Serum Vitamin D Concentrations Are Not Associated with Insulin Resistance in Swiss Adults.

BACKGROUND: Low vitamin D status has been associated with an increased risk of developing type 2 diabetes and insulin resistance (IR), although this has been recently questioned. OBJECTIVE: We examined the association between serum vitamin D metabolites and incident IR. METHODS: This was a prospective, population-based study derived from the CoLaus (Cohorte Lausannoise) study including 3856 participants (aged 51.2 ± 10.4 y; 2217 women) free from diabetes or IR at baseline. IR was defined as a homeostasis model assessment (HOMA) index >2.6. Fasting plasma insulin and glucose were measured at baseline and at follow-up to calculate the HOMA index. The association of vitamin D metabolites with incident IR was analyzed by logistic regression, and the results were expressed for each independent variable as ORs and 95% CIs. RESULTS: During the 5.5-y follow-up, 649 (16.9%) incident cases of IR were identified. Participants who developed IR had lower baseline serum concentrations of 25-hydroxyvitamin D3 [25(OH)D3 (25-hydroxycholecalciferol); 45.9 ± 22.8 vs. 49.9 ± 22.6 nmol/L; P < 0.001], total 25(OH)D3 (25(OH)D3 + epi-25-hydroxyvitamin D3 [3-epi-25(OH)D3]; 49.1 ± 24.3 vs. 53.3 ± 24.1 nmol/L; P < 0.001), and 3-epi-25(OH)D3 (4.2 ± 2.9 vs. 4.3 ± 2.5 nmol/L; P = 0.01) but a higher 3-epi- to total 25(OH)D3 ratio (0.09 ± 0.05 vs. 0.08 ± 0.04; P = 0.007). Multivariable analysis adjusting for month of sampling, age, and sex showed an inverse association between 25(OH)D3 and the likelihood of developing IR [ORs (95% CIs): 0.86 (0.68, 1.09), 0.60 (0.46, 0.78), and 0.57 (0.43, 0.75) for the second, third, and fourth quartiles compared with the first 25(OH)D3 quartile; P-trend < 0.001]. Similar associations were found between total 25(OH)D3 and incident IR. There was no significant association between 3-epi-25(OH)D3 and IR, yet a positive association was observed between the 3-epi- to total 25(OH)D3 ratio and incident IR. Further adjustment for body mass index, sedentary status, and smoking attenuated the association between 25(OH)D3, total 25(OH)D3, and the 3-epi- to total 25(OH)D3 ratio and the likelihood of developing IR. CONCLUSION: In the CoLaus study in healthy adults, the risk of incident IR is not associated with serum concentrations of 25(OH)D3 and total 25(OH)D3.

A Population-Based Model to Consider the Effect of Seasonal Variation on Serum 25(OH)D and Vitamin D Status.

Background. We elaborated a model that predicts the centiles of the 25(OH)D distribution taking into account seasonal variation. Methods. Data from two Swiss population-based studies were used to generate (CoLaus) and validate (Bus Santé) the model. Serum 25(OH)D was measured by ultra high pressure LC-MS/MS and immunoassay. Linear regression models on square-root transformed 25(OH)D values were used to predict centiles of the 25(OH)D distribution. Distribution functions of the observations from the replication set predicted with the model were inspected to assess replication. Results. Overall, 4,912 and 2,537 Caucasians were included in original and replication sets, respectively. Mean (SD) 25(OH)D, age, BMI, and % of men were 47.5 (22.1) nmol/L, 49.8 (8.5) years, 25.6 (4.1) kg/m(2), and 49.3% in the original study. The best model included gender, BMI, and sin-cos functions of measurement day. Sex- and BMI-specific 25(OH)D centile curves as a function of measurement date were generated. The model estimates any centile of the 25(OH)D distribution for given values of sex, BMI, and date and the quantile corresponding to a 25(OH)D measurement. Conclusions. We generated and validated centile curves of 25(OH)D in the general adult Caucasian population. These curves can help rank vitamin D centile independently of when 25(OH)D is measured.

