Canadian recommendations for vitamin D intake for persons affected by multiple sclerosis

In 2016, the Multiple Sclerosis (MS) Society of Canada convened a panel of expert scientists, clinicians and patient advocate to review the evidence for an association between vitamin D status and MS prevention and/or disease modification. The goal was to develop clear and accurate recommendations on optimal vitamin D intake and status for people affected by MS for use in clinical practice and public health policy. The final consensus report was based on a review and grading of existing published papers combined with expert opinions of panel members. The report led to recommendations published in November of 2018 on the website of the MS Society of Canada, one in a format for use by health professionals and another in a question and answer format that was targeted to persons affected by MS and the general public. For people at risk of developing MS, the vitamin D recommendations are similar to those for the general public following the Dietary Reference Intakes (DRI) for Canada and the United States. Adults should achieve and maintain a normal vitamin D status with monitoring by physicians (serum 25-hydroxyvitamin D (25(OH)D) = 50-125 nmol/L, requiring 600-4000 IU vitamin D/d intake). For pregnant women, newborn infants, and all youth at risk of MS, vitamin D intakes should also follow DRI recommendations but additionally their serum 25-(OH)D should be monitored. For persons living with MS, existing evidence did not allow prediction of a vitamin D intake that might modify MS disease course. For this group the recommendations included: (1) serum 25-(OH)D should be maintained in the range of 50-125 nmol/L (600-4000 IU/d intake).; and (2) vitamin D should not be used as a standalone treatment for MS. For children and adolescents, serum 25OHD status was recommended to be measured upon diagnosis of a first clinical demyelinating event, and monitored every 6 months to achieve a target of 75 nmol/L Since people living with MS are at increased risk of osteoporosis, falls, and bone fractures, it was recommended to achieve a minimum serum 25OHD concentration that is protective for bone health in the general population. The revision of the MS Society recommendations on vitamin D awaits future clinical trial evidence.

Vitamin D deficiency in Kazakhstan: Cross-Sectional study

Vitamin D deficiency (VDD) is one of the serious and highly debatable public health problems affecting at least one billion of world population. This study objected to evaluate Vitamin D status in adult population of both sexes residing in different geographical areas of Kazakhstan and to elucidate the possible contributing factors related to VDD. This cross-sectional study covered 6 regions of Kazakhstan and applied the systematic random sampling to recruit 1347 healthy adults (of whom 819 were females) with mean age 44 ± 14 years. The concentration of 25-hydroxy vitamin D (25-OHD) was measured from May 2018 to August 2018 with Architect 25OH Vitamin D assay (Abbott Ireland Diagnostics Division Lisnamuck, Longford Co. Longford Ireland). Vitamin D deficiency was defined as 25-OHD values not exceeding 20 ng/mL as a reference threshold in healthy population. The median serum 25(OH)D concentrations in all studied regions of Kazakhstan were below the reference threshold (20 ng/mL). The lowest range of vitamin D (<10 ng/mL) was observed more commonly in females (34.6 % - 283) as compared to males (16.7 % - 88) and was significantly higher in Asians (33.2 % - 352) in contrast with Caucasians (6.7 % - 19) (χ2 = 177,939; D.f. = 3; p-value=<0,001). The proportion of severe VDD was higher in individuals with low body mass index (31.1 % - 188) vs. individuals with high body mass index (18.7 % - 50). In this study individuals aged 60 years and older had the most favorable situation with 25-OHD concentrations since these were normal in 14.4 % of observations (χ2 = 26,589; D.f. = 6; p-value=<0001). Studying the prevalence of VDD is an important public health task. Further research is needed to understand the epidemiology of VDD in more details to tailor intervention programs.

