Specific white matter tissue microstructure changes associated with obesity

Andreas Fritsche,Martin Heni,Stephanie Kullmann,Hans-Ulrich Häring,Nikolaus Weiskopf,Hubert Preissl,Ralf Veit,Martina F Callaghan,Klaus Scheffler

doi:10.1016/j.neuroimage.2015.10.006

Abstract

Obesity-related structural brain alterations point to a consistent reduction in gray matter with increasing body mass index (BMI) but changes in white matter have proven to be more complex and less conclusive. Hence, more recently diffusion tensor imaging (DTI) has been employed to investigate microstructural changes in white matter structure. Altogether, these studies have mostly shown a loss of white matter integrity with obesity-related factors in several brain regions. However, the variety of these obesity-related factors, including inflammation and dyslipidemia, resulted in competing influences on the DTI indices. To increase the specificity of DTI results, we explored specific brain tissue properties by combining DTI with quantitative multi-parameter mapping in lean, overweight and obese young adults. By means of multi-parameter mapping, white matter structures showed differences in MRI parameters consistent with reduced myelin, increased water and altered iron content with increasing BMI in the superior longitudinal fasciculus, anterior thalamic radiation, internal capsule and corpus callosum. BMI-related changes in DTI parameters revealed mainly alterations in mean and axial diffusivity with increasing BMI in the corticospinal tract, anterior thalamic radiation and superior longitudinal fasciculus. These alterations, including mainly fiber tracts linking limbic structures with prefrontal regions, could potentially promote accelerated aging in obese individuals leading to an increased risk for cognitive decline.

Highlights

Besides the strong association with numerous health conditions and changes in blood pressure, inflammation, dyslipidemia and insulin resistance (Bastard et al, 2006; Johnson et al, 2012), obesity is related to changes in cognitive functions
body mass index (BMI) was associated with significantly lower R1 within a cluster ranging from the left superior longitudinal fasciculus, anterior thalamic radiation, anterior and posterior part of the internal capsule to the body and genu of the corpus callosum (Table 2, Fig. 1) (p b 0.05, family wise error corrected (FWE)-corrected)
We explored specific tissue properties of white matter microstructure by combining diffusion tensor imaging (DTI) with quantitative multi-parametric mapping in lean, overweight and obese young adults

Summary

Introduction

Besides the strong association with numerous health conditions and changes in blood pressure, inflammation, dyslipidemia and insulin resistance (Bastard et al, 2006; Johnson et al, 2012), obesity is related to changes in cognitive functions These alterations include an increased risk for dementia and an accelerated cognitive decline in older age, with complementary structural and functional brain changes (Gunstad et al, 2007; Gustafson et al, 2003). Recent studies in this fast growing field have mainly focused on changes in volume or density of gray (GM) and white matter (WM) using voxel-based (VBM) and tensor-based morphometry (TBM). Cortical thickness, a more specific and direct measure of gray matter, recently confirmed these obesity-related GM alterations showing cortical thinning with increased BMI mainly in frontal, temporal and parietal regions (Hassenstab et al, 2012; Marques-Iturria et al, 2013; Veit et al, 2014)

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Results

Conclusion