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  • Abstract: Vitamin D x
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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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Ranganathan R Rao Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK

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Harpal S Randeva Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK
Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK

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Sailesh Sankaranarayanan Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK
Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK

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Murthy Narashima Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK
Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK

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Matthias Möhlig Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK

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Hisham Mehanna Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK

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Martin O Weickert Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK
Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK

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Introduction/background

Vitamin D deficiency further increases circulating parathyroid hormone (PTH) levels in patients with primary hyperparathyroidism (pHPT), with potential detrimental effects on bone mass.

Methods

This was an observational clinical study in consecutive conservatively treated postmenopausal women (n=40) with pHPT and coexistent 25-hydroxyvitamin D deficiency (25OHD ≤50 nmol/l (≤20 ng/ml)). Patients who showed an increase in serum 25OHD above the threshold of vitamin D deficiency (>50 nmol/l; n=28) using treatment with various commonly prescribed vitamin D preparations were, for the purposes of statistical analyses, allocated to the treatment group. Patients who were retrospectively identified as having received no treatment with vitamin D and/or remained vitamin D deficient were considered as non-responders/controls (n=12). Adjusted calcium (adjCa), PTH and 25OHD concentrations were monitored in all subjects up to 54 months (mean observation period of 18±2 months).

Results

Prolonged increased vitamin D intake, regardless of the source (serum 25OHD, increase from 32.2±1.7 nmol/l at baseline to 136.4±11.6 nmol/l, P<0.0001), significantly reduced serum PTH (13.3±1.1 vs 10.5±1.0 pmol/l, P=0.0001), with no adverse effects on adjCa levels (2.60±0.03 vs 2.60±0.02 mmol/l, P=0.77) and renal function tests (P>0.73). In contrast, serum PTH remained unchanged (15.8±2.6 vs 16.3±1.9 pmol/l, P=0.64) in patients who remained vitamin D deficient, with a significant difference between groups in changes of PTH (P=0.0003). Intrapartial correlation analyses showed an independent negative correlation of changes in 25OHD with PTH levels (r ic=−0.41, P=0.014).

Conclusions

Prolonged treatment with vitamin D in various commonly prescribed preparations appeared to be safe and significantly reduced PTH levels by 21%.

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Sharon A Huish University Hospitals of Coventry and Warwickshire NHS Trust, Coventry, UK
The University of Warwick, Coventry, UK
Royal Devon and Exeter NHS Foundation Trust, Exeter, UK

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Carl Jenkinson The University of Birmingham, Birmingham, UK

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Janet A Dunn The University of Warwick, Coventry, UK

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David J Meredith Royal Devon and Exeter NHS Foundation Trust, Exeter, UK

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Rosemary Bland The University of Warwick, Coventry, UK

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Martin Hewison The University of Birmingham, Birmingham, UK

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Low serum 1,25-dihydroxyvitamin D (1,25(OH)2D) in end-stage renal disease (ESRD) is considered a consequence of elevated fibroblast growth factor 23 (FGF23) and concomitant reduced activity of renal 1α-hydroxylase (CYP27B1). Current ESRD treatment strategies to increase serum calcium and suppress secondary hyperparathyroidism involve supplementation with vitamin D analogues that circumvent 1α-hydroxylase. This overlooks the potential importance of 25-hydroxyvitamin D (25(OH)D) deficiency as a contributor to low serum 1,25(OH)2D. We investigated the effects of vitamin D (cholecalciferol) supplementation (40,000 IU for 12 weeks and maintenance dose of 20,000 IU fortnightly), on multiple serum vitamin D metabolites (25(OH)D, 1,25(OH)2D3 and 24,25(OH)2D3) in 55 haemodialysis patients. Baseline and 12 month data were compared using related-samples Wilcoxon signed rank test. All patients remained on active vitamin D analogues as part of routine ESRD care. 1,25(OH)2D3 levels were low at baseline (normal range: 60–120 pmol/L). Cholecalciferol supplementation normalised both serum 25(OH)D and 1,25(OH)2D3. Median serum 25(OH)D increased from 35.1 nmol/L (IQR: 23.0–47.5 nmol/L) to 119.9 nmol/L (IQR: 99.5–143.3 nmol/L) (P < 0.001). Median serum 1,25(OH)2D3 and 24,25(OH)2D3 increased from 48.3 pmol/L (IQR: 35.9–57.9 pmol/L) and 3.8 nmol/L (IQR: 2.3–6.0 nmol/L) to 96.2 pmol/L (IQR: 77.1–130.6 pmol/L) and 12.3 nmol/L (IQR: 9–16.4 nmol/L), respectively (P < 0.001). A non-significant reduction in daily active vitamin D analogue dose occurred, 0.94 µmcg at baseline to 0.77 µmcg at 12 months (P = 0.73). The ability to synthesise 1,25(OH)2D3 in ESRD is maintained but is substrate dependent, and serum 25(OH)D was a limiting factor at baseline. Therefore, 1,25(OH)2D3 deficiency in ESRD is partly a consequence of 25(OH)D deficiency, rather than solely due to reduced 1α-hydroxylase activity as suggested by current treatment strategies.

