Effects of short-term glycemic control, low protein diet and administration of enalapril on renal hemodynamics and protein permselectivity in type 2 diabetic patients with microalbuminuria

To determine whether each of glycemic control (GC), low protein diet (LPD) or administration of angiotensin converting enzyme inhibitor (ACEI) has ben eficial effects on diabetic nephropathy through the different mechanisms, c hanges in charge and size selectivity of glomerulus and renal hemodynamics were analyzed in microalbuminuric type 2 diabetic patients after additive c ombination therapy (first period: GC only, second period: GC+ LPD, third pe riod: GC+LPD+ACEI). To detect improvement of the impairments of glomerular charge selectivity and size selectivity, changes in the ratio of the renal clearance of two plasma proteins with similar molecular radii and different isoelectric points (pIs) (ceruloplasmin and IgG: CRL/IgG) and changes in t he ratio of the renal clearance of two plasma proteins with similar pIs and different molecular radii (cua-macroglobulin and albumin: alpha 2/Alb) mer e examined before and after each therapy. Creatinine clearance decreased si gnificantly in the first and third periods although slight but not signific ant decrease was detected in the second period. Filtration fraction was sig nificantly decreased only in the third period. Although renal clearances of Alb, IgG and CRL were decreased in periods of all three therapies, that of alpha 2-macroglobulin with a large molecular radius was decreased signific antly only after the third therapy. Neither CRL/IgG nor alpha 2/Alb changed during these three therapies. These findings suggest that each of three sh ort-term therapies consisting of CTC, GC+LPD and GC+LPD+ACEI, reduced prote inuria in microalbuminuric type 2 diabetic patients not through the improve ment of renal size and charge selectivities, but through improvement of ren al hemodynamics. (C) 1999 Tohoku University Medical Press.