Maternal vitamin D deficiency induces transcriptomic changes in newborn rat lungs

Vitamin D deficiency (VDD) during pregnancy is common and related to several maternal and fetal morbidities. Vitamin D (VD) plays a role in normal lung development and VDD causes abnormal airway, alveolar, and vascular growth in newborn rats. Here we use an unbiased transcriptomic approach to identify pathways altered in the lungs of offspring from VDD dams. The lungs of newborn offspring from VD replete and VDD dams were removed and RNA from these samples were analyzed using Affymetrix microarrays. Data were RMA normalized, differential gene expression was determined using Significance Analysis of Microarrays (5 % FDR) and pathway enrichment analysis was assessed. There were 2233 differentially expressed transcripts between the VDD and control lungs (1889 up, 344 down). Consistent with the suppression of lung growth in the VDD group, there were significant suppression of signal transduction pathways related to vascular biology and anabolic signaling pathways, e.g. the insulin-like growth factor-1 receptor (IGF-1R), fibroblast growth factor (FGF), cell cycle control. A major, enriched functional category was upregulation of pathways related to the innate immune system, including pathways for granulocyte and macrophage development, chemotaxis, and activation of cytokine signaling through Jak/Stat (e.g. resulting in higher IL1 α and β). We conclude that VDD during fetal development alters multiple pathways beyond the predicted angiogeneic alterations. These changes either contribute to, or reflect, the abnormal airway, alveolar, and vascular growth seen in the neonatal lung resulting from maternal VDD. The pattern also suggests abnormal lung development caused by maternal VDD creates a proinflammatory milieu that could contribute to the suppression of lung growth and development.

[Vitamin D in adolescents: summarizing guidelines for general practice]

Vitamin D plays a critical role in bone health in adolescence. Is screening and treatment of vitamin D deficiency therefore necessary at this age? Inspired by a clinical case, we try to answer this question by presenting a summary of worldwide recommendations for vitamin D in adolescents.

Genetic predisposition for vitamin D deficiency is not associated with adverse outcome of very low birth weight infants: A cohort study from the German Neonatal Network

Objective

Postnatal vitamin D supplementation is standard of care in neonates and preterm infants. Despite routine supplementation of vitamin D, a wide range of complications related to vitamin D deficiency has been described in the literature. Since standard vitamin D supplementation might be not sufficient in preterm infants with a genetic predisposition for vitamin D deficiency, we investigated the outcome of preterm infants with regard to their genetic estimated vitamin D levels.

Methods

Preterm infants with a birth weight below 1500 grams were included in the German Neonatal Network at the time of their birth and tested at the age of five. The vitamin D level was genetically calculated based on three single nucleotide polymorphisms (SNPs: rs12794714, rs7944926 and rs2282679) which alter vitamin D synthesis pathways. Specific alleles of these polymorphisms are validated markers for low plasma vitamin D levels. Outcome data were based on baseline data at the time of birth, typical complications of prematurity, body measurements at the age of five and occurrence of bone fractures. T-test and Fisher’s exact test were used for statistical comparison.

Results

According to their genetic predisposition, 1,924 preterm infants were divided into groups of low (gsVitD < 20. Percentile), intermediate and high vitamin D level estimates. Low genetic vitamin D level estimates could not be shown to be associated with any adverse outcome measures examined. The analyses covered data on aforementioned determinants.

Conclusion

Low genetic vitamin D level estimates could not be shown to be associated with previously described adverse outcome in preterm infants.

Roles of Vitamin D in Reproductive Systems and Assisted Reproductive Technology

Vitamin D, an essential steroid hormone in the human body, plays an important role in not only the regulation of calcium and phosphorus metabolism, but also in various physiological processes, such as cell differentiation and apoptosis, inflammation, and insulin resistance. Vitamin D receptors are widely distributed in male and female reproductive systems, suggesting that vitamin D is essential for fertility. Because vitamin D deficiency is highly prevalent around the world, this review aims to discuss the potential functions of vitamin D in male and female reproductive systems and the associations between vitamin D and assisted reproductive technology (ART) outcomes. Vitamin D is involved in many physiological reproductive processes, including steroidogenesis, spermatogenesis, and acrosome reaction. It is correlated with sperm quality, ovarian reserve, polycystic ovarian syndrome, and endometriosis, among others. Controversial clinical findings on vitamin D levels and ART outcomes were revealed in this review, and demonstrations of efficacy for human fertility in randomized controlled trials of vitamin D supplementation are notably lacking. Thus, further studies are highly required involving molecular mechanisms among different species and human populations, as well as randomized controlled trials.

