Combined vitamin C and E deficiency induces motor defects in gulo(-/-)/SVCT2(+/-) mice

Ascorbate insufficiency disrupts glutamatergic signaling and alters electroencephalogram phenotypes in a mouse model of Alzheimer's disease

Clinical studies have reported that increased epileptiform and subclinical epileptiform activity can be detected in many patients with an Alzheimer's disease (AD) diagnosis using electroencephalogram (EEG) and this may correlate with poorer cognition. Ascorbate may have a specific role as a neuromodulator in AD as it is released concomitantly with glutamate reuptake following excitatory neurotransmission. Insufficiency may therefore result in an exacerbated excitatory/inhibitory imbalance in neuronal signaling. Using a mouse model of AD that requires dietary ascorbate (Gulo-/-APPswe/PSEN1dE9), EEG was recorded at baseline and during 4 weeks of ascorbate depletion in young (5-month-old) and aged (20-month-old) animals. Data were scored for changes in quantity of spike trains, individual spikes, sleep-wake rhythms, sleep fragmentation, and brainwave power bands during light periods each week. We found an early increase in neuronal spike discharges with age and following ascorbate depletion in AD model mice and not controls, which did not correlate with brain amyloid load. Our data also show more sleep fragmentation with age and with ascorbate depletion. Additionally, changes in brain wave activity were observed within different vigilance states in both young and aged mice, where Gulo-/-APPswe/PSEN1dE9 mice had shifts towards higher frequency bands (alpha, beta, and gamma) and ascorbate depletion resulted in shifts towards lower frequency bands (delta and theta). Microarray data supported ascorbate insufficiency altering glutamatergic transmission through the decreased expression of glutamate related genes, however no changes in protein expression of glutamate reuptake transporters were observed. These data suggest that maintaining optimal brain ascorbate levels may support normal brain electrical activity and sleep patterns, particularly in AD patient populations where disruptions are observed.

A mixed antioxidant supplement improves cognitive function, and coordination in aged mice

Accumulation of oxidative damage increases the risk of several disorders. To prevent these diseases, people consume supplements. However, there is little evidence of the impact of supplement intake on cognitive function. Recently, frailty and sarcopenia have become serious issues, and these phenomena include a risk of mild cognitive impairment. In this study, aged mice were fed the combination supplement and cognitive and motor functions were measured. Following 1 month of treatment with the supplement, significant improvements in cognitive function and neuromuscular coordination were observed. Following 2 weeks of treadmill training, treatment with the supplement dramatically increased running distance compared to that in untreated normal aged mice. Serum indices such as triglyceride and total cholesterol were significantly decreased in the supplement-treated aged mice compared to untreated aged mice. These results indicate that the combination supplement may play a role in maintaining cognitive function, coordination ability and improving lipid metabolism.

Determination of tissue-specific interaction between vitamin C and vitamin E in vivo using senescence marker protein-30 knockout mice as a vitamin C synthesis deficiency model

Vitamin E (α-tocopherol; VE) is known to be regenerated from VE radicals by vitamin C (L-ascorbic acid; VC) in vitro. However, their in vivo interaction in various tissues is still unclear. Therefore, we alternatively examined the in vivo interaction of VC and VE by measurement of their concentrations in various tissues of senescence marker protein-30 (SMP30) knockout (KO) mice as a VC synthesis deficiency model. Male SMP30-KO mice were divided into four groups (VC+/VE+, VC+/VE-, VC-/VE+ and VC-/VE-), fed diets with or without 500 mg/kg VE and given water with or without 1·5 g/l VC ad libitum. Then, VC and VE concentrations in the plasma and various tissues were determined. Further, gene expression levels of transporters associated with VC and VE, such as α-tocopherol transfer protein (α-TTP) and sodium-dependent vitamin C transporters (SVCTs), were examined. These results showed that the VE levels in the VC-depleted (VC-/VE+) group were significantly lower than those in the VC+/VE+ group in the liver and heart; the VC levels in the VE-depleted (VC+/VE-) group were significantly lower than those in the VC+/VE+ group in the kidneys. The α-TTP gene expression in the liver and kidneys was decreased by VC and/or VE depletion. Moreover, SVCT1 gene expression in the liver was decreased by both VC and VE depletion. In conclusion, these results indicate that VC spares VE mainly in the liver and heart and that VE spares VC in the kidneys of SMP30-KO mice. Thus, interaction between VC and VE is likely to be tissue specific.

