Peritoneal Protein Loss, Inflammation, and Nutrition: Refuting Myths

Peritoneal protein loss (PPL) has been correlated with mortality, malnutrition and inflammation. More recently overhydration was brought to the equation. This study aims to review classic and recent factors associated with PPL. Prevalent and incident peritoneal dialysis (PD) patients were included. Dialysate and serum IL-6 was obtained during PET. Hydration and nutritional status were assessed by bio-impedance. Linear regression and Cox regression were performed. The 78 included patients presented median values of PPL 4.8 g/24 h, serum IL-6: 5.1 pg/mL, and IL-6 appearance rate 153.5 pg/min. Mean extracellular water excess (EWexc) was 0.88 ± 0.94 L, and lean body mass index (LBMI) 17.3 ± 2.4 kg/m2. After mean follow-up of 33.9 ± 29.3 months, 12 patients died. Linear univariable analysis showed positive associations between PPL and small solute transport, body composition (LBMI and EWexc), comorbidities and performing CAPD (vs. cycler). PPL correlated positively with dialysate appearance rate of IL-6, but not with serum IL-6. Linear multivariable analysis confirmed positive association between PPL and EWexc (p = 0.012; 95%CI: 4.162–31.854), LBMI (p = 0.008; 95%CI: 1.720–11.219) and performing CAPD (p = 0.023; 95%CI: 4.375–54.190). In survival analysis, no relationship was found between mortality and PPL. Multivariable Cox regression showed Charlson Comorbidity Index (HR: 1.896, 95%CI: 1.235–2.913), overhydration (HR: 10.034, 95%CI: 1.426–70.587) and lower PPL (HR: 0.576, 95%CI: 0.339–0.978) were predictors for mortality. Overhydration, was a strong predictor of PPL, overpowering variables previously reported as determinants of PPL, namely clinical correlates of endothelial dysfunction or local inflammation. PPL were not associated with malnutrition or higher mortality, emphasizing the importance of volume overload control in PD patients.

Peritoneal Protein Loss, Inflammation, and Nutrition: Refuting Myths

Peritoneal protein loss (PPL) has been correlated with mortality, malnutrition and inflammation. More recently overhydration was brought to the equation. This study aims to review classic and recent factors associated with PPL. Prevalent and incident peritoneal dialysis (PD) patients were included. Dialysate and serum IL-6 was obtained during PET. Hydration and nutritional status were assessed by bio-impedance. Linear regression and Cox regression were performed. The 78 included patients presented median values of PPL 4.8 g/24 h, serum IL-6: 5.1 pg/mL, and IL-6 appearance rate 153.5 pg/min. Mean extracellular water excess (EWexc) was 0.88 ± 0.94 L, and lean body mass index (LBMI) 17.3 ± 2.4 kg/m2. After mean follow-up of 33.9 ± 29.3 months, 12 patients died. Linear univariable analysis showed positive associations between PPL and small solute transport, body composition (LBMI and EWexc), comorbidities and performing CAPD (vs. cycler). PPL correlated positively with dialysate appearance rate of IL-6, but not with serum IL-6. Linear multivariable analysis confirmed positive association between PPL and EWexc (p = 0.012; 95%CI: 4.162-31.854), LBMI (p = 0.008; 95%CI: 1.720-11.219) and performing CAPD (p = 0.023; 95%CI: 4.375-54.190). In survival analysis, no relationship was found between mortality and PPL. Multivariable Cox regression showed Charlson Comorbidity Index (HR: 1.896, 95%CI: 1.235-2.913), overhydration (HR: 10.034, 95%CI: 1.426-70.587) and lower PPL (HR: 0.576, 95%CI: 0.339-0.978) were predictors for mortality. Overhydration, was a strong predictor of PPL, overpowering variables previously reported as determinants of PPL, namely clinical correlates of endothelial dysfunction or local inflammation. PPL were not associated with malnutrition or higher mortality, emphasizing the importance of volume overload control in PD patients.

MO697: FGF-21 Correlates with Overhydration: Is There a Role for Peritoneal GLUT-1?

BACKGROUND AND AIMS

FGF-21 is a hepatokine that stimulates glucose uptake through GLUT-1. The presence of this glucose transporter in peritoneal fibroblasts is driven by peritoneal glucose exposure and is related to impaired ultrafiltration, predisposing to overhydration. The study was designed to determine FGF-21 levels in peritoneal effluent and serum, and its possible association with overhydration.

