Physiologic and pathophysiologic roles of extra renal CYP27b1: Case report and review

Vitamin D and systemic lupus erythematosus: Causality and association with disease activity and therapeutics

The major role of bioactive vitamin 1,25-dihydroxyvitamin D3 (1,25(OH)2D or calcitriol) is to maintain the levels of calcium and phosphorus to achieve bone and mineral homeostasis. Dietary intake and adequate natural light exposure are the main contributors to normal vitamin D status. In addition to regulating metabolism, vitamin D exerts various immunomodulatory effects that regulate innate and adaptive immunity through immune effector cells such as monocytes, macrophages, T and B lymphocytes, and natural killer cells and nonimmune cells that express vitamin D receptors. Systemic lupus erythematosus (SLE) is an autoimmune disease with an unknown etiology, and the association between vitamin D and SLE remains incompletely understood. Given that the current treatment for SLE relies heavily on corticosteroids and that SLE patients tend to have low vitamin D status, vitamin D supplementation may help to reduce the dosage of corticosteroids and/or attenuate disease severity. In this review, we address the associations between vitamin D and several clinical aspects of SLE. In addition, the underlying immunomodulatory mechanisms accounting for the potential vitamin D-mediated therapeutic effects are discussed. Finally, several confounding factors in data interpretation and the execution of clinical trials and perspectives targeting vitamin D supplementation in patients with SLE are also addressed.

Vitamin D supplementation and calcium: Many-faced gods or nobody in fighting against Corona Virus Disease 2019

In December 2019, Corona Virus Disease 2019 (COVID-19) was first identified and designated as a pandemic in March 2020 due to rapid spread of the virus globally. At the beginning of the pandemic, only a few treatment options, mainly focused on supportive care and repurposing medications, were available. Due to its effects on immune system, vitamin D was a topic of interest during the pandemic, and researchers investigated its potential impact on COVID-19 outcomes. However, the results of studies about the impact of vitamin D on the disease are inconclusive. In the present narrative review, different roles of vitamin D regarding the COVID-19 have been discussed to show that vitamin D supplementation should be recommended carefully.

Insight into vitamin D3 action within the ovary-Basic and clinical aspects

Vitamin D3 is a fat-soluble secosteroid predominantly synthesized in the skin or delivered with a diet. Nevertheless, recently it is considered more as a hormone than a vitamin due to its pleiotropic function within the organism ensured by widely distributed vitamin D receptors and metabolic enzymes. Besides the main role in calcium and phosphorus homeostasis, vitamin D3 was shown to regulate many cellular and metabolic processes in normal and cancerous tissues within the immune system, the cardiovascular system, the respiratory system and the endocrine system. The ovary is an important extraskeletal tissue of vitamin D3 action and local metabolism, indicating its role in the regulation of ovarian functions upon physiological and pathological conditions. This chapter reviews firstly the updated information about vitamin D3 metabolism and triggered intracellular pathways. Furthermore, the basic information about ovarian physiology and several aspects of vitamin D3 effects within the ovary are presented. Finally, the special attention is paid into possible mechanism of vitamin D3 action within ovarian pathologies such as premature ovarian failure, polycystic ovary syndrome, and ovarian cancer, considering its clinical application as alternative therapy.

Consensus Statement on Vitamin D Status Assessment and Supplementation: Whys, Whens, and Hows

The 6th International Conference, "Controversies in Vitamin D," was convened to discuss controversial topics, such as vitamin D metabolism, assessment, actions, and supplementation. Novel insights into vitamin D mechanisms of action suggest links with conditions that do not depend only on reduced solar exposure or diet intake and that can be detected with distinctive noncanonical vitamin D metabolites. Optimal 25-hydroxyvitamin D (25(OH)D) levels remain debated. Varying recommendations from different societies arise from evaluating different clinical or public health approaches. The lack of assay standardization also poses challenges in interpreting data from available studies, hindering rational data pooling and meta-analyses. Beyond the well-known skeletal features, interest in vitamin D's extraskeletal effects has led to clinical trials on cancer, cardiovascular risk, respiratory effects, autoimmune diseases, diabetes, and mortality. The initial negative results are likely due to enrollment of vitamin D-replete individuals. Subsequent post hoc analyses have suggested, nevertheless, potential benefits in reducing cancer incidence, autoimmune diseases, cardiovascular events, and diabetes. Oral administration of vitamin D is the preferred route. Parenteral administration is reserved for specific clinical situations. Cholecalciferol is favored due to safety and minimal monitoring requirements. Calcifediol may be used in certain conditions, while calcitriol should be limited to specific disorders in which the active metabolite is not readily produced in vivo. Further studies are needed to investigate vitamin D effects in relation to the different recommended 25(OH)D levels and the efficacy of the different supplementary formulations in achieving biochemical and clinical outcomes within the multifaced skeletal and extraskeletal potential effects of vitamin D.

The Power of Vitamin D: Is the Future in Precision Nutrition through Personalized Supplementation Plans?

In the last few decades, vitamin D has undeniably been one of the most studied nutrients. Despite our ability to produce vitamin D through sunlight exposure, its presence in several natural food sources and fortified foods, and its widespread availability as a dietary supplement, vitamin D deficiency is a serious public health problem, affecting nearly 50% of the global population. Low serum levels of vitamin D are being associated with increased susceptibility to numerous health conditions, including respiratory infections, mental health, autoimmune diseases, and different cancer types. Although the association between vitamin D status and health is well-established, the exact beneficial effects of vitamin D are still inconclusive and indefinite, especially when considering the prevention and treatment of different health conditions and the determination of an appropriate dosage to exert those beneficial effects in various population groups. Therefore, further research is needed. With constant improvements in our understanding of individual variations in vitamin D metabolism and requirements, in the future, precision nutrition and personalized supplementation plans could prove beneficial.

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.

Vitamin D3 Receptors and Metabolic Enzymes in Hen Reproductive Tissues

In recent years, vitamin D3 has been revealed as an important regulator of reproductive processes in humans and livestock; however, its role in the female reproductive system of poultry is poorly known. The aim of this study was to examine vitamin D3 receptor (VDR and PDIA3) and metabolic enzyme (1α-hydroxylase and 24-hydroxylase) mRNA transcript and protein abundances, and protein localization within the hen ovary, oviductal shell gland, pituitary, liver, and kidney. We demonstrated, for the first time, the patterns of the relative mRNA and protein abundances of examined molecules in the ovary, dependent on follicle development and the layer of follicle wall, as well as in other examined organs. Immunohistochemically, PDIA3, 1α-hydroxylase, and 24-hydroxylase are localized in follicular theca and granulosa layers, luminal epithelium and tubular glands of the shell gland, pituitary, liver, and kidney. These results indicate that reproductive tissues have both receptors, VDR, primarily involved in genomic action, and PDIA3, probably participating in the rapid, non-genomic effect of vitamin D3. The finding of 1α-hydroxylase and 24-hydroxylase expression indicates that the reproductive system of chickens has the potential for vitamin D3 synthesis and inactivation, and may suggest that locally produced vitamin D3 can be considered as a significant factor in the orchestration of ovarian and shell gland function in hens. These results provide a new insight into the potential mechanisms of vitamin D3 action and metabolism in the chicken ovary and oviduct.

Vitamin D and depression in older adults: lessons learned from observational and clinical studies

Depression is a mental disorder triggered by the interaction of social, psychological and biological factors that have an important impact on an individual's life. Despite being a well-studied disease with several established forms of treatment, its prevalence is increasing, especially among older adults. New forms of treatment and prevention are encouraged, and some researchers have been discussing the effects of vitamin D (VitD) on depression; however, the exact mechanism by which VitD exerts its effects is not yet conclusive. In this study, we aimed to discuss the possible mechanisms underlying the association between VitD and depression in older adults. Therefore, we conducted a systematic search of databases for indexed articles published until 30 April 2021. The primary focus was on both observational studies documenting the association between VitD and depression/depressive symptoms, and clinical trials documenting the effects of VitD supplementation on depression/depressive symptoms, especially in older adults. Based on pre-clinical, clinical and observational studies, it is suggested that the maintenance of adequate VitD concentrations is an important issue, especially in older adults, which are a risk population for both VitD deficiency and depression. Nevertheless, it is necessary to carry out more studies using longitudinal approaches in low- and middle-income countries to develop a strong source of evidence to formulate guidelines and interventions.

