The bovine gastrointestinal tract is the main reservoir for enterohaemorrhagic Escherichia coli (EHEC) responsible for food-borne infections. Characterization of nutrients that promote the carriage of these pathogens by the ruminant would help to develop ecological strategies to reduce their survival in the bovine gastrointestinal tract. In this study, we show for the first time that free ethanolamine (EA) constitutes a nitrogen source for the O157:H7 EHEC strain EDL933 in the bovine intestinal content because of induction of the eut (ethanolamine utilization) gene cluster. In contrast, the eut gene cluster is absent in the genome of most species constituting the mammalian gut microbiota. Furthermore, the eutB gene (encoding a subunit of the enzyme that catalyses the release of ammonia from EA) is poorly expressed in non-pathogenic E. coli. Accordingly, EA is consumed by EHEC but is poorly metabolized by endogenous microbiota of the bovine small intestine, including commensal E. coli. Interestingly, the capacity to utilize EA as a nitrogen source confers a growth advantage to E. coli O157:H7 when the bacteria enter the stationary growth phase. These data demonstrate that EHEC strains take advantage of a nitrogen source that is not consumed by the resident microbiota, and suggest that EA represents an ecological niche favouring EHEC persistence in the bovine intestine.
Elucidation of the relationships between genotype, diet, and health requires accurate dietary assessment. In intervention and epidemiological studies, dietary assessment usually relies on questionnaires, which are susceptible to recall bias. An alternative approach is to quantify biomarkers of intake in biofluids, but few such markers have been validated so far. Here we describe the use of metabolomics for the discovery of nutritional biomarkers, using citrus fruits as a case study. Three study designs were compared. Urinary metabolomes were profiled for volunteers that had (a) consumed an acute dose of orange or grapefruit juice, (b) consumed orange juice regularly for one month, and (c) reported high or low consumption of citrus products for a large cohort study. Some signals were found to reflect citrus consumption in all three studies. Proline betaine and flavanone glucuronides were identified as known biomarkers, but various other biomarkers were revealed. Further, many signals that increased after citrus intake in the acute study were not sensitive enough to discriminate high and low citrus consumers in the cohort study. We propose that urine profiling of cohort subjects stratified by consumption is an effective strategy for discovery of sensitive biomarkers of consumption for a wide range of foods.
Vitamin E and carotenoids are fat-soluble micronutrients carried by plasma lipoproteins. Their plasma concentrations are governed by several factors, some of which are genetic, but data on these genetic factors remain scarce. We hypothesized that genes involved in lipid metabolism, i.e. the genes implicated in intestinal uptake, intracellular trafficking, and the lipoprotein distribution of lipids, play a role in the plasma concentrations of these micronutrients. To verify this hypothesis, we assessed whether the plasma status of vitamin E and carotenoids is related to genes involved in lipid metabolism. Fasting plasma vitamin E (a-and g-tocopherol) and carotenoid (a-and b-carotene, lutein, lycopene, b-cryptoxanthin, and zeaxanthin) concentrations were measured in 48 males and 80 females. The following genes were genotyped [single nucleotide polymorphisms (SNP)]: apolipoprotein (apo) A-IV, apo B, apo E, lipoprotein lipase, and scavenger-receptor class B type I (SR-BI). Plasma a-tocopherol concentrations were different (P , 0.05) in subjects bearing different SNP in apo A-IV, apo E, and SR-BI. Plasma g-tocopherol concentrations were different (P , 0.05) in subjects bearing different SNP in apo A-IV and SR-BI. a-Carotene concentrations were different (P , 0.05) in subjects bearing different SNP in SR-BI. b-Carotene concentrations were different (P , 0.05) in subjects bearing different SNP in apo B and SR-BI. Lycopene concentrations were different (P , 0.05) in subjects bearing different SNP in apo A-IV and apo B. b-Cryptoxanthin concentrations were different (P , 0.05) in subjects bearing different SNP in SR-BI. Plasma lutein and zeaxanthin concentrations did not differ in subjects bearing different SNP. Most of the differences remained significant after the plasma micronutrients were adjusted for plasma triglycerides and cholesterol. These results suggest that genes involved in lipid metabolism influence the plasma concentrations of these fat-soluble micronutrients.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.