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.
Charge Selectivity of Proteinuria in Type I Diabetes Explored by Ig Subclass Clearance
Patrizia Pietravalle, Susanna Morano, Giuseppe Cristina, Maria Grazia De Rossi, Guido Mariani, Patrizia Cotroneo, Giovanni Ghirlanda, Aldo Clementi, Domenico Andreani, Umberto Di Mario; Charge Selectivity of Proteinuria in Type I Diabetes Explored by Ig Subclass Clearance. Diabetes 1 December 1991; 40 (12): 1685–1690. https://doi.org/10.2337/diab.40.12.1685
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