Experimental diabetes induces functional and structural changes in the peritoneum

Background. Peritoneal dialysis (PD) is an established renal replacement therapy in diabetic patients, but the influence of diabetes on the peritoneal membrane (PM) remains debated. We have used functional, biochemical and molecular studies in vivo and in vitro to substantiate the changes induced by diabetes and hyperglycemia in the PM. Methods. Peritoneal equilibration tests were performed 2, 4, and 6 weeks after induction of diabetes with streptozotocin (STZ) in rats. Morphological analyses, determination of nitric oxide synthase (NOS) activities, and expression studies for NOS isoforms and advanced glycation end products (AGE) were performed in parallel. Additional studies were conducted in diabetic rats treated with insulin, non-diabetic rats fed with urea, and cultured bovine aortic endothelial cells (BAEC). Results. In comparison with controls, diabetic rats were characterized by: increased permeability for small solutes and decreased sodium sieving; capillary proliferation; increased endothelial NOS (eNOS) and AGE immunoreactivity; up-regulation of eNOS and down-regulation of neuronal NOS; and increased NOS activity in the PM. The changes, which culminated at week 6, were prevented by chronic insulin treatment in diabetic rats. In contrast to hyperglycemia, hyperosmolality alone did not induce functional or structural changes in the PM. Studies in BAEC showed that high glucose incubation led to increased activity and expression of eNOS, a prerequisite for vascular proliferation. Conclusions. These data demonstrate that chronic hyperglycemia is associated with functional and structural changes in the peritoneum that parallel with selective regulation of NOS isoforms and AGE deposits. The alterations are prevented by insulin treatment, which suggests that adequate control of diabetes can preserve PM integrity in diabetic patients prior to PD.