The leptin/adiponectin ratio: Potential implications for peritoneal dialysis

Sterile inflammation of peritoneal membrane caused by peritoneal dialysis: focus on the communication between immune cells and peritoneal stroma

Peritoneal dialysis is a widely used method for treating kidney failure. However, over time, the peritoneal structure and function can deteriorate, leading to the failure of this therapy. This deterioration is primarily caused by infectious and sterile inflammation. Sterile inflammation, which is inflammation without infection, is particularly concerning as it can be subtle and often goes unnoticed. The onset of sterile inflammation involves various pathological processes. Peritoneal cells detect signals that promote inflammation and release substances that attract immune cells from the bloodstream. These immune cells contribute to the initiation and escalation of the inflammatory response. The existing literature extensively covers the involvement of different cell types in the sterile inflammation, including mesothelial cells, fibroblasts, endothelial cells, and adipocytes, as well as immune cells such as macrophages, lymphocytes, and mast cells. These cells work together to promote the occurrence and progression of sterile inflammation, although the exact mechanisms are not fully understood. This review aims to provide a comprehensive overview of the signals from both stromal cells and components of immune system, as well as the reciprocal interactions between cellular components, during the initiation of sterile inflammation. By understanding the cellular and molecular mechanisms underlying sterile inflammation, we may potentially develop therapeutic interventions to counteract peritoneal membrane damage and restore normal function.

The associations of leptin and adiponectin with the metabolic syndrome in an Indonesian and a Dutch population

BACKGROUND AND AIMS

At the same BMI, Asian populations develop cardiometabolic complications earlier than Western populations. We hypothesized that a different secretion of the adipocyte-derived hormones leptin and adiponectin plays a role and investigated the associations of the two hormones with the metabolic syndrome (MetS) in an Indonesian and a Dutch population.

METHODS AND RESULTS

We performed cross-sectional analyses of the Netherlands Epidemiology of Obesity Study (n = 6602) and the SUGAR Scientific Programme Indonesia-Netherlands Study (n = 1461). We examined sex-stratified associations of leptin and adiponectin with MetS, using multivariate logistic regression including adjustment for total body fat. The mean (SD) leptin (mcg/L) were 4.7 (6.0) in Indonesian men, 18.6 (12.0) in Indonesian women, 9.1 (7.7) in Dutch men, and 23.4 (17.4) in Dutch women. The mean (SD) adiponectin (mg/L) were 5.7 (5.4), 7.5 (7.1), 6.6 (3.3), and 11.3 (4.9), respectively. Within the same BMI category, leptin concentrations were similar in the two populations, whereas adiponectin was lower in the Indonesian population. Per SD of leptin, adjusted prevalence odds ratios (ORs, 95%CI) of MetS were 0.9 (0.6-1.2) in Indonesian men, 1.1 (0.9-1.4) in Indonesian women, 2.2 (1.6-2.8) in Dutch men, and 1.2 (1.0-1.5) in Dutch women. Per SD of adiponectin, the ORs were 0.9 (0.7-1.2), 0.8 (0.7-1.0), 0.6 (0.6-0.8), and 0.4 (0.4-0.5), respectively.

CONCLUSIONS

Despite lower adiponectin levels, adiponectin was not related to the MetS in the Indonesian population and can not explain their increased cardiometabolic risk at the same BMI.

Effects of dynamic and isometric resistance training protocols on metabolic profile in hemodialysis patients: a randomized controlled trial

The aim of this study was to compare the effect of dynamic (DRT) and isometric (IRT) resistance training on glycemic homeostasis, lipid profile, and nitric oxide (NO) in hemodialysis (HD) patients. Patients were randomly distributed into 3 groups: control (n = 65), DRT (n = 65), and IRT (n = 67). Patients assessed before and after the intervention period were tested for fasting blood glucose, glycated hemoglobin, oral glucose tolerance test, insulin resistance, lipid profile, leptin, insulin, adiponectin, C-reactive protein, and NO . Patients underwent to strength and body composition assessments. Subjects allocated in both DRT and IRT groups took part in a 24-week resistance training program, 3 times per week. Each training session was approximately 1 hour before dialysis and consisted of 3 sets of 8-12 repetitions at low intensity. Total workload was higher in the DRT as compared with the IRT. This heightened workload related to better glycemic homeostasis in HD patients as measured by regulation of insulin, adiponectin, and leptin, while improveing triglycerides, free-fat mass, and muscle strength. Additionally, NO levels were increased in the DRT group. NO was significantly correlated with glucose intolerance (r = -0.42, p = 0.0155) and workload (r = 0.46, p = 0.0022). The IRT group only improved strength (p < 0.05). Twenty-four weeks of DRT improved glycemic homeostasis, lipid profile, and NO in HD patients. Although IRT seems to play an important role in increasing strength, DRT might be a better choice to promote metabolic adjustments in HD patients. Clinical trial: http://www.ensaiosclinicos.gov.br/rg/RBR-3gpg5w. Novelty: DRT might be a better choice for metabolic improvements in patients with chronic kidney disease (CKD). Exercise-training might treat metabolic imbalance in CKD patients.

Disturbances in Insulin-Glucose Metabolism in Patients With Advanced Renal Disease With and Without Diabetes

CONTEXT

Use of insulin in patients with diabetes and advanced chronic kidney disease (CKD; stages 4 to 5) is challenging and shows great variability among individuals. We explored the mechanisms underlying this variability.

EVIDENCE ACQUISITION

PubMed was searched for articles in English from 1960 to 2018 for advanced CKD and diabetes, glucose and insulin metabolism, insulin clearance, secretion and resistance, plasma insulin concentration, glycemic control, hypoglycemia, insulin dosage, and continuous glucose monitoring (CGM) in CKD.

