RESULTS

Levels of lipid soluble antioxidant vitamin E and A in cord blood were lower than maternal values (p <0.01, p <0.05, respectively). Conversely, the level of water-soluble vitamin C was higher in cord blood than in maternal level (p <0.05). Significantly higher levels of vitamins E, A, and C were found in term babies as compared with those born preterm (p <0.05).

CONCLUSIONS

There was a positive correlation between maternal and cord blood levels of vitamins E and A (r = 0.775, r = 0.725, respectively). In conclusion, preterm babies have fewer lipid-soluble antioxidant vitamins in their serum compared to term infants. Therefore, it is possible to postulate that preterm infants are more susceptible to oxidative stress.

Impaired arachidonic (20:4n-6) and docosahexaenoic (22:6n-3) acid synthesis by phenylalanine metabolites as etiological factors in the neuropathology of phenylketonuria

The recent literature on polyunsaturated fatty acid metabolism in phenylketonuria (PKU) is critically analyzed. The data suggest that developmental impairment of the accretion of brain arachidonic (20:4n-6) and docosahexaenoic (22:6n-3, DHA) acids is a major etiological factor in the microcephaly and mental retardation of uncontrolled PKU and maternal PKU. These fatty acids appear to be synthesized by the recently elucidated carnitine-dependent, channeled, mitochondrial fatty acid desaturases for which alpha-tocopherolquinone (alpha-TQ) is an essential enzyme cofactor. alpha-TQ can be synthesized either de novo or from alpha-tocopherol. The fetus and newborn would primarily rely on de novo alpha-TQ synthesis for these mitochondrial desaturases because of low maternal transfer of alpha-tocopherol. Homogentisate, a pivotal intermediate in the de novo pathway of alpha-TQ synthesis, is synthesized by 4-hydroxyphenylpyruvate dioxygenase. The major catabolic products of excess phenylalanine, viz. phenylpyruvate and phenyllactate, are proposed to inhibit alpha-TQ synthesis at the level of the dioxygenase reaction by competing with its 4-hydroxyphenylpyruvate substrate, thus leading to a developmental impairment of 20:4n-6 and 22:6n-3 synthesis in uncontrolled PKU and fetuses of PKU mothers. The data suggest that dietary supplementation with carnitine, 20:4n-6, and 22:6n-3 may have therapeutic value for PKU mothers and for PKU patients who have been shown to have a low plasma status of these essential metabolites.

Pathogenesis of diabetes-induced congenital malformations

The increased rate of fetal malformation in diabetic pregnancy represents both a clinical problem and a research challenge. In recent years, experimental and clinical studies have given insight into the teratological mechanisms and generated suggestions for improved future treatment regimens. The teratological role of disturbances in the metabolism of inositol, prostaglandins, and reactive oxygen species has been particularly highlighted, and the beneficial effect of dietary addition of inositol, arachidonic acid and antioxidants has been elucidated in experimental work. Changes in gene expression and induction of apoptosis in embryos exposed to a diabetic environment have been investigated and assigned roles in the teratogenic processes. The diabetic environment appears to simultaneously induce alterations in several interrelated teratological pathways. The complex pathogenesis of diabetic embryopathy has started to unravel, and future research efforts will utilize both clinical intervention studies and experimental work that aim to characterize the human applicability and the cell biological components of the discovered teratological mechanisms.