Vitamin D: a review on its effects on muscle strength, the risk of fall, and frailty.

Vitamin D is the main hormone of bone metabolism. However, the ubiquitary nature of vitamin D receptor (VDR) suggests potential for widespread effects, which has led to new research exploring the effects of vitamin D on a variety of tissues, especially in the skeletal muscle. In vitro studies have shown that the active form of vitamin D, calcitriol, acts in myocytes through genomic effects involving VDR activation in the cell nucleus to drive cellular differentiation and proliferation. A putative transmembrane receptor may be responsible for nongenomic effects leading to rapid influx of calcium within muscle cells. Hypovitaminosis D is consistently associated with decrease in muscle function and performance and increase in disability. On the contrary, vitamin D supplementation has been shown to improve muscle strength and gait in different settings, especially in elderly patients. Despite some controversies in the interpretation of meta-analysis, a reduced risk of falls has been attributed to vitamin D supplementation due to direct effects on muscle cells. Finally, a low vitamin D status is consistently associated with the frail phenotype. This is why many authorities recommend vitamin D supplementation in the frail patient.

Interplay of vitamin D, erythropoiesis, and the renin-angiotensin system.

For many years deficiency of vitamin D was merely identified and assimilated to the presence of bone rickets. It is now clear that suboptimal vitamin D status may be correlated with several disorders and that the expression of 1-α-hydroxylase in tissues other than the kidney is widespread and of clinical relevance. Recently, evidence has been collected to suggest that, beyond the traditional involvement in mineral metabolism, vitamin D may interact with other kidney hormones such as renin and erythropoietin. This interaction would be responsible for some of the systemic and renal effects evoked for the therapy with vitamin D. The administration of analogues of vitamin D has been associated with an improvement of anaemia and reduction in ESA requirements. Moreover, vitamin D deficiency could contribute to an inappropriately activated or unsuppressed RAS, as a mechanism for progression of CKD and/or cardiovascular disease. Experimental data on the anti-RAS and anti-inflammatory effects treatment with active vitamin D analogues suggest a therapeutic option particularly in proteinuric CKD patients. This option should be considered for those subjects that are intolerant to anti-RAS agents or, as add-on therapy, in those already treated with anti-RAS but not reaching the safe threshold level of proteinuria.

Vitamin D receptor alleles and bone mineral density in a normal premenopausal Brazilian female population

Studies on the association between vitamin D receptor (VDR) polymorphism and bone mineral density (BMD) in different populations have produced conflicting results probably due to ethnic differences in the populations studied. The Brazilian population is characterized by a very broad genetic background and a high degree of miscegenation. Of an initial group of 164, we studied 127 women from the city of São Paulo, aged 20 to 47 years (median, 31 years), with normal menses, a normal diet and no history of diseases or use of any medication that could alter BMD. VDR genotype was assessed by PCR amplification followed by BsmI digestion of DNA isolated from peripheral leukocytes. BMD was measured using dual energy X-ray absorptiometry (Lunar DPX) at the lumbar site (L2-L4) and femoral neck. Most of the women (77.6%) were considered to be of predominantly European ancestry (20.6% of them reported also native American ancestry), 12.8% were of African-Brazilian ancestry and 9.6% of Asian ancestry, 41.0% (52) were classified as bb, 48.8% (62) as Bb and 10.2% (13) as BB. The BB, Bb and bb groups did not differ in age, height, weight, body mass index or age at menarche. Lumbar spine BMD was significantly higher in the bb group (1.22 ± 0.16 g/cm²) than in the BB group (1.08 ± 0.14; P<0.05), and the Bb group presented an intermediate value (1.17 ± 0.15). Femoral neck BMD was higher in the bb group (0.99 ± 0.11 g/cm²) compared to Bb (0.93 ± 0.12) and BB (0.90 ± 0.09) (P<0.05). These data indicate that there is a significant correlation between the VDR BsmI genotype and BMD in healthy Brazilian premenopausal females.

