Correlation of secreted protein acidic and rich in cysteine with diabetic nephropathy

Abstract

Objective To investigate the serum concentrations of secreted protein acidic and rich in cysteine (SPARC) in patients with diabetic nephropathy and SPARC mRNA and protein expressions in renal tissue of db/db mice.Methods Serum SPARC levels in normal subjects and patients with type 2 diabetes mellitus (without diabetic nephropathy),chronic renal failure (without diabetes mellitus),and diabetic nephropathy were determined with enzyme-linked immunosorbent assay.RT-PCR,Western blot,and immunofluorescence were used to detect the mRNA and protein expressions of SPARC in renal tissue of db/db mice.Results The serum level of SPARC in diabetic nephropathy group was significantly higher than those in normal group,type 2 diabetes mellitus,and chronic renal failure group [(5.78 ± 1.41 vs 3.58 ±0.41,4.51 ± 1.08,and 3.81 ± 1.16) μg/L,P＜0.05 or P＜0.01].The SPARC level in the type 2 diabetes mellitus group was higher than that in normal group (P＜0.05),but there was no difference between normal group and chronic renal failure.SPARC mRNA and protein levels in renal tissue of db/db mice were higher compared with the littermates (P ＜ 0.05).Conclusions The long term hyperglycemic state in patients with diabetic nephropathy causes pathological change of renal tissue.Simultaneously,increased secretion of SPARC from renal tissue results in elevation of serum SPARC level and may play a role in pathological change of diabetic nephropathy. Key words: Secreted protein acidic and rich in cysteine; Diabetic nephropathy; Insulin-like growth factor; Transforming growth factor β1