Integrative analysis of physiological responses to high fat feeding with diffusion tensor images and neurochemical profiles of the mouse brain

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Abstract
Background: Obesity proceeds with important physiological and microstructural alterations in the brain, but the precise relationships between the diet and feeding status, its physiological responses, and the observed neuroimaging repercussions, remain elusive. Here, we implemented a mouse model of high fat diet (HFD) feeding to explore specific associations between diet, feeding status, phenotypic and endocrine repercussions, and the resulting microstructural and metabolic alterations in the brain, as detected by diffusion tensor imaging (DTI) and neurochemical metabolic profiling. Methods: Brain DTI images were acquired from adult male C57BL6/J mice after 6 weeks of HFD, or standard diet (SD) administrations, both under the fed, and overnight fasted conditions. Metabolomic profiles of the cortex (Ctx), hippocampus (Hipc), and hypothalamus (Hyp) were determined by 1H high-resolution magic angle spinning (HRMAS) spectroscopy, in cerebral biopsies dissected after microwave fixation. Mean diffusivity (MD), fractional anisotropy (FA) maps, and HRMAS profiles were complemented with determinations of phenotypic alterations and plasma levels of appetite-related hormones, measured by indirect calorimetry and multiplex assays, respectively. We used Z-score and alternating least squares scaling (ALSCAL) analysis to investigate specific associations between diet and feeding status, physiological, and imaging parameters. Results: HFD induced significant increases in body weight and the plasma levels of glucose and fatty acids in the fed and fasted conditions, as well as higher cerebral MD (Ctx, Hipc, Hyp), FA (Hipc), and mobile saturated fatty acids resonances (Ctx, Hipc, Hyp). Z-score and ASLCAL analysis identified the precise associations between physiological and imaging variables. Conclusions: The present study reveals that diet and feeding conditions elicit prominent effects on specific imaging and spectroscopic parameters of the mouse brain that can be associated to the alterations in phenotypic and endocrine variables. Together, present results disclose a neuro-inflammatory response to HFD, characterized primarily by vasogenic edema and compensatory responses in osmolyte concentrations.

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