ABSTRACT
Nicotinamide adenine dinucleotide (NAD+) extends longevity in experimental organisms, raising interest in its impact on human health. De novo NAD+ biosynthesis from tryptophan is evolutionarily conserved yet considered supplanted among higher species by biosynthesis from nicotinamide (NAM). Here we show that a bottleneck enzyme in de novo biosynthesis, quinolinate phosphoribosyltransferase (QPRT), defends renal NAD+ and mediates resistance to acute kidney injury (AKI). Following murine AKI, renal NAD+ fell, quinolinate rose, and QPRT declined. QPRT+/- mice exhibited higher quinolinate, lower NAD+, and higher AKI susceptibility. Metabolomics suggested an elevated urinary quinolinate/tryptophan ratio (uQ/T) as an indicator of reduced QPRT. Elevated uQ/T predicted AKI and other adverse outcomes in critically ill patients. A phase 1 placebo-controlled study of oral NAM demonstrated a dose-related increase in circulating NAD+ metabolites. NAM was well tolerated and was associated with less AKI. Therefore, impaired NAD+ biosynthesis may be a feature of high-risk hospitalizations for which NAD+ augmentation could be beneficial.
Subject(s)
Acute Kidney Injury/metabolism , Biosynthetic Pathways , NAD/biosynthesis , Acute Kidney Injury/drug therapy , Acute Kidney Injury/urine , Aged , Animals , Cardiac Surgical Procedures , Humans , Ischemia/urine , Mice , Middle Aged , Niacinamide/administration & dosage , Niacinamide/therapeutic use , Pentosyltransferases/metabolism , Pilot Projects , Quinolinic Acid/metabolism , Quinolinic Acid/urine , Treatment Outcome , Tryptophan/urineABSTRACT
BACKGROUND: Human ascending thoracic aortic aneurysms (ATAAs) are life threatening and constitute a leading cause of mortality in the United States. Previously, we demonstrated that collagens α2(V) and α1(XI) mRNA and protein expression levels are significantly increased in ATAAs. METHODS AND RESULTS: In this report, the authors extended these preliminary studies using high-throughput proteomic analysis to identify additional biomarkers for use in whole blood real-time RT-PCR analysis to allow for the identification of ATAAs before dissection or rupture. Human ATAA samples were obtained from male and female patients aged 65 ± 14 years. Both bicuspid and tricuspid aortic valve patients were included and compared with nonaneurysmal aortas (mean diameter 2.3 cm). Five biomarkers were identified as being suitable for detection and identification of ATAAs using qRT-PCR analysis of whole blood. Analysis of 41 samples (19 small, 13 medium-sized, and 9 large ATAAs) demonstrated the overexpression of 3 of these transcript biomarkers correctly identified 79.4% of patients with ATAA of ≥4.0 cm (P<0.001, sensitivity 0.79, CI=0.62 to 0.91; specificity 1.00, 95% CI=0.42 to 1.00). CONCLUSION: A preliminary transcript biomarker panel for the identification of ATAAs using whole blood qRT-PCR analysis in men and women is presented.