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Stefan Pilz Division of Endocrinology and Diabetology, Department of Internal Medicine, Medical University of Graz, Graz, Austria

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Armin Zittermann Clinic for Thoracic and Cardiovascular Surgery, Herz- und Diabeteszentrum NRW, Ruhr University Bochum, Bad Oeynhausen, Germany

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Christian Trummer Division of Endocrinology and Diabetology, Department of Internal Medicine, Medical University of Graz, Graz, Austria

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Verena Theiler-Schwetz Division of Endocrinology and Diabetology, Department of Internal Medicine, Medical University of Graz, Graz, Austria

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Elisabeth Lerchbaum Division of Endocrinology and Diabetology, Department of Internal Medicine, Medical University of Graz, Graz, Austria

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Martin H Keppel University Institute for Medical and Chemical Laboratory Diagnostics, Paracelsus Medical University, Salzburg, Austria

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Martin R Grübler Department of Cardiology, Swiss Cardiovascular Center Bern, Bern University Hospital, University of Bern, Bern, Switzerland

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Winfried März Clinical Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Graz, Graz, Austria
Medical Clinic V (Nephrology, Hypertensiology, Rheumatology, Endocrinology, Diabetology), Medical Faculty Mannheim, Ruperto-Carola University of Heidelberg, Heidelberg, Germany
Synlab Medical Center of Human Genetics Mannheim, Mannheim, Germany

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Marlene Pandis Division of Endocrinology and Diabetology, Department of Internal Medicine, Medical University of Graz, Graz, Austria

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Vitamin D testing and treatment is a subject of controversial scientific discussions, and it is challenging to navigate through the expanding vitamin D literature with heterogeneous and partially opposed opinions and recommendations. In this narrative review, we aim to provide an update on vitamin D guidelines and the current evidence on the role of vitamin D for human health with its subsequent implications for patient care and public health issues. Vitamin D is critical for bone and mineral metabolism, and it is established that vitamin D deficiency can cause rickets and osteomalacia. While many guidelines recommend target serum 25-hydroxyvitamin D (25[OH]D) concentrations of ≥50 nmol/L (20 ng/mL), the minimum consensus in the scientific community is that serum 25(OH)D concentrations below 25–30 nmol/L (10–12 ng/mL) must be prevented and treated. Using this latter threshold of serum 25(OH)D concentrations, it has been documented that there is a high worldwide prevalence of vitamin D deficiency that may require public health actions such as vitamin D food fortification. On the other hand, there is also reason for concern that an exploding rate of vitamin D testing and supplementation increases costs and might potentially be harmful. In the scientific debate on vitamin D, we should consider that nutrient trials differ from drug trials and that apart from the opposed positions regarding indications for vitamin D treatment we still have to better characterize the precise role of vitamin D for human health.

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Marcela Moraes Mendes Department of Nutrition, Faculty of Health Sciences, University of Brasília, Distrito Federal, Brazil
Department of Nutrition, Institute of Life Sciences, Federal University of Juiz de Fora, Governador Valadares, Minas Gerais, Brazil
Department of Nutrition, Faculty of Health and Medical Sciences, University of Surrey, University of Surrey, Guildford, UK

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Patricia Borges Botelho Department of Nutrition, Faculty of Health Sciences, University of Brasília, Distrito Federal, Brazil

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Helena Ribeiro Department of Environmental Health, Faculty of Public Health, University of São Paulo, São Paulo, Brazil