Does Native Vitamin D Supplementation Have Pleiotropic Effects in Patients with End-Stage Kidney Disease? A Systematic Review of Randomized Trials

Vitamin D has been shown to have multiple pleiotropic effects beyond bone and mineral metabolism, with purported roles in cardiovascular disease, cancer, and host immunity. Vitamin D deficiency is common in patients with end-stage kidney disease (ESKD); however, current clinical practice has favored the use of the active hormone. Whether vitamin D deficiency should be corrected in patients with ESKD remains unclear, as few randomized trials have been conducted. In this systematic review, we summarize the current evidence examining whether vitamin D supplementation improves outcomes, beyond mineral metabolism, in patients with ESKD. Data from randomized controlled trials of adults with ESKD were obtained by searching Ovid MEDLINE, Embase, the Cochrane Central Register of Controlled Trials, and the Web of Science Core Collection from inception to February 2023. Twenty-three trials composed of 2489 participants were identified for inclusion. Data were synthesized by two independent reviewers and summarized in tables organized by outcome. Outcomes included measures of mortality, cardiovascular disease, inflammation, muscle strength/function, nutrition, patient well-being, and outcomes specific to ESKD including erythropoietin usage, pruritus, and dialysis access maturation. The Cochrane risk of Bias Tool (RoB 2, 2019) was used to assess study quality. Overall, our findings indicate a minimal and varied benefit of native vitamin D supplementation. From the largest studies included, we determine that vitamin D has no demonstrated effect on patient-reported measures of well-being or utilization of erythropoietin, nor does it change levels of the inflammation biomarker C-reactive protein. Included trials were heterogeneous with regards to outcomes, and the majority studied small participant populations with a relatively short follow-up. We conclude that vitamin D supplementation corrects vitamin D deficiency and is safe and well-tolerated in humans with ESKD. However, it is not clear from clinical trials conducted to date that a causal pathway exists between 25(OH)D and pleiotropic effects that is responsive to vitamin D treatment.

Vitamin D and Vitamin D-Binding Protein in Health and Disease

Vitamin D is a fat-soluble secosteroid that exists in two forms: vitamin D₂ and vitamin D₃ [...].

Genetic Variations of the Vitamin D Metabolic Pathway and COVID-19 Susceptibility and Severity: Current Understanding and Existing Evidence

The immunomodulatory and metabolic effects of vitamin D receptor (VDR) activation have been considered beneficial in mitigating the susceptibility and severity of COVID-19 infection. Furthermore, vitamin D-binding protein (DBP) has pleiotropic effects on the immune system that may influence inflammation associated with COVID-19. Multiple observational studies have demonstrated an association between low levels of serum 25-hydroxyvitamin D and risk and the severity of COVID-19 infection. However, the impact of vitamin D supplementation as an adjunctive treatment for COVID-19 based on evidence from randomized clinical trials is unclear. Equally important is that certain variations of the genes involved in the vitamin D metabolic pathway have been shown to affect immune function and linked with various clinical outcomes, including cardio-metabolic disorders, autoimmune diseases, infections, and cancers. This indicates inter-individual difference in body response to vitamin D. There is also emerging evidence that common polymorphisms of these genes may influence the susceptibility and severity of COVID-19, although the confidence of these findings is limited by a small number of studies and participants. Further studies are needed to address the potential role of VDR activation and DBP in the pathophysiology of COVID-19 which take into account the genetic variations of vitamin D metabolic pathway.

Vitamin D and Bone: A Story of Endocrine and Auto/Paracrine Action in Osteoblasts

Despite its rigid structure, the bone is a dynamic organ, and is highly regulated by endocrine factors. One of the major bone regulatory hormones is vitamin D. Its renal metabolite 1α,25-OH2D3 has both direct and indirect effects on the maintenance of bone structure in health and disease. In this review, we describe the underlying processes that are directed by bone-forming cells, the osteoblasts. During the bone formation process, osteoblasts undergo different stages which play a central role in the signaling pathways that are activated via the vitamin D receptor. Vitamin D is involved in directing the osteoblasts towards proliferation or apoptosis, regulates their differentiation to bone matrix producing cells, and controls the subsequent mineralization of the bone matrix. The stage of differentiation/mineralization in osteoblasts is important for the vitamin D effect on gene transcription and the cellular response, and many genes are uniquely regulated either before or during mineralization. Moreover, osteoblasts contain the complete machinery to metabolize active 1α,25-OH2D3 to ensure a direct local effect. The enzyme 1α-hydroxylase (CYP27B1) that synthesizes the active 1α,25-OH2D3 metabolite is functional in osteoblasts, as well as the enzyme 24-hydroxylase (CYP24A1) that degrades 1α,25-OH2D3. This shows that in the past 100 years of vitamin D research, 1α,25-OH2D3 has evolved from an endocrine regulator into an autocrine/paracrine regulator of osteoblasts and bone formation.

Ketogenic Diet and Vitamin D Metabolism: A Review of Evidence

The ketogenic diet (KD), which is low in carbohydrates and high to normal in fat and protein, has been traditionally used in epilepsy for the last 100 years. More recently, its application in obesity has been introduced. The present review aimed to investigate the effects of the KD on vitamin D. In total, five studies were done in healthy adults, one in subjects with type 2 diabetes, and seven in subjects with epilepsy that assessed the levels of vitamin D pre- and post-intervention. In the majority of studies, increases in circulating vitamin D were reported. The relationship of the KD with vitamin D was explained through several mechanisms: ketone bodies, macronutrient intake, the status levels of other fat-soluble vitamins, weight loss, changes in the hormonal milieu, and effects on gut microbiota. Moreover, potential nutrient-gene-related interactions were discussed. There is still a need to conduct multiple arm studies to compare the effects of the KD versus other diets and better decipher the particular effects of the KD on vitamin D levels and metabolism. Moreover, differentiations of the diet's effects according to sex and genetic makeup should be investigated to prescribe KDs on a more personalized basis.

Vitamin D: sources, physiological role, biokinetics, deficiency, therapeutic use, toxicity, and overview of analytical methods for detection of vitamin D and its metabolites

Vitamin D has a well-known role in the calcium homeostasis associated with the maintenance of healthy bones. It increases the efficiency of the intestinal absorption of dietary calcium, reduces calcium losses in urine, and mobilizes calcium stored in the skeleton. However, vitamin D receptors are present ubiquitously in the human body and indeed, vitamin D has a plethora of non-calcemic functions. In contrast to most vitamins, sufficient vitamin D can be synthesized in human skin. However, its production can be markedly decreased due to factors such as clothing, sunscreens, intentional avoidance of the direct sunlight, or the high latitude of the residence. Indeed, more than one billion people worldwide are vitamin D deficient, and the deficiency is frequently undiagnosed. The chronic deficiency is not only associated with rickets/osteomalacia/osteoporosis but it is also linked to a higher risk of hypertension, type 1 diabetes, multiple sclerosis, or cancer. Supplementation of vitamin D may be hence beneficial, but the intake of vitamin D should be under the supervision of health professionals because overdosing leads to intoxication with severe health consequences. For monitoring vitamin D, several analytical methods are employed, and their advantages and disadvantages are discussed in detail in this review.

Vitamin D and Beta Cells in Type 1 Diabetes: A Systematic Review

The prevalence of type 1 diabetes (T1D) is rising steadily. A potential contributor to the rise is vitamin D. In this systematic review, we examined the literature around vitamin D and T1D. We identified 22 papers examining the role of vitamin D in cultured β-cell lines, islets, or perfused pancreas, and 28 papers examining vitamin D in humans or human islets. The literature reports strong associations between T1D and low circulating vitamin D. There is also high-level (systematic reviews, meta-analyses) evidence that adequate vitamin D status in early life reduces T1D risk. Several animal studies, particularly in NOD mice, show harm from D-deficiency and benefit in most studies from vitamin D treatment/supplementation. Short-term streptozotocin studies show a β-cell survival effect with supplementation. Human studies report associations between VDR polymorphisms and T1D risk and β-cell function, as assessed by C-peptide. In view of those outcomes, the variable results in human trials are generally disappointing. Most studies using 1,25D, the active form of vitamin D were ineffective. Similarly, studies using other forms of vitamin D were predominantly ineffective. However, it is interesting to note that all but one of the studies testing 25D reported benefit. Together, this suggests that maintenance of optimal circulating 25D levels may reduce the risk of T1D and that it may have potential for benefits in delaying the development of absolute or near-absolute C-peptide deficiency. Given the near-complete loss of β-cells by the time of clinical diagnosis, vitamin D is much less likely to be useful after disease-onset. However, given the very low toxicity of 25D, and the known benefits of preservation of C-peptide positivity for long-term complications risk, we recommend considering daily cholecalciferol supplementation in people with T1D and people at high risk of T1D, especially if they have vitamin D insufficiency.