Fractures of the proximal femur: correlation with vitamin D receptor gene polymorphism

Fractures are the feared consequences of osteoporosis and fractures of the proximal femur (FPF) are those that involve the highest morbidity and mortality. Thus far, evaluation of bone mineral density (BMD) is the best way to determine the risk of fracture. Genetic inheritance, in turn, is one of the major determinants of BMD. A correlation between different genotypes of the vitamin D receptor (VDR) and BMD has been recently reported. On this basis, we decided to determine the importance of the determination of VDR genotype in the presence of an osteoporotic FPF in a Brazilian population. We studied three groups: group I consisted of 73 elderly subjects older than 65 years (78.5 ± 7.2 years) hospitalized for nonpathological FPF; group II consisted of 50 individuals older than 65 years (72.9 ± 5.2 years) without FPF and group III consisted of 98 young normal Brazilian individuals aged 32.6 ± 6.6 years (mean ± SD). Analysis of VDR gene polymorphism by restriction fragment length polymorphism (RFLP) was performed by PCR amplification followed by BsmI digestion of DNA isolated from peripheral leukocytes. The genotype distribution in group I was 20.5% BB, 42.5% Bb and 37% bb and did not differ significantly from the values obtained for group II (16% BB, 36% Bb and 48% bb) or for group III (10.2% BB, 47.6% Bb and 41.8% bb). No differences in genotype distribution were observed between sexes or between the young and elderly groups. We conclude that determination of VDR polymorphism is of no practical use for the prediction of FPF. Other nongenetic factors probably start to affect bone mass, the risk to fall and consequently the occurrence of osteoporotic fractures with advancing age.

Differential regulation of vitamin D receptor expression in distinct leukemic cell lines upon phorbol ester-induced growth arrest

A close correlation between vitamin D receptor (VDR) abundance and cell proliferation rate has been shown in NIH-3T3 fibroblasts, MCF-7 breast cancer and in HL-60 myeloblastic cells. We have now determined if this association occurs in other leukemic cell lines, U937 and K562, and if VDR content is related to c-myc expression, which is also linked to cell growth state. Upon phorbol myristate acetate (PMA) treatment, cells from the three lineages (HL-60, U937 and K562) differentiated and expressed specific surface antigens. All cell lines analyzed were growth inhibited by PMA and the doubling time was increased, mainly due to an increased fraction of cells in the G0/G1 phase, as determined by flow cytometry measurements of incorporated bromodeoxyuridine and cell DNA content. C-myc mRNA expression was down-regulated and closely correlated to cell growth arrest. However, VDR expression in leukemic cell lines, as determined by immunofluorescence and Northern blot assays, was not consistently changed upon inhibition of cell proliferation since VDR levels were down-regulated only in HL-60 cells. Our data suggest that VDR expression cannot be explained simply as a reflection of the leukemic cell growth state.

Genetic polymorphisms in vitamin D receptor, vitamin D-binding protein, Toll-like receptor 2, nitric oxide synthase 2, and interferon-γ genes and its association with susceptibility to tuberculosis

Mycobacterium tuberculosis kills more people than any other single pathogen, with an estimated one-third of the world's population being infected. Among those infected, only 10% will develop the disease. There are several demonstrations that susceptibility to tuberculosis is linked to host genetic factors in twins, family and associated-based case control studies. In the past years, there has been dramatic improvement in our understanding of the role of innate and adaptive immunity in the human host defense to tuberculosis. To date, attention has been paid to the role of genetic host and parasitic factors in tuberculosis pathogenesis mainly regarding innate and adaptive immune responses and their complex interactions. Many studies have focused on the candidate genes for tuberculosis susceptibility ranging from those expressed in several cells from the innate or adaptive immune system such as Toll-like receptors, cytokines (TNF-α, TGF-β, IFN-γ, IL-1b, IL-1RA, IL-12, IL-10), nitric oxide synthase and vitamin D, both nuclear receptors and their carrier, the vitamin D-binding protein (VDBP). The identification of possible genes that can promote resistance or susceptibility to tuberculosis could be the first step to understanding disease pathogenesis and can help to identify new tools for treatment and vaccine development. Thus, in this mini-review, we summarize the current state of investigation on some of the genetic determinants, such as the candidate polymorphisms of vitamin D, VDBP, Toll-like receptor, nitric oxide synthase 2 and interferon-γ genes, to generate resistance or susceptibility to M. tuberculosis infection.

