Vitamin D: metabolism

Oleanolic acid exerts bone anabolic effects via activation of osteoblastic 25-hydroxyvitamin D 1-alpha hydroxylase

Oleanolic acid (OA) is previously shown to exert bone protective effects in aged animals. However, its role in regulating osteoblastic vitamin D bioactivation, which is one of major causes of age-related bone loss, remains unclear. Our results revealed that treatment of OA significantly increased skeletal CYP27B1 expression and circulating 1,25(OH)2D3 in ovariectomized mice (p <0.01). Moreover, OA upregulated CYP27B1 protein expression and activity, as well as the vitamin D-responsive bone markers alkaline phosphatase (ALP) activity and osteopontin (OPN) protein expression, in human osteoblast-like MG-63 cells (p<0.05). CYP27B1 expression increased along with the osteoblastic differentiation of human bone marrow derived mesenchymal stem cells (hMSCs). CYP27B1 expression and cellular 1,25(OH)2D3 production were further potentiated by OA in cells at mature osteogenic stages. Notably, our study suggested that the osteogenic actions of OA were CYP27B1 dependent. In summary, the bone protective effects of OA were associated with the induction of CYP27B1 activity and expression in bone tissues and osteoblastic lineages. Hence, OA might be a potential approach for management of age-related bone loss.

The effect of oral supplementation of Paricalcitol on C-reactive protein levels in chronic kidney disease patients: GRADE-assessed systematic review and dose-response meta-analysis of data from randomized controlled trials

BACKGROUND

Previous studies investigating the effect of oral supplementation of paricalcitol on reactive protein levels in chronic kidney disease (CKD) patients reported inconsistent findings. In this systematic review and meta-analysis, we have analyzed and interpreted the results obtained from previous randomized clinical trials on the effect of paricalcitol on C-reactive protein in CKD patients in the literature.

METHODS

MEDLINE, SciVerse Scopus, and Clarivate Analytics Web of Science databases were searched until January 2023 and related articles were obtained through a careful screening process allowing extraction of required data from selected articles. The effect size was calculated using a random effect model and weighted mean differences (WMD) and 95% confidence intervals (CI). Heterogeneity among studies was evaluated using Cochran's Q test and I2.

RESULTS

Amongst the 182 articles obtained from the initial search, 4 studies (6 arms) were finally included in the meta-analysis. Pooled analysis shows that C-reactive protein levels significantly decrease after oral supplementation with paricalcitol (WMD: -2.55 mg/L, 95% CI (-4.99 to -0.11; P = 0.04). The studies used in this meta-analysis showed significant heterogeneity (I2 = 66.3% and P = 0.01).

CONCLUSION

Oral paricalcitol supplementation in CKD patients can significantly reduce C-reactive protein levels, which may prevent CKD progression.

Relationship of the bone phenotype of the Klotho mutant mouse model of accelerated aging to changes in skeletal architecture that occur with chronological aging

Introduction

Due to the relatively long life span of rodent models, in order to expediate the identification of novel therapeutics of age related diseases, mouse models of accelerated aging have been developed. In this study we examined skeletal changes in the male and female Klotho mutant (kl/kl) mice and in male and female chronically aged mice to determine whether the accelerated aging bone phenotype of the kl/kl mouse reflects changes in skeletal architecture that occur with chronological aging.

Methods

2, 6 and 20-23 month old C57BL/6 mice were obtained from the National Institute of Aging aged rodent colony and wildtype and kl/kl mice were generated as previously described by M. Kuro-o. Microcomputed tomography analysis was performed ex vivo to examine trabecular and cortical parameters from the proximal metaphyseal and mid-diaphyseal areas, respectively. Serum calcium and phosphate were analyzed using a colorimetric assay. The expression of duodenal Trpv6, which codes for TRPV6, a vitamin D regulated epithelial calcium channel whose expression reflects intestinal calcium absorptive efficiency, was analyzed by quantitative real-time PCR.

Results and discussion

Trabecular bone volume (BV/TV) and trabecular number decreased continuously with age in males and females. In contrast to aging mice, an increase in trabecular bone volume and trabecular number was observed in both male and female kl/kl mice. Cortical thickness decreased with advancing age and also decreased in male and female kl/kl mice. Serum calcium and phosphate levels were significantly increased in kl/kl mice but did not change with age. Aging resulted in a decline in Trpv6 expression. In the kl/kl mice duodenal Trpv6 was significantly increased. Our findings reflect differences in bone architecture as well as differences in calcium and phosphate homeostasis and expression of Trpv6 between the kl/kl mutant mouse model of accelerated aging and chronological aging. Although the Klotho deficient mouse has provided a new understanding of the regulation of mineral homeostasis and bone metabolism, our findings suggest that changes in bone architecture in the kl/kl mouse reflect in part systemic disturbances that differ from pathophysiological changes that occur with age including dysregulation of calcium homeostasis that contributes to age related bone loss.

Mixture of air pollution, brominated flame retardants, polychlorinated biphenyls, per- and polyfluoroalkyl substances, and organochlorine pesticides in relation to vitamin D concentrations in pregnancy

Over two-thirds of pregnant women in the U.S. have insufficient 25(OH)D (Vitamin D) concentrations, which can adversely impact fetal health. Several pollutants have been associated with 25(OH)D, but have not been considered in the context of chemical co-exposures. We aimed to determine associations between a broad mixture of prenatal environmental chemical exposures and 25(OH)D concentrations in mid-pregnancy. Stored mid-pregnancy serum samples were assayed from 421 women delivering live births in Southern California in 2000-2003. 25(OH)D, six BFRs, eleven polychlorinated biphenyls (PCBs), six per- and polyfluoroalkyl substances, and two organochlorine pesticides were detected in ≥60% of specimens. Gestational exposures to airborne particulate matter ≤ 10 μm (PM10) and ≤ 2.5 μm (PM2.5), nitrogen monoxide (NO), nitrogen dioxide (NO2), and ozone concentrations were derived from monitoring station data. Bayesian Hierarchical Modeling (BHM) and Bayesian Kernel Machine Regression (BKMR) analyses estimated overall mixture and individual chemical associations accounting for co-exposures and covariates with mean 25(OH)D levels, and BHM was used to estimate associations with insufficient (<75 nMol/L) 25(OH)D levels. Non-mixture associations for each chemical were estimated with linear and logistic models. PM10 [BHM estimate: -0.133 nmol/l 95% Credible Interval (-0.240, -0.026)] was associated with lower 25(OH)D in BHM and BKMR. Higher quantiles of combined exposures were associated with lower 25(OH)D, though with wide credible intervals. In non-mixture models, PM10, PM2.5, NO, and NO2 were associated with lower concentrations, while O3 and PBDE153 were associated with higher 25(OH)D and/or lower insufficiency. While some chemicals were associated with increased and others with decreased 25(OH)D concentrations, the overall mixture was associated with lower concentrations. Mixture analyses differed from non-mixture regressions, highlighting the importance of mixtures approaches for estimating real-world associations.

