The Urinary Phosphate to Serum Fibroblast Growth Factor 23 Ratio, Deemed the Nephron Index, Is a Useful Clinical Index for Early Stage Chronic Kidney Disease in Patients with Type 2 Diabetes: An Observational Pilot Study

Abstract

Renal function decline is associated with progressive type 2 diabetes mellitus, which causes mineral and bone disorders. In the present study, we defined the ratio of urinary phosphate excretion (mg/day) to serum fibroblast growth factor 23 as the nephron index. We examined changes in the nephron index in type 2 diabetes patients with early stage chronic kidney disease (stages 1–3), enrolling 15 patients and retrospectively analysing the follow-up data. After follow-up at 5.4 years, we observed no significant changes in the estimated glomerular filtration rate; the nephron index, however, was significantly reduced between the baseline and the follow-up. We propose that the nephron index may be potentially useful as a biomarker for monitoring the decline of renal function in the early stages of diabetic chronic kidney disease patients.

Nephron index rather than serum FGF 23 predicts endothelial dysfunction in early but not advanced chronic kidney disease patients

“…In such individuals, the renal tubular response to FGF23 may be suboptimal [ 29 ]. In 142 diabetic-early CKD patients, a decrease in nephron index reflects early-stage renal impairment and is an independent risk factor of atherosclerosis in diabetic patients [ 13 ]. In another Indian cohort of 110 predialysis CKD, the nephron index was found to be correlated to atherosclerosis measured by carotid intimal media thickness [ 30 ].…”

“…The ratio of urinary phosphate excretion (mg/day) to serum FGF23 was considered as an index reflecting the functional nephron number, which was defined as the nephron index [ 11 ]. The nephron index was reported before to be associated with atherosclerosis in early-stage CKD [ 12 ] and diabetic CKD [ 13 ]. Since it is anticipated that it will begin to decline in the early stages of CKD, we hypothesize that the nephron index can be a more sensitive predictor of the early ED than serum FGF 23 testing alone.…”