Development of a Primary Human Intestinal Epithelium Enriched in L-Cells for Assay of GLP-1 Secretion

Type 2 diabetes mellitus is a chronic disease associated with obesity and dysregulated human feeding behavior. The hormone glucagon-like peptide 1 (GLP-1), a critical regulator of body weight, food intake, and blood glucose levels, is secreted by enteroendocrine L-cells. The paucity of L-cells in primary intestinal cell cultures including organoids and monolayers has made assays of GLP-1 secretion from primary human cells challenging. In the current paper, an analytical assay pipeline consisting of an optimized human intestinal tissue construct enriched in L-cells paired with standard antibody-based GLP-1 assays was developed to screen compounds for the development of pharmaceuticals to modulate L-cell signaling. The addition of the serotonin receptor agonist Bimu 8, optimization of R-spondin and Noggin concentrations, and utilization of vasoactive intestinal peptide (VIP) increased the density of L-cells in a primary human colonic epithelial monolayer. Additionally, the incorporation of an air-liquid interface culture format increased the L-cell number so that the signal-to-noise ratio of conventional enzyme-linked immunoassays could be used to monitor GLP-1 secretion in compound screens. To demonstrate the utility of the optimized analytical method, 21 types of beverage sweeteners were screened for their ability to stimulate GLP-1 secretion. Stevioside and cyclamate were found to be the most potent inducers of GLP-1 secretion. This platform enables the quantification of GLP-1 secretion from human primary L-cells and will have broad application in understanding L-cell formation and physiology and will improve the identification of modulators of human feeding behavior.