The Role of Vitamin D in Reducing the Risk of Metabolic Disturbances That Cause Cardiovascular Diseases

Among the most common problems facing public health today is a lack of vitamin D, which plays a role in the physiological processes of chronic illness conditions. Vitamin D deficiency in metabolic disorders has primary effects on osteoporosis, obesity, hypertension, diabetes, and cardiovascular disease (CVD). Vitamin D acts as a "co-hormone" in the various tissues of the body, and it has been found that vitamin D receptors (VDR) are present on all cell types, suggesting that vitamin D has a wide range of effects on most cells. Recently, there has been a surge in interest in assessing its roles. Vitamin D insufficiency increases the risk of diabetes because it lowers insulin sensitivity, and also raises the risk of obesity and CVD because of its effect on the body's lipid profile, particularly in terms of the prevalence of dangerously high levels of low-density lipoproteins (LDL). Furthermore, vitamin D insufficiency is often related to CVD and connected risk factors, highlighting the need to know vitamin D's functions in relation to metabolic syndrome and related processes. Through looking at previous studies, this paper explains why vitamin D is important, how deficiency is related to risk factors for metabolic syndrome through different mechanisms, and how deficiency affects CVD.

Determination of vitamin D3 conjugated metabolites: a complementary view on hydroxylated metabolites

Experts typically define vitamin D deficiency levels by the determination of a circulating 25-hydroxyvitamin D₃-calcifediol prohormone. A large part of the population is characterized by deficient vitamin D levels (calcifediol < 20 ng mL^-1) despite individuals not being affected by any disorder. Cholecalciferol (vitamin D₃) and/or calcifediol supplementation is a common practice for vitamin D-deficient individuals as recommended by international scientific societies and official agencies. In the last few years, several studies have reported the presence of conjugated vitamin D₃ metabolites, mainly glucuronidation and sulfation derivatives, although simultaneous quantitative measurements involving phase I and II vitamin D metabolites have not been carried out. A quantitative method based on tandem mass spectrometry detection is proposed here for the combined determination of phase I and phase II vitamin D₃ metabolites in human serum. As phase I and phase II metabolites are preferentially ionized in different modes, a switching polarity mode was adopted to determine both groups of compounds in serum at high sensitivity levels (pg mL^-1). The validation of this proposal was successfully accomplished by following the Center for Drug Evaluation and Research (CDER) guidelines. Its applicability was tested in a cohort of volunteers with mostly deficient baseline levels. Considering the sulfated form of calcifediol, the sum of its concentrations showed sufficient baseline vitamin D levels in all individuals, suggesting that this could be a novel strategy for vitamin D deficiency definition. Therefore, phase II metabolites are proposed to be included when evaluating the vitamin D status since they provide more information about the overall status of the vitamin D endocrine system. Nevertheless, further studies are required to confirm the biological activity of these conjugated metabolites and the suitability of this strategy for the description of vitamin D deficiency.

Calcitriol increases MBNL1 expression and alleviates myotonic dystrophy phenotypes in HSALR mouse models

BACKGROUND

Myotonic dystrophy type 1 (DM1), one of the most common forms of adult-onset muscular dystrophy, is caused by abnormally expanded CTG repeats in the 3' untranslated region of the DMPK gene. The CUG repeats transcribed from the expanded CTG repeats sequestrate a splicing factor, MBNL1, causing the clinical symptoms in DM1. Nowadays, only symptomatic treatments are available for DM1, and no rational therapy is available. Recently, upregulation of MBNL1 expression has been found to be one of the promising therapies for DM1.

METHODS

All experiments were conducted in the C2C12 myoblasts and HSA^LR mice, a DM1 mouse model. Real-time PCR and western blot were used to detect the mRNA and protein level, respectively. The rotarod exercise, grip strength and hanging time were used to evaluate the muscle strength of mice.

RESULTS

In this study, we demonstrated that calcitriol, an active form of vitamin D3, increased MBNL1 in C2C12 mouse myoblasts as well as in HSA^LR mice model for DM1. In HSA^LR mice model, calcitriol improved muscle strength, and corrected aberrant splicing in skeletal muscle. Besides, calcitriol reduced the number of central nuclei, and improved muscle histopathology in HSA^LR mice. In addition, we identified that calcitriol upregulated MBNL1 expression via activating the promoter of Mbnl1 in C2C12 myogenic cells.

CONCLUSION

Our study suggests that calcitriol is a potential pharmacological strategy for DM1 that enhances MBNL1 expression.

Vitamin D3 eradicates Helicobacter pylori by inducing VDR-CAMP signaling

Background

Vitamin D₃ [VitD₃, 1,25 (OH)₂D₃] is known to have immunomodulatory and anti-microbial properties; however, its activity against Helicobacter pylori is unclear. In this study, we established H. pylori infection models in wild-type and VitD₃ receptor (VDR) knockdown mice and analyzed the effects of VitD₃ and their underlying mechanisms.

Methods

VDR^+/+ and VDR^+/- mice were intragastrically infected with the H. pylori SS1 strain. After confirmation of H. pylori infection, mice were treated with different doses of VitD₃. The infection levels in stomach tissues were quantified using the colony-forming assay, and the expression levels of the VDR and cathelicidin antimicrobial peptide (CAMP) in the gastric mucosa were analyzed by immunohistochemistry and western blotting.

Results

The gastric mucosa of VDR^+/- mice was more susceptible to H. pylori colonization and had lower levels of VDR and CAMP expression than that of VDR^+/+ mice. H. pylori infection upregulated VDR and CAMP expression in the stomach of both wild-type and mutant mice, and VitD₃ treatment resulted in further increase of VDR and CAMP levels, while significantly and dose-dependently decreasing the H. pylori colonization rate in both mouse groups, without affecting blood calcium or phosphorus levels.

Conclusion

Our data indicate that oral administration of VitD₃ reduces the H. pylori colonization rate and upregulates VDR and CAMP expression in the gastric mucosa, suggesting a role for VitD₃/VDR/CAMP signaling in the eradication of H. pylori in the stomach. These findings provide important insights into the mechanism underlying the anti-H. pylori activity of VitD₃ and should be useful in the development of measures to eradicate H. pylori.

Vitamin D deficiency attenuates endothelial function by reducing antioxidant activity and vascular eNOS expression in the rat microcirculation

This study examined the effects of vitamin D deficiency on vascular function and tissue oxidative status in the microcirculation; and whether or not these effects can be ameliorated with calcitriol, the active vitamin D metabolite. Three groups (n = 10 each) of male Sprague Dawley rats were fed for 10 weeks with control diet (CR), vitamin D-deficient diet without (DR), or with oral calcitriol supplementation (0.15 μg/kg) for the last four weeks (DSR). After 10 weeks, rats were sacrificed; mesenteric arterial rings were studied using wire myograph. Oxidative stress biomarkers malondialdehyde (MDA) levels and superoxide dismutase (SOD) activity were measured in the mesenteric arterial tissue. Vascular protein expression of endothelial nitric oxide synthase (eNOS) was determined by Western blotting. Acetylcholine-induced endothelium-dependent relaxation of DR was lower than CR. eNOS expression and SOD activity were lower in mesenteric arterial tissue of DR compared to CR. Calcitriol supplementation to DSR did not ameliorate the above parameters; in fact, augmented endothelium-dependent contraction was observed. Serum calcium was higher in DSR compared to CR and DR. In conclusion, vitamin D deficiency impaired microvascular vasodilation, associated with eNOS downregulation and reduced antioxidant activity. Calcitriol supplementation to vitamin D-deficient rats at the dosage used augmented endothelium-dependent contraction, possibly due to hypercalcaemia.

