Plasma dimethylglycine, nicotine exposure and risk of low bone mineral density and hip fracture: the Hordaland Health Study

• Published in: Osteoporosis international Vol. 26; no. 5; pp. 1573 - 1583
• Main Authors: Øyen, J., Svingen, G. F. T., Gjesdal, C. G., Tell, G. S., Ueland, P. M., Lysne, V., Apalset, E. M., Meyer, K., Vollset, S. E., Nygård, O. K.
• Format: Journal Article
• Language: English
• Published: London Springer London 01-05-2015; Springer Nature B.V
• Subjects: Absorptiometry, Photon - methods; Aged; Bone density; Bone Density - drug effects; Endocrinology; Female; Femur Neck - physiopathology; Fractures; Hip Fractures - blood; Hip Fractures - etiology; Hip Fractures - physiopathology; Hip joint; Humans; Kaplan-Meier Estimate; Male; Medicine; Medicine & Public Health; Middle Aged; Nicotine; Nicotine - adverse effects; Older people; Original Article; Orthopedics; Osteoporosis - blood; Osteoporosis - etiology; Osteoporosis - physiopathology; Osteoporotic Fractures - blood; Osteoporotic Fractures - etiology; Osteoporotic Fractures - physiopathology; Rheumatology; Risk Factors; Sarcosine - analogs & derivatives; Sarcosine - blood; Smoking; Smoking - adverse effects; Nicotine exposure; One-carbon metabolism; Hip fracture; Bone mineral density; Dimethylglycine; Smoking
• ISSN: 0937-941X; 1433-2965
• DOI: 10.1007/s00198-015-3030-4

Summary
In the large community-based Hordaland Health Study, low plasma dimethylglycine was associated with low bone mineral density in both middle-aged and elderly subjects and to an increased risk of subsequent hip fracture among the elderly. These associations seemed to be particularly strong among subjects exposed to nicotine.
Introduction
Dimethylglycine (DMG) is a product of the choline oxidation pathway and formed from betaine during the folate-independent remethylation of homocysteine (Hcy) to methionine. Elevated plasma DMG levels are associated with atherosclerotic cardiovascular disease and inflammation, which in turn are related to osteoporosis. High plasma total Hcy and low plasma choline are associated with low bone mineral density (BMD) and hip fractures, but the role of plasma DMG in bone health is unknown.
Methods
We studied the associations of plasma DMG with BMD among 5315 participants (46–49 and 71–74 years old) and with hip fracture among 3310 participants (71–74 years old) enrolled in the Hordaland Health Study.
Results
In age and sex-adjusted logistic regression models, subjects in the lowest versus highest DMG tertile were more likely to have low BMD (odds ratio [OR] 1.68, 95 % confidence interval [CI] 1.43–1.99). The association was stronger in participants exposed compared to those unexposed to nicotine (OR 2.31, 95 % CI 1.73–3.07 and OR 1.43, 95 % CI 1.16–1.75, respectively,
p
interaction = 0.008). In the older cohort, Cox regression analyses adjusted for sex showed that low plasma DMG was associated with an increased risk of hip fracture (hazard ratio [HR] 1.70, 95 % CI 1.28–2.26). A trend toward an even higher risk was found among women exposed to nicotine (HR 3.41, 95 % CI 1.40–8.28).
Conclusion
Low plasma DMG was associated with low BMD and increased risk of hip fractures. A potential effect modification by nicotine exposure merits particular attention.