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Mirjam M Oosterwerff Departments of Internal Medicine, Epidemiology and Biostatistics, Public and Occupational Health, Endocrine Section

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Rosa Meijnen Departments of Internal Medicine, Epidemiology and Biostatistics, Public and Occupational Health, Endocrine Section

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Natasja M Van Schoor Departments of Internal Medicine, Epidemiology and Biostatistics, Public and Occupational Health, Endocrine Section

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Dirk L Knol Departments of Internal Medicine, Epidemiology and Biostatistics, Public and Occupational Health, Endocrine Section

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Mark H H Kramer Departments of Internal Medicine, Epidemiology and Biostatistics, Public and Occupational Health, Endocrine Section

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Mireille N M Van Poppel Departments of Internal Medicine, Epidemiology and Biostatistics, Public and Occupational Health, Endocrine Section

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Paul Lips Departments of Internal Medicine, Epidemiology and Biostatistics, Public and Occupational Health, Endocrine Section

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E Marelise W Eekhoff Departments of Internal Medicine, Epidemiology and Biostatistics, Public and Occupational Health, Endocrine Section

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Vitamin D deficiency is highly prevalent among non-western immigrants in The Netherlands and associated with poor physical performance. The aim of this study was to assess the effect of vitamin D supplementation on physical performance, exercise capacity, and daily physical activity in vitamin D-deficient, overweight non-western immigrants. A randomized double-blind, placebo-controlled trial was conducted to assess the effect of vitamin D on physical performance. A total of 130 participants were included. Eligibility criteria included overweight (BMI >27 kg/m2), 25-hydroxy vitamin D (25(OH)D) ≤50 nmol/l, and an age range of 20–65 years. The intervention group received 1200 IU vitamin D3 daily for 4 months; the control group received placebo. Both groups received 500 mg calcium daily. Outcome measures included physical performance (physical performance score), exercise capacity (a 6-min walk test (6-MWT)), and daily physical activity (questionnaire and accelerometer). There was no significant effect on physical performance, exercise capacity, or physical activity in the intention to treat analysis. In an explorative post hoc analysis restricted to participants reaching a serum 25(OH)D concentration of >60 nmol/l after intervention, there was an improvement of 19 m in the 6-MWT compared with the control group (P=0.053). Moderate dose vitamin D supplementation did not significantly improve physical performance, exercise capacity, or physical activity. However, when 25(OH)D concentrations reached >60 nmol/l after intervention, there was a borderline significant improvement in exercise capacity. Although the clinical relevance is not clear, this is a promising result, as all participants were overweight and did not improve their overall activity levels.

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Stan Ursem Department of Clinical Chemistry, Amsterdam Gastroenterology & Metabolism, Amsterdam UMC, Vrije Universiteit Amsterdam, Endocrine Laboratory, Amsterdam, Netherlands

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Vito Francic Division of Endocrinology and Diabetology, Department of Internal Medicine, Endocrinology Lab Platform, Medical University of Graz, Graz, Austria

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

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Verena Schwetz Division of Endocrinology and Diabetology, Department of Internal Medicine, Endocrinology Lab Platform, Medical University of Graz, Graz, Austria

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

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

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Felix Aberer Division of Endocrinology and Diabetology, Department of Internal Medicine, Endocrinology Lab Platform, Medical University of Graz, Graz, Austria

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Martin R Grübler Division of Endocrinology and Diabetology, Department of Internal Medicine, Endocrinology Lab Platform, Medical University of Graz, Graz, Austria

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Nicolas D Verheyen Division of Cardiology, Department of Internal Medicine, Medical University of Graz, Graz, Austria

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Winfried März Synlab Academy, Synlab Holding Germany GmbH, München, Germany

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Andreas Tomaschitz Specialist Clinic of Rehabilitation Bad Gleichenberg, Bad Gleichenberg, Austria

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

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Barbara Obermayer-Pietsch Division of Endocrinology and Diabetology, Department of Internal Medicine, Endocrinology Lab Platform, Medical University of Graz, Graz, Austria

