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

Oxidation State in Peritoneal Dialysis in Patients with Type 2 Diabetes Mellitus

End-stage renal disease (ESRD) progression is closely related to oxidative stress (OS). The study objective was to determine the oxidant and antioxidant status in peritoneal dialysis (PD) patients with type 2 diabetes mellitus (DM). An analytical cross-sectional study from the PD program was carried out with 62 patients, 22 with and 40 without DM. Lipoperoxides (LPO) levels in patients with DM, 3.74 ± 1.09 mM/L, and without DM, 3.87 ± 0.84 mM/L were found to increase compared to healthy controls (HC) 3.05 ± 0.58 mM/L (p = 0.006). The levels of the oxidative DNA damage marker (8-OH-dG) were found to be significantly increased in patients with DM, 1.71 ng/mL (0.19-71.92) and without DM, 1.05 ng/mL (0.16-68.80) front to 0.15 ng/mL (0.15-0.1624) of HC (p = 0.001). The antioxidant enzyme superoxide dismutase (SOD) activity was found to be significantly increased in patients with DM, 0.37 ± 0.15 U/mL, and without DM, 0.37 ± 0.17 compared to HC, 0.23 ± 0.05 U/mL (p = 0.038). The activity of the enzyme glutathione peroxidase (GPx) showed a significant increase (p < 0.001) in patients with DM, 3.56 ± 2.18 nmol/min/mL, and without DM, 3.28 ± 1.46 nmol/min/mL, contrary to the activity obtained in HC, 1.55 ± 0.34 nmol/min/mL. In conclusion, we found an imbalance of oxidative status in patients undergoing PD with and without DM through the significant increase in LPO oxidants and the marker of oxidative damage in DNA. The activity of the antioxidant enzymes SOD and GPx were significantly increased in patients with and without DM undergoing PD, possibly in an attempt to compensate for the deregulation of oxidants. Antioxidant enzymes could be promising therapeutic strategies as a complement to the management of chronic kidney diseases.

Comparison of transcriptome between high- and low-marbling fineness in longissimus thoracis muscle of Korean cattle

Objective

This study compared differentially expressed genes (DEGs) between groups with high and low numbers of fine marbling particles (NFMP) in the longissimus thoracis muscle (LT) of Korean cattle to understand the molecular events associated with fine marbling particle formation.

Methods

The size and distribution of marbling particles in the LT were assessed with a computer image analysis method. Based on the NFMP, 10 LT samples were selected and assigned to either high- (n = 5) or low- (n = 5) NFMP groups. Using RNA sequencing, LT transcriptomic profiles were compared between the high- and low-NFMP groups. DEGs were selected at p<0.05 and |fold change| >2 and subjected to functional annotation.

Results

In total, 328 DEGs were identified, with 207 up-regulated and 121 down-regulated genes in the high-NFMP group. Pathway analysis of these DEGs revealed five significant (p<0.05) Kyoto encyclopedia of genes and genomes pathways; the significant terms included endocytosis (p = 0.023), protein processing in endoplasmic reticulum (p = 0.019), and adipocytokine signaling pathway (p = 0.024), which are thought to regulate adipocyte hypertrophy and hyperplasia. The expression of sirtuin4 (p<0.001) and insulin receptor substrate 2 (p = 0.043), which are associated with glucose uptake and adipocyte differentiation, was higher in the high-NFMP group than in the low-NFMP group.

Conclusion

Transcriptome differences between the high- and low-NFMP groups suggest that pathways regulating adipocyte hyperplasia and hypertrophy are involved in the marbling fineness of the LT.

Unfavorable Effects of Peritoneal Dialysis Solutions on the Peritoneal Membrane: The Role of Oxidative Stress

One of the main limitations to successful long-term use of peritoneal dialysis (PD) as a renal replacement therapy is the harmful effects of PD solutions to the structure and function of the peritoneal membrane (PM). In PD, the PM serves as a semipermeable membrane that, due to exposure to PD solutions, undergoes structural alterations, including peritoneal fibrosis, vasculopathy, and neoangiogenesis. In recent decades, oxidative stress (OS) has emerged as a novel risk factor for mortality and cardiovascular disease in PD patients. Moreover, it has become evident that OS plays a pivotal role in the pathogenesis and development of the chronic, progressive injury of the PM. In this review, we aimed to present several aspects of OS in PD patients, including the pathophysiologic effects on the PM, clinical implications, and possible therapeutic antioxidant strategies that might protect the integrity of PM during PD therapy.

