scholarly journals The Effect of Vitamin D Supplementation on its Metabolism and the Vitamin D Metabolite Ratio

Nutrients ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2539 ◽  
Author(s):  
Vito Francic ◽  
Stan R. Ursem ◽  
Niek F. Dirks ◽  
Martin H. Keppel ◽  
Verena Theiler-Schwetz ◽  
...  
Keyword(s):  
Vitamin D ◽  
Vitamin D Supplementation ◽  
Vitamin D Metabolites ◽  
Vitamin D Status ◽  
Hydroxyvitamin D ◽  
Dihydroxyvitamin D ◽  
Correlation And Regression Analysis ◽  
Metabolite Ratio ◽  
25 Hydroxyvitamin D ◽  
Additional Value

25-hydroxyvitamin D (25(OH)D) is commonly measured to assess vitamin D status. Other vitamin D metabolites such as 24,25-dihydroxyvitamin D (24,25(OH)2D) provide additional insights into vitamin D status or metabolism. Earlier studies suggested that the vitamin D metabolite ratio (VMR), calculated as 24,25(OH)2D/25(OH)D, could predict the 25(OH)D increase after vitamin D supplementation. However, the evidence for this additional value is inconclusive. Therefore, our aim was to assess whether the increase in 25(OH)D after supplementation was predicted by the VMR better than baseline 25(OH)D. Plasma samples of 106 individuals (25(OH)D < 75 nmol/L) with hypertension who completed the Styrian Vitamin D Hypertension Trial (NC.T.02136771) were analyzed. Participants received vitamin D (2800 IU daily) or placebo for 8 weeks. The treatment effect (ANCOVA) for 25(OH)D3, 24,25(OH)2D3 and the VMR was 32 nmol/L, 3.3 nmol/L and 0.015 (all p < 0.001), respectively. Baseline 25(OH)D3 and 24,25(OH)2D3 predicted the change in 25(OH)D3 with comparable strength and magnitude. Correlation and regression analysis showed that the VMR did not predict the change in 25(OH)D3. Therefore, our data do not support routine measurement of 24,25(OH)2D3 in order to individually optimize the dosage of vitamin D supplementation. Our data also suggest that activity of 24-hydroxylase increases after vitamin D supplementation.

Calcium-Regulating Hormones and Minerals From Birth to 18 Months of Age: A Cross-Sectional Study. I. Effects of Sex, Race, Age, Season, and Diet on Vitamin D Status

PEDIATRICS ◽  
1986 ◽  
Vol 77 (6) ◽  
pp. 883-890
Author(s):  
P. Lichtenstein ◽  
B. L. Specker ◽  
R. C. Tsang ◽  
F. Mimouni ◽  
C. Gormley
Keyword(s):  
Vitamin D ◽  
Human Milk ◽  
Binding Protein ◽  
Vitamin D Metabolites ◽  
Vitamin D Status ◽  
Vitamin D Binding Protein ◽  
Hydroxyvitamin D ◽  
Dihydroxyvitamin D ◽  
1,25 Dihydroxyvitamin D ◽  
25 Hydroxyvitamin D

The influence of sex, race, age, season, and diet (cow's milk formula v human milk) on the vitamin D and vitamin D-binding protein status in infants less than 18 months of age was investigated in this crosssectional, prospective study of 198 infants. No differences by sex were observed in serum 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, 24,25-dihydroxyvitamin D, or vitamin D-binding protein concentrations. By race, black infants had significantly elevated serum 1,25-dihydroxyvitamin D levels relative to white infants. By age, vitamin D-binding protein concentrations increased with increasing age. By season, serum 25-hydroxyvitamin D concentrations were low in winter, whereas 1,25-dihydroxyvitamin D and vitamin D-binding protein were high in winter compared with summer. By diet, formula-fed infants had higher serum concentrations of all measured vitamin D metabolites and vitamin D-binding protein than human milk-fed infants. Thus, race, age, season, and diet exert, individually or in combination, different and significant effects on vitamin D metabolites; these should be considered in assessing infant vitamin D status.

