The incidence of inflammatory bowel diseases has increased during recent decades. Within the colon, the families of mucins (MUC) and trefoil factors (TFF) facilitate mucosal protection. Probiotic administration influences the intestinal MUC layer. Additionally, food components may affect gut microflora or have direct effects on the MUC barrier. Our objective was to determine whether diet and/or Lactobacillus rhamnosus GG (LGG) would mediate dextran sodium sulfate (DSS)-induced colitis by altering expression of the MUC and TFF genes. C57BL/6 mice were fed diets containing 20% (wt:wt) casein, soy, or whey proteins with or without LGG for 12 d. Seven days after starting LGG diets, the mice were given 2% DSS in drinking water for 4 d. Two additional casein groups with or without LGG were given tap water, for a total of 8 groups. One day after the DSS treatment, the mice were killed and the colon and cecum tissues and cecum contents were collected and analyzed by qRT-PCR. Whey protein significantly increased cecal LGG content compared with the other diets. In the casein diet groups, MUC1 and TFF-3 expression in colon was significantly induced by DSS independent of LGG. Compared with other DSS-treated groups, soy protein decreased MUC-1 and TFF-3 in the colon. Similarly, soy protein decreased the impact of DSS on inflammatory scores, TNFα gene expression, and colon shortening. There was no overall effect of LGG on these measurements. In conclusion, soy protein suppressed the DSS-induced inflammatory stimulation of MUC, TFF, and TNFα gene expression independently of LGG.

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The incidence of inflammatory bowel diseases (IBD) is increasing in the US. Dietary factors impact the symptoms of IBD, although the food matrix and milieu of the gastrointestinal tract create challenges for therapy. Based on previously documented success in managing necrotizing enteropathy in neonatal pigs using a concentrated form of blood‐derived immunoglobulins, we explored the role of this product in alleviating the symptoms of IBD in a mouse model. ImmunoLin® (Proliant Health Ingredients, Ankeny IA) contains a mixture of mainly IgG with IgA, IgM, IgE, and IgD. We hypothesized that the immunoglobulins in this product would reduce colon inflammation. We treated C57BlackJ mice with 2% dextran sodium sulfate (DSS) for 4 days and then fed AIN‐93G diets containing 0, 11.25, 22.5 or 45 g/kg ImmunoLin® for 7 or 14 days. Colon tissue was snap frozen and 23 cytokines were analyzed by Luminex immunoassay. DSS resulted in elevated expression of most cytokines in the mouse colon. After 14 days the lower doses of ImmunoLin® reduced IL‐1α, IL‐4, IL‐6, IL‐10, MCP‐1 and KC, but the highest dose was ineffective. In a parallel study, feeding the 45g dose for 14 days prior to DSS treatment had no protective effect on these cytokines. Thus, low doses of ImmunoLin® reduced cytokine induction in response to DSS in mice and may have value in human therapy. Funded by USDA special grant to the ISU Center for Designing Foods to Improve Nutrition.

vii CHAPTER 1: LITERATURE REVIEW Physiological and cellular characterization of the colon mucosa 1 Overview of inflammatory bowel diseases 5 Etiology of IBD 6 IBD animal models: classification, DSS model 10 MUC genes and DSS induced colitis 13 TFF genes and DSS induced colitis 14 TNF-α as an inflammatory marker in DSS induced colitis 16 Probiotic and barrier function 18 Dairy proteins and barrier function 20 Soy protein and barrier function 22 Hypothesis 25 iii CHAPTER 2: REDUCTION IN MUCOSAL BARRIER MARKERS WITH SOY PROTEIN DIET BUT NOT LACTOBACILLUS RHAMNOSUS GG IN DSS-TREATED MICE Abstract 26 vi ACKNOWLEDGEMENTS I would like to take this opportunity to express my acknowledgements to those who helped me during the two years I conducted research and wrote this thesis. I thank Dr. Ruth S. MacDonald for her guidance, support and patience throughout my education. Her encouragement always inspired me when I came across difficulties in my research and in the writing of this thesis. I admire her dedication, passion and confidence as a scientist and her responsibility as an educator. I thank Dr. Joseph Przybyszewski for his constant help and support. He taught me a lot of experimental skills and assisted me to complete the study and analyze the data. This work could not be possible without his support. I also thank my committee members for their contributions to my education: Dr. Stephanie Clark, Dr. Suzanne Hendrich, Dr. Michael Wannemuehler and Dr. Eric Weaver. They gave me countless valuable suggestions about my research and made this work better. I would also like to thank Dr. Byron Brehm-Stecher for providing the facility to culture the probiotic and examine the histological sections, Jack Gallup for helping with the PCR, Debjani Mitra for preparing the probiotic, and Chad Becker for his assistance in this project. Last but not least, I would like to express my appreciation to my family and friends for their love and support. vii ABSTRACT Inflammatory bowel disease (IBD) is a common ailment affecting people of all ages. Even though the pathogenesis of IBD has not been fully elucidated, there is evidence that it involves interactions between genetic susceptibility, aberrant activation of the immune system, and the environment. Inflammation of the colon (colitis) results in pain, diarrhea, hemorrhage, and weight loss. Within the colon, the family of mucins (MUC) and trefoil factors (TFF) facilitate mucosal protection. Recent studies found that probiotic administration could influence the colonic mucin layer. Additionally, food components may affect gut microflora or have influence on the mucin barrier. Our aims were to explore the role of probiotic administration in modulating MUC and TFF gene expression in the dextran sodium sulfate (DSS) induced colitis mouse model, and to examine interactions with casein, whey, or soy protein diets. C57BL/6 mice were assigned to three diet groups. Diets were formulated to substitute casein, whey or soy protein on an equivalent basis. On day 6, each diet group was divided into 2 g...

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