Vitamin D Sources, Metabolism, and Deficiency: Available Compounds and Guidelines for Its Treatment

Studies on vitamin/hormone D deficiency have received a vast amount of attention in recent years, particularly concerning recommendations, guidelines, and treatments. Moreover, vitamin D’s role as a hormone has been confirmed in various enzymatic, metabolic, physiological, and pathophysiological processes related to many organs and systems in the human body. This growing interest is mostly due to the evidence that modest-to-severe vitamin D deficiency is widely prevalent around the world. There is broad agreement that optimal vitamin D status is necessary for bones, muscles, and one’s general health, as well as for the efficacy of antiresorptive and anabolic bone-forming treatments. Food supplementation with vitamin D, or the use of vitamin D supplements, are current strategies to improve vitamin D levels and treat deficiency. This article reviews consolidated and emerging concepts about vitamin D/hormone D metabolism, food sources, deficiency, as well as the different vitamin D supplements available, and current recommendations on the proper use of these compounds.

Vitamin D and Stress Fractures in Sport: Preventive and Therapeutic Measures-A Narrative Review

There are numerous risk factors for stress fractures that have been identified in literature. Among different risk factors, a prolonged lack of vitamin D (25(OH)D) can lead to stress fractures in athletes since 25(OH)D insufficiency is associated with an increased incidence of a fracture. A 25(OH)D value of <75.8 nmol/L is a risk factor for a stress fracture. 25(OH)D deficiency is, however, only one of several potential risk factors. Well-documented risk factors for a stress fracture include female sex, white ethnicity, older age, taller stature, lower aerobic fitness, prior physical inactivity, greater amounts of current physical training, thinner bones, 25(OH)D deficiency, iron deficiency, menstrual disturbances, and inadequate intake of 25(OH)D and/or calcium. Stress fractures are not uncommon in athletes and affect around 20% of all competitors. Most athletes with a stress fracture are under 25 years of age. Stress fractures can affect every sporty person, from weekend athletes to top athletes. Stress fractures are common in certain sports disciplines such as basketball, baseball, athletics, rowing, soccer, aerobics, and classical ballet. The lower extremity is increasingly affected for stress fractures with the locations of the tibia, metatarsalia and pelvis. Regarding prevention and therapy, 25(OH)D seems to play an important role. Athletes should have an evaluation of 25(OH)D -dependent calcium homeostasis based on laboratory tests of 25-OH-D3, calcium, creatinine, and parathyroid hormone. In case of a deficiency of 25(OH)D, normal blood levels of ≥30 ng/mL may be restored by optimizing the athlete's lifestyle and, if appropriate, an oral substitution of 25(OH)D. Very recent studies suggested that the prevalence of stress fractures decreased when athletes are supplemented daily with 800 IU 25(OH)D and 2000 mg calcium. Recommendations of daily 25(OH)D intake may go up to 2000 IU of 25(OH)D per day.

Evaluation of the potential anticancer activity of different vitamin D metabolites on colorectal and breast cancer cell lines

OBJECTIVES

Vitamin D is very important for calcium and mineral metabolism, and many hypotheses appear to link sunlight exposure with cancer risk and prognosis. As many studies supported the antitumor effect of vitamin D we wanted to investigate the potential effect of multiple vitamin D metabolites.

METHODS

This study compared the anticancer effect of three inactive forms of vitamin D₃ which are; cholecalciferol, alfacalcidol, and calcifediol on two human cancer cell lines colorectal cancer (CaCo II) and breast cancer (MCF-7). All were examined after 24, 48, and 72 h continuous exposure using a colorimetric assay (MTT) seeded in 96-multiwell plates. Doxorubicin anticancer used as a standard agent for comparison, while normal skin fibroblast cells (HDFa) was used as our negative control. IC₅₀ values were calculated as indication of antitumor effect.

RESULTS

Broad-spectrum of cytotoxicity with IC₅₀ values ranging from 4 to 200 μM were found. Alfacalcidol was the most potent cytotoxic agents on colorectal cancer (CaCo II) and breast cancer (MCF-7) compared to cholecalciferol, and calcifediol. Both, alfacalcidol and calcifediol were more cytotoxic than cholecalciferol on the tested cell lines as they are partially active metabolites. Breast cancer (MCF-7) was the most sensitive to all metabolites at all-time intervals with the best IC₅₀ values of 4.35 μM ± 1.06 after 72 h continuous exposure of alfacalcidol.

CONCLUSIONS

Vitamin D metabolites are a potential option for cancer treatment along with or an alternative to chemo-therapeutics although extensive preclinical studies are required to prove this effect.

Supplementation with vitamin D in the COVID-19 pandemic?

The coronavirus disease 2019 (COVID-19) pandemic was declared a public health emergency of international concern by the World Health Organization. COVID-19 has high transmissibility and could result in acute lung injury in a fraction of patients. By counterbalancing the activity of the renin-angiotensin system, angiotensin-converting enzyme 2, which is the fusion receptor of the virus, plays a protective role against the development of complications of this viral infection. Vitamin D can induce the expression of angiotensin-converting enzyme 2 and regulate the immune system through different mechanisms. Epidemiologic studies of the relationship between vitamin D and various respiratory infections were reviewed and, here, the postulated mechanisms and clinical data supporting the protective role of vitamin D against COVID-19-mediated complications are discussed.

The Role of Vitamin D in Small Animal Bone Metabolism

Dogs and cats have differences in vitamin D metabolism compared to other mammalian species, as they are unable to perform vitamin D cutaneous synthesis through sun exposure. Therefore, they are dependent on the dietary intake of this nutrient. The classic functions of vitamin D are to stimulate intestinal calcium and phosphate absorption, renal calcium and phosphate reabsorption and regulate bone mineral metabolism. Thus, it is an important nutrient for calcium and phosphorus homeostasis. This review highlights the evidence of the direct and indirect actions of vitamin D on bone mineral metabolism, the consequences of nutritional imbalances of this nutrient in small animals, as well as differences in vitamin D metabolism between different size dogs.

