Red blood cell deformability and diabetic nephropathy

Abstract

To the editor: In an interesting study, Brown et al1.Brown C.D. Ghali H.S. Zhao Z. et al.Association of reduced red blood cell deformability and diabetic nephropathy.Kidney Int. 2005; 67: 295-300Google Scholar found an impaired red blood cell deformability in 57 adult type 2 diabetic patients. They used a filtration technique using polycarbonate membranes with straight channels of 3 micrometer pore diameter. In patients with diabetic nephropathy they found an increased impairment in red blood cell deformability. The hypothesis that an impaired red blood cell deformability contributes to renal function decline is very attractive and may give rise to therapeutic possibilities. Many studies found an impaired red blood cell deformability in diabetic patients; others, however, did not. Years ago we tested the hypothesis that red blood cell deformability contributes to diabetic nephropathy using both ektacytometry and erythrocyte filtration, with micropores with a diameter of 5 micrometer2.Schut N.H. Van arkel E.C. Hardeman M.R. et al.No decreased erythrocyte deformability in type 1 (insulin-dependent) diabetes, either by filtration or by ektacytometry.Acta Diabetol. 1993; 30: 89-92Google Scholar. In order to imitate local circumstances in the kidney red blood cell, deformability was also measured in hyperosmolar solutions. Seventy-one insulin-dependent diabetic patients were included, 25 patients without any sign of organ damage, 21 patients with microalbuminuria, 13 patients with overt nephropathy, and 12 patients with leg ulceration. No decreased red blood cell deformability was found in any of the diabetic groups with either technique, neither did the total group of 71 diabetic patients have a lower red blood cell deformability when compared to controls. Extaerythrocytic factors, such as leukocytes, plasma fibrinogen, and platelet microaggregates may influence filtration results. I suppose the filtration technique of Brown et al was corrected for this. These results may suggest that the filtration pore size of 3 micrometers used by Brown et al was more sensitive than the 5 micrometer pores filtration technique and ektacytometry that was used by us and that the lack of difference in our patient groups reflects this lack of sensitivity. On the other hand, the question arises whether such subtle differences in red blood cell deformability, if present, contribute to nephropathy in diabetic patients.