Interleukin 10 Restores Gastric Emptying, Electrical Activity, and Interstitial Cells of Cajal Networks in Diabetic Mice

Abstract

Background and Aims Gastroparesis is a complication of diabetes, characterized by delayed emptying of stomach contents and accompanied by early satiety, nausea, vomiting, and pain. No safe and reliable treatments are available. Interleukin 10 (IL10) activates the M2 cytoprotective phenotype of macrophages and induces expression of heme oxygenase 1 (HO1) protein. We investigated whether IL10 administration could improve gastric emptying and reverse the associated cellular and electrical abnormalities in diabetic mice. Methods Non-obese diabetic mice with delayed gastric emptying were given either IL10 (0.1-1μg, twice/day) or vehicle (controls). Stomach tissues were isolated, and sharp microelectrode recordings were made of the electrical activity in the gastric muscle layers. Changes to interstitial cells of Cajal (ICC), NADPH-diaphorase and levels and distribution of HO1 protein were determined by histochemical and imaging analyses of the same tissues. Results Gastric emptying remained delayed in vehicle-treated diabetic mice but returned to normal in mice given IL10 (n = 10 mice, P < 0.05). In mice given IL10, normalization of gastric emptying was associated with a membrane potential difference between the proximal and distal stomach and lower irregularity and higher frequency of slow-wave activity, particularly in the distal stomach. Levels of HO1 protein were higher in stomach tissues from mice given IL10, and ICC networks were more organized, better connected, and more evenly distributed compared with controls. Conclusions IL10 increases gastric emptying in diabetic mice and has therapeutic potential for patients with diabetic gastroparesis. This response is associated with up-regulation of HO1 and repair of connectivity of ICC networks.

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

“…At 17 weeks of age, half-times (T 1/2 ) of solid GE 22 were significantly shorter in Lepr db/db mice whereas controls had T 1/2 values highly similar to results previously obtained in nondiabetic NOD mice 28 (Figure 1 A ). In Lepr db/db mice, GE remained accelerated at least until 50 weeks of age (T 1/2 = 60±6 min; mean±S.E.M.…”

“…28 Although oxidative stress determined by measuring gastric 8-OHdG and circulating MDA was elevated in Lepr db/db mice, MDA concentrations were lower than the levels reported in the presence of ICC depletion and delayed GE. 28 Thus, the oxidative stress observed in our cohort of Lepr db/db mice was likely insufficient to precipitate ICC loss. By the same token, the similarly modest increases seen in the Sdhc -deficient mice were unlikely to underlie the ICC loss in that model.…”

“…We also determined oxidative stress, a hallmark of diabetes mellitus, which contributes to ICC depletion in type 1 diabetic NOD mice. 28 Serum malondialdehyde (MDA), a product of polyunsaturated fatty acid peroxidation, 28 and levels in the gastric musculature of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of oxidative DNA damage, were also significantly increased (Supplementary Figure S2 B ). These results indicate that Lepr db/db mice are a suitable model to study the ICC phenotype and gastric functions in hyperinsulinemic type 2 diabetes.…”

“…In Lepr db/db mice, ICCs increased despite reduced KITL and increased oxidative stress, i.e., factors contributing to ICC depletion in type 1 diabetes. 15,28 Both Lepr db/db and Kit K641E/+ mice showed increased ERK1-ERK2 phosphorylation and upregulated ETV1 and KIT proteins. The increase in ICCs and ICC-SCs and the activation of the ERK-ETV1-KIT pathway were faithfully reproduced by in-vitro exposure of immortalized and primary ICCs, cultured ICC-SCs, as well as mouse and human gastric tunica muscularis organotypic cultures to glucose concentrations occurring in Lepr db/db mice, demonstrating a stimulatory effect of elevated glucose on ICCs.…”

“…22 Electrical slow waves were recorded by intracellular techniques. 4,11,14,28 Spontaneous and carbachol-stimulated phasic contractile activity in circular antral muscles was studied by isometric force measurements using standard techniques (Supplementary Methods). …”