High-fat diet induces an adaptive dysbiosis in the gut microbiota, associated with oxidative stress and the gut resistome profile in a rat model.

Antibiotic resistance is one of the main public health issues worldwide; therefore, studying the factors contributing to this problem, including the reservoirs of antibiotic resistance genes, is highly relevant. Among these reservoirs, the gut microbiota stands out for its potential to disseminate antibiotic resistance genetic determinants. In this context, identifying the factors shaping the gut resistome is crucial. This study aimed to evaluate the effects of a high-fat diet (HFD) on intestinal and systemic oxidative stress in a rat model and to assess its impact on the gut microbiota, its DNA oxidative damage, and the resistome. Oxidative stress was evaluated by quantifying oxidative stress markers in the host (MDA, T-SOD, and T-GSH/GSSG) and in the gut microbiota (8-OHdG), while the impact on the gut microbiota was determined using a shotgun metagenomic sequencing approach. The effect of HFD on oxidative stress, the gut microbiota, and its resistome was evaluated after 4, 8, and 12 weeks of exposure, with and without supplementation with an antioxidant (N-acetylcysteine). Results showed that a high-fat diet generates a pro-oxidant stimulus in intestinal tissue, with increased lipid peroxidation and superoxide dismutase activity, without systemic effects. In the gut microbiota, HFD altered microbial diversity, without DNA oxidative damage. Analysis of the predominant genera revealed an increased abundance of Mucispirillum, Phocaeicola, and Taurinivorans, among others, and a significant reduction of Segatella, Ligilactobacillus, and Prevotella, which were correlated with intestinal oxidative stress. On the other hand, Mucispirillum showed a significant negative correlation with DNA oxidative damage in the gut microbiota. Resistome characterization showed that a high-fat diet increased the abundance of antibiotic resistance genes (ARGs) in the gut microbiota. ARGs were strongly correlated with significantly modified taxa and showed a mild correlation with oxidative stress, while specific ARGs were associated with the high-fat diet (CblA-1, the vanH gene in the vanM cluster, vanD, and the vanXY gene in the vanE cluster). These findings suggest an adaptive dysbiosis, characterized by a microbial community restructuring associated with oxidative stress tolerance and antibiotic resistance genes.