scholarly journals Vitamin D-Mediated Hypercalcemia: Mechanisms, Diagnosis, and Treatment

2016 ◽  
Vol 37 (5) ◽  
pp. 521-547 ◽  
Author(s):  
Peter J. Tebben ◽  
Ravinder J. Singh ◽  
Rajiv Kumar
Keyword(s):  
Vitamin D ◽  
Vitamin D Receptor ◽  
Active Form ◽  
Elevated Serum ◽  
Diagnosis And Treatment ◽  
Vitamin D Metabolites ◽  
Hydroxyvitamin D ◽  
Dihydroxyvitamin D ◽  
Stone Formers ◽  
25 Hydroxyvitamin D

AbstractHypercalcemia occurs in up to 4% of the population in association with malignancy, primary hyperparathyroidism, ingestion of excessive calcium and/or vitamin D, ectopic production of 1,25-dihydroxyvitamin D [1,25(OH)2D], and impaired degradation of 1,25(OH)2D. The ingestion of excessive amounts of vitamin D3 (or vitamin D2) results in hypercalcemia and hypercalciuria due to the formation of supraphysiological amounts of 25-hydroxyvitamin D [25(OH)D] that bind to the vitamin D receptor, albeit with lower affinity than the active form of the vitamin, 1,25(OH)2D, and the formation of 5,6-trans 25(OH)D, which binds to the vitamin D receptor more tightly than 25(OH)D. In patients with granulomatous disease such as sarcoidosis or tuberculosis and tumors such as lymphomas, hypercalcemia occurs as a result of the activity of ectopic 25(OH)D-1-hydroxylase (CYP27B1) expressed in macrophages or tumor cells and the formation of excessive amounts of 1,25(OH)2D. Recent work has identified a novel cause of non-PTH-mediated hypercalcemia that occurs when the degradation of 1,25(OH)2D is impaired as a result of mutations of the 1,25(OH)2D-24-hydroxylase cytochrome P450 (CYP24A1). Patients with biallelic and, in some instances, monoallelic mutations of the CYP24A1 gene have elevated serum calcium concentrations associated with elevated serum 1,25(OH)2D, suppressed PTH concentrations, hypercalciuria, nephrocalcinosis, nephrolithiasis, and on occasion, reduced bone density. Of interest, first-time calcium renal stone formers have elevated 1,25(OH)2D and evidence of impaired 24-hydroxylase-mediated 1,25(OH)2D degradation. We will describe the biochemical processes associated with the synthesis and degradation of various vitamin D metabolites, the clinical features of the vitamin D-mediated hypercalcemia, their biochemical diagnosis, and treatment.

Vitamin D status in infancy and cardiometabolic health in adolescence

2020 ◽  
Vol 113 (1) ◽  
pp. 104-112
Author(s):  
Joshua Garfein ◽  
Kerry S Flannagan ◽  
Sheila Gahagan ◽  
Raquel Burrows ◽  
Betsy Lozoff ◽  
...  
Keyword(s):  
Vitamin D ◽  
Body Fat ◽  
Early Life ◽  
Vitamin D Supplementation ◽  
Lower Percentage ◽  
Cardiometabolic Health ◽  
Vitamin D Status ◽  
Percentage Body Fat ◽  
Hydroxyvitamin D ◽  
25 Hydroxyvitamin D