Nutritional rickets: Historic overview and plan for worldwide eradication

Rickets was first described in great detail in the mid 17th century and was affecting a great number of children in major European cities. The disease, however, existed already in the Roman times. The etiology of this disease remained enigmatic until the 1920s when two different mechanisms, lack of exposure to sunlight and lack of a dietary factor were finally solved by the discovery of vitamin D and its dual origin. Soon thereafter, the implementation of vitamin D supplementation for all infants and small children largely eliminated nutritional rickets in Europe and North America. It took nearly a century to elucidate the complex chemistry, metabolism, mode and spectrum of activity of the vitamin D endocrine system. Nutritional rickets, whether due to simple vitamin D or calcium deficiency or both, remains widely ravaging many infants and children around the world. Asian countries and the Middle East are mainly confronted with vitamin D deficiency whereas many African and some Asian countries face calcium deficiency rickets. Immigrants and refugees or in general people with a darker skin living in moderate climate zone are also confronted with this disease. There is great consensus how this disease could be prevented or cured. In collaboration with most international professional societies, we prepare a memorandum, in line with the successful battle against iodine deficiency disorders, to convince the World Health Organization and its member states to start an implementation program to eradicate nutritional rickets by 2030.

Vitamin D Supplementation in Multiple Sclerosis: A Critical Analysis of Potentials and Threats

Multiple sclerosis (MS) is a chronic inflammatory demyelinating and neurodegenerative disease of the central nervous system (CNS). In recent years, vitamin D has gained attention, as low serum levels are suspected to increase the risk for MS. Cholecalciferol supplementation has been tested in several clinical trials, since hypovitaminosis D was linked to higher disease activity and may even play a role in long-term outcome. Here, we review the current understanding of the molecular effects of vitamin D beyond calcium homeostasis, the potential beneficial action in MS and hazards including complications of chronic and high-dose therapy. In clinical trials, doses of up to 40,000 IU/day were tested and appeared safe as add-on therapy for short-term periods. A recent meta-analysis of a randomized, double-blind, placebo-controlled clinical trial investigating vitamin D as add-on therapy in MS, however, suggested that vitamin D had no therapeutic effect on disability or relapse rate. We recognize a knowledge gap for chronic and high-dose therapy, which can lead to life-threatening complications related to vitamin D toxicity including renal failure, cardiac arrythmia and status epilepticus. Moreover, vitamin D toxicity may manifest as fatigue, muscle weakness or urinary dysfunction, which may mimic the natural course of progressive MS. Given these limitations, vitamin D supplementation in MS is a sensitive task which needs to be supervised by physicians. While there is strong evidence for vitamin D deficiency and the development of MS, the risk-benefit profile of dosage and duration of add-on supplementation needs to be further clarified.

Investigation of vitamin D levels in patients with Sudden Sensory-Neural Hearing Loss and its effect on treatment

BACKGROUND

Due to high prevalence of vitamin D deficiency and the possible association with Sudden Sensory-Neural Hearing Loss (SSNHL) finding the main causes and appropriate treatments are highly essential. This study aimed to investigate vitamin D levels in patients suffering SSNHL and its effect on response to treatment.

MATERIALS AND METHODS

This cross-sectional study was performed on two groups of case (34 SSNHL patients) and control (34 healthy subjects without risk of hearing loss). All patient information such as age, sex, audiogram illustration of hearing frequency and the level of vitamin D were recorded at baseline. Patients with SSNHL received routine treatments such as 10 days of 1 mg/kg/day steroid and the response or lack of complete response to treatment was recorded and analyzed according to the audiometry.