An Overview of the Current Known and Unknown Roles of Vitamin D3 in the Female Reproductive System: Lessons from Farm Animals, Birds, and Fish

Recent studies have clearly shown that vitamin D₃ is a crucial regulator of the female reproductive process in humans and animals. Knowledge of the expression of vitamin D₃ receptors and related molecules in the female reproductive organs such as ovaries, uterus, oviduct, or placenta under physiological and pathological conditions highlights its contribution to the proper function of the reproductive system in females. Furthermore, vitamin D₃ deficiency leads to serious reproductive disturbances and pathologies including ovarian cysts. Although the influence of vitamin D₃ on the reproductive processes of humans and rodents has been extensively described, the association between vitamin D₃ and female reproductive function in farm animals, birds, and fish has rarely been summarized. In this review, we provide an overview of the role of vitamin D₃ in the reproductive system of those animals, with special attention paid to the expression of vitamin D₃ receptors and its metabolic molecules. This updated information could be essential for better understanding animal physiology and overcoming the incidence of infertility, which is crucial for optimizing reproductive outcomes in female livestock.

Megalin and Vitamin D Metabolism—Implications in Non-Renal Tissues and Kidney Disease

Megalin is an endocytic receptor abundantly expressed in proximal tubular epithelial cells and other calciotropic extrarenal cells expressing vitamin D metabolizing enzymes, such as bone and parathyroid cells. The receptor functions in the uptake of the vitamin D-binding protein (DBP) complexed to 25 hydroxyvitamin D3 (25(OH)D3), facilitating the intracellular conversion of precursor 25(OH)D3 to the active 1,25 dihydroxyvitamin D3 (1,25(OH)2D3). The significance of renal megalin-mediated reabsorption of 25(OH)D3 and 1,25(OH)2D3 has been well established experimentally, and other studies have demonstrated relevant roles of extrarenal megalin in regulating vitamin D homeostasis in mammary cells, fat, muscle, bone, and mesenchymal stem cells. Parathyroid gland megalin may regulate calcium signaling, suggesting intriguing possibilities for megalin-mediated cross-talk between calcium and vitamin D regulation in the parathyroid; however, parathyroid megalin functionality has not been assessed in the context of vitamin D. Within various models of chronic kidney disease (CKD), megalin expression appears to be downregulated; however, contradictory results have been observed between human and rodent models. This review aims to provide an overview of the current knowledge of megalin function in the context of vitamin D metabolism, with an emphasis on extrarenal megalin, an area that clearly requires further investigation.

Physiologically Based Pharmacokinetic Modeling of Vitamin D3 and Metabolites in Vitamin D-Insufficient Patients

A physiologically based pharmacokinetic (PBPK) model of vitamin D3 and metabolites [25(OH)D3, 1,25(OH)2D3, and 24,25(OH)2D3] is presented. In this study, patients with 25(OH)D3 plasma concentrations below 30 ng/ml were studied after a single dose of 5000 I.U. (125 µg) cholecalciferol, provided with 5000 I.U. daily cholecalciferol supplementation until vitamin D replete [25(OH)D3 plasma concentrations above 30 ng/ml], and had serial plasma samples were collected at each phase for 14 days. Total concentrations of vitamin D3 and metabolites were measured by ultra-high performance liquid chromatography tandem mass spectrometry. A nine-compartment PBPK model was built using MATLAB to represent the triphasic study nature (insufficient, replenishing, and sufficient). The stimulatory and inhibitory effect of 1,25(OH)2D3 were incorporated by fold-changes in the primary metabolic enzymes CYP27B1 and CYP24A1, respectively. Incorporation of dynamic adipose partition coefficients for vitamin D3 and 25(OH)D3 and variable enzymatic reactions aided in model fitting. Measures of model predictions agreed well with data from metabolites, with 97%, 88%, and 98% of the data for 25(OH)D3, 24,25(OH)2D3, and 1,25(OH)2D3, respectively, within twofold of unity (fold error values between 0.5 and 2.0). Bootstrapping was performed and optimized parameters were reported with 95% confidence intervals. This PBPK model could be a useful tool for understanding the connections between vitamin D and its metabolites under a variety of clinical situations. SIGNIFICANCE STATEMENT: This study developed a physiologically based pharmacokinetic (PBPK) model of vitamin D3 and metabolites for patients moving from an insufficient to a repleted state over a period of 16 weeks.

25-hydroxyvitamin D-1α-hydroxylase (CYP27B1) induces ectopic calcification

Vascular calcification is an important pathogenesis related to cardiovascular disease and high mortality rate in chronic kidney disease (CKD) patients. It has been well-known that hyper-phosphatemia induces osteochondrogenic transition of vascular smooth muscle cells (VSMCs) resulting ectopic calcification in aortic media, cardiac valve, and kidney. However, the detailed mechanism of the ectopic calcification has been not clarified yet. Here, we found that the co-localization of CYP27B1 with the calcified lesions of aorta and arteries in kidney of klotho mutant (kl/kl) mice, and then investigated the role of CYP27B1 in the mineralization of the VSMCs. Under high phosphate condition, overexpression of CYP27B1 induced calcification and osteocalcin mRNA expression in the VSMCs. Inversely, siRNA-CYP27B1 inhibited high phosphate-induced calcification of the VSMCs. We also found that the accumulated CYP27B1 protein was glycosylated in the kidney of kl/kl mice. Therefore, overexpression of CYP27B1-N310A and CYP27B1-T439A, which are a mutation for N-linked glycosylation site (N310A) and a mutation for O-linked glycosylation site (T439A) in CYP27B1, decreased calcium deposition and expression of RUNX2 induced by high phosphate medium in VSMCs compared with wild-type CYP27B1. These results suggest that extra-renal expression of glycosylated CYP27B1 would be required for ectopic calcification of VSMCs under hyperphosphatemia.

Salt inducible kinases and PTH1R action

Parathyroid hormone is a central regulator of calcium homeostasis. PTH protects the organism from hypocalcemia through its actions in bone and kidney. Recent physiologic studies have revealed key target genes for PTH receptor (PTH1R) signaling in these target organs. However, the complete signal transduction cascade used by PTH1R to accomplish these physiologic actions has remained poorly defined. Here we will review recent studies that have defined an important role for salt inducible kinases downstream of PTH1R in bone, cartilage, and kidney. PTH1R signaling inhibits the activity of salt inducible kinases. Therefore, direct SIK inhibitors represent a promising novel strategy to mimic PTH actions using small molecules. Moreover, a detailed understanding of the molecular circuitry used by PTH1R to exert its biologic effects will afford powerful new models to better understand the diverse actions of this important G protein coupled receptor in health and disease.

Frequency of Vitamin D Deficiency and Associated Factors in Long-term Bariatric Surgery Patients: a Cross-sectional Study

BACKGROUND

Vitamin D deficiency is a common consequence of bariatric surgery (BS). However, few studies have evaluated influential factors and to date there are no studies investigating individual ultraviolet B (UVB) radiation levels in BS patients. This study aimed to evaluate vitamin D deficiency and its associated factors, including UVB radiation, in Roux-Y gastric bypass (RYGB) patients.

METHODS

This study included 104 adults (90.4% female) at least 5 years after RYGB. Patients underwent surgery in private hospitals (Private; n = 47) or in two public hospitals, one with ongoing outpatient care (Active; n = 17), and the other with discontinued service for BS (Discontinued; n = 40). 25-hydroxyvitamin D (25(OH)D) concentrations were analyzed by chemiluminescence, individual UVB radiation levels by dosimeter badges. Vitamin D intake, anthropometric, skin phototype, sociodemographic and lifestyle patterns were also assessed.

RESULTS

Mean age was 49.6 ± 9.1 years and post-operative period 8.7 ± 2.2 years. The prevalence of 25(OH)D deficiency and insufficiency was 25.0% and 51.9% respectively. 25(OH)D concentration differed among the hospitals (private = 26.2 ± 8.5; active = 28.7 ± 11.4; discontinued = 23.5 ± 6.5 ng/mL; p = 0.038). A total of 26.2% of the variance observed in 25(OH)D concentrations was explained by daily UVB radiation levels (β = 0.224; p = 0.032) and vitamin D intake (β = 0.431; p < 0.001), controlling for age and BMI.

