Vitamin D and Chronic Diseases

Drug Delivery Systems for Vitamin D Supplementation and Therapy

Vitamin D (VD) is a fat-soluble prohormone well known for its role in regulating calcium and phosphate metabolism. It has been clinically used for many years to prevent rickets in children, osteomalacia, and osteoporosis in adults. VD insufficiency is a common medical condition, and many supplements are available in the market in order to increase serum 25-hydroxy VD levels to recommended amounts. Over the course of the last decades, it has become increasingly clear that calcitriol, an active form of VD, regulates multiple cellular processes with effects on normal and malignant cell growth and differentiation, and on the immune and cardiovascular function. Increasing evidence supports the role of the VD system in cancer prevention and therapy. Due to many pleiotropic and beneficial effects in extra-skeletal disorders, VD has gained potential and become an interesting active for encapsulation into drug delivery systems. The purpose of this review is to present the diversity of drug delivery systems that have been reported for VD or VD derivatives in an orderly manner across the following categories: Oral administration, application on the skin, cancer prevention/therapy, and other diseases or routes of administration.

Role of Hypovitaminosis D in the Pathogenesis of Obesity-Induced Insulin Resistance

Obesity and type 2 diabetes have both rapidly increased during the last decades and are continuing to increase at an alarming rate worldwide. Obesity and impaired glucose homeostasis are closely related, and during the last decades of investigation about vitamin D, several clinical and epidemiological studies documented an inverse correlation between circulating vitamin D levels, central adiposity and the development of insulin resistance and diabetes. The insufficient sun exposure and outdoor activities of obese individuals, the storage of vitamin D in adipose tissue, because of its lipophilic properties, and the vitamin D-mediated modulation of adipogenesis, insulin secretion, insulin sensitivity and the immune system, are the main reasons for the close relationship between obesity, glucose homeostasis and hypovitaminosis D. Then objective of this review is to explore the pathophysiological mechanism(s) by which vitamin D modulates glycemic control and insulin sensitivity in obese individuals.

Effect of Calcium and Vitamin D Supplements as an Adjuvant Therapy to Metformin on Menstrual Cycle Abnormalities, Hormonal Profile, and IGF-1 System in Polycystic Ovary Syndrome Patients: A Randomized, Placebo-Controlled Clinical Trial

Objective

This study aims to investigate the effect of combining calcium and vitamin D supplements with metformin on menstrual cycle abnormalities, gonadotropins, and IGF-1 system in vitamin D-deficient/insufficient PCOS women.

Study Design

This is a randomized, placebo-controlled clinical trial.

Setting

This study was performed in Damascus University of Obstetrics and Gynecology Hospital and Orient Hospital, in Damascus, Syria.

Materials and Methods

Forty PCOS women with 25-OH-vitamin D < 30 ng/ml were randomly assigned to take either metformin (1500 mg/daily) plus placebo or metformin (1500 mg/daily) plus calcium (1000 mg/daily) and vitamin D₃ (6000 IU/daily) orally for 8 weeks. Serum levels of gonadotropins (luteinizing hormone (LH) and follicle-stimulating hormone (FSH)), insulin-like growth factor-1 (IGF-1), and insulin-like growth factor binding protein-1 (IGFBP-1) were detected at the baseline during the early follicular phase of a spontaneous or induced menstrual cycle and after 8 weeks of intervention (except for the final gonadotropins levels which were assayed from samples obtained during the early follicular phase of a spontaneous menstrual cycle).

Results

Thirty-four patients (85%) completed the study. After 8 weeks of intervention, calcium and vitamin D co-supplementation led to a significant increase in 25-OH-vitamin D levels and calcium levels in the supplementation group compared to the other group (change in 25-OH-vitamin D levels: +19.38 ± 7.78 vs +0.11 ± 4.79 ng/ml, respectively; p value=0.0001) (change in calcium levels: +0.83 ± 0.82 vs +0.01 ± 0.86 mg/dl, respectively; p value=0.014). An improvement in menstrual cycle irregularity was detected in 38.5% and 58.8% of patients in metformin-placebo group and metformin-calcium-vitamin D group, respectively; but the change was statistically significant only in the supplementation group (p value=0.002). Nevertheless, the means of changes from baseline in gonadotropins levels (serum levels of LH, FSH, and LH to FSH ratio) and the studied parameters of IGF-1 system (serum levels of IGF-1, IGFBP-1, and IGF-1 to IGFBP-I ratio) did not differ significantly between the two groups.

Conclusions

Calcium and vitamin D supplements can support metformin effect on regulation of menstrual cycle irregularity in vitamin D-deficient/insufficient PCOS patients, but this effect is not associated with any significant changes in gonadotropins or IGF-1 system. These results suggest a possible role of calcium and vitamin D supplements in managing PCOS. However, further studies are needed to identify the underlying mechanisms. The Clinical Trial Registration Number is NCT03792984.

