Effects of acute fructose loading on levels of serum uric acid-a pilot study.

BACKGROUND: Fructose intake may lead to hyperuricaemia, which is associated with increased risk and progression of kidney disease. We aimed to explore the acute effects of fructose loading from different sources, with and without a pizza, on levels of serum uric acid in patients with chronic kidney disease (CKD), type 2 diabetes (T2D) without CKD, and in healthy subjects (HS). METHODS: The study included six HS, and three CKD stage 4-5 and seven T2D patients. Drinks consumed were blueberry drink (17.5 g fructose), Coca-Cola (18 g fructose) and fructose drink (35 g fructose). The drinks were also combined with pizza, in total six interventions. Serum samples were collected fasting and 30, 60, 90 and 120 minutes after intake and also 240 minutes after drink + pizza, and analysed for fructose, uric acid and triglycerides. Postprandial responses were explored using repeated-measure ANOVA. RESULTS: Baseline serum uric acid levels were increased in CKD (P = 0.037). There were significant differences in serum fructose and serum uric levels over time between drinks and drinks + pizza for all groups (P < 0.001 and P < 0.05, respectively). The highest peak in serum fructose followed the fructose drink interventions and the lowest the blueberry drink. The fructose drink interventions gave the highest responses in serum uric acid and the lowest responses followed the blueberry drink. Triglycerides increased following pizza interventions (P < 0.001). CONCLUSIONS: Intake of fructose increases serum uric acid. The fructose intake via a blueberry drink induced lowest increase and thus may be protective.

Skin autofluorescence, arterial stiffness and Framingham risk score as predictors of clinical outcome in chronic kidney disease patients: a cohort study.

BACKGROUND: The risk of cardiovascular disease (CVD) is predicted by Framingham's CVD risk scores (FRS) but the high CVD-related mortality in patients with chronic kidney disease (CKD) is only partially explained by traditional CVD risk markers. Therefore, there is a need to explore whether other CVD risk markers may improve risk prediction. Although arterial stiffness measured by augmentation index (AIx) and tissue content of advanced glycation end-products (AGEs) measured by skin autofluorescence (SAF) are two biomarkers that associate with CVD and mortality in CKD, it is not known how they compare with FRS. We evaluated associations between SAF, AIx and FRS, and their associations with CVD and mortality in CKD patients. METHODS: SAF (AGE Reader) and AIx (SphygmoCor; adjusted for 75 heart beats per minute) were measured in 261 clinically stable and extensively phenotyped patients with CKD Stage 5 (median age 56 years, 66% male, 20% diabetes; 130 non-dialysed, 93 patients on peritoneal dialysis and 38 patients on haemodialysis). Multivariate receiver operator characteristics (ROC) curve analysis and multivariate Cox models followed by C-statistics were used to evaluate CVD-related and all-cause mortality risk associated with SAF, AIx and FRS during follow-up for median 25 months with 46 deaths. RESULTS: In multivariate regression analysis, SAF associated with FRS, haemoglobin, fat body mass index and CVD, and inversely with per cent handgrip strength (HGS). AIx associated with FRS, and inversely with per cent HGS. Associations of SAF and AIx with high-sensitivity C-reactive protein (hsCRP), serum albumin, statin therapy and renal replacement therapy were not statistically significant. In ROC analysis, area under the curve (AUC) for CVD mortality ranged from AUC = 0.72 (AIx and FRS, respectively) to AUC = 0.78 (FRS + AIx), and for all-cause mortality from AUC = 0.70 (AIx) to AUC = 0.79 (FRS + AIx). In multivariate Cox analysis, after adjusting for 1-standard deviation (1-SD) of FRS, 1-SD increase of SAF associated with all-cause mortality and 1-SD increase of AIx associated with CVD mortality and all-cause mortality. After further adjustments for hsCRP, albumin and presence of CVD, AIx (but not SAF) remained independently associated with CVD mortality, hazard ratio (HR) 2.14 [95% confidence interval (95% CI) 1.18-3.89] and all-cause mortality, HR 1.74 (95% CI 1.16-2.60). CONCLUSIONS: In patients with CKD Stage 5, SAF and aortic stiffness associated with mortality, independently of FRS. After adjusting for additional confounders including inflammation, aortic stiffness remained as an independent predictor of outcome. Since the contribution of SAF and aortic stiffness compared with FRS in ROC curve analysis was relatively modest, this underlines the importance of traditional CVD risk factors in CKD.

