Vitamin D, folate, and cobalamin (vitamin B12) are crucial micronutrients in human physiology that are necessary for healthy calcium, phosphorus, and single-carbon metabolism. Recent studies have indicated that these vitamins also affect the inflammatory response in ways unrelated to their well-characterized deficiencies. Accordingly, analysis of their effect on chronic inflammatory diseases like Crohn's disease (CD) is warranted. This investigation examines the effects of vitamin deficiency on macrophages and intestinal epithelial cells upon exposure to Mycobacterium avium paratuberculosis (MAP,) a pathogen capable of triggering CD, to model the inflammatory response in clinical CD patients. ELISA analysis of CD patient plasma established that MAP-positive patients have lower folate, vitamin B12, and active vitamin D (calcitriol) than MAP-negative patients. Next, we investigated the effects of folate and vitamin B12 deprivation on macrophages to assess inflammatory cytokine expression, oxidative stress, and macrophage apoptosis. We determined that folate and B12 deprivation exacerbates inflammation while preventing infected macrophages from successfully undergoing apoptosis, whereas supplementation reversed these effects. Then, we examined the role of vitamin D in regulating cathelicidin expression during MAP infection. MAP infection blocked the conversion of inactive vitamin D (calcifediol) to calcitriol, thereby interrupting the expression of the antimicrobial peptide cathelicidin. Calcitriol treatment restored cathelicidin production, reduced inflammation and bacterial viability, and reduced oxidative stress in co-cultured macrophages, Furthermore, cathelicidin knockdown abolished calcitriol's beneficent effects. These studies detail the importance of vitamin availability for healthy immune functionality. The attenuation of inflammation during MAP infection further indicates that CD patients, who are at elevated risk of vitamin deficiency, may benefit from supplementation or clinical screening for low vitamin levels.
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Doctor of Philosophy (Ph.D.)
College of Medicine
Burnett School of Biomedical Sciences
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Vaccaro, Joseph, "Role of Vitamin D, Folate, and Cobalamin Deficiency in Mycobacterium avium Paratuberculosis Infection and Inflammation" (2023). Electronic Theses and Dissertations, 2020-. 1685.