Low serum adiponectin level is associated with central arterial stiffness in patients undergoing peritoneal dialysis

Objective:

Adiponectin has antidiabetic, anti-atherosclerotic, and anti-inflammatory functions and protects against vascular damage. Carotid-femoral pulse wave velocity (cfPWV) is a noninvasive method for measuring central artery stiffness, which is known to be associated with cardiovascular disease in peritoneal dialysis (PD) patients. This study was conducted to evaluate the relationship between central arterial stiffness and serum adiponectin levels in PD patients.

Materials and Methods:

Fasting blood samples were obtained from 60 PD patients, and the cfPWV value was measured using a validated tonometry system. In this study, cfPWV values of >10 m/s were used to define the high arterial stiffness group according to the European Society of Hypertension and the European Society of Cardiology guidelines.

Results:

Among 60 patients with PD, 19 patients (31.7%) were included in the high arterial stiffness group. When compared to those in the control group, the high arterial stiffness group patients were older (P = 0.029), had longer PD vintage (P = 0.001), higher diastolic blood pressures (P = 0.030), higher fasting glucose (P = 0.014), and lower serum adiponectin levels (P = 0.001). After multivariable logistic regression analysis, serum adiponectin (odds ratio, 0.612; 95% confidence interval: 0.426–0.879; P = 0.008) was identified as an independent predictor of arterial stiffness. The multivariable regression analysis also showed that the adiponectin level (β = −0.408; adjusted R² change = 0.183; P < 0.001) was negatively associated with cfPWV values in patients undergoing PD.

Conclusion:

Low serum adiponectin level is an independent marker of arterial stiffness in patients undergoing PD.

UA promotes epithelial‑mesenchymal transition in peritoneal mesothelial cells

Long‑term peritoneal dialysis is often limited or interrupted due to the development and progression of peritoneal fibrosis. Accumulating evidence suggests that epithelial‑mesenchymal transition (EMT) is a major component of peritoneal injury associated with peritoneal fibrosis in the end stage of renal disease; however, at present, the underlying mechanisms remain unclear. Thus, in the present study, uric acid (UA)‑induced EMT of peritoneal mesothelial cells was investigated by western‑blot and immunofluorescence staining. The results revealed that peritoneal mesothelial cells stimulated with UA underwent EMT, as demonstrated by the decreased expression of epithelial markers (E‑cadherin) and an increased expression of mesenchymal markers (α‑smooth muscle actin and vimentin). Additionally, it was reported that UA could facilitate the progression of EMT of peritoneal mesothelial cells via EMT transcription pathways, including transforming growth factor‑β1/mothers against decapentaplegic homolog 3 and P38/mitogen‑activated protein kinase by western‑blot and reverse transcription semi‑quantitative polymerase chain reaction. The results of the present study suggest that UA could promote EMT and may contribute to peritoneal chronic disease. Furthermore, the data obtained suggest that the levels of blood UA may account for the development of EMT; thus, lowering the levels of blood UA may be beneficial to inhibit the occurrence and development of peritoneal fibrosis.

Oxidative Stress in Patients Undergoing Peritoneal Dialysis: A Current Review of the Literature

Peritoneal dialysis (PD) patients manifest excessive oxidative stress (OS) compared to the general population and predialysis chronic kidney disease patients, mainly due to the composition of the PD solution (high-glucose content, low pH, elevated osmolality, increased lactate concentration and glucose degradation products). However, PD could be considered a more biocompatible form of dialysis compared to hemodialysis (HD), since several studies showed that the latter results in an excess accumulation of oxidative products and loss of antioxidants. OS in PD is tightly linked with chronic inflammation, atherogenesis, peritoneal fibrosis, and loss of residual renal function. Although exogenous supplementation of antioxidants, such as vitamins E and C, N-acetylcysteine, and carotenoids, in some cases showed potential beneficial effects in PD patients, relevant recommendations have not been yet adopted in everyday clinical practice.

