Regulation of type 2 diabetes by helminth-induced Th2 immune response

Abstract

Helminth-induced type 2 cytokines increase the number of regulatory T cells and alternatively activated macrophages, resulting in modulation of the host-immune system. Studies on these parasite-induced immunoregulatory mechanisms might contribute to the development of new therapies for inflammatory diseases, including type 2 diabetes (T2D). Previous studies have suggested that progression of obesity-associated metabolic abnormalities is under pathophysiological control of CD4+ T cells. Glucose absorption through the intestinal epithelium reduced after infection in a STAT-6-dependent manner. In this study, we investigated whether infection with the gastrointestinal nematode parasite Heligmosomoides polygyrus (Hp) can modulate T2D-associated pathology in a mouse model (KK-Ay/TaJcl). KK-Ay/TaJcl mice were inoculated with infective third-stage Hp larvae and studied at Day 8 following infection. Uninfected KK-Ay/TaJcl mice showed high blood glucose levels even 120 min after administration of glucose by IP injection. However, it was significantly improved in the infected group. HOMA-IR, fat accumulation and FAS gene expression in the liver were significantly decreased by Hp infection. GLUT2 gene expression in this group was significantly lower than that in the uninfected diabetic mice, which might be related to the decrease in glucose absorption in the parasite-infected intestine. In conclusion, helminth-induced type 2 immune responses might contribute to T2D disease control.

Fig. 1.

The KK-Ay/TaJcl mouse strain develops obesity and insulin resistance at early stages. (A) The KKAy/TaJcl mice increased their body weight. The mice were divided into two groups at 6 weeks of age, and one group was infected with Hp and investigated on day 8 after infection. (B) Blood glucose levels at the time of infection. (C) IPGTT was significantly decreased in the Hp-infected mice. (D) Insulin resistance index (HOMA-IR) was recovered in the Hp-infected KK-Ay/TaJcl mice. *P<0.05; **P<0.01; ***P<0.001. N=4. We performed two independent experiments with similar results.

Fig. 2.

Representative liver from uninfected (A) and Hp-infected (D) mice (12 weeks old, day 8 after infection). H&E-stained histology (B: uninfected, E: infected) and Oil-O-Red staining (C: uninfected, F: infected) for assessment of fat accumulation. All images of BCEF were acquired at 200× magnification, and the images are representative for more than four mice. FAS gene expression in the liver (G), GPT (ALT) in serum (H) and total lipid content in the liver (I). *P<0.05, N≥4.

Fig. 3.

Real-time PCR analysis of IL-4 (A), IL-13 (B), IL-10 (C), ARG1 (D), FIZZ1 (E) and YM1 (F) gene expression in the small intestine from uninfected control mice (white bars) and 8 days after Hp infection (black bars) of the study mice (12 weeks old, N=5). All data are expressed in relative units compared with uninfected mice (controls). **P<0.01; ***P<0.001. Data are shown as means ± SE and represent two independent experiments with similar results. (G) Immunofluorescence staining with anti-CD206 (green) and anti-F4/80 (red) antibodies of a section of the small intestine. The observation that CD206+ cells were F4/80+ is consistent with AAMacs phenotype. Images left to right: merged FITC and Alexa647, FITC only, and Alexa647 only. All images are of 4-µm-thick sections at 100× magnification, and images represent submucosa obtained from more than five mice.

Fig. 4.

Representative H&E stained sections in the small intestine (12 weeks old, control: top and day 8 after Hp infection: bottom). All images are 7-µm-thick sections at 100× (left) and 600× (right) magnification. Enlarged regions of the submucosa, indicated by a dashed rectangle, are shown in the left panel.

Fig. 5.

(A) Real-time PCR analysis of SGLT1 in whole tissue of the small intestine. (B) Real-time PCR analysis of GLUT2 in whole tissue of the small intestine. (C) Real-time PCR analysis of GLUT2 in the epithelium of the small intestine with LCM. (D) Immunofluorescence staining of a section of the small intestine from control and Hp-infected mice (12 weeks old, day 8 after infection) with anti-GLUT2 antibody. *P<0.05; ***P<0.001. N≥4. Data are shown as means ± SE and represent two independent experiments with similar results.