Sarah McCaskey

Dietary Fish Oil Alters T Lymphocyte Cell Populations and Exacerbates Disease in a Mouse Model of Inflammatory Colitis

Inflammatory bowel diseases (IBD) increase the risk of developing colorectal cancer. Dietary components that reduce inflammation are associated with lower cancer risk. The long-chain omega-3 fatty acid docosahexaenoic acid (DHA) is present in fish oil and has potent anti-inflammatory properties. The objective of this study is to determine whether dietary fish oil enriched with DHA (DFO) could reduce experimentally induced colitis and colon cancer risk in a mouse model. When SMAD3-/- mice are exposed to Helicobacter hepaticus, mild colitis is observed 4 weeks postinfection. Mice were fed isocaloric diets modified to include corn oil, safflower oil, or DFO (doses ranging from 0.75% to 6.00%) as the fatty acid source for 8 weeks. Mice were gavaged with H. hepaticus; DFO feeding was continued; and mice were sacrificed 4 weeks after infection. The colon and cecum were collected for histopathology. Spleens and mesenteric lymph nodes were collected and analyzed for T-cell populations using flow cytometry. Contrary to expectations, DFO induced severe colitis and adenocarcinoma formation. DFO consumption was associated with decreased CD8(+) cell frequency and diminished CD69 expression on CD4(+) and CD8(+) T-cell populations. Mice consuming DFO also exhibited higher FoxP3(+) CD25(+) CD4(+) T regulatory cell frequency, FoxP3 expression, and altered L-selectin expression during infection. We concluded that DFO-fed mice may be less equipped to mount a successful response to H. hepaticus infection, increasing colon cancer risk. These results support the need to establish a tolerable upper limit for DHA intake particularly in the context of chronic inflammatory conditions such as IBD.

Adipokines and obesity are associated with colorectal polyps in adult males: A cross-sectional study

Background Obesity increases the risk of colon cancer. It is also known that most colorectal cancers develop from adenomatous polyps. However, the effects of obesity and adipokines on colonic polyp formation are unknown. Methods To determine if BMI, waist circumference or adipokines are associated with colon polyps in males, 126 asymptomatic men (48–65 yr) were recruited at time of colonoscopy, and anthropometric measures as well as blood were collected. Odds ratios were determined using polytomous logistic regression for polyp number (0 or ≥3) and polyp type (no polyp, hyperplastic polyp, tubular adenoma). Results 41% of the men in our study were obese (BMI ≥30). The odds of an obese individual having ≥3 polyps was 6.5 (CI: 1.3–33.0) times greater than those of a lean (BMI<25) individual. Additionally, relative to lean individuals, obese individuals were 7.8 (CI: 2.0–30.8) times more likely to have a tubular adenoma than no polyp. As BMI category increased, participants were 2.9 (CI: 1.5–5.4) times more likely to have a tubular adenoma than no polyps. Serum leptin, IP-10 and TNF-α were significantly associated with tubular adenoma presence. Serum leptin and IP-10 were significantly associated with increased likelihood of ≥3 polyps, and TNF-α showed a trend (p = 0.09). Conclusions Obese men are more likely to have at least three polyps and adenomas. This cross-sectional study provides evidence that colonoscopy should be recommended for obese, white males.

Supplementation with Galacto-Oligosaccharides Increases the Percentage of NK Cells and Reduces Colitis Severity in Smad3-Deficient Mice