Vitamin D in burn-injured patients

Recently, many studies have demonstrated pleotropic effects of vitamin D, including immune modulation and cardiovascular system activity. Sufficient vitamin D concentrations and supplementation of vitamin D may be of benefit in burn-injured patients. Low 25(OH)D has been observed in nearly all pediatric and most adult burn patients. Vitamin D has primarily been studied in pediatric burn patients, focusing on bone marker measurements and the incidence of fractures. The preferred vitamin D dose, formulation, and route of administration remain unknown, and there is limited data on the impact of vitamin D status on clinical outcomes. Further research should focus on determining optimal monitoring strategies, supplementation regimens and clinical outcomes like mortality, length of stay and incidence of sepsis.

Comparison of serum levels of vitamin D and vitamin D-binding protein in normal, osteopenic and osteoporotic postmenopausal women

Objective:

To compare the serum levels of vitamin D, vitamin D binding protein (VDBP) calcium and phosphate in normal, osteopenic and osteoporotic postmenopausal women categorized on the basis of bone mineral density (BMD) scores.

Methods:

A cross sectional study carried out from May 2017 to August 2018. BMD measured by Dual energy X-ray Absorptiometry categorized women (aged 20- 70 years) into normal (n=37) (T score ≥ -1.0) osteopenic (n=25) (-2.5< T score, < -1) and osteoporotic (n= 26) (T score < -2.5) according to WHO classification. Serum concentrations of vitamin D, VDBP, calcium, phosphate analyzed by enzyme linked immunosorbent assay were compared by Analysis of Variance

Results:

In normal females higher levels of vitamin D and VDBP were observed [15.82 (8 - 69.18), 469.9 (269.57 - 875.55)] vs. osteopenic [(7.45 (4.66 - 15.1), 296.05 (232.58 - 420.23)] and osteoporotic women [(7.25 (3.97 - 17.49), 272.94 (202.23 - 351.24)]; [median interquartile range]; p value < 0.0001.

Conclusion:

Vitamin D and VDBP are linked with bone health and estimation of VDBP appears to be a valuable tool for the assessment of increased bone loss and possible risks of bone fractures especially in postmenopausal women.

When and How to Diagnose and Treat Vitamin D Deficiency in Adults: A Practical and Clinical Update

Vitamin D deficiency is considered a major public health concern. Inadequate sun exposure, limited oral intake, and impaired intestinal absorption are common risk factors for vitamin D deficiency. An increasing amount of research is aimed at answering questions regarding the most convenient test that can assess vitamin D status, the indications for screening, and finally the utility of treatments for vitamin D deficiency. Our review outlines practical strategies to diagnose and treat vitamin D deficiency in adults. This study was undertaken in the PubMed and the Google Scholar databases in April 2018 without limitation as to the publication period. Vitamin D status is determined by measuring the 25-hydroxyvitamin D serum concentration. However, this technique has several limitations. Determining the accurate thresholds for vitamin D deficiency is still a matter of debate. Only individuals at risk for vitamin D deficiency should be screened. The symptoms of vitamin D deficiency are unspecific and very common. Therefore, physicians may easily suspect vitamin D deficiency, measure 25-hydroxyvitamin D levels, and sometimes overprescribe supplementation. Hypovitaminosis D could rarely be treated by increasing consumption of foods naturally containing and fortified with vitamin D. Special attention should be given to vitamin D supplementation to prevent adverse effects. No safe and well-defined threshold of ultraviolet exposure allows adequate vitamin D synthesis without increasing the risk of skin cancer. Unanimous and decisive guidelines are urgently needed to improve knowledge and practices related to vitamin D deficiency.

Analysis of Association between Vitamin D Deficiency and Insulin Resistance

Recent evidence revealed extra skeleton activity of vitamin D, including prevention from cardiometabolic diseases and cancer development as well as anti-inflammatory properties. It is worth noting that vitamin D deficiency is very common and may be associated with the pathogenesis of insulin-resistance-related diseases, including obesity and diabetes. This review aims to provide molecular mechanisms showing how vitamin D deficiency may be involved in the insulin resistance formation. The PUBMED database and published reference lists were searched to find studies published between 1980 and 2019. It was identified that molecular action of vitamin D is involved in maintaining the normal resting levels of ROS and Ca2+, not only in pancreatic β-cells, but also in insulin responsive tissues. Both genomic and non-genomic action of vitamin D is directed towards insulin signaling. Thereby, vitamin D reduces the extent of pathologies associated with insulin resistance such as oxidative stress and inflammation. More recently, it was also shown that vitamin D prevents epigenetic alterations associated with insulin resistance and diabetes. In conclusion, vitamin D deficiency is one of the factors accelerating insulin resistance formation. The results of basic and clinical research support beneficial action of vitamin D in the reduction of insulin resistance and related pathologies.

Vitamin D, diet, and lifestyle in a chronic SCI population

STUDY DESIGN

Cross-sectional study.