Ascorbate Is a Primary Antioxidant in Mammals

Ascorbate (vitamin C in primates) functions as a cofactor for a number of enzymatic reactions represented by prolyl hydroxylases and as an antioxidant due to its ability to donate electrons, which is mostly accomplished through non-enzymatic reaction in mammals. Ascorbate directly reacts with radical species and is converted to ascorbyl radical followed by dehydroascorbate. Ambiguities in physiological relevance of ascorbate observed during in vivo situations could be attributed in part to presence of other redox systems and the pro-oxidant properties of ascorbate. Most mammals are able to synthesize ascorbate from glucose, which is also considered to be an obstacle to verify its action. In addition to animals with natural deficiency in the ascorbate synthesis, such as guinea pigs and ODS rats, three strains of mice with genetic removal of the responsive genes (GULO, RGN, or AKR1A) for the ascorbate synthesis have been established and are being used to investigate the physiological roles of ascorbate. Studies using these mice, along with ascorbate transporter (SVCT)-deficient mice, largely support its ability in protection against oxidative insults. While combined actions of ascorbate in regulating epigenetics and antioxidation appear to effectively prevent cancer development, pharmacological doses of ascorbate and dehydroascorbate may exert tumoricidal activity through redox-dependent mechanisms.

Decreased content of ascorbic acid (vitamin C) in the brain of knockout mouse models of Na+,K+-ATPase-related neurologic disorders

Na⁺,K⁺-ATPase is a crucial protein responsible for maintaining the electrochemical gradients across the cell membrane. The Na⁺,K⁺-ATPase is comprised of catalytic α, β, and γ subunits. In adult brains, the α3 subunit, encoded by ATP1A3, is predominantly expressed in neurons, whereas the α2 subunit, encoded by ATP1A2, is expressed in glial cells. In foetal brains, the α2 is expressed in neurons as well. Mutations in α subunits cause a variety of neurologic disorders. Notably, the onset of symptoms in ATP1A2- and ATP1A3-related neurologic disorders is usually triggered by physiological or psychological stressors. To gain insight into the distinct roles of the α2 and α3 subunits in the developing foetal brain, whose developmental dysfunction may be a predisposing factor of neurologic disorders, we compared the phenotypes of mouse foetuses with double homozygous knockout of Atp1a2 and Atp1a3 (α2α3-dKO) to those with single knockout. The brain haemorrhage phenotype of α2α3-dKO was similar to that of homozygous knockout of the gene encoding ascorbic acid (ASC or vitamin C) transporter, SVCT2. The α2α3-dKO brain showed significantly decreased level of ASC compared with the wild-type (WT) and single knockout. We found that the ASC content in the basal ganglia and cerebellum was significantly lower in the adult Atp1a3 heterozygous knockout mouse (α3-HT) than in the WT. Interestingly, we observed a significant decrease in the ASC level in the basal ganglia and cerebellum of α3-HT in the peripartum period, during which mice are under physiological stress. These observations indicate that the α2 and α3 subunits independently contribute to the ASC level in the foetal brain and that the α3 subunit contributes to ASC transport in the adult basal ganglia and cerebellum. We propose that decreases in ASC levels may affect neural network development and are linked to the pathophysiology of ATP1A2- and ATP1A3-related neurologic disorders.

Preventive and Therapeutic Potential of Vitamin C in Mental Disorders

In this review, we summarize the involvement of vitamin C in mental disorders by presenting available evidence on its pharmacological effects in animal models as well as in clinical studies. Vitamin C, especially its reduced form, has gained interest for its multiple functions in various tissues and organs, including central nervous system (CNS). Vitamin C protects the neuron against oxidative stress, alleviates inflammation, regulates the neurotransmission, affects neuronal development and controls epigenetic function. All of these processes are closely associated with psychopathology. In the past few decades, scientists have revealed that the deficiency of vitamin C may lead to motor deficit, cognitive impairment and aberrant behaviors, whereas supplement of vitamin C has a potential preventive and therapeutic effect on mental illness, such as major depressive disorder (MDD), schizophrenia, anxiety and Alzheimer's disease (AD). Although several studies support a possible role of vitamin C against mental disorders, more researches are essential to accelerate the knowledge and investigate the mechanism in this field.

