Associations of homoarginine with bone metabolism and density, muscle strength and mortality: cross-sectional and prospective data from 506 female nursing home patients.

UNLABELLED: In female nursing home patients, homoarginine was associated with lower bone turnover, higher bone density, lower mortality and, by trend, with muscle strength.
INTRODUCTION: Homoarginine, a cationic amino acid, may be relevant for muscusloskeletal health because it inhibits alkaline phosphatases (AP) and is involved in nitric oxide and energy metabolism. We aimed to evaluate whether homoarginine serum concentrations are associated with bone density and metabolism, muscle strength, fractures and mortality.
METHODS: We examined a cohort of female nursing home patients that underwent quantitative bone ultrasound (QUS) measurements and assessments of knee extensor strength. Measurements of serum homoarginine, C-terminal telopeptide cross-links (β-CTxs) and osteocalcin were also performed at baseline. Thereafter, patients were followed-up with respect to fractures and mortality.
RESULTS: Serum homoarginine concentrations were determined in 506 female study participants (mean age: 83.9 ± 6.0 years). Homoarginine was inversely correlated with β-CTxs (r = -0.26; p < 0.001) and osteocalcin (r = -0.21; p < 0.001), and these associations remained significant in multiple regression analyses. Multivariate regression analyses showed that homoarginine is significantly associated with calcaneus stiffness (beta coefficient = 0.11; p = 0.020) and by trend with knee extensor strength (beta coefficient = 0.09; p = 0.065). During a mean follow-up time of 27 ± 8 months, we recorded 119 deaths (23.5%) and 63 fractures (12.5%). In multivariate analyses, homoarginine was associated with significantly reduced risk of mortality and the combined endpoint of fractures and mortality.
CONCLUSIONS: Whether homoarginine metabolism is critically involved into the pathogenesis of musculoskeletal diseases and fatal events warrants further studies.