Plasma Beta-Trace Protein as a Marker of Residual Renal Function: The Effect of Different Hemodialysis Modalities and Intra-Individual Variability over Time.

BACKGROUND/AIMS: Beta-trace protein (BTP) is a low-molecular-weight molecule, which may be used to assess residual renal function (RRF) in dialysis patients. Here we evaluated the influence of hemodialysis (HD) and hemodiafiltration (HDF) on plasma BTP, and analyzed the inter- and intra-individual variability of plasma BTP over time in HD and peritoneal dialysis (PD) patients. METHODS: In 12 prevalent HD patients, the effect of a single session of low-flux HD, high-flux HD and HDF on plasma BTP was studied. Blood samples were taken at baseline, after 120 and 240 minutes, and at the start of the next dialysis session. In 13 HD patients and 10 PD patients, inter- and intra-individual variability over three months was studied (monthly and weekly, respectively). Plasma BTP was measured using a nephelometric method. RESULTS: No significant decrease in plasma BTP was seen following a session of low-flux HD. Both high-flux HD and HDF resulted in a significant decrease immediately after dialysis (22% and 61% median decrease, respectively). A significant reduction of the molecule persisted only in HDF and a significant decrease (-15%) was still found immediately before the start of the next dialysis session. In both HD and PD patients, the reproducibility over time was excellent with intra-class correlation coefficient of 0.96 (0.93-0.99) and 0.92 (0.86-0.99) respectively. In a small cohort of PD patients, fair agreement existed between mGFR (average of renal urea and creatinine clearance from a 24 hours urine collection) and the BTP-based GFR estimation. CONCLUSION: BTP is a stable marker and a promising tool for RRF estimations in PD and HD patients. In patients receiving HDF, plasma levels of BTP should be interpreted with caution.

Plasma S100A12 and soluble receptor of advanced glycation end product levels and mortality in chronic kidney disease Stage 5 patients.

BACKGROUND: Alterations in the advanced glycation end-products (AGE)-receptor of AGE (RAGE) system are linked to several chronic diseases, which may result from vascular damage. A high circulating level of the pro-inflammatory RAGE-ligand S100A12, also known as EN-RAGE, is thought to promote while a high level of soluble RAGE (sRAGE) is thought to protect against development of atherosclerotic cardiovascular disease (CVD). We evaluated circulating S100A12 and sRAGE in relation to clinical characteristics, nutritional status, inflammation and mortality risk in chronic kidney disease (CKD) Stage 5 patients starting on dialysis. METHODS: Plasma S100A12 and sRAGE, biomarkers of inflammation and nutritional status, and comorbidities were investigated in 200 CKD Stage 5 patients [median age of 56 years, 62% men and median glomerular filtration rate (GFR) of 6.2 mL/min/1.73 m(2)] in conjunction with initiation of dialysis therapy. Associations between mortality risk and S100A12 or sRAGE were assessed after a median follow-up period of 23 months. In addition, for comparative analyses, S100A12 and sRAGE levels were assessed also in 58 haemodialysis and 78 peritoneal dialysis patients after 1 year of dialysis, 56 CKD Stages 3-4 patients and 50 community-based control subjects. RESULTS: The median level of S100A12 was 4-fold higher, median sRAGE 2.4 higher and median ratio S100A12/sRAGE 2.27 times higher in CKD 5 patients than in controls. Similar alterations were observed in CKD 3-4 patients; however, CKD 5 patients had a higher median level of sRAGE than the CKD 3-4 patients. In the CKD 5 patients, S100A12 levels were higher in those with diabetes or CVD than in those without these comorbidities. Furthermore, S100A12 correlated with high-sensitivity C-reactive protein (hsCRP) levels (ρ = 0.53; P < 0.001) and a 1-SD higher level of S100A12 associated with increased all-cause mortality risk (hazard ratio 1.32, 95% confidence interval 1.01-1.73) after adjustment for age, sex, comorbidity, nutritional status and inflammation (hsCRP). In the CKD 5 patients, sRAGE correlated negatively with GFR (ρ = -0.26; P < 0.01) but sRAGE did not associate with hsCRP, comorbidities or mortality. CONCLUSIONS: Plasma concentrations of sRAGE, S100A12 and the ratio S100A12/sRAGE, are markedly elevated in CKD 5 patients starting on dialysis as well as in CKD 3-4 patients and prevalent dialysis patients suggesting that these alterations are typical for patients with moderate or severe CKD. In CKD 5 patients, an increased concentration of S100A12 are associated with inflammation, comorbidities and increased mortality risk whereas no such associations were observed for sRAGE. These results suggest that while high plasma S100A12 is an independent predictor of increased mortality risk, sRAGE does not seem to be a valid risk marker in this patient population.

