# Ileum Proteomics Identifies Distinct Pathways Associated with Different Dietary Doses of Copper–Fructose Interactions: Implications for the Gut–Liver Axis and MASLD

## TL;DR

This study uses proteomics to uncover how different copper and fructose diets affect gut pathways linked to liver disease in rats.

## Contribution

The study identifies distinct ileum pathways associated with varying dietary copper–fructose interactions and their role in MASLD.

## Key findings

- CuAF diets enriched oxidative phosphorylation and ribosome pathways in the ileum.
- CuMF diets enriched arachidonic acid metabolism pathways.
- CuSF diets enriched focal adhesion, actin cytoskeleton regulation, and tight junction pathways.

## Abstract

The interactions of different dietary doses of copper with fructose contribute to the development of metabolic dysfunction-associated steatotic liver disease (MASLD) via the gut–liver axis. The underlying mechanisms remain elusive. The aim of this study was to identify the specific pathways leading to gut barrier dysfunction in the ileum using a proteomics approach in a rat model. Male weanling Sprague Dawley rats were fed diets with adequate copper (CuA), marginal copper (CuM), or supplemented copper (CuS) in the absence or presence of fructose supplementation (CuAF, CuMF, and CuSF) for 4 weeks. Ileum protein was extracted and analyzed with an LC-MS. A total of 2847 differentially expressed proteins (DEPs) were identified and submitted to functional enrichment analysis. As a result, the ileum proteome and signaling pathways that were differentially altered were revealed. Of note, the CuAF is characterized by the enrichment of oxidative phosphorylation and ribosome as analyzed with the KEGG; the CuMF is characterized by an enriched arachidonic acid metabolism pathway; and focal adhesion, the regulation of the actin cytoskeleton, and tight junction were significantly enriched by the CuSF. In conclusion, our proteomics analysis identified the specific pathways in the ileum related to the different dietary doses of copper–fructose interactions, suggesting that distinct mechanisms in the gut are involved in the development of MASLD.