Vitamin C Deficiency Causes Severe Defects in the Development of the Neonatal Cerebellum and in the Motor Behaviors of Gulo(-/-) Mice

AIMS

The developing brain of a neonate is particularly susceptible to damage by vitamin C deficiency because of its rapid growth and immature antioxidant system. Cognitive impairment and sensory motor deficits are found in the adult brain upon vitamin C deficiency. Therefore, the aim of this study was to clarify the role of vitamin C in its own right and its related mechanisms in Gulo(-/-) mice incapable of synthesizing vitamin C.

RESULTS

When vitamin C supplementation was ceased for 2 weeks until delivery, stillbirths and a significant reduction in neonatal mice were observed and the growth of neonates was remarkably decreased. In addition, intraparenchymal hemorrhages were found in most of the brains, especially in the stillborn neonates. In addition, the levels of malondialdehyde (MDA) and 8-isoprostanes were increased and structural abnormalities were found in the cortex, hippocampus, and cerebellum. Especially, vitamin C deficiency caused the failure of or a delay in the formation of cerebellar fissures accompanied by abnormal foliation and altered Purkinje cell alignment. In the developed adult brains from vitamin C-deficient Gulo(-/-) mice, the levels of glutathione, MDA, nitrate, IL-6, TNF-α, and Bax were increased and the expression of the GABRA6 and calbindin-28k was decreased. Due to atrophy of the granule and Purkinje cells, the motor behavior of vitamin C-deficient Gulo(-/-) mice declined.

INNOVATION AND CONCLUSION

Vitamin C deficiency during gestation induces intraparenchymal hemorrhages and severe defects in the development of the cerebellum. In fully developed brains, it induces the functional impairment by altering the cellular composition in the cerebellum.

Does vitamin C deficiency promote fatty liver disease development?

Obesity and the subsequent reprogramming of the white adipose tissue are linked to human disease-complexes including metabolic syndrome and concurrent non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). The dietary imposed dyslipidemia promotes redox imbalance by the generation of excess levels of reactive oxygen species and induces adipocyte dysfunction and reprogramming, leading to a low grade systemic inflammation and ectopic lipid deposition, e.g., in the liver, hereby promoting a vicious circle in which dietary factors initiate a metabolic change that further exacerbates the negative consequences of an adverse life-style. Large epidemiological studies and findings from controlled in vivo animal studies have provided evidence supporting an association between poor vitamin C (VitC) status and propagation of life-style associated diseases. In addition, overweight per se has been shown to result in reduced plasma VitC, and the distribution of body fat in obesity has been shown to have an inverse relationship with VitC plasma levels. Recently, a number of epidemiological studies have indicated a VitC intake below the recommended daily allowance (RDA) in NAFLD-patients, suggesting an association between dietary habits, disease and VitC deficiency. In the general population, VitC deficiency (defined as a plasma concentration below 23 μM) affects around 10% of adults, however, this prevalence is increased by an adverse life-style, deficiency potentially playing a broader role in disease progression in specific subgroups. This review discusses the currently available data from human surveys and experimental models in search of a putative role of VitC deficiency in the development of NAFLD and NASH.

Ascorbic acid and the brain: rationale for the use against cognitive decline

This review is focused upon the role of ascorbic acid (AA, vitamin C) in the promotion of healthy brain aging. Particular attention is attributed to the biochemistry and neuronal metabolism interface, transport across tissues, animal models that are useful for this area of research, and the human studies that implicate AA in the continuum between normal cognitive aging and age-related cognitive decline up to Alzheimer’s disease. Vascular risk factors and comorbidity relationships with cognitive decline and AA are discussed to facilitate strategies for advancing AA research in the area of brain health and neurodegeneration.