Autologous Peripheral Blood Mononuclear Cells as Treatment in Refractory Acute Respiratory Distress Syndrome.

BACKGROUND: Acute respiratory distress syndrome (ARDS) is a devastating disorder. Despite enormous efforts in clinical research, effective treatment options are lacking, and mortality rates remain unacceptably high. OBJECTIVES: A male patient with severe ARDS showed no clinical improvement with conventional therapies. Hence, an emergent experimental intervention was performed. METHODS: We performed intratracheal administration of autologous peripheral blood-derived mononuclear cells (PBMCs) and erythropoietin (EPO). RESULTS: We found that after 2 days of initial PBMC/EPO application, lung function improved and extracorporeal membrane oxygenation (ECMO) support was reduced. Bronchoscopy and serum inflammatory markers revealed reduced inflammation. Additionally, serum concentration of miR-449a, b, c and miR-34a, a transient upregulation of E-cadherin and associated chromatin marks in PBMCs indicated airway epithelial differentiation. Extracellular vesicles from PBMCs demonstrated anti-inflammatory capacity in a TNF-α-mediated nuclear factor-x03BA;B in vitro assay. Despite improving respiratory function, the patient died of multisystem organ failure on day 38 of ECMO treatment. CONCLUSIONS: This case report provides initial encouraging evidence to use locally instilled PBMC/EPO for treatment of severe refractory ARDS. The observed clinical improvement may partially be due to the anti-inflammatory effects of PBMC/EPO to promote tissue regeneration. Further studies are needed for more in-depth understanding of the underlying mechanisms of in vivo regeneration.

Macrophage migration inhibitory factor (MIF) and thyroid hormone alterations in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV).

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine known to be released from lymphocytes, macrophages and endothelial cells and also in animal models shown to be inducible with glucocorticoids (GC). In contrast, thyroxine seems to antagonize MIF activity. To investigate whether MIF is increased in active antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and possible correlations with GC dosing and thyroid hormone levels, 27 consecutive patients with active AAV were studied and followed prospectively. Disease activity was assessed using Birmingham Vasculitis Activity Score 2003 (BVAS) at baseline and at follow-up at 3 and 6 months, along with MIF, thyroid hormones free triiodothyronine (fT3) and free thyroxine (fT4), C-reactive protein (CRP) and creatinine. MIF was elevated significantly at baseline compared with follow-up at 3 and 6 months (8,618 pg/mL versus 5,696 and 6,212 respectively; P < 0.002) but did not correlate to CRP, GC dose, creatinine or organ involvement. fT3 was depressed significantly at baseline compared with follow-up (1.99 pg/mL versus 2.31 and 2.67 respectively; P = 0.01) and correlated inversely to the BVAS score at baseline. We found a significant correlation between the MIF/fT4 ratio at baseline versus MIF/fT4 ratio at 6 months (ρ = 0.52, P < 0.005) and a trend between the baseline MIF/fT3 ratio versus MIF/fT3 ratio at 6 months (ρ = 0.39, P = 0.05). These results suggest a possible role for MIF and thyroid status in AAV. Further studies could reveal whether the association between AAV and thyroid hormone levels in the context of elevated MIF may present a link as well as a target of treatment.

Circulating vascular endothelial growth factor (VEGF) and its soluble receptor 1 (sVEGFR-1) are associated with inflammation and mortality in incident dialysis patients.

