Abstract
Background and Aim
Recent studies revealed a link between hypovitaminosis D3 and the risk for hyperglycemia. Further mechanistic and interventional investigations suggested a common reason for both conditions rather than a causal relationship. Exposure to sunlight is the most relevant source of vitamin D3 (25(OH)D), whereas adipose tissue is able to store relevant amounts of the lipophilic vitamin. Since running/bicycling leads to increased out-door time and alters physiological response mechanisms, it can be hypothesized that the correlation between hypovitaminosis D3 and hyperglycemia might be disturbed in outdoor athletes.
Methods
47 elderly marathoners/bicyclists and 47 age/sex matched controls were studied in a longitudinal setting at baseline and after three years. HbA1c as a surrogate for (pre-)diabetic states was quantified via HPLC, 25(OH)D levels were measured by means of chemiluminescent assays. Physical performance was assessed by ergometry.
Results
When adjusted for seasonal variations, 25(OH)D was significantly higher in athletes than in controls. 25(OH)D levels inversely correlated with triglycerides in both groups, whereas only in controls an association between high BMI or low physical performance with hypovitaminosis D3 had been found. Likewise, the presence of hypovitaminosis D3 at baseline successfully predicted hyperglycemia at the follow up examinations within the control group (AUC = 0.85, 95% CI [0.74, 0.96], p < .001, statistically independent from BMI), but not in athletes.
Conclusion
Our data suggest that mechanisms of HbA1c elevation might differ between athletes and controls. Thus, intense physical activity must be taken into account as a potential pre-analytic confounder when it is aimed to predict metabolic risk by vitamin D3 levels.
Citation: Haslacher H, Nistler S, Batmyagmar D, Ponocny-Seliger E, Perkmann T, Scherzer TM, et al. (2016) Low Vitamin D Levels Do Not Predict Hyperglycemia in Elderly Endurance Athletes (but in Controls). PLoS ONE 11(6):
e0157695.
https://doi.org/10.1371/journal.pone.0157695
Editor: Klaus Roemer, University of Saarland Medical School, GERMANY
Received: April 5, 2016; Accepted: June 2, 2016; Published: June 15, 2016
Copyright: © 2016 Haslacher et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: To protect participant confidentiality, data are available on request. Requests may be sent to Dr. Helmuth Haslacher (Helmuth.haslacher@meduniwien.ac.at).
Funding: This trial was supported by the Anniversary Fund of the Austrian National Bank (No. 14511, No. 12979), https://www.oenb.at/en/About-Us/Research-Promotion/The- OeNBAnniversary-Fund.html. Moreover, authors EP and GE are currently affiliated with commercial companies. However, neither these companies nor the funder (Austrian National Bank), who inter alia provided support in the form of salaries for authors (EP, DB), did have any role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist. The private-sector affiliations of authors EP and GE do neither constitute conflicts of interest regarding the present study nor do they alter the authors’ adherence to PLOS ONE policies on sharing data and materials.
Description
The study examines the relationship between vitamin D levels and hyperglycemia in elderly endurance athletes compared to controls.