METHOD

Prevalent and incident peritoneal dialysis (PD) patients without diabetes were included. FGF-21 (dialysate and serum) was obtained during a 3.86% glucose peritoneal equilibration test. Peritoneal glucose load was calculated. The presence or absence of local peritoneal production was assessed by comparing the dialysate to plasma (D/P) ratio of FGF-21 (MW 32 kD) with that of albumin (MW 67 kD). Hydration status was assessed by bioimpedance. Spearman's correlations were performed.

RESULTS

A total of 58 patients (38 incident, 20 prevalent) were included, mean age 54 years, 67% males, PD duration from 1 to 75 months, mean 10.4. Residual GFR was 6.4 ± 3.5 mL/min/1.73 m2 and D/P creatinine 0.65 ± 0.12. Peritoneal glucose load was 110.5 g/day (range 40.8–226.9). Dialysate FGF-21 was 42.5 ± 47.0 pg/mL and serum FGF-21 943.9 ± 1164.8 pg/mL, giving a D/P ratio of 0.07. D/P albumin was 0.009, indicating that dialysate FGF-21 concentrations can be explained by transport from the circulation, without local peritoneal production. Serum FGF-21 was positively correlated with dialysate FGF-21, extracellular water excess and total peritoneal glucose load (all P < 0.01). Some association was present with PD duration (P < 0.05). No relationship was found between plasma FGF-21 and plasma insulin, D/P creatinine, or residual kidney function.

CONCLUSION

FGF-21 in peritoneal effluent is likely not locally produced, but caused by transport from the circulation. The associations between plasma FGF-21 levels with PD duration, peritoneal glucose load and overhydration, all indicate an effect of peritoneal glucose absorption from the peritoneal cavity into the interstitium with an insulin-independent storage into interstitial adipocytes, where it may stimulate the expression of GLUT-1.

MO688: Peritoneal Protein Clearance, Inflammation, Nutrition and Overhydration in PD Patients: Looking for the Culprit

BACKGROUND AND AIMS

Peritoneal protein loss has been for many years seen as a detrimental consequence of peritoneal dialysis (PD). Many studies correlated this leakage with mortality, malnutrition and inflammation. More recent knowledge has brought overhydration to this equation. This study aims to review classic and recent factors associated with peritoneal protein clearance and its consequences on overall mortality.

METHOD

Prevalent and incident PD patients were included. Interleukin 6 (IL-6; dialysate and serum) was obtained during a 3.86% glucose peritoneal equilibration test. Hydration and nutritional status was assessed by bioimpedance. Linear and Cox regression were performed.

RESULTS

A total of 78 patients were included (54 incident, 24 prevalent), the mean age was 54.6 ± 18.1 years, 65% were males, and the mean follow-up was 33.9 ± 29.3 months. The mean Charlson comorbidity index (CCI) was 4.4 ± 2.4. The residual GFR was 6.7 ± 3.6 mL/min/1.73 m2 and the D/P creatinine 0.65 ± 0.12. The IL-6 concentration in the dialysate was 24.9 ± 30.8 pg/mL and in serum was 37.3 ± 5.1 pg/mL. The phase angle was 5.4 ± 1.1°, overhydration 0.88 ± 0.94 L and peritoneal protein clearance 85.6 ± 54.7 mL/24 h. Overall, eight patients died.

Linear univariable analysis showed positive associations between peritoneal protein clearance and (i) small solute transport, as measured by D/P creatinine, (ii) body composition, as measured by phase angle and overhydration and (iii) CCI. The peritoneal protein clearance also correlated positively with dialysate IL-6, but not with serum IL-6. By linear multivariable analysis, using the backward method, a significant positive association between peritoneal protein and overhydration (P < 0.001; IC:26.665–71.694) and also phase angle (P = 0.032; IC: 1.845–39.330) were validated.

In the exploratory survival analysis, no relationship was found between mortality and peritoneal protein clearance. A univariable positive association was shown with serum IL-6 concentration, overhydration and CCI. A higher phase angle was associated with lower mortality. No relationship with dialysate IL-6 or D/P creatinine was found. In this early-stage PD population, with globally preserved residual kidney function, an effect of this variable on mortality was not evident.

