Vitamin E: the shrew waiting to be tamed

alpha-Tocopherol administration produces an antidepressant-like effect in predictive animal models of depression

This study investigated the antidepressant potential of alpha-tocopherol, the most active and abundant form of vitamin E, in the forced swim test (FST) and tail suspension test (TST). The acute oral treatment with alpha-tocopherol at the doses of 30 and 100mg/kg reduced the immobility time in the FST and in the TST. A single i.c.v. administration of alpha-tocopheryl phosphate, a water-soluble analogue of alpha-tocopherol, also reduced the immobility time in the FST (0.1 and 1 nmol/site) and in the TST (0.1 nmol/site). In addition, the long-term treatment (28 days) with alpha-tocopherol (10mg/kg, p.o.) significantly reduced the immobility time in the FST. Moreover, a subeffective dose of alpha-T (10mg/kg, p.o.) potentiated the effect of fluoxetine (10mg/kg, p.o.) in the FST. The long-term treatment with alpha-T was able to increase the glutathione (GSH) antioxidant defense system, while the acute treatment was not. The long-term treatment with alpha-tocopherol (10mg/kg) increased the GSH levels in the hippocampus and in the prefrontal cortex and increased the glutathione peroxidase and glutathione reductase activity in the hippocampus (10mg/kg) and in the prefrontal cortex (10-100mg/kg). The long-term treatment with fluoxetine (10mg/kg, p.o.), a positive control, was also able to increase the GSH levels in the hippocampus, but failed to alter the activity of both enzymes. Besides the specific antidepressant-like effect, long-term, but not the acute treatment with alpha-T, especially in the doses that produced an antidepressant-like effect (10mg/kg), improved the antioxidant defenses in the mouse hippocampus and prefrontal cortex, two structures closely implicated in the pathophysiology of depression.

alpha-Tocopherol transfer protein inhibition is effective in the prevention of cerebral malaria in mice

BACKGROUND

Nutritional status likely plays an important role in determining the outcome of protozoan infections. Despite the evidence of Plasmodium sensitivity to oxidative stress, the potential role of vitamin E, a free radical scavenger, on the outcome of cerebral malaria (CM) has yet to be elucidated.

OBJECTIVE

To determine the influence of vitamin E on Plasmodium parasite development and murine CM outcome, alpha-tocopherol transfer protein (alpha-TTP), a regulator of vitamin E in the host circulation, was abrogated.

DESIGN

alpha-TTP knockout mice were infected with Plasmodium berghei ANKA, and survival rate, parasitemia, brain histologic alterations, and brain barrier permeability were assessed. In addition, mRNA expression of the cytokines and adhesion molecules involved in this neurologic pathology were monitored.

RESULTS

alpha-TTP knockout mice infected with P. berghei ANKA did not exhibit any clinical or pathologic signs of CM, and a histologic analysis of the brain tissues in these animals showed no alteration of blood-brain barrier integrity compared with that in control mice. Interestingly, protection of the blood-brain barrier in these infected alpha-TTP knockout mice was lost when dietary supplementation with vitamin E was added to their diet. Moreover, interleukins and adhesion molecule transcripts in the brain of control mice were significantly up-regulated compared with those in the alpha-TTP knockout mice.

CONCLUSION

It appears that a deficiency of alpha-tocopherol in the circulation prevents CM and suggests that alpha-TTP is a putative target for the early prevention of CM.

Tipping the redox balance of oxidative stress in fibrogenic pathways in chronic kidney disease

Patients with moderate to advanced chronic kidney disease or end-stage renal disease have a greatly increased cardiovascular risk that cannot be explained entirely by traditional cardiovascular risk factors. An increase in oxidative stress and inflammation have been proposed as nontraditional cardiovascular risk factors in this patient population. Oxidative stress reflects the redox balance between oxidant generation and antioxidant mechanisms. The generation of reactive oxygen species is not simply a random process that oxidizes nearby macromolecules, but, in many instances, the oxidants target particular amino acid residues or lipid moieties. Oxidant mechanisms are now recognized to be intimately involved in cell signaling and to be vital components of the immune response. This is equally true for antioxidant mechanisms as well. In the progression of chronic kidney disease, the redox balance is not in equilibrium and is tipped toward oxidation, resulting in the dysregulation of cellular process and subsequent tissue injury. In this review we discuss the major oxidant and antioxidant pathways and the biomarkers to assess redox status. We also review the data linking the pathogenesis of oxidative stress, inflammation, and the progressive loss of kidney function in chronic kidney disease.