OBJECTIVES

Determine dietary, lifestyle, and clinical factors associated with plasma 25-hydroxyvitamin D [25(OH)D] levels in persons with chronic spinal cord injury (SCI).

SETTING

Veterans Affairs Medical Center in Boston, MA.

METHODS

174 participants completed food frequency and health questionnaires, provided a blood sample, and underwent dual x-ray absorptiometry (DXA) to assess %total body fat. Linear regression models were used to assess cross-sectional associations of personal, lifestyle, and nutritional factors with plasma 25(OH)D.

RESULTS

Independent factors positively associated with higher plasma 25(OH)D included vitamin D intake, age, hours of planned exercise, female sex, white race, wine consumption, and if a never or former smoker. The most important predictor of 25(OH)D was supplement intake. The majority of subjects (98.9% for vitamin D and 74.1% for calcium) did not meet the recommended daily allowance for adults from their diet alone. Level and completeness of SCI, injury duration, mobility, %total body fat, time outside, and comorbid diseases were not associated with plasma 25(OH)D.

CONCLUSIONS

Plasma 25(OH)D level in chronic SCI is not associated with clinical factors specific to SCI such as injury level and completeness, injury duration, and mobility mode, but related to supplement intake and other lifestyle factors.

Molecular Mechanism of Cancer Susceptibility Associated with Fok1 Single Nucleotide Polymorphism of VDR in Relation to Breast Cancer

Breast cancer is the leading cause of death among women worldwide. It is a multi-factorial disease caused by genetic and environmental factors. Vitamin D has been hypothesized to lower the risk of breast cancer via the nuclear vitamin D receptor (VDR). Genetic variants of these vitamin D metabolizing genes may alter the bioavailability of vitamin D, and hence modulate the risk of breast cancer.

Stabilization of Vitamin D in Pea Protein Isolate Nanoemulsions Increases Its Bioefficacy in Rats

Micronutrient delivery formulations based on nanoemulsions can enhance the absorption of nutrients and bioactives, and thus, are of great potential for food fortification and supplementation strategies. The aim was to evaluate the bioefficacy of vitamin D (VitD) encapsulated in nanoemulsions developed by sonication and pH-shifting of pea protein isolate (PPI) in restoring VitD status in VitD-deficient rats. Weaned male albino rats (n = 35) were fed either normal diet AIN-93G (VitD 1000 IU/kg) (control group; n = 7) or a VitD-deficient diet (<50 IU/kg) for six weeks (VitD-deficient group; n = 28). VitD-deficient rats were divided into four subgroups (n = 7/group). Nano-VitD and Oil-VitD groups received a dose of VitD (81 µg) dispersed in either PPI-nanoemulsions or in canola oil, respectively, every other day for one week. Their control groups, Nano-control and Oil-control, received the respective delivery vehicles without VitD. Serum 25-hydroxyvitamin D [25(OH)VitD], parathyroid hormone (PTH), Ca, P, and alkaline phosphatase (ALP) activity were measured. After one week of treatment, the VitD-deficient rats consuming Nano-VitD recovered from Vitamin D deficiency (VDD) as compared against baseline and had serum 25(OH)VitD higher than the Nano-control. Enhancement in VitD status was followed with expected changes in serum PTH, Ca, P, and ALP levels, as compared against the controls. Stabilization of VitD within PPI-based nanoemulsions enhances its absorption and restores its status and biomarkers of bone resorption in VitD-deficient rats.

Air pollution, environmental chemicals, and smoking may trigger vitamin D deficiency: Evidence and potential mechanisms

Beyond vitamin D (VD) effect on bone homeostasis, numerous physiological functions in human health have been described for this versatile prohormone. In 2016, 95% of the world's population lived in areas where annual mean ambient particulate matter (<2.5 μm) levels exceeded the World Health Organization guideline value (Shaddick et al., 2018). On the other hand, industries disperse thousands of chemicals continually into the environment. Further, considerable fraction of populations are exposed to tobacco smoke. All of these may disrupt biochemical pathways and cause detrimental consequences, such as VD deficiency (VDD). In spite of the remarkable number of studies conducted on the role of some of the above mentioned exposures on VDD, the literature suffers from two main shortcomings: (1) an overview of the impacts of environmental exposures on the levels of main VD metabolites, and (2) credible engaged mechanisms in VDD because of those exposures. To summarize explanations for these unclear topics, we conducted the present review, using relevant keywords in the PubMed database, to investigate the adverse effects of exposure to air pollution, some environmental chemicals, and smoking on the VD metabolism, and incorporate relevant potential pathways disrupting VD endocrine system (VDES) leading to VDD. Air pollution may lead to the reduction of VD cutaneous production either directly by blocking ultraviolet B photons or indirectly by decreasing outdoor activity. Heavy metals may reduce VD serum levels by increasing renal tubular dysfunction, as well as downregulating the transcription of cytochrome P450 mixed-function oxidases (CYPs). Endocrine-disrupting chemicals (EDCs) may inhibit the activity and expression of CYPs, and indirectly cause VDD through weight gain and dysregulation of thyroid hormone, parathyroid hormone, and calcium homeostasis. Smoking through several pathways decreases serum 25(OH)D and 1,25(OH)2D levels, VD intake from diet, and the cutaneous production of VD through skin aging. In summary, disturbance in the cutaneous production of cholecalciferol, decreased intestinal intake of VD, the modulation of genes involved in VD homeostasis, and decreased local production of calcitriol in target tissues are the most likely mechanisms that involve in decreasing the serum VD levels.

