Microbiota Co-Metabolism Alterations Precede Changes in the Host Metabolism in the Early Stages of Diet-Induced MASLD in Wistar Rats.

Metabolic-dysfunction-associated steatotic liver disease (MASLD) affects around 30% of the global population. The sexual dimorphism and gut microbiota play an important role in the early development of MASLD. The main objective of this research was to investigate metabolic changes during the early subclinical MASLD progression, for identifying the sequence of events and evaluating the impact of sexual dimorphism and the microbiota on the initial stages of MASLD development. Male and female Wistar rats 18 weeks old were randomly divided into different groups and fed a chow diet or a 45% high-fat diet for 21 weeks. Every three weeks, samples of serum, urine, and faeces were collected and studied by metabolomics. Furthermore, the liver was analysed at the endpoint. In addition, the gut microbiota was analysed from faecal samples over time using 16S rRNA gene-targeted group-specific primers. Our results revealed that three weeks on an HFD reduced the bacterial diversity in the faecal microbiota of Wistar rats, accompanied by changes in the faecal and urine metabolome. The HFD-induced alterations in microbiota-related co-metabolites in the liver, blood, urine, and faeces indicate a significant role of host-microbiota co-metabolism changes in the early stages of MASLD. In this study, we provide a comprehensive longitudinal analysis, detailing the sequence of events in the early development of MASLD. Our findings suggest that alterations in the gut microbiota diversity and co-metabolism occur before changes in host metabolism in the early onset of liver steatosis, a subclinical phase of MASLD.