title: Bone marrow fat is increased in chronic kidney disease by magnetic resonance spectroscopy.
abstract: In aging, the bone marrow fills with fat and this may lead to higher fracture risk. We show that a bone marrow fat measurement by magnetic resonance spectroscopy (MRS), a newer technique not previously studied in chronic kidney disease (CKD), is useful and reproducible. CKD patients have significantly higher bone marrow fat than healthy adults.
  
  
  BACKGROUND
  Renal osteodystrophy leads to increased morbidity and mortality in patients with CKD. Traditional bone biopsy histomorphometry is used to study abnormalities in CKD, but the bone marrow, the source of osteoblasts, has not been well characterized in patients with CKD.
  
  
  METHODS
  To determine the repeatability of bone marrow fat fraction assessment by MRS and water-fat imaging (WFI) at four sites in patients with CKD, testing was performed to determine the coefficients of reproducibility and intraclass coefficients (ICCs). We further determined if this noninvasive technique could be used to determine if there are differences in the percent bone marrow fat in patients with CKD compared to matched controls using paired t tests.
  
  
  RESULTS
  The mean age of subjects with CKD was 59.8 ± 7.2 years, and the mean eGFR was 24 ± 8 ml/min. MRS showed good reproducibility at all sites in subjects with CKD and controls, with a coefficient of reproducibilities ranging from 2.4 to 13 %. MRS and WFI assessment of bone marrow fat showed moderate to strong agreement (ICC 0.6-0.7) at the lumbar spine, with poorer agreement at the iliac crest and no agreement at the tibia. The mean percent bone marrow fat at L2-L4 was 13.8 % (95 % CI 8.3-19.7) higher in CKD versus controls (p < 0.05).
  
  
  CONCLUSIONS
  MRS is a useful and reproducible technique to study bone marrow fat in CKD. Patients with CKD have significantly higher bone marrow fat than healthy adults; the relationship with bone changes requires further analyses.
authors.affiliation: Division of Nephrology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA. rmoorthi@iu.edu.
authors.forename: R N
authors.initials: RN
authors.lastname: Moorthi
authors.affiliation: Department of Biostatistics, Indiana University School of Medicine, Indianapolis, IN, 46202, USA.|Richard M. Fairbanks School of Public Health, Indianapolis, IN, 46202, USA.
authors.forename: W
authors.initials: W
authors.lastname: Fadel
authors.affiliation: Department of Biostatistics, Indiana University School of Medicine, Indianapolis, IN, 46202, USA.|Richard M. Fairbanks School of Public Health, Indianapolis, IN, 46202, USA.
authors.forename: G J
authors.initials: GJ
authors.lastname: Eckert
authors.affiliation: Division of Nephrology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA.
authors.forename: K
authors.initials: K
authors.lastname: Ponsler-Sipes
authors.affiliation: Division of Nephrology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA.|Roudebush Veterans Administration Medical Center, Indianapolis, IN, 46202, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Moe
authors.affiliation: Department of Radiology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA.
authors.forename: C
authors.initials: C
authors.lastname: Lin
mesh_terms: D000273:Adipose Tissue / Q000473:pathology*; D000368:Aged; D001853:Bone Marrow / Q000473:pathology*; D016022:Case-Control Studies; D003928:Diabetic Nephropathies / Q000473:pathology / Q000503:physiopathology; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008297:Male; D008875:Middle Aged; D051436:Renal Insufficiency, Chronic / Q000473:pathology* / Q000503:physiopathology; D015203:Reproducibility of Results
keywords: Adipogenesis; Marrow fat; Spectroscopy; Water-fat imaging