Dietary vitamin E deficiency increases anxiety-like behavior in juvenile and adult rats

Twendee X, a mixed antioxidant supplement, improves cognitive function, coordination, and neurotrophic factor expression in long-term vitamin E-deficient mice

Oxidation products gradually accumulate during senescence, enhancing the risk of onset of many severe diseases. One such disease is dementia, and the number of cases of dementia, including Alzheimer's disease, has been increasing world-wide. These diseases can be prevented via attenuation of age-related physiological dysfunction; one preventive approach is the ingestion of antioxidants such as vitamin C and vitamin E. Many antioxidants are readily available commercially. Ingestion of mixed antioxidants is expected to provide further beneficial effects for human health. In this study, we used vitamin E-deficient mice as an animal model of increased oxidative stress and assessed the effects of dosing with mixed antioxidants. Administration of a commercial mixed antioxidant formula, Twendee X significantly improved cognitive function and coordination compared to untreated vitamin E-deficient animals. Furthermore, the levels of brain-derived neurotrophic factor and nerve growth factor were significantly increased in the cerebral cortex of Twendee X-dosed vitamin E-deficient mice compared to untreated animals. These results indicate that intake of a mixed antioxidant supplement may be beneficial to human health, even after oxidative stress has begun. In the next stage, it will be necessary to compare with other antioxidants and consider whether it is effective in the aged model.

Increased anxiety-like behaviour is an early symptom of vitamin E deficiency that is suppressed by adrenalectomy in rats

We previously reported that dietary vitamin E deficiency increased anxiety-like behaviour in rats exposed to social isolation. Here, we performed a detailed investigation of this phenomenon and its underlying mechanism. First, we fed Wistar rats with a vitamin E-free diet for 3 d, 1 week or 2 weeks and found an increase in anxiety-like behaviour after 1 and 2 weeks of vitamin E deficiency based on behavioural indicators. Next, we examined the effect of a control diet (150 mg all-racemic α-tocopheryl acetate/kg) on anxiety-like behaviours in rats that received a 4-week vitamin E-free diet. We found that increased anxiety-like behaviour was reversed to control levels after refeeding vitamin E for 7 d but not for 1 or 3 d. Further, anxiety-like behaviour increased or decreased gradually based on the amount of vitamin E intake; however, it had a quicker progression than physical symptoms of vitamin E deficiency. Moreover, rats fed with excess vitamin E (500 mg all-racemic α-tocopherol/kg diet) showed less anxiety-like behaviour than control rats, indicating that vitamin E supplementation is effective for preventing anxiety increase under social isolation stress. Since plasma corticosterone levels were higher in vitamin E-deficient rats, we investigated the effect of adrenalectomy on anxiety-like behaviour and found that adrenal hormones played an essential role in the increased anxiety-like behaviour induced by vitamin E deficiency. In conclusion, increased anxiety-like behaviour is a symptom that emerges earlier than physical vitamin E deficiency and is caused by adrenal hormone-dependent mechanisms.

Oxidative Stress Mediates Anxiety-Like Behavior Induced by High Caffeine Intake in Zebrafish: Protective Effect of Alpha-Tocopherol

Anxiety is a common symptom associated with high caffeine intake. Although the neurochemical mechanisms of caffeine-induced anxiety remain unclear, there are some evidences suggesting participation of oxidative stress. Based on these evidences, the current study is aimed at evaluating the possible protective effect of alpha-tocopherol (TPH) against anxiety-like behavior induced by caffeine (CAF) in zebrafish. Adult animals were treated with CAF (100 mg/kg) or TPH (1 mg/kg)+CAF before behavioral and biochemical evaluations. Oxidative stress in the zebrafish brain was evaluated by a lipid peroxidation assay, and anxiety-like behavior was monitored using light/dark preference and novel tank diving test. Caffeine treatment evoked significant elevation of brain MDA levels in the zebrafish brain, and TPH treatment prevented this increase. Caffeine treatment also induced anxiety-like behavior, while this effect was not observed in the TPH+CAF group. Taken together, the current study suggests that TPH treatment is able to inhibit oxidative stress and anxiety-like behavior evoked by caffeine.

Effect of dietary vitamin E on oxidative stress-related gene-mediated differences in anxiety-like behavior in inbred strains of mice

It has been reported that the degree of anxiety-like behavior differs between inbred strains of mice, and that this phenomenon was linked to the expression levels of the oxidative stress-related genes glyoxalase 1 (Glo1) and glutathione reductase 1 (Gsr) in the brain. Therefore, we investigated whether antioxidative activity in the brain affects the Glo1 and Gsr mRNA expressions and strain-dependent anxiety-like behavior using mice fed different amounts of vitamin E. First, we measured brain Glo1 and Gsr mRNA levels and evaluated the anxiety-like behaviors presented by C57BL/6J (B6) and DBA/2C (D2) mice. We demonstrated that D2 mice presented both significantly elevated Glo1 and Gsr mRNA levels as well as more prominent anxiety-like behavior in elevated plus-maze and open field tests. Next, we fed mice from these two strains either a control, vitamin E-free, or vitamin E-supplemented diet for four weeks. Plasma, liver, and brain α-tocopherol concentrations changed in a dose-dependent manner. However, neither brain Glo1 and Gsr mRNA levels nor anxiety-like behavior were affected by dietary vitamin E intake. These results demonstrated that while strain-dependent anxiety-like behavior in mice was related to oxidative stress-related gene expression, the regulatory mechanisms for these genes and anxiety-like behaviors were independent of antioxidative activity in the brain. Strain-dependent differences of the anxiety in mice are probably related to the anxiolytic effects of methylglyoxal, a substrate for Glo1 and Gsr.