The effect of alpha-tocopherol transfer protein gene disruption on Trypanosoma congolense infection in mice

At present 15 to 20 million people are estimated to be infected with pathogenic trypanosome parasites worldwide, mainly in developing countries. There are a number of factors that affect the severity of trypanosomiasis, including the nutritional status of the host. However, the relationship between micronutrient levels and trypanosomiasis outcome has yet to be reported in detail. Here, we demonstrate that the inhibition of alpha-tocopherol transfer protein, a determinant of the vitamin E concentration in host circulation, confers resistance to Trypanosoma congolense infection, evidently owing to oxidative damage to parasite DNA. These results suggest that transient inhibition of alpha-tocopherol transfer gene activity could possibly be exploited as a strategy for both the prevention and the treatment of trypanosomiasis.

Vitamin-regulated cytokines and growth factors in the CNS and elsewhere

There is a growing awareness that natural vitamins (with the only exception of pantothenic acid) positively or negatively modulate the synthesis of some cytokines and growth factors in the CNS, and various mammalian cells and organs. As natural vitamins are micronutrients in the human diet, studying their effects can be considered a part of nutritional genomics or nutrigenomics. A given vitamin selectively modifies the synthesis of only a few cytokines and/or growth factors, although the same cytokine and/or growth factor may be regulated by more than one vitamin. These effects seem to be independent of the effects of vitamins as coenzymes and/or reducing agents, and seem to occur mainly at genomic and/or epigenetic level, and/or by modulating NF-kappaB activity. Although most of the studies reviewed here have been based on cultured cell lines, but their findings have been confirmed by some key in vivo studies. The CNS seems to be particularly involved and is severely affected by most avitaminoses, especially in the case of vitamin B(12). However, the vitamin-induced changes in cytokine and growth factor synthesis may initiate a cascade of events that can affect the function, differentiation, and morphology of the cells and/or structures not only in the CNS, but also elsewhere because most natural vitamins, cytokines, and growth factors cross the blood-brain barrier. As cytokines are essential to CNS-immune and CNS-hormone system communications, natural vitamins also interact with these circuits. Further studies of such vitamin-mediated effects could lead to vitamins being used for the treatment of diseases which, although not true avitaminoses, involve an imbalance in cytokine and/or growth factor synthesis.

Correlation between neurological dysfunction with vitamin E deficiency and gastrectomy

OBJECTIVE

We previously reported on vitamin E malabsorption after gastrectomy. In this study, we focused on neurological dysfunction due to serum vitamin E decrease during the postgastrectomy period in lager number of patients.

METHODS

We examined the type of gastrectomy, type of reconstruction, serum vitamin E level, and neurological status for 96 gastrectomy patients.

RESULTS

Low serum vitamin E levels were observed in 20 patients, and 10 of those patients suffered some neurological symptoms, i.e., peripheral neuropathy, limb or truncal ataxia. Vitamin E levels tended to decrease with time after gastrectomy, and the number of patients with low serum vitamin E levels increased at about 50 months after gastrectomy. This relationship was stronger in total gastrectomy patients than in subtotal gastrectomy patients. Ten patients were given oral vitamin E, and serum vitamin E levels normalized in 9 of the patients and neurological abnormalities improved in 8 patients. An oral intake of 300 mg or more of vitamin E was necessary for normalization of vitamin E levels.

CONCLUSIONS

Gastrectomy should be considered a risk for vitamin E deficiency and neurological disturbance over the long-term clinical course. An oral vitamin E supply can improve serum vitamin E levels and neurological symptoms.

Do carotenoids serve as transmembrane radical channels?

Carotenoids are a diverse group of terpenoid pigments that originated in prokaryotes over 3 billion years ago. Their primary function in plants is to serve as photomodulators of the oxidizing side of Photosystem II. In animals, which must acquire carotenoids from their diets, carotenoids serve a host of functions and are viewed primarily as efficient scavengers of singlet oxygen and radicals within the domain of membranes where they reside. Recently it has been demonstrated that carotenoids react cooperatively and synergistically with vitamin C and E, serving to regenerate a pro-oxidant radical carotenoid after the antioxidant reduction of a radical species. The exact location and behavior of carotenoids within biological membrane systems remain largely unknown. A hypothesis is proposed suggesting that carotenoids may serve as transmembrane radical channels. In this capacity carotenoids may reduce radicals in one biological compartment, while simultaneously being reduced in another. The benefit of rapid radical quenching across membrane compartments by transmembrane-spanning carotenoids such as zeaxanthin and lutein may be especially advantageous to intra- and extracellular redox control.