The gut microbiota plays an essential role in intestinal immunity. Prebiotics, including galacto-oligosaccharides (GOS), are fermentable fibers that beneficially affect the host by stimulating the growth of specific microbial populations. We investigated the effect of GOS on colitis development and on immune variables in Smad3-deficient mice treated with the pathogen Helicobacter hepaticus. Mice were supplemented daily with 5000 mg GOS/kg body weight 2 wk prior to infection and 4 wk postinfection, a time period during which colitis severity peaks in this model. Mice (n = 4-8/treatment at each time) were killed preinfection (0 d) and at 3, 7, and 28 d postinfection to evaluate immune variables in the spleen and in mesenteric lymph nodes (MsLN) by flow cytometry. Colon and cecum samples were collected for histopathologic analysis. Fecal pellets (n = 8-9/treatment) were collected prior to infection to measure relative changes in Bifidobacterium ssp. and Lactobacillum ssp. by real-time PCR. GOS significantly reduced colitis severity in response to H. hepaticus (P < 0.0001). This was associated with a significant increase in the percentage of NK cells in the spleen (P < 0.001) and in MsLN (P < 0.001) at 3 d postinfection and a 1.5-fold increase in fecal Bifidobacterium ssp. (P = 0.003). GOS stimulated NK expression of CCR9, a chemokine receptor involved in lymphocyte trafficking to the gut preinfection (0 d) in the blood (P = 0.02), spleen (P = 0.033), and MsLN (P = 0.017). In addition, GOS stimulated colonic IL-15 production 3 d postinfection (P < 0.001). These data suggest that GOS reduces colitis by modulating the function and trafficking of NK cells and may provide a novel therapeutic strategy for individuals with inflammatory bowel disease.

Curcumin and docosahexaenoic acid block insulin-induced colon carcinoma cell proliferation☆

Diets high in fish and curcumin are associated with a decreased risk of CRC. Insulin resistance and obesity are associated with increased CRC risk and higher reoccurrence rates. We utilized cell culture to determine if dietary compounds could reduce insulin-induced cell proliferation comparing the response in normal and metastatic colon epithelial cells. We treated model normal murine colon epithelial cells (YAMC) and adenocarcinoma cells (MC38) with docosahexaenoic acid (DHA) or curcumin alone and then co-treatments of the diet-derived compound and insulin were combined. Cell proliferation was stimulated with insulin (1 ug/mL) to model insulin resistance in obesity. Despite the presence of insulin, proliferation was reduced in the MC38 cells treated with 10 μM curcumin (p<0.001) and 50 μM DHA (p<0.001). Insulin stimulated MAPK and MEK phosphorylation was inhibited by DHA and curcumin in MC38 cancer cells. Here we show that curcumin and DHA can block insulin-induced colon cancer cell proliferation in vitro via a MEK mediated mechanism.

Association of Insulin-Related Serum Factors with Colorectal Polyp Number and Type in Adult Males

Background: Dysregulated insulin signaling is thought to contribute to cancer risk. Methods: To determine if insulin-related serum factors are associated with colon polyps, 126 asymptomatic men (48–65 years) were recruited at colonoscopy. Blood was collected. Odds ratios were determined using polytomous logistic regression for polyp number and type. Results: Males with serum C-peptide concentration >3.3 ng/mL were 3.8 times more likely to have an adenoma relative to no polyp than those with C-peptide ≤1.8 ng/mL. As C-peptide tertile increased, an individual was 2 times more likely to have an adenoma (P = 0.01) than no polyp. There were no associations between insulin-like growth factor or its binding proteins with polyp number or type. Males with soluble receptor for advanced glycation end products (sRAGE) concentration >120.4 pg/mL were 0.25 times less likely to have ≥3 polyps relative to no polyps compared with males with sRAGE ≤94.5 pg/mL. For each increase in sRAGE tertile, a man was 0.5 times less likely to have ≥3 polyps than no polyps (P = 0.03). Compared with males with a serum vascular endothelial growth factor (VEGF) concentration ≤104.7 pg/mL, males with a serum VEGF concentration >184.2 pg/mL were 3.4 times more likely to have ≥3 polyps relative to no polyps. As the VEGF tertile increased, a man was 1.9 times more likely to have ≥3 polyps than no polyps (P = 0.049). Conclusions: Serum concentrations of C-peptide, sRAGE, and VEGF may indicate which men could benefit most from colonoscopy. Impact: Identification of biomarkers could reduce medical costs through the elimination of colonoscopies on low-risk individuals. Cancer Epidemiol Biomarkers Prev; 23(9); 1843–51. ©2014 AACR.

