The association between plasma homocysteine levels, methylation capacity and incident osteoporotic fractures

Background: An elevated level of plasma homocysteine (Hey) is a known risk factor for osteoporotic fractures. In addition, Hey is related to DNA-methylation metabolism. To determine whether the association between Hey and fractures is explained by an altered methylation capacity, we investigated the associations between levels of s-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) and fracture risk. Methods: We studied 503 females aged 55 years and over from the Rotterdam Study (RS) in whom plasma Hey, SAM and SAH levels were measured. Bone mineral density (BMD) at the hip was assessed using DXA. Incident fractures were recorded over a mean period of 7.0 years. Cox proportional hazards analysis and linear regression were used to assess relationships between plasma metabolite levels, incident osteoporotic fractures and BMD. Results: Over a total of 3502 person-years of follow-up, 103 subjects sustained at least one osteoporotic fracture. Whereas incidence of osteoporotic fractures was associated with quartiles of Hey (p = 0.047), it was not associated with quartiles of SAM, SAH or SAM/SAH-ratio (all p for trend > 0.6). Stepwise linear regression showed that SAM/SAH-ratio, but not Hey, was independently associated with hip BMD (beta = 0.073, p = 0.025). Conclusion: Since SAM, SAH and SAM/SAH-ratio were not associated with osteoporotic fractures, alterations in methylation capacity most likely do not appear to be an important factor in the association between Hey and fractures. (C) 2012 Elsevier Inc. All rights reserved.