Changes in the glomerular pore size selectivity in patients with type II diabetes mellitus

We measured the urinary excretion rate and clearance of three plasma proteins, albumin, transferrin, and IgG4, each of which has a similar isoelectric point, but a different molecular weight. This study consisted of 86 patients with type II diabetes mellitus and 15 healthy subjects. In the patients, the degree of the urinary excretion rate and clearance of both transferrin (TER and Ctrans) and IgG4 (IgG4 ER and CIgG4) closely correlated with that of the urinary excretion rate of albumin (AER). Although significant increases in the medians of TER and Ctrans were found even in the patients with AER of less than 5 μg/min, significant increases in the medians of IgG4 ER and CIgG4 were observed only in the patients with AER of more than 10 μg/min, in comparison with age-matched healthy subjects. Considering the biochemical properties of these proteins, our results indicate that an alteration in the glomerular size selectivity may appear even in patients with normoalbuminuria, and in patients with AER of more than 10 μg/min, more extensive damage in glomerular size selectivity may occur.