Predictive value of urinary low molecular weight proteins for progression of early diabetic nephropathy in patient with type 2 diabetes mellitus

Objective To investigate the predictive value of urinary low molecular weight proteins for progression of diabetic nephropathy in type 2 diabetic patient with microalbuminuria. Methods Urinary excretion amounts of alpha-1-microglobulin (α1-MG), retinal-binding protein (RBP), N-acetyl-beta-D-glucosaminidase (NAG) and beta-2-microglobulin (β2-MG) were determined in 66 patients of type 2 diabetes mellitus with microalbuminuria at baseline. The patients were followed up for 3 1～5 5 years 〔(4 18±0 61) years〕 and then divided into two groups(progression group and non-progression group) according to whether or not to progress to clinical diabetic nephropathy during the follow-up period. Results 18 of 66 patients progressed to clinical diabetic nephropathy during follow-up period. The initial urinary α1-MG,RBP,NAG excretion level in progression group were higher significantly than that in non-progression group respectively(α1-MG:4 33±2 15 vs 1 50±0 27 mg/L;RBP:63 6±36 6 vs.18 8±19 6 ng/mmol; NAG: 14 2±1 44 vs 2 45±2 09 U/mmol, P respectively 0 01). But the initial urinary β2-MG level was not significantly different between the two groups. There were 83 3%,89 9% and 44 4% of patients in progression group who showed an abnormal elevation of initial urinary α1-MG,RBP,NAG excretion levels, respectively, while compared with the reference range of normal healthy adults, which were higher significantly than in non-progression group(P0 01). But the percentage of patients with abnormal initial urinary β2-MG excretion level was not significantly different between the two groups(P0 05). The mean HbA1c, blood lipid levels, blood pressure during follow-up period were not significantly different between the two groups. Conclusions Measurements of urinary α1-MG,RBP and NAG may be useful for predicting whether or not development of clinical diabetic nephropathy in patient of type 2 diabetes mellitus with microalbuminuria. Elevation of urinary α1-MG,RBP and NAG level may be one of characteristics of early diabetic nephropathy.