BACKGROUND: Vascular endothelial growth factor (VEGF) and its soluble receptor 1 (sVEGFR-1) predict mortality in nondialyzed chronic kidney disease (CKD) stage 3-5 patients and prevalent hemodialysis (HD) patients. We investigated determinants of VEGF and sVEGFR-1 as well as their relationship with all-cause mortality in incident dialysis patients. METHODS: In this longitudinal cohort study of 211 CKD 5 patients [64% males, mean age of 54 ± 12 years and median glomerular filtration rate (GFR) 5.9 [interquartile range (IQR), 4.6-7.2 mL/min/1.73 m2] who were enrolled at initiation of renal replacement therapy, demographics, clinical characteristics, including comorbidities and laboratory data were obtained at the beginning of the study. After 12 months, blood was again drawn from 95 dialysis patients [42 HD patients and 53 peritoneal dialysis (PD) patients]. The 211 patients were followed up for a median of 29 (IQR, 15-37) months for survival analysis. Plasma was also obtained from 47 healthy controls. RESULTS: VEGF and sVEGFR-1 levels did not change significantly after 12 months on HD or PD. The sVEGFR-1, but not VEGF levels, differed between the patients and the healthy controls. VEGF and sVEGFR-1 correlated with high-sensitivity C-reactive protein (hsCRP; rho = 0.19, P = 0.01 and rho = 0.16, P = 0.03; respectively), leukocyte count (rho = 0.22; P < 0.01 and rho = 0.23; P < 0.01; respectively) and sVEGFR-1 correlated also with interleukin-6 (IL-6) (rho = 0.21, P < 0.01). In Kaplan-Meier analysis, a high VEGF level was associated with increased all-cause mortality (Chi-square = 5.8, P = 0.02) which remained after adjustments for age, gender, body mass index (BMI), IL-6, GFR and comorbidities [hazard ratio, HR: 3.08, 95% confidence intervals (CI) 1.48-6.42]. Whereas sVEGFR-1 per se did not predict mortality, a high sVEGFR-1 level in patients with concomitant high IL-6 was associated with increased all-cause mortality (HR 2.83, 95% CI 1.32-6.06) which remained significant after adjustments for age, gender, BMI and comorbidities (HR 2.33, 95% CI 1.06-5.14) but not after adjusting also for GFR. CONCLUSIONS: The circulating levels of VEGF and sVEGFR-1 are associated with biomarkers of inflammation. VEGF predicts all-cause mortality, independent of inflammation, while an elevated sVEGFR-1 level increased the mortality risk in inflamed patients.

Differences in acute metabolism of fructose between hemodialysis patients and healthy subjects.

The consumption of fructose has increased dramatically during the last few decades and parallels the epidemics of obesity, metabolic syndrome, diabetes and chronic kidney disease (CKD). Fructose occurs naturally e.g. in fruit and in honey (rich in this monosaccharide) and as sucrose (table sugar). The effects of fructose have been attributed to the transient increases in serum uric acid levels during its metabolism. Recent research, also in CKD patients, has linked fructose to dysmetabolism of lipids, glucose and oxidative radicals. However, a general consensus of the potentially harmful effects of fructose is lacking. We improved a sensitive inulin assay for fructose measurement in serum and plasma and tested its accuracy in an acute experiment following consumption of pure fructose in controls. In addition, fructose and uric acid were analyzed postprandially during 240 min in six maintenance hemodialysis (HD) patients and nine healthy subjects consuming 190 ml cream/75 g sucrose in a fasting state. Whereas the fructose levels reached a maximum level after 60 min in controls they had not even started to decrease at 240 min in HD-patients. Likewise, while uric acid levels remained stable in controls they increased by 10% in HD patients at 240 min following the meal. In conclusion, a glucose and fat rich meal is associated with delayed absorption and/or metabolism of fructose in HD patients as well as increased serum uric acid levels.

Pentraxin 3, a sensitive early marker of hemodialysis-induced inflammation.

BACKGROUND/AIMS: The purpose of this investigation was to determine if the long pentraxin 3 (PTX-3) may be a useful marker of intradialytic inflammation since it is rapidly released in the vasculature. METHODS: PTX-3, interleukin-6, tumor necrosis factor-α and C-reactive protein were measured before and during a hemodialysis session in 22 patients and compared with healthy subjects. The effect of dialysis with low-flux, high-flux membranes and hemodiafiltration on the inflammatory response was compared in 11 patients. RESULTS: C-reactive protein and interleukin-6 levels did not change, while a modest decrease in tumor necrosis factor-α was observed during hemodialysis. The plasma PTX-3 concentration was significantly increased (p < 0.001) after 60 min and peaked at 180 min during hemodialysis. There was no difference in the intradialytic increase in PTX-3 using different dialysis membranes and modalities. CONCLUSION: PTX-3 stands out as a rapid and sensitive marker of hemodialysis-induced inflammation. Membrane flux and hemodiafiltration did not alter the inflammatory response.

Effects of Acute Fructose Loading on Markers of Inflammation-A Pilot Study.