The Relationship Between Body Composition and Bone Quality Measured with HR-pQCT in Peritoneal Dialysis Patients

BACKGROUND

Bone is known to be impaired in chronic kidney disease and dialysis patients. Recent studies have shown that body composition (fat mass and lean mass) may impact bone health. Some of these effects may be related to mediators that are secreted by adipose tissue.

METHODS

The aim of this study was to evaluate the association between body composition (dual x-ray absorptiometry [DEXA]) and adipokines (leptin, adiponectin), with bone density and microarchitecture assessed with high-resolution peripheral quantitative computed tomography (HR-pQCT) in chronic peritoneal dialysis (PD) patients in a single-center prospective study.

RESULTS

Twenty-three patients with a median age of 61 years and body mass index (BMI) of 27 kg/m² were recruited. On univariate analysis, age was negatively associated with total volumetric bone mineral density (vBMD) (r = -0.75, p < 0.01), cortical vBMD (r = -0.85, p < 0.01), and cortical thickness (r = -0.71, p < 0.01). There was a negative association between leptin and cortical thickness (r = -0.48, p = 0.021). Fat mass (FM) was negatively correlated with cortical thickness (r = -0.52, p = 0.012). No association was found between bone parameters and dialysis duration, serum insulin, intact parathyroid hormone, osteocalcin, and adiponectin. The short dialysis vintage could in part explain the lack of correlation with bone parameters. In multivariate analysis, FM was significantly and negatively correlated with total vBMD, cortical and trabecular thickness.

CONCLUSIONS

These data suggest that FM is negatively associated with bone quality in PD patients, supporting a relation between body composition and bone that is independent from other dialysis-associated complications. The relative contribution of the different fat deposits (visceral versus subcutaneous) needs to be assessed in future studies.

Fat tissue and inflammation in patients undergoing peritoneal dialysis

Background

Body weight has been increasing in the general population and is an established risk factor for hypertension, diabetes, and all-cause and cardiovascular mortality. Patients undergoing peritoneal dialysis (PD) gain weight, mainly during the first months of treatment. The aim of this study was to assess the relationship between body composition and metabolic and inflammatory status in patients undergoing PD.

Methods

This was a prospective, non-interventional study of prevalent patients receiving PD. Body composition was studied every 3 months using bioelectrical impedance (BCM^®). We performed linear regression for each patient, including all BCM^® measurements, to calculate annual changes in body composition. Thirty-one patients in our PD unit met the inclusion criteria.

Results

Median follow-up was 26 (range 17–27) months. Mean increase in weight was 1.8 ± 2.8 kg/year. However, BCM^® analysis revealed a mean increase in fat mass of 3.0 ± 3.2 kg/year with a loss of lean mass of 2.3 ± 4.1 kg/year during follow-up. The increase in fat mass was associated with the conicity index, suggesting that increases in fat mass are based mainly on abdominal adipose tissue. Changes in fat mass were directly associated with inflammation parameters such as C-reactive protein (r = 0.382, P = 0.045) and inversely associated with high-density lipoprotein cholesterol (r=−0.50, P = 0.008).

Conclusions

Follow-up of weight and body mass index can underestimate the fat mass increase and miss lean mass loss. The increase in fat mass is associated with proinflammatory state and alteration in lipid profile.

Association of Adiponectin with High-Sensitivity C-Reactive Protein and Clinical Outcomes in Peritoneal Dialysis Patients: A 3.5-Year Follow-Up Study

Introduction

Adiponectin (ADPN), one of most abundant fat-derived biologically active substances, plays an important role in anti-atherosclerotic process. There are conflicting results about the impact of ADPN on cardiovascular (CV) outcomes and mortality, particularly in patients undergoing peritoneal dialysis (PD). Moreover, the relationship between ADPN and inflammatory mediators has been seldom explored in this population. Therefore, we examined the relationship between ADPN and longitudinal high-sensitivity C-reactive protein (hs-CRP) changes and investigated whether ADPN or hs-CRP levels could predict CV outcomes and mortality in prevalent PD patients after comprehensive adjustment of possible confounders.