25-Hydroxyvitamin D status, vitamin D intake, and skin cancer risk: a systematic review and dose-response meta-analysis of prospective studies

Sun exposure is a major environmental risk factor for skin cancers and is also an important source of vitamin D. However, while experimental evidence suggests that vitamin D may have a protective effect on skin cancer risk, epidemiologic studies investigating the influence of 25-hydroxyvitamin D (25(OH)D) level and/or vitamin D intake on skin cancer risk are conflicting. A systematic review and dose–response meta-analyses of prospective studies was conducted to clarify these associations. Relevant studies were identified by searching the PubMed database up to 30th August 2019. Random effects dose–response meta-analyses were used to estimate summary relative risks (SRRs) and 95% confidence intervals (CIs). Overall, thirteen prospective studies were included. Circulating level of 25(OH)D was associated with higher risks of melanoma (SRR (95% CI) per 30 nmol = 1.42 (1.17–1.72)) and keratinocyte cancer (KC) (SRR (95% CI) per 30 nmol/L = 1.30 (1.13–1.49)). The SRR (95% CI) per 30 nmol/L increase in 25(OH) D level was 1.41 (1.19–1.67), and 1.57 (0.64–3.86), for basal cell carcinomas (BCCs) and squamous cell carcinomas (SCCs), respectively. However, while we found that vitamin D intake (from diet, supplemental and total) was not associated with risks of melanoma and SCC, vitamin D intake was associated with slightly increased BCC risk, albeit with no heterogeneity across skin cancer type. This meta-analysis suggests positive associations between circulating 25(OH)D level and risk of melanoma and KC, however, this finding is most likely confounded by sun exposure. We found no associations between vitamin D intake skin cancers, except positive associations with BCC risk.

Bacillus Calmette-Guérin (BCG) stimulates changes in dendritic cell surface marker expression in vitamin D-deficient mice

Objective

Vitamin D (VD) deficiency increases susceptibility to tuberculosis and is an important immunomodulator. Dendritic cells (DCs) are important antigen-presenting cells that play a critical role during tuberculosis infection, and Mycobacterium tuberculosis modulates DC responses. The underlying mechanism is poorly understood. Our aim was to study changes in DC surface markers in VD deficient mice administered Bacillus Calmette-Guérin (BCG).

Methods

We divided C57BL/6 mice into a normal group and a VD deficient group. Two groups of mouse bone marrow-derived cells were isolated and cultured with granulocyte-macrophage colony-stimulating factor (20 ng/mL) and interleukin-4 (10 ng/mL) for 6 days. On day 7, BCG (0, 1 or 2 mg/mL) was administered to both groups for 24 hours. Non-adherent cells were harvested to assess DC phenotypic changes induced by different concentrations of BCG.

Results

Expression levels of CD80, MHC-I, MHC-II and CD86 on the surfaces of DCs from VD deficient mice were lower than those in DCs from normal mice. By contrast, the expression level of CD11c on DCs was higher in VD deficient mice than in normal mice. Changes in all factors were concentration-dependent.

Conclusions

These findings indicate that BCG reduced DC surface marker expression to modulate immune responses during M. tuberculosis infection.

Vitamin D Deficiency and Associated Risk Factors in Women from Riyadh, Saudi Arabia

Vitamin D deficiency is an epidemic public health problem worldwide. It is common in the Middle East and is more severe in women. This cross-sectional study was conducted to assess vitamin D deficiency and associated risk factors in women living in Riyadh, Saudi Arabia. Serum 25-hydroxyvitamin D (25(OH)D) was measured in 166 women aged 30-65 years. Socio-demographic, lifestyle and health status characteristics, as well as intake of selected dietary supplements, were collected. Weight and height were measured. Vitamin D deficiency (25(OH)D < 20 ng/mL) was reported in 60.2% of participants. Mean of serum 25(OH)D was 20.7 ng/mL. Older age and taking the supplements of vitamin D, multi-vitamins or calcium were identified as factors that associated with a lower risk of hypovitaminosis D. A national strategy is needed to control a hypovitaminosis D crisis in Saudi Arabia. This could be accomplished by raising public awareness regarding vitamin D, regulating and enhancing vitamin D fortification and supplementation and screening vitamin D status among women at high risk.

Vitamin D metabolism in dogs and cats and its relation to diseases not associated with bone metabolism

Due to the presence of receptors in the cells of numerous body tissues, vitamin D is associated with several physiological functions that go beyond calcium and phosphorus homoeostasis and control of bone metabolism in the body. In humans, several studies have associated lower vitamin D concentrations with numerous diseases, such as cancer, heart disease, autoimmune diseases and infectious diseases, and also with an increase in the total mortality rate of the population. Recently, this nutrient started to gain importance in veterinary medicine, and several articles have shown a correlation between low vitamin D status and diseases unrelated to bone metabolism. The present review aims to highlight the recent publications that investigated this relationship, bringing the evidence that exists so far in dogs and cats.

Nutritional vitamin D in CKD: Should we measure? Should we treat?

Vitamin Ddeficiency is frequently present in patients affected by chronic kidney disease (CKD). Experimental studies demonstrated that Vitamin D may play a role in the pathophysiology of diseases beyond mineral bone disorders in CKD (CKD-MBD). Unfortunately, the lack of large and interventional studies focused on the so called "non-classic" effects of 25(OH) Vitamin D supplementation in CKD patients, doesn't permit to conclude definitely about the beneficial effects of this supplementation in clinical practice. In conclusion, treatment of nutritional vitamin D deficiency in CKD may play a central role in both bone homeostasis and cardiovascular outcomes, but there is not clear evidence to support one formulation of nutritional vitamin D over another in CKD.

Vitamin D for secondary prevention of acute wheeze attacks in preschool and school-age children

INTRODUCTION

Vitamin D is best known for its role in bone health; however, the discovery of the vitamin D receptor and the expression of the gene encoding the vitamin D 1α-hydroxylase (CYP27B1) enzyme in a wide variety of tissues including immune cells and respiratory epithelium has led to the discovery of potential roles for vitamin D in the prevention of acute wheeze.

METHODS

We review here the literature concerning the relationships between circulating 25-hydroxyvitamin D (25(OH)D) concentration and secondary prevention of acute wheeze attacks in preschool and school-age children.

RESULTS

Epidemiological data suggest that vitamin D insufficiency (25(OH)D <75 nmol/L) is highly prevalent in preschool and school-age children with wheeze. Preschool age children with a history of wheeze attacks and circulating 25(OH)D <75 nmol/L are at increased risk and frequency of future acute wheeze. However, no consistent association between low vitamin D status and risk of acute wheeze is reported in school-age children. Seven randomised controlled trials (RCTs) with relatively small sample sizes (30-430) and variable quality showed inconsistent results regarding the effect of oral vitamin D supplementation during childhood on the risk of asthma attacks, asthma symptom control, inhaled corticosteroid requirements, spirometry and unscheduled healthcare attendances for wheeze. A RCT showed that vitamin D supplementation had no effect on the frequency of unplanned healthcare attendances due to acute wheeze in 22 preschool children.

DISCUSSION

An evidence-based recommendation for the use of vitamin D as a preventive therapy for wheeze attacks cannot be made until results of further trials are available. The assessment of circulating 25(OH)D concentration and the optimisation of vitamin D status to prevent acute respiratory tract infections, and to maintain skeletal and general health in preschool and school-age children with acute wheeze is worthwhile in its own right, but whether this will reduce the risk of acute wheeze attacks is unclear.

Hypovitaminosis D: Is It Time to Consider the Use of Calcifediol?