Association of Vitamin D Status with Body Mass Index in Adolescents in Ukraine

Background and aims: Vitamin D status in many health managements have been researched extensively, but its dependence with obesity still remains controversial. This article is devoted to examination of blood cholecalciferol levels in Ukrainian population with establishment the association of cholecalciferol levels and body mass index (BMI). Materials and methods: For this observed investigation, data were collected during the summer 2017, over a period of one week from three township areas in Carpathian region, Ukraine from 304 adults aged 19-78 years. Measured variables contained 25(OH)D level, weight and weight applied to check BMI degree. The average level of vitamin D among adolescents presented 23.1 ± 8.2 ng/ml. Female gender was associated with lower vitamin D concentrations (22.9 ± 9.3 ng/ml vs. 26.2 ± 8.5 ng/ml for men). Among the participants, 74.4% had a BMNI of 25 kg/m2 and over, and in 27.3% of them the number was 30 kg/m2 and over. Results: Violation of vitamin D status was detected in 90.5% persons. 1.8% people had been identified as severe 25(OH)D deficiency. Measurement of cholecalciferol demonstrated meaningful connection between its level and BMI only in persons with BMI 25-29.9 kg/m2. Average vitamin D concentrations in persons with BMI over30 kg/m2 did not vary to a significant range from data in persons with normal body weight. Conclusions: Vitamin D status among the adolescents in Ukraine is far from optimum. Our results confirm reliable association between cholecalciferol level and BMI in persons with overweight. Interchange between conservation of vitamin D and BMI needs additional surveys.

Impact of Nutritional and Environmental Factors on Vitamin D Deficiency

Background: Vitamin D can be obtained through a variety of food sources; however, ultraviolet rays in the sunlight can convert a natural substance in the skin known as ergosterol to vitamin D. Aim: This study aims to investigate the prevalence and risk factors linked to vitamin D deficiency among a group of apparently healthy young male and female Tabuk citizens in Saudi Arabia. Methods: A cross-sectional study that comprised a convenience sampling method of 350 male and female Tabuk citizens. Results: The results indicated a generalized vitamin D deficiency and severe deficiency among the participants, where 74.57% of the population had vitamin D deficiency, and 25.43% reported vitamin D sufficiency. There was a significant positive correlation among the BMI, exercise, exposure to sunlight, vitamin D intake, and calcium intake with vitamin D status (r = 0.574,** 0.525,** 0.515,** 0.466 and 0.465** at p-value < 0.001, respectively). Conclusion: The present study indicates vitamin D deficiency to be relatively common even among the population of Saudi Arabia, a country receiving adequate sunlight. Also, Vitamin D and calcium supplementation can prove to be beneficial in correcting the deficiency. Moreover, the individuals at a higher risk of vitamin insufficiency, such as women, need to be educated on the health benefits of vitamin D and calcium supplementation.

Modulation of neurosecretion and approaches for its multistep analysis

BACKGROUND

Neurosecretion is the multistep process occurring in separate spatial and temporal cellular boundaries which complicates its comprehensive analysis. Most of the research are focused on one distinct stage of synaptic vesicle recycling. Here, we describe approaches for complex analysis of synaptic vesicle (SV) endocytosis and separate steps of exocytosis at the level of presynaptic bouton and highly purified SVs.

METHODS

Proposed fluorescence-based strategies and analysis of neurotransmitter transport provided the advantages in studies of exocytosis steps. We evaluated SV docking/tethering, their Ca²⁺-dependent fusion and release of neurotransmitters gamma-aminobutyric acid (GABA) and glutamate in two animal models.

RESULTS

Approaches enabled us to study: 1) endocytosis/Ca²⁺-dependent release of fluorescent carbon nanodots (CNDs) during stimulation of nerve terminals; 2) the action of levetiracetam, modulator of SV glycoprotein SV2, on fusion competence of SVs and stimulated release of GABA and glutamate; 3) impairments of several steps of neurosecretion under vitamin D₃ deficiency.

CONCLUSIONS

Our algorithm enabled us to verify the method validity for multidimensional analysis of SV turnover. By increasing SV docking and the size of readily releasable pool (RRP), levetiracetam is able to selectively enhance the stimulated GABA secretion in hippocampal neurons. Findings suggest that SV2 regulates RRP through impact on the number of docked/primed SVs.

