Activation of renal dopaminergic system in early diabetic nephropathy

Early diabetic nephropathy is typically diagnosed using the urinary albumin-to-creatinine ratio or creatinine clearance to detect renal function decline in diabetic patients. However, it is not yet fully understood how the alteration of the renal dopaminergic system occurs during early diabetic nephropathy progression, or whether the system is a predictor of renal function associated with diabetic nephropathy. Mass spectroscopy imaging of the kidneys of spontaneously diabetic torii rats, an animal model of diabetes with diabetic nephropathy, revealed clearly differing a dopamine precursor L-dihydroxyphenylalanine distributions. Furthermore, the significantly increased excretion of urinary L-dihydroxyphenylalanine-to-creatinine or urinary dopamine-to-creatinine ratios are observed before the development of microalbuminuria. The present study represents the renal dopaminergic system responses along the progression of diabetic nephropathy, and our results will facilitate understanding of the association between early diabetic nephropathy pathogenesis and the renal dopaminergic system.