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Seasonal genetic influence on serum 25-hydroxyvitamin D levels: a twin study
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Orthopaedics.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, UCR-Uppsala Clinical Research Center. (Clinical Pharmacogenetics and Osteoporosis)
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Anaesthesiology and Intensive Care. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, UCR-Uppsala Clinical Research Center.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, UCR-Uppsala Clinical Research Center.
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2009 (English)In: PloS one, ISSN 1932-6203, Vol. 4, no 11, e7747- p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Although environmental factors, mainly nutrition and UV-B radiation, have been considered major determinants of vitamin D status, they have only explained a modest proportion of the variation in serum 25-hydroxyvitamin D. We aimed to study the seasonal impact of genetic factors on serum 25-hydroxyvitamin D concentrations. METHODOLOGY/PRINCIPAL FINDINGS: 204 same-sex twins, aged 39-85 years and living at northern latitude 60 degrees, were recruited from the Swedish Twin Registry. Serum 25-hydroxyvitamin D was analysed by high-pressure liquid chromatography and mass spectrometry. Genetic modelling techniques estimated the relative contributions of genetic, shared and individual-specific environmental factors to the variation in serum vitamin D. The average serum 25-hydroxyvitamin D concentration was 84.8 nmol/l (95% CI 81.0-88.6) but the seasonal variation was substantial, with 24.2 nmol/l (95% CI 16.3-32.2) lower values during the winter as compared to the summer season. Half of the variability in 25-hydroxyvitamin D during the summer season was attributed to genetic factors. In contrast, the winter season variation was largely attributable to shared environmental influences (72%; 95% CI 48-86%), i.e., solar altitude. Individual-specific environmental influences were found to explain one fourth of the variation in serum 25-hydroxyvitamin D independent of season. CONCLUSIONS/SIGNIFICANCE: There exists a moderate genetic impact on serum vitamin D status during the summer season, probably through the skin synthesis of vitamin D. Further studies are warranted to identify the genes impacting on vitamin D status.

Place, publisher, year, edition, pages
2009. Vol. 4, no 11, e7747- p.
National Category
Surgery
Research subject
Orthopaedics
Identifiers
URN: urn:nbn:se:uu:diva-110673DOI: 10.1371/journal.pone.0007747ISI: 000271721900006PubMedID: 19915719OAI: oai:DiVA.org:uu-110673DiVA: diva2:277976
Available from: 2009-11-23 Created: 2009-11-23 Last updated: 2013-08-15Bibliographically approved
In thesis
1. Boning up on Vitamin D: Observational Studies on Bone and Health
Open this publication in new window or tab >>Boning up on Vitamin D: Observational Studies on Bone and Health
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The primary function of vitamin D in humans is to maintain sufficient circulating calcium concentrations. Low vitamin D levels could result in excessive calcium resorption from bone. Vitamin deficiency may therefore decrease bone mineral density (BMD), resulting in an increased risk of fracture. This thesis sought to determine the association between vitamin D intake and bone health and to estimate circulating levels of vitamin D optimal for bone health without increasing the risk for non-bone disease. Furthermore, the thesis assessed the difference in performance between common serum vitamin D assays and the genetic influence of vitamin D status.

In prospective population-based cohorts, blood concentrations <40 nmol/L (lowest 5%) increased the risk of fracture in elderly men. Low levels were further associated with a slight decrease in lumbar spine BMD. Both high (>98 nmol/L) and low (<46 nmol/L) vitamin D levels were associated with higher cancer and overall mortality. In another cohort, also of older men and women, no association was found between vitamin D levels and fracture. Low vitamin D levels were weakly associated with decreased total body BMD in men but not in women.

Dietary intake of vitamin D over a 20-year period in more than 60,000 Swedish women was not associated with osteoporosis or fracture, regardless of calcium intake. During summer, dietary vitamin D intake and other life style habits are of minor importance for the variation in vitamin D levels relative to sun exposure and genes. In summer time, genes explain about half  of the variation in vitamin D levels, but none of the variance in winter time. The variability between vitamin D assays was substantial. Three assays classified 8, 22 and 43% of the same study population as vitamin D insufficient if <50 nmol/L was set as the insufficiency level.

Based on the results in this thesis, low 25(OH)D levels and low dietary vitamin D intake are not a major cause of fractures in community-dwelling elderly Swedish women and men. Differences in assay performance and potential negative health outcomes of high 25(OH)D levels need to be considered.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 68 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 711
Keyword
Vitamin D, fracture, BMD, assays, genes, mortality, cohort studies
National Category
Orthopedics
Research subject
Orthopaedics
Identifiers
urn:nbn:se:uu:diva-159873 (URN)978-91-554-8184-1 (ISBN)
Public defence
2011-11-25, Grönwallsalen, Ing. 70, Akademiska Sjukhuset, Uppsala, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2011-11-03 Created: 2011-10-11 Last updated: 2011-11-10Bibliographically approved

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Snellman, GretaMelhus, HåkanGedeborg, RolfMichaëlsson, Karl

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