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Novel insulin/GIP co‐producing cell lines provide unexpected insights into Gut K‐cell function in vivo
Author(s) -
Ramshur Erin B.,
Rull Teena R.,
Wice Burton M.
Publication year - 2002
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.10139
Subject(s) - glucokinase , insulin , biology , cell culture , enteroendocrine cell , transfection , medicine , population , endocrinology , proinsulin , microbiology and biotechnology , hormone , endocrine system , demography , sociology , genetics
Enteroendocrine (EE) cells represent complex, rare, and diffusely‐distributed intestinal epithelial cells making them difficult to study in vivo. A specific sub‐population of EE cells called Gut K‐cells produces and secretes glucose‐dependent insulinotropic peptide (GIP), a hormone important for glucose homeostasis. The factors that regulate hormone production and secretion, as well as the timing of peptide release, are remarkably similar for K‐cells and islet β‐cells suggesting engineering insulin production by K‐cells is a potential gene therapeutic strategy to treat diabetes. K‐cell lines could be used to study the feasibility of this potential therapy and to understand Gut K‐cell physiology in general. Heterogeneous STC‐1 cells were transfected with a plasmid (pGIP/Neo) encoding neomycin phosphotransferase, driven by the GIP promoter‐only cells in which the GIP promoter was active survived genetic selection. Additional clones expressing pGIP/Neo plus a GIP promoter/insulin transgene were isolated—only doubly transfected cells produced preproinsulin mRNA. Bioactive insulin was stored and then released following stimulation with arginine, peptones, and bombesin—physiological GIP secretagogues. Like K‐cells in vivo, the GIP/insulin‐producing cells express the critical glucose sensing enzyme, glucokinase. However, glucose did not regulate insulin or GIP secretion or mRNA levels. Conversely, glyceraldehyde and methyl‐pyruvate were secretagogues, indicating cells depolarized in response to changes in intracellular metabolite levels. Potassium channel opening drugs and sulphonylureas had little effect on insulin secretion by K‐cells. The K‐cell lines also express relatively low levels of Kir 6.1, Kir 6.2, SUR1, and SUR2 suggesting secretion is independent of K ATP channels. These results provided unexpected insights into K‐cell physiology and our experimental strategy could be easily modified to isolate/characterize additional EE cell populations. © 2002 Wiley‐Liss, Inc.