EVIDENCE SYNTHESIS

The evidence shows that in most patients the daily dose of insulin needs to be significantly reduced with a high degree of variability; in some the dose remains unchanged, and rarely it is increased. The premise that the marked reduction in insulin requirement is essentially attributable to decreased insulin clearance by kidneys leading to prolongation of its plasma half-life, elevated blood insulin concentration, and hypoglycemia is not entirely correct. Other factors including decreases in food intake, insulin secretion, insulin clearance by peripheral tissues, and renal gluconeogenesis play important roles. There is also heightened resistance to insulin due to metabolic acidosis, uremic toxins, inflammatory state, and vitamin D deficiency. Importantly, the magnitude of changes in each of these factors varies between individuals with the same degree of CKD.

CONCLUSIONS

In the presence of diabetes with advanced CKD, the insulin regimen should be individualized based on knowledge of the daily glucose patterns. The use of CGM is promising for safer glycemic control in patients with advanced CKD and diabetes and helps prevent extremes of hypoglycemia and hyperglycemia.

Insulin resistance in chronic kidney disease

This review provides an overview of insulin resistance (IR) in patients with chronic kidney disease (CKD). IR is a pathological state in which target tissues fail to respond normally to insulin. IR is understood as a consequence of CKD and its prevalence rises particularly in advanced CKD stages. Mechanisms leading to IR are complex and multifactorial, involving post-receptor signaling defects, unhealthy lifestyles, metabolic acidosis, inflammation, oxidative stress, vitamin D deficiency, anemia, and uremic toxicity, as shown by human and experimental studies over the last 30 years. Whereas hyperinsulinemic euglycemic clamp is the gold standard, it is unpractical at the bedside, and either estimated IR indices by fasting glucose or insulin and oral glucose tolerance tests (OGTT) provide satisfactory estimates of IR also in patients with CKD. IR is likely to play a key role in the development of cardiometabolic complications, but not all studies associate IR with the risk of cardiovascular events and death. Various interventions at the level of lifestyle modifications, adaptations in dialysis therapy (such as use of icodextrin based solutions) and pharmacological strategies such as thiazolidinediones or vitamin D therapy may improve IR in patient with CKD.

Inflammation and Peritoneal Dialysis

Inflammation is one of the well-recognized nontraditional risk factors that contributes to the excessive cardiovascular mortality in peritoneal dialysis (PD) patients. Serum C-reactive protein and interleukin-6 levels are common surrogate markers used to measure inflammatory burden and predict adverse clinical outcomes in PD patients. Causes of inflammation are complex and can be categorized into factors related to a decrease in renal function and factors related to dialysis. They interact with each other and finally result in systemic and intraperitoneal inflammation. This review discusses the various causes and clinical implications of inflammation in PD patients. More importantly, potential therapeutic options that target the underlying pathogenic mechanisms are explored.

Transcriptomics: A Step behind the Comprehension of the Polygenic Influence on Oxidative Stress, Immune Deregulation, and Mitochondrial Dysfunction in Chronic Kidney Disease

Chronic kidney disease (CKD) is an increasing and global health problem with a great economic burden for healthcare system. Therefore to slow down the progression of this condition is a main objective in nephrology. It has been extensively reported that microinflammation, immune system deregulation, and oxidative stress contribute to CKD progression. Additionally, dialysis worsens this clinical condition because of the contact of blood with bioincompatible dialytic devices. Numerous studies have shown the close link between immune system impairment and CKD but most have been performed using classical biomolecular strategies. These methodologies are limited in their ability to discover new elements and enable measuring the simultaneous influence of multiple factors. The “omics” techniques could overcome these gaps. For example, transcriptomics has revealed that mitochondria and inflammasome have a role in pathogenesis of CKD and are pivotal elements in the cellular alterations leading to systemic complications. We believe that a larger employment of this technique, together with other “omics” methodologies, could help clinicians to obtain new pathogenetic insights, novel diagnostic biomarkers, and therapeutic targets. Finally, transcriptomics could allow clinicians to personalize therapeutic strategies according to individual genetic background (nutrigenomic and pharmacogenomic). In this review, we analyzed the available transcriptomic studies involving CKD patients.

Measurement and Correlation of Indices of Insulin Resistance in Patients on Peritoneal Dialysis

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BACKGROUND

Insulin resistance (IR) is common in maintenance dialysis patients and is associated with excess mortality. Hyperinsulinemic euglycemic glucose clamp (HEGC) is the gold standard for measuring IR. There are limited studies using HEGC for comparison to other indirect indices of IR in peritoneal dialysis (PD) patients, nor have there been direct comparisons between patients receiving PD and those on maintenance hemodialysis (MHD) with regard to severity of IR, methods of measurement, or factors associated with the development of IR. ♦

METHODS

This is a cross-sectional, single-center study performed in 10 prevalent PD patients of median age 48 years (range 41 - 54); 50% were female and 60% were African American. Insulin resistance was assessed by HEGC (glucose disposal rate [GDR]), homeostatic model assessment of IR (HOMA-IR), HOMA-IR corrected by adiponectin (HOMA-AD), leptin adiponectin ratio (LAR), quantitative insulin sensitivity check index (QUICKI), McAuley's index, and oral glucose tolerance test (OGTT) at each time point for a total of 18 studies. Retrospective analysis compared this cohort to 12 hemodialysis patients who had previously undergone similar testing. ♦

RESULTS

The median GDR was 6.4 mg/kg/min (interquartile range [IQR] 6.0, 7.8) in the PD cohort compared with the MHD group, which was 5.7 mg/kg/min (IQR 4.3, 6.6). For both the PD and MHD cohorts, the best predictors of GDR by HEGC after adjusting for age, gender, and body mass index (BMI), were HOMA-AD (PD: r = -0.69, p = 0.01; MHD: r = -0.78, p = 0.03) and LAR (PD: r = -0.68, p < 0.001; MHD: r = -0.65, p = 0.04). In both groups, HOMA-IR and QUICKI failed to have strong predictive value. Eight of 10 PD patients had at least 1 abnormal OGTT, demonstrating impaired glucose tolerance. ♦

CONCLUSIONS

Insulin resistance is highly prevalent in PD patients. The adipokine based formulas, HOMA-AD and LAR, correlated well in both the PD and MHD populations in predicting GDR by HEGC, outperforming HOMA-IR. The use of these novel markers could be considered for large-scale, epidemiological outcome studies.