RESULTS

Vitamin D level in SSNHL group with a mean of 19.28 ± 9.56 ng/ml was significantly less than the control group (25.71 ± 11.21 ng/ml; P value < 0.001). After treatment, 76.5% were completely recovered and 23.5% did not recover completely. Factors such as age, sex and level of initial hearing loss did not have a significant effect on the response to treatment, but the level of vitamin D in these patients had a significant relationship with the response to treatment (P value = 0.004); so that all patients with sufficient vitamin D level had completely recovered, versus 87.5% of patients with vitamin D deficiency and 12.5% of insufficient vitamin D had no response to treatment.

CONCLUSION

According to the results of the present study, the prevalence of vitamin D deficiency in patients with SSNHL was more than healthy people. SSNHL patients with deficient vitamin D had the highest percentage of no response to treatment.

Low maternal vitamin D is associated with increased risk of congenital and peri/postnatal transmission of Cytomegalovirus in women with HIV

Background

CMV infection of the fetus or neonate can lead to devastating disease, and there are no effective prevention strategies to date. Vitamin D is a potent immunomodulator, supports antiviral immune responses, and plays an important role in placental immunity.

Methods

Retrospective cohort study to evaluate the impact of low maternal vitamin D on congenital and early postnatal transmission of CMV among HIV-infected, non-breastfeeding women and their HIV exposed but negative infants from an urban HIV clinic. Vitamin D panel was performed on stored maternal plasma obtained near time of delivery. Infant CMV testing at 0–6 months included urine and oral cultures, and/or serum polymerase chain reaction testing.

Results

Cohort included 340 mother-infant pairs (births 1991–2014). Among 38 infants (11%) with a CMV+ test between 0–6 months, 4.7% (14/300) had congenital CMV transmission (CMV+ test 0–3 weeks), and 7.6% (24/315) had peri/postnatal CMV (CMV+ test >3 weeks-6 months). Women with lower calcitriol (1,25-dihydroxyvitamin D), the active form of vitamin D, were more likely to have an infant with congenital (OR 12.2 [95% CI 1.61–92.2] P = 0.02) and peri/postnatal (OR 9.84 [95% CI 2.63–36.8] P = 0.0007) infections in multivariate analyses, independent of maternal HIV viral load and CD4 count.

Conclusion

This study demonstrates an association between inadequate maternal calcitriol during pregnancy and increased congenital and early postnatal acquisition of CMV among non-breastfeeding women with HIV and their HIV negative infants.

Acute Responses to Low and High Intensity Exercise in Type 1 Diabetic Adolescents in Relation to Their Level of Serum 25(OH)D

The main purpose of this study was to investigate the differences in glycaemic reaction in response to various physical activities in 20 young boys (14.4 ± 1.6 years) with type 1 diabetes mellitus (T1DM) and with either vitamin D deficiency or with suboptimal levels of vitamin D. Participants were divided into two groups (deficiency group-DG, n = 10; suboptimal group-SG, n = 10) according to their vitamin D levels. All patients performed aerobic and mixed (aerobic-anaerobic) physical efforts. During the exercise, the respiratory responses and glucose levels were monitored. Biochemical blood analyses were performed before each physical effort. The oxygen consumption was not significantly lower in SG during both aerobic and mixed effort (4.0% and 5.6%, respectively). The glycated haemoglobin (HbA1c) level was higher by 6.1% and the total daily dose of insulin (DDI) was higher by 18.4% in the DG. The differences were not statistically significant. Patients with lower vitamin D levels demonstrated an insignificantly higher glycaemic variability during days with both aerobic and mixed exercises. An appropriate vitamin D concentration in T1DM patients' blood may constitute a prophylactic factor for hyperglycaemia during anaerobic training and hypoglycaemia during aerobic training.