CONCLUSION

A quarter of the evaluated patients presented vitamin D deficiency, which was associated with the discontinuation of the health care, higher BMI, lower vitamin D intake, and lower individual UVB radiation levels.

Vitamin D3 Metabolic Enzymes in the Porcine Uterus: Expression, Localization and Autoregulation by 1,25(OH)2D3 In Vitro

The role of vitamin D₃ has been confirmed in female reproductive organs. This study aimed to examine vitamin D₃ metabolic enzymes, i.e., CYP27B1 and CYP24A1, mRNA transcript and protein abundance, and protein localization in the uterus of pigs on days 2–5, 10–12, 15–16 and 18–20 of the estrous cycle. Additionally, we determined 1,25(OH)₂D₃ concentration in uterine flushings and the effect of 1,25(OH)₂D₃ (10, 50 and 100 ng/mL) in vitro on CYP27B1 and CYP24A1 mRNA transcript abundance in endometrial and myometrial slices. In the endometrium, a greater CYP27B1 mRNA transcript abundance was noted on days 10–12 and 18–20 than on days 15–16, whereas encoded protein abundance was greater on days 18–20 when compared to days 15–16. Endometrial CYP24A1 mRNA transcript abundance was greater on days 18–20 than on days 10–12 and 15–16. In the myometrium, CYP27B1 mRNA transcript abundance was greater on days 18–20 than on days 2–5 and 15–16, while protein abundance was larger in slices collected on days 18–20 than on days 15–16. Neither CYP24A1 mRNA transcript nor encoded protein abundance were detected in the myometrium. The highest 1,25(OH)₂D₃ concentration in uterine flushings was observed on days 18–20. Furthermore, the 1,25(OH)₂D₃ increased the abundance of the CYP24A1 mRNA transcript in endometrial slices. Overall, our results suggest that porcine uterus is an extra-renal site of vitamin D₃ metabolism. Both the endometrium and the myometrium possess the ability to synthesize vitamin D₃, while only the endometrium contributes to its catabolism.

Is There a Crucial Link Between Vitamin D Status and Inflammatory Response in Patients With COVID-19?

Background

Hypovitaminosis D has been suggested to play a possible role in coronavirus disease 2019 (COVID-19) infection.

Methods

The aim of this study is to analyze the relationship between vitamin D status and a biochemical panel of inflammatory markers in a cohort of patients with COVID-19. A secondary endpoint was to evaluate the correlation between 25OHD levels and the severity of the disease. Ninety-three consecutive patients with COVID-19-related pneumonia were evaluated from March to May 2020 in two hospital units in Pisa, in whom biochemical inflammatory markers, 25OHD levels, P/F ratio at nadir during hospitalization, and complete clinical data were available.

Results

Sixty-five percent of patients presented hypovitaminosis D (25OHD ≤ 20 ng/ml) and showed significantly higher IL-6 [20.8 (10.9-45.6) vs. 12.9 (8.7-21.1) pg/ml, p = 0.02], CRP [10.7 (4.2-19.2) vs. 5.9 (1.6-8.1) mg/dl, p = 0.003], TNF-α [8.9 (6.0-14.8) vs. 4.4 (1.5-10.6) pg/ml, p = 0.01], D-dimer [0.53 (0.25-0.72) vs. 0.22 (0.17-0.35) mg/l, p = 0.002], and IL-10 [3.7 (1.8-6.9) vs. 2.3 (0.5-5.8) pg/ml, p = 0.03]. A significant inverse correlation was found between 25OHD and all these markers, even adjusted for age and sex. Hypovitaminosis D was prevalent in patients with severe ARDS, compared with the other groups (75% vs. 68% vs. 55%, p < 0.001), and 25OHD levels were lower in non-survivor patients.

Conclusions

The relationship between 25OHD levels and inflammatory markers suggests that vitamin D status needs to be taken into account in the management of these patients. If vitamin D is a marker of poor prognosis or a possible risk factor with beneficial effects from supplementation, this still needs to be elucidated.

Serum Vitamin D as a Biomarker in Autoimmune, Psychiatric and Neurodegenerative Diseases

Vitamin D is a steroid hormone regulating calcium-phosphorus homeostasis, immune response and brain function. In the past thirty years, an increasing number of cohort studies, meta-analyses and randomized controlled trials (RTCs) evaluated the serum levels of 25-hydroxyvitamin D [25(OH)D], which is considered the Vitamin D status biomarker, in patients affected by neurological, psychiatric and autoimmune diseases. Although an association between low 25(OH)D serum levels and the prevalence of these diseases has been found, it is still unclear whether the serum 25(OH)D measurement can be clinically useful as a biomarker for diagnosis, prognosis and predicting treatment response in neurodegeneration, mental illness and immune-mediated disorders. The lack of standardized data, as well as discrepancies among the studies (in the analytical methods, cut-offs, endpoints and study sets), weakened the findings achieved, hindered pooling data, and, consequently, hampered drawing conclusions. This narrative review summarizes the main findings from the studies performed on serum 25(OH)D in neurological, psychiatric and autoimmune diseases, and clarifies whether or not serum 25(OH)D can be used as a reliable biomarker in these diseases.

Hypercalcemia Associated with the Ectopic Expression of 25-hydroxyvitamin D3-1α-hydroxylase in Diffuse Large B-cell Lymphoma

An 82-year-old man was transferred to our hospital due to impaired consciousness. His albumin-corrected calcium level was 14.2 mg/dL, intact parathyroid hormone (PTH) and PTH-related protein levels were reduced, and his 1,25-dihydroxyvitamin D [1,25 (OH) ₂VitD] level was elevated at 71.5 pg/mL. Computed tomography revealed masses on the bilateral ribs. The mass on the rib was biopsied and diagnosed as diffuse large B-cell lymphoma (DLBCL). Immunostaining of the biopsy sample with the anti-CYP27B1 antibody revealed the ectopic expression of 1α-hydroxylase in the lesion. We herein report a rare case of hypercalcemia induced by the overproduction of 1,25 (OH) ₂VitD in DLBCL ectopically expressing 1α-hydroxylase.

Transcriptome-Wide Profile of 25-Hydroxyvitamin D3 in Primary Immune Cells from Human Peripheral Blood

Vitamin D₃ is an essential micronutrient mediating pleiotropic effects in multiple tissues and cell types via its metabolite 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃), which activates the transcription factor vitamin D receptor. In this study, we used peripheral blood mononuclear cells (PBMCs) obtained from five healthy adults and investigated transcriptome-wide, whether the precursor of 1,25(OH)₂D₃, 25-hydroxyvitamin D₃ (25(OH)D₃), has gene regulatory potential on its own. Applying thresholds of >2 in fold change of gene expression and <0.05 as a false discovery rate, in this ex vivo approach the maximal physiological concentration of 25(OH)D₃ (250 nM (nmol/L)) none of the study participants had a significant effect on their PBMC transcriptome. In contrast, 1000 and 10,000 nM 25(OH)D₃ regulated 398 and 477 genes, respectively, which is comparable to the 625 genes responding to 10 nM 1,25(OH)₂D₃. The majority of these genes displayed specificity to the tested individuals, but not to the vitamin D metabolite. Interestingly, the genes MYLIP (myosin regulatory light chain interacting protein) and ABCG1 (ATP binding cassette subfamily G member 1) showed to be specific targets of 10,000 nM 25(OH)D₃. In conclusion, 100- and 1000-fold higher 25(OH)D₃ concentrations than the reference 10 nM 1,25(OH)₂D₃ are able to affect the transcriptome of PBMCs with a profile comparable to that of 1,25(OH)₂D₃.

Role of Vitamin D in Cognitive Dysfunction: New Molecular Concepts and Discrepancies between Animal and Human Findings

PURPOSE OF REVIEW

increasing evidence suggests that besides the several metabolic, endocrine, and immune functions of 1alpha,25-dihydroxyvitamin D (1,25(OH)2D), the neuronal effects of 1,25(OH)2D should also be considered an essential contributor to the development of cognition in the early years and its maintenance in aging. The developmental disabilities induced by vitamin D deficiency (VDD) include neurological disorders (e.g., attention deficit hyperactivity disorder, autism spectrum disorder, schizophrenia) characterized by cognitive dysfunction. On the other hand, VDD has frequently been associated with dementia of aging and neurodegenerative diseases (e.g., Alzheimer's, Parkinson's disease).

