Objectives Dexamethasone is associated with adrenal insufficiency in adults and children with chronic disease. This association has not been studied after single-dose oral dexamethasone, the standard of care for children with croup. We hypothesized that single-dose oral dexamethasone in children with croup is associated with a transient decrease in endogenous glucocorticoids. Methods We conducted a prospective, 2-arm, pharmacodynamic study of single-dose oral dexamethasone 0.6 mg/kg (maximum, 12 mg) in children older than 2 years with croup compared with controls (children with febrile upper respiratory tract infections who did not receive dexamethasone). Primary outcome was urinary 6β-hydroxycortisol–cortisol ratio. Results Twenty-seven children were analyzed (22 with croup and 5 with upper respiratory tract infections). Median 6β-hydroxycortisol–cortisol ratios before dexamethasone, the following morning, and on days 1, 3, and 7 were 2.8, 2.2, 2.0, 2.8, and 2.6, respectively. Among controls, the median 6β-hydroxycortisol–cortisol ratios at the same time intervals was 1.9, 1.5, 1.8, 2.5, and 1.7, respectively. There were no significant differences in the change from time 0 between groups at any time point. There were no serious adverse events or infectious complications. Conclusions Single-dose oral dexamethasone is not associated with decreased endogenous corticosteroid levels in children with croup. Future studies should use criterion standard tests to rule out suppression of the hypothalamic-pituitary-adrenal axis and be powered sufficiently to identify adverse clinical outcomes.

Background and Purpose: Cisplatin-induced nephrotoxicity manifests as acute kidney injury (AKI) in approximately one third of patients receiving cisplatin therapy. Current measures of AKI are inadequate in detecting AKI prior to significant renal injury, and better biomarkers are needed for early diagnosis of cisplatin-induced AKI. Experimental Approach: C57BL/6 and FVB/N mice were treated with a single intraperitoneal injection of cisplatin (15 mg kg-1) or saline. Plasma, urine, and kidney samples were collected prior to cisplatin injection and 24-, 48-, 72-, and 96-hours following cisplatin injection. Untargeted metabolomics was employed using liquid chromatography-mass spectrometry to identify early diagnostic biomarkers for cisplatin-induced AKI. Key Results: There was clear metabolic discrimination between saline and cisplatin-treated mice at all timepoints (day 1 to day 4). In total, 26 plasma, urine, and kidney metabolites were identified as exhibiting early alterations following cisplatin treatment. Several of the metabolites showing early alterations were associated with mitochondrial function and energetics, including intermediates of the tricarboxylic acid cycle, regulators of mitochondrial function and indicators of fatty acid β-oxidation dysfunction. Furthermore, several metabolites were derived from the gut microbiome. Conclusion and Implications: Our results highlight the detrimental effects of cisplatin on mitochondrial function and demonstrate potential involvement of the gut microbiome in the pathophysiology of cisplatin-induced AKI. Here we provide a panel of metabolites to guide future clinical studies of cisplatin-induced AKI and provide insight into potential mechanisms behind cisplatin nephrotoxicity.

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Nonrenal clearance pathways such as drug metabolism are decreased in chronic kidney disease (CKD). Although the mechanism remains elusive, uremic toxin retention and an altered gut microbiota are suspected to influence cytochrome P450s (CYPs) contributing to the unpredictable pharmacokinetics in patients with CKD. We characterized dysbiosis and uremia in CKD to elucidate associations between CYP expression and CKD progression. Rats fed control or CKD-inducing adenine diet were subsequently studied at five time points over 42 days. CYP expression and activity were compared to alterations in the 1) plasma and liver metabolome and 2) gut bacterial microbiota. CYP3A2 and CYP2C11 were downregulated in CKD by ≥76% (p<0.001) concurrently with or slightly prior to CKD onset as defined by serum creatinine.Metabolite profiles were altered prior to changes in the gut microbiota, and gut-derived uremic toxins including indoxyl sulfate, phenyl sulfate and 4-ethylphenyl sulfate correlated with CYP3A2 or CYP2C11 expression. Bacterial genera Turicibacter and Parabacteroides were identified as being characteristic of CKD. In conclusion, CYP3A2 and CYP2C11 are downregulated before dysbiosis and correlate with select uremic toxins.

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