Nutrient sensing by absorptive and secretory progenies of small intestinal stem cells

Abstract

The apical membranes of intestinal cells are exposed to luminal food contents, and the cells' ability to perceive and adapt to these environmental cues is critical so that appropriate endocrine signals are released and that specific types as well as numbers of enzymes and transporters are synthesized to match the variety and fluctuating concentrations of dietary constituents. Since enteroendocrine and enterocyte cells represent secretory and absorptive lineages, respectively, and have previously been shown to demonstrate nutrient sensing capacity, we tested the hypothesis that progenitor intestinal stem cells (ISCs) possess nutrient sensing ability which is subsequently inherited by their progenies. We directed via modulators of Wnt and Notch signaling, the primary three‐dimensional culture of mouse intestinal crypts into ISC, enterocyte, goblet or Paneth organoids. Each specialized organoid contained mostly a single specific cell type comprised primarily of ISC (~90%), enterocytes (~90%), goblet (~85%) or Paneth cells (~65%) at relative proportions much higher than in situ as determined by mRNA expression and immunocytochemical detection of cell type biomarkers. We identified nutrient sensing cell type(s) by examining responses of fructose responsive genes after a fructose challenge. Typical (control) organoids comprised of all cell types as well as enterocyte, but not ISC, organoids responded specifically to fructose without altering expression of nonfructolytic genes. Surprisingly, Paneth and goblet organoids responded dramatically to fructose, suggesting that each of the three major secretory cell types has nutrient sensing ability. Responses of all fructose‐sensing organoids increased with higher fructose concentrations. Typical organoids generated from fructose transporter GLUT5‐KO and fructokinase KHK‐KO mice did not respond to fructose, suggesting that transport and metabolism of fructose are required for fructose sensing, and providing a likely mechanism underlying absence of fructose sensing in ISCs that do not significantly express GLUT5 and KHK. More mature absorptive and secretory organoids tended to exhibit stronger fructose responses, suggesting that sensing improves with increased differentiation. Remarkably, mature enterocytes, upon forced dedifferentiation to reacquire ISC characteristics, retained fructose sensing ability. Fructose response was independent of either Wnt or Notch modulators used to direct organoid formation, and of glucose concentrations in the organoid culture medium. Using an innovative experimental approach, we determined that nutrient sensing is likely repressed in progenitor ISCs, then derepressed prior to specification between absorptive and secretory lineages. This study increases our understanding of the role of differentiation in regulating nutrient sensing during development of intestinal epithelial cells.Support or Funding InformationSupported by NSF Grants No. IOS‐1121049 and 1456673 (RPF). RPF also received support from NIH R01‐DK‐102934 (NG).