Cox regression, conditional backward method, showed CCI (OR: 1.896, IC: 1.235–2.913, P = 0.003), overhydration (OR: 10.034, IC: 1.426–70.587, P = 0.021) and peritoneal protein clearance (OR: 0.576, IC: 0.339–0.978, P = 0.041) were predictors for mortality.

CONCLUSION

A better nutrition status and overhydration are the major determinants of peritoneal protein clearance. The survival analysis showed that mortality is higher in overhydrated patients, with higher CCI, but not with higher peritoneal protein clearance. Inflammation, local or systemic, as assessed by IL-6 concentration, did not reveal to be such a strong prognosis predictor as overhydration in these PD patients.

Gla-Rich Protein, Magnesium and Phosphate Associate with Mitral and Aortic Valves Calcification in Diabetic Patients with Moderate CKD

Accelerated and premature cardiovascular calcification is a hallmark of chronic kidney disease (CKD) patients. Valvular calcification (VC) is a critical indicator of cardiovascular disease and all-cause mortality in this population, lacking validated biomarkers for early diagnosis. Gla-rich protein (GRP) is a cardiovascular calcification inhibitor recently associated with vascular calcification, pulse pressure, mineral metabolism markers and kidney function. Here, we examined the association between GRP serum levels and mitral and aortic valves calcification in a cohort of 80 diabetic patients with CKD stages 2–4. Mitral and aortic valves calcification were detected in 36.2% and 34.4% of the patients and associated with lower GRP levels, even after adjustments for age and gender. In this pilot study, univariate, multivariate and Poisson regression analysis, show that low levels of GRP and magnesium (Mg), and high levels of phosphate (P) are associated with mitral and aortic valves calcification. Receiver operating characteristic (ROC) curves showed that the area under the curve (AUC) values of GRP for mitral (0.762) and aortic (0.802) valves calcification were higher than those of Mg and P. These results suggest that low levels of GRP and Mg, and high levels of P, are independent and cumulative risk factors for VC in this population; the GRP diagnostic value might be potentially useful in cardiovascular risk assessment.

P0873GLA-RICH PROTEIN (GRP) AS AN EARLY AND NOVEL MARKER ASSOCIATED WITH VASCULAR CALCIFICATION AND CKD-MINERAL AND BONE DISORDER (MBD) IN DIABETIC PATIENTS WITH CKD: A PILOT COHORT STUDY

Background and Aims

Cardiovascular disease (CVD) is the most life-threatening complication in chronic kidney disease (CKD) patients. In addition to traditional risk factors, most patients with CKD display abnormal mineral metabolism with underlying hormonal dysregulation, defined as chronic kidney disease-mineral and bone disorder (CKD-MBD). CKD-MBD involves changes in mineral ion homeostasis, bone quality and turnover, cardiovascular and soft tissue calcifications, which highly contribute for cardiovascular complications. Vascular calcification (VC) is associated with significant morbidity and mortality and a strong predictor of cardiovascular risk in CKD patients. Early preventive measures, including new diagnostic/prognostic tools, are required to reduce the development and progression of VC, left ventricular hypertrophy and arterial stiffness, which are crucial for the prevention of CVD outcomes in CKD patients. Gla-rich protein (GRP) is a vitamin K-dependent protein with a dual capacity to function as an inhibitor of pathological calcification and anti-inflammatory agent in the cardiovascular system, whose clinical utility is unknown. Our aim with this study was to evaluate the potential of GRP as a new marker for CKD-MBD and vascular calcification, in type 2 diabetic patients with chronic kidney disease (CKD) stages 2-4.

Method

In an observational prospective study including all eligible type 2 diabetic patients with CKD stages 2-4 (n=80) followed in outpatient nephrology consultation from 2010 to 2017, we explored correlations between levels of GRP in serum with mineral metabolism and inflammation markers, CKD developmental stage, vascular calcification and pulse pressure (PP). Vascular calcification score (VCS) was evaluated using the plain x-ray of the hands and pelvis (Adragão score), and increased cardiovascular risk was considered for VCS≥3. Measurements of GRP in serum were performed using a recently developed sandwich ELISA assay. Descriptive statistics, ANOVA and post hoc analysis with Scheffe test were used for analysis. Forward stepwise logistic regression (likelihood ratio) analysis was applied to identify predictive factors for VCS and PP, and ROC curves were used to assess the sensitivity and specificity of GRP in relation to these exposure factors.

