A Prospective Randomized Controlled Trial of the Effects of Vitamin D Supplementation on Cardiovascular Disease Risk

Vitamin D (VitD) supplementation has been advocated for cardiovascular risk reduction; however, supporting data are sparse. The objective of this study was to determine whether VitD supplementation reduces cardiovascular risk. Subjects in this prospective, randomized, double-blind, placebo-controlled trial of post-menopausal women with serum 25-hydroxyvitamin D concentrations >10 and <60 ng/mL were randomized to Vitamin D3 2500 IU or placebo, daily for 4 months. Primary endpoints were changes in brachial artery flow-mediated vasodilation (FMD), carotid-femoral pulse wave velocity (PWV), and aortic augmentation index (AIx). The 114 subjects were mean (standard deviation) 63.9 (3.0) years old with a 25-hydroxyvitamin D level of 31.3 (10.6) ng/mL. Low VitD (<30 ng/mL) was present in 47% and was associated with higher body-mass index, systolic blood pressure, glucose, CRP, and lower FMD (all p<0.05). After 4 months, 25-hydroxyvitamin D levels increased by 15.7 (9.3) ng/mL on vitamin D3 vs. −0.2 (6.1) ng/mL on placebo (p<0.001). There were no significant differences between groups in changes in FMD (0.3 [3.4] vs. 0.3 [2.6] %, p = 0.77), PWV (0.00 [1.06] vs. 0.05 [0.92] m/s, p = 0.65), AIx (2.7 [6.3] vs. 0.9 [5.6] %, p = 0.10), or CRP (0.3 [1.9] vs. 0.3 [4.2] mg/L, p = 0.97). Multivariable models showed no significant interactions between treatment group and low VitD status (<30 ng/mL) for changes in FMD (p = 0.65), PWV (p = 0.93), AIx (p = 0.97), or CRP (p = 0.26).In conclusion, VitD supplementation did not improve endothelial function, arterial stiffness, or inflammation. These observations do not support use of VitD supplementation to reduce cardiovascular disease risk

Locally harvested foods support serum 25-hydroxyvitamin D sufficiency in an indigenous population of Western Alaska

Background: Low serum vitamin D is associated with higher latitude, age, body fat percentage and low intake of fatty fish. Little documentation of vitamin D concentrations is available for Alaska Native populations. Objective: This study was undertaken to investigate serum 25-hydroxyvitamin D (25(OH)D) concentrations of the Yup'ik people of southwestern Alaska in relation to demographic and lifestyle variables, particularly with the use of locally harvested (local) foods. Design: Cross-sectional study. Methods: We estimated 25(OH)D, dietary vitamin D and calcium, percent of energy from local foods and demographic variables in 497 Yup'ik people (43% males) aged 14–92 residing in southwestern Alaska. Sampling was approximately equally divided between synthesizing and non-synthesizing seasons, although the preponderance of samples were drawn during months of increasing daylight. Results: Mean vitamin D intake was 15.1±20.2 µg/d, while local foods accounted for 22.9±17.1% of energy intake. The leading sources of vitamin D were local fish (90.1%) followed by market foods. Mean 25(OH)D concentration was 95.6±40.7 nmol/L. Participants in the upper 50th percentile of 25(OH)D concentration tended to be older, male, of lower body mass index, sampled during the synthesizing season, and among the upper 50th percentile of local food use. Conclusions: A shift away from locally harvested foods will likely increase the risk for serum 25(OH)D insufficiency in this population

Effects of interacting networks of cardiovascular risk genes on the risk of type 2 diabetes mellitus (the CODAM study)

Background: Genetic dissection of complex diseases requires innovative approaches for identification of disease-predisposing genes. A well-known example of a human complex disease with a strong genetic component is Type 2 Diabetes Mellitus (T2DM). Methods: We genotyped normal-glucose-tolerant subjects (NGT; n = 54), subjects with an impaired glucose metabolism (IGM; n = 111) and T2DM (n = 142) subjects, in an assay (designed by Roche Molecular Systems) for detection of 68 polymorphisms in 36 cardiovascular risk genes. Using the single-locus logistic regression and the so-called haplotype entropy, we explored the possibility that (1) common pathways underlie development of T2DM and cardiovascular disease which would imply enrichment of cardiovascular risk polymorphisms in "pre-diabetic" (IGM) and diabetic (T2DM) populations- and (2) that gene-gene interactions are relevant for the effects of risk polymorphisms. Results: In single-locus analyses, we showed suggestive association with disturbed glucose metabolism (i.e. subjects who were either IGM or had T2DM), or with T2DM only. Moreover, in the haplotype entropy analysis, we identified a total of 14 pairs of polymorphisms (with a false discovery rate of 0.125) that may confer risk of disturbed glucose metabolism, or T2DM only, as members of interacting networks of genes. We substantiated gene-gene interactions by showing that these interacting networks can indeed identify potential "disease-predisposing allele-combinations". Conclusion: Gene-gene interactions of cardiovascular risk polymorphisms can be detected in prediabetes and T2DM, supporting the hypothesis that common pathways may underlie development of T2DM and cardiovascular disease. Thus, a specific set of risk polymorphisms, when simultaneously present, increases the risk of disease and hence is indeed relevant in the transfer of risk