Epimers of Vitamin D: A Review

In this review, we discuss the sources, formation, metabolism, function, biological activity, and potency of C3-epimers (epimers of vitamin D). We also determine the role of epimerase in vitamin D-binding protein (DBP) and vitamin D receptors (VDR) according to different subcellular localizations. The importance of C3 epimerization and the metabolic pathway of vitamin D at the hydroxyl group have recently been recognized. Here, the hydroxyl group at the C3 position is orientated differently from the alpha to beta orientation in space. However, the details of this epimerization pathway are not yet clearly understood. Even the gene encoding for the enzyme involved in epimerization has not yet been identified. Many published research articles have illustrated the biological activity of C3 epimeric metabolites using an in vitro model, but the studies on in vivo models are substantially inadequate. The metabolic stability of 3-epi-1α,25(OH)₂D3 has been demonstrated to be higher than its primary metabolites. 3-epi-1 alpha, 25 dihydroxyvitamin D3 (3-epi-1α,25(OH)₂D3) is thought to have fewer calcemic effects than non-epimeric forms of vitamin D. Some researchers have observed a larger proportion of total vitamin D as C3-epimers in infants than in adults. Insufficient levels of vitamin D were found in mothers and their newborns when the epimers were not included in the measurement of vitamin D. Oral supplementation of vitamin D has also been found to potentially cause increased production of epimers in mice but not humans. Moreover, routine vitamin D blood tests for healthy adults will not be significantly affected by epimeric interference using LC-MS/MS assays. Recent genetic models also show that the genetic determinants and the potential factors of C3-epimers differ from those of non-C3-epimers.Most commercial immunoassays techniques can lead to inaccurate vitamin D results due to epimeric interference, especially in infants and pregnant women. It is also known that the LC-MS/MS technique can chromatographically separate epimeric and isobaric interference and detect vitamin D metabolites sensitively and accurately. Unfortunately, many labs around the world do not take into account the interference caused by epimers. In this review, various methods and techniques for the analysis of C3-epimers are also discussed. The authors believe that C3-epimers may have an important role to play in clinical research, and further research is warranted.

Targeting Vitamin D Deficiency to Limit Exacerbations in Respiratory Diseases: Utopia or Strategy With Potential?

Patients with respiratory diseases such as cystic fibrosis, chronic obstructive pulmonary disease, or asthma often experience an acute worsening of respiratory symptoms, termed exacerbations. Although the course of exacerbations is disease specific, they are mostly triggered by a respiratory infection. Exacerbations often require hospitalization and are an important cause of mortality. Treatments of exacerbations aim to minimize the negative impact and to prevent subsequent events. Despite many existing therapy options, many patients do not benefit from therapy and suffer from recurrent events. Vitamin D deficiency is a worldwide problem and is extremely prevalent in these patients. Vitamin D, known for its calcemic effects, also has immunomodulatory and anti-infectious actions and can therefore be a possible agent to treat or prevent exacerbations. This review will focus on vitamin D as a potential candidate to treat or prevent exacerbations in CF, COPD, and asthma.

Vitamin D Deficiency Is Associated With Metabolic Risk Factors in Women With Polycystic Ovary Syndrome: A Cross-Sectional Study in Shaanxi China

Background: Polycystic ovary syndrome (PCOS) is a common endocrine disorder in women at reproductive age, which is characterized by obesity, hyperandrogenemia, and insulin resistance (IR). This study aimed to investigate the vitamin D status, and analyze the relationship between vitamin D deficiency and metabolic risk factors in PCOS women in Shaanxi China. Methods: A cross-sectional study included 169 women diagnosed with PCOS and 114 control women without PCOS. The serum 25(OH)D and metabolic markers were measured. Vitamin D deficiency was defined as serum 25(OH)D concentration less than 20 ng/mL. The primary outcome was the difference in vitamin D status between the PCOS and control groups, the secondary outcomes were correlations between serum 25(OH)D concentration and metabolic risk factors in women with PCOS. Results: The serum 25(OH)D concentration was significantly lower in women with PCOS than in controls (P < 0.05), and the prevalence rates of 25(OH)D deficiency and insufficiency were significantly higher in women with PCOS than in controls (P < 0.05). The serum 25(OH)D concentration was significantly lower in PCOS women with obesity or IR than in women without obesity or IR (P < 0.05), and the prevalence of 25(OH)D deficiency in PCOS women with obesity or IR was significantly higher than in women without obesity or IR (P < 0.05). Serum 25(OH)D concentration was significantly negatively correlated with body mass index (BMI), waist-to-hip ratio (WHR), fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR), total cholesterol, low-density lipoprotein cholesterol (LDL-C), and high-sensitivity C-reactive protein (hs-CRP) (P < 0.05). In comparison, serum 25(OH)D concentration was significantly positively correlated with high-density lipoprotein cholesterol (HDL-C) (P < 0.05). Increased BMI and WHR, high levels of fasting insulin, HOMA-IR, total cholesterol, LDL-C and hs-CRP were regarded as risk factors, but high level of HDL-C was considered to be protective factor of vitamin D deficiency in PCOS women. Conclusions: Vitamin D deficiency is prevalent in PCOS women in Shaanxi China, especially in those with obesity and IR. The serum 25(OH)D level was correlated with metabolic risk factors in PCOS women. Multi-center randomized controlled trials with large sample sizes are needed to probe the metabolic effect of vitamin D supplementation in PCOS women.