Hypovitaminosis D is becoming a notable health problem worldwide. A consensus exists among several different medical societies as to the need for adequate levels of vitamin D for bone and general health. The correct method by which to restore normal vitamin D levels is still a matter of debate. Although cholecalciferol remains the most commonly distributed form of vitamin D supplementation worldwide, several drugs with vitamin D activity are available for clinical use, and making the correct selection for the individual patient may be challenging. In this narrative review, we aim to contribute to the current knowledge base on the possible and appropriate use of calcifediol-the 25-alpha-hydroxylated metabolite-in relation to its chemical characteristics, its biological properties, and its pathophysiological aspects. Furthermore, we examine the trials that have aimed to evaluate the effect of calcifediol on the restoration of normal vitamin D levels. Calcifediol is more soluble than cholecalciferol in organic solvents, due to its high polarity. Good intestinal absorption and high affinity for the vitamin-D-binding protein positively affect the bioavailability of calcifediol compared with cholecalciferol. In particular, orally administered calcifediol shows a much shorter half-life than oral cholecalciferol. Most findings suggest that oral calcifediol is about three- to five-fold more powerful than oral cholecalciferol, and that it has a higher rate of intestinal absorption. Accordingly, calcifediol can be particularly useful in treating diseases associated with decreased intestinal absorption, as well as obesity (given its lower trapping in the adipose tissue) and potentially neurological diseases treated with drugs that interfere with the hepatic cytochrome P-450 enzyme system, resulting in decreased synthesis of calcifediol. Up to now, there has not been enough clinical evidence for its use in the context of osteoporosis treatment.

Role of CYP1A1, ABCG2, CYP24A1 and VDR gene polymorphisms on the evaluation of cardiac iron overload in thalassaemia patients

OBJECTIVES

Iron-burden-induced arrhythmia and heart failure are among the leading causes of morbidity and mortality in β-thalassaemia major patients. T2* cardiac magnetic resonance remains the only reliable noninvasive method for the heart iron excess assessment. We explored the role of single nucleotide polymorphisms involved in vitamin D metabolism, transport and activity and in deferasirox (DFX) metabolism on cardiac iron burden.

PATIENTS AND METHODS

One hundred and five β-thalassaemia patients, treated with DFX, were enrolled in the present study. Drug plasma Ctrough was measured by a high-performance liquid chromatography-ultraviolet method. Allelic discrimination was carried out using the real-time PCR.

RESULTS

CYP1A1*1189 CC, ABCG2 421 GA, CYP24A1 8620 GG and VDR TaqI CC single nucleotide polymorphisms influenced T2* values. Age, serum ferritin, ABCG2 421 GA, ABCG2 1194 +928 TC/CC, CYP24A1 22776 TT and VDR TaqI TC/CC were retained in linear regression model.

CONCLUSION

Our results suggested, for the first time, the role of DFX and vitamin D pharmacogenetics on cardiac iron overload.

The effect of vitamin D pathway genes and deferasirox pharmacogenetics on liver iron in thalassaemia major patients

Monitoring and treating iron overload is crucial in transfusion-dependent thalassaemia patients. Liver stiffness measurement by transient elastography and T2* magnetic resonance imaging represent non-invasive ways to evaluate the adequacy of the iron chelation treatment. We explored the role of single nucleotide polymorphisms involved in vitamin D metabolism, transport and activity, and in deferasirox metabolism on liver iron burden parameters. One-hundred and five beta-thalassaemia patients, treated with deferasirox, have been enrolled. Drug plasma C_trough and AUC were measured by a HPLC-UV method. Allelic discrimination was performed by real-time PCR. Age, UGT1A1-364 CT/TT and CYP27B1 -1260 GT/TT positively predicted liver stiffness values. Deferasirox dose and serum ferritin negatively predicted T2* data, whereas age and CYP2D6 1457 GG genotype positively influenced these values. The discoveries of this research may be useful for personalized medicine and the proposed method could be applied in patients with hereditary hemochromatosis and myelodysplastic syndromes.

Vitamin D's role in health and disease: How does the present inform our understanding of the past?

While the role of vitamin D in supporting bone homeostasis during growth and maintenance is well substantiated, emerging evidence from ecological and observational studies suggests that a deficiency of vitamin D is associated with some cancers, immune disorders, cardiovascular disease, abnormal glucose metabolism, and neurodegenerative diseases. Biological plausibility for extraskeletal functions originated with the discovery of the vitamin D receptor in many body tissues and knowledge that the conversion of 25-hydroxyvitamin D (25(OH)D) to its active metabolite 1,25(OH)₂D occurs in many cell types in addition to the kidney. The association of vitamin D status in humans as an etiological factor in developmental programming of bone, in some chronic diseases, and in all-cause mortality, in addition to skeletal morbidity, is supported by some but not all observational studies and randomized controlled trials. These clinical observations have implications for paleopathology, both in terms of specific comorbidities and the potential role of vitamin D in individuals who display no evidence for skeletal disease. This paper outlines recent clinical research on vitamin D metabolism and its novel biological roles, and explores the possible relevance to paleopathological research designs, theoretical models, and interpretations of disease experience.

Role of phosphate sensing in bone and mineral metabolism

Inorganic phosphate (P_i) is essential for signal transduction and cell metabolism, and is also an essential structural component of the extracellular matrix of the skeleton. P_i is sensed in bacteria and yeast at the plasma membrane, which activates intracellular signal transduction to control the expression of P_i transporters and other genes that control intracellular P_i levels. In multicellular organisms, P_i homeostasis must be maintained in the organism and at the cellular level, requiring an endocrine and metabolic P_i-sensing mechanism, about which little is currently known. This Review will discuss the metabolic effects of P_i, which are mediated by P_i transporters, inositol pyrophosphates and SYG1-Pho81-XPR1 (SPX)-domain proteins to maintain cellular phosphate homeostasis in the musculoskeletal system. In addition, we will discuss how P_i is sensed by the human body to regulate the production of fibroblast growth factor 23 (FGF23), parathyroid hormone and calcitriol to maintain serum levels of P_i in a narrow range. New findings on the crosstalk between iron and P_i homeostasis in the regulation of FGF23 expression will also be outlined. Mutations in components of these metabolic and endocrine phosphate sensors result in genetic disorders of phosphate homeostasis, cardiomyopathy and familial basal ganglial calcifications, highlighting the importance of this newly emerging area of research.

Associations of Circulating 25-Hydroxyvitamin D3 Concentrations With Incident, Sporadic Colorectal Adenoma Risk According to Common Vitamin D-Binding Protein Isoforms

Concentration of 25-hydroxyvitamin D3 (25(OH)D3), the main circulating form of vitamin D, is inversely associated with incident, sporadic colorectal adenoma risk. We investigated whether this association differs by 2 functional variants in the vitamin D-binding protein (DBP) gene, group-specific component (GC), that encode for common protein isoforms Gc1s, Gc1f, and Gc2 linked to differences in vitamin D metabolism. We pooled data (418 patients with adenoma and 524 polyp-free control subjects) from 3 colonoscopy-based case-control studies (Minnesota, 1991-1994; North Carolina, 1994-1997; South Carolina, 2002). We estimated 25(OH)D3-adenoma associations, stratified by DBP isoforms, using multivariable logistic regression. Higher 25(OH)D3 concentrations were inversely associated with colorectal adenoma risk among those with the Gc2 isoform (per 10-ng/mL increase in 25(OH)D3, odds ratio = 0.71, 95% confidence interval: 0.56, 0.90), but not among those with only Gc1 isoforms (odds ratio = 1.07, 95% confidence interval: 0.87, 1.32; P for interaction = 0.03). Thus, the vitamin D-incident, sporadic colorectal adenoma association may differ by common DBP isoforms, and patients with the Gc2 isoform may particularly benefit from maintaining higher circulating 25(OH)D3 concentrations for adenoma prevention.