Ketoacid Supplementation Partially Improves Metabolic Parameters in Patients on Peritoneal Dialysis

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BACKGROUND

A low protein diet supplemented with ketoacids has been shown to improve the metabolic profile, including insulin resistance, in patients with chronic kidney disease (CKD), but whether ketoacids alone exert similar effects is unknown. In this prospective randomized controlled trial, we aimed to evaluate the effects of ketoacid supplementation on insulin resistance, systemic inflammation, oxidative stress and endothelial dysfunction among 100 CKD patients undergoing peritoneal dialysis (PD). ♦

METHODS

Patients from one Chinese PD center were randomly assigned to take ketoacids (12 tablets per day) (n = 50) versus a control group (n = 50) for 6 months in an open-label parallelarm design. Daily protein intake of 0.8 - 1.2 g/kg/d and daily energy intake of 25 - 35 kcal/kg/d was prescribed to both groups. Insulin resistance was evaluated using homeostatic model assessment (HOMA-IR) index as the primary outcome. We assessed systemic inflammation using high-sensitive C-reactive protein (hs-CRP) and interleukin-6 (IL-6), oxidative stress using plasma oxidized low density lipoprotein (oxLDL), adipokines using leptin and adiponectin and endothelial dysfunction using serum soluble intercellular adhesion molecule-1 (sICAM) and soluble vascular adhesion molecule-1 (sVCAM) as secondary outcomes. ♦

RESULTS

There were no significant differences in baseline characteristics between the 2 groups except a slightly higher age in patients assigned to the intervention. A total of 89% of participants completed the 6-month intervention. There was no significant difference in the change of HOMA-IR values from baseline between groups after adjusting for baseline age, gender, body mass index and HOMA-IR. For secondary outcomes, hs-CRP varied significantly between groups (p = 0.02), increasing over time for the control group while remaining stable for the ketoacid group. Similarly, the leptin/adiponectin ratio (LAR) differed between groups (p < 0.001), remaining stable in the ketoacid group but increasing in the control group. ♦

CONCLUSION

Ketoacid therapy administered for 6 months had no effect on HOMA-IR but resulted in improvements in hs-CRP and LAR, suggesting metabolic benefit. Future studies are needed to confirm these results and any potential benefit in vascular health of PD patients.

Insulin resistance as a therapeutic target for chronic kidney disease

Insulin resistance (IR) is a prevalent metabolic feature in chronic kidney disease (CKD). Postreceptor insulin-signaling defects have been observed in uremia. A decrease in the activity of phosphatidylinositol 3-kinase appears critical in the pathophysiology of CKD-associated IR. Lipotoxicity due to ectopic accumulation of lipid moieties has recently emerged as another mechanism by which CKD and/or associated metabolic disorders may lead to IR through impairment of various insulin-signaling molecules. Metabolic acidosis, anemia, excess of fat mass, inflammation, vitamin D deficiency, adipokine imbalance, physical inactivity, and the accumulation of nitrogenous compounds of uremia all contribute to CKD-associated IR. The clinical impacts of IR in this setting are numerous, including endothelial dysfunction, increased cardiovascular mortality, muscle wasting, and possibly initiation and progression of CKD. This is why IR may be a therapeutic target in the attempt to improve outcomes in CKD. General measures to improve IR are directed to counteract causal factors. The use of pharmaceutical agents such as inhibitors of the renin-angiotensin system may improve IR in hypertensive and CKD patients. Pioglitazone appears a safe and promising therapeutic agent to reduce IR and uremic-associated abnormalities. However, interventional studies are needed to test if the reduction and/or normalization of IR may actually improve outcomes in these patients.

Pioglitazone improves fat distribution, the adipokine profile and hepatic insulin sensitivity in non-diabetic end-stage renal disease subjects on maintenance dialysis: a randomized cross-over pilot study

Background

Fat redistribution, increased inflammation and insulin resistance are prevalent in non-diabetic subjects treated with maintenance dialysis. The aim of this study was to test whether pioglitazone, a powerful insulin sensitizer, alters body fat distribution and adipokine secretion in these subjects and whether it is associated with improved insulin sensitivity.

Trial Design

This was a double blind cross-over study with 16 weeks of pioglitazone 45 mg vs placebo involving 12 subjects.

Methods

At the end of each phase, body composition (anthropometric measurements, dual energy X-ray absorptometry (DEXA), abdominal CT), hepatic and muscle insulin sensitivity (2-step hyperinsulinemic euglycemic clamp with 2H2-glucose) were measured and fasting blood adipokines and cardiometabolic risk markers were monitored.

Results

Four months treatment with pioglitazone had no effect on total body weight or total fat but decreased the visceral/sub-cutaneous adipose tissue ratio by 16% and decreased the leptin/adiponectin (L/A) ratio from 3.63×10⁻³ to 0.76×10⁻³. This was associated with a 20% increase in hepatic insulin sensitivity without changes in muscle insulin sensitivity, a 12% increase in HDL cholesterol and a 50% decrease in CRP.

Conclusions/Limitations

Pioglitazone significantly changes the visceral-subcutaneous fat distribution and plasma L/A ratio in non diabetic subjects on maintenance dialysis. This was associated with improved hepatic insulin sensitivity and a reduction of cardio-metabolic risk markers. Whether these effects may improve the outcome of non diabetic end-stage renal disease subjects on maintenance dialysis still needs further evaluation.