Brain Vitamin E Deficiency During Development Is Associated With Increased Glutamate Levels and Anxiety in Adult Mice

Vitamin E, the most important lipophilic radical scavenging antioxidant in vivo, has a pivotal role in brain. In an earlier study, we observed that adult mice with a defect in the gene encoding plasma phospholipid transfer protein (PLTP) display a moderate reduction in cerebral vitamin E levels, and exacerbated anxiety despite normal locomotion and memory functions. Here we sought to determine whether dietary vitamin E supplementation can modulate neurotransmitter levels and alleviate the increased anxiety phenotype of PLTP-deficient (PLTP^−/−) mice. To address this question, a vitamin E-enriched diet was used, and two complementary approches were implemented: (i) “early supplementation”: neurotransmitter levels and anxiety were assessed in 6 months old PLTP^−/− mice born from vitamin E-supplemented parents; and (ii) “late supplementation”: neurotransmitter levels and anxiety were assessed in 6 months old PLTP^−/− mice fed a vitamin E-enriched diet from weaning. Our results show for the first time that an inadequate supply of vitamin E during development, due to moderate maternal vitamin E deficiency, is associated with reduced brain vitamin E levels at birth and irreversible alterations in brain glutamate levels. They also suggest this deficiency is associated with increased anxiety at adulthood. Thus, the present study leads to conclude on the importance of the micronutrient vitamin E during pregnancy.

Testosterone represses urinary excretion of the alpha-tocopherol metabolite alpha-carboxymethylhydroxychroman in rats

In rats, plasma and tissue concentrations of α-tocopherol, a predominant form of vitamin E in mammals, are known to differ between the sexes. In order to examine sex differences in α-tocopherol metabolism, we investigated urinary excretion of the α-tocopherol metabolite α-carboxymethylhydroxychroman (α-CEHC) using Wistar rats. First, we measured α-CEHC in urine of 9-week-old male and female rats in basal and α-tocopherol-administered conditions. We observed that female rats excrete significantly more α-CEHC than male rats via urine. This sex difference was observed in matured 9-week-old rats but not in premature 3-week-old rats, suggesting that the difference may relate to sex hormones. In order to confirm this, we examined the effect of ovariectomy and orchiectomy on female and male rats, respectively. The results of castration clearly demonstrated that orchiectomy enhanced urinary excretion of α-CEHC, supporting the hypothesis that testosterone repressed α-tocopherol metabolism. We then administered testosterone propionate to orchiectomized rats and observed down-regulation of α-CEHC excretion. Taken together, these results indicate that testosterone represses the metabolism and urinary excretion of α-tocopherol in rats. This is the first report to show a sex-dependent difference in urinary excretion rate of an α-tocopherol metabolite and contributes to the understanding of vitamin E metabolism.

Long-Term Vitamin E-Deficient Mice Exhibit Cognitive Dysfunction via Elevation of Brain Oxidation

Vitamin E inhibits oxidative processes in living tissues. We produced vitamin E-deficient mice by feeding them a vitamin E-deficient diet to verify the influence of chronic vitamin E deficiency on cognitive function. We measured cognitive function over a 5-d period using the Morris water maze task, as well as antioxidant enzyme activity and lipid peroxidation in discrete brain regions, and total serum cholesterol content. Three- and six-mo-old vitamin E-deficient and age-matched control mice were used. In addition, 24-mo-old mice were used as an aged-model. In the 3-mo-old mice, cognitive function in the vitamin E-deficient (short-term vitamin E-deficient) group was significantly impaired compared to age-matched controls. Although the lipid peroxidation products in the cerebral cortex, cerebellum and hippocampus did not significantly differ in 3-mo-old mice, the levels in the 6-mo-old vitamin E-deficient (long-term vitamin E-deficient) mice were significantly increased compared to age-matched controls. Serum cholesterol content was also significantly increased in the short- and long-term vitamin E-deficient mice compared to their respective age-matched controls. These results indicate that chronic vitamin E deficiency may slowly accelerate brain oxidation. Thus, vitamin E concentrations may need to be monitored in order to prevent the risk of cognitive dysfunction, even under normal conditions.