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Vitamin D enhances calcium absorption and bone mineralisation, promotes maintenance of muscle function, and is crucial for musculoskeletal health. Low vitamin D status triggers secondary hyperparathyroidism, increases bone loss, and leads to muscle weakness. The primary physiologic function of vitamin D and its metabolites is maintaining calcium homeostasis for metabolic functioning, signal transduction, and neuromuscular activity. A considerable amount of human evidence supports the well-recognised contribution of adequate serum 25-hydroxyvitamin D concentrations for bone homeostasis maintenance and prevention and treatment strategies for osteoporosis when combined with adequate calcium intake. This paper aimed to review the literature published, mainly in the last 20 years, on the effect of vitamin D and its supplementation for musculoskeletal health in order to identify the aspects that remain unclear or controversial and therefore require further investigation and debate. There is a clear need for consistent data to establish realistic and meaningful recommendations of vitamin D status that consider different population groups and locations. Moreover, there is still a lack of consensus on thresholds for vitamin D deficiency and optimal status as well as toxicity, optimal intake of vitamin D, vitamin D supplement alone as a strategy to prevent fractures and falls, recommended sun exposure at different latitudes and for different skin pigmentations, and the extra skeletal effects of vitamin D.

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Glenville Jones Department of Biomedical and Molecular Sciences, Queen’s University, Kingston, Ontario, Canada

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Vitamin D has many physiological functions including upregulation of intestinal calcium and phosphate absorption, mobilization of bone resorption, renal reabsorption of calcium as well as actions on a variety of pleiotropic functions. It is believed that many of the hormonal effects of vitamin D involve a 1,25-dihydroxyvitamin D3-vitamin D receptor-mediated transcriptional mechanism involving binding to the cellular chromatin and regulating hundreds of genes in many tissues. This comprehensive historical review provides a unique perspective of the many steps of the discovery of vitamin D and its deficiency disease, rickets, stretching from 1650 until the present. The overview is divided into four distinct historical phases which cover the major developments in the field and in the process highlighting the: (a) first recognition of rickets or vitamin D deficiency; (b) discovery of the nutritional factor, vitamin D and its chemical structure; (c) elucidation of vitamin D metabolites including the hormonal form, 1,25-dihydroxyvitamin D3; (d) delineation of the vitamin D cellular machinery, functions and vitamin D-related diseases which focused on understanding the mechanism of action of vitamin D in its many target cells.

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Barbara J Boucher Blizard Institute, Barts & The London school of Medicine & Dentistry, Queen Mary University of London, London, UK

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Our knowledge of vitamin D has come a long way since the 100 years it took for doctors to accept, between 1860 and 1890, that both sunlight and cod liver oil (a well-known folk remedy) cured and prevented rickets. Vitamins D2/D3 were discovered exactly a hundred years ago, and over the last 50 years vitamin D has been found to have many effects on virtually all human tissues and not just on bone health, while mechanisms affecting the actions of vitamin D at the cellular level are increasingly understood, but deficiency persists globally. Observational studies in humans have shown that better provision of vitamin D is strongly associated, dose-wise, with reductions in current and future health risks in line with the known actions of vitamin D. Randomised controlled trials, commonly accepted as providing a ‘gold standard’ for assessing the efficacy of new forms of treatment, have frequently failed to provide supportive evidence for the expected health benefits of supplementation. Such RCTs, however, have used designs evolved for testing drugs while vitamin D is a nutrient; the appreciation of this difference is critical to identifying health benefits from existing RCT data and for improving future RCT design. This report aims, therefore, to provide a brief overview of the evidence for a range of non-bony health benefits of vitamin D repletion; to discuss specific aspects of vitamin D biology that can confound RCT design and how to allow for them.

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Shu-Meng Hu Department of Nephrology, West China Hospital, Sichuan University, Chengdu, Sichuan, China

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Yang-Juan Bai Department of Laboratory Medicine/Research Centre of Clinical Laboratory Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan, China

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Ya-Mei Li Department of Laboratory Medicine/Research Centre of Clinical Laboratory Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan, China

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Ye Tao Department of Nephrology, West China Hospital, Sichuan University, Chengdu, Sichuan, China

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Xian-Ding Wang Department of Urology/Institute of Urology, West China Hospital, Sichuan University, Chengdu, Sichuan, China

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Tao Lin Department of Urology/Institute of Urology, West China Hospital, Sichuan University, Chengdu, Sichuan, China

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Lan-Lan Wang Department of Laboratory Medicine/Research Centre of Clinical Laboratory Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan, China

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Yun-Ying Shi Department of Nephrology, West China Hospital, Sichuan University, Chengdu, Sichuan, China

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Introduction

Tertiary hyperparathyroidism (THPT) and vitamin D deficiency are commonly seen in kidney transplant recipients, which may result in persistently elevated fibroblast growth factor 23 (FGF23) level after transplantation and decreased graft survival. The aim of this study is to evaluate the effect of vitamin D supplementation on THPT, FGF23-alpha Klotho (KLA) axis and cardiovascular complications after transplantation.