RECENT FINDINGS

various cells (i.e., neurons, astrocytes, and microglia) within the central nervous system (CNS) express vitamin D receptors (VDR). Moreover, some of them are capable of synthesizing and catabolizing 1,25(OH)2D via 25-hydroxyvitamin D 1alpha-hydroxylase (CYP27B1) and 25-hydroxyvitamin D 24-hydroxylase (CYP24A1) enzymes, respectively. Both 1,25(OH)2D and 25-hydroxyvitamin D were determined from different areas of the brain and their uneven distribution suggests that vitamin D signaling might have a paracrine or autocrine nature in the CNS. Although both cholecalciferol and 25-hydroxyvitamin D pass the blood-brain barrier, the influence of supplementation has not yet demonstrated to have a direct impact on neuronal functions. So, this review summarizes the existing evidence for the action of vitamin D on cognitive function in animal models and humans and discusses the possible pitfalls of therapeutic clinical translation.

Rethinking Fragility Fractures in Type 2 Diabetes: The Link between Hyperinsulinaemia and Osteofragilitas

Patients with type 2 diabetes mellitus (T2DM) and/or cardiovascular disease (CVD), conditions of hyperinsulinaemia, have lower levels of osteocalcin and bone remodelling, and increased rates of fragility fractures. Unlike osteoporosis with lower bone mineral density (BMD), T2DM bone fragility "hyperinsulinaemia-osteofragilitas" phenotype presents with normal to increased BMD. Hyperinsulinaemia and insulin resistance positively associate with increased BMD and fragility fractures. Hyperinsulinaemia enforces glucose fuelling, which decreases NAD+-dependent antioxidant activity. This increases reactive oxygen species and mitochondrial fission, and decreases oxidative phosphorylation high-energy production capacity, required for osteoblasto/cytogenesis. Osteocytes directly mineralise and resorb bone, and inhibit mineralisation of their lacunocanalicular space via pyrophosphate. Hyperinsulinaemia decreases vitamin D availability via adipocyte sequestration, reducing dendrite connectivity, and compromising osteocyte viability. Decreased bone remodelling and micropetrosis ensues. Trapped/entombed magnesium within micropetrosis fossilisation spaces propagates magnesium deficiency (MgD), potentiating hyperinsulinaemia and decreases vitamin D transport. Vitamin D deficiency reduces osteocalcin synthesis and favours osteocyte apoptosis. Carbohydrate restriction/fasting/ketosis increases beta-oxidation, ketolysis, NAD+-dependent antioxidant activity, osteocyte viability and osteocalcin, and decreases excess insulin exposure. Osteocalcin is required for hydroxyapatite alignment, conferring bone structural integrity, decreasing fracture risk and improving metabolic/endocrine homeodynamics. Patients presenting with fracture and normal BMD should be investigated for T2DM and hyperinsulinaemia.

Investigation of the effects of dietary supplementation with 25-hydroxyvitamin D3 and vitamin D3 on indicators of vitamin D status in healthy dogs

OBJECTIVE

To compare the effects of short-term dietary supplementation with vitamin D₃ and 25-hydroxyvitamin D₃ (25[OH]D₃) on indicators of vitamin D status in healthy dogs.

ANIMALS

13 purpose-bred adult dogs.

PROCEDURES

20 extruded commercial dog foods were assayed for 25(OH)D₃ content. Six dogs received a custom diet containing low vitamin D concentrations and consumed a treat with vitamin D₂ (0.33 μg/kg^0.75) plus 1 of 3 doses of 25(OH)D₃ (0, 0.23, or 0.46 μg/kg^0.75) once daily for 8 weeks followed by the alternate treatments in a crossover-design trial. In another crossover-design trial, 7 dogs received a custom diet supplemented with vitamin D₃ or 25(OH)D₃ (targeted content, 3,250 U/kg [equivalent to 81.3 μg/kg] and 16 μg/kg, respectively, as fed) for 10 weeks followed by the alternate treatment. In washout periods before each trial and between dietary treatments in the second trial, dogs received the trial diet without D-vitamer supplements. Dietary intake was monitored. Serum or plasma concentrations of vitamin D metabolites and biochemical variables were analyzed at predetermined times.

RESULTS

25(OH)D₃ concentrations were low or undetected in evaluated commercial diets. In the first trial, vitamin D₂ intake resulted in quantifiable circulating concentrations of 25-hydroxyvitamin D₂ but not 24R,25-dihydroxyvitamin D₂. Circulating 25(OH)D₃ concentration appeared to increase linearly with 25(OH)D₃ dose. In the second trial, circulating 25(OH)D₃ concentration increased with both D vitamer-supplemented diets and did not differ significantly between treatments. No evidence of vitamin D excess was detected in either trial.

CONCLUSIONS AND CLINICAL RELEVANCE

Potency of the dietary 25(OH)D₃ supplement estimated on the basis of targeted content was 5 times that of vitamin D₃ to increase indicators of vitamin D status in the study sample. No adverse effects attributed to treatment were observed in short-term feeding trials.

Systemic Jak1 activation causes extrarenal calcitriol production and skeletal alterations provoking stunted growth

Mineral homeostasis is regulated by a complex network involving endocrine actions by calcitriol, parathyroid hormone (PTH), and FGF23 on several organs including kidney, intestine, and bone. Alterations of mineral homeostasis are found in chronic kidney disease and other systemic disorders. The interplay between the immune system and the skeletal system is not fully understood, but cytokines play a major role in modulating calcitriol production and function. One of the main cellular signaling pathways mediating cytokine function is the Janus kinase (JAK)--signal transducer and activator of transcription (STAT) pathway. Here, we used a mouse model (Jak1^S645P+/- ) that resembles a constitutive activating mutation of the Jak1/Stat3 signaling pathway in humans, and shows altered mineral metabolism, with higher fibroblast growth factor 23 (FGF23) levels, lower PTH levels, and higher calcitriol levels. The higher calcitriol levels are probably due to extrarenal calcitriol production. Furthermore, systemic Jak1/Stat3 activation led to growth impairment and skeletal alterations. The growth plate in long bones showed decreased chondrocyte proliferation rates and reduced height of terminal chondrocytes. Furthermore, we demonstrate that Jak1 is also involved in bone remodeling early in life. Jak1^S645P+/- animals have decreased bone and cortical volume, imbalanced bone remodeling, reduced MAP kinase signaling, and local inflammation. In conclusion, Jak1 plays a major role in bone health probably both, directly and systemically by regulating mineral homeostasis. Understanding the role of this signaling pathway will contribute to a better knowledge in bone growth and in mineral physiology, and to the development of selective Jak inhibitors as osteoprotective agents.

Expression of renal vitamin D receptors and metabolizing enzymes in IgA nephropathy

AIM

One of the main causes of end-stage renal disease (ESRD) in the world is IgA nephropathy (IgAN). Since kidney is a key player in vitamin D metabolism, we investigated the expression of renal vitamin D receptors (VDR) and metabolizing enzymes in IgA nephropathy patients (IgAN-P).

METHODS

The sample included twelve IgAN-P who underwent ultrasound-guided renal biopsies and five controls who underwent nephrectomy due to clear renal carcinoma. Immunofluorescent staining was used to determine the expression of VDR, 25-hydroxyvitamin D3 -alpha-hydroxylase (1alpha-OHase) and vitamin D3 24-hydroxylase (CYP24A1).

RESULTS

Significant increase in expression of VDR, which was prominent in distal tubular cells (DTCs) in tissues from IgAN-P, was found in comparison to the controls (p = 0.0368). The expression of 1alpha-OHase, calcitriol synthesizing enzyme, was significantly lower in IgAN-P, in comparison with controls (p < 0.0001). The opposite, expression of CYP24A1 (vitamin D degrading enzyme), was significantly higher in IgAN-P in comparison with controls (p = 0.0003). Additionally, we found significant negative correlation between percentage of CYP24A1 immunoreactive nuclei in proximal tubular cells (PTCs) and estimated glomerular filtration rate (eGFR) in IgAN-P (r = -0.6139; p = 0.0337).

CONCLUSIONS

Our research indicates substantially decreased renal calcitriol production and increased vitamin D degradation in kidneys of IgAN-P, but larger studies are needed to confirm our results.