Acute dietary tryptophan manipulation differentially alters social behavior, brain serotonin and plasma corticosterone in three inbred mouse strains

Clinical evidence indicates brain serotonin (5-HT) stores and neurotransmission may be inadequate in subpopulations of individuals with autism, and this may contribute to characteristically impaired social behaviors. Findings that depletion of the 5-HT precursor tryptophan (TRP) worsens autism symptoms support this hypothesis. Yet dietetic studies show and parents report that many children with autism consume less TRP than peers. To measure the impact of dietary TRP content on social behavior, we administered either diets devoid of TRP, with standard TRP (0.2 g%), or with 1% added TRP (1.2 g%) overnight to three mouse strains. Of these, BTBRT(+)Itpr3(tf)/J and 129S1/SvImJ consistently exhibit low preference for social interaction relative to C57BL/6. We found that TRP depletion reduced C57BL/6 and 129S social interaction preference, while TRP enhancement improved BTBR sociability (p < 0.05; N = 8-10). Subsequent marble burying did not differ among diets or strains. After behavior tests, brain TRP levels and plasma corticosterone were higher in TRP enhanced C57BL/6 and BTBR, while 5-HT levels were reduced in all strains by TRP depletion (p < 0.05; N = 4-10). Relative hyperactivity of BTBR and hypoactivity of 129S, evident in self-grooming and chamber entries during sociability tests, were uninfluenced by dietary TRP. Our findings demonstrate mouse sociability and brain 5-HT turnover are reduced by acute TRP depletion, and can be enhanced by TRP supplementation. This outcome warrants further basic and clinical studies employing biomarker combinations such as TRP metabolism and 5-HT regulated hormones to characterize conditions wherein TRP supplementation may best ameliorate sociability deficits.

Blood reflects tissue oxidative stress: a systematic review

We examined whether the levels of oxidative stress biomarkers measured in blood reflect the tissue redox status. Data from studies that measured redox biomarkers in blood, heart, liver, kidney and skeletal muscle were analyzed. In seven out of nine investigated redox biomarkers (malondialdehyde, reduced glutathione, superoxide dismutase, catalase, glutathione peroxidase, vitamin C and E) there was generally good qualitative and quantitative agreement between the blood and tissues. In contrast, oxidized glutathione and the reduced to oxidized glutathione ratio showed poor agreement between the blood and tissues. This study suggests that most redox biomarkers measured in blood adequately reflect tissue redox status.

Vitamin E depletion enhances liver oxidative damage in rats with water-immersion restraint stress

We examined the effect of vitamin E depletion on liver oxidative damage in rats with water-immersion restraint stress (WIRS). Male Wistar rats were fed a normal diet (N) or vitamin E-depleted diet (VE-D) for 4 wk. N- and VE-D-fed rats were exposed to WIRS for 6 h. The activities of serum transaminases and lactate dehydrogenase and serum ascorbic acid concentration were similar in both diet groups. WIRS exposure increased these serum enzyme activities and the serum ascorbic acid concentration in both diet groups but the ratios of these increases were higher in VE-D-fed rats than in N-fed rats. Serum and liver α-tocopherol concentrations in VE-D-rats were approximately 50% and 30% of those in N-fed rats, respectively. WIRS exposure reduced liver α-tocopherol concentration in VE-D-fed rats, but not in N-fed rats. Liver ascorbic acid and reduced glutathione concentrations were higher in the VE-D-fed group than in the N-fed group. WIRS exposure reduced liver ascorbic acid and reduced glutathione concentrations in both diet groups. There were no differences in liver concentrations of coenzyme Q9 or coenzyme Q10 in the reduced form between the N- and VE-D-fed groups. WIRS exposure reduced liver concentrations of coenzyme Q9 and coenzyme Q10 in the reduced form in both diet groups. Liver lipid peroxide concentration was higher in the VE-D-fed group than in the N-fed group. WIRS exposure raised liver lipid peroxide concentration more in the VE-D-fed group than in the N-fed group. These results indicate that vitamin E depletion enhances liver oxidative damage in rats with WIRS.

Anti-oxidative and DNA Protecting Effects of Flavonoids-rich Scutellaria Lateriflora

Scutellaria lateriflora (American skullcap), a native plant of North America, has been used by Americans and Europeans as a nerve tonic for more than 200 years. In vivo studies have shown anxiolytic activity of S. lateriflora in animals and humans. However, the neuroprotective mechanisms of S. lateriflora are not fully understood. Oxidative stress plays a vital role in the neurodegenerative and neuropsychiatric diseases such as anxiety, Alzheimer's disease, depression, and Parkinson's disease. Bioactive compounds present in various medicinal plants neutralize or scavenge toxic free radicals and thus suppress oxidative stress. Therefore, the objective of this study was to investigate the antioxidant effects of S. lateriflora. The antioxidant potential of aqueous or ethanolic extracts of S. lateriflora was determined in mouse brain tissue using various biochemical assays. Protective effects of S. lateriflora against oxidative stress induced DNA fragmentation was determined using plasmid DNA. The ethanolic and aqueous extracts scavenged the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals. The ethanolic extract reduced tert-butyl peroxide-induced reactive oxygen species (ROS) and lipid peroxides in the mouse brain homogenates. Furthermore, the ethanolic extract of S. lateriflora protected hydrogen peroxide-UV induced cleavage of supercoiled plasmid DNA. In conclusion, S. lateriflora exhibited significant antioxidant effects. The current findings posit S. lateriflora as one of the potential experimental herbal drugs that should be screened for its therapeutic potential against various oxidative stress associated mental disorders.