Inflammation plays a role in development of diabetic complications. The postprandial state has been linked to chronic low grade inflammation. We therefore aimed to investigate the acute effects of fructose loading, with and without a pizza, on metabolic and inflammatory markers in patients with type 2 diabetes (T2D) (n = 7) and in healthy subjects (HS) (n = 6), age 47-76 years. Drinks consumed were blueberry drink (18 g fructose), Coca-Cola (17.5 g fructose), and fructose drink (35 g fructose). The levels of glucose, insulin, insulin-like growth factor binding protein-1 (IGFBP-1) and inflammatory markers: Interleukin-6 (IL-6), Monocyte chemoattractant protein-1 (MCP-1), Interleukin-18 (IL-18), Intercellular Adhesion Molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and bacterial lipopolysaccharides (LPS) were analyzed in blood. The postprandial responses were assessed using Wilcoxon's matched-pairs test, Friedman's ANOVA and Mann-Whitney U test. There was no difference in baseline levels of inflammatory markers between the groups. In T2D, MCP-1 decreased following blueberry drink and Coca-Cola (p = 0.02), Coca-Cola + pizza and fructose + pizza (p = 0.03). In HS, IL-6 increased following blueberry + pizza and fructose + pizza (p = 0.03), there was a decrease in MCP-1 following blueberry drink and Coca-Cola (p = 0.03), and in ICAM-1 following blueberry + pizza (p = 0.03). These results may indicate a role for MCP-1 as a link between postprandial state and diabetes complications, however further mechanistic studies on larger population of patients with T2D are needed for confirmation of these results.

Clinical importance of an elevated circulating chemerin level in incident dialysis patients.

BACKGROUND: Circulating chemerin, a novel adipokine linked to obesity, glucose tolerance and hyperlipidaemia, was recently reported to be increased in chronic kidney disease (CKD) patients. We explored possible links between chemerin and various clinical, nutritional and biochemical markers as well as its association with 5-year all-cause mortality. METHODS: Fasting plasma samples were obtained from 252 CKD Stage 5 patients [median age 56 years, male 61%, glomerular filtration rate (GFR) 7 mL/min] enrolled at the initiation of dialysis. Serum chemerin was measured using commercial ELISA. Chemerin levels were related to clinical status and biomarkers of inflammation, glucose and lipid metabolism and body composition (body mass index and total and truncal fat mass by dual-energy X-ray absorptiometry). Survival, censored for transplantation, was recorded for a follow-up time of 5 years. RESULTS: In univariate regression, circulating chemerin (119 ± 26 ng/mL) was positively correlated with cholesterol (ρ = 0.21; P = 0.001), triglycerides (ρ = 0.22; P = 0.0007), apolipoprotein B (ρ = 0.33; P < 0.0001), high-sensitivity C-reactive protein (ρ = 0.18; P = 0.006), white blood cell count (ρ = 0.23; P < 0.001), insulin (ρ = 0.18; P < 0.05) and homeostatic model assessment (HOMA) index (ρ = 0.17; P < 0.05), whereas we found a negative correlation with GFR (ρ = -0.28; P = 0.007), high-density lipoprotein cholesterol (ρ = -0.15; P < 0.05) and homocysteine (ρ = -0.25; P = 0.001). Moreover, a high chemerin predicted a better survival (log-rank χ(2) = 3.85; P < 0.05). Also, in a Cox model, adjustments for age, sex and CRP did not alter this finding (hazard ratio = 1.98 [95% confidence interval = 1.13-3.50], P = 0.01). However, adjusting for GFR made the model non-significant. CONCLUSIONS: We report that, in incident dialysis patients, an elevated chemerin is associated with a survival advantage despite its significant positive association with markers of inflammation and dyslipidaemia.

Visfatin is increased in chronic kidney disease patients with poor appetite and correlates negatively with fasting serum amino acids and triglyceride levels.

OBJECTIVE: Anorexia is a common complication of chronic kidney disease (CKD), while novel animal and human data suggest a role for visfatin in regulating feeding behavior. We hypothesized that increased visfatin levels in CKD patients may be involved in the regulation of appetite and nutrient homeostasis. METHODS: This is a cross-sectional study where circulating visfatin levels were analysed in 246 incident CKD stage 5 patients starting dialysis therapy. The associations between visfatin (enzyme-linked immunosorbent assay, ELISA) and anthropometric and biochemical nutritional status, self-reported appetite, fasting serum amino acids (high-performance liquid chromatography) and circulating cytokine levels (ELISAs) were assessed. We also performed genotyping (Pyrosequencing(R)) of two polymorphisms (rs1319501 and rs9770242) in the visfatin gene. RESULTS: Serum visfatin concentrations were not associated with either body mass index or serum leptin. Across groups with worsening appetite, median visfatin levels were incrementally higher (P < 0.05). With increasing visfatin tertiles, patients proved to be more often anorectic (P < 0.05) and to have incrementally lower serum albumin, cholesterol and triglycerides as well as lower essential and non-essential serum amino acids (P < 0.05 for all). A polymorphism in the visfatin gene was associated with increased circulating visfatin levels and, at the same time, a higher prevalence of poor appetite (P < 0.05 for both). CONCLUSION: Our study suggests novel links between visfatin and anorexia in CKD patients. Based on recent studies, we speculate that high visfatin in CKD patients may constitute a counter-regulatory response to central visfatin resistance in uremia. Future studies should examine a putative role of visfatin as a regulator of nutrient homeostasis in uremia.

