Introduction:
Enteroendocrine cells (EEC) are a rare population of hormone-producing mucosal cells within the gastrointestinal (GI) tract that control feeding behaviour, glucose homeostasis and fat metabolism [1], making them excellent targets for the treatment of type 2 diabetes and obesity. EECs release metabolically important hormones upon exposure to dietary and microbial cues within the gut [2]. High fat diet (HFD) drives changes in EEC biology [3], microbial diversity [4], and the GI cellular landscape. How diet-induced gut dysbiosis contributes to these changes remains unclear. To interrogate the role of diet and the microbiome on gut mucosal cell biology, we performed single-cell transcriptomic analysis to understand changes in cellular identity and function under obesogenic conditions.
Method:
Male 6-week old C57BL/6J mice were placed on a low fat diet (LFD) or HFD in the presence or absence of a broad-spectrum antibiotic cocktail (ABX) to deplete gut microbiota for 8 weeks. Metabolic status was assessed with glucose tolerance tests at the beginning and end of the diet, along with weight gain, food consumption and fasting blood glucose. Fecal pellets and serum were also routinely collected throughout the diet regime. After 8 weeks, the mucosal cells were isolated from all regions of mouse intestine and enriched for EECs using fluorescence-activated cell sorting. Single-cell analysis was performed using Chromium Fixed RNA Profiling kit (10X Genomics) and sequenced on a NovaSeq X chemistry (Illumina). Post-analyses were performed using Seurat (version 5.0.1) in R.
Key findings:
An 8 week HFD induced obesity and metabolic dysfunction which was prevented in mice treated with ABX. Single cell transcriptomics analysis showed significant diet-driven changes in the global proportion of different mucosal cell types across all regions of the GI tract. Analysis of the EEC lineage revealed HFD-driven changes in the proportion of progenitors and serotonergic EEC types compared to LFD. These changes also appear to be dependent on the presence of the gut microbiome, as HFD-ABX and LFD-ABX mice have a vastly different EEC signatures compared to non-ABX mice.
Conclusions:
An obesogenic diet shifts the global landscape of the intestinal mucosa by altering its cellular composition and diversity. Single cell transcriptomics analysis also reveals that the EEC lineage is highly dependent on the presence of the gut microbiome, suggesting that it may play an essential role in the development of obesity and type 2 diabetes. Further analysis is being undertaken to assess transcriptional changes in cell biology across EEC subtypes.