Effects of vitamin D supplementation in women with polycystic ovary syndrome: a review

Increasing evidence supports the contribution of vitamin D deficiency (VDD) in metabolic disturbances among women with polycystic ovary syndrome (PCOS). This review aims to assess the associations between vitamin D levels and metabolic/endocrine dysregulations and to determine the effects of vitamin D supplementation on glucose metabolism, insulin sensitivity, lipid profile, and hormones functionality in PCOS patients. We searched in PubMed human randomized controlled trials (RCTs) published in English between 2016 and 2019 on the effects of vitamin D supplementation on PCOS. Nine studies were included and analyzed. Vitamin D supplementation restored physiological serum 25(OH)D levels in PCOS women in all the studies included. In six studies, it significantly decreased fasting plasma glucose and brought to improvements in insulin resistance (IR) and serum fasting insulin. In addition, four studies reported decreases of serum triglycerides, while discordant data are reported as far as LDL, HDL, and total cholesterol levels. High-doses of vitamin D (4000 IU), compared with low-dose (1000 IU), and placebo, showed beneficial effects on total testosterone, sex hormone-binding globulin (SHBG) and free androgen index (FAI). Vitamin D supplementation at high doses for a period of at least 12 weeks, may lead to improvement in terms of glucose level, insulin sensitivity, hyperlipidemia, and hormonal functionality in PCOS women.

Vitamin D in Follicular Fluid Correlates With the Euploid Status of Blastocysts in a Vitamin D Deficient Population

CONTEXT

The widespread distribution of the Vitamin D (VitD) receptor in reproductive tissues suggests an important role for VitD in human reproduction. The assessment of patient´s VitD is based on the 25-hydroxyvitamin D (25(OH)D) metabolite measurement. However, most of the circulating 25(OH)D is bound to either VitD-binding protein (VDBP) (88%) or albumin (12%) and less than 1% circulates free.

OBJECTIVE

To determine a possible correlation between VitD levels in serum (S) and follicular fluid (FF) and blastocyst ploidy status in patients undergoing infertility treatment.

METHODS

A prospective observational study was performed including couples planned for preimplantation genetic testing for aneuploidies (PGT-A) from ART Fertility Clinics. Patients were classified according to their 25(OH)D-Serum levels: VitD deficient group <20 ng/ml and insufficient/replete ≥20 ng/ml defined as VitD non-deficient group.

RESULTS

Serum samples and 226 FF from individual follicles were collected for 25(OH)D, bioavailable 25(OH)D, free 25(OH)D, and % free 25(OH)D measurement. 25(OH)D-Serum in VitD deficient and non-deficient were 13.2±4.0 ng/ml vs 32.3±9.2 ng/ml; p<0.001. FF from 40 and 74 biopsied blastocysts was analysed of which 52.5 and 60.8% were euploid (p = 0.428), respectively. In VitD deficient patients, mean 25(OH)D-FF, bioavailable 25(OH)D-FF, and free 25(OH)D-FF were higher in euploid vs aneuploid blastocysts (18.3±6.3 ng/ml vs 13.9±4.8 ng/ml; p = 0.040; 1.5±0.5 ng/ml vs 1.1±0.4 ng/ml; p = 0.015; 0.005±0.002 ng/ml vs 0.003±0.001 ng/ml; p = 0.023, respectively), whilst no differences were found in VitD non-deficient patients (37.9±12.3 ng/ml vs 40.6±13.7 ng/ml; p = 0.380; 3.1±1.1 ng/ml vs 3.3±1.2 ng/ml; p = 0.323; 0.01±0.003 ng/ml vs 0.01±0.004 ng/ml; p = 0.319, respectively).