Effect of vitamin D therapy in addition to amitriptyline on migraine attacks in pediatric patients

The purpose of this study was to investigate the effect of supplementary vitamin D therapy in addition to amitriptyline on the frequency of migraine attacks in pediatric migraine patients. Fifty-three children 8-16 years of age and diagnosed with migraine following the International Headache Society 2005 definition, which includes childhood criteria, were enrolled. Patients were classified into four groups on the basis of their 25-hydroxyvitamin D [25(OH)D] levels. Group 1 had normal 25(OH)D levels and received amitriptyline therapy alone; group 2 had normal 25(OH)D levels and received vitamin D supplementation (400 IU/day) plus amitriptyline; group 3 had mildly deficient 25(OH)D levels and received amitriptyline plus vitamin D (800 IU/day); and group 4 had severely deficient 25(OH)D levels and was given amitriptyline plus vitamin D (5000 IU/day). All groups were monitored for 6 months, and the number of migraine attacks before and during treatment was determined. Calcium, phosphorus alkaline phosphatase, parathormone, and 25(OH)D levels were also determined before and during treatment. Results were compared between the groups. Data obtained from the groups were analyzed using one-way analysis of variance. The number of pretreatment attacks in groups 1 to 4 was 7±0.12, 6.8±0.2, 7.3±0.4, and 7.2±0.3 for 6 months, respectively (all P>0.05). The number of attacks during treatment was 3±0.25, 1.76±0.37 (P<0.05), 2.14±0.29 (P<0.05), and 1.15±0.15 (P<0.05), respectively. No statistically significant differences in calcium, phosphorus, alkaline phosphatase, or parathormone levels were observed (P>0.05). Vitamin D given in addition to anti-migraine treatment reduced the number of migraine attacks.

Low serum concentrations of 25-hydroxyvitamin D in children and adolescents with systemic lupus erythematosus

We evaluated the concentrations of 25-hydroxyvitamin D [25(OH)D] in children and adolescents with juvenile systemic lupus erythematosus (JSLE) and associated them with disease duration and activity, use of medication (chloroquine and glucocorticoids), vitamin D intake, calcium and alkaline phosphatase levels, and bone mineral density. Thirty patients with JSLE were evaluated and compared to 30 healthy individuals, who were age and gender matched. Assessment was performed of clinical status, disease activity, anthropometry, laboratory markers, and bone mineral density. The 30 patients included 25 (83.3%) females and 16 (53.3%) Caucasians, with a mean age of 13.7 years. The mean age at diagnosis was 10.5 years and mean disease duration was 3.4 years. Mean levels of calcium, albumin, and alkaline phosphatase were significantly lower in patients with JSLE compared with controls (P<0.001, P=0.006, and P<0.001, respectively). Twenty-nine patients (97%) and 23 controls (77%) had 25(OH)D concentrations lower than 32 ng/mL, with significant differences between them (P<0.001). Fifteen patients (50%) had vitamin D levels <20 ng/mL and 14 had vitamin D levels between 20 and 32 ng/mL. However, these values were not associated with greater disease activity, higher levels of parathormone, medication intake, or bone mineral density. Vitamin D concentrations were similar with regard to ethnic group, body mass index, height for age, and pubertal stage. Significantly more frequently than in controls, we observed insufficient serum concentrations of 25(OH)D in patients with JSLE; however, we did not observe any association with disease activity, higher levels of parathormone, lower levels of alkaline phosphatase, use of medications, or bone mineral density alterations.