GENERAL SIGNIFICANCE

Methodology can be widely applied to study the stimulated neurosecretion in presynapse, regulation of SV docking, their Ca²⁺-dependent fusion with target membranes, quantitative analysis of expression of neuron-specific proteins, as well as for testing the efficiency of pre-selected designed neuroactive substances.

The association between the serum level of vitamin D and ischemic heart disease: a study from Jordan

Background

Decreased levels of vitamin D were associated with increased risk of multiple diseases, including cardiovascular diseases. However, there seem to be some discrepancies among the results obtained from different studies. The aim of the present study was to explore the importance of having sufficient serum levels of vitamin D in reducing the incidence and the progression of coronary artery stenosis and ischemic heart disease (IHD).

Methods

Serum levels of vitamin D were measured using radioimmunoassay in 186 Jordanian patients who underwent investigative coronary catheterization. Of these patients, 133 were suffering from coronary artery stenosis. The association between vitamin D levels, coronary stenosis and many risk factors was determined using SPSS software.

Results and conclusions

Interestingly, the current results did not show an association between vitamin D abnormalities and the incidence or the reoccurrence of coronary artery stenosis. Moreover, significant differences were detected in the prevalence of vitamin D abnormalities based on the patient’s gender, and there was a significant association between vitamin D abnormalities and both body mass index and dyslipidemia. However, current results did not show any significant association with other risk factors for IHD. For instance, no association was found with smoking, hypertension, diabetes mellitus, stable and unstable angina or with acute recent myocardial infarction.

A Case-Control Study of the Association between Vitamin D Levels and Gastric Incomplete Intestinal Metaplasia

Aim: Low circulating vitamin D levels are associated with gastric adenocarcinoma, but whether vitamin D levels are associated with premalignant gastric mucosal changes is unknown. Here, we determined associations between vitamin D levels and gastric incomplete intestinal metaplasia, a known gastric adenocarcinoma risk factor. Methods: This was a retrospective, unmatched, case-control study comparing serum 25-hydroxyvitamin D levels among subjects with gastric incomplete intestinal metaplasia (cases; n = 103) and those without gastric incomplete intestinal metaplasia (controls; n = 216). The 25-hydroxyvitamin D levels were categorized as normal (30–100 ng/dL), vitamin D insufficiency (VDi; 20–29 ng/dL), and vitamin D deficiency (VDd; <20 ng/dL). Using multivariable logistic regression, odds ratios (ORs) were calculated and adjusted to age, gender, ethnicity, body mass index, history of hypertension or diabetes mellitus, and timing of vitamin D collection to assess associations between 25-hydroxyvitamin D levels and gastric incomplete intestinal metaplasia. Results: A majority of case subjects were male, Hispanic, and did not have hypertension or diabetes mellitus. The average serum 25-hydroxyvitamin D level was significantly lower in the intestinal metaplasia group than the control group (19.7 ng/dL vs. 34.7 ng/dL; p < 0.001). Hypovitaminosis D was more common in subjects with incomplete intestinal metaplasia in a multivariable regression model (OR 54.1, 95% CI 21.8–134.3; p < 0.001). VDd (OR 129.0, 95% CI 43.7–381.2; p < 0.001) and VDi (OR 31.0, 95% CI 11.9–80.3; p < 0.001) were more common in patients with incomplete intestinal metaplasia than healthy subjects, with VDd slightly more prevalent than VDi (OR 4.0, 95% CI 1.7–9.6; p < 0.001). Conclusions: Vitamin D deficiency and insufficiency are more common in patients with gastric incomplete intestinal metaplasia than healthy subjects and may play a role in the development of premalignant phenotypes related to gastric adenocarcinoma.

Effect of vitamin D supplementation on fasting plasma glucose, insulin resistance and prevention of type 2 diabetes mellitus in non-diabetics: A systematic review and meta-analysis

Increasing epidemiological studies suggest that there is an association between vitamin D deficiency and risk of type 2 diabetes mellitus (T2DM). Therefore, randomized clinical trials (RCTs) have been performed to observe the effect of vitamin D supplementation on preventing T2DM, decreasing fasting plasma glucose (FPG) and improving insulin resistance to confirm the association between vitamin D and T2DM. However, the results of RCTs on controlling FPG level, improving insulin resistance and preventing T2DM in non-diabetics are inconsistent. In the present study, a systematic meta-analysis considering individual variation and intervention strategy was conducted to establish an objective and definitive conclusion. The results suggested that vitamin D supplementation had no significant effect on controlling FPG level, improving insulin resistance or preventing T2DM in non-diabetics in a pooled meta-analysis of 23 articles (containing 28 RCTs). However, stratified analysis indicated that supplementation of vitamin D had differential effects on FPG control, insulin sensitivity improvement and T2DM prevention in individuals with different baseline states: FPG was decreased for those with BMI <25 (P=0.048) or 20≤ 25(OH)D <30 ng/ml (P=0.002); insulin resistance was improved for those with 25(OH)D ≥30 ng/ml (P=0.021); and risk of T2DM was lower for pre-diabetic individuals (P=0.047) or for those with 25≤ BMI <30 (P=0.032). Additionally, the effect on T2DM prevention was improved when the supplement dose was >2,000 IU/day (P=0.047) and with intervention without calcium (P=0.047). Thus, further trials should focus on individual baselines and the supplementation strategy of vitamin D in the prevention of T2DM.