CONCLUSION

VitD non-deficient patients have a significantly higher probability of obtaining a euploid blastocyst compared to VitD deficient patients (OR:33.36, p = 0.002).

Melanin has a Small Inhibitory Effect on Cutaneous Vitamin D Synthesis: A Comparison of Extreme Phenotypes

Epidemiology suggests that melanin inhibits cutaneous vitamin D₃ synthesis by UVR. Laboratory investigations assessing the impact of melanin on vitamin D production have produced contradictory results. We determined the effect of melanin on vitamin D₃ photosynthesis in healthy young volunteers (n = 102) of Fitzpatrick skin types II-VI (white to black). Participants, irrespective of skin type, were exposed to the same suberythemal UVR dose, to 85% body surface area, using solar simulated UVR or narrowband UVB (311 nm). This was repeated five times with intervals of 3-4 days between UVR exposures. Blood was taken before, during, and after the irradiation and assessed for serum 25-hydroxyvitamin D₃ (25[OH]D₃) as a marker of vitamin D₃ status. Linear UVR dose-dependent increases in 25(OH)D₃ were highly significant (P ≤ 7.7 x 10^-11). The ratios of regression slopes of the different skin type groups were compared, and only skin type II was significantly steeper than the other groups. Comparisons between extreme skin types II and VI showed melanin inhibition factors of approximately 1.3-1.4, depending on the UVR source. We conclude that the inhibitory effect of melanin on vitamin D₃ synthesis is small, compared with erythema, but that this difference may be sufficient to explain the epidemiological data.

Vitamin D deficiency induces the excitation/inhibition brain imbalance and the proinflammatory shift

Vitamin D₃ is among the major neurosteroids whose role in developing and adult brain is intensively studied now. Its active form 1,25(OH)₂D₃ regulates the expression and functioning of a range of brain-specific proteins, which orchestrate the neurotransmitter turnover, neurogenesis and neuroplasticity. Despite numerous studies of the vitamin D role in normal and pathological brain function, there is little evidence on the mechanisms of alterations in excitatory and inhibitory neurotransmission under vitamin D deficiency (VDD). Using the animal model we characterized the dysfunction of excitatory and inhibitory neurotransmission under alimentary VDD. The shift between unstimulated and evoked GABA release under VDD was largely reversed after treatment of VDD, whereas the impairments in glutamatergic system were only partially recovered after 1-month vitamin D₃ supplementation. The increase of the external glutamate level and unstimulated GABA release in brain nerve terminals was associated with intensified ROS production and higher [Ca²⁺]_i in presynapse. The negative allosteric modulation of presynaptic mGlu7 receptors significantly enhanced exocytotic GABA release, which was decreased under VDD, thereby suggesting the neuroprotective effect of such modulation of inhibitory neurotransmission. Synaptic plasma membranes and cytosolic proteins contribute to the decreased stimulated release of neurotransmitter, by being the crucial components, whose functional state is impaired under VDD. The critical changes with synaptic vesicles occurred at the docking step of the process, whereas malfunctioning of synaptic cytosolic proteins impacted the fusion event foremost. The decreased amplitude of exocytosis was inherent for non-excitable cells as well, as evidenced by lower platelet degranulation. Our data suggest the presynaptic dysfunction and proinflammatory shift as the early events in the pathogenesis of VDD-associated disorders and provide evidences for the neuroprotective role of vitamin D₃.

