Background & AimsDiabetic gastroparesis is associated with changes in interstitial cells of Cajal (ICC), neurons, and smooth muscle cells in both animal models and humans. Macrophages appear to be critical to the development of cellular damage that leads to delayed gastric emptying (GE), but the mechanisms involved are not well understood. Csf1op/op (Op/Op) mice lack biologically active Csf1 (macrophage colony stimulating factor), resulting in the absence of Csf1-dependent tissue macrophages. We used Csf1op/op mice to determine the role of macrophages in the development of delayed GE.MethodsAnimals were injected with streptozotocin to make them diabetic. GE was determined weekly. Immunohistochemistry was used to identify macrophages and ICC networks in the gastric muscular layers. Oxidative stress was measured by serum malondialdehyde (MDA) levels. Quantitative reverse-transcription polymerase chain reaction was used to measure levels of mRNA.ResultsCsf1op/op mice had normal ICC. With onset of diabetes both Csf1op/op and wild-type Csf1+/+ mice developed increased levels of oxidative stress (75.8 ± 9.1 and 41.2 ± 13.6 nmol/mL MDA, respectively). Wild-type Csf1+/+ mice developed delayed GE after the onset of diabetes (4 of 13) whereas no diabetic Csf1op/op mouse developed delayed GE (0 of 15, P = .035). The ICC were disrupted in diabetic wild-type Csf1+/+ mice with delayed GE but remained normal in diabetic Csf1op/op mice.ConclusionsCellular injury and development of delayed GE in diabetes requires the presence of muscle layer macrophages. Targeting macrophages may be an effective therapeutic option to prevent cellular damage and development of delayed GE in diabetes.

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.

Gastric emptying studies in mice have been limited by the inability to follow gastric emptying changes in the same animal since the most commonly used techniques require killing of the animals and postmortem recovery of the meal(1,2). This approach prevents longitudinal studies to determine changes in gastric emptying with age and progression of disease. The commonly used [(13)C]-octanoic acid breath test for humans(3) has been modified for use in mice(4-6) and rats(7) and we previously showed that this test is reliable and responsive to changes in gastric emptying in response to drugs and during diabetic disease progression(8). In this video presentation the principle and practical implementation of this modified test is explained. As in the previous study, NOD LtJ mice are used, a model of type 1 diabetes(9). A proportion of these mice develop the symptoms of gastroparesis, a complication of diabetes characterized by delayed gastric emptying without mechanical obstruction of the stomach(10). This paper demonstrates how to train the mice for testing, how to prepare the test meal and obtain 4 hr gastric emptying data and how to analyze the obtained data. The carbon isotope analyzer used in the present study is suitable for the automatic sampling of the air samples from up to 12 mice at the same time. This technique allows the longitudinal follow-up of gastric emptying from larger groups of mice with diabetes or other long-standing diseases.