Vitamin D deficiency exacerbates experimental stroke injury and dysregulates ischemia-induced inflammation in adult rats

Vitamin D, arterial hypertension & cerebrovascular disease

Vitamin D is mainly derived from endogenous ultraviolet-B induced vitamin D synthesis in the skin, and the current high prevalence of vitamin D deficiency can, therefore, largely be attributed to lifestyle related low sunlight exposure. Regulation of bone and mineral metabolism is a classic vitamin D effect, but the identification of the vitamin D receptor (VDR) in almost all human cells suggests a role for vitamin D also in extra-skeletal diseases. Experimental studies demonstrated several antihypertensive and vascular protective effects of vitamin D, such as suppression of the renin angiotensin aldosterone system, beneficial modulation of classic cardiovascular risk factors, and anti-atherosclerotic properties including improvements of endothelial function. Additional neuroprotective actions of vitamin D have also been reported. In line with this, epidemiological studies have largely shown that vitamin D deficiency is an independent risk factor for arterial hypertension and strokes. Data from randomized controlled trials (RCTs) are, however, limited and less promising, with currently no confirmation that vitamin D reduces stroke incidence. Whereas some RCTs suggest that vitamin D supplementation might modestly reduce blood pressure, this has not been consistently observed in all studies. It is, therefore, premature to recommend vitamin D supplementation for the prevention and treatment of arterial hypertension and stroke. Nevertheless, the fact that patients with arterial hypertension and cerebrovascular disease are at a relatively high risk of vitamin D deficiency, and therewith associated musculoskeletal diseases can serve as a rationale for the evaluation, prevention and treatment of vitamin D deficiency in these patients.

Revisiting the timing hypothesis: biomarkers that define the therapeutic window of estrogen for stroke

Significantly extended life expectancy coupled with contemporary sedentary lifestyles and poor nutrition has created a global epidemic of cardiovascular disease and stroke. For women, this issue is complicated by the discrepant outcomes of hormone therapy (HT) for stroke incidence and severity as well as the therapeutic complications for stroke associated with advancing age. Here we propose that the impact of estrogen therapy cannot be considered in isolation, but should include age-related changes in endocrine, immune, and nucleic acid mediators that collaborate with estrogen to produce neuroprotective effects commonly seen in younger, healthier demographics. Due to their role as modulators of ischemic cell death, the post-stroke inflammatory response, and neuronal survival and regeneration, this review proposes that Insulin-like Growth Factor (IGF)-1, Vitamin D, and discrete members of the family of non-coding RNA peptides called microRNAs (miRNAs) may be crucial biochemical markers that help determine the neuroprotective "window" of HT. Specifically, IGF-1 confers neuroprotection in concert with, and independently of, estrogen and failure of the insulin/IGF-1 axis is associated with metabolic disturbances that increase the risk for stroke. Vitamin D and miRNAs regulate and complement IGF-1 mediated function and neuroprotective efficacy via modulation of IGF-1 availability and neural stem cell and immune cell proliferation, differentiation and secretions. Together, age-related decline of these factors differentially affects stroke risk, severity, and outcome, and may provide a novel therapeutic adjunct to traditional HT practices.

The transcriptomic response of mixed neuron-glial cell cultures to 1,25-dihydroxyvitamin d3 includes genes limiting the progression of neurodegenerative diseases

Seasonal or chronic vitamin D deficiency and/or insufficiency is highly prevalent in the human population. Receptors for 1,25-dihydroxyvitamin D3, the hormonal metabolite of vitamin D, are found throughout the brain. To provide further information on the role of this hormone on brain function, we analyzed the transcriptomic profiles of mixed neuron-glial cell cultures in response to 1,25-dihydroxyvitamin D3. 1,25-dihydroxyvitamin D3 treatment increases the mRNA levels of 27 genes by at least 1.9 fold. Among them, 17 genes were related to neurodegenerative and psychiatric diseases, or brain morphogenesis. Notably, 10 of these genes encode proteins potentially limiting the progression of Alzheimer's disease. These data provide support for a role of 1,25-dihydroxyvitamin D3 in brain disease prevention. The possible consequences of circannual or chronic vitamin D insufficiencies on a tissue with a low regenerative potential such as the brain should be considered.

Combination treatment with progesterone and vitamin D hormone is more effective than monotherapy in ischemic stroke: the role of BDNF/TrkB/Erk1/2 signaling in neuroprotection

We investigated whether combinatorial post-injury treatment with progesterone (P4) and vitamin D hormone (VDH) would reduce ischemic injury more effectively than P4 alone in an oxygen glucose deprivation (OGD) model in primary cortical neurons and in a transient middle cerebral artery occlusion (tMCAO) model in rats. In the OGD model, P4 and VDH each showed neuroprotection individually, but combination of the "best" doses did not show substantial efficacy; instead, the lower dose of VDH in combination with P4 was the most effective. In the tMCAO model, P4 and VDH were given alone or in combination at different times post-occlusion for 7 days. In vivo data confirmed the in vitro findings and showed better infarct reduction at day 7 and functional outcomes (at 3, 5 and 7 days post-occlusion) after combinatorial treatment than when either agent was given alone. VDH, but not P4, upregulated heme oxygenase-1, suggesting a pathway for the neuroprotective effects of VDH differing from that of P4. The combination of P4 and VDH activated brain-derived neurotrophic factor and its specific receptor, tyrosine kinase receptor-B. Under specific conditions VDH potentiates P4's neuroprotective efficacy and should be considered as a potential partner of P4 in a low-cost, safe and effective combinatorial treatment for stroke.