Methods

In this prospective cohort study, 78 PD patients were enrolled and followed from February 2009 to August 2012. During follow-up, CV events and all-cause mortality were recorded.

Results

The mean baseline ADPN value was 29.46±18.01 μg/ml and duration of PD treatment was 37.76±36.96 months. In multiple linear regression analysis, plasma ADPN levels positively correlated with high-density lipoprotein and negatively associated with hs-CRP, body mass index, D4/D0 glucose, triglyceride, and duration of PD treatment. After stratified by genders, the inverse association between baseline ADPN and hs-CRP was more significant in the female group. The hs-CRP levels were followed up annually and remained significantly lower in the high ADPN group in the first 2 years. Patients were then stratified into two groups according to the median ADPN value (23.8 μg/ml). The results of Kaplan-Meier survival analysis demonstrated less CV events and better survival in high ADPN group. On multivariate Cox regression analysis, only ADPN level (HR: 0.93, 95% CI: 0.88–0.98, p = 0.02), age and history of CV diseases were independent risk factors for future CV events. Furthermore, hs-CRP (HR: 1.11, 95% CI:1.001–1.22, p = 0.04) was identified as independent predictor of all-cause mortality.

Conclusions

Serum hs-CRP levels were consistently lower in the high ADPN group during 2-year follow-up. We also demonstrated the importance of ADPN and hs-CRP in predicting CV events and all-cause mortality in PD population during 3.5-year follow-up.

The cell biology of fat expansion

Adipose tissue is a complex, multicellular organ that profoundly influences the function of nearly all other organ systems through its diverse metabolite and adipokine secretome. Adipocytes are the primary cell type of adipose tissue and play a key role in maintaining energy homeostasis. The efficiency with which adipose tissue responds to whole-body energetic demands reflects the ability of adipocytes to adapt to an altered nutrient environment, and has profound systemic implications. Deciphering adipocyte cell biology is an important component of understanding how the aberrant physiology of expanding adipose tissue contributes to the metabolic dysregulation associated with obesity.

Oxidative DNA damage and mortality in hemodialysis and peritoneal dialysis patients

BACKGROUND AND AIMS

Increased oxidative stress in dialysis patients is thought to contribute to increased mortality; however, confirmatory data are scarce. We analyzed the serum concentration of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of oxidative stress, in relation to mortality in hemodialysis (HD) and peritoneal dialysis (PD) patients.

METHODS

Serum 8-OHdG, interleukin 6 (IL-6), other biochemical markers, Davies comorbidity score, and protein-energy wasting (PEW) were assessed in 303 prevalent patients treated with HD (n = 220; age: 63 ± 14 years) or PD (n = 83; age: 64 ± 14 years). Mortality was assessed after a median follow-up of 31 months.

RESULTS

The median (25th - 75th percentile) concentration of 8-OHdG was higher in HD than in PD patients: 1.3 ng/mL (0.9 - 1.8 ng/mL) versus 0.5 ng/mL (0.4 - 0.6 ng/mL), p < 0.001. The HD modality (standard β = 0.57, p < 0.001) and dialysis vintage (standard β = 0.12, p = 0.02) were independent predictors of serum 8-OHdG in a multivariable linear regression model including age, sex, body mass index, dialysis modality (HD or PD), preceding time on dialysis (dialysis vintage), PEW, comorbidity score, IL-6, and use of angiotensin converting-enzyme inhibitors or angiotensin II receptor blockers or statins. During follow-up, 107 patients died. In multivariable Cox regression models including all 303 patients and adjusted for age, sex, body mass index, dialysis modality, dialysis vintage, and comorbidity score, 8-OHdG was significantly associated with all-cause mortality (adjusted hazard ratio: 1.40; 95% confidence limits: 1.05, 1.87 for 1 standard deviation increase of 8-OHdG). In subgroup analyses according to dialysis modality, 8-OHdG was associated with mortality in HD patients but not in PD patients.

CONCLUSIONS

Oxidative stress as assessed by 8-OHdG is an independent predictor of all-cause mortality in dialysis patients. This association was seen in HD patients, but no such association could be demonstrated for PD patients.

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.