Expression of the Multiple Sclerosis-Associated MHC Class II Allele HLA-DRB1*1501 Is Regulated by Vitamin D

Multiple sclerosis (MS) is a complex trait in which allelic variation in the MHC class II region exerts the single strongest effect on genetic risk. Epidemiological data in MS provide strong evidence that environmental factors act at a population level to influence the unusual geographical distribution of this disease. Growing evidence implicates sunlight or vitamin D as a key environmental factor in aetiology. We hypothesised that this environmental candidate might interact with inherited factors and sought responsive regulatory elements in the MHC class II region. Sequence analysis localised a single MHC vitamin D response element (VDRE) to the promoter region of HLA-DRB1. Sequencing of this promoter in greater than 1,000 chromosomes from HLA-DRB1 homozygotes showed absolute conservation of this putative VDRE on HLA-DRB1*15 haplotypes. In contrast, there was striking variation among non–MS-associated haplotypes. Electrophoretic mobility shift assays showed specific recruitment of vitamin D receptor to the VDRE in the HLA-DRB1*15 promoter, confirmed by chromatin immunoprecipitation experiments using lymphoblastoid cells homozygous for HLA-DRB1*15. Transient transfection using a luciferase reporter assay showed a functional role for this VDRE. B cells transiently transfected with the HLA-DRB1*15 gene promoter showed increased expression on stimulation with 1,25-dihydroxyvitamin D3 (P = 0.002) that was lost both on deletion of the VDRE or with the homologous “VDRE” sequence found in non–MS-associated HLA-DRB1 haplotypes. Flow cytometric analysis showed a specific increase in the cell surface expression of HLA-DRB1 upon addition of vitamin D only in HLA-DRB1*15 bearing lymphoblastoid cells. This study further implicates vitamin D as a strong environmental candidate in MS by demonstrating direct functional interaction with the major locus determining genetic susceptibility. These findings support a connection between the main epidemiological and genetic features of this disease with major practical implications for studies of disease mechanism and prevention

Socioeconomic questionnaire and clinical assessment in the HELENA Cross-sectional Study: methodology

Rationale: Environmental factors such as dietary habits, breastfeeding, socioeconomic conditions and educational factors are strong influences on nutritional and puberty status, physical activity, food choices and their interactions. Several diseases of adulthood seem to be linked to, or to originate from, lifestyle in childhood and adolescence. Objective: The aims of this study are to describe birth parameters and socioeconomic factors and to assess clinical status in adolescents aged 13-16 years from 10 European countries participating in the Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) Cross-Sectional Study (CSS). Methodology: A self-report questionnaire on the socioeconomic status, a parental questionnaire concerning neonatal period and also a case report form (CRF), in which clinical items during clinical examination (such as medical history, treatments, anthropometry, Tanner staging, blood pressure, heart rate) were assessed. To develop these documents, first a list of items was established, a search of existing documents was performed and the advice of local and international experts was taken. All documents (questionnaires and an operations manual) were discussed in plenary HELENA meetings; a final version of these documents was fixed, and the process of translation and back translation was performed. Results: The questionnaires and CRF were tested for validation in all 10 participant cities; 208 adolescents were enrolled during the pilot study. All items that caused problems or questions in one or more participating centers or were completed by < 85% of the adolescents were reviewed before the beginning of the HELENA-CSS. Conclusion: These final questionnaires and CRF will contribute to better understanding of the inequalities in nutrition, behavior and health in the European adolescent population. The experience and process should be useful for other multicenter studies

Age-Related Skeletal Dynamics and Decrease in Bone Strength in DNA Repair Deficient Male Trichothiodystrophy Mice

Accumulation of DNA damage caused by oxidative stress is thought to be one of the main contributors of human tissue aging. Trichothiodystrophy (TTD) mice have a mutation in the Ercc2 DNA repair gene, resulting in accumulation of DNA damage and several features of segmental accelerated aging. We used male TTD mice to study the impact of DNA repair on bone metabolism with age. Analysis of bone parameters, measured by micro-computed tomography, displayed an earlier decrease in trabecular and cortical bone as well as a loss of periosteal apposition and a reduction in bone strength in TTD mice with age compared to wild type mice. Ex vivo analysis of bone marrow differentiation potential showed an accelerated reduction in the number of osteogenic and osteoprogenitor cells with unaltered differentiation capacity. Adipocyte differentiation was normal. Early in life, osteoclast number tended to be increased while at 78 weeks it was significantly lower in TTD mice. Our findings reveal the importance of genome stability and proper DNA repair for skeletal homeostasis with age and support the idea that accumulation of damage interferes with normal skeletal maintenance, causing reduction in the number of osteoblast precursors that are required for normal bone remodeling leading to a loss of bone structure and strength