Reduced vitamin D receptor (VDR) expression and plasma vitamin D levels are associated with aging-related prostate lesions

BACKGROUND

Protective roles have been proposed for vitamin D in prostate cancer, which has the advanced age as the major risk factor. However, little is known about the expression of the vitamin D receptor (VDR) in the aging prostate and its association with the development of epithelial lesions that affect tissue homeostasis and may precede prostate tumors.

METHODS

VDR expression in the prostatic complex of young adults to senile Wistar rats, a natural model to study age-related prostatic disorders, was evaluated by immunohistochemical, Western blotting, and image-assisted analyzes. Results were correlated with the plasma levels of vitamin D and testosterone, the occurrence of punctual histopathological changes in the aging prostate, and the expression of retinoid X receptors (RXR).

RESULTS

VDR was widely distributed in the prostatic complex at all ages analyzed, with the highest immunoexpression found in basal epithelial cells. As the animals aged, VDR levels increased, except in punctual areas with intraepithelial proliferation, metaplasia, or proliferative inflammatory atrophy, which had reduced expression of this receptor concomitantly with increased cell proliferation. Interestingly, RXR expression in the aging prostate was similar to that found for its partner VDR, indicating that components of the VDR/RXR complex required for vitamin D signaling are affected in aging-related prostatic lesions. Moreover, plasma vitamin D levels declined at the same ages when prostatic alterations appeared. Although circulating levels of testosterone also decreased with aging, the changes observed in the components of the vitamin D system were not correlated with androgens.

CONCLUSIONS

Our data indicate that the aging prostate suffers from an imbalance on the intricate mechanism of tissue regulation by the vitamin D responsive system. We argue that the status of VDR expression might be determinant for the development of histopathological alterations in the aging prostate, which include premalignant lesions.

The Vitamin D⁻Folate Hypothesis as an Evolutionary Model for Skin Pigmentation: An Update and Integration of Current Ideas

Vitamin D is unique in being generated in our skin following ultraviolet radiation (UVR) exposure. Ongoing research into vitamin D must therefore always consider the influence of UVR on vitamin D processes. The close relationship between vitamin D and UVR forms the basis of the “vitamin D–folate hypothesis”, a popular theory for why human skin colour has evolved as an apparent adaption to UVR environments. Vitamin D and folate have disparate sensitivities to UVR; whilst vitamin D may be synthesised following UVR exposure, folate may be degraded. The vitamin D–folate hypothesis proposes that skin pigmentation has evolved as a balancing mechanism, maintaining levels of these vitamins. There are several alternative theories that counter the vitamin D–folate hypothesis. However, there is significant overlap between these theories and the now known actions of vitamin D and folate in the skin. The focus of this review is to present an update on the vitamin D–folate hypothesis by integrating these current theories and discussing new evidence that supports associations between vitamin D and folate genetics, UVR, and skin pigmentation. In light of recent human migrations and seasonality in disease, the need for ongoing research into potential UVR-responsive processes within the body is also discussed.

Exploring vitamin D metabolism and function in cancer

Vitamin D, traditionally known as an essential nutrient, is a precursor of a potent steroid hormone that regulates a broad spectrum of physiological processes. In addition to its classical roles in bone metabolism, epidemiological, preclinical, and cellular research during the last decades, it revealed that vitamin D may play a key role in the prevention and treatment of many extra-skeletal diseases such as cancer. Vitamin D, as a prohormone, undergoes two-step metabolism in liver and kidney to produce a biologically active metabolite, calcitriol, which binds to the vitamin D receptor (VDR) for the regulation of expression of diverse genes. In addition, recent studies have revealed that vitamin D can also be metabolized and activated through a CYP11A1-driven non-canonical metabolic pathway. Numerous anticancer properties of vitamin D have been proposed, with diverse effects on cancer development and progression. However, accumulating data suggest that the metabolism and functions of vitamin D are dysregulated in many types of cancer, conferring resistance to the antitumorigenic effects of vitamin D and thereby contributing to the development and progression of cancer. Thus, understanding dysregulated vitamin D metabolism and function in cancer will be critical for the development of promising new strategies for successful vitamin D-based cancer therapy.

