Type 2 Diabetic Patients with Greater Urinary Albumin Excretion and Less Severe Glomerulopathy
B Najafian, P Fioretto, ML Caramori, M Mauer. University of Minnesota, Minneapolis, MN; University of Padova, Padova, Italy
Background: Proteinuria is commonly known as a marker of severe glomerulopathy in diabetic nephropathy (DN). While most renal structural-functional relationship (RSFR) studies of DN have been done in type 1 diabetes (T1DM), SFR in type 2 diabetes (T2DM) is not thoroughly understood.
Design: RSFR was studied in 161(M/F=60/101) T1DM and 133 (M/F=88/45) T2DM patients with a wide range of urinary albumin excretion rate (AER) and glomerular filtration rate (GFR). Mesangial fractional volume [Vv(Mes/glom)], glomerular basement membrane (GBM) width and peripheral GBM surface density [Sv(PGBM/glom)] were estimated in research biopsies using electron microscopy stereology.
Results: AER and GFR values were not statistically different between T1DM and T2DM patients. Multiple regression analysis in T1DM patients with Vv(Mes/glom), GBM with and Sv(PGBM/glom) as predictors and AER as dependent variable provided a model which explained 70% of AER variability (p<0.00001). This same model explained 31% (p=0.01) of AER variability in T2DM patients. Data from T1DM and T2DM patients were pooled together. AER values predicted by glomerular structural parameters were calculated. Squared (observed predicted) AER values with sign preservation were used for k-means cluster analysis to obtain two maximally different groups A and B. 99% of T1DM and 74% of T2DM patients were clustered in A. All T2DM patients in B had AER>20 g/min. T2DM patients in A and B with AER>20 g/min were compared.
Table 1. Renal structural and functional values in microalbuminuric and proteinuric T2DM patients in groups A and B
|GBM width (nm)||500128||458124||0.13|
Conclusions: T2DM patients are heterogenous in RSFR. While RSFR in 3/4 of T2DM patients resembles that of T1DM patients, 1/4 of T2DM patients have greater AER values despite less severe glomerulopathy (less mesangial expansion and more filtration surface density). Conventional relation of AER values to severity of diabetic glomerulopathy and classification of patients into normo, micro, and macroalbuminuric groups may not be clinically relevant in all T2dm patients.
Category: Kidney (does not include tumors)
Tuesday, March 10, 2009 1:00 PM
Poster Session IV # 192, Tuesday Afternoon