Association of reduced red blood cell deformability and diabetic nephropathy.

BACKGROUND Impaired red blood cell deformability may play a key role in the pathogenesis of chronic vascular complications of diabetes mellitus and progression of renal failure. The present study was conducted to test whether impaired red blood cell deformability is indeed associated with development of diabetic nephropathy. METHODS We studied 57 adult type 2 diabetic patients divided into three groups according to serum creatinine concentration. Group I comprised 28 diabetic patients with normal renal function (serum creatinine concentration <1.5 mg/dL, mean 1.0 +/- 0.3 mg/dL). Group II comprised 10 diabetic patients with renal insufficiency (serum creatinine concentration ranging from 2 to 6 mg/dL, mean 3.9 +/- 1.54 mg/dL). Group III consisted of 19 diabetic subjects with end-stage renal disease (ESRD) on hemodialysis (serum creatinine concentration ranging from 7.7 to 14.6 mg/dL, mean 10.1 +/- 2.4 mg/dL). In addition, 11 (mean serum creatinine concentration 4.2 +/- 1.5 mg/dL) and 10 (mean serum creatinine concentration 11.5 +/- 3.6 mg/dL) nondiabetic individuals, matched renal function for the diabetic groups (group II and III, respectively) served as control. Red blood cell deformability, measured by filtration technique, is defined as the filtration rate of erythrocyte suspension through a micropore filter divided by the filtration rate of a physiologic buffer solution. RESULTS In the diabetic cohort, we found substantially impaired red blood cell deformability in those with normal renal function (group I). With further renal function loss, an increased impairment in red blood cell deformability was observed. Diabetic patients with renal insufficiency (group II) when compared to non-diabetic controls (renal insufficiency) had a significantly greater impairment in red blood cell deformability (P= 0.01). The nondiabetic cohort (renal insufficiency), on the other hand, manifested significant impairment in red blood cell deformability. Their degree of impairment was statistically higher than that in diabetic patients with normal renal function (P= 0.0005). Interestingly, there was a progressive increase in red blood cell deformability impairment, along with progression of renal insufficiency, and thus no significant difference in the degree of red blood cell deformability impairment was observed between diabetic and nondiabetic patients with ESRD (P= 0.52). There is significant correlation between serum creatinine and impairment in red blood cell deformability in both diabetic (group II plus III) (r= 0.43, P= 0.02) and nondiabetic (r= 0.62, P= 0.003) cohorts. CONCLUSION In diabetic patients, early impairment in red blood cell deformability appears in patients with normal renal function, and progressive impairment in red blood cell deformability is associated with renal function loss in all patients regardless of the presence or absence of diabetes.