Peritoneal clearance of leptin in continuous ambulatory peritoneal dialysis

Leptin and plasminogen activator inhibitor-1 levels in children on chronic dialysis

PURPOSE

In this study, it is aimed to compare the serum leptin and PAI-1 levels and evaluate their relationship in children on hemodialysis (HD) and peritoneal dialysis (PD).

METHOD

Thirty-six patients on HD (mean age: 15.0 ± 2.8 years), 19 patients on PD (mean age: 13.0 ± 3.5 years) and 15 healthy subjects (mean age: 14.5 ± 2.7 years) were included in the study. Laboratory investigations included blood count, biochemical parameters, serum iron, iron binding capacity, parathormone, erythrocyte sedimentation rate, C-reactive protein (CRP), prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen, serum leptin and PAI-1 levels.

RESULTS

Serum leptin levels were significantly higher in HD group than in control group when the effects of BMI and sex were controlled, while PD and control groups had similar leptin levels. PAI-1 levels were also significantly higher in HD group than in control group, while there was no statistically significant difference in PAI-1 levels of PD and control group. PAI-1 levels and leptin levels were significantly correlated, which was independent of the effect of BMI in both HD and PD groups when they are evaluated separately.

CONCLUSION

Results of our study showed that HD patients had higher leptin and PAI-1 levels and leptin and PAI-1 levels were correlated significantly in both patient groups. The effect of elevated serum leptin and PAI-1 levels on the cardiovascular complications remains to be established.

Leptin and resistin levels and their relationships with glucose metabolism in children with chronic renal insufficiency and undergoing dialysis

AIM

The aim of the present study is: (i) to evaluate the serum concentrations of leptin and resistin in the paediatric patients with chronic renal impairment (CRI), on haemodialysis (HD) and on peritoneal dialysis (PD) treatment; (ii) to examine the relationship between these hormones; and (iii) to investigate the possible influence of these hormones on the insulin resistance and sensitivity indexes as well as on serum insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein-3 (IGFBP-3) levels.

METHODS

In total, 52 patients (15 patients with CRI, 24 PD patients and 13 HD patients) and 23 healthy age- and sex-matched control subjects were included in the present study.

RESULTS

Homeostasis model assessment of insulin resistance (HOMA-IR) was higher than 2.5 in 47.1% of the patients. IGF-1 levels of patients with CRI, PD and HD patients were significantly lower than those in the controls (P < 0.001, P < 0.001, P < 0.001, respectively). The leptin levels of patients with CRI and on PD and HD treatment were significantly higher than the control group (P = 0.038, P = 0.002, P = 0.006, respectively). Similarly, serum resistin levels of patients with CRI and those of PD and HD patients were higher when compared with healthy controls (P = 0.037, P < 0.001, P = 0.005, respectively).

CONCLUSION

Leptin and resistin levels were increased in the children with CRF; however, this elevation was not found to be associated with hyperinsulinism. Further studies to explain the mechanisms and consequences of the accumulation of these hormones in CRF may provide the therapeutical approach aiming to normalize their circulating levels.

A cute plasma ghrelin and leptin responses to oral feeding or intraperitoneal hypertonic glucose-based dialysate in patients with chronic renal failure

BACKGROUND

Chronic renal failure (CRF) is associated with increased plasma levels of ghrelin and leptin, but the regulation of the secretion of these hormones has been insufficiently studied, in this setting. The aim of this study was to analyze the acute effects of oral feeding or intraperitoneal 3.86% glucose-based dialysate infusion on plasma ghrelin and leptin levels in patients with CRF undergoing peritoneal dialysis (PD).

METHODS

Following a crossover design, 10 patients and eight healthy controls underwent a standardized oral intake, a 3.86% glucose-based dialysate PD exchange (patients) and placebo oral intake. We scrutinized acute changes in plasma ghrelin, leptin, glucose, insulin, and growth hormone (GH) levels.

RESULTS

In patients, total ghrelin decreased modestly immediately after oral feeding (nadir 90.6% of baseline, range 85.1, 94.5, P= 0.03) or the PD exchange test (92.2%, range 58.7, 101.9, P= 0.05) (median). Response to oral feeding was markedly blunted when compared with healthy individuals (73.8%, range 56.1, 89.1, P= 0.007) (P < 0.005 vs. patients). Plasma acyl-ghrelin had a less marked but more persistent decay after the PD exchange test (nadir 80.4%, range 55.1, 96.3, P= 0.02) than after oral intake (64.4%, range 45.6, 82.3, P= 0.005); again, changes were more intense in normal controls (47.4%, range 32.1, 67.3, P= 0.01) (P < 0.05 vs. patients). Leptin levels decreased slightly (P < 0.05) after the PD exchange in patients, but did not respond acutely to oral feeding in patients or controls.

