Abstract
The morphologic alterations in the kidney and the retina that can be present in patients with diabetic microangiopathy are mediated by growth factors. Vascular endothelial growth factor (VEGF) is a mediator of neoangiogenesis in diabetic retinopathy. Transforming growth factor-β (TGF-β) is involved in the extracellular matrix proliferation in diabetic nephropathy. The aim of the present study was to investigate the presence of VEGF and TGF-β1 in peritoneal effluents of patients undergoing continuous ambulatory peritoneal dialysis who are being treated with glucose-containing dialysis solutions in relation to parameters of peritoneal transport. Standard peritoneal permeability analyses with 3.86% glucose dialysate were performed in 16 stable patients undergoing peritoneal dialysis (PD) (median duration of PD 39 months, range 1 to 104 months). The power relationship that is present between dialysate/serum (D/S) ratios of serum proteins that are transported only across the peritoneal membrane and their molecular weights was used to predict the D/S ratios when diffusion would be the only explanation for the measured dialysate concentration. It was assumed that all TGF-β1 in the circulation was bound to α2-macroglobulin. The D/S ratios of VEGF (P < .0005) and TGF-β1 (P < .015) were significantly higher than expected when VEGF and TGF-β1 would have been transported from the circulation only by diffusion. No relationship was present between the effluent concentration attributed to the local production of VEGF (LVEGF) and that of TGF-β1 (LTGF-β1). LVEGF correlated with the mass transfer area coefficient (MTAC) creatinine value (r = 0.69, P < .007), MTAC urate value (r = 0.60, P < .02), and glucose absorption value (r = 0.75, P < .004), all reflections of the peritoneal vascular surface area. A negative correlation was observed between the transcapillary ultrafiltration (926 mL/4 h, 394 to 1262 mL/4 h) and LVEGF (r = −0.52, P < .045). This negative tendency was also observed between the net ultrafiltration (622 mL/4 h, −43 to 938 mL/4 h) and LVEGF (r = −0.48) but did not reach significance. LVEGF and the duration of treatment did not correlate, possibly because of the relatively small number of patients. LTGF-β1 showed no relationship with transport parameters or duration of treatment. In conclusion, we found evidence for the local production of both VEGF and TGF-β1 in the peritoneal membrane of patients undergoing long-term peritoneal diolysis with glucose-based dialysate solutions. The analogy with VEGF in diabetic retinopathy suggests a pathogenetic role of high dialysate glucose concentrations in the development of these alterations in the peritoneal membrane.
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