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Annemieke C Heijboer Department of Clinical Chemistry, Amsterdam Gastroenterology & Metabolism, Amsterdam UMC, Vrije Universiteit Amsterdam, Endocrine Laboratory, Amsterdam, Netherlands
Department of Clinical Chemistry, Amsterdam Gastroenterology & Metabolism, Amsterdam UMC, University of Amsterdam, Endocrine Laboratory, Amsterdam, Netherlands

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Objective

PTH can be oxidised in vivo, rendering it biologically inactive. Non-oxidised PTH (n-oxPTH) may therefore give a better image of the hormonal status of the patient. While vitamin D supplementation decreases total PTH (tPTH) concentration, the effect on n-oxPTH concentration is unexplored. We investigated the effect of vitamin D on n-oxPTH concentration in comparison to tPTH and compared the correlations between parameters of calcium, bone and lipid metabolism with n-oxPTH and tPTH.

Methods

N-oxPTH was measured in 108 vitamin D-insufficient (25(OH)D <75 nmol/L) hypertensive patients, treated with vitamin D (2800 IE daily) or placebo for 8 weeks in the Styrian Vitamin D Hypertension Trial (NCT02136771). We calculated the treatment effect and performed correlation analyses of n-oxPTH and tPTH with parameters of calcium, bone and lipid metabolism and oxidative stress.

Results

After treatment, compared to placebo, 25(OH)D concentrations increased, tPTH decreased by 9% (P < 0.001), n-oxPTH by 7% (P = 0.025) and the ratio of n-oxPTH/tPTH increased (P = 0.027). Changes in phosphate and HDL concentration correlated with changes in n-oxPTH, but not tPTH.

Conclusions

tPTH and n-oxPTH decrease upon vitamin D supplementation. Our study suggests that vitamin D supplementation reduces the oxidation of PTH, as we observed a small but significant increase in the non-oxidised proportion of PTH upon treatment. In addition, we found that changes in phosphate and HDL concentration showed a relationship with changes in n-oxPTH, but not tPTH. This may be explained by the biological activity of n-oxPTH. Further research should be carried out to establish the clinical relevance of n-oxPTH.

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Haojie Zhang Institute and Department of Endocrinology and Metabolism, Shanghai Ninth People’s Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China

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Yuke Cui Institute and Department of Endocrinology and Metabolism, Shanghai Ninth People’s Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China

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Ruihua Dong Key Laboratory of Public Health Safety of Ministry of Education, Collaborative Innovation Center of Social Risks Governance in Health, School of Public Health, Fudan University, Shanghai, China

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Wen Zhang Institute and Department of Endocrinology and Metabolism, Shanghai Ninth People’s Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China

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Shihan Chen Institute and Department of Endocrinology and Metabolism, Shanghai Ninth People’s Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China

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Heng Wan Institute and Department of Endocrinology and Metabolism, Shanghai Ninth People’s Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China

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Chi Chen Institute and Department of Endocrinology and Metabolism, Shanghai Ninth People’s Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China

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Yi Chen Institute and Department of Endocrinology and Metabolism, Shanghai Ninth People’s Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China

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Yuying Wang Institute and Department of Endocrinology and Metabolism, Shanghai Ninth People’s Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China

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Chunfang Zhu Institute and Department of Endocrinology and Metabolism, Shanghai Ninth People’s Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China

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Bo Chen Key Laboratory of Public Health Safety of Ministry of Education, Collaborative Innovation Center of Social Risks Governance in Health, School of Public Health, Fudan University, Shanghai, China

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Ningjian Wang Institute and Department of Endocrinology and Metabolism, Shanghai Ninth People’s Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China

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Yingli Lu Institute and Department of Endocrinology and Metabolism, Shanghai Ninth People’s Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China

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Background

Bone is thought to be the reservoir of the human lead burden, and vitamin D is associated with bone turnover. We aimed to explore whether exposure to lower 25-hydroxy vitamin D (25(OH)D) levels was associated with higher blood lead levels (BLLs) by increasing the bone turnover rate in individuals with type 2 diabetes.

Methods

A total of 4103 type 2 diabetic men and postmenopausal women in Shanghai, China, were enrolled in 2018. Their 25(OH)D, β-C-terminal telopeptide (β-CTX), N-MID osteocalcin and procollagen type 1 N-peptide (P1NP) levels were detected. Their BLLs were determined by atomic absorption spectrometry. Mediation analyses were performed to identify the possible role that bone turnover played in the underlying mechanisms.

Results

In both the men and postmenopausal women, all three bone turnover markers were inversely associated with 25(OH)D and positively associated with the BLL (all P < 0.01) after adjusting for age, current smoking habits, metabolic parameters, duration of diabetes, vitamin D intake, and use of anti-osteoporosis medication. In the mediation analyses, none of the direct associations between 25(OH)D and BLL was significant for the three bone turnover markers, but all three bone turnover markers were found to be significant mediators of the indirect associations between 25(OH)D and BLL.