Trial Registration

ClinicalTrial.gov NCT01253928

Correction of metabolic acidosis in hemodialysis: consequences on serum leptin and mineral metabolism

PURPOSE

Hyperleptinemia and metabolic acidosis (MA) are frequently observed in patients on hemodialysis (HD). While the role of leptin in patients on HD is not completely understood, HD only partially corrects MA. Both leptin and acidosis have effect on bone disease. The goal of the present study was to evaluate the effects of MA correction on chronic kidney disease-mineral and bone disorder laboratory parameters and leptin levels.

METHODS

Forty-eight patients on HD, aged 43±19 years, were prospectively studied. Individual adjustments in the bicarbonate dialysate concentration were made to maintain pre-dialysis concentration≥22 mEq/l. Blood gas analysis was done monthly for 4 months (M1-M4).

RESULTS

From M0 to M4, serum albumin increased (from 3.5 ±0.3 to 4.0±0.3 g/l, p<0.0001) while β2 microglobulin decreased (from 27.6±8.3 to 25.8±6.8 µg/ml, p=0.025). Serum leptin decreased in all but three patients, as well as leptin/adiponectin ratio (p<0.0001). There was a decrease in ionized serum calcium (from 5.0±0.5 to 4.7±0.5 mg/dl, p =0.002) and an increase in parathyroid hormone (PTH) [from 191 (85, 459) to 446 pg/ml (212, 983), p<0.0001] and in serum phosphate (from 5.4±1.4 to 5.8±1.1 mg/dl, p=0.048).

CONCLUSION

MA correction in HD patients can decrease leptin, an atherogenic marker. The impact of such treatment extends to uremic bone disease, as decrease in serum calcium and increase in PTH. However, this could be an undesirable effect because it may aggravate a secondary hyperparathyroidism. Whether the reduction in leptin levels has impact on outcomes in patients on hemodialysis deserves further investigation.

Leptin as an uremic toxin: Deleterious role of leptin in chronic kidney disease

White adipose tissue secretes a large variety of compounds named adipokines amongst which, leptin exhibits pleiotropic metabolic actions. Leptin is an anorexigenic hormone, secreted in proportion of fat mass, with additional effects on the regulation of inflammation, cardiovascular system, immunity, hematopoiesis and bone metabolism. Chronic kidney disease (CKD) is characterized by an increase of plasma leptin concentration that may be explained by a lack of renal clearance. Hyperleptinemia plays a key role in the pathogenesis of complications associated with CKD such as cachexia, protein energy wasting, chronic inflammation, insulin resistance, cardiovascular damages and bone complications. Leptin is also involved in the progression of renal disease through its pro-fibrotic and pro-hypertensive actions. Most of the adverse effects of leptin have been documented both experimentally and clinically. Leptin may therefore be considered as an uremic toxin in CKD. The aim of this review is to summarize the pathophysiological and clinical role of leptin in in vitro studies, experimental models, as well as in patients suffering from CKD.

The peptidic middle molecules: is molecular weight doing the trick?

Chronic kidney disease (CKD) is characterized by a gradual endogenous intoxication caused by the progressive accumulation of bioactive compounds that in normal conditions would be excreted and/or metabolized by the kidney. Uremic toxicity now is understood as one of the potential causes for the excess of cardiovascular disease and mortality observed in CKD. An important family of uremic toxins is that of the peptidic middle molecules, with a molecular weight ranging between 500 and 60,000 Da, which makes them, as a consequence, difficult to remove in the process of dialysis unless the dialyzer pore size is large enough. This review provides an overview of the main and best-characterized peptidic middle molecules and their role as potential culprits of the cardiometabolic complications inherent to CKD patients.

A longitudinal study of nutritional and inflammatory status in patients on dialysis

OBJECTIVE

Several anthropometric, laboratory and bioelectrical impedance parameters of nutritional status and inflammation are often used as prognostic indices in patients on dialysis. Their longitudinal assessment is necessary for the estimation of their true prognostic value. We aim to estimate this prognostic value in better-nourished dialysis patients, which are commonly under-represented in pertinent studies.

METHODS

The design is a prospective case series. Pertinent parameters were studied three times during a 20-month period in 47 haemodialysis (HD) and 27 peritoneal dialysis (PD) patients with a low malnutrition-inflammation score (MIS). Mortality rate was assessed three years after the initial evaluation. Correlation coefficients were calculated between mortality rate, the studied parameters and their alteration.

RESULTS

Serum albumin of less than 40 g/l was strongly correlated with mortality risk. The alteration of studied parameters during a short period of time does not allow for long-term prediction of mortality risk.

CONCLUSION

Serum albumin had the strongest predictive value of all the pertinent parameters in the study. Thus, better conjugate clinical and laboratory measurements should be developed for patients on PD, as well as for those with a relatively low MIS.

Insulin resistance and protein metabolism in chronic hemodialysis patients

OBJECTIVE

Loss of lean body mass (sarcopenia) is associated with increased morbidity and mortality in patients receiving chronic hemodialysis (CHD). Insulin resistance (IR), which is highly prevalent in patients receiving CHD, has been proposed to play a critical role in the development of sarcopenia. The aim of this study was to examine the effect of IR on amino acid metabolism in patients receiving CHD.

DESIGN

This was a cross-sectional study.

SUBJECTS

The study included 12 prevalent (i.e., patients that have been on dialysis for more than 90 days) African American patients receiving CHD.

METHODS

IR was measured as glucose disposal rate (GDR) determined from hyperinsulinemic euglycemic clamp (HGEC) studies performed 3 consecutive times. Plasma amino acid (AA) concentrations were measured by real-time high-performance liquid chromatography (HPLC) throughout the clamp study. The primary outcome was percentage change in leucine concentrations during the clamp study. The main predictor was the GDR measured simultaneously during the HGEC studies. Mixed model analysis was used to account for repeated measures.

