Impact of Marrow Adiposity on Trabecular Microarchitecture and Strength Estimates in Adolescents with Morbid Obesity

Presentation Number: OR06-6
Date of Presentation: April 4th, 2017

Vibha Singhal*1, Fatima Cody Stanford2, Alexander Toth3, Charu Baskaran1, Brian Carmine4, Miriam A. Bredella1 and Madhusmita Misra5
1Massachusetts General Hospital/Harvard Medical School, Boston, MA, 2MGH, 3Massachusetts General Hospital, Boston, MA, 4Boston Medical Center, 5Massachusetts General Hospital and Harvard Medical School, Boston, MA

Abstract

Purpose: Childhood obesity is associated with a high incidence of forearm fractures, especially of the distal radius, suggesting greater skeletal fragility. In adults with obesity, increased skeletal fragility has been associated with greater marrow adipose tissue (MAT). Preclinical studies show that high-fat diet causes persistent changes in trabecular bone quality and skeletal fragility even after weight loss. Recent studies in rats indicate that high-fat diets induce inflammation in MAT, associated with suboptimal development of trabecular bone. However, data are lacking regarding associations of MAT with trabecular microarchitecture in adolescents with obesity.

Objective: To determine whether marrow adiposity is associated with trabecular microarchitectural parameters at the distal radius in adolescents with severe obesity. We hypothesized that marrow adiposity at the L4 vertebra (trabecular site) would be negatively associated with trabecular microarchitectural parameters at the distal radius in this population.

Methods: We recruited 17 adolescents with severe obesity who underwent 3D HR- pQCT of the distal radius with an isotropic voxel size of 82 μm (Xtreme CT, Scanco Medical, Basserdorf, Switzerland). Measures of trabecular microarchitecture, including individual trabecular segmentation (ITS), were assessed. ITS models the trabecular region as a lattice of individual plates and rods, with a predominance of plate morphology typically associated with greater bone strength than rod morphology. These data were further used to evaluate strength estimates using micro-finite element analysis (FEA). MAT content of the L4 vertebra was quantified by 1H-MR spectroscopy at 3Tesla and expressed as a lipid to water ratio. Linear regression analysis was performed to determine whether marrow adiposity is associated with trabecular microarchitectural parameters at the distal radius.

Results: Participants (15 female and 2 male) had a mean age of 17.6 ± 2.4 yrs and a mean BMI of 44.5 ± 7.1 kg/m2. None of the participants exercised regularly for more than 2 hours per week in the preceding year and none had a history of diabetes. MAT at L4 was negatively associated with trabecular von Mises stress (a strength estimate) at the distal radius (r= -0.51; p= 0.04), and with trabecular thickness (r= -0.52; p= 0.048) and plate bone volume fraction (r= -0.51; p= 0.04). Similar trends were observed with axial bone volume fraction and plate trabecular number. Conversely, L4 MAT was associated positively with rod bone volume fraction (r= 0.51; p= 0.04) and rod-rod junction density (r= 0.53; p= 0.03). No correlations were detected with trabecular volumetric BMD, trabecular area or stiffness at the distal radius.

Conclusion: Higher lumbar MAT is associated with adverse changes in the trabecular compartment of the distal radius in adolescents with severe obesity.

 

Disclosure: FCS: Consultant, Novo Nordisk. Nothing to Disclose: VS, AT, CB, BC, MAB, MM