Gene expression profiling of L cells. Gene expression profiling of L cells

Objectives: To profile the enteroendocrine L cell transcriptome under several conditions to enable therapeutic strategies targeting these cells. We investigate the differences in L cells between regions of the gastrointestinal tract (ileum and colon), and how this relates to the surrounding epithelium. We also investigated the changes which occur following a high fat diet (HFD) and development of insulin resistance or following vertical sleeve gastrectomy (VSG). Methods: We developed the gcg-DTR-eGFP mouse line to enable the FACS purification of enteroendocrine L cells, gcg expressing cells, from the ileum and colon of 5 mice which developed insulin resistance following HFD and 5 chow controls and from 7 mice which showed improved glucose tolerance following VSG, alongside 7 glucose intolerant sham controls. Epithelial cells were also purified from the VSG and sham mice. Transcriptomic sequencing of these cells and analysis of differentially expressed genes was used to determine differences in L cells between tissues and with HFD or VSG, and primary intestinal cultures were used to confirm the observed tissue differences.Results: HFD and the development of insulin resistance led to a small change in the L cell transcriptome in immune related genes, whereas no differences were seen after VSG. In contrast, large differences were observed between ileal and colonic L cells due to differential expression of genes involved in nutrient transport and metabolism, recapitulating changes in the surrounding epithelium and leading to different GLP-1 responses between tissues. Conclusions: The L cell transcriptome differs along the length of the gastrointestinal tract, so L cells from different regions express different hormonal profiles and exhibit differing sensitivities to stimulants of GLP-1 secretion. This will have consequences on the role of L cells in post-prandial glucose homeostasis and for anti-diabetic drug development.