Tubular dysfunction impairs renal excretion of pseudouridine in diabetic kidney disease

Abstract

Plasma nucleosides-pseudouridine (PU) and N2N2-dimethyl guanosine (DMG) predict the progression of type 2 diabetic kidney disease (DKD) to end-stage renal disease, but the mechanisms underlying this relationship are not well-understood. We used a well-characterized model of type 2 diabetes ( db/db mice) and control non-diabetic mice ( db/m mice) to characterize the production and excretion of PU and DMG levels using liquid chromatography-mass spectrometry. The fractional excretion of PU and DMG was decreased in db/db mice compared to control mice at 24 weeks before any changes to renal function. We then examined the dynamic changes in nucleoside metabolism using in vivo metabolic flux analysis (MFA) with the injection of labeled nucleoside precursors. MFA revealed significant decreases in the ratio of urine-to-plasma labeling of PU and DMG in db/db mice compared to db/m mice indicating significant tubular dysfunction in diabetic kidney disease. We observed that the gene and protein expression of the renal tubular transporters involved with nucleoside transport in diabetic kidneys in mice and humans was reduced. In conclusion, this study strongly suggests that tubular handling of nucleosides is altered in early DKD, in part explaining the association of PU and DMG with human DKD progression observed in previous studies.