Results

Spearman’s correlation analysis revealed the strong positive correlation between levels of serum GRP and eGFR (r=0.863, p<0.0001) and α klotho (r=0.647, p<0.0001), while a negative correlation with phosphate (P) (r=-0.715, <0.0001), FGF23 (r=-0.676, <0.0001), VCS (r=-0.822, p<0.0001), PP (r=-0.533, p<0.0001), calcium x phosphate (CaxP) (r=-0.302, p=0.006) and IL-6 (r=-0.349, p=0.002). Serum GRP levels were found to progressively decreased from stage 2 to stage 4 CKD. Multivariate analysis identified low levels of eGFR and GRP, and high levels of FGF-23 as independent risk factors for both the VCS and PP. The area under the ROC curves for GRP was 0.865±0.046, 95% CI (0.776-0.955), p<0.0001 for VCS and 0.782±0.054, 95% CI (0.677-0.887), p<0.0001 for PP.

Conclusion

Reduced levels of GRP were associated with higher levels of vascular calcification promoters such as P, FGF-23 and CaxP, and with lower levels of the VC inhibitor α-Klotho, indicating a correlation between GRP and the dysregulation of phosphate metabolism characteristic of CKD-MBD. In addition, this pilot cohort study indicates that GRP levels might be a significant clinical predictor of vascular calcifications in diabetic patients with CKD.

Funding

This research was funded by the Portuguese Society of Nephrology (SPN) through project funding 2016, by the Portuguese national funds from FCT - Foundation for Science and Technology through the transitional provision DL57/2016/CP1361/CT0006 and project UID/Multi/04326/2019.

Acknowledgments

To SPN by the attribution of the Jacinto Simões award (2018) financed by Fresenius medical care.

Gla-Rich Protein (GRP) as an Early and Novel Marker of Vascular Calcification and Kidney Dysfunction in Diabetic Patients with CKD: A Pilot Cross-Sectional Study

Vascular calcification (VC) is one of the strongest predictors of cardiovascular risk in chronic kidney disease (CKD) patients. New diagnostic/prognostic tools are required for early detection of VC allowing interventional strategies. Gla-rich protein (GRP) is a cardiovascular calcification inhibitor, whose clinical utility is here highlighted. The present study explores, for the first time, correlations between levels of GRP in serum with CKD developmental stage, mineral metabolism markers, VC and pulse pressure (PP), in a cohort of 80 diabetic patients with mild to moderate CKD (stages 2–4). Spearman’s correlation analysis revealed a positive association of GRP serum levels with estimated glomerular filtration rate (eGFR) and α-Klotho, while a negative correlation with phosphate (P), fibroblast growth factor 23 (FGF-23), vascular calcification score (VCS), PP, calcium (x) phosphate (CaxP) and interleukin 6 (IL-6). Serum GRP levels were found to progressively decrease from stage 2 to stage 4 CKD. Multivariate analysis identified low levels of eGFR and GRP, and high levels of FGF-23 associated with both the VCS and PP. These results indicate an association between GRP, renal dysfunction and CKD-mineral and bone disorder. The relationship between low levels of GRP and vascular calcifications suggests a future, potential utility for GRP as an early marker of vascular damage in CKD.

Low Magnesium Levels and FGF-23 Dysregulation Predict Mitral Valve Calcification as well as Intima Media Thickness in Predialysis Diabetic Patients

Background. Mitral valve calcification and intima media thickness (IMT) are common complications of chronic kidney disease (CKD) implicated with high cardiovascular mortality. Objective. To investigate the implication of magnesium and fibroblast growth factor-23 (FGF-23) levels with mitral valve calcification and IMT in CKD diabetic patients. Methods. Observational, prospective study involving 150 diabetic patients with mild to moderate CKD, divided according to Wilkins Score. Carotid-echodoppler and transthoracic echocardiography were used to assess calcification. Statistical tests used to establish comparisons between groups, to identify risk factors, and to establish cut-off points for prediction of mitral valve calcification. Results. FGF-23 values continually increased with higher values for both IMT and calcification whereas the opposite trend was observed for magnesium. FGF-23 and magnesium were found to independently predict mitral valve calcification and IMT (P < 0.05). Using Kaplan-Meier analysis, the number of deaths was higher in patients with lower magnesium levels and poorer Wilkins score. The mean cut-off value for FGF-23 was 117 RU/mL and for magnesium 1.7 mg/dL. Conclusions. Hypomagnesemia and high FGF-23 levels are independent predictors of mitral valve calcification and IMT and are risk factors for cardiovascular mortality in this population. They might be used as diagnostic/therapeutic targets in order to better manage the high cardiovascular risk in CKD patients.

