糖尿病性腎症における尿中糖蛋白分析 ： ウエスタンブロッティング分析によるレクチン結合パターン

Abstract

The aim of this study was to evaluate the clinical usefulness of polyacrylamide gel electrophoresis，followed by reaction with peroxidase-coupled lectins using urinary glycoproteins in 20 patients with diabetic nephropathy. After SDS-polyacrylamide gel electrophoresis (SDS-PAGE)，high performance lectin affinity chromatography (HPLAC) and immunoblotting of urinary glycoproteins with α₁-acid glycoprotein (α₁-AG) and α₁-microglobulin (α₁-MG) were performed. The lectins used were derived from Triticum vulgaris (WGA)，Phaseolus vulgaris (PHA-E₄)，Dolichos biflorus (DBA) and Lens culinaris (LCA)，which had a high affinity for β1→4 N-acetyl-D-gulcosamine (GlcNAcβ1→4GlcNAc)，N-acetyl-D-galactosamine (GalNAc)，α-galactosamine (α-GalNAc) and α-mannose (α-Man) residues，respectively. Electrophoretic patterns of urinary glycoproteins clearly showed the presence of lectin-reactive glycoproteins with molecular weights lower than that of albumin. The molecular weights of the main bands that reacted with WGA，namely PHA-E₄ and LCA，were respectively 50,000 and 38,000 daltons，and increased with the progression of diabetic nephropathy. WGA reacted strongly with many glycoproteins having a wide range of molecular weights. LCA and PHA-E₄ reacted preferentially with glycoproteins of molecular weight lower than 50,000 daltons，but with DBA no reaction was observed. These results suggest that low molecular-weight glycoproteins that are observed in the urine of patients with diabetic nephropathy have abundant carbohydrate residues such as GlcNAc β1→4 GlcNAc，GalNAc and α-Man，and include α₁-AG and α₁-MG. The excretion of low-molecular-weight glycoproteins with high affinities for some lectins suggests organic impairment in diabetic nephropathy.