Transmission disequilibrium of rs4809957 in type 2 diabetes mellitus families and its association with vitamin D deficiency: A family-based case-control study

AIMS

Association between T2DM and vitamin D was found in many epidemiologic reports. And 24-hydroxylase encoded by CYP24A1 is the very enzyme that degrades the active vitamin D metabolite. We aimed to investigate the association between rs4809957 in CYP24A1 and T2DM, as well as vitamin D level.

METHODS

A total of 419 pedigrees containing 1556 participants were included. T2DM diagnosis, 25(OH)D measurement and genotyping of rs4809957 were conducted for all the individual. Then association between rs4809957 and T2DM, as well as 25(OH)D level, was investigated by family-based association test (FBAT) and 1:1 matched case-control study.

RESULTS

The FBAT results revealed that there was transmission disequilibrium for allele G in T2DM families by both additive model (Z = 2.183, P = 0.029049) and recessive model (Z = 2.236, P = 0.025347). Allele G was also associated with 25(OH)D level in both additive model (Z = 2.549, P = 0.010811) and dominant model (Z = 2.012, P = 0.044187). On the other hand, results of case-control study suggested that vitamin D deficiency was a risk factor for T2DM (OR 1.987; 95%CI 1.331-2.964; P = 0.001). Further stratified analysis revealed that vitamin D deficiency increased T2DM risk in women (OR 2.347; 95%CI 1.373-4.012; P = 0.002), instead of men (OR 1.600; 95%CI 0.874-2.931; P = 0.127). In addition, T2DM patients with GG and AG genotypes were more susceptible to vitamin D deficiency than the control (P = 0.006 and P = 0.038, respectively).

CONCLUSION

There was transmission disequilibrium for allele G of rs4809957 in T2DM families, which was linked to vitamin D deficiency.

Vitamin D prevents lipid accumulation in murine muscle through regulation of PPARγ and perilipin-2 expression

Vitamin D plays an important role in regulation of skeletal muscle tone and contraction. Serum vitamin D status is linked to muscle power and force in adolescent girls, and vitamin D deficiency is associated with myopathies in children and poorer physical performance in the elderly. We previously reported that vitamin D deficiency is linked to a significant increase in muscle fatty infiltration in healthy young women, and studies in patients with neuromuscular disorders also associate muscle weakening and lipid content. In order to better understand the link between vitamin D status and skeletal muscle lipid metabolism, we compared the effect of a low (25IU/kg) or normal (1000IU/kg) vitamin D₃ diet on muscle fat in female FVB mice maintained in a room without UVB lighting to minimize endogenous vitamin D production. Animals on low vitamin D diet displayed lower circulating 25(OH)D levels and a dramatic increase (287±52% compared to normal diet, p<0.0001) in lipid deposition in skeletal muscle accompanied by muscle fiber disorganization. Lipid droplet staining increased by 242±23% (p<0.0001) in low vitamin D diet, and lipid droplet coat protein perilipin-2 and nuclear receptor transcription factor PPARγ expression levels were increased compared to mice fed the normal vitamin D diet: average staining for PLIN2: 0.22±0.08 (25IU/kg diet) vs 0.10±0.02 (1000IU/kg). Average staining for PPARγ: 0.24±0.06 (25IU/kg diet) vs 0.07±0.04 (1000IU/kg) p<0.0001. Tissue mass spectrometry imaging revealed major differences in muscle phospholipids profile depending on diet. In vitro, 1,25(OH)₂D₃ treatment of 3T3-L1 pre-adipocytes inhibited appearance of lipid droplets by 79±9.3%, and caused a 80±10% and 25±8% (p=0.001) reduction in PPARγ and perilipin-2 mRNA levels (by qPCR) compared to control cells. In summary, we report here the first in vivo model illustrating the important structural muscle fiber disorganization and fat accumulation inside and outside muscle fibers that accompany vitamin D deficiency. Furthermore, we show that the underlying mechanisms involve PPARγ and perilipin-2.

Vitamin D deficiency causes inward hypertrophic remodeling and alters vascular reactivity of rat cerebral arterioles

Background and purpose

Vitamin D deficiency (VDD) is a global health problem, which can lead to several pathophysiological consequences including cardiovascular diseases. Its impact on the cerebrovascular system is not well understood. The goal of the present work was to examine the effects of VDD on the morphological, biomechanical and functional properties of cerebral arterioles.

Methods

Four-week-old male Wistar rats (n = 11 per group) were either fed with vitamin D deficient diet or received conventional rat chow with per os vitamin D supplementation. Cardiovascular parameters and hormone levels (testosterone, androstenedione, progesterone and 25-hydroxyvitamin D) were measured during the study. After 8 weeks of treatment anterior cerebral artery segments were prepared and their morphological, biomechanical and functional properties were examined using pressure microangiometry. Resorcin-fuchsin and smooth muscle actin staining were used to detect elastic fiber density and smooth muscle cell counts in the vessel wall, respectively. Sections were immunostained for eNOS and COX-2 as well.

