Hyperglycemia Increases Interstitial Cells of Cajal via MAPK1 and MAPK3 Signaling to ETV1 and KIT, Leading to Rapid Gastric Emptying

Abstract

BACKGROUND & AIMS Depletion of interstitial cells of Cajal (ICCs) is common in diabetic gastroparesis. However, in approximately 20% of patients with diabetes, gastric emptying (GE) is accelerated. GE is also faster in obese individuals, and is associated with increased blood levels of glucose in patients with type 2 diabetes. To understand the fate of ICCs in hyperinsulinemic, hyperglycemic states characterized by rapid GE, we studied mice with mutation of the leptin receptor (Leprdb/db), which in our colony had accelerated GE. We also investigated hyperglycemia-induced signaling in the ICC lineage and ICC dependence on glucose oxidative metabolism in mice with disruption of the succinate dehydrogenase complex, subunit C gene (Sdhc). METHODS Mice were given breath tests to analyze GE of solids. ICCs were studied by flow cytometry, intracellular electrophysiology, isometric contractility measurement, reverse transcription PCR, immunoblot, immunohistochemistry, ELISAs, and metabolite assays; cells and tissues were manipulated pharmacologically and by RNA interference. Viable cell counts, proliferation, and apoptosis were determined by methyltetrazolium, Ki-67, proliferating cell nuclear antigen, bromodeoxyuridine, and caspase-Glo 3/7 assays. Sdhc was disrupted in 2 different strains of mice via cre recombinase. RESULTS In obese, hyperglycemic, hyperinsulinemic female Leprdb/db mice, GE was accelerated and gastric ICC and phasic cholinergic responses were increased. Female KitK641E/+ mice, which have genetically induced hyperplasia of ICCs, also had accelerated GE. In isolated cells of the ICC lineage and gastric organotypic cultures, hyperglycemia stimulated proliferation by mitogen-activated protein kinase 1 (MAPK1)- and MAPK3-dependent stabilization of ets variant 1 (ETV1)—a master transcription factor for ICCs—and consequent upregulation of KIT proto-oncogene receptor tyrosine kinase (KIT). Opposite changes occurred in mice with disruption of Sdhc. CONCLUSIONS Hyperglycemia increases ICCs via oxidative metabolism-dependent, MAPK1- and MAKP3-mediated stabilization of ETV1 and increased expression of KIT, causing rapid gastric emptying. Increases in ICCs might contribute to the acceleration in GE observed in some patients with diabetes.

Bone marrow‐derived interstitial cells of cajal are increased by electroacupuncture in the colon of diabetic mice

“…Hayashi et al . reported that increased ICC are dependent on the activation of the ERK‐ETV1‐KIT pathway . Another report confirmed that c‐Jun can enhance the transcriptional activity of ETV1 .…”

High temporal resolution gastric emptying breath tests in mice

“…Measuring 13 C enrichment in exhaled breath samples provides a robust and reproducible measure of gastric emptying that has been extensively validated. Our research group has used manual breath collection and 13 C analysis by isotope gas chromatography, automated sampling and 13 C analysis by infrared spectroscopy, and most recently by OA‐ICOS . As described previously, the latter system allows for simultaneous measurements in 12 animals with approximately 15 distinct measurements after stabilization every 5 minutes for high temporal resolution of a 4‐6 h gastric emptying test.…”

“…Our research group has used this test to evaluate gastric emptying in mice in several disease models, most commonly diabetic gastroparesis . Utilizing off axis‐ integrated cavity output spectroscopy (OA‐ICOS) with a multiple input unit to measure 13 CO 2 , mitigates the need to concentrate air samples, thus increasing temporal resolution and throughput of data.…”

Slowed gastric emptying and improved oral glucose tolerance produced by a nanomolar‐potency inhibitor of calcium‐activated chloride channel TMEM16A

“…Obesity is associated with accelerated gastric emptying (35), with up to 20% of patients with diabetes mellitus having rapid gastric emptying, although delayed gastric emptying is more common in the diabetic population (36,37). A recent study in mice showed that hyperglycemia stimulates ICC proliferation in vitro and that obese, hyperglycemic, hyperinsulinemic db/db mice have accelerated gastric emptying, increased gastric slow wave frequency, and phasic cholinergic responses (38). Accelerated gastric emptying is thus thought to contribute to impaired glucose tolerance and weight gain in obesity.…”