RESULTS

All individual AA concentrations declined significantly in response to high-dose insulin administration (P < .001). There was a significant direct association between GDR by HECG studies and the percentage change in leucine concentration (P = .02). Although positive correlations were observed between GDR values and concentration changes from baseline for other AAs, these associations did not reach statistical significance.

CONCLUSIONS

Our results suggest that the severity of IR of carbohydrate metabolism is associated with a lesser decline in plasma leucine concentrations, suggesting a similar resistance to protein anabolism. Insulin resistance represents a potential mechanism for sarcopenia commonly observed in patients receiving CHD.

A pilot study of active vitamin D administration and insulin resistance in African American patients undergoing chronic hemodialysis

OBJECTIVE

Insulin resistance (IR) is associated with increased cardiovascular risk in multiple patient populations, including those undergoing chronic hemodialysis (CHD). Active vitamin D deficiency has been proposed to play a role in the extent of IR observed in patients with CHD. We postulated that administration of paracalcitol, an active vitamin D medication, influences IR in patients with CHD.

DESIGN AND METHODS

This was a pilot randomized controlled trial. Ten prevalent CHD patients receiving a stable dose of paracalcitol were recruited. Paracalcitol was withheld for 8 weeks in all patients (phase I). Parathyroid hormone levels were managed with the calcium-sensing receptor agonist cinacalcet. At week 8, patients were randomized to continue cinacalcet or to restart paracalcitol for 8 weeks (phase II). The primary outcome was the change in IR measured by the glucose disposal rate (GDR) using hyperinsulinemic euglycemic clamp (HEGC) method. Secondary outcomes included changes in IR between groups in indirect indices of IR, biomarkers of inflammation, and adipokine levels.

RESULTS

The mean age was 49 years (range, 46-57 years) and 40% of patients were women. There was no detectable change in the GDR at the end of phase I (P = .7) when compared with baseline values. There was also no statistically significant difference in GDR between groups at the end of phase II (P = .9). No changes were observed in indirect indices of IR, adipokine levels, or biomarkers of inflammation in either phase.

CONCLUSION

The results of this pilot study suggest that withdrawal of paracalcitol over 8 to 16 weeks and replacement for 8 weeks after withdrawal does not influence IR measured by HEGC in patients receiving CHD.

Leptin/adiponectin ratio is an independent predictor of mortality in nondiabetic peritoneal dialysis patients

BACKGROUND

The leptin/adiponectin (L/A) ratio has been suggested to be an atherosclerotic index for diabetic patients and a useful marker of insulin resistance in patients with and without diabetes. Even though end-stage renal disease (ESRD) patients on peritoneal dialysis (PD) are well characterized by abnormal adipocytokine metabolism, the significance of alterations in the L/A ratio is largely unexplored in these patients. In this prospective study, we investigated the associations of leptin, adiponectin, and the L/A ratio with clinical outcomes in nondiabetic PD patients.

METHODS

The study included 131 stable nondiabetic ESRD patients who had been on PD for more than 3 months. Serum leptin and adiponectin levels were determined at baseline. Mortality was evaluated over a 5-year follow-up period.

RESULTS

During the follow-up period, 22 patients died (16.8%), including 10 (45.5%) as a result of cardiovascular disease. The L/A ratio showed a significant positive correlation with body mass index [BMI (r = 0.47, p < 0.001)], high-sensitivity C-reactive protein (r = 0.32, p < 0.001), and triglycerides (r = 0.43, p < 0.001). In addition, we observed significant inverse correlations between the L/A ratio and percentage lean body mass (r = -0.30, p = 0.001) and high-density lipoprotein cholesterol (r = -0.31, p = 0.001). In contrast to individual leptin and adiponectin levels, the L/A ratio was found to be independently associated with an increased mortality risk (relative risk: 1.15; 95% confidence interval: 1.05 to 1.27; p = 0.003) even after adjustments for age and BMI.

CONCLUSIONS

The L/A ratio might be better related to patient outcomes than adipocytokines are individually in nondiabetic patients undergoing PD.

Adipokines as uremic toxins

The adipose tissue has pleiotropic functions far beyond the mere storage of energy, and it secretes a number of hormones and cytokines, called adipokines, which have biological effects that impact heath and disease. Adipokines are markedly elevated in the plasma of uremic patients, mainly due to decreased renal excretion. They have pluripotent signaling effects on inflammation/oxidative stress (leptin, adiponectin, resistin), protein-energy wasting (leptin, adiponectin), insulin signaling (adiponectin, leptin, visfatin), endothelial dysfunction (visfatin), and vascular damage (adiponectin, leptin, resistin), which are prevalent in uremic patients. Obesity superimposed to uremia may further aggravate hyperadipokinemia, with the exception of adiponectinemia, which is mitigated by adiposity. Among adipokines and until more data become available, only leptin may be considered as a full uremic toxin owing to adverse effects on protein-energy wasting, cardiovascular damage, inflammation, and the immune system, which have been documented both clinically and experimentally. Resistin and visfatin display some features of uremic toxins, but more data are needed to consider these adipokines as true uremic toxins. In contrast, high levels of adiponectin and chemerin seen in uremia appear to be beneficial. Further research is needed to investigate whether selective removal of leptin, resistin, and visfatin and increments of adiponectin and chemerin levels may have clinical relevance in uremic patients.

A study of the clinical and biochemical profile of peritoneal dialysis fluid low in glucose degradation products

OBJECTIVE

Although peritoneal dialysis (PD) is a widely accepted form of renal replacement therapy, concerns remain regarding the bioincompatible nature of standard PD fluid (PDF). Short-term studies of new biocompatible PDFs low in glucose degradation products (GDPs) reveal divergent results with respect to peritoneal integrity.