Vitamin D in SLE: a role in pathogenesis and fatigue? A review of the literature

Fatigue is a common, disabling problem that is highly prevalent in patients with systemic lupus erythematous (SLE). More recently, vitamin D status has been established as a potential contributor to SLE pathogenesis and manifestations, in particular fatigue. This review summarizes the literature regarding the role of vitamin D in SLE, and provides an overview of the recent literature examining the association between vitamin D and fatigue in patients with SLE. Finally, the role of vitamin D supplementation in the treatment of SLE-related fatigue is considered.

Effect of pharmacogenetic markers of vitamin D pathway on deferasirox pharmacokinetics in children

OBJECTIVES

Patients with β-thalassemia major have extremely low vitamin D levels, owing to reduced intestinal absorption, subicteric tint, and/or iron-induced higher pigmentation. We investigated whether some polymorphisms within the VDR, CYP24A1, CYP27B1, and GC genes could play a role in deferasirox pharmacokinetics in a cohort of pediatric patients.

PATIENTS AND METHODS

Eighteen children with β-thalassemia were enrolled. Drug plasma concentrations at the end of dosing interval (Ctrough) and after 0, 2, 4, 6, and 24 h of drug administration were measured by a HPLC-UV method. Allelic discrimination for VDR (TaqI, FokI, BsmI, Cdx2, and ApaI), CYP24A1 (22776, 3999 and 8620), CYP27B1 (2838 and -1260), and GC (1296) single nucleotide polymorphisms was performed by real-time PCR.

RESULTS

CYP24A1 8620 AG/GG group negatively predicted Ctrough in regression analysis (P=0.012). ApaI AA genotype resulted as a negative predictor of Ctrough (P=0.025) and area under the concentration curve (P=0.007); FoKI CC genotype remained as area under the concentration curve positive predictor (P=0.008) and TC/CC group as half-life (t1/2) (P=0.003) and volume of distribution (Vd) (P=0.011) negative one; TaqI TC/CC was retained as a negative predictor of drug maximum concentration (Cmax) (P=0.004). Moreover, GC 1296 TG/GG seemed able to predict lower time to reach drug maximum concentration (Tmax) (P=0.033).

CONCLUSION

Our preliminary experience suggested the potential usefulness of vitamin D pharmacogenetic to better understand deferasirox interindividual variability, also in pediatric patients.

The genetic determinants of circulating C3-epimers of 25-hydroxyvitamin D

BACKGROUND

The complexity of vitamin D metabolites especially the contribution of C3-epimers of 25-hydroxyvitamin D (C3-epimers) in human sera remains unclear. We hypothesized that genetic polymorphisms in the vitamin D-related gene pathway contribute to variation in C3-epimer levels. Therefore, we investigated candidate single nucleotide polymorphisms (SNPs) concerning C3-epimer levels.

METHODS

The candidate SNPs, including DHCR7/NADSYN1 (rs12785878), CYP2R1 (rs2060793) and GC (rs2282679), were genotyped in 1727 members of the third project of the Electricity Generating Authority of Thailand 3/1 cohort investigation. Each SNP was tested under three genetic effects (dominant, recessive and additive models) concerning the levels of total serum 25(OH)D [the sum of 25(OH)D2+3 and 3-epi-25(OH)D2+3], non-C3-epimers [25(OH)D2+3] and C3-epimers [3-epi-25(OH)D2+3], using linear regression analysis.

RESULTS

Among the participants, the median (range) levels of non-C3-epimers and C3-epimers were 22.7 (6.4-49.2) ng/mL and 1.3 (0.01-14.2) ng/mL, respectively. In regression analysis, we found the genetic variation of two SNPs, the DHCR7/NADSYN1 (rs12785878; G > T) and GC (rs2282679; T > G) under additive genetic models, explained the variation of C3-epimer levels about 1.5% (p = 1.66 × 10-7) and 1.1% (p = 1.10 × 10-5), respectively. Interestingly, participants carrying the minor T-allele of rs12785878 exhibited a trend to increase C3-epimer levels, while those carrying the minor G-allele of rs2282679 exhibited a trend to decrease levels of both non-C3-epimers and C3-epimers. In addition, CYP2R1 (rs2060793; G > A) was clearly associated only with non-C3-epimer levels (p = 2.46 × 10-8). In multivariate analyses, sex, age and BMI were predictors for variation in C3-epimer concentration; sex and age for variation in non-C3-epimers.

CONCLUSION

To the best of our knowledge, this is the first study to demonstrate genetic models concerning the variation in C3-epimer levels. Our results emphasize that genetic determinants and the potential factors of C3-epimers differ from non-C3-epimers. This study contributes fundamental knowledge of the endogenous vitamin D pathway.

Can adverse effects of excessive vitamin D supplementation occur without developing hypervitaminosis D?

Vitamin D is a fat-soluble hormone that has endocrine, paracrine and autocrine functions. Consumption of vitamin D-supplemented food & drugs have increased significantly in the last couple of decades due to campaign and awareness programs. Despite such wide use of artificial vitamin D supplements, serum level of 25 hydroxyvitamin D does not always reflect the amount of uptake. In contrast to the safe sunlight exposure, prolonged and disproportionate consumption of vitamin D supplements may lead to vitamin D intoxication, even without developing hypervitaminosis D. One of the reasons why vitamin D supplementation is believed to be safe is, it rarely raises serum vitamin D levels to the toxic range even after repeated intravenous ingestion of extremely high doses of synthetic vitamin D analogs. However, prolonged consumption of vitamin D supplementation may induce hypercalcemia, hypercalciuria and hyperphosphatemia, which are considered to be the initial signs of vitamin D intoxication. It is likely that calcium and phosphorus dysregulation, induced by exogenous vitamin D supplementation, may lead to tissue and organ damages, even without developing hypervitaminosis D. It is needed to be emphasized that, because of tight homeostatic control of calcium and phosphorus, when hypercalcemia and/or hyperphosphatemia is apparent following vitamin D supplementation, the process of tissue and/or organ damage might already have been started.