ABSTRACT Background Vitamin D deficiency is associated with obesity-related conditions, but the role of early life vitamin D status on the development of obesity is poorly understood. Objectives We assessed whether serum 25-hydroxyvitamin D [25(OH)D] at age 1 y was related to metabolic health through adolescence. Methods We quantified serum 25(OH)D in samples obtained at age 1 y from 306 participants in a cohort study in Santiago, Chile. Anthropometry was performed at ages 5, 10, and 16/17 y. At 16/17 y, we determined body composition using DXA and quantified metabolic parameters in a blood sample. We examined the associations of infancy 25(OH)D with BMI-for-age z-score (BMIZ) at ages 5, 10, and 16/17 y; with percentage fat and percentage lean body mass at age 16/17 y; and with a metabolic syndrome (MetS) score and its components at age 16/17 y. Results Infancy 25(OH)D was inversely associated with BMIZ in childhood. Every 25-nmol/L difference in 25(OH)D was related to an adjusted 0.11 units lower BMIZ at age 5 y (95% CI: −0.20, −0.03; P = 0.01) and a 0.09 unit lower BMIZ change from ages 1 to 5 y (95% CI: −0.17, −0.01; P = 0.02). Also, every 25-nmol/L 25(OH)D in infancy was associated with an adjusted 1.3 points lower percentage body fat mass (95% CI: −2.2, −0.4; P = 0.005) and an adjusted 0.03 units lower MetS score (95% CI: −0.05, −0.01; P = 0.01) at age 16/17 y, through inverse associations with waist circumference and the HOMA-IR. Conclusions Serum 25(OH)D at age 1 y is inversely associated with childhood BMIZ, percentage body fat at age 16/17 y, and a MetS score at age 16/17 y. Intervention studies are warranted to examine the effects of vitamin D supplementation in early life on long-term cardiometabolic outcomes.

scholarly journals Skeletal and Extraskeletal Actions of Vitamin D: Current Evidence and Outstanding Questions

2018 ◽  
Vol 40 (4) ◽  
pp. 1109-1151 ◽  
Author(s):  
Roger Bouillon ◽  
Claudio Marcocci ◽  
Geert Carmeliet ◽  
Daniel Bikle ◽  
John H White ◽  
...  
Keyword(s):  
Vitamin D ◽  
Vitamin D Deficiency ◽  
Human Subjects ◽  
Osteoporotic Fractures ◽  
Vitamin D Supplementation ◽  
Current Evidence ◽  
Elderly Subjects ◽  
Vitamin D Status ◽  
Hydroxyvitamin D ◽  
25 Hydroxyvitamin D

AbstractThe etiology of endemic rickets was discovered a century ago. Vitamin D is the precursor of 25-hydroxyvitamin D and other metabolites, including 1,25(OH)2D, the ligand for the vitamin D receptor (VDR). The effects of the vitamin D endocrine system on bone and its growth plate are primarily indirect and mediated by its effect on intestinal calcium transport and serum calcium and phosphate homeostasis. Rickets and osteomalacia can be prevented by daily supplements of 400 IU of vitamin D. Vitamin D deficiency (serum 25-hydroxyvitamin D <50 nmol/L) accelerates bone turnover, bone loss, and osteoporotic fractures. These risks can be reduced by 800 IU of vitamin D together with an appropriate calcium intake, given to institutionalized or vitamin D–deficient elderly subjects. VDR and vitamin D metabolic enzymes are widely expressed. Numerous genetic, molecular, cellular, and animal studies strongly suggest that vitamin D signaling has many extraskeletal effects. These include regulation of cell proliferation, immune and muscle function, skin differentiation, and reproduction, as well as vascular and metabolic properties. From observational studies in human subjects, poor vitamin D status is associated with nearly all diseases predicted by these extraskeletal actions. Results of randomized controlled trials and Mendelian randomization studies are supportive of vitamin D supplementation in reducing the incidence of some diseases, but, globally, conclusions are mixed. These findings point to a need for continued ongoing and future basic and clinical studies to better define whether vitamin D status can be optimized to improve many aspects of human health. Vitamin D deficiency enhances the risk of osteoporotic fractures and is associated with many diseases. We review what is established and what is plausible regarding the health effects of vitamin D.

