Charge selectivity of proteinuria in type I diabetes explored by Ig subclass clearance.
To investigate the role of protein charge in early diabetic proteinuria, the clearance of proteins differing in charge and/or size (anionic and cationic Igs, albumin) was evaluated in 98 insulin-dependent (type I) diabetic patients selected as a representative sample of the 418 patients attending our clinics. Of the patients, 12.9% were microalbuminuric and 4.8% were macroalbuminuric. Anionic and total IgG clearances were significantly increased in 30.6 and 12.2% of patients and were correlated with duration of disease. Anionic IgG4 clearances were increased in patients (9.2%) with normal IgG excretion, suggesting that charge-selectivity impairment is responsible for protein loss. Anionic Ig clearances were also higher in some patients (14.3%) with normal albumin clearance, probably as a result of different glomerular filtration and/or tubular reabsorption. The anionic-cationic IgG clearance ratio tended to increase in parallel with albumin clearance, but once above macroalbuminuric levels, it tended to fall again, indicating the concomitant presence of size-selectivity loss. The anionic IgG clearance and the anionic-cationic IgG ratio, in addition to albumin excretion, may be valuable in assessing early kidney protein charge-selectivity impairment and better characterizing normoalbuminuric patients and those in the preclinical stage of diabetic nephropathy.
Pietravalle
P
P
Department of Endocrinology, University La Sapienza, Rome, Italy.
Morano
S
S
Cristina
G
G
De Rossi
M G
MG
Mariani
G
G
Cotroneo
P
P
Ghirlanda
G
G
Clementi
A
A
Andreani
D
D
Di Mario
U
U
D000328:Adult; D000419:Albuminuria; D015415:Biomarkers / Q000652:urine; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology / Q000503:physiopathology / Q000652:urine*; D003928:Diabetic Nephropathies / Q000175:diagnosis; D005500:Follow-Up Studies; D005919:Glomerular Filtration Rate; D006801:Humans; D007074:Immunoglobulin G / Q000145:classification / Q000652:urine*; D008657:Metabolic Clearance Rate; D015233:Models, Statistical; D011507:Proteinuria
D015415:Biomarkers; D007074:Immunoglobulin G