Phosphorus as an early marker of morbidity and mortality in type 2 chronic kidney disease diabetic patients

AIMS

To evaluate the association of different phosphorus levels with cardiovascular mortality and hospitalizations risk in type-2 diabetic patients in phase 3/4 of CKD.

METHODS

An observational, prospective study involving 119 patients divided into groups according to baseline phosphorus levels: 1, ≤3.60 mg/dL; 2, 3.60-4.60 mg/dL; and 3, >4.60 mg/dL. Baseline characteristics were analyzed and compared. Multivariate Cox regression and Multivariate Logistic regression were used to find out the predictors of cardiovascular mortality and hospitalizations, respectively. T-test was used to investigate the association of phosphorus and start of hemodialysis.

RESULTS

Patients of group 3 presented lower clearance and Hb and increased PTH, Ca×P, LVMI, HOMA, uric acid, IL-6 and more hospitalization days. Patients' mean survival on groups 1, 2 and 3 was 62.5 ± 1.95, 60.1 ± 2.85 and 52.6 ± 2.84 months, respectively (p = 0.001). Phosphorus and creatinine levels were independent predictors of mortality, and phosphorus, creatinine, PTH and age were independent predictors of hospitalizations in this population. Patients who entered hemodialysis presented greater phosphorus levels than those who did not (5.04 ± 1.31 vs. 4.14 ± 1.09; p = 0.001).

CONCLUSIONS

Phosphorus was a predictor of cardiovascular mortality and hospitalizations. Phosphorus levels might have a significant clinical use, possibly translated as an early marker of mortality and hospitalizations in this population.

Statins and vitamin D: a friendly association in pre-dialysis patients

The increased mortality rate observed in patients with chronic kidney disease is related to the high prevalence of cardiovascular disease in this population. Recently, it has been shown that interventional therapy with statins and/or vitamin D could improve the outcomes of these patients. The aim of this study was to identify the risk factors for mortality in a group of patients with chronic kidney disease (stages 4 and 5--pre-dialysis) and verify whether vitamin D and statins could change the outcome. We included 95 patients (mean age--69.4) with stages 4 and 5 (pre-dialysis) of our "low-clearance" outpatient clinic, with an average eGFR of 16.9 ml/min and a mean follow-up of 24.1 months. Several biological, nutritional, laboratory and inflammatory parameters were analysed at baseline. Our population was divided into three groups: G-I, patients not medicated with either vitamin D or statins; G-II, patients medicated with either vitamin D or statins; and G-III, patients medicated with vitamin D and statins. We found (ANOVA) that the serum levels of pre-albumin (P = 0.018) and PTH (P = 0.03) were lower in G-I. Concerning the inflammatory parameters, G-I showed higher levels of hsCRP (P = 0.014) and a trend to higher IL-6 levels (P = 0.077). We found the actuarial survival at 30 months (Kaplan-Meier), to be 56.4% in G-I, 82.3% in G-II and 100% in G-III (log rank = 13.08 P = 0.0014). Using the Cox proportional hazards model, we found that the existence of coronary artery disease (P = 0.0001) and the absence of medication with vitamin D and/or statins (P = 0.005) independently influenced the mortality of our patients. In conclusion, we found, in our study, that patients under vitamin D and statins (with a synergistic effect) were less inflamed and showed a lower mortality rate.

Inflammation, homocysteine and carotid intima-media thickness

INTRODUCTION

Cardiovascular disease is the main cause of morbidity and mortality in chronic renal patients. Carotid intima-media thickness (CIMT) is one of the most accurate markers of atherosclerosis risk. In this study, the authors set out to evaluate a population of chronic renal patients to determine which factors are associated with an increase in intima-media thickness.

