The Developmental Vitamin D (DVD) Model of Schizophrenia

Developmental vitamin D-deficiency produces autism-relevant behaviours and gut-health associated alterations in a rat model

Developmental vitamin D (DVD)-deficiency is an epidemiologically established risk factor for autism. Emerging studies also highlight the involvement of gut microbiome/gut physiology in autism. The current study aims to examine the effect of DVD-deficiency on a broad range of autism-relevant behavioural phenotypes and gut health. Vitamin D deficient rat dams exhibited altered maternal care, DVD-deficient pups showed increased ultrasonic vocalizations and as adolescents, social behaviour impairments and increased repetitive self-grooming behaviour. There were significant impacts of DVD-deficiency on gut health demonstrated by alterations to the microbiome, decreased villi length and increased ileal propionate levels. Overall, our animal model of this epidemiologically validated risk exposure for autism shows an expanded range of autism-related behavioural phenotypes and now alterations in gut microbiome that correlate with social behavioural deficits raising the possibility that DVD-deficiency induced ASD-like behaviours are due to alterations in gut health.

Maternal vitamin D supplementation and treadmill exercise attenuated vitamin D deficiency-induced anxiety-and depressive-like behaviors in adult male offspring rats

BACKGROUND

Vitamin D is a vital neuroactive steroid for brain development and function. Vitamin D deficiency is a worldwide health problem, particularly in children and women. Gestational or developmental vitamin D deficiency is associated with an increased risk of neurodevelopmental and neuropsychiatric disorders. This study examined the effect of maternal vitamin D dietary manipulations and treadmill exercise on anxiety-and depressive-related behaviors, pro-inflammatory cytokines, and prefrontal cortex (PFC) protein levels of brain-derived neurotrophic factor (BDNF) and vitamin D receptor (VDR) in adult male offspring born to vitamin D-deficient diet (VDD)-fed dams.

METHODS AND RESULTS

Female rats were provided standard diet (SD) or VDD for six weeks and then were treated with SD (started a week before mating throughout gestation and lactation) and treadmill exercise (a week before mating until gestational day 20). Male offspring were separated on postnatal day (PND) 21 and fed SD chow until PND90. Our results demonstrated that maternal vitamin D deficiency increased anxiety and depression-related behaviors, increased levels of TNF-α and IL-1β in serum, and decreased prefrontal protein expressions of BDNF and VDR in adult male offspring. However, maternal vitamin D supplementation and treadmill exercise reversed these changes alone or in combination.

CONCLUSION

It seems that developmental vitamin D deficiency disrupts brain development and has a long-lasting effect on VDR and BDNF signaling in the rat brain resulting in neuropsychiatric disorders in offspring. Therefore, vitamin D supplementation and physical exercise are reasonable strategies to prevent these neurobehavioral impairments.

Vitamin D: Brain and Behavior

It has been 20 years since we first proposed vitamin D as a "possible" neurosteroid.^{( 1 )} Our work over the last two decades, particularly results from our cellular and animal models, has confirmed the numerous ways in which vitamin D differentiates the developing brain. As a result, vitamin D can now confidently take its place among all other steroids known to regulate brain development.^{( 2 )} Others have concentrated on the possible neuroprotective functions of vitamin D in adult brains. Here these data are integrated, and possible mechanisms outlined for the various roles vitamin D appears to play in both developing and mature brains and how such actions shape behavior. There is now also good evidence linking gestational and/or neonatal vitamin D deficiency with an increased risk of neurodevelopmental disorders, such as schizophrenia and autism, and adult vitamin D deficiency with certain degenerative conditions. In this mini-review, the focus is on what we have learned over these past 20 years regarding the genomic and nongenomic actions of vitamin D in shaping brain development, neurophysiology, and behavior in animal models. © 2020 The Author. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Prenatal vitamin D deficiency does not exacerbate behavioural impairments associated with prenatal ethanol exposure in juvenile male mice

There is a high prevalence of vitamin D deficiency and exposure to low levels of ethanol in pregnant women. However, there are a paucity of studies that have addressed the impact of both vitamin D deficiency and ethanol exposure on the offspring's vulnerability to neurodevelopmental disorders later in life. The aim of this study was to examine whether the absence of vitamin D during gestation in mice would alter the effects of prenatal exposure to low dose ethanol on the behaviour and dopaminergic gene expression patterns of juvenile mice. Four-week old female C57BL/6J mice were placed on a prenatal vitamin D deficient (PVD) or standard diet for 6 weeks and mated at 10 weeks of age. Females were exposed to either 10%(v/v) ethanol or water between gestational days 0-8 and all were offered water thereafter. We found that blood ethanol concentration in the dams was not affected by maternal diet. Behavioural analyses of the offspring included ultrasonic vocalizations (USV) at postnatal day (P) 7, locomotion and social interaction at P21. The main findings were increased USV calling rate and impaired social interaction in males with prenatal ethanol exposure (PrEE). Gene expression analysis of transcripts involved in dopamine regulation revealed a main effect of ethanol exposure on dopamine- and cyclic adenosine monophosphate- regulated neuronal phosphoprotein (Darpp-32), a main effect of vitamin D diet on Dopamine 2 Receptors (D2R) and a main effect of Sex on Tyrosine Hydroxylase (TH) expression. The combination of PVD-PrEE did not exacerbate the alterations resulting from PVD or PrEE. Despite the limited evidence to support the interaction of PVD and PrEE during the postnatal period, males were more vulnerable than female offspring to the detrimental effects of PrEE. Therefore, based on these studies in mice we suggest that maintenance of optimal vitamin D levels and abstinence from ethanol during pregnancy would reduce risk of later disruption to brain function and behaviour in the offspring.