Impact of Vitamin D on Physical Efficiency and Exercise Performance-A Review

Vitamin D deficiency amongst athletes and the general population seems to be a prominent problem. The most recognized role of vitamin D is its regulation of calcium homeostasis; there is a strong relationship between vitamin D and bone health. Moreover, its concentrations are associated with muscle function and immune response in both the general and athletic populations. Vitamin D level is strongly connected with the presence of VDRs (vitamin D receptors) in most human extraskeletal cells. Expression of multiple myogenic transcription factors enhancing muscle cell proliferation and differentiation is caused by an exposure of skeletal muscles to vitamin D. The aim of this review is to summarize current understanding of the significance of vitamin D on exercise performance and physical efficiency, as well to analyze the impact of vitamin D on multiple potential mechanisms. More high-quality research studies, considering free 25(OH)D as a better marker of vitamin D status, the baseline level of 25(OH)D and multiple pathways of vitamin D acting and usage in athletes are required.

Developmental Vitamin D Deficiency in the Rat Impairs Recognition Memory, but Has No Effect on Social Approach or Hedonia

Developmental vitamin D (DVD) deficiency is a risk factor for schizophrenia. In rodents we show that DVD-deficiency alters brain development and produces behavioral phenotypes in the offspring of relevance to the positive symptoms of schizophrenia. The aims of this study are to examine behavioral phenotypes specific to the cognitive and negative symptoms of schizophrenia in this model, and to vary the duration of vitamin D deficiency during gestation and beyond birth. We hypothesize that a longer duration of DVD-deficiency would result in greater behavioral impairments. Female vitamin D-deficient Sprague Dawley dams were mated at 10 weeks of age. Dietary vitamin D was reintroduced to dams and/or pups at different developmental time-points: Conception, Birth, Post-natal day (PND) 6 and PND21. Adult male and female offspring were assessed on a battery of behavioral tests, including sucrose preference, open field, novel object recognition (NOR), social approach and social novelty. We find that all windows of DVD-deficiency impaired NOR a cognitive measure that requires intact recognition memory. Sucrose consumption, social approach and social memory negative symptom-like phenotypes were unaffected by any maternal dietary manipulation. In addition, contrary to our hypothesis, we find that rats in the Conception group, that is the shortest duration of vitamin D deficiency, demonstrate increased locomotor activity, and decreased interaction time with novel objects. These findings have implications for the increasing number of studies examining the preclinical consequences of maternal vitamin D deficiency, and continue to suggest that adequate levels of maternal vitamin D are required for normal brain development.

Glutathione deficiency induces epigenetic alterations of vitamin D metabolism genes in the livers of high-fat diet-fed obese mice

Obesity has been correlating with low levels of glutathione (GSH) and 25-hydroxyvitamin D3 (25(OH)VD3). The liver is the principal site for the 25(OH)VD3 biosynthesis. This study investigated whether GSH deficiency induces epigenetic alterations that impair Vitamin D (VD) metabolism genes in the livers of HFD-fed mice. The expression of the VD metabolism genes CYP2R1 and CYP27A1 (25-hydroxylase), CYP27B1 (1-α-hydroxylase), and vitamin D receptor (VDR) were downregulated in the livers of mice fed an HFD (GSH- deficient) compared with control diet-fed group. The expression of CYP24A1 (24-hydroxylase) was significantly increased, which catabolizes both 25(OH)VD3 and 1α,25-hydroxyvitaminD3. Gene-specific hypermethylation of 25-hydroxylase, 1-α-hydroxylase, and VDR, and hypomethylation of CYP24A1 was observed in HFD-fed mice. GSH deficiency induced in cultured hepatocytes caused an increase in oxidative stress and alterations in VD regulatory genes. Similarly, elevated global DNA methylation, Dnmt activity, and 5-methylcytosine but decreased Tet activity and 5-hydroxymethylcytosine were observed in the GSH-deficient hepatocytes and the liver of HFD-fed mice. Replenishment of GSH by its prodrugs treatment beneficially altered epigenetic enzymes, and VD-metabolism genes in hepatocytes. HFD-induces GSH deficiency and epigenetically alters VD-biosynthesis pathway genes. This provides a biochemical mechanism for the VD-deficiency and potential benefits of GSH treatment in reducing 25(OH)VD3-deficiency.