title: Association of Bone Marrow Sphingosine 1-phosphate Levels with Osteoporotic Hip Fractures.
abstract: BACKGROUND
  Sphingosine 1-phosphate (S1P) has been discovered to be a critical regulator of bone metabolism. Very recently, we found that higher circulating S1P levels were associated with higher rate of prevalent osteoporotic fracture in human.
  
  
  METHODS
  This was a cross-sectional study of 16 patients who underwent hip replacement surgeries. Bone marrow fluids were obtained during hip surgeries, and the S1P levels were measured using a competitive enzyme-linked immunosorbent assay (ELISA) assay. Bone mineral densities (BMDs) at various skeletal sites were obtained using dual energy X-ray absorptiometry.
  
  
  RESULTS
  Among 16 patients, 4 patients were undergone operations due to hip fractures, and the others were done by any other causes. Bone marrow S1P levels were significantly lower in patients with hip fractures than in those without, before and after adjusting for confounding factors (P=0.047 and 0.025, respectively). We failed to demonstrate significant associations between bone marrow S1P levels and any BMD values (γ=0.026-0.482, P=0.171-0.944).
  
  
  CONCLUSIONS
  In conjunction with our previous findings, these suggest that the effects of gradient between peripheral blood and bone marrow, but not S1P itself, may be the most critical on bone metabolism.
authors: Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Seong Hee
authors: SH
authors: Ahn
authors: Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Jung-Min
authors: JM
authors: Koh
authors: Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Eun Jeong
authors: EJ
authors: Gong
authors: Division of Orthopedic Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Seongeun
authors: S
authors: Byun
authors: Asan Institute for Life Sciences, Seoul, Korea.
authors: Sun-Young
authors: SY
authors: Lee
authors: Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Beom-Jun
authors: BJ
authors: Kim
authors: Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Seung Hun
authors: SH
authors: Lee
authors: Division of Orthopedic Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Jae Suk
authors: JS
authors: Chang
authors: Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Ghi Su
authors: GS
authors: Kim
keywords: Bone density; Osteoporotic fracture; Sphingosine 1-phosphate