Developmental vitamin D deficiency alters multiple neurotransmitter systems in the neonatal rat brain

BACKGROUND

Epidemiological evidence suggests that developmental vitamin D (DVD) deficiency is a risk factor for neuropsychiatric disorders, such as schizophrenia. DVD deficiency in rats is associated with altered brain structure and adult behaviours indicating alterations in dopamine and glutamate signalling. Developmental alterations in dopamine neurotransmission have also been observed in DVD-deficient rats but a comprehensive assessment of brain neurochemistry has not been undertaken. Thus, the current study determined the regional concentrations of dopamine, noradrenaline, serotonin, glutamine, glutamate and γ-aminobutyric acid (GABA), and associated metabolites, in DVD-deficient neonates.

METHODS

Sprague-Dawley rats were fed a vitamin D deficient diet or control diet six weeks prior to mating until birth and housed under UVB-free lighting conditions. Neurotransmitter concentration was assessed by high-performance liquid chromatography on post-mortem neonatal brain tissue.

RESULTS

Ubiquitous reductions in the levels of glutamine (12-24%) were observed in DVD-deficient neonates compared with control neonates. Similarly, in multiple brain regions DVD-deficient neonates had increased levels of noradrenaline and serine compared with control neonates. In contrast, increased levels of dopamine and decreased levels of serotonin in DVD-deficient neonates were limited to striatal subregions compared with controls.

CONCLUSIONS

Our results confirm that DVD deficiency leads to changes in multiple neurotransmitter systems in the neonate brain. Importantly, this regionally-based assessment in DVD-deficient neonates identified both widespread neurotransmitter changes (glutamine/noradrenaline) and regionally selective neurotransmitter changes (dopamine/serotonin). Thus, vitamin D may have both general and local actions depending on the neurotransmitter system being investigated. Taken together, these data suggest that DVD deficiency alters neurotransmitter systems relevant to schizophrenia in the developing rat brain.

Vitamin D regulates tyrosine hydroxylase expression: N-cadherin a possible mediator

Vitamin D is a neuroactive steroid. Its genomic actions are mediated via the active form of vitamin D, 1,25(OH)2D3, binding to the vitamin D receptor (VDR). The VDR emerges in the rat mesencephalon at embryonic day 12, representing the peak period of dopaminergic cell birth. Our prior studies reveal that developmental vitamin D (DVD)-deficiency alters the ontogeny of dopaminergic neurons in the developing mesencephalon. There is also consistent evidence from others that 1,25(OH)2D3 promotes the survival of dopaminergic neurons in models of dopaminergic toxicity. In both developmental and toxicological studies it has been proposed that 1,25(OH)2D3 may modulate the differentiation and maturation of dopaminergic neurons; however, to date there is lack of direct evidence. The aim of the current study is to investigate this both in vitro using a human SH-SY5Y cell line transfected with rodent VDR and in vivo using a DVD-deficient model. Here we show that in VDR-expressing SH-SY5Y cells, 1,25(OH)2D3 significantly increased production of tyrosine hydroxylase (TH), the rate-limiting enzyme in dopamine synthesis. This effect was dose- and time-dependent, but was not due to an increase in TH-positive cell number, nor was it due to the production of trophic survival factors for dopamine neurons such as glial-derived neurotrophic factor (GDNF). In accordance with 1,25(OH)2D3's anti-proliferative actions in the brain, 1,25(OH)2D3 reduced the percentage of dividing cells from approximately 15-10%. Given the recently reported role of N-cadherin in the direct differentiation of dopaminergic neurons, we examined here whether it may be elevated by 1,25(OH)2D3. We confirmed this in vitro and more importantly, we showed DVD-deficiency decreases N-cadherin expression in the embryonic mesencephalon. In summary, in our in vitro model we have shown 1,25(OH)2D3 increases TH expression, decreases proliferation and elevates N-cadherin, a potential factor that mediates these processes. Accordingly all of these findings are reversed in the developing brain in our DVD-deficiency model. Remarkably our findings in the DVD-deficiency model phenocopy those found in a recent model where N-cadherin was regionally ablated from the mesencephalon. This study has, for the first time, shown that vitamin D directly modulates TH expression and strongly suggests N-cadherin may be a plausible mediator of this process both in vitro and in vivo. Our findings may help to explain epidemiological data linking DVD deficiency with schizophrenia.