Body mass index correlates negatively with white matter integrity in the fornix and corpus callosum: a diffusion tensor imaging study

Abstract

Overweight or obese body habitus is associated with cognitive deficits, impaired brain function, gray matter atrophy, and white matter (WM) hyperintensities. However, few diffusion tensor imaging (DTI) studies have assessed WM integrity in relation to overweight or obese status. This study assessed relationships between body mass index (BMI) and values of DTI parameters among 51 normal weight (lean), overweight, and obese participants who were otherwise healthy. BMI correlated negatively with fractional anisotropy and axial eigenvalues (λ(1)) in the body of corpus callosum (CC), positively with mean diffusivity and radial eigenvalues (See figure in text) in the fornix and splenium of CC, and positively with λ(1) in the right corona radiata (CR) and superior longitudinal fasciculus (SLF). These data indicate that BMI correlates negatively with WM integrity in the fornix and CC. Furthermore, the different patterns of BMI-related differences in DTI parameters at the fornix, body, and splenium of the CC, and the right CR and SLF suggest that different biological processes may underlie BMI-related impairments of WM integrity in different brain regions.

Figure 1

Correlations between BMI and FA values. Red‐yellow color on MNI T1 template indicates brain regions exhibiting significant correlations between BMI and FA values. Scatter‐plots demonstrate correlations between BMI values (x‐axis) and mean values of FA (y‐axis) within the indicated clusters. The green color shows the “group mean_FA_skeleton,” the number below each brain image indicates Z coordinates in MNI space, and only clusters surviving voxel level t > 2.0 and cluster P < 0.05, FWE‐corrected for multiple comparisons of voxel‐wise whole‐brain analysis are shown. Mean values of DTI parameters were calculated from all voxels in each significant cluster for each participant. Abbreviation: L = left.

Figure 2

Correlations between BMI and λ₁ values. Red‐yellow color on MNI T1 template indicates brain regions exhibiting significant correlations between BMI and λ₁ values. The green color shows the “group mean_FA_skeleton,” the number below each brain image indicates Z coordinates in MNI space, and only clusters surviving voxel level t > 2.0 and cluster P < 0.05, FWE‐corrected for multiple comparisons of voxel‐wise whole‐brain analysis are shown. Scatter‐plots demonstrate correlations between BMI values (x‐axis) and mean values of λ₁ (y‐axis) within each indicated cluster. Abbreviations: CC = corpus callosum; CR = corona radiata; L = left; SLF = superior longitudinal fasciculus.

Figure 3

Correlations between BMI and λ_⟂ values. Red‐yellow color on MNI T1 template indicates brain regions exhibiting significant correlations between BMI and λ_⟂ values. The green color shows the “group mean_FA_skeleton,” the number below each brain image indicates Z coordinates in MNI space, and only clusters surviving voxel level t > 2.0 and cluster P < 0.05, FWE‐corrected for multiple comparisons of voxel‐wise whole‐brain analysis are shown. Scatter‐plots demonstrate correlations between BMI values (x‐axis) and mean values of λ_⟂ (y‐axis) within each indicated cluster. Different ranges are used on the y‐axes of scatter plots given range differences in λ_⟂ values for the fornix and splenium. Abbreviation: L = left.

Figure 4

Correlations between BMI and MD values. Red‐yellow color on MNI T1 template indicates brain regions exhibiting significant correlations between BMI and MD values. The green color shows the “group mean_FA_skeleton,” the number below each brain image indicates Z coordinates in MNI space, and only clusters surviving voxel level t > 2.0 and cluster P < 0.05, FWE‐corrected for multiple comparisons of voxel‐wise whole‐brain analysis are shown. Scatter‐plots demonstrate the correlations between BMI values (x‐axis) and mean values of MD (y‐axis) within each indicated cluster. Different ranges are used on the y‐axes of scatter plots given range differences in MD values for the fornix and splenium. Abbreviation: L = left.