Evaluation of expression of VDR-associated lncRNAs in COVID-19 patients

BACKGROUND

Coronavirus disease 2019 (COVID-19) has been shown to cause serious health problems among them is the Acute Respiratory Distress syndrome (ARDS). Vitamin D receptor (VDR) signaling possibly partakes in the pathophysiology of this devastating complication.

METHODS

In the current project, we have appraised expression levels of VDR, CYP27B1 and a number of associated lncRNAs in the circulation of COVID-19 patients versus healthy subjects using real-time PCR method.

RESULTS

Expression of SNHG6 was considerably lower in COVID-19 patients compared with control subjects (Ratio of mean expression (RME) = 0.22, P value = 7.04E-05) and in both female and male COVID-19 patients compared with sex-matched unaffected individuals (RME = 0.32, P value = 0.04 and RME = 0.16, P value = 0.000679683, respectively). However, its expression was similar among ICU-hospitalized and non-ICU patients. Similarly, expression of SNHG16 was lower in in COVID-19 patients compared with controls (RME = 0.20, P value = 5.94E-05) and in both female and male patients compared with sex-matched controls (RME = 0.32, P value = 0.04 and RME = 0.14, P value = 0.000496435, respectively) with no significant difference among ICU-hospitalized and non-ICU hospitalized patients. Expression of VDR was lower in COVID-19 patients compared with controls (RME = 0.42, P value = 0.04) and in male patients compared with male controls (RME = 0.27, P value = 0.02). Yet, expression of VDR was statistically similar between female subgroups and between ICU-hospitalized and non-ICU hospitalized patients. Expression levels CYP27B, Linc00511 and Linc00346 were similar among COVID-19 patients and healthy subjects or between their subgroups. Significant correlations have been detected between expression levels of VDR, CYP27B and SNHG6, SNHG16, Linc00511 and Linc00346 lncRNAs both among COVID-19 patients and among healthy controls with the most significant ones being SNHG6 and SNHG16 (r = 0.74, P value = 3.26e-17 and r = 0.81, P = 1.54e-22, respectively).

CONCLUSION

Combination of transcript levels of VDR, CYP27B and SNHG6, SNHG16, Linc00511 and Linc00346 could differentiate patients from controls with AUC = 0.76, sensitivity = 0.62 and specificity = 0.81. The current data potentiate SNHG6, SNHG16 and VDR as possible contributors in COVID-19 infection but not in the severity of ARDS.

Vitamin D: Possible Therapeutic Roles in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a unique type of liver cancer instigated by underlying liver diseases. Pre-clinical evidence suggests that HCC progression, like other cancers, could be aided by vitamin D deficiency. Vitamin D is a lipid-soluble hormone usually obtained through sunlight. Vitamin D elucidates its biological responses by binding the vitamin D receptor; thus, promoting skeletal mineralization, and maintain calcium homeostasis. Other reported Vitamin D functions include specific roles in proliferation, angiogenesis, apoptosis, inflammation, and cell differentiation. This review highlighted studies on vitamin D's functional roles in HCC and discussed the specific therapeutic targets from various in vivo, in vitro and clinical studies over the years. Furthermore, it described recent advancements in vitamin D's anticancer effects and its metabolizing enzymes' roles in HCC development. In summary, the review elucidated specific vitamin D-associated target genes that play critical functions in the inhibition of tumorigenesis through inflammation, oxidative stress, invasion, and apoptosis in HCC progression.

Altered expression of the vitamin D metabolizing enzymes CYP27B1 and CYP24A1 under the context of prostate aging and pathologies

Low circulating levels of vitamin D are common at older ages and have been linked to an increased risk of prostate disease, including cancer. However, it has not yet been determined whether aging affects the ability of prostate cells to locally metabolize vitamin D into its active metabolite calcitriol and thus mediate the vitamin D signaling in autocrine and paracrine ways. By using a suitable rat model to interrogate spontaneous prostatic modifications over the course of aging, here we showed that both CYP27B1 and CYP24A1 enzymes, which are key players respectively involved with calcitriol synthesis and deactivation, were highly expressed in the prostate epithelium. Furthermore, as the animals aged, a drastic reduction of CYP27B1 levels was detected in total protein extracts and especially in epithelial areas of lesions, including tumors. On the other hand, CYP24A1 expression significantly increased with aging and remained elevated even in altered epithelia. Such intricate unbalance in regard to vitamin D metabolizing enzymes was strongly associated with reduced bioavailability of calcitriol in the senile prostate, which in addition to decreased expression of the vitamin D receptor, further limits the protective actions mediated by vitamin D signaling. This evidence was corroborated by the increased proliferative activity exactly at sites of lesions where the factors implicated with calcitriol synthesis and responsiveness had its expression inhibited. Taken together, our results emphasize a set of modifications over the course of aging with a high potential to hamper vitamin D signaling on the prostate. These findings highlight a crosstalk between vitamin D, aging, and prostate carcinogenesis, offering new potential targets in the prevention of malignancies and other aging-related disorders arising in the gland.

Calcitriol-mediated hypercalcemia as an immune-related adverse event in a patient receiving nivolumab and ipilimumab for metastatic renal cell carcinoma, case report

BACKGROUND

Severe hypercalcemia is often associated with uncontrolled malignancy through several mechanisms. However, calcitriol-mediated hypercalcemia is a rare etiology for advanced solid tumors.

CASE PRESENTATION

We report a case of calcitriol-mediated hypercalcemia secondary to immune checkpoint inhibition in a responder with metastatic clear cell renal cell carcinoma (ccRCC). In this case, a 68 year old male with metastatic ccRCC to the liver within 4 months of right radical nephrectomy went on to develop hypercalcemia (12.8 mg/dL) shortly following 2 cycles of nivolumab and ipilimumab. Additional testing showed an elevated calcitriol level (142 pg/mL), low parathyroid hormone (PTH) and parathyroid hormone-related protein (PTHrP) levels, and a normal 25-hydroxyvitamin D level. FDG-PET imaging showed hypermetabolic mediastinal, hilar, and intra-abdominal lymphadenopathy, however the subsequent lymph node biopsy only showed reactive lymphoid cells without malignancy or granuloma. The hypercalcemia was resistant to initial therapy with calcitonin, hydration, and zoledronic acid but quickly responded to high-dose prednisone (1 mg/kg), followed by normalization of calcitriol levels. The patient was rechallenged with nivolumab and ipilimumab which provided a partial response after 4 cycles. He was maintained on low dose prednisone (10 mg daily) leading to a sustained resolution of his hypercalcemia.

CONCLUSION

This case suggests calcitriol-mediated hypercalcemia as a novel immune-related adverse event.

The Role of Vitamin D as a Biomarker in Alzheimer's Disease

Vitamin D and cognition is a popular association, which led to a remarkable body of literature data in the past 50 years. The brain can synthesize, catabolize, and receive Vitamin D, which has been proved to regulate many cellular processes in neurons and microglia. Vitamin D helps synaptic plasticity and neurotransmission in dopaminergic neural circuits and exerts anti-inflammatory and neuroprotective activities within the brain by reducing the synthesis of pro-inflammatory cytokines and the oxidative stress load. Further, Vitamin D action in the brain has been related to the clearance of amyloid plaques, which represent a feature of Alzheimer Disease (AD), by the immune cell. Based on these considerations, many studies have investigated the role of circulating Vitamin D levels in patients affected by a cognitive decline to assess Vitamin D’s eventual role as a biomarker or a risk factor in AD. An association between low Vitamin D levels and the onset and progression of AD has been reported, and some interventional studies to evaluate the role of Vitamin D in preventing AD onset have been performed. However, many pitfalls affected the studies available, including substantial discrepancies in the methods used and the lack of standardized data. Despite many studies, it remains unclear whether Vitamin D can have a role in cognitive decline and AD. This narrative review aims to answer two key questions: whether Vitamin D can be used as a reliable tool for diagnosing, predicting prognosis and response to treatment in AD patients, and whether it is a modifiable risk factor for preventing AD onset.