Vitamin D-Dependent Rickets Type II with Alopecia: A Rare Case Report

Vitamin D-dependent rickets type II is a rare hereditary disorder. It occurs due to mutations in the gene chr. 12q12-q14, which codes for vitamin D receptor. End-organ resistance to 1,25-(OH)₂ vitamin D3 and alopecia in severe cases are the characteristic features. We report a case of a 4-year-old boy with loss of hair over the scalp and body – first observed after 1 month of birth. The boy also developed difficulty in walking at the age of 2 year. On analysis, reduced serum calcium level (7.5 mg/dL) and elevated alkaline phosphatase level (625 IU/L) were reported. Initially, the treatment included intramuscularly administered single dose of 600,000 IU vitamin D, followed by 400 IU of vitamin D along with 1 g of supplemental calcium every day. Periodic follow-up was conducted for 2 months. Improvement was observed in the biochemical parameters and X-rays of the distal radial and ulnar metaphyses, although no improvement was observed in alopecia.

Vitamin D ratio and glycaemic control in individuals with type 2 diabetes mellitus: A systematic review

Several studies have suggested a favorable role for vitamin D in glycaemic metabolism and its potential as adjuvant treatment of type 2 diabetes mellitus. This review discusses the role of vitamin D in the glycaemic control of individuals with type 2 diabetes mellitus and evaluates the effect of vitamin D supplementation on glycaemic markers in this population. Literature searches were performed in the BIREME, LILACS, and PubMed databases using the Medical Subject Headings and words related to vitamin D, type 2 diabetes mellitus, and glycaemic control. Interventional and observational studies were considered eligible. The evaluation of the included studies was independently performed by 2 evaluators at all stages of selection, data extraction, and bias risk assessment. The primary outcome was the relationship between vitamin D levels and glucose metabolism markers in type 2 diabetes mellitus individuals. The secondary outcome was the effect of vitamin D supplementation on the glycaemic control markers in individuals with type 2 diabetes mellitus. The inverse relationship between vitamin D and variables of glucose metabolism was verified. Interventional studies revealed that vitamin D supplementation did not alter glycaemic control markers in most studies. Few studies have shown positive effects with a significant reduction in the percentage of glycated haemoglobin, insulin, and glucose concentrations, and changes in homeostatic model assessment-insulin resistance and beta cell, and quantitative insulin sensitivity check index. Therefore, despite the association of vitamin D with glucose metabolism, there is insufficient evidence of the beneficial effects of its supplementation on the metabolic control of type 2 diabetes mellitus.

Epilepsy and vitamin D: a comprehensive review of current knowledge

Vitamin D has been considered as neurosteroid, and its pivotal role in neuroprotection, brain development, and immunomodulation has been noticed in studies; however, our knowledge regarding its role in neurological disorders is still developing. The potential role of vitamin D in the pathophysiology and treatment of epilepsy, as one the most prevalent neurological disorders, has received less attention in recent years. In this article, we review the possible relationship between vitamin D and epilepsy from different aspects, including the action mechanism of vitamin D in the central nervous system and ecological and epidemiological findings. We also present the outcome of studies that evaluated the level of vitamin D and the impact of administrating vitamin D in epileptic patients or animal subjects. We also review the current evidence on interactions between vitamin D and antiepileptic drugs.

Role of CYP24A1, VDR and GC gene polymorphisms on deferasirox pharmacokinetics and clinical outcomes

β-Thalassemia patients develop deficiency in vitamin D absorption and liver hydroxylation, resulting in extremely low calcitriol levels. We explored the role of single-nucleotide polymorphisms (SNPs) involved in vitamin D metabolism, transport and activity on deferasirox pharmacokinetics and outcomes (effectiveness trough levels (C_trough) and the area under the curve (AUC) cutoffs of 20 μg ml^-1 and 360 μg ml^-1 h^-1, respectively; nonresponse AUC limit of 250 μg ml^-1 h^-1). Ninety-nine β-thalassemic patients were enrolled. Drug plasma C_trough and AUC were measured by the high-performance liquid chromatography system coupled with an ultraviolet determination method. Allelic discrimination for VDR, CYP24A1, CYP27B1 and GC gene SNPs was performed by real-time PCR. CYP24A1 22776 TT significantly influenced C_min and negatively predicted it in regression analysis. CYP24A1 3999 CC was associated with C_trough and C_min and was a negative predictor of T_max, whereas CYP24A1 8620 GG seemed to have a role in C_trough, AUC, t_1/2 and C_min, and was an AUC negative predictor factor. Considering treatment outcome, Cdx2 and GC 1296 were retained in regression analysis as AUC efficacy cutoff negative predictors.

Simultaneous quantification of 25-hydroxyvitamin D3-3-sulfate and 25-hydroxyvitamin D3-3-glucuronide in human serum and plasma using liquid chromatography-tandem mass spectrometry coupled with DAPTAD-derivatization

25-hydroxyvitamin D₃-3-sulfate (25-OHD₃-S) and 25-hydroxyvitamin D₃-3-glucuronide (25-OHD₃-G) are major conjugative metabolites of vitamin D₃ found in the systemic circulation and potentially important reservoirs for 25-hydroxyvitamin D₃. Simultaneous and accurate quantification of these metabolites could advance assessment of the impact of vitamin D₃ on health and disease. In this study, a highly sensitive and accurate liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for simultaneous quantification of 25-OHD₃-S and 25-OHD₃-G in human serum or plasma. Following protein precipitation, the analytes of interest were partially purified by solid-phase extraction and subjected to derivatization with 4-(4'-dimethylaminophenyl)-1,2,4-triazoline-3,5-dione (DAPTAD). Quantification of the analytes was based on multiple reaction monitoring (MRM) operated in the positive ion mode, and deuterated internal standards were used for each conjugative metabolite. Applying this method to the analysis of 25-OHD₃-S and 25-OHD₃-G concentrations in human serum or plasma samples achieved satisfactory reproducibility, accuracy and sensitivity. We subsequently used this method to simultaneously determine serum concentrations of the two metabolites in archived samples from a rifampin treatment study. Drug treatment had no effect on metabolite concentrations, but significantly increased the 25-OHD₃-S/25-OHD₃ concentration ratio (p=0.01). The availability of this new method should improve sample throughput and our ability to quantify and monitor circulating 25-OHD₃-S and 25-OHD₃-G concentrations.

Role of vitamin D pathway gene polymorphisms on rifampicin plasma and intracellular pharmacokinetics

AIM

We retrospectively evaluate the pharmacogenetic role of single nucleotide polymorphisms involved in rifampicin transport (SLCO1B1, MDR1 and PXR genes) and vitamin D (VDR, CYP24A1 and CYP27B1 genes) metabolism and activity on drug plasma and intracellular concentrations.

PATIENTS & METHODS

Rifampicin C_max and C_trough were measured at weeks 2 and 4 using Ultra-Performance Liquid Chromatography-tandem mass spectroscopy methods. Allelic discrimination was performed by real-time polymerase chain reaction.

RESULTS

Twenty-four patients were enrolled. At week 2, OATP1B1 521TT and CYP27B1 +2838CC/CT considering plasma and BsmIAA for intraperipheral blood mononuclear cells C_max, remained in regression analysis. Concerning week 4, TaqITC/CC and CYP24A1 22776CT/TT were retained in plasma C_max regression model.

CONCLUSION

This study confirms the role of SLCO1B1 and it suggests the involvement of vitamin D pathway gene polymorphisms in rifampicin pharmacokinetics.

