The combination of high-fat diet-induced obesity and chronic ulcerative colitis reciprocally exacerbates adipose tissue and colon inflammation

Abstract

Background: This study evaluated the relationship between ulcerative colitis and obesity, which are both chronic diseases characterized by inflammation and increases in immune cells and pro-inflammatory cytokines.

Methods: Mice with chronic ulcerative colitis induced by 2 cycles of dextran sodium sulfate (DSS) in the first and fourth week of the experiment were fed a high-fat diet (HFD) to induce obesity by 8 weeks. The animals were divided into 4 \ groups (control, colitis, HFD and colitis + HFD).

Results: Obesity alone did not raise histopathology scores, but the combination of obesity and colitis worsened the scores in the colon compared to colitis group. Despite the reduction in weight gain, there was increased inflammatory infiltrate in both the colon and visceral adipose tissue of colitis + HFD mice due to increased infiltration of macrophages, neutrophils and lymphocytes. Intravital microscopy of VAT microvasculature showed an increase in leukocyte adhesion and rolling and overexpression of adhesion molecules compared to other groups. Moreover, circulating lymphocytes, monocytes and neutrophils in the spleen and cecal lymph nodes were increased in the colitis + HFD group.

Conclusion: Our results demonstrated the relationship between ulcerative colitis and obesity as aggravating factors for each disease, with increased inflammation in the colon and adipose tissue and systemic alterations observed in the spleen, lymph nodes and bloodstream.

Figure 1

Histopathological scores (A) and components: inflammatory infiltrate (B), muscularis mucosa thickness (C), mucosa general architecture (D) and goblet cell depletion (E) of mice from control and HFD groups (receiving standard chow or HFD, respectively) or colitis and colitis + HFD groups (receiving the respective diets and treated with 2 cycles of DSS [3%] to induce ulcerative colitis). Bars indicate the means, and vertical lines indicate the standard errors. n = 4-5 per group. Statistical tests: One-way ANOVA + Newman-Keuls post-test. Different letters indicate p < 0.05.

Figure 2

Percentage of leukocyte subtypes in the colon lamina propria. Neutrophils (A), regulatory T lymphocytes (B), total macrophages and monocytes (C), activated macrophages (D), B lymphocytes (E), activated B lymphocytes (F), CD4+ T cells (G), activated CD4+ T cells (H), CD8+ T cells (I), activated CD8+ T cells (J) of mice from control and HFD groups (receiving standard chow or HFD, respectively) or colitis and colitis + HFD groups (receiving the respective diets and treated with 2 cycles of DSS [3%] to induce ulcerative colitis). Bars indicate the means, and vertical lines indicate the standard errors. n = 5 per group. Statistical tests: One-way ANOVA + Newman-Keuls post-test. Different letters indicate p < 0.05.

Figure 3

Lamina propria cytokine and chemokine concentrations. TNFa (A), IL6 (B), IL4 (C), IL10 (D), IFN-y (E) and MCP1/CCL2 (F) of mice from control and HFD groups (receiving standard chow or HFD, respectively) or colitis and colitis + HFD groups (receiving the respective diets and treated with 2 cycles of DSS [3%] to induce ulcerative colitis). Bars indicate the means, and vertical lines indicate the standard errors. n = 5 per group. Statistical tests: One-way ANOVA + Newman-Keuls post-test. Different letters indicate p < 0.05.

Figure 4

Expression of TLR4 (A) and Ob-R (B) in the colon mucosa of mice from control and HFD groups (receiving standard chow or HFD, respectively) or colitis and colitis + HFD groups (receiving the respective diets and treated with 2 cycles of DSS [3%] to induce ulcerative colitis). Bars indicate the means, and vertical lines the indicate standard errors. n = 5 per group. Statistical tests: One-way ANOVA + Newman-Keuls post-test. Different letters indicate p < 0.05.

Figure 5

Percentage of epididymal adipose tissue in relation to body (A), adipocyte area (B) and average of number of crown-like structures (C) of mice from control and HFD groups (receiving standard chow or HFD, respectively) or colitis and colitis + HFD groups (receiving the respective diets and treated with 2 cycles of DSS [3%] to induce ulcerative colitis). Bars indicate the means, and vertical lines indicate standard error. n = 5 per group. Statistical tests: One-way ANOVA + Newman-Keuls post-test. Different letters indicate p < 0.05. n = 12-14 per group in (A) and (C) and 4-5 per group in (B).

Figure 6

Macrophages and monocytes (A), activated macrophages (B), neutrophils (C), regulatory T lymphocytes (D), total (E) and activated (F) CD4+ T cells, total (G) and activated (H) CD8+ T cells, total (I) and activated (J) B cells, activated cytotoxic T lymphocytes (H), total (I) and activated B cells (J) of mice from control and HFD groups (receiving standard chow or HFD, respectively) or colitis and colitis + HFD groups (receiving the respective diets and treated with 2 cycles of DSS [3%] to induce ulcerative colitis). Bars indicate the means, and vertical lines indicate the standard errors. n = 5 per group. Test: One-way ANOVA + Newman-Keuls post-test. Different indicate p < 0.05.

Figure 7

Expression of TLR4 (A), MCP1/CCL2 (B), TNFα (C) and IL6 (D) in adipose tissue of mice from control and HFD groups (receiving standard chow or HFD, respectively) or colitis and colitis + HFD groups (receiving the respective diets and treated with 2 cycles of DSS [3%] to induce ulcerative colitis). Bars indicate the means, and vertical lines indicate the standard errors. n = 5 per group. Statistical tests: One-way ANOVA + Newman-Keuls post-test. Different letters indicate p < 0.05.

Figure 8

Serum levels and adipose tissue expression of leptin (A, B), resistin (C,D) and adiponectin (E,F) of mice from control and HFD groups (receiving standard chow or HFD, respectively) or colitis and colitis + HFD groups (receiving the respective diets and treated with 2 cycles of DSS [3%] to induce ulcerative colitis). Bars indicate the means, and vertical lines indicate the standard errors. Statistical tests: One-way ANOVA + Newman-Keuls post-test. Different letters indicate p < 0.05. n = 5 per group.

Figure 9

Intravital microscopy showing the rolling (A) and adhesion (B) of leukocytes on microvasculature of epididymal adipose tissue and ICAM (C) and VCAM-1 (D) expression in control and HFD groups (receiving standard chow or HFD, respectively) or colitis and colitis + HFD groups (receiving the respective diets and treated with 2 cycles of DSS [3%] to induce ulcerative colitis). Bars indicate the means, and vertical lines indicate standard error. n = 5 per group. Statistical tests: One-way ANOVA + Newman-Keuls post-test. Different letters indicate p < 0.05.n = 6-8 per group.