Probing the Scope and Mechanisms of Calcitriol Actions Using Genetically Modified Mouse Models

Genetically modified mice have provided novel insights into the mechanisms of activation and inactivation of vitamin D, and in the process have provided phenocopies of acquired human disease such as rickets and osteomalacia and inherited diseases such as pseudovitamin D deficiency rickets, hereditary vitamin D resistant rickets, and idiopathic infantile hypercalcemia. Both global and tissue-specific deletion studies leading to decreases of the active form of vitamin D, calcitriol [1,25(OH)2D], and/or of the vitamin D receptor (VDR), have demonstrated the primary role of calcitriol and VDR in bone, cartilage and tooth development and in the regulation of mineral metabolism and of parathyroid hormone (PTH) and FGF23, which modulate calcium and phosphate fluxes. They have also, however, extended the spectrum of actions of calcitriol and the VDR to include, among others: modulation, jointly and independently, of skin metabolism; joint regulation of adipose tissue metabolism; cardiovascular function; and immune function. Genetic studies in older mice have also shed light on the molecular mechanisms underlying the important role of the calcitriol/VDR pathway in diseases of aging such as osteoporosis and cancer. In the course of these studies in diverse tissues, important upstream and downstream, often tissue-selective, pathways have been illuminated, and intracrine, as well as endocrine actions have been described. Human studies to date have focused on acquired or genetic deficiencies of the prohormone vitamin D or the (generally inactive) precursor metabolite 25-hyrodxyvitamin D, but have yet to probe the pleiotropic aspects of deficiency of the active form of vitamin D, calcitriol, in human disease. © 2020 American Society for Bone and Mineral Research © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Mitochondria, Oxidative Stress, cAMP Signalling and Apoptosis: A Crossroads in Lymphocytes of Multiple Sclerosis, a Possible Role of Nutraceutics

Multiple sclerosis (MS) is a complex inflammatory and neurodegenerative chronic disease that involves the immune and central nervous systems (CNS). The pathogenesis involves the loss of blood–brain barrier integrity, resulting in the invasion of lymphocytes into the CNS with consequent tissue damage. The MS etiology is probably a combination of immunological, genetic, and environmental factors. It has been proposed that T lymphocytes have a main role in the onset and propagation of MS, leading to the inflammation of white matter and myelin sheath destruction. Cyclic AMP (cAMP), mitochondrial dysfunction, and oxidative stress exert a role in the alteration of T lymphocytes homeostasis and are involved in the apoptosis resistance of immune cells with the consequent development of autoimmune diseases. The defective apoptosis of autoreactive lymphocytes in patients with MS, allows these cells to perpetuate, within the CNS, a continuous cycle of inflammation. In this review, we discuss the involvement in MS of cAMP pathway, mitochondria, reactive oxygen species (ROS), apoptosis, and their interaction in the alteration of T lymphocytes homeostasis. In addition, we discuss a series of nutraceutical compounds that could influence these aspects.

Altered vitamin D metabolic system in follicular cysts of sows

This study aimed to examine 25OHD₃ concentration in the fluid of follicular and follicular lutein cysts of sows in comparison with preovulatory follicles as well as immunolocalize vitamin D metabolic enzymes (CYP27B1 and CYP24A1) and determine their protein abundances in the cyst wall. We have shown for the first time that 25OHD₃ level in the fluid of both cyst types was significantly lower than in preovulatory follicles. Furthermore, we have demonstrated CYP27B1 and CYP24A1 protein immunolocalization and abundance in follicular and follicular lutein cysts. The abundance of protein for both metabolic enzymes was decreased in ovarian cysts when compared to preovulatory follicles. We propose that altered VD metabolism in ovarian cyst might associate with their formation in sows.

Vitamin D3 in ovarian antral follicles of mature gilts: Expression of its receptors and metabolic enzymes, concentration in follicular fluid and effect on steroid secretion in vitro

Recent studies have reported that vitamin D₃ (VD) regulates ovarian function under physiological and pathological conditions. Due to a lack of information concerning the expression of VD-related molecules (receptors: VDR, PDIA3, and metabolic enzymes: CYP27B1, CYP24A1) in the porcine ovary, this research aimed to determine the mRNA expression, protein abundance and localization of VDR, PDIA3, CYP27B1 and CYP24A1 in small (SFs), medium (MFs) and large (LFs) antral follicles of sexually mature gilts. We also examined the concentration of active VD in the follicular fluid of SFs, MFs and LFs, and the effect of 1,25(OH)₂D₃ on their steroidogenic activity in vitro. In the present study, we have demonstrated for the first time the patterns of VDR, PDIA3, CYP27B1 and CYP24A1 immunolocalization in porcine antral follicles of different sizes. Furthermore, the expression of VD-related molecules was influenced by follicle developmental stage. VDR and PDIA3 mRNA expression and protein abundance decreased with the follicle size: they were the greatest in SFs, and the lowest in LFs. CYP27B1 mRNA expression was the highest in MFs and differed from that in SFs, whereas protein abundance was greater in MFs and SFs than in LFs. The expression of mRNA for CYP24A1 was higher in MFs than in SFs and LFs, while protein abundance did not differ between follicle classes. We have also described changes in the concentration of 1,25(OH)₂D₃ in the follicular fluid of antral follicles with its highest level in MFs. These findings show that the porcine antral follicle is a target tissue for direct VD action and is a local site of VD metabolism. Furthermore, we found that 1,25(OH)₂D₃ increased the secretion of progesterone and estradiol-17β by SFs and MFs in vitro, implying a crucial role of VD in the regulation of ovarian steroidogenesis in mature gilts. Therefore, VD appears to be an important intraovarian factor that could regulate follicular development and function in pigs.

Vitamin D oral gel for prevention of radiation-induced oral mucositis: A randomized clinical trial

OBJECTIVES

The aim of this clinical trial is to evaluate the effectiveness of topical oral vitamin D gel in prevention of radiation-induced oral mucositis.

MATERIAL AND METHODS

A three-armed randomized controlled clinical trial on forty-five head and neck cancer patients was conducted. First group: conventional treatment. Second group: Topical oral vitamin D gel. Third group: topical oral vitamin D gel plus the conventional treatment. All the patients were examined clinically three and six weeks after the start of radiotherapy for pain and WHO mucositis score.

RESULTS

After 6 weeks of radiotherapy, (33.5%) the patients in control group developed high-grade severity of oral mucositis while the patients in the two-test groups "vitamin D group and combined therapy group" remained with low-grade severity or with complete remission. Mean pain scores showed a significant decrease in the combined therapy group and to a close degree in vitamin D group rather than the control group.

CONCLUSION

Topical oral vitamin D gel has a beneficial effect in lowering oral mucositis development and in reducing pain sensation during the radiation period especially when combined with conventional therapeutic agents.

Is vitamin D receptor a druggable target for non-alcoholic steatohepatitis?

Nonalcoholic steatohepatitis (NASH) is a progressed stage of non-alcoholic fatty liver disease, and available therapeutic strategies for NASH are limited. Vitamin D receptor (VDR) is proposed as a druggable target for NASH due to the discovery of vitamin D deficiency in NASH patients. To date, vitamin D supplementation has not consistently conferred expected therapeutic benefits, raising the question of whether VDR can serve as a proper drug target for NASH. It is known that VDR can interact with other ligands such as bile acids in addition to vitamin D, and its expression can be induced by fatty acids, and insulin. It has also been shown that while activation of VDR in hepatic macrophages and hepatic stellate cells resulted in attenuation of hepatic inflammation and fibrosis, activation of VDR in hepatocytes could accelerate lipid accumulation. Thus, the multiplicity of VDR ligands, together with the cell type-specificity of VDR activation, must be taken into consideration in assessing the validity of VDR being a potential druggable target for NASH treatment. To this end, we have evaluated the relationship between VDR activation and various contributing factors, such as gut microbiota, bile acid, fatty acids, and insulin, in addition to vitamin D, with an expectation that a potential drug might be identified that can elicit VDR activation in a tissue- and/or cell type-specific manner and therefore achieving therapeutic benefits in NASH.

Vitamin D Status Modulates Inflammatory Response in HIV+ Subjects: Evidence for Involvement of Autophagy and TG2 Expression in PBMC

Conflicting results on the involvement of vitamin D deficiency in inflammatory and immune response in HIV+ subjects are reported. We aimed to characterize the possible influence of vitamin D status on changes in expression of tissue transglutaminase gene (TGM2) and other genes involved in inflammatory response and autophagy in peripheral blood mononuclear cells (PBMC) from HIV+ subjects. HIV+ subjects (n = 57) under antiretroviral therapy (ART) and healthy controls (n = 40) were enrolled. mRNA levels of 1-alpha-hydroxylase (CYP27B1), tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), TGM2, microtubule-associated protein 1A/1B-light chain 3 (LC3), autophagy-related 5 homolog (ATG5), and Beclin 1 (BECN1) were quantified by real-time PCR. In HIV+ subjects, 25(OH)D₃ plasma levels were negatively correlated with time since HIV diagnosis. In PBMC from HIV+ subjects, increases in gene expression of TNF-α and IFN-γ in comparison to controls were observed. The highest increase in TNF-α transcripts was observed in HIV+ subjects with deficient 25(OH)D₃ levels. Autophagy-related genes LC3, ATG5, and BECN1 were down-regulated in HIV+ subjects. Moreover, TGM2 transcripts were up-regulated in PBMC from HIV+ subjects with 25(OH)D3 deficiency. Changes observed in PBMC from HIV+ subjects appeared to be dependent on vitamin D status. The present results suggest that vitamin D deficiency is associated with changes in the expression of markers of inflammation and autophagy, resulting in immune cell dysfunction.