The kidney is the major site of S-adenosylhomocysteine disposal in humans.

S-adenosylhomocysteine (SAH), the metabolic precursor of homocysteine in the body, is a potent inhibitor of methylation reactions. Several methylation reactions play a major role in epigenetic regulation of protein expression, atherosclerosis, and cancer development. Here we studied the mechanisms responsible for the maintenance of circulating SAH levels by measurement of the arterio-venous differences across the kidney, splanchnic organs, and the lung in humans. The lungs did not remove or add any circulating SAH, whereas the liver released it into the hepatic veins. The kidney extracted 40% of SAH and the SAH arterio-venous difference across the kidney was directly and significantly related to its arterial levels. Thus, the kidney plays a major role in maintaining SAH levels and may, indirectly, control tissue transmethylation reactions. Our findings of a pivotal role for the human kidney in sulfur amino acid metabolism may also account for the increased plasma levels of SAH in patients with chronic kidney diseases.

Associations of VEGF and its receptors sVEGFR-1 and -2 with cardiovascular disease and survival in prevalent haemodialysis patients.

BACKGROUND: Vascular endothelial growth factor (VEGF) was recently shown to predict survival in prevalent haemodialysis patients. Soluble VEGF receptors (sVEGFR)-1 and -2 are circulating endogenous modulators of VEGF activity. We thus studied the relationship between sVEGFR-1 and -2 and survival in a cohort of prevalent haemodialysis (HD) patients. METHODS: Components of the VEGF system were measured (ELISAs) in 185 prevalent HD patients and levels related to clinical characteristics, biochemical markers and survival. The patients were followed up prospectively for a median 31 (20-37) months. RESULTS: While ischaemic heart disease was independently associated with a lower sVEGFR-2 (OR = 2.75, P = 0.02), sVEGFR-1 was positively associated with IL-6 (rho = 0.22, P = 0.003) and white blood cell count (rho = 0.22, P = 0.002). In survival analysis, the patients with a high sVEGFR-1 level had a higher all-cause mortality (Kaplan-Meier Chi-Square = 5.6, P = 0.02) and a higher adjusted mortality risk (Cox HR = 1.93, P = 0.009) than those with low levels. CONCLUSION: In the first clinical study of sVEGFR-1 and -2 in CKD, we found novel associations between the sVEGFRs and cardiac disease. This may be of clinical importance, as a high sVEGFR-1 was an independent risk factor for all-cause mortality.

Modification of the oxidative stress biomarker AOPP assay: application in uremic samples.

BACKGROUND: The levels of advanced oxidation protein products (AOPP), a plasma protein biomarker used to assess oxidative stress, are elevated in patients with chronic kidney disease (CKD). However, this apparent elevation is to a large extent due to assay interference (mostly by triglycerides which are usually markedly elevated in CKD). We therefore developed and tested a modified version of the AOPP assay to minimize the impact of this interference. METHODS: Plasma levels of AOPP, lipids, proteins and various biomarkers of inflammation and oxidative stress were analyzed in 218 prevalent hemodialysis patients and 13 healthy controls using the established original (oAOPP) assay and following precipitation of plasma lipids using dextran sulphate (modified assay, mAOPP). The modified results were validated against a lipid extraction procedure using ether/butanol. RESULTS: The modified assay decreased the levels of triglycerides and AOPP by 87% and 38%, respectively. Whereas oAOPP values correlated strongly with triglycerides, no such correlation was seen with mAOPP. The mAOPP levels correlated significantly with the oxidative stress markers 8-oxo-dG and pentosidine, whereas no such correlations were found for oAOPP. CONCLUSIONS: The oAOPP concentration is largely overestimated in plasma samples due to lipid interferences. Precipitation of triglycerides before analysis yields markedly lower mAOPP values which more accurately reflect oxidative stress. Based on these results we propose that AOPP should be analyzed using the modified assay, which is a cheap, simple and fast method.

