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Erschienen in:
01.10.2009 | Short Communication
Circulating β-carotene levels and type 2 diabetes—cause or effect?
Erschienen in: Diabetologia | Ausgabe 10/2009
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Aims/hypothesis
Circulating β-carotene levels are inversely associated with risk of type 2 diabetes, but the causal direction of this association is not certain. In this study we used a Mendelian randomisation approach to provide evidence for or against the causal role of the antioxidant vitamin β-carotene in type 2 diabetes.
Methods
We used a common polymorphism (rs6564851) near the BCMO1 gene, which is strongly associated with circulating β-carotene levels (p = 2 × 10−24), with each G allele associated with a 0.27 standard deviation increase in levels. We used data from the InCHIANTI and Uppsala Longitudinal Study of Adult Men (ULSAM) studies to estimate the association between β-carotene levels and type 2 diabetes. We next used a triangulation approach to estimate the expected effect of rs6564851 on type 2 diabetes risk and compared this with the observed effect using data from 4549 type 2 diabetes patients and 5579 controls from the Diabetes Genetics Replication And Meta-analysis (DIAGRAM) Consortium.
Results
A 0.27 standard deviation increase in β-carotene levels was associated with an OR of 0.90 (95% CI 0.86–0.95) for type 2 diabetes in the InCHIANTI study. This association was similar to that of the ULSAM study (OR 0.90 [0.84–0.97]). In contrast, there was no association between rs6564851 and type 2 diabetes (OR 0.98 [0.93–1.04], p = 0.58); this effect size was also smaller than that expected, given the known associations between rs6564851 and β-carotene levels, and the associations between β-carotene levels and type 2 diabetes.
Conclusions/interpretation
Our findings in this Mendelian randomisation study are in keeping with randomised controlled trials suggesting that β-carotene is not causally protective against type 2 diabetes.