An Update on Vitamin D Metabolism

Vitamin D is a steroid hormone classically involved in the calcium metabolism and bone homeostasis. Recently, new and interesting aspects of vitamin D metabolism has been elucidated, namely the special role of the skin, the metabolic control of liver hydroxylase CYP2R1, the specificity of 1α-hydroxylase in different tissues and cell types and the genomic, non-genomic and epigenomic effects of vitamin D receptor, which will be addressed in the present review. Moreover, in the last decades, several extraskeletal effects which can be attributed to vitamin D have been shown. These beneficial effects will be here summarized, focusing on the immune system and cardiovascular system.

Vitamin D and Cardiovascular Disease, with Emphasis on Hypertension, Atherosclerosis, and Heart Failure

Vitamin D deficiency is the most common nutritional deficiency, affecting almost one billion people worldwide. Vitamin D is mostly known for its role in intestinal calcium absorption and bone mineralization. However, the observation of seasonal changes in blood pressure and the subsequent identification of vitamin D receptor (VDR) and 1α-hydroxylase in cardiomyocytes, as well as endothelial and vascular smooth muscle cells, implicated a role of vitamin D in the cardiovascular system. Animal studies provided compelling evidence that vitamin D signaling is essential for cardiovascular integrity, especially for the regulation of vascular tone and as an antifibrotic and antihypertrophic signaling pathway in the heart. In addition, observational studies reported an association between vitamin D deficiency and risk of hypertension, atherosclerosis, and heart failure. However, recent clinical intervention studies failed to prove the causal relationship between vitamin D supplementation and beneficial effects on cardiovascular health. In this review, we aim to highlight our current understanding of the role of vitamin D in the cardiovascular system and to find potential explanations for the large discrepancies between the outcome of experimental studies and clinical intervention trials.

Vitamin D receptor stimulation to reduce acute respiratory distress syndrome (ARDS) in patients with coronavirus SARS-CoV-2 infections: Revised Ms SBMB 2020_166

Coronavirus infection is a serious health problem awaiting an effective vaccine and/or antiviral treatment. The major complication of coronavirus disease 2019 (COVID-19), the Acute Respiratory Distress syndrome (ARDS), is due to a variety of mechanisms including cytokine storm, dysregulation of the renin-angiotensin system, neutrophil activation and increased (micro)coagulation. Based on many preclinical studies and observational data in humans, ARDS may be aggravated by vitamin D deficiency and tapered down by activation of the vitamin D receptor. Several randomized clinical trials using either oral vitamin D or oral Calcifediol (25OHD) are ongoing. Based on a pilot study, oral calcifediol may be the most promising approach. These studies are expected to provide guidelines within a few months.

Vitamin D in COVID - 19: Dousing the fire or averting the storm? - A perspective from the Asia-Pacific

COVID-19, the acute respiratory tract infection (RTI) caused by the Coronavirus, Sars-CoV-2, has swept around the world. No country has been spared from its onslaught. Treatments that can reduce the risk of infection and mortality from the disease are desperately needed. Though high quality randomized controlled trials are lacking, some observational and interventional studies that explore the link between vitamin D and RTIs exist. Vitamin D modulates both innate as well as adaptive immunity and may potentially prevent or mitigate the complications associated with RTIs. Evidence linking vitamin D to COVID-19 include that the outbreak occurred in winter in the northern hemisphere at a time when vitamin D levels are lowest in resident populations, that blacks and minority ethnic individuals who are known to have lower levels of vitamin D appear to be disproportionately affected and have more severe complications from the disease, that vitamin D deficiency has been shown to contribute to acute respiratory distress syndrome and that case fatality rates increase with age and in populations with comorbid conditions such as diabetes, hypertension, and cardiovascular disease, all of which are associated with lower vitamin D levels. This narrative review summarizes the current knowledge about the epidemiology and pathophysiology of COVID-19, the evidence linking vitamin D and RTIs, especially COVID-19, the mechanistic reasons behind the possible protective effect of vitamin D in COVID-19, and the evidence with regard to vitamin D supplementation in RTIs. It concludes with some recommendations regarding supplementation of vitamin D in patients with COVID-19.

Spatial Localization of Vitamin D Metabolites in Mouse Kidney by Mass Spectrometry Imaging

Vitamin D plays a key role in the maintenance of calcium/phosphate homeostasis and elicits biological effects that are relevant to immune function and metabolism. It is predominantly formed through UV exposure in the skin by conversion of 7-dehydrocholsterol (vitamin D3). The clinical biomarker, 25-hydroxyvitamin D (25-(OH)-D), is enzymatically generated in the liver with the active hormone 1,25-dihydroxyvitamin D then formed under classical endocrine control in the kidney. Vitamin D metabolites are measured in biomatrices by liquid chromatography-tandem mass spectrometry (LC-MS/MS). In LC-MS/MS, chemical derivatization (CD) approaches have been employed to achieve the desired limit of quantitation. Recently, matrix-assisted laser desorption/ionization (MALDI) has also been reported as an alternative method. However, these quantitative approaches do not offer any spatial information. Mass spectrometry imaging (MSI) has been proven to be a powerful tool to image the spatial distribution of molecules from the surface of biological tissue sections. On-tissue chemical derivatization (OTCD) enables MSI to image molecules with poor ionization efficiently. In this technical report, several derivatization reagents and OTCD methods were evaluated using different MSI ionization techniques. Here, a method for detection and spatial distribution of vitamin D metabolites in murine kidney tissue sections using an OTCD-MALDI-MSI platform is presented. Moreover, the suitability of using the Bruker ImagePrep for OTCD-based platforms has been demonstrated. Importantly, this method opens the door for expanding the range of other poor ionizable molecules that can be studied by OTCD-MSI by adapting existing CD methods.

The vitamin D activator CYP27B1 is upregulated in muscle fibers in denervating disease and can track progression in amyotrophic lateral sclerosis

Extra-renal expression of Cytochrome P450 Family 27 Subfamily B Member 1 (CYP27B1) has been well recognized and reflects the importance of intracrine/paracrine vitamin D signaling in different tissues under physiological and pathological conditions. In a prior RNA sequencing project, we identified CYP27B1 mRNA as upregulated in muscle samples from patients with amyotrophic lateral sclerosis (ALS) compared to normal controls. Our aims here were: (1) to validate this finding in a larger sample set including disease controls, (2) to determine which cell type is expressing CYP27B1 protein in muscle tissue, (3) to correlate CYP27B1 mRNA expression with disease progression in the SOD1G93A ALS mouse and in ALS patients. We assessed CYP27B1 expression by qPCR, western blot, and immunohistochemistry in a repository of muscle samples from ALS, disease controls (myopathy and non-ALS neuropathic disease), normal subjects, and muscle samples from the SOD1G93A mouse. Eight ALS patients were studied prospectively over 6-12 months with serial muscle biopsies. We found that CYP27B1 mRNA and protein levels were significantly increased in ALS versus normal and myopathy muscle samples. Neuropathy samples had increased CYP27B1 mRNA and protein expression but at a lower level than the ALS group. Immunohistochemistry showed that CYP27B1 localized to myofibers, especially those with features of denervation. In the SOD1G93A mouse, CYP27B1 mRNA and protein were detected in skeletal muscle in early pre-symptomatic stages and increased through end-stage. In the human study, increases in CYP27B1 mRNA in muscle biopsies correlated with disease progression rates over the same time period. In summary, we show for the first time that CYP27B1 mRNA and protein expression are elevated in muscle fibers in denervating disease, especially ALS, where mRNA levels can potentially serve as a surrogate marker for tracking disease progression. Its upregulation may reflect a local perturbation of vitamin D signaling, and further characterization of this pathway may provide insight into underlying molecular processes linked to muscle denervation.