scholarly journals Vitamin D Metabolism and Profiling in Veterinary Species

Metabolites ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 371 ◽  
Author(s):  
Emma A. Hurst ◽  
Natalie Z. Homer ◽  
Richard J. Mellanby
Keyword(s):  
Vitamin D ◽  
Companion Animals ◽  
Vitamin D Metabolites ◽  
Vitamin D Status ◽  
Vitamin D Metabolism ◽  
Hydroxyvitamin D ◽  
Chromatography Tandem Mass Spectrometry ◽  
Liquid Chromatography Tandem Mass ◽  
Health And Disease ◽  
25 Hydroxyvitamin D

The demand for vitamin D analysis in veterinary species is increasing with the growing knowledge of the extra-skeletal role vitamin D plays in health and disease. The circulating 25-hydroxyvitamin-D (25(OH)D) metabolite is used to assess vitamin D status, and the benefits of analysing other metabolites in the complex vitamin D pathway are being discovered in humans. Profiling of the vitamin D pathway by liquid chromatography tandem mass spectrometry (LC-MS/MS) facilitates simultaneous analysis of multiple metabolites in a single sample and over wide dynamic ranges, and this method is now considered the gold-standard for quantifying vitamin D metabolites. However, very few studies report using LC-MS/MS for the analysis of vitamin D metabolites in veterinary species. Given the complexity of the vitamin D pathway and the similarities in the roles of vitamin D in health and disease between humans and companion animals, there is a clear need to establish a comprehensive, reliable method for veterinary analysis that is comparable to that used in human clinical practice. In this review, we highlight the differences in vitamin D metabolism between veterinary species and the benefits of measuring vitamin D metabolites beyond 25(OH)D. Finally, we discuss the analytical challenges in profiling vitamin D in veterinary species with a focus on LC-MS/MS methods.

scholarly journals Oral vitamin D supplementation has a lower bioavailability and reduces hypersecretion of parathyroid hormone and insulin resistance in obese Chinese males

2014 ◽  
Vol 18 (12) ◽  
pp. 2211-2219 ◽  
Author(s):  
Ji-Chang Zhou ◽  
Yu-Mei Zhu ◽  
Zheng Chen ◽  
Jun-Luan Mo ◽  
Feng-Zhu Xie ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Vitamin D ◽  
Parathyroid Hormone ◽  
Vitamin D Supplementation ◽  
Normal Weight ◽  
Vitamin D Status ◽  
Intervention Trial ◽  
Oral Vitamin ◽  
Hydroxyvitamin D ◽  
25 Hydroxyvitamin D

AbstractObjectiveTo examine the vitamin D status, SNP of the vitamin D receptor gene (VDR) and the effects of vitamin D supplementation on parathyroid hormone and insulin secretion in adult males with obesity or normal weight in a subtropical Chinese city.DesignAn intervention trial.SettingShenzhen City, Guangdong Province, China.SubjectsFrom a cross-sectional survey conducted from June to July, eighty-two normal-weight and ninety-nine obese males (18–69 years) were screened to analyse their vitamin D status and for five SNP of VDR. From these individuals, in the same season of a different year, obese and normal-weight male volunteers (twenty-one per group) were included for an intervention trial with oral vitamin D supplementation at 1250 µg/week for 8 weeks.ResultsFor the survey, there was no significant difference (P>0·05) in baseline circulating 25-hydroxyvitamin D concentrations or in the percentages of participants in different categories of vitamin D status between the two groups. The VDR SNP, rs3782905, was significantly associated with obesity (P=0·043), but none of the examined SNP were correlated with serum 25-hydroxyvitamin D when adjusted for age, BMI and study group. After vitamin D supplementation, serum 25-hydroxyvitamin D concentration, hypersecretions of parathyroid hormone and insulin, and insulin resistance in the obese were changed beneficially (P<0·05); however, the increase in serum 25-hydroxyvitamin D was less than that of the normal-weight men.ConclusionsFor obese and normal-weight men of subtropical China, the summer baseline vitamin D status was similar. However, oral vitamin D supplementation revealed a decreased bioavailability of vitamin D in obese men and ameliorated their hypersecretion of parathyroid hormone and insulin resistance.