METHODS

We studied 125 patients on maintenance PD who were assigned, by simple randomization, to receive either conventional or low-GDP PDF at PD initiation. Parameters of dialysis adequacy and peritoneal transport of small solutes were determined at initiation and after a period of maintenance PD at the time when serum and overnight effluent dialysate were simultaneously collected and assayed for various cytokines, chemokines, adipokines, and cardiac biomarkers. All patients were further followed prospectively for an average of 15 months from the day of serum and effluent collection to determine patient survival and cardiovascular events.

RESULTS

Patients treated with conventional or low-GDP PDF were matched for sex, age, duration of dialysis, dialysis adequacy, and incidence of cardiovascular disease or diabetes. After an average of 2.3 years of PD treatment, the weekly total and peritoneal creatinine clearance, and the total and peritoneal Kt/V were comparable in the groups. However, urine output was higher in patients using low-GDP PDF despite there having been no difference between the groups at PD initiation. Patients using low-GDP PDF also experienced a slower rate of decline of residual glomerular filtration and urine output than did patients on conventional PDF. Compared with serum concentrations, effluent concentrations of tumor necrosis factor α, hepatocyte growth factor, macrophage migration inhibitory factor, interleukins 8 and 6, C-reactive protein, and leptin were found to be higher in both groups of patients after long-term PD, suggesting that the peritoneal cavity was the major source of those mediators. Compared with patients on low-GDP PDF, patients on conventional fluid showed elevated leptin and reduced adiponectin levels in serum and effluent. The effluent concentration of interleukin 8 was significantly lower in patients using low-GDP PDF. The survival rate and incidence of cardiovascular complications did not differ between these groups after maintenance PD for an average of 3.6 years.

CONCLUSIONS

It appears that low-GDP PDF results in an improvement of local peritoneal homeostasis through a reduction of chronic inflammatory status in the peritoneum.

Time-dependent associations between total sodium removal and mortality in patients on peritoneal dialysis

PURPOSE

To determine if the time-dependent association between total sodium removal and mortality in patients on continuous ambulatory peritoneal dialysis (CAPD) is confounded by markers of diet and nutrition.

METHODS

The study enrolled 305 incident patients who started CAPD between July 2002 and February 2007. All patients were followed until death or censoring in February 2008. Demographics, blood pressure, and markers of volume and inflammation were collected at baseline. Biochemistry, fluid and solute removal, and diet and nutrition parameters were collected quarterly and thus calculated as time-averaged values.

RESULTS

Mean age of the study patients was 59.4 years, 42.3% were men, and 40.3% had diabetes. During the 31.4-month follow-up, 74 patients died. The time-averaged daily total sodium removal (TSR) in the overall cohort was 2.67 g (range: 2.02 g-3.47 g). Participants with a high time-averaged TSR tended to experience higher fluid, sodium, urea, and creatinine removal, mainly as a result of better residual renal function (RRF). They also had a higher nutrient intake and a higher lean body mass. Time-dependent TSR was an independent predictor of death, including when adjusted for age, Charlson index, time-dependent hemoglobin, RRF, and peritoneal transport rate (hazard ratio: 0.84; 95% confidence interval: 0.70 to 1.00; p=0.05), but the predictive effect disappeared in multivariate models after further individual adjustment for time-dependent total energy intake, total protein intake, serum albumin, and lean body mass. By contrast, the predictive effect did not disappear if the only adjustment was for time-dependent RRF.

CONCLUSIONS

The time-dependent association between TSR and mortality in patients on peritoneal dialysis can be largely explained by diet and nutrition parameters.

Fighting protein-energy wasting in chronic kidney disease: a challenge of complexity

Chronic uremia is often characterized by wasting of muscle and fat mass, which has been defined as protein-energy wasting (PEW), and is responsible for substantial worsening of patient outcome in terms of morbidity and mortality, mostly from cardiovascular events. Despite major advances in patient treatment, nutritional outcome in patients with end-stage renal disease has not improved substantially in recent years. Extensive research in this field has provided plausible explanations for this limitation by indicating that the pathogenesis of PEW in kidney disease is complex and multifactorial. Complexity involves underlying metabolic alterations, including inflammation, oxidative stress, and insulin resistance. In addition, patient heterogeneity is increasing with large numbers of obese individuals as a result of the ongoing obesity epidemics. Several tissues are involved in cross-talk and contribute to metabolic derangements, including adipose tissue, the gut, and the central nervous system, with novel mediators including the gastric hormone ghrelin. Acknowledging its complex pathogenesis may favor the development of novel and more effective therapeutic tools for PEW. These should ideally be effective in treating the underlying common mechanisms of wasting, which appear to include oxidative stress, inflammation, and insulin resistance.

A comparison of novel and commonly-used indices of insulin sensitivity in African American chronic hemodialysis patients

BACKGROUND

Insulin resistance (IR) is highly prevalent in chronic hemodialysis (CHD) patients and is associated with poor cardiovascular outcomes. Hyperinsulinemic euglycemic glucose clamp (HEGC) is the gold standard for measuring IR. The comparison of commonly-used indirect indices of IR to HEGC has not been adequately performed in this population. Furthermore, the validity of newly proposed adipokine-based IR indices has not been explored.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This is an observational study performed in a single center, involving 12 prevalent CHD patients (50 ± 9 years old, 100% African American, 33% women, body mass index of 34.4 ± 7.6 kg/m(2)) who were studied three consecutive times. IR was assessed by HEGC (glucose-disposal rate [GDR]), homeostatic model assessment of IR (HOMA-IR), HOMA-IR corrected by adiponectin (HOMA-AD), leptin adiponectin ratio (LAR), QUICKI, and the McAuley's index at each time point.