Elevated serum levels of S-adenosylhomocysteine, but not homocysteine, are associated with cardiovascular disease in stage 5 chronic kidney disease patients.

OBJECTIVE: The putative role of sulfur amino acids such as homocysteine (tHcy) as cardiovascular risk factors is controversial in chronic kidney disease (CKD). Although, S-adenosylhomocysteine (SAH) levels have been linked to CVD in non-renal populations, such relationship has not been evaluated in CKD. DESIGN: Serum concentrations of S-adenosylmethionine (SAM), SAH and total homocysteine (tHcy) were determined by HPLC in 124 CKD stage 5 patients (GFR range 1-11 m/min) and 47 control subjects, and related to renal function, presence of CVD, inflammation and protein-energy wasting (PEW). RESULTS: The levels of SAM and SAH were higher in CKD patients than in controls. Both SAM (rho=-0.19; P<0.05) and SAH (rho=-0.37, P<0.001) were inversely related to GFR. The concentrations of SAH were significantly higher (P<0.001) in patients with CVD than in non-CVD patients, (683 (201-3057) vs 485 (259-2620) nmol/L; median (range)) as opposed to tHcy levels, which were lower in CVD patients. While SAH was not associated with the presence of inflammation or PEW, it was a significant contributor (OR; 4.9 (CI 1.8-12.8), P<0.001) to CVD in a multinomial logistic regression model (pseudo r(2)=0.31). CONCLUSION: Concentrations of serum SAH and SAM in CKD stage 5 patients are associated with renal function, but not with inflammation or PEW. Among the investigated sulfur amino acids, only SAH was independently associated with the presence of clinical signs of CVD. These findings suggest that while tHcy might be influenced by a number of confounding uremic factors, SAH levels may better reflect the putative increased cardiovascular risk of sulfur amino acid alterations in CKD patients.

Rate of synthetic oligosaccharide degradation as a novel measure of amylase activity in peritoneal dialysis patients.

BACKGROUND: Plasma alpha-amylase activity is elevated in uremic patients but lower in peritoneal dialysis (PD) patients using icodextrin in comparison to healthy controls. We studied the rate by which an exogenous oligosaccharide (maltoheptaose; G7) is degraded ex vivo by amylase in plasma from PD patients treated with glucose or icodextrin PD solutions. METHODS: Plasma amylase (pancreatic and total) activity and concentration were measured in 11 controls and in PD patients treated with glucose (n = 11) and icodextrin (n = 19). The plasma was spiked with G7 and/or synthetic amylase and the metabolites formed were measured by HPLC following incubation at 37 degrees C for 4 hours. RESULTS: The relationship between amylase activity and amylase concentration was similar in all patients and controls. The G7 degradation rate was slower in plasma from icodextrin patients but it was also reduced in patients using glucose compared with the controls, in spite of the higher amylase activity in the glucose group. Normalization (by spiking) of patient plasma with porcine amylase increased but did not normalize the speed of G7 degradation. At a given endogenous amylase activity level, the efficiency of G7 degradation was similar for both patient groups. CONCLUSIONS: An ex vivo model to study the relationship between amylase activity and the actual rate of carbohydrate (represented by G7) breakdown was developed and showed that PD patients using glucose and icodextrin degrade G7 at a slower speed than controls. This suggests that amylase-mediated carbohydrate metabolism is reduced in PD patients. Further clinical studies are needed to confirm if these findings hold true also in other groups of uremic patients with varying degrees of kidney failure, as well as in patients undergoing hemodialysis.

Brown adipose tissue in young adults who were born preterm or small for gestational age.

BACKGROUND: Brown adipose tissue (BAT) is present and functions to dissipate energy as heat in young adults and can be assessed using magnetic resonance imaging (MRI) to estimate the voxel fat fraction, i.e. proton density fat fraction (PDFF). It is hypothesized that subjects born preterm or small for gestational age (SGA) may exhibit disrupted BAT formation coupled to metabolic factors. Our purpose was to assess the presence of BAT in young adults born extremely preterm or SGA in comparison with controls. METHODS: We studied 30 healthy subjects (median age, 21 years): 10 born extremely preterm, 10 full term but SGA and 10 full term with a normal birth weight (controls). We utilized an MRI technique combining multiple scans to enable smaller echo spacing and an advanced fat-water separation method applying graph cuts to estimate B0 inhomogeneity. We measured supraclavicular/cervical PDFF, R2*, fat volume, insulin-like growth factor 1, glucagon, thyroid stimulating hormone and the BAT-associated hormones fibroblast growth factor 21 and irisin. RESULTS: The groups did not significantly differ in supraclavicular/cervical PDFF, R2*, fat volume or hormone levels. The mean supraclavicular/cervical PDFF was equivalent between the groups (range 75-77%). CONCLUSIONS: Young adults born extremely preterm or SGA show BAT development similar to those born full term at a normal birth weight. Thus, the increased risk of cardiovascular and metabolic disorders in these groups is not due to the absence of BAT, although our results do not exclude possible BAT involvement in this scenario. Larger studies are needed to understand these relationships.

