Modulation of urinary siderophores by the diet, gut microbiota and inflammation in mice.

Mammalian siderophores are believed to play a critical role in maintaining iron homeostasis. However, the properties and functions of mammalian siderophores have not been fully clarified. In this study, we have employed Chrome Azurol S (CAS) assay which is a well-established method for bacterial siderophores study, to detect and quantify mammalian siderophores in urine samples. Our study demonstrates that siderophores in urine can be altered by diet, gut microbiota and inflammation. C57BL/6 mice, fed on plant-based chow diets which contain numerous phytochemicals, have more siderophores in the urine compared to those fed on purified diets. Urinary siderophores were up-regulated in iron overload conditions, but not altered by other tested nutrients status. Further, germ-free mice displayed 50% reduced urinary siderophores, in comparison to conventional mice, indicating microbiota biotransformation is critical in generating or stimulating host metabolism to create more siderophores. Altered urinary siderophores levels during inflammation suggest that host health conditions influence systemic siderophores level. This is the first report to measure urinary siderophores as a whole, describing how siderophores levels are modulated under different physiological conditions. We believe that our study opens up a new field in mammalian siderophores research and the technique we used in a novel manner has the potential to be applied to clinical purpose.

Nitric oxide-derived urinary nitrate as a marker of intestinal bacterial translocation in rats.

BACKGROUND/AIMS: Bacterial translocation across the gut wall may lead to bacteremia and sepsis. Bacteriological analyses are laborious and time consuming, which precludes a rapid diagnosis of bacterial translocation. Synthesis of nitric oxide by macrophages is a primary response to bacterial infections. Therefore, the aim of this study was to examine whether NO-derived nitrate excretion in urine can be used as a rapid and quantitative marker of intestinal bacterial translocation. METHODS: The kinetics of urinary nitrate excretion was determined in rats intraperitoneally injected with increasing doses of Salmonella enteritidis lipopolysaccharide. Subsequently, the response to bacterial translocation was studied in rats infected orally with different doses of viable, invasive S. enteritidis. RESULTS: Increasing the lipopolysaccharide dose from 0.05 to 0.50 mg/kg resulted in a transient, dose-dependent, almost 10-fold increase in urinary nitrate excretion. Administration of the NO synthase inhibitor NG-nitro-L-arginine methyl ester merely inhibited the increase in nitrate excretion after lipopolysaccharide injection. Increasing the infective dose of viable Salmonella resulted in a time- and dose-dependent exponential increase in nitrate output. Translocation was a prerequisite for provoking a nitrate response. Total urinary nitrate excretion after infection and classical infection parameters, such as weight of the mesenteric lymph nodes and population levels of Salmonella in feces, were highly correlated. CONCLUSIONS: Urinary nitrate excretion is a quantitative, noninvasive biomarker of intestinal bacterial translocation, which can be used to follow the course of a systemic infection.