Differential effects of energy balance on experimentally-induced colitis

AIM To characterize the influence of diet-induced changes in body fat on colitis severity in SMAD3-/- mice. METHODS SMAD3-/- mice (6-8 wk of age) were randomly assigned to receive a calorie restricted (30% of control; CR), control (CON), or high fat (HF) diet for 20 wk and were gavaged with sterile broth or with Helicobacter hepaticus (H. hepaticus) to induce colitis. Four weeks after infection, mice were sacrificed and the cecum and colons were processed for histological evaluation. RESULTS Dietary treatment significantly influenced body composition prior to infection (P < 0.05), with CR mice having less (14% ± 2%) and HF-fed mice more body fat (32% ± 7%) compared to controls (22% ± 4%). Differences in body composition were associated with alterations in plasma levels of leptin (HF > CON > CR) and adiponectin (CON > HF ≥ CR) (P < 0.05). There were no significant differences in colitis scores between CON and HF-fed mice 4 wk post-infection. Consistent with this, differences in proliferation and inflammation markers (COX-2, iNOS), and infiltrating cell types (CD3+ T lymphocytes, macrophages) were not observed. Unexpectedly, only 40% of CR mice survived infection with H. hepaticus, with mortality observed as early as 1 wk following induction of colitis. CONCLUSION Increased adiposity does not influence colitis severity in SMAD3-/- mice. Importantly, caloric restriction negatively impacts survival following pathogen challenge, potentially due to an impaired immune response.

Increased presence of effector lymphocytes during Helicobacter hepaticus -induced colitis

AIM To identify and characterize drosophila mothers against decapentaplegic (SMAD)3-dependent changes in immune cell populations following infection with Helicobacter hepaticus (H. hepaticus). METHODS SMAD3(-/-) (n = 19) and colitis-resistant SMAD3(+/-) (n = 24) mice (8-10 wk of age) were infected with H. hepaticus and changes in immune cell populations [T lymphocytes, natural killer (NK) cells, T regulatory cells] were measured in the spleen and mesenteric lymph nodes (MsLNs) at 0 d, 3 d, 7 d and 28 d post-infection using flow cytometry. Genotype-dependent changes in T lymphocytes and granzyme B(+) cells were also assessed after 28 d in proximal colon tissue using immunohistochemistry. RESULTS As previously observed, SMAD3(-/-), but not SMAD3(+/-) mice, developed colitis, peaking at 4 wk post-infection. No significant changes in T cell subsets were observed in the spleen or in the MsLNs between genotypes at any time point. However, CD4(+) and CD8(+)/CD62L(lo) cells, an effector T lymphocyte population, as well as NK cells (NKp46/DX5(+)) were significantly higher in the MsLNs of SMAD3(-/-) mice at 7 d and 28 d post-infection. In the colon, a higher number of CD3(+) cells were present in SMAD3(-/-) compared to SMAD3(+/-) mice at baseline, which did not significantly change during infection. However, the number of granzyme B(+) cells, a marker of cytolytic lymphocytes, significantly increased in SMAD3(-/-) mice 28 d post-infection compared to both SMAD3(+/-) mice and to baseline values. This was consistent with more severe colitis development in these animals. CONCLUSION Data suggest that defects in SMAD3 signaling increase susceptibility to H. hepaticus-induced colitis through aberrant activation and/or dysregulation of effector lymphocytes.

Association of serum cytokines with colorectal polyp number and type in adult males.

Chronic inflammation contributes to colorectal carcinogenesis. To determine whether serum cytokines are associated with colon polyps, 126 asymptomatic men (48–65 years) were recruited during colonoscopy. Serum cytokine concentrations were measured. Odds ratios were determined using polytomous logistic regression for polyp number and type. Men with serum monocyte chemotactic protein-3 (MCP-3) or soluble interleukin-4 receptor (sIL-4R) concentrations in the highest tertile were 0.2 times less likely to have three or more polyps relative to no polyps. For each increase in serum MCP-3 or sIL-4R tertile a man was about 0.4 times less likely to have three or more polyps than to have no polyps. Men with serum concentrations of interferon-&agr;2 (IFN-&agr;2) or interleukin (IL)-7 in the highest tertile were three times more likely to have an adenoma than no polyps. Those with serum IL-8 concentrations in the highest tertile were four times more likely to have an adenoma than no polyps. For each increase in serum IFN-&agr;2, IL-7, or IL-8 tertile an individual was 1.8 times more likely to have an adenoma than to have no polyps. Serum concentrations of MCP-3, sIL-4R, IFN-&agr;2, IL-7, and IL-8 may indicate which men are more likely to have colorectal polyps.