Inflammation down-regulates CYP3A4-catalysed drug metabolism in hemodialysis patients.

BACKGROUND: Recent studies indicate that inflammation may also affect CYP3A4 activity. Associations of CYP3A4-mediated metabolism of quinine, with inflammatory biomarkers were investigated in patients undergoing maintenance hemodialysis (HD). METHODS: A single dose of 100 mg quinine was given to 44 HD patients and the plasma concentration of quinine and its metabolite 3-OH-quinine were measured 12 h after drug intake. The ratios of quinine/3-OH-quinine and 4ß-OH-cholesterol/cholesterol were used as markers of CYP3A4 activity. Inflammatory biomarkers, high-sensitive CRP (hsCRP), pentraxin 3 (PTX3) and orosomucoid were followed during 4 weeks prior to quinine administration. RESULTS: The quinine/3-OH-quinine ratio correlated with median concentrations of hsCRP (Rho = 0.48; p = 0.001) and orosomucoid (Rho = 0.44; p = 0.003), and also with interleukin-6 at 12 h after drug intake (Rho = 0.43; P = 0.004) but not PTX3. In multivariate regression analysis, the correlation between CYP3A4 activity and median hsCRP remained borderline significant (p = 0.05). 4ß-OH-cholesterol/cholesterol ratio correlated with quinine/3-OH-quinine (p = 0.008), but not with any of the inflammation markers. CONCLUSIONS: The association between CYP3A4 activity and inflammatory biomarkers suggest that the activity of CYP3A4 is reduced by inflammation in HD patients. Further studies are needed to confirm this finding and to assess to what extent magnitude and duration of inflammation as well as the microbiota affect drug metabolism.

Restrictive lung disorder is common in patients with kidney failure and associates with protein-energy wasting, inflammation and cardiovascular disease.

BACKGROUND: Cardiovascular disease (CVD), protein-energy wasting (PEW), and inflammation are common interrelated features of chronic kidney disease (CKD). Less is known about lung dysfunction in CKD and its possible role in this context. We evaluated lung function and its association with estimated glomerular filtration rate (GFR), CVD, PEW, and inflammation in individuals with normal to severely reduced GFR. METHODS: In 404 individuals with GFR category G1 (n = 31; GFR >90mL/min/1.73 m2), G2 (n = 46), G3 (n = 33), G4 (n = 49) and G5 (n = 245; GFR<15mL/min/1.73 m2), pulmonary function was assessed by spirometry. Obstructive (OLD) and restrictive (RLD) lung dysfunction was defined based on forced vital capacity (FVC), forced expiratory volume in the first second (FEV1) and peak expiratory flow (PEF), expressed as percentages of predicted values (%FEV1, %FVC and %PEF, respectively). PEW was evaluated by subjective global assessment, handgrip strength (HGS) and lean body mass index (LBMI), and inflammation by interleukin-6 and high sensitivity C-reactive protein. RESULTS: RLD (defined as FEV1/FVC ≥ 0.70 and %FVC<80) associated with GFR and was present in 36% of G5 and 14% of G1-4 individuals. OLD (FEV1/FVC<0.70) was less common with similar prevalence among G1-4 (9%) and G5 (11%) individuals. Notably, 64% of those with concomitant presence of PEW, inflammation and clinical signs of CVD had RLD while 79% of those lacking these complications had normal lung function. In multivariate logistic regression analysis, RLD associated with CVD, PEW and inflammation, after adjusting for Framingham's CVD risk score, serum albumin, and GFR category. CONCLUSIONS: RLD is a common complication in patients with advanced CKD, especially in those with concomitant presence of CVD, inflammation and PEW. RLD appears to be an integral albeit scarcely explored consequence of pulmonary-renal interactions in CKD patients.