CONCLUSION

Ghrelin secretion is partially refractory to the acute inhibitory effect of oral feeding in patients with CRF undergoing PD therapy. A 3.86% glucose-based PD exchange results in a significant decrease of plasma ghrelin levels. Plasma leptin levels are not acutely affected by oral feeding in patients with CRF or healthy individuals.

Protein and energy nutrition among adult patients treated with chronic peritoneal dialysis

Protein-energy malnutrition (PEM) in adult patients treated with chronic peritoneal dialysis (CPD), which is highly prevalent and frequently severe in its manifestation, poses a significant therapeutic dilemma. The causes of PEM include inflammation, low nutrient intake, nutrient losses during dialysis, metabolic acidemia, coexisting illnesses, and possibly the endocrine disorders of uremia. Treatment strategies for PEM in CPD patients include the following: attempt to treat the potentially reversible causes of anorexia, increase nutrient intake (by nutritional counseling, oral food supplements, consideration of appetite stimulants and intraperitonial amino acid solutions), and the correction of metabolic acidosis. Coexisting illnesses engendering PEM should be treated. Experimental evidence suggests that such agents as anabolic steroids, human growth hormone, insulin-like growth factor-I, and L-carnitine may engender positive protein balance in these individuals. Finally, the use of anti-inflammatory agents to improve the nutritional status of malnourished CPD patients remains to be defined. There is a need to carry out clinical trials that examine whether an improvement in the nutritional status of CPD patients is associated with an improvement in their mortality, morbidity and/or quality of life.

Low-Molecular Weight Proteins in End-Stage Renal Disease: Potential Toxicity and Dialytic Removal Mechanisms

ABSTRACT. Low-molecular-weight proteins (LMWP) are now recognized as a distinct class of uremic toxins, and numerous compounds in this category have been identified. Dr. Henderson has spent much of his career investigating ways to enhance the removal of intermediate- and large-sized uremic retention molecules. As LMWP clearly fall under this category, it is fitting to provide a review of several aspects of this molecular class. Normal renal metabolism of LMWP is discussed along with the changes that occur during chronic renal insufficiency. The effect of end-stage renal disease on plasma LMWP concentrations is assessed. As examples of the potential uremic toxicity of this molecular class, leptin, adrenomedullin, and the compounds associated with increased susceptibility to infection are highlighted. Finally, an overview of LMWP removal mechanisms for both hemodialysis and the convective therapies is provided.

Leptin and renal disease

Leptin is a small peptide hormone that is mainly, but not exclusively, produced in adipose tissue. The circulating leptin concentration therefore directly reflects the amount of body fat. Leptin was identified through positional cloning of the obese (ob) gene, which is mutated in the massively obese ob/ob mouse, and it has a pivotal role in regulating food intake and energy expenditure. It binds to the so-called long receptor (Ob-Rb) in the hypothalamus and regulates food intake through the release of other neurotransmitters. Moreover, leptin exerts several other important metabolic effects on peripheral tissue, including modification of insulin action, induction of angiogenesis, and modulation of the immune system. As a small peptide, leptin is cleared principally by the kidney. Not surprisingly, serum leptin concentrations are increased in patients with chronic renal failure and those undergoing maintenance dialysis. Whether the hyperleptinemia of chronic renal failure contributes to some uremic manifestations, such as anorexia and weight loss, requires additional investigation. The kidney expresses abundant concentrations of the truncated isoform of the leptin receptor Ob-Ra, but only a small amount of the full-length receptor Ob-Rb. We recently discovered that leptin has direct effects on renal pathophysiological characteristics. Both cultured glomerular endothelial cells and mesangial cells obtained from the diabetic db/db mouse possess the Ob-Ra receptor, but whether biological effects of leptin are transduced through this receptor remains unknown. In glomerular endothelial cells, leptin stimulates cellular proliferation, transforming growth factor-beta1 (TGF-beta1) synthesis, and type IV collagen production. Conversely, in mesangial cells, leptin upregulates synthesis of the TGF-beta type II receptor, but not TGF-beta1, and stimulates glucose transport and type I collagen production through signal transduction pathways involving phosphatidylinositol-3-kinase. These data suggest that leptin triggers a paracrine interaction in which glomerular endothelial cells secrete TGF-beta, to which sensitized mesangial cells may respond. Both cell types increase their expression of extracellular matrix in response to leptin. Infusion of leptin into normal rats for 3 weeks fosters the development of focal glomerulosclerosis and proteinuria. Additional previously described direct and indirect effects of leptin on the kidney include natriuresis, increased sympathetic nervous activity, and stimulation of reactive oxygen species. These findings collectively suggest that the kidney is not only a site of leptin metabolism, but also a target organ for leptin action in pathophysiological states.