title: Changes in vertebral bone marrow fat and bone mass after gastric bypass surgery: A pilot study.
abstract: Bone marrow fat may serve a metabolic role distinct from other fat depots, and it may be altered by metabolic conditions including diabetes. Caloric restriction paradoxically increases marrow fat in mice, and women with anorexia nervosa have high marrow fat. The longitudinal effect of weight loss on marrow fat in humans is unknown. We hypothesized that marrow fat increases after Roux-en-Y gastric bypass (RYGB) surgery, as total body fat decreases. In a pilot study of 11 morbidly obese women (6 diabetic, 5 nondiabetic), we measured vertebral marrow fat content (percentage fat fraction) before and 6 months after RYGB using magnetic resonance spectroscopy. Total body fat mass declined in all participants (mean ± SD decline 19.1 ± 6.1 kg or 36.5% ± 10.9%, p<0.001). Areal bone mineral density (BMD) decreased by 5.2% ± 3.5% and 4.1% ± 2.6% at the femoral neck and total hip, respectively, and volumetric BMD decreased at the spine by 7.4% ± 2.8% (p<0.001 for all). Effects of RYGB on marrow fat differed by diabetes status (adjusted p=0.04). There was little mean change in marrow fat in nondiabetic women (mean +0.9%, 95% CI -10.0 to +11.7%, p=0.84). In contrast, marrow fat decreased in diabetic women (-7.5%, 95% CI -15.2 to +0.1%, p=0.05). Changes in total body fat mass and marrow fat were inversely correlated among nondiabetic (r=-0.96, p=0.01) but not diabetic (r=0.52, p=0.29) participants. In conclusion, among those without diabetes, marrow fat is maintained on average after RYGB, despite dramatic declines in overall fat mass. Among those with diabetes, RYGB may reduce marrow fat. Thus, future studies of marrow fat should take diabetes status into account. Marrow fat may have unique metabolic behavior compared with other fat depots.
authors.affiliation: Department of Medicine, University of California, San Francisco, CA, USA; Medical Service, San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA. Electronic address: anne.schafer@ucsf.edu.
authors.forename: A L
authors.initials: AL
authors.lastname: Schafer
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA.
authors.forename: X
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Epidemiology and Biostatistics, University of California, San Francisco, CA, USA.
authors.forename: A V
authors.initials: AV
authors.lastname: Schwartz
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA.
authors.forename: L S
authors.initials: LS
authors.lastname: Tufts
authors.affiliation: Department of Medicine, University of California, San Francisco, CA, USA; Medical Service, San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA.
authors.forename: A L
authors.initials: AL
authors.lastname: Wheeler
authors.affiliation: Department of Medicine, University of California, San Francisco, CA, USA; Medical Service, San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA.
authors.forename: C
authors.initials: C
authors.lastname: Grunfeld
authors.affiliation: Department of Surgery, University of California, San Francisco, CA, USA; Surgical Service, San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA.
authors.forename: L
authors.initials: L
authors.lastname: Stewart
authors.affiliation: Department of Surgery, University of California, San Francisco, CA, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Rogers
authors.affiliation: Department of Surgery, University of California, San Francisco, CA, USA.
authors.forename: J T
authors.initials: JT
authors.lastname: Carter
authors.affiliation: Department of Surgery, University of California, San Francisco, CA, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Posselt
authors.affiliation: Department of Epidemiology and Biostatistics, University of California, San Francisco, CA, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Black
authors.affiliation: Department of Medicine, University of California, San Francisco, CA, USA; Medical Service, San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Shoback
mesh_terms: D050154:Adiposity; D000328:Adult; D015519:Bone Density; D001853:Bone Marrow / Q000473:pathology*; D003920:Diabetes Mellitus / Q000378:metabolism; D005260:Female; D015390:Gastric Bypass; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D008875:Middle Aged; D010865:Pilot Projects; D013131:Spine / Q000473:pathology*
chemical_list: D006442:Glycated Hemoglobin
keywords: Bariatric surgery; Bone marrow fat; Diabetes; Gastric bypass surgery