RESULTS

Eighty-three percent of the subjects displayed either glucose intolerance or overt insulin resistance by HEGC (GDR median, 5.71; interquartile range [IQR], 4.16, 6.81). LAR and HOMA-AD were the best correlates of IR measured by HEGC (r=-0.72, P<0.001, and -0.67, P<0.001), respectively. Fat percentage, interleukin-6, and adipokines (leptin, adiponectin, and resistin) were strongly associated with GDR. HEGC, LAR, and HOMA-AD had the best intraclass correlation coefficients.

CONCLUSION

IR is common in CHD patients. Adipokine-based indices are the best correlates of IR measurements by HEGC. HOMA-IR and QUICKI are reasonable alternatives. Use of these indices may allow better detection of alterations in insulin sensitivity in CHD patients.

Insulin resistance and lower plasma adiponectin increase malignancy risk in nondiabetic continuous ambulatory peritoneal dialysis patients

End-stage renal disease patients have a higher risk for developing cancer. Although several causes for this increased risk have been proposed, the risk factors for cancer development in this population have not been elucidated. The aim of this study was to determine whether metabolic derangements, including insulin resistance and altered adipokines, increase the risk of developing malignancies in peritoneal dialysis (PD) patients, who are vulnerable to metabolic disorders because of excessive glucose absorbed from the dialysate. Study subjects comprised 106 nondiabetic PD patients who had been on PD for a minimum of 3 months with no overt malignancy. Baseline anthropometry, fasting glucose, insulin, and adiponectin were measured. The development of malignancy was evaluated during the follow-up period. During the mean follow-up of 47.0 ± 23.7 months, malignancy occurred in 15 patients (14.2%). The most common site of cancer was the kidney (26.7%), followed by thyroid (13.3%) and stomach (13.3%). Baseline insulin levels and homeostasis model assessment of insulin resistance were significantly higher, whereas plasma adiponectin levels were significantly lower, in patients who developed malignancy. Cox proportional hazards analysis revealed that insulin levels, homeostasis model assessment of insulin resistance, and lower adiponectin were independent predictors of malignancy. These findings demonstrate that insulin resistance and lower adiponectin levels could be risk factors for malignancy in nondiabetic PD patients.

Insulin resistance and protein energy metabolism in patients with advanced chronic kidney disease

Insulin resistance (IR), the reciprocal of insulin sensitivity is a known complication of advanced chronic kidney disease (CKD) and is associated with a number of metabolic derangements. The complex metabolic abnormalities observed in CKD such as vitamin D deficiency, obesity, metabolic acidosis, inflammation, and accumulation of "uremic toxins" are believed to contribute to the etiology of IR and acquired defects in the insulin-receptor signaling pathway in this patient population. Only a few investigations have explored the validity of commonly used assessment methods in comparison to gold standard hyperinsulinemic hyperglycemic clamp technique in CKD patients. An important consequence of insulin resistance is its role in the pathogenesis of protein energy wasting, a state of metabolic derangement characterized by loss of somatic and visceral protein stores not entirely accounted for by inadequate nutrient intake. In the general population, insulin resistance has been associated with accelerated protein catabolism. Among end-stage renal disease (ESRD) patients, enhanced muscle protein breakdown has been observed in patients with Type II diabetes compared to ESRD patients without diabetes. In the absence of diabetes mellitus (DM) or severe obesity, insulin resistance is detectable in dialysis patients and strongly associated with increased muscle protein breakdown, primarily mediated by the ubiquitin-proteasome pathway. Recent epidemiological data indicate a survival advantage and better nutritional status in insulin-free Type II DM patients treated with insulin sensitizer thiazolidinediones. Given the high prevalence of protein energy wasting in ESRD and its unequivocal association with adverse clinical outcomes, insulin resistance may represent an important modifiable target for intervention in the ESRD population.

Glucose-based peritoneal dialysis solution suppresses adiponectin synthesis through oxidative stress in an experimental model of peritoneal dialysis

OBJECTIVE

Accumulation of visceral fat is one of the major risk factors for the development of cardiovascular disease in peritoneal dialysis (PD) patients. Adiponectin, an adipokine commonly regarded as a negative indicator of metabolic disease, is reported to be downregulated in its gene level in end-stage renal disease patients. Since excessive fat deposit is involved in increased reactive oxygen species (ROS), PD solution (PDS) may contribute to ROS production, resulting in dysregulation of adiponectin. In this study, we tested our hypothesis that oxidative stress induced by PDS may play a role in the regulation of adiponectin.

METHODS

Commercial PDS containing 3.86% glucose (20 - 30 mL) was administered to SD rats for 12 weeks with and without N-acetylcysteine (NAC; 10 mmol/L). ELISA was used to quantify adiponectin in plasma and spent dialysate. For in vitro studies, fully differentiated 3T3-L1 adipocytes and adipocytes isolated from abdominal fat were treated with a high glucose solution, PDS, and H(2)O(2). Adiponectin levels in the conditioned media were measured by ELISA and immunoblot assays. The mRNA levels of adiponectin in mature adipocytes were examined using real-time RT-PCR.

RESULTS

The levels of adiponectin in plasma and spent dialysate were significantly downregulated by PDS and this effect was suppressed by NAC. In 3T3-L1 adipocytes, adiponectin secretion was inhibited by 50 mmol/L glucose, PDS diluted 2-fold, and H(2)O(2) (200 μmol/L). In addition, H(2)O(2) downregulated expression of adiponectin mRNA and secretion of adiponectin oligomer complexes.

CONCLUSIONS

Our data suggest that ROS induced by conventional glucose-based PDS may contribute to pathophysiological changes in abdominal fat and downregulate adiponectin secreted from adipocytes during long-term PD.

