Metabolic consequences of peritoneal dialysis treatment.

Energy and protein metabolism are both altered in chronic kidney disease (CKD) from its early stages. Patients undergoing peritoneal dialysis (PD) use peritoneal solutions with glucose as osmotic agent, which exposes them to an increased glucose load (40-80 g/day) and during PD there is a net loss of proteins through the peritoneum (4-8 g/day). Insulin resistance may lead to a reduction of the anabolic effects of insulin, while its proliferative effects on adipose tissue are potentially enhanced. Insulin resistance is also an important factor in the development of hypertriglyceridemia in PD patients: it increases free fatty acid availability, which then stimulates the release of large triglyceride-rich VLDL. Moreover, inhibitors of lipolytic enzymes (apoC-III, inflammation, oxidative modification and carbamoylation of apolipoproteins) may reduce lipid clearance, contributing to the development of dyslipidemia. Inflammatory molecules also play an important role in regulating glucose metabolism, and the excessive activation of inflammatory pathways may represent a fundamental step in the development of insulin resistance, including an over-expression of cytokines. Frequently, protein intake is reduced in PD because of under-dialysis, glucose load, abdominal discomfort and abnormal hormones levels, leading to a complex "protein-energy malnutrition". Optimization of dialysis dose, correction of acidosis and anemia and nutritional counseling, together with "non-traditional" management strategies, such as the use of PD solutions without glucose, like icodextrin and amino acid based solutions, represent the best strategies to prevent and correct malnutrition in PD patients. The mainstay of therapy is a reduction of glucose-based PD solutions and a correct dietary prescription.