# Multi-Omics Analyses Unveil the Effects of a Long-Term High-Salt, High-Fat, and High-Fructose Diet on Rats

## TL;DR

A long-term diet high in salt, fat, and fructose harms rats' metabolism, brain health, and gut bacteria, increasing risks of neurodegenerative diseases.

## Contribution

This study reveals how a combined high-salt, high-fat, and high-fructose diet affects brain and gut health through multi-omics analyses.

## Key findings

- The diet increased blood glucose, blood pressure, and harmful serum lipid levels in rats.
- Brain proteomic and metabolomic changes included glial cell proliferation and altered fatty acid metabolism.
- Gut microbiome disruption and elevated neuroinflammation suggest a link to neurodegenerative risks.

## Abstract

Background: Unhealthy diets characterized by high salt, fat, and fructose content are established risk factors for metabolic and cardiovascular disorders and may have indirect effects on cognitive function. However, the combined impact of a high-salt, high-fat, and high-fructose diet (HSHFHFD) on systemic physiology and brain health remains to be fully elucidated. Methods: Sprague-Dawley (SD) rats received a customized high-salt, high-fat diet supplemented with 30% fructose water for 18 weeks. Physiological and brain parameters were assessed, in combination with multi-omics analyses including brain proteomics and metabolomics, serum metabolomics, and gut microbiota profiling. Results: HSHFHFD significantly elevated blood glucose, blood pressure, and serum levels of TG, TC, and LDL in rats. Serum metabolomic profiling identified over 100 differentially abundant metabolites in the Model group. Proteomics, metabolomics, and gut microbiome integration revealed pronounced alterations in both brain proteomic and metabolomic profiles, with 155 differentially expressed proteins associated with glial cell proliferation and 65 differential metabolites linked to fatty acid and amino acid metabolism, among others. Experimental validation confirmed marked upregulation of GFAP and Bax protein, concomitant with downregulation of ZO-1 and occludin. Furthermore, HSHFHFD perturbed the CREB signaling pathway, leading to diminished BDNF expression. The levels of inflammatory factors, including IL-6, IL-10, IL-1β and TNFα, were significantly elevated in the brain. Oxidative stress was evident, as indicated by elevated malondialdehyde (MDA) levels, increased superoxide dismutase (SOD) activity, and altered NAD+/NADH ratio. Additionally, HSHFHFD significantly reduced the abundance of beneficial gut bacteria, including Lactobacillus, Romboutsia, and Monoglobus. Conclusions: HSHFHFD-induced depletion of gut Lactobacillus spp. may disrupt the linoleic acid metabolic pathway and gut–brain axis homeostasis, leading to the impairment of neuroprotective function, blood–brain barrier dysfunction, and exacerbated neuroinflammation and oxidative stress in the brain. These effects potentially increase the susceptibility of rats to neurodegenerative disorders.