Vitamin D status and its associations with rheumatoid arthritis in Korean women: the Korean National Health and Nutrition Examination Survey 2008-2014

In the present study, vitamin D status and its associations with rheumatoid arthritis in Korean women were investigated. Total 2,162 women’s data from the Korea National Health and Nutrition Examination Survey during 2008–2014 ware analyzed by complex sampling design logistic regression analysis and complex sampling design general linear model. Women who over 19 years old were included, and who has osteoporosis or abnormal parathyroid hormone or renal failure or liver cirrhosis or abnormal creatinine were excluded. Age and body mass index were used as covariate. In the present study, we have shown that vitamin D status were not associated with development of rheumatoid arthritis in Korean women as well were not associated with pain and quality of life in Korean women with rheumatoid arthritis. Based on the present study and considering the effects of vitamin D on fracture and osteoporosis, it can be suggested that additional cohort study and cost-effectiveness analysis are needed.

The half-life of 25(OH)D after UVB exposure depends on gender and vitamin D receptor polymorphism but mainly on the start level

The 25(OH)D decrease over time in a group (N= 22) with high 25(OH)D start levels was exponential. The half-life (T_1/2) was 89 days and prolonged in materials with lower 25(OH)D start levels.

High Prevalence of Vitamin D Deficiency among Pregnant Saudi Women

Vitamin D deficiency has emerged as a public health problem worldwide due to its important role in health and disease. The present work is intended to examine prevalence of vitamin D deficiency among pregnant Saudi women and related risk factors. A cross-sectional study was carried out at King Fahad Medical City in Riyadh, Saudi Arabia. Serum 25-hydroxy vitamin D (25(OH)D) was measured by enzyme-linked immunosorbent assay in 160 pregnant women during the first trimester of pregnancy. Socio-demographic, lifestyle and maternal characteristics were collected and vitamin D intake was assessed using a 24-h dietary recall. Weight and height were measured using standardized methods. Vitamin D deficiency (25(OH)D < 50 nmol/L) and insufficiency (25(OH)D = 50–74 nmol/L) were reported in 50% and 43.8% of the study sample, respectively. Median serum 25(OH)D concentration was 49.9 nmol/L. Adequate vitamin D intake (≥600 IU/day) was reported among only 8.1% of pregnant women. Age group, educational level, sun exposure frequency and daytime and daily practice of exercise were significantly associated with vitamin D status. Overall, vitamin D deficiency was common among pregnant Saudi women in Riyadh. Steps should be taken to address the current situation, including increased sunlight exposure, consumption of fatty fish, and vitamin D supplements.

Inhibition of α-glucosidase by vitamin D3 and the effect of vitamins B1 and B2

Vitamin D₃ occupies the active site of α-glucosidase to avoid the entry of the substrate and causes the inhibition of α-glucosidase.

Mechanisms Underlying the Regulation of Innate and Adaptive Immunity by Vitamin D

Non-classical actions of vitamin D were first suggested over 30 years ago when receptors for the active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), were detected in various tissues and cells that are not associated with the regulation of calcium homeostasis, including activated human inflammatory cells. The question that remained was the biological significance of the presence of vitamin D receptors in the different tissues and cells and, with regard to the immune system, whether or not vitamin D plays a role in the normal immune response and in modifying immune mediated diseases. In this article findings indicating that vitamin D is a key factor regulating both innate and adaptive immunity are reviewed with a focus on the molecular mechanisms involved. In addition, the physiological significance of vitamin D action, as suggested by in vivo studies in mouse models is discussed. Together, the findings indicate the importance of 1,25(OH)2D3 as a regulator of key components of the immune system. An understanding of the mechanisms involved will lead to potential therapeutic applications for the treatment of immune mediated diseases.

Vitamin D and 1,25(OH)2D regulation of T cells

Vitamin D is a direct and indirect regulator of T cells. The mechanisms by which vitamin D directly regulates T cells are reviewed and new primary data on the effects of 1,25 dihydroxyvitamin D (1,25(OH)2D) on human invariant natural killer (iNK)T cells is presented. The in vivo effects of vitamin D on murine T cells include inhibition of T cell proliferation, inhibition of IFN-γ, IL-17 and induction of IL-4. Experiments in mice demonstrate that the effectiveness of 1,25(OH)2D requires NKT cells, IL-10, the IL-10R and IL-4. Comparisons of mouse and human T cells show that 1,25(OH)2D inhibits IL-17 and IFN-γ, and induces T regulatory cells and IL-4. IL-4 was induced by 1,25(OH)2D in mouse and human iNKT cells. Activation for 72 h was required for optimal expression of the vitamin D receptor (VDR) in human and mouse T and iNKT cells. In addition, T cells are potential autocrine sources of 1,25(OH)2D but again only 48-72 h after activation. Together the data support the late effects of vitamin D on diseases like inflammatory bowel disease and multiple sclerosis where reducing IL-17 and IFN-γ, while inducing IL-4 and IL-10, would be beneficial.

Chronic high fructose intake reduces serum 1,25 (OH)2D3 levels in calcium-sufficient rodents

Excessive fructose consumption inhibits adaptive increases in intestinal Ca²⁺ transport in lactating and weanling rats with increased Ca²⁺ requirements by preventing the increase in serum levels of 1,25(OH)₂D₃. Here we tested the hypothesis that chronic fructose intake decreases 1,25(OH)₂D₃ levels independent of increases in Ca²⁺ requirements. Adult mice fed for five wk a high glucose-low Ca²⁺ diet displayed expected compensatory increases in intestinal and renal Ca²⁺ transporter expression and activity, in renal CYP27B1 (coding for 1α-hydroxylase) expression as well as in serum 1,25(OH)₂D₃ levels, compared with mice fed isocaloric glucose- or fructose-normal Ca²⁺ diets. Replacing glucose with fructose prevented these increases in Ca²⁺ transporter, CYP27B1, and 1,25(OH)₂D₃ levels induced by a low Ca²⁺ diet. In adult mice fed for three mo a normal Ca²⁺ diet, renal expression of CYP27B1 and of CYP24A1 (24-hydroxylase) decreased and increased, respectively, when the carbohydrate source was fructose instead of glucose or starch. Intestinal and renal Ca²⁺ transporter activity and expression did not vary with dietary carbohydrate. To determine the time course of fructose effects, a high fructose or glucose diet with normal Ca²⁺ levels was fed to adult rats for three mo. Serum levels of 1,25(OH)₂D₃ decreased and of FGF23 increased significantly over time. Renal expression of CYP27B1 and serum levels of 1,25(OH)₂D₃ still decreased in fructose- compared to those in glucose-fed rats after three mo. Serum parathyroid hormone, Ca²⁺ and phosphate levels were normal and independent of dietary sugar as well as time of feeding. Thus, chronically high fructose intakes can decrease serum levels of 1,25(OH)₂D₃ in adult rodents experiencing no Ca²⁺ stress and fed sufficient levels of dietary Ca²⁺. This finding is highly significant because fructose constitutes a substantial portion of the average diet of Americans already deficient in vitamin D.