Use of Nmr-based Metabonomics to Study Animal Models and Human Disease

Résumé du livre

This dissertation describes the effects that both antibiotics and opportunistic pathogens had on the host and gut metabolome, as well as the physical effects that these experimental factors had on the distal ileum of the study mice. The dissertation also presents urinary metabolic profiles in order to identify statistically significant changes in metabolites that could be used as a biomarker for early disease diagnosis and treatment. In chapter 1 a background of both human and animal model metabonomics studies is presented, including an overview of NMR and the multivariate statistical analysis method, PCA, which was utilized in all work in this dissertation. Chapter 2 illustrates the effects that a broad spectrum antibiotic, Baytril, has on the urinary and fecal metabolic profiles of Balb/c mice. It was found that eliminating bacterial species from the gut caused significant changes in metabolic profiles of study mice. Many of the metabolic changes were a direct result of bacterial cell death and a lack of bacterial processes that naturally occur in the host intestinal tract. Chapter 3 takes the study design in Chapter 2 a few steps further and following antibiotic treatment an opportunistic pathogen, Clostridium butyricum was introduced to the mice by an intragastric gavage procedure. C. butyricum has been linked to necrotizing enterocolitis (NEC) in past studies and has been isolated from the blood and fecal cultures of neonates diagnosed with NEC. It was determined that administering a broad spectrum antibiotic to the mice altered both the urine and fecal metabolic profiles and also had negative effects on the structural integrity of the distal ileum of the same mice. Rather than further amplify the intestinal injury in the mice, the Clostridial species brought the metabolic profile of the mice back to that which was similar to the control mice, and the intestinal villi that were damaged by the antibiotics was able to repair as bacterial colonization became more prominent. Chapter 4 describes the metabolic changes in the urine samples of 20 preterm infants over the first 14 days of life with the goal of identifying a marker for acute kidney injury. Three infants of the extremely low birth weight (ELBW) group were found to have elevated levels of one metabolite, carnitine, and this increase was also correlated to spikes in neutrophil gelatinase-associated lipocalin (NGAL), the current biomarker for acute kidney injury in adults. Chapter 5 is a study comparing the urinary metabolic profiles of patients suffering from class IV and class V lupus nephritis (LN) and focal segmental glomerulosclerosis (FSGS). Two metabolites, citrate and taurine, were found to be changing significantly between class IV and class V patients, and hippurate was identified as changing when comparing class V LN and FSGS patients. The metabolic changes in these three metabolites were all linked to amore severe renal tubular dysfunction in the class V LN patients. The results contained in this dissertation demonstrated the ability of NMR to be used as a tool to identify markers of injury and disease in both mouse models and human diseases.