Materials and methods

Two hundred nine kidney transplant recipients were included and further divided into treated and untreated groups depending on whether they received vitamin D supplementation. We tracked the state of THPT, bone metabolism and FGF23–KLA axis within 12 months posttransplant and explored the predictors and risk factors for intact FGF23 levels, KLA levels, THPT and cardiovascular complications in recipients.

Results

Vitamin D supplementation significantly improved FGF23 resistance, THPT and high bone turnover status, preserved better graft function and prevented coronary calcification in the treated group compared to the untreated group at month 12. The absence of vitamin D supplementation was an independent risk factor for THPT and a predictor for intact FGF23 and KLA levels at month 12. Age and vitamin D deficiency were independent risk factors for coronary calcification in recipients at month 12.

Conclusion

Vitamin D supplementation effectively improved THPT, FGF23 resistance and bone metabolism, preserved graft function and prevented coronary calcification after transplantation.

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Mohammed S Razzaque Department of Pathology, Lake Erie College of Osteopathic Medicine, Erie, Pennsylvania, USA

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Fibroblast growth factor‐23 (FGF23) controls the homeostasis of both phosphate and vitamin D. Bone-derived FGF23 can suppress the transcription of 1α‐hydroxylase (1α(OH)ase) to reduce renal activation of vitamin D (1,25(OH)2D3). FGF23 can also activate the transcription of 24‐hydroxylase to enhance the renal degradation process of vitamin D. There is a counter-regulation for FGF23 and vitamin D; 1,25(OH)2D3 induces the skeletal synthesis and the release of FGF23, while FGF23 can suppress the production of 1,25(OH)2D3 by inhibiting 1α(OH)ase synthesis. Genetically ablating FGF23 activities in mice resulted in higher levels of renal 1α(OH)ase, which is also reflected in an increased level of serum 1,25(OH)2D3, while genetically ablating 1α(OH)ase activities in mice reduced the serum levels of FGF23. Similar feedback control of FGF23 and vitamin D is also detected in various human diseases. Further studies are required to understand the subcellular molecular regulation of FGF23 and vitamin D in health and disease.

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Gabriella Oliveira Lima Laboratory of Pharmacology and Toxicology of Natural Products, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Alex Luiz Menezes da Silva Laboratory of Pharmacology and Toxicology of Natural Products, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Julianne Elba Cunha Azevedo Laboratory of Pharmacology and Toxicology of Natural Products, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Chirlene Pinheiro Nascimento Laboratory of Pharmacology and Toxicology of Natural Products, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Luana Rodrigues Vieira Laboratory of Pharmacology and Toxicology of Natural Products, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Akira Otake Hamoy Laboratory of Pharmacology and Toxicology of Natural Products, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Luan Oliveira Ferreira Laboratory of Experimental Neuropathology, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Verônica Regina Lobato Oliveira Bahia Multidisciplinary Laboratory of Animal Morphology, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Nilton Akio Muto Amazon Bioactive Compounds Valorization Center, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Dielly Catrina Favacho Lopes Laboratory of Experimental Neuropathology, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Moisés Hamoy Laboratory of Pharmacology and Toxicology of Natural Products, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Low plasma levels of vitamin D causes bone mineral change that can precipitate osteopenia and osteoporosis and could aggravate autoimmune diseases, hypertension and diabetes. The demand for vitamin D supplementation becomes necessary; however, the consumption of vitamin D is not without risks, which its toxicity could have potentially serious consequences related to hypervitaminosis D, such as hypercalcemia and cerebral alterations. Thus, the present study describes the electroencephalographic changes caused by supraphysiological doses of vitamin D in the brain electrical dynamics and the electrocardiographic changes. After 4 days of treatment with vitamin D at a dose of 25,000 IU/kg, the serum calcium levels found were increased in comparison with the control group. The electrocorticogram analysis found a reduction in wave activity in the delta, theta, alpha and beta frequency bands. For ECG was observed changes with shortened QT follow-up, which could be related to serum calcium concentration. This study presented important evidence about the cerebral and cardiac alterations caused by high doses of vitamin D, indicating valuable parameters in the screening and decision-making process for diagnosing patients with symptoms suggestive of intoxication.