scholarly journals MON-386 Determining Vitamin D Status: Analytical Variability Between Available Assays

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Azni Lihawa Abdul Wahab ◽  
Hans Gerhard Schneider
Keyword(s):  
Vitamin D ◽  
Cross Reactivity ◽  
Vitamin D Metabolites ◽  
Vitamin D Status ◽  
Serum Samples ◽  
Hydroxyvitamin D ◽  
Low Concentrations ◽  
Strong Positive Relationship ◽  
Liquid Chromatography Tandem Mass ◽  
25 Hydroxyvitamin D

Abstract Clinical interest to evaluate serum 25-hydroxyvitamin D[25(OH)D] to assess Vitamin D status in health risks continue to increase exponentially over the last decade. Variability of 25(OH)D measurements remains controversial despite the international initiative Vitamin D Standardization Program (VDSP) to standardise the assays. The aim of the present study was to examine the correlation of 25(OH)D concentrations measured by different assays. We measured 25(OH)D using the new Abbott Alinity and DiaSorin LiaisonXL chemiluminescence immunoassays against the National Institute of Standards and Technology (NIST)-traceable liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. The immunoassay method were compared with the LC-MS/MS using Passing-Bablok regression and Bland-Altman analysis. Common 25(OH)D cut-point for classification of vitamin D deficiency was used to compare the different assays. 125 adult serum samples were randomly selected and measured 25(OH)D levels ranged between &lt;10 nmol/L to 290 nmol/L as determined by LC-MS/MS. Compared to the LC-MS/MS, both immunoassays demonstrated strong positive relationship based on Passing-Bablok regression analysis. The results were as follows: Abbott Alinity = 0.85x + 1.29nmol/L, 95% CI: -2.39 to 5.03 (r=0.94); DiaSorin LiaisonXL= 0.74x + 2.54nmol/L, 95% CI: -2.53 to 6.18 (r=0.91). Despite apparent good correlation, the overall mean bias was -12.6% for Abbott Alinity and -24.4% for DiaSorin LiaisonXL assays. A higher percentage of patients were classified as vitamin D deficient (25(OH)D &lt;50 nmol/L) using DiaSorin LiaisonXL (53%) followed by Abbott Alinity (49%), when compared with LC-MS/MS (34%). Using 25(OH)D ≥ 50nmol/L as “adequate” determined by LC-MS/MS method, 22% (18/82) and 28% (23/82) of patients were classified as “deficient” when analysed on Abbott Alinity and DiaSorin LiaisonXL respectively. Clinician should be aware of the inter-method variability among different Vitamin D assays despite standardization efforts. These differences could be due to cross-reactivity with 25(OH)D2 and vitamin D metabolites, such as 24,25(OH)2D and epimeric forms. 3-epi-25(OH)D is not separated chromatographically by the LC-MS/MS method used in this study. Therefore, the negative bias observed might be due to interference from the 3-epi-25(OH)D, whereby clinical significance is uncertain. It is present in low concentrations in adult human serum, 1 but seen in significant amounts in neonatal serum.2 It is advisable to monitor serum 25(OH)D level following treatment in the same laboratory. 1. Lensmeyer G, et al. The C-3 epimer of 25-hydroxyvitamin D3 is present in adult serum. JCEM 2012; 97: 163–8. 2. Singh RJ, et al. C-3 epimers can account for a significant portion of total circulating 25-hydroxyvitamin D in infants, complicating accurate measurement and interpretation of vitamin D status. JCEM 2006; 91: 3055-61.