Results

VDD markedly increased the wall thickness, the wall-to-lumen ratio and the wall cross-sectional area of arterioles as well as the number of smooth muscle cells in the tunica media. As a consequence, tangential wall stress was significantly lower in the VDD group. In addition, VDD increased the myogenic as well as the uridine 5’-triphosphate-induced tone and impaired bradykinin-induced relaxation. Decreased eNOS and increased COX-2 expression were also observed in the endothelium of VDD animals.

Conclusions

VDD causes inward hypertrophic remodeling due to vascular smooth muscle cell proliferation and enhances the vessel tone probably because of increased vasoconstrictor prostanoid levels in young adult rats. In addition, the decreased eNOS expression results in endothelial dysfunction. These morphological and functional alterations can potentially compromise the cerebral circulation and lead to cerebrovascular disorders in VDD.

Maternal transmission disequilibrium of rs2248359 in type 2 diabetes mellitus families and its association with vitamin D level in offspring

Association between T2DM and vitamin D deficiency has been reported in many epidemiologic studies. 24-hydroxylase encoded by CYP24A1 is the enzyme that degrades the active vitamin D metabolite. Variation in CYP24A1 may be associated with T2DM. This study investigates the association between rs2248359 in CYP24A1 and T2DM by a family-based association test (FBAT) and in a case-control study. The FBAT results revealed that there was transmission disequilibrium for allele T in both additive model (Z = 2.041, P = 0.041227) and dominant model (Z = 2.722, P = 0.006496). Results of the case-control study suggested that rs2248359 may be a risk factor for female T2DM (P = 0.036) but not for male T2DM (P = 0.816). Furthermore, excessive transmission of allele T in T2DM offspring was observed compared with the non-T2DM offspring (OR 1.392; 95%CI 1.024–1.894; P = 0.035). In addition, combination of maternal CT and paternal CC genotypes had significant synergistic effect on obtaining CT genotype for offspring with T2DM (OR 6.245; 95%CI 1.868–20.883; P = 0.004). Besides, lower level of 25(OH)D in T2DM offspring with genotype CT was observed as compared with the non-T2DM offspring (P = 0.013). These data suggest that maternal transmission disequilibrium of allele T may be a risk factor for T2DM and vitamin D deficiency in T2DM offspring.

Subcutaneous white adipocytes express a light sensitive signaling pathway mediated via a melanopsin/TRPC channel axis

Subcutaneous white adipose tissue (scWAT) is the major fat depot in humans and is a central player in regulating whole body metabolism. Skin exposure to UV wavelengths from sunlight is required for Vitamin D synthesis and pigmentation, although it is plausible that longer visible wavelengths that penetrate the skin may regulate scWAT function. In this regard, we discovered a novel blue light-sensitive current in human scWAT that is mediated by melanopsin coupled to transient receptor potential canonical cation channels. This pathway is activated at physiological intensities of light that penetrate the skin on a sunny day. Daily exposure of differentiated adipocytes to blue light resulted in decreased lipid droplet size, increased basal lipolytic rate and alterations in adiponectin and leptin secretion. Our results suggest that scWAT function may be directly under the influence of ambient sunlight exposure and may have important implications for our current understanding of adipocyte biology. (150 words)

Vitamin D deficiency accelerates ageing and age-related diseases: a novel hypothesis

Ageing can occur at different rates, but what controls this variable rate is unknown. Here I have developed a hypothesis that vitamin D may act to control the rate of ageing. The basis of this hypothesis emerged from studyng the various cellular processes that control ageing. These processes such as autophagy, mitochondrial dysfunction, inflammation, oxidative stress, epigenetic changes, DNA disorders and alterations in Ca²⁺ and reactive oxygen species (ROS) signalling are all known to be regulated by vitamin D. The activity of these processes will be enhanced in individuals that are deficient in vitamin D. Not only will this increase the rate of ageing, but it will also increase the probability of developing age-related diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis and cardiovascular disease. In individual with normal vitamin D levels, these ageing-related processes will occur at lower rates resulting in a reduced rate of ageing and enhanced protection against these age-related diseases.

Vitamin D deficiency: infertility and neurodevelopmental diseases (attention deficit hyperactivity disorder, autism, and schizophrenia)

The process of development depends on a number of signaling systems that regulates the progressive sequence of developmental events. Infertility and neurodevelopmental diseases, such as attention deficit hyperactivity disorder, autism spectrum disorders, and schizophrenia, are caused by specific alterations in these signaling processes. Calcium signaling plays a prominent role throughout development beginning at fertilization and continuing through early development, implantation, and organ differentiation such as heart and brain development. Vitamin D plays a major role in regulating these signaling processes that control development. There is an increase in infertility and an onset of neurodevelopmental diseases when vitamin D is deficient. The way in which vitamin D deficiency acts to alter development is a major feature of this review. One of the primary functions of vitamin D is to maintain the phenotypic stability of both the Ca²⁺ and redox signaling pathways that play such a key role throughout development.