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Shatha Alharazy Department of Physiology, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia

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M Denise Robertson Department of Nutritional Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK

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Susan Lanham-New Department of Nutritional Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK

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Muhammad Imran Naseer Centre of Excellence in Genomic Medicine Research, King Abdulaziz University, Jeddah, Saudi Arabia
Department of Medical Laboratory Technology, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah, Saudi Arabia

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Adeel G Chaudhary Centre of Excellence in Genomic Medicine Research, King Abdulaziz University, Jeddah, Saudi Arabia
Department of Medical Laboratory Technology, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah, Saudi Arabia
Centre for Innovation in Personalized Medicine, King Abdulaziz University, Jeddah, Saudi Arabia

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Eman Alissa Department of Clinical Biochemistry, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia

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Background

Measurement of free 25-hydroyvitamin D (25(OH)D) status has been suggested as a more representative marker of vitamin D status than that of total 25(OH)D. Previously, free 25(OH)D could only be calculated indirectly; however, a newly developed direct assay for the measurement of free 25(OH)D is now available. The aim of this study therefore was to investigate directly measured total and free vitamin D levels association with metabolic health in postmenopausal healthy women living in Saudi Arabia.

Methods

A sample of 302 postmenopausal women aged ≥50 years (n  = 302) living in Saudi Arabia were recruited in a cross-sectional study design. Blood samples were collected from subjects for measurement of serum levels of total 25(OH)D, directly measured free 25(OH)D, metabolic bone parameters, lipid profile, and other biochemical tests.

Results

A positive correlation was found between directly measured free and total 25(OH)D (r = 0.64, P< 0.0001). Total but not free 25(OH)D showed significant association with serum intact parathyroid hormone (P = 0.004), whilst free 25(OH)D but not total 25(OH)D showed a significant association with total cholesterol and LDL-C (P = 0.032 and P = 0.045, respectively).

Conclusions

Free 25(OH)D and total 25(OH)D were found to be consistently correlated but with different associations to metabolic health parameters. Further research is needed to determine which marker of vitamin D status would be the most appropriate in population studies.

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Natércia Neves Marques de Queiroz University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Franciane Trindade Cunha de Melo University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Fabrício de Souza Resende University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Luísa Corrêa Janaú University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Norberto Jorge Kzan de Souza Neto University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Manuela Nascimento de Lemos University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Ana Carolina Lobato Virgolino University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Maria Clara Neres Iunes de Oliveira University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Angélica Leite de Alcântara University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Lorena Vilhena de Moraes University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Tiago Franco David University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Wanderson Maia da Silva University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Scarlatt Souza Reis University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Márcia Costa dos Santos University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Ana Carolina Contente Braga de Souza University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Pedro Paulo Freire Piani University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Neyla Arroyo Lara Mourão University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Karem Mileo Felício University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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João Felício Abrahão Neto University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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João Soares Felício University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Objective:

Investigate the prevalence of vitamin D deficiency in an equatorial population through a large-sample study.

Methods:

Cross-sectional study with 30,224 healthy individuals from the North Region, in Brazil (Amazônia – state of Pará), who had 25-hydroxy-vitamin D (25(OH)D) and intact parathyroid hormone (PTH) serum levels measured by immunoassay method. Those with history of acute or chronic diseases were excluded. Abnormal levels of calcium, creatinine, glycemia and albumin were also exclusion criteria.