Simultaneous determination of 25-hydroxyvitamin D, 24,25-dihydroxyvitamin D, and 1,25-dihydroxyvitamin D in plasma or serum.

1981 ◽  
Vol 27 (10) ◽  
pp. 1757-1760 ◽  
Author(s):  
M J Jongen ◽  
W J van der Vijgh ◽  
H J Willems ◽  
J C Netelenbos ◽  
P Lips
Keyword(s):  
Vitamin D ◽  
Vitamin D Metabolites ◽  
Binding Assays ◽  
Hydroxyvitamin D ◽  
Dihydroxyvitamin D ◽  
1,25 Dihydroxyvitamin D ◽  
Extraction And Purification ◽  
Chromatographic Procedure ◽  
25 Hydroxyvitamin D ◽  
Liquid Chromatographic

Abstract We describe a simultaneous assay for the principal vitamin D metabolites: 25-hydroxyvitamin D, 24-25-dihydroxyvitamin D, and 1,25-dihydroxyvitamin D. Special attention has been paid to simplification of the extensive extraction and purification procedures used in previously described simultaneous assays. All three metabolites were isolated with a single extraction step, followed by only one gradient liquid-chromatographic procedure. For final quantitation we used competitive protein binding assays, involving readily available binding proteins and commercially purchased tritiated vitamin D metabolites. Concentrations in the plasma of healthy subjects (mean age, 27 years), sampled during December were 51 (SD 17) nmol/L, 4.1 (SD 1.3) nmol/L, and 124 (SD 26) pmol/L for 25-hydroxyvitamin D, 24,25-dihydroxyvitamin D and 1,25-dihydroxyvitamin D, respectively. Intra- and interassay CVs for the three metabolites were 4.4 and 3.9%, 6.7 and 8.0%, and 7.0 and 4.8%, respectively.

scholarly journals Vitamin D3 metabolite ratio as an indicator of vitamin D status and its association with diabetes complications

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Lina H. M. Ahmed ◽  
Alexandra E. Butler ◽  
Soha R. Dargham ◽  
Aishah Latif ◽  
Omar M. Chidiac ◽  
...  
Keyword(s):  
Vitamin D ◽  
Vitamin D Deficiency ◽  
Diabetic Complications ◽  
Cross Sectional Study ◽  
Cross Sectional ◽  
Hydroxyvitamin D ◽  
Dihydroxyvitamin D ◽  
Metabolite Ratio ◽  
25 Hydroxyvitamin D ◽  
Artery Disease

Abstract Background Vitamin D deficiency is diagnosed by total serum 25-hydroxyvitamin D (25(OH)D) concentration and is associated with poor health and increased mortality; however, some populations have low 25(OH) D concentrations without manifestations of vitamin D deficiency. The Vitamin D Metabolite Ratio (VMR) has been suggested as a superior indicator of vitamin D status. Therefore, VMR was determined in a population with type 2 diabetes at high risk for vitamin D deficiency and correlated with diabetic complications. Research design and methods Four hundred sisty patients with type 2 diabetes (T2D) were recruited, all were vitamin D3 supplement naive. Plasma concentration of 25-hydroxyvitamin D3 (25(OH)D3) and its metabolites 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) and 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) and its epimer, 3-epi-25-hydroxyvitamin D3 (3-epi-25(OH)D3), were measured by LC-MS/MS analysis. VMR-1 was calculated as a ratio of 24,25(OH)2D3:25(OH)D3; VMR-2 as a ratio of 1,25(OH)2D3:25(OH)D3; VMR-3 was calculated as a ratio of 3-epi-25(OH)D3: 25(OH)D3. Results An association means that there were significant differences between the ratios found for those with versus those without the various diabetic complications studied. VMR-1 was associated with diabetic retinopathy (p = 0.001) and peripheral artery disease (p = 0.012); VMR-2 associated with hypertension (p < 0.001), dyslipidemia (p < 0.001), diabetic retinopathy (p < 0.001), diabetic neuropathy (p < 0.001), coronary artery disease (p = 0.001) and stroke (p < 0.05). VMR-3 associated with hypertension (p < 0.05), dyslipidemia (p < 0.001) and coronary artery disease (p < 0.05). Conclusions In this cross sectional study, whilst not causal, VMR-2 was shown to be the superior predictor of diabetic and cardiovascular complications though not demonstrative of causality in this cross-sectional study population over VMR-1, VMR-3 and the individual vitamin D concentration measurements; VMR-2 associated with both microvascular and cardiovascular indices and therefore may have utility in predicting the development of diabetic complications.

