Neuroinflammation and White Matter Alterations in Obesity Assessed by Diffusion Basis Spectrum Imaging

Amjad Samara; Tatianna Murphy; Jeremy Strain; Jerrel Rutlin; Peng Sun; Olga Neyman; Nitya Sreevalsan; Joshua S Shimony; Beau M Ances; Sheng-Kwei Song; Tamara Hershey; Sarah A Eisenstein

doi:10.3389/fnhum.2019.00464

Neuroinflammation and White Matter Alterations in Obesity Assessed by Diffusion Basis Spectrum Imaging

Front Hum Neurosci. 2020 Jan 14:13:464. doi: 10.3389/fnhum.2019.00464. eCollection 2019.

Authors

Amjad Samara¹, Tatianna Murphy¹, Jeremy Strain², Jerrel Rutlin¹, Peng Sun³, Olga Neyman¹, Nitya Sreevalsan¹, Joshua S Shimony³, Beau M Ances², Sheng-Kwei Song³, Tamara Hershey^{1

2

3

4}, Sarah A Eisenstein^{1

3}

Affiliations

¹ Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, United States.
² Department of Neurology, Washington University School of Medicine, St. Louis, MO, United States.
³ Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO, United States.
⁴ Department of Psychological & Brain Sciences, Washington University School of Medicine, St. Louis, MO, United States.

Abstract

Human obesity is associated with low-grade chronic systemic inflammation, alterations in brain structure and function, and cognitive impairment. Rodent models of obesity show that high-calorie diets cause brain inflammation (neuroinflammation) in multiple regions, including the hippocampus, and impairments in hippocampal-dependent memory tasks. To determine if similar effects exist in humans with obesity, we applied Diffusion Basis Spectrum Imaging (DBSI) to evaluate neuroinflammation and axonal integrity. We examined diffusion-weighted magnetic resonance imaging (MRI) data in two independent cohorts of obese and non-obese individuals (Cohort 1: 25 obese/21 non-obese; Cohort 2: 18 obese/41 non-obese). We applied Tract-based Spatial Statistics (TBSS) to allow whole-brain white matter (WM) analyses and compare DBSI-derived isotropic and anisotropic diffusion measures between the obese and non-obese groups. In both cohorts, the obese group had significantly greater DBSI-derived restricted fraction (DBSI-RF; an indicator of neuroinflammation-related cellularity), and significantly lower DBSI-derived fiber fraction (DBSI-FF; an indicator of apparent axonal density) in several WM tracts (all corrected p < 0.05). Moreover, using region of interest analyses, average DBSI-RF and DBSI-FF values in the hippocampus were significantly greater and lower, respectively, in obese relative to non-obese individuals (Cohort 1: p = 0.045; Cohort 2: p = 0.008). Hippocampal DBSI-FF and DBSI-RF and amygdalar DBSI-FF metrics related to cognitive performance in Cohort 2. In conclusion, these findings suggest that greater neuroinflammation-related cellularity and lower apparent axonal density are associated with human obesity and cognitive performance. Future studies are warranted to determine a potential role for neuroinflammation in obesity-related cognitive impairment.

Keywords: diffusion basis spectrum imaging; diffusion tensor imaging; neuroinflammation; obesity; white matter.

Abstract

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