N-phenacylthiazolium bromide decreases renal and increases urinary advanced glycation end products excretion without ameliorating diabetic nephropathy in C57BL/6 mice

Aims: Advanced glycation end products (AGE), which form from the non-enzyma tic reaction of proteins and sugars, have been implicated in the pathogenes is of diabetic nephropathy. Recently, a compound [N-phenacylthiazolium brom ide (PTB)] has been described which cleaves alpha,beta -dicarbonyl compound s. In the present study we used diabetic C57BL/6 mice to determine if PTB a ltered renal AGE levels and reduced diabetic glomerulosclerosis. Methods: Mice with stable hyperglycaemia induced by streptozotocin were giv en daily subcutaneous injections of either PTB (10 mug/g) or saline for 12 weeks. Renal-collagen bound AGE and urinary AGE-peptides were measured by E LISA using an anti-AGE-RNase antibody. Renal collagen-released N-epsilon(ca rboxymethyl)lysine (CML) and pentosidine were determined by high pressure l iquid chromatography (HPLC). Glomerular lesions (volume and mesangial/total surface area) were evaluated by computer-assisted image analysis. We deter mined urinary protein/ creatinine ratio as a functional parameter. AGE loca lization was examined by immunohistochemistry using the anti-AGE-RNase anti body. Results: Renal collagen-bound AGE were decreased and urinary AGE excretion was increased in PTB-treated diabetic mice. However, collagen-released CML and pentosidine were similar in both groups. Glomerular histology and morph ometric analysis revealed also no differences between PTB-and saline-treate d diabetic mice. The urinary protein/creatinine ratio was unaffected by PTB -treatment. AGE staining by anti-AGE-RNase antibody was present in Bowman's capsules, glomerular basement membranes and cortical tubules. It was decre ased in all structures in PTB-treated diabetic mice. Conclusion: In summary, PTB decreased renal AGE accumulation but did not am eliorate glomerular lesions or proteinuria. Thus, cleavage of AGE by PTB is not sufficient to prevent development of diabetic nephropathy in C57BL/6 m ice.