Abstract
White adipose tissue browning promotes type 2 diabetes (T2D) control. A gut microbiome (GM)-adipose tissue axis is involved, but the mechanisms are unclear. This study aims to demonstrate the causal role of human GM in browning in a T2D model and unveil underlying mechanisms, and to identify the molecules that promote browning. T2D mice will undergo GM depletion by antibiotics with or without fecal microbiota transplantation from children with highly active brown adipose tissue. The following will be measured: body weight, food intake, glucose/insulin tolerance, glucose metabolism and adipose depot density (by PET/CT imaging), browning, intestinal wall morphology and hypothalamic inflammation (by histology). Metabolomics and molecular analyses of blood and adipose tissue, and GM profiling will allow identifying involved taxa, functional pathways and molecules. Selected molecules will be tested in vitro on adipose tissue explants from T2D mice to identify new therapeutic leads. RESULTS ACHIEVED The project was implemented through the coordinated work of the operational units at the CNR – Centro Nazionale delle Ricerche (RU1), the Marche Polytechnic University (RU2) and the University of Bologna (RU3). The different units contributed with complementary expertise in pre-clinical studies, histology, immunohistochemistry, electron microscopy, gut microbiome analysis and metabolomics. Through this collaboration, the project successfully achieved its scientific objectives, and in particular for RU3, provided new insights into whether the gut microbiome contributes to the browning of white adipose tissue in T2D. Using a preclinical humanized fecal microbiota transplantation (FMT) model, the study followed four experimental groups: healthy controls, a T2D group, an antibiotic-depleted group and an antibiotic-depleted group receiving FMT from children with highly active brown adipose tissue. The groups were followed longitudinally, with fecal samples collected across timepoints and a cecal and serum sample collected at endpoint. An integrated multi-omic strategy was applied, combining i) 16S rRNA amplicon sequencing for diversity and compositional structure; ii) shotgun metagenomics for species-level and functional insights, and iii) mass spectrometry for targeted and untargeted metabolome profiling. The results obtained from each analysis were cross-referenced against a terminal phenotype panel collecting data - among others - on browning activity and glycemic responses, allowing each biological layer to be interpreted in the context of others. Analysis of the microbial community showed a consistent and pronounced collapse of diversity driven by antibiotic exposure, which was (partially) significantly recovered by the FMT procedure. This pattern was concordant between the 16S and the metagenomic dataset, and observed both at the within sample (alpha-diversity) and the between-sample (beta-diversity) level. From a taxonomic point of view, we could identify FMT-driven changes, namely the enrichment of Akkermansiaceae (Akkermansia muciniphila), Lachnospiraceae (Blautia producta) and Ruminococcaceae, while also revealing biologically informative limits of the model, i.e. the poor engraftment of a donor taxon such as Bifidobacterium, in a heterologous host. Interestingly, targeted (namely short-chain fatty acids, SCFAs) and untargeted metabolic profiling, as well as shotgun metagenomics, placed the FMT group closer to the antibiotic-depleted group, suggesting a more nuanced functional recovery compared to the compositional one. Integrating these data with the phenotypic database generated a shortlist of putative candidates, with hexanal being the most notable one, negatively correlated with browning activity. The fatty acid degradation pathway, identified by shotgun metagenomics, which ultimately leads - among others - to hexanal production, was also negatively associated with browning activity, providing a coherent mechanistic connection. Additionally, the branched-chain fatty acids isobutyrate and isovalerate were directly associated with impaired glucose tolerance. This project generated useful scientific results, showing how an integrated multi-omics framework can help disentangle complex interactions linking the gut microbiome to adipose and metabolic phenotypes in T2D and, thanks to the harmonization with the other RUs, provide actionable therapeutic leads. The results of this project have been presented, as part of the dissemination plan, to various congresses, including the Società Italiana di Diabetologia (SID) and the European Association for the Study of Diabetes (EASD) congresses.
Project details
Unibo Team Leader: Silvia Turroni
Unibo involved Department/s:
Dipartimento di Farmacia e Biotecnologie
Coordinator:
CNR - Consiglio Nazionale delle Ricerche(Italy)
Total Unibo Contribution: Euro (EUR) 46.603,00
Project Duration in months: 24
Start Date:
18/10/2023
End Date:
28/02/2026
