title: Hyperhomocysteinemia induces a tissue specific accumulation of homocysteine in bone by collagen binding and adversely affects bone.
abstract: BACKGROUND
  Recently, hyperhomocysteinemia (HHCY) has been suggested to have adverse effects on bone. This study investigated if an experimental HHCY in rats induces an accumulation of homocysteine (HCY) in bone tissue that is accompanied by bone loss and reduced bone strength.
  
  
  METHODS
  HHCY was induced in healthy rats by either a methionine (Meth)- or a homocystine (Homo)-enriched diet and compared with controls. Homocystine is the product of two disulfide linked HCY molecules. Tissue and plasma concentrations of HCY, S-adenosylhomocysteine (SAH) and S-adenosylmethionine (SAM) were measured. Bones were assessed by biomechanical testing, histomorphometry, microCT and the measurement of biochemical bone turnover markers in plasma.
  
  
  RESULTS
  Meth and Homo animals developed a significant HHCY that was accompanied by a tissue specific accumulation of HCY (1300 to 2000% vs. controls). 65% of HCY in bone was bound to collagen of the extracellular matrix. The SAH / SAM-ratio in bone and plasma of Meth and Homo animals exhibited a tissue specific increase indicating a reduced methylation capacity. Accumulation of HCY in bone was characterized by a distinct reduction of cancellous bone (proximal femur: -25 to -35%; distal femur -56 to -58%, proximal tibia: -28 to -43%). Accordingly, bone strength was significantly reduced (-9 to -12%).
  
  
  CONCLUSIONS
  A tissue specific accumulation of HCY in bone may be a promising mechanism explaining adverse effects of HHCY on bone. A reduced methylation capacity of bone cells might be another relevant pathomechanism.
authors.affiliation: Department of Clinical Chemistry and Laboratory Medicine, University Hospital of Saarland, Homburg, Germany. markusherr@aol.com
authors.forename: Markus
authors.initials: M
authors.lastname: Herrmann
authors.forename: Andrea
authors.initials: A
authors.lastname: Tami
authors.forename: Britt
authors.initials: B
authors.lastname: Wildemann
authors.forename: Martin
authors.initials: M
authors.lastname: Wolny
authors.forename: Alexandra
authors.initials: A
authors.lastname: Wagner
authors.forename: Heike
authors.initials: H
authors.lastname: Schorr
authors.forename: Omid
authors.initials: O
authors.lastname: Taban-Shomal
authors.forename: Natalia
authors.initials: N
authors.lastname: Umanskaya
authors.forename: Steffen
authors.initials: S
authors.lastname: Ross
authors.forename: Patric
authors.initials: P
authors.lastname: Garcia
authors.forename: Ulrich
authors.initials: U
authors.lastname: Hübner
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Herrmann
mesh_terms: D000368:Aged; D000818:Animals; D001842:Bone and Bones / Q000033:anatomy & histology / Q000737:chemistry / Q000378:metabolism* / Q000473:pathology; D003094:Collagen / Q000378:metabolism*; D005260:Female; D006710:Homocysteine / Q000378:metabolism*; D006711:Homocystine / Q000008:administration & dosage; D006801:Humans; D020138:Hyperhomocysteinemia / Q000139:chemically induced / Q000378:metabolism*; D008297:Male; D008715:Methionine / Q000008:administration & dosage; D009206:Myocardium / Q000737:chemistry; D010024:Osteoporosis / Q000378:metabolism; D016062:Porosity; D051381:Rats; D017208:Rats, Wistar; D012435:S-Adenosylhomocysteine / Q000378:metabolism; D012436:S-Adenosylmethionine / Q000378:metabolism; D013314:Stress, Mechanical
chemical_list: D006710:Homocysteine; D006711:Homocystine; D012436:S-Adenosylmethionine; D003094:Collagen; D012435:S-Adenosylhomocysteine; D008715:Methionine