Vitamin D and Kidney disease: what we know and what we do not know

Vitamin D deficiency is common in the chronic kidney disease (CKD) population. CKD has been recognized as a significant public health problem and CKD patients are at increased risk of total and cardiovascular morbidity and mortality. There are increasing epidemiological data suggesting that vitamin D deficiency may play a role in overall morbidity and mortality associated with CKD. The vitamin D hormonal system is classically implicated in the regulation of calcium homeostasis and bone metabolism but there is ample evidence to support the claim that extra renal conversion of 25(OH)D to 1.25(OH)2 has significant biological roles beyond those traditionally ascribed to vitamin D. Based on the current state of evidence this review intends to give an update on novel biological and clinical insights with relevance to the steroid hormone vitamin D specifically in patients with kidney disease.

Vitamin D status and latent tuberculosis infection : a preliminary study in a group of healthy Mexican agricultural workers

Vitamin D metabolites are important in the regulation of bone and calcium homeostasis, but also have a more ubiquitous role in the regulation of cell differentiation and immune function. Severely low circulating 25-dihydroxyvitamin D [25(OH)D] concentrations have been associated with the onset of active tuberculosis (TB) in immigrant populations, although the association with latent TB infection (LTBI) has not received much attention. A previous study identified the prevalence of LTBI among a sample of Mexican migrant workers enrolled in Canada's Seasonal Agricultural Workers Program (SA WP) in the Niagara Region of Ontario. The aim of the present study was to determine the vitamin D status of the same sample, and identify if a relationship existed with LTBI. Studies of vitamin D deficiency and active TB are most commonly carried out among immigrant populations to non-endemic regions, in which reactivation of LTBI has occurred. Currently, there is limited knowledge of the association between vitamin D deficiency and LTBI. Entry into Canada ensured that these individuals did not have active TB, and L TBI status was established previously by an interferon-gamma release assay (IGRA) (QuantiFERON-TB Gold In-Tube®, Cellestis Ltd., Australia). Awareness of vitamin D status may enable individuals at risk of deficiency to improve their nutritional health, and those with LTBI to be aware of this risk factor for disease. Prevalence of vitamin D insufficiency among the Mexican migrant workers was determined from serum samples collected in the summer of 2007 as part of the cross sectional LTBI study. Samples were measured for concentrations of the main circulating vitamin D metabolite, 25(OH)D, with a widely used 1251 250HD RIA (DiaSorin Inc.®, Stillwater, MN), and were categorized as deficient «37.5 nmoI/L), insufficient (>37.5 nmollL, < 80 nmol/L) or sufficient (2::80 nmoI/L). Fisher's exact tests and t tests were used to determine if vitamin D status (sufficiency or insufficiency) or 25(OH)D concentrations significantly differed by sex or age categories. Predictors of vitamin D insufficiency and 25(OH)D concentrations were taken from questionnaires carried out during the previous study, and analyzed in the present study using multiple regression prediction models. Fisher's exact test and t test was used to determine if vitamin D status or 25(OH)D concentration differed by LTBI status. Strength of the relationship between interferongamma (IFN-y) concentration (released by peripheral T cells in response to TB antigens) and 25(OH)D concentration was analyzed using a Spearman correlation. Out of 87 participants included in the study (78% male; mean age 38 years), 14 were identified as LTBI positive but none had any signs or symptoms of TB reactivation. Only 30% of the participants were vitamin D sufficient, whereas 68% were insufficient and 2% were deficient. Significant independent predictors of lower 25(OH)D concentrations were sex, number of years enrolled in the SA WP and length of stay in Canada. No significant differences were found between 25(OH)D concentrations and LTBI status. There was a significant moderate correlation between IFN-y and 25(OH)D concentrations ofLTBI-positive individuals. The majority of participants presented with Vitamin D insufficiency but none were severely deficient, indicating that 25(OH)D concentrations do not decrease dramatically in populations who temporarily reside in Canada but go back to their countries of origin during the Canadian winter. This study did not find a statistical relationship between low levels of vitamin D and LTBI which suggests that in the presence of overall good health, lower than ideal levels of 2S(OH)D, may still be exerting a protective immunological effect against LTBI reactivation. The challenge remains to determine a critical 2S(OH)D concentration at which reactivation is more likely to occur.

