From juvenile hyperuricaemia to dysfunctional uromodulin: an ongoing metamorphosis.

Familial juvenile hyperuricaemic nephropathy (FJHN) is a diagnosis that is easily missed. It has taken a long time to clarify the pathophysiology and prevalence of this disease entity which has been shown to be genetically identical to medullary cystic kidney disease (MCKD) type II. The initial suspicion that uric acid was the noxious agent has been replaced by the recognition that a mutant uromodulin (UMOD) is the real culprit-although the exact mechanisms of pathogenicity remain uncertain.

4-Pyridone-3-carboxamide-1-β-D-ribonucleoside triphosphate (4PyTP), a novel NAD metabolite accumulating in erythrocytes of uremic children: a biomarker for a toxic NAD analogue in other tissues?

We have identified a novel nucleotide, 4-pyridone 3/5-carboxamide ribonucleoside triphosphate (4PyTP), which accumulates in human erythrocytes during renal failure. Using plasma and erythrocyte extracts obtained from children with chronic renal failure we show that the concentration of 4PyTP is increased, as well as other soluble NAD(+) metabolites (nicotinamide, N(1)-methylnicotinamide and 4Py-riboside) and the major nicotinamide metabolite N(1)-methyl-2-pyridone-5-carboxamide (2PY), with increasing degrees of renal failure. We noted that 2PY concentration was highest in the plasma of haemodialysis patients, while 4PyTP was highest in erythrocytes of children undergoing peritoneal dialysis: its concentration correlated closely with 4Py-riboside, an authentic precursor of 4PyTP, in the plasma.