Conclusion

The association between vitamin D and BLL was fully mediated by bone turnover markers in type 2 diabetic patients (mediation effect). This finding suggested that vitamin D may protect against blood lead exposure from the bone reservoir by decreasing bone turnover in individuals with type 2 diabetes.

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Barbara J Boucher The Blizard Institute, Queen Mary University of London, London, UK

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High vitamin D deficiency rates, with rickets and osteomalacia, have been common in South Asians (SAs) arriving in Britain since the 1950s with preventable infant deaths from hypocalcaemic status-epilepticus and cardiomyopathy. Vitamin D deficiency increases common SA disorders (type 2 diabetes and cardiovascular disease), recent trials and non-linear Mendelian randomisation studies having shown deficiency to be causal for both disorders. Ethnic minority, obesity, diabetes and social deprivation are recognised COVID-19 risk factors, but vitamin D deficiency is not, despite convincing mechanistic evidence of it. Adjusting analyses for obesity/ethnicity abolishes vitamin D deficiency in COVID-19 risk prediction, but both factors lower serum 25(OH)D specifically. Social deprivation inadequately explains increased ethnic minority COVID-19 risks. SA vitamin D deficiency remains uncorrected after 70 years, official bodies using ‘education’, ‘assimilation’ and ‘diet’ as ‘proxies’ for ethnic differences and increasing pressures to assimilate. Meanwhile, English rickets was abolished from ~1940 by free ‘welfare foods’ (meat, milk, eggs, cod liver oil), for all pregnant/nursing mothers and young children (<5 years old). Cod liver oil was withdrawn from antenatal clinics in 1994 (for excessive vitamin A teratogenicity), without alternative provision. The take-up of the 2006 ‘Healthy-Start’ scheme of food-vouchers for low-income families with young children (<3 years old) has been poor, being inaccessible and poorly publicised. COVID-19 pandemic advice for UK adults in ‘lockdown’ was ‘400 IU vitamin D/day’, inadequate for correcting the deficiency seen winter/summer at 17.5%/5.9% in White, 38.5%/30% in Black and 57.2%/50.8% in SA people in representative UK Biobank subjects when recruited ~14 years ago and remaining similar in 2018. Vitamin D inadequacy worsens many non-skeletal health risks. Not providing vitamin D for preventing SA rickets and osteomalacia continues to be unacceptable, as deficiency-related health risks increase ethnic health disparities, while abolishing vitamin D deficiency would be easier and more cost-effective than correcting any other factor worsening ethnic minority health in Britain.

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Niek F Dirks Atalmedial Diagnostics Centre, Spaarne Gasthuis, Haarlem, The Netherlands
Department of Clinical Chemistry, Hematology and Immunology, Noordwest Ziekenhuis, Alkmaar, The Netherlands

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Etienne Cavalier Department of Clinical Chemistry, University of Liège, CHU de Liège, Liège, Belgium

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Annemieke C Heijboer Amsterdam UMC location Vrije Universiteit Amsterdam, Department of Clinical Chemistry, Endocrine Laboratory, Boelelaan, Amsterdam, The Netherlands
Amsterdam Gastroenterology, Endocrinology & Metabolism, Amsterdam, The Netherlands
Amsterdam UMC location University of Amsterdam, Department of Clinical Chemistry, Endocrine Laboratory, Amsterdam, The Netherlands
Amsterdam Reproduction & Development Research Institute, Amsterdam, The Netherlands

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The measurement of vitamin D metabolites aids in assessing vitamin D status and in diagnosing disorders of calcium homeostasis. Most laboratories measure total 25-hydroxyvitamin D (25(OH)D), while others have taken the extra effort to measure 25(OH)D2 and 25(OH)D3 separately and additional metabolites such as 1,25-dihydroxyvitamin D and 24,25-dihydroxyvitamin D. The aim of this review is to provide an updated overview of the main markers of vitamin D metabolism, define the intended measurands, and discuss the advantages and disadvantages of the two most widely used assays, automated assays and liquid chromatography–tandem mass spectrometry (LC-MS/MS). Whether using the easy and fast automated assays or the more complex LC-MS/MS, one should know the pitfalls of the used technique in order to interpret the measurements. In conclusion, automated assays are unable to accurately measure 25(OH)D in all patient groups, including persons using D2. In these cases, an LC-MS/MS method, when appropriately developed and standardized, produces a more reliable measurement.