Évaluation de la densité osseuse et du statut nutritionnel en vitamine D chez des enfants prépubères avec allergie au lait non résolue

L'allergie au lait de vache (ALV) représente l'allergie alimentaire la plus fréquemment rencontrée durant l'enfance. Cette allergie a longtemps été reconnue comme transitoire mais des données récentes révèlent que celle-ci est persistante chez environ 15% des enfants qui en sont touchés durant l'enfance, posant ainsi un risque à leur santé. La présente étude examine 26 enfants avec ALV et 12 enfants contrôles recrutés au CHU Sainte-Justine durant l’hiver 2011-2012. L'objectif étant de comparer la densité minérale osseuse (DMO) et les niveaux sériques de 25(OH)D d'enfants prépubères avec ALV non résolue à un groupe contrôle d'enfants avec autres allergies alimentaires, en plus d'évaluer les apports en calcium et en vitamine D ainsi que l'adhérence à la supplémentation chez cette population. La DMO lombaire (L2-L4) ne diffère pas significativement entre les groupes. Cependant, une faible densité osseuse, caractérisée par un score-Z entre -1,0 et -2,0 pour l'âge et le sexe, est détectée chez plus de 30% des enfants avec ALV et plus de 16% du groupe contrôle, sans allergie au lait. Tel qu'attendu, les apports en calcium sont significativement moins élevés chez les enfants avec ALV comparé au groupe contrôle, avec près de 90% de tous nos participants ne rencontrant pas les besoins pour l’âge en vitamine D. Plus de la moitié des enfants avec ALV présentent une concentration de 25(OH)D inférieure à 75 nmol/L. Cependant, notre étude n'a décelé aucune différence entre les niveaux sériques de 25(OH)D des enfants avec ALV comparativement au groupe contrôle. Enfin, l'adhérence à la supplémentation est jugée adéquate chez plus de 75% de notre groupe d'enfants avec ALV, soit ≧ 4 journées par semaine, un facteur aussi associé à une meilleure atteinte de leurs apports nutritionnels en calcium et en vitamine D. Enfin, ces résultats soulignent l'importance de suivre la santé osseuse d'enfants avec ALV ainsi qu'avec allergies multiples, qui présentent un risque de faible densité osseuse. L'intervention nutritionnelle devrait suivre l'adhérence à la supplémentation chez les enfants avec ALV non résolue, afin d'optimiser les apports nutritionnels insuffisants en calcium et en vitamine D

Niveles de vitamina d y prevalencia de déficit de vitamina d en mujeres postmenopáusicas mayores de 50 años en Bogotá

Objetivo: Describir los niveles de vitamina D y calcular prevalencia de déficit de vitamina D en mujeres postmenopáusicas mayores de 50 años que asisten a consulta de medicina general en una muestra en de la ciudad de Bogotá durante el periodo 2013-2014. Pacientes y métodos: Realizamos un estudio descriptivo para estimar el déficit de VD en mujeres postmenopáusicas entre 50 y 80 años en la ciudad de Bogotá y la prevalencia de hipovitaminosis D. Durante el periodo octubre 2013 a octubre 2014 se analizaron 320 muestras, se identificaron las características socio-demográficas, patológicas y la exposición a radiación ultravioleta de cada participante. Se realizó un análisis descriptivo de las variables, se estableció su asociación con el déficit de vitamina D su aporte estadístico con al mismo. Resultados :El promedio de edad en la muestra fue de 61 años y el promedio de edad en la que reportaron la ultima menstruación fue a los 43 años. Con respecto a las características socio-demográficas 50% de las mujeres pertenecieron a los estratos 3 y 4, únicamente 11% de los pacientes realizaron una carrera universitaria y 73% de la mujeres fueron amas de casa. Con respecto a los niveles de vitamina D, 81% de los pacientes presentaron niveles anormales y el promedio de 25(OH)D en la población estudio fue de 19,81ng/ml. Conclusión: La prevalencia de déficit de vitamina D en mujeres bogotanas postmenopáusicas es significativo. Se requiere incrementar la exposición solar o dar suplencia con vitamina D para disminuir el riesgo de fracturas.