scholarly journals Association of Differing Qatari Genotypes with Vitamin D Metabolites

2020 ◽  
Vol 2020 ◽  
pp. 1-6
Author(s):  
Youssra Dakroury ◽  
Alexandra E. Butler ◽  
Soha R. Dargham ◽  
Aishah Latif ◽  
Amal Robay ◽  
...  
Keyword(s):  
Vitamin D ◽  
Skin Pigmentation ◽  
Genetic Differences ◽  
Vitamin D Metabolites ◽  
Vitamin D Metabolism ◽  
Hydroxyvitamin D ◽  
Dihydroxyvitamin D ◽  
Increased Risk ◽  
25 Hydroxyvitamin D

Objective. Genetic studies have identified four Qatari genotypes: Q1 Arab, Bedouin; Q2 Asian/Persian; Q3 African; and a fourth admixed group not fitting into the previous 3 groups. This study was undertaken to determine if there was an increased risk of deficiency of vitamin D and its metabolites associated with differing genotypes, perhaps due to genetic differences in skin pigmentation. Methods. 398 Qatari subjects (220 type 2 diabetes and 178 controls) had their genotype determined by Affymetrix 500 k SNP arrays. Total values of 1,25-dihydroxyvitamin D (1,25(OH)2D), 25-hydroxyvitamin D (25(OH)D), 24,25-dihydroxyvitamin D (24,25(OH)2D), and 25-hydroxy-3epi-vitamin D (3epi-25(OH)D) concentrations were measured by the LC-MS/MS analysis. Results. The distribution was as follows: 164 (41.2%) genotyped Q1, 149 (37.4%) genotyped Q2, 31 (7.8%) genotyped Q3, and 54 (13.6%) genotyped “admixed.” Median levels of 25(OH)D and 3epi-25(OH)D did not differ across Q1, Q2, Q3, and “admixed” genotypes, respectively. 1,25(OH)2D levels were lower (p<0.04) between Q2 and the admixed groups, and 24,25(OH)2D levels were lower (p<0.05) between Q1 and the admixed groups. Vitamin D metabolite levels were lower in females for 25(OH)D, 1,25(OH)2D (p<0.001), and 24,25(OH)2D (p<0.006), but 3epi-25(OH)D did not differ (p<0.26). Diabetes prevalence was not different between genotypes. Total 1,25(OH)2D (p<0.001), total 24,25(OH)2D (p<0.001), and total 3epi-25(OH)D (p<0.005) were all significantly lower in diabetes patients compared to controls whilst the total 25(OH)D was higher in diabetes than controls (p<0.001). Conclusion. Whilst 25(OH)D levels did not differ between genotype groups, 1,25(OH)2D and 24,25(OH)2D were lower in the admixed group, suggesting that there are genetic differences in vitamin D metabolism that may be of importance in a population that may allow a more targeted approach to vitamin D replacement. This may be of specific importance in vitamin D replacement strategies with the Q2 genotype requiring less, and the other genotypes requiring more to increase 1,25(OH)2D. Whilst overall the group was vitamin D deficient, total 25(OH)D was higher in diabetes, but 1,25(OH)2D, 24,25(OH)2D, and 3epi-25(OH)D were lower in diabetes that did not affect the relationship to genotype.

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