Adipokines, endothelial dysfunction and nutritional status in peritoneal dialysis patients

OBJECTIVE

Adipokines such as leptin and adiponectin are adipocyte-specific secretory proteins that play important roles in the metabolic regulation of body weight, insulin resistance and cardiovascular complications. The relationship between the malnutrition-inflammation complex syndrome and high levels of some adipokines in peritoneal dialysis (PD) patients is still unclear. An association between high body mass index (BMI) and improved survival in PD patients has also been proposed. The purpose of this study was to investigate the levels of plasma adipokines and inflammation and oxidative stress markers in overweight and normal weight PD patients.

MATERIAL AND METHODS

Thirty PD patients (12 M, 18 F; mean age 57.3 ± 16.6 years) were examined and 23 healthy volunteers were included as a control group. The levels of high-sensitivity C-reactive protein (hsCRP), tumour necrosis factor-α, interleukin-6, leptin, the leptin receptor, adiponectin, malondialdehyde/4-hydroxynonenal, oxidized low-density lipoprotein, carbonyl groups and asymmetric dimethylarginine (ADMA) were measured in both groups. The nutritional status of each patient was determined by albumin levels, BMI, percentage of body fat (%F), lean body mass (LBM) and the Subjective Global Assessment (SGA) score. The adequacy of dialysis was estimated by weekly Kt/V measurements.

RESULTS

According to the seven-point SGA scores and the albumin levels, the nutrition status of 15 patients was good (6-7 points), while 15 patients were mildly malnourished (3-5 points). The concentrations of hsCRP, leptin and adiponectin were statistically higher in the PD group than in the control group (p < 0.05). Markers of oxidative stress and inflammation were also higher in the PD group. The adiponectin level was inversely correlated with %F and BMI (Spearman's R = -0.3, p ≤ 0.05) and positively correlated with hsCRP level (R = -0.4). The level of leptin was positively correlated with %F, BMI and LBM (R = 0.4, p ≤ 0.05). Patients with normal BMI values had lower leptin concentrations (50.2 vs 242.8 μg/l) and higher adiponectin levels (30.0 vs 20.3 μg/ml) than overweight patients. The statistical analysis indicated that there were no differences in oxidative stress, inflammation and ADMA concentration between the lean and overweight PD patients.

CONCLUSION

The nutritional status of lean and overweight patients was comparable. Signs of malnutrition were detected in both groups. The severity of chronic inflammation and oxidative stress were not related to BMI in PD patients.

Proinflammatory cytokines, hepatocyte growth factor and adipokines in peritoneal dialysis patients

Chronic inflammation is a well-recognized complication in dialysis patients and a potential role of the adipose tissue as an important tissue of origin contributing to inflammation has been proposed. Stable peritoneal dialysis (PD) patients were enrolled to investigate the relationship between serum levels of proinflammatory cytokines and adipokines. Our results revealed that there was a strong association between high sensitivity C-reactive protein and interleukin (IL)-6 and tumor necrosis factor-alpha (TNF-alpha) but not with IL-10 and IL-18. IL-6 correlated with TNF-alpha, IL-10, and IL-18. No association was found between IL-10 and IL-18. Adiponectin was positively correlated with all proinflammatory cytokines, except IL-10. No significant association was found between resistin and proinflammatory cytokines. Hepatocyte growth factor (HGF) was directly related to proinflammatory cytokines but not with adipokines. The presence of residual kidney function (RKF) affected IL-6, TNF-alpha, and HGF levels. The peritoneal transport property did not influence inflammatory cytokine and adipokine levels. In conclusion, there was a close relationship between proinflammatory cytokines and adipokines. HGF correlated with proinflammatory cytokines but not with adipokines. The PD-related factors such as RKF, peritoneal property and dialysis glucose load affected levels of proinflammatory cytokines. Body mass index was an important determinant of leptin and adiponectin in PD patients.

Peritoneal adipocytes and their role in inflammation during peritoneal dialysis

Adipose tissue is a major site of chronic inflammation associated with peritoneal dialysis (PD) frequently complicating peritonitis. Adiposity-associated inflammation plays a significant contributory role in the development of chronic inflammation in patients undergoing maintenance PD. However, the molecular and cellular mechanisms of this link remain uncertain. Adipose tissue synthesizes different adipokines and cytokines that orchestrate and regulate inflammation, insulin action, and glucose metabolism locally and systemically. In return, inflammation retards adipocyte differentiation and further exacerbates adipose dysfunction and inflammation. An understanding of the inflammatory roles played by adipose tissue during PD and the healing mechanism of injured mesothelium will help to devise new therapeutic approach to slow the progression of peritoneal damage during peritoneal dialysis. This article reviews the roles of peritoneal adipose tissue in chronic peritoneal inflammation under PD and in serosal repair during PD.

Reducing cardiometabolic risk in peritoneal dialysis patients: role of the dialysis solution

Peritoneal dialysis (PD) is a well-established form of therapy for stage 5 chronic kidney disease requiring renal replacement therapy. D-Glucose has been used successfully for several decades as the osmotic agent employed in dialysis solutions to achieve adequate fluid removal. The absorption of 100-200 grams of glucose per day has been suggested as potentially increasing cardiometabolic risk, particularly in patients with diabetes. Supporting and undermining evidence for this hypothesis is reviewed, with a focus on the role of glucose absorption in changes in body composition, dyslipidemia, and glycemic control in diabetic PD patients. Clinical strategies to optimize fluid removal while minimizing the metabolic impact of glucose absorption are also discussed.

Icodextrin: an alternative peritoneal dialysis fluid

Peritoneal dialysis is a home dialysis therapy in which a fluid known as dialysate is placed into the patient's peritoneal cavity. The standard dialysate consists of a concentrated dextrose solution. Icodextrin is a glucose polymer that can be substituted for dextrose with avoidance of some of the glucose-dependant effects. The efficacy and safety of this compound was evaluated and compared with the standard dialysate solutions. It seems to be well-tolerated overall and may offer benefits in select populations of patients with kidney failure. This seems to be especially relevant in patients with more permeable peritoneal membranes who are known as 'high-transporters'.