The circulating sphingosine-1-phosphate level predicts incident fracture in postmenopausal women: a 3.5-year follow-up observation study.

ABSTRACT

UNLABELLED A high level of circulating sphingosine-1-phosphate (S1P) is associated with a high incidence of osteoporotic fracture and a high rate of an insufficient response to bisphosphonate therapy. INTRODUCTION: Sphingosine-1-phosphate (S1P) is a significant regulator of bone metabolism. Recently, we found that a high plasma S1P level is associated with low bone mineral density (BMD), high levels of bone resorption markers (BRMs), and a high risk of prevalent vertebral fracture in postmenopausal women. We investigated the possibility that S1P is a predictor of incident fracture. METHODS: A total of 248 postmenopausal women participated in this longitudinal study and were followed up for a mean duration of 3.5 years (untreated [n = 76] or treated with bisphosphonate or hormone replacement therapy [n = 172]). The baseline plasma S1P level and prevalent and incident fracture occurrence were assessed. RESULTS: A high S1P level was significantly associated with a higher rate of prevalent fracture after adjusting for femoral neck (FN) BMD, BRM, and potential confounders (odds ratio = 2.05; 95 % confidence interval [CI] = 1.03-4.00). Incident fractures occurred more frequently in the highest S1P tertile (T3) than in the lower two tertiles (T1-2) after adjusting for confounders, including baseline FN BMD, prevalent fracture, antiosteoporotic medication, annualized changes in FN BMD, BRM, and potential confounders (hazard ratio = 5.52; 95 % CI = 1.04-56.54). Insufficient response to bisphosphonate therapy occurred more frequently in T3 than T1-2 (odds ratio = 4.43; 95 % CI = 1.02-21.25). CONCLUSIONS: The plasma S1P level may be a potential predictor of fracture occurrence and an insufficient response to bisphosphonate therapy in postmenopausal women.