Results:

25(OH)D levels were 29.1 ± 8.2 ng/mL and values <12.7 ng/mL were equal to < −2 s.d. below average. Hypovitaminosis D was present in 10% of subjects according to the Institute of Medicine (values <20 ng/mL) and in 59%, in consonance with Endocrine Society (values 20–30 ng/mL as insufficiency and <20 ng/mL as deficiency) criteria. Individuals were divided according to four age brackets: children, adolescents, adults and elderly, and their 25(OH)D levels were: 33 ± 9; 28.5 ± 7.4; 28.3 ± 7.7; 29.3 ± 8.5 ng/mL, respectively. All groups differed in 25(OH)D, except adolescents vs adults. Regression model showed BMI, sex, living zone (urban or rural) and age as independent variables to 25(OH)D levels. Comparing subjects with vitamin D deficiency (<20 ng/mL) to those with vitamin D insufficiency (20–30 ng/mL), a difference between PTH levels in these two groups was observed (95.9 ± 24.7 pg/mL vs 44.2 ± 64.5 pg/mL; P < 0.01). Additionally, the most accurate predictive vitamin D level for subclinical hyperparathyroidism in ROC curve was 26 ng/mL.

Conclusion:

Our equatorial population showed low prevalence of vitamin D hypovitaminosis ranging with age bracket. The insufficient category by Endocrine Society was corroborated by our PTH data.

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Jane Fletcher Nutrition Nurses, University Hospitals Birmingham NHS Trust, Queen Elizabeth Hospital Birmingham, Mindelsohn Way, Edgbaston, Birmingham, UK
School of Nursing, Institute of Clinical Sciences, University of Birmingham, Edgbaston, Birmingham, UK

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Emma L Bishop Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, UK

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Stephanie R Harrison Leeds Institute of Rheumatic and Musculoskeletal Medicine, Chapel Allerton Hospital, Leeds, UK

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Amelia Swift School of Nursing, Institute of Clinical Sciences, University of Birmingham, Edgbaston, Birmingham, UK

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Sheldon C Cooper Gastroenterology Department, University Hospitals Birmingham NHS Trust, Queen Elizabeth Hospital Birmingham, Mindelsohn Way, Edgbaston, Birmingham, UK

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Sarah K Dimeloe Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, UK

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Karim Raza Institute of Inflammation and Ageing, University of Birmingham, Birmingham, UK

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Martin Hewison Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, UK

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Vitamin D has well-documented effects on calcium homeostasis and bone metabolism but recent studies suggest a much broader role for this secosteroid in human health. Key components of the vitamin D system, notably the vitamin D receptor (VDR) and the vitamin D-activating enzyme (1α-hydroxylase), are present in a wide array of tissues, notably macrophages, dendritic cells and T lymphocytes (T cells) from the immune system. Thus, serum 25-hydroxyvitamin D (25D) can be converted to hormonal 1,25-dihydroxyvitamin D (1,25D) within immune cells, and then interact with VDR and promote transcriptional and epigenomic responses in the same or neighbouring cells. These intracrine and paracrine effects of 1,25D have been shown to drive antibacterial or antiviral innate responses, as well as to attenuate inflammatory T cell adaptive immunity. Beyond these mechanistic observations, association studies have reported the correlation between low serum 25D levels and the risk and severity of human immune disorders including autoimmune diseases such as inflammatory bowel disease, multiple sclerosis, type 1 diabetes and rheumatoid arthritis. The proposed explanation for this is that decreased availability of 25D compromises immune cell synthesis of 1,25D leading to impaired innate immunity and over-exuberant inflammatory adaptive immunity. The aim of the current review is to explore the mechanistic basis for immunomodulatory effects of 25D and 1,25D in greater detail with specific emphasis on how vitamin D-deficiency (low serum levels of 25D) may lead to dysregulation of macrophage, dendritic cell and T cell function and increase the risk of inflammatory autoimmune disease.

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