METHODS

We included 56 patients (F=22, M=34), with a mean age of 68.6 years, and an estimated glomerular filtration rate of 15.8 ml/min (calculated by the MDRD equation). Various laboratory and inflammatory parameters (hsCRP, IL-6 and TNF-alpha) were evaluated. All subjects underwent measurement of internal carotid artery intima-media thickness by high-resolution real-time B-mode ultrasonography using a 10 MHz linear transducer.

RESULTS

Intima-media thickness was used as a dependent variable in a simple linear regression model, with the various laboratory parameters as independent variables. Only parameters showing a significant correlation with CIMT were evaluated in a multiple regression model: age (p=0.001), hemoglobin (p=00.3), logCRP (p=0.042), logIL-6 (p=0.004) and homocysteine (p=0.002). In the multiple regression model we found that age (p=0.001) and homocysteine (p=0.027) were independently correlated with CIMT. LogIL-6 did not reach statistical significance (p=0.057), probably due to the small population size.

CONCLUSION

The authors conclude that age and homocysteine correlate with carotid intima-media thickness, and thus can be considered as markers/risk factors in chronic renal patients.

Nutritional and inflammatory status influence darbepoetin dose in pre-dialysis elderly patients

Anaemia is a common finding in elderly patients particularly in those with chronic kidney disease. Effective correction of anaemia improves survival and quality of life. The association between anaemia and a poor nutritional status as well as the presence of inflammation has already been documented. The aim of our study was to assess the impact of the nutritional and inflammatory status on darbepoetin dose requirements of elderly patients followed in a "Chronic Kidney Disease" outpatient clinic. We included 71 elderly patients (age>or=65 years) in a "Chronic Kidney Disease" outpatient clinic. Creatinine Clearance (CrCl) was estimated according to the Cockroft-Gault equation. Nutritional status was evaluated by biochemical and anthropometric parameters. Tumour Necrosis Factor-alpha (TNF-alpha), Interleukin-6 (IL-6) and high sensitivity C-reactive protein (hs-CRP) were used as biomarkers of inflammation. Our patients (56% males) with a mean age of 76.2+/-6.6 years were followed for 33.1+/-43.6 months. Mean eCrCl was 13.5+/-7.2 ml/mn/1.73 m2. All patients were under supplemental iron therapy and 74.7% needed darbepoietin (0.762+/-0.6 (microg/kg/week) to correct anaemia. Among the several variables regressed on darbepoietin dose, in a multiple regression model, only Hb, IL-6 and TNF-alpha levels and SGA score predicted the need for higher doses of darbepoietin. (r=0.677; r2=0.459). In Conclusion, in our pre-dialysis elderly patients, markers of a poor nutritional status (SGA and albumin) and inflammation (IL-6 and TNF-alpha) independently predicted the use of higher doses of darbepoietin to correct anaemia.

Anaemia correction in predialysis elderly patients: influence of the antihypertensive therapy on darbepoietin dose

Anaemia and hypertension are common in patients with chronic renal insufficiency. The correction of anaemia with erythropoiesis stimulating agents (ESA) can improve survival and decrease the decline of renal function. Angiotensin converting-enzyme inhibitors (ACEI) and angiotensin II receptor blockers (AIIRA) can also slow the progression of renal failure, but the blockade of the renin-angiotensin system can worsen anaemia. The aim of our study was to assess the impact of antihypertensive therapy (ACEI plus AIIRA) in the requirements of darbepoietin in a group of elderly predialysis patients. We included 71 patients (m = 39, f = 32), mean age of 76.3 years with a mean creatinine clearance of 17.5 ml/min. Patients were divided in two groups according to their antihypertensive therapy: G-I patients under ACEI or AIIRA therapy and G-II normotensive patients or hypertensive patients under antihypertensive drugs other than ACEI or AIIRA. The groups were compared regarding demographic, nutritional, biochemical and inflammatory parameters. We also compared the mean darbepoietin dose. In GI the mean dose of darbepoietin was higher than in GII (0.543 vs. 0.325 microg/kg/week, P = 0.032). We did not find any difference regarding other parameters analysed. We conclude that ACEI and AIIRA can increase the needs of darbepoietin in predialysis elderly patients. However, when formally indicated to treat hypertension in a specific patient, they should not be switched to another antihypertensive agent. Instead, in such cases, higher doses of ESA should be used, if necessary.