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Mateo Amaya-Montoya School of Medicine, Universidad de los Andes, Bogotá, Colombia

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Daniela Duarte-Montero School of Medicine, Universidad de los Andes, Bogotá, Colombia

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Luz D Nieves-Barreto School of Medicine, Universidad de los Andes, Bogotá, Colombia

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Angélica Montaño-Rodríguez School of Medicine, Universidad de los Andes, Bogotá, Colombia

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Eddy C Betancourt-Villamizar Team Foods, Bogotá, Colombia

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María P Salazar-Ocampo School of Medicine, Universidad de los Andes, Bogotá, Colombia

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Carlos O Mendivil School of Medicine, Universidad de los Andes, Bogotá, Colombia
Fundación Santa Fe de Bogotá, Section of Endocrinology, Bogotá, Colombia

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Data on dietary calcium and vitamin D intake from Latin America are scarce. We explored the main correlates and dietary sources of calcium and vitamin D in a probabilistic, population-based sample from Colombia. We studied 1554 participants aged 18–75 from five different geographical regions. Dietary intake was assessed by employing a 157-item semi-quantitative food frequency questionnaire and national and international food composition tables. Daily vitamin D intake decreased with increasing age, from 230 IU/day in the 18–39 age group to 184 IU/day in the 60–75 age group (P -trend < 0.001). Vitamin D intake was positively associated with socioeconomic status (SES) (196 IU/day in lowest vs 234 in highest SES, P-trend < 0.001), and with educational level (176 IU/day in lowest vs 226 in highest education level, P-trend < 0.001). Daily calcium intake also decreased with age, from 1376 mg/day in the 18–39 age group to 1120 mg/day in the 60–75 age group (P -trend < 0.001). Calcium intake was lowest among participants with only elementary education, but the absolute difference in calcium intake between extreme education categories was smaller than for vitamin D (1107 vs 1274 mg/day, P-trend = 0.023). Daily calcium intake did not correlate with SES (P -trend = 0.74). Eggs were the main source of overall vitamin D, albeit their contribution decreased with increasing age. Dairy products contributed at least 48% of dietary calcium in all subgroups, mostly from cheese-containing traditional foods. SES and education were the key correlates of vitamin D and calcium intake. These findings may contribute to shape public health interventions in Latin American countries.

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Melissa Braga Department of Internal Medicine, Charles R. Drew University of Medicine and Science, Los Angeles, California, USA

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Zena Simmons Department of Health & Life Sciences, Charles R. Drew University of Medicine and Science, Los Angeles, California, USA

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Keith C Norris Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California, USA

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Monica G Ferrini Department of Internal Medicine, Charles R. Drew University of Medicine and Science, Los Angeles, California, USA
Department of Health & Life Sciences, Charles R. Drew University of Medicine and Science, Los Angeles, California, USA
Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California, USA

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Jorge N Artaza Department of Internal Medicine, Charles R. Drew University of Medicine and Science, Los Angeles, California, USA
Department of Health & Life Sciences, Charles R. Drew University of Medicine and Science, Los Angeles, California, USA
Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California, USA

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Skeletal muscle wasting is a serious disorder associated with health conditions such as aging, chronic kidney disease and AIDS. Vitamin D is most widely recognized for its regulation of calcium and phosphate homeostasis in relation to bone development and maintenance. Recently, vitamin D supplementation has been shown to improve muscle performance and reduce the risk of falls in vitamin D deficient older adults. However, little is known of the underlying molecular mechanism(s) or the role it plays in myogenic differentiation. We examined the effect of 1,25-D3 on myogenic cell differentiation in skeletal muscle derived stem cells. Primary cultures of skeletal muscle satellite cells were isolated from the tibialis anterior, soleus and gastrocnemius muscles of 8-week-old C57/BL6 male mice and then treated with 1,25-D3. The efficiency of satellite cells isolation determined by PAX7+ cells was 81%, and they expressed VDR. Incubation of satellite cells with 1,25-D3 induces increased expression of: (i) MYOD, (ii) MYOG, (iii) MYC2, (iv) skeletal muscle fast troponin I and T, (v) MYH1, (vi) IGF1 and 2, (vii) FGF1 and 2, (viii) BMP4, (ix) MMP9 and (x) FST. It also promotes myotube formation and decreases the expression of MSTN. In conclusion, 1,25-D3 promoted a robust myogenic effect on satellite cells responsible for the regeneration of muscle after injury or muscle waste. This study provides a mechanistic justification for vitamin D supplementation in conditions characterized by loss of muscle mass and also in vitamin D deficient older adults with reduced muscle mass and strength, and increased risk of falls.

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