Effects Of The Uremic Toxins P-cresyl Sulfate On Left Ventricular Diastolic Dysfunction

ObjectivePatients with chronic kidney disease(CKD)are at high risk of cardiovascular disease(CVD).The main events observed during the various aspects of uremic cardiovascular dysfunction include heart failure,atherosclerosis,arterial stiffness,vascular calcifications,and impaired angiogenesis.Cardiac diastolic dysfunction(DD)happens early in the progress of CKD,and is the most common cause of CV mortality in the CKD polulation,but the mechanism is still less understood.The high prevalence of traditional cardiovascular risk factors(e.g.hypertension,diabetes,dyslipidema,and RAAS activation)does not fully explain this augmented cardiovascular risk.Uremic toxins,among other metabolites,accumulate in patients with chronic kidney disease,and these are potentially damaging to cardiovascular system.One uremic toxin,indoxyl-sulfate(IS),has been found to associate with DD previously.The present study tried to find the effects of another uremic toxin,p-cresyl sulfate(PCS),on cardiac dysfunction,since previous studies had revealed the adverse effects of PCS on cardiovascular system repeatly.Methods1.The association of PCS and left ventricular(LV)diastolic dysfunction in the clinical setting was investigated.170 patients underwent hemodialysis(HD)treatment for more than 6 months were selected.Exclusion criteria: 1)previous history of CVD(coronary artery disease,myocardial infarction,valvular heat disease,atria fibrillation,and sever arrhythmia),2)malignant tumor,3)systemic disease such as systemic lupuserythematosus,4)LV systolic dysfunction,defined as LV ejection fraction <50%.Blood samples from HD patients were collected and biochemical data,including albumin,hemoglobin,alanine aminotransferase(ALT),aspartate aminotransferase(AST),blood urea nitrogen(BUN),creatinine(CRE),Triglycerides,Total Cholesterol,high-density lipoprotein-cholesterol(HDL-C),low-density lipoprotein-cholesterol(LDL-C),C-reactive protein(CRP),tumor necrosis factor-alpha(TNF-a),and B-type natriuretic peptide(BNP)were measured.After blood sampling,echocardiography was performed in each patient.Parameters of the cardiac cycle were recorded by M-mode echocardiography,and aorta ascendens(AAO),left atrial(LA),LV diastolic diameter,LV systolic diameter,interventricular septum(IVS),LV posterior wall(LVPW),and LV ejection fraction(LVEF)were calculated.The mitral and pulmonary venous flow were measured using pulsed Doppler echocardiogram including peak flow velocity of early diastole(E),peak flow velocity of atrial contraction(A).The mitral annular peak early myocardial tissue velocity(E')and peak late(or atrial)myocardial tissue velocity(A')were measured using tissue-doppler imaging.E/E' ratio was then calculated.LV diastolic dysfunction was defined as E/E'>15.Plasma free and total PCS levels were also measured with high-performance liquid chromatography tandem mass spectrometry(HPLC-MS/MS).To examine the correlations between PCS and other variables,Spearman and Pearson test were used.Logistic regression was used for multivariate analysis of independent variables.2.The pharmacokinetics of PCS in mice with variable renal function was measured.Male Balb/c mice subjected to 5/6 nephrectomy(CRF),unilateral nephrectomy(UNX),or no surgery(controls)were given PCS(po,50 mg/kg).Blood samples were obtained from the retro-orbital venous plexus before and 15,30,60,120,180,and 240 min after PCS gavage.Plasma PCS concentrations were measured with HPLC-MS/MS.The elimination rate constant(K),half-life(t1/2),area under the concentration-time curve(AUC),and total clearance(CLt)of PCS in mice with variable kidney function were estimated.3.C57/BL mice were subjected to uninephrectomy(UNX)and then divided intoPCS-treated and control groups.The PCS-treated mice were fed with 0.5 mg/ml PCS dissolved in double distilled water for 12 weeks.In the contrast,the control mice received daily double distilled water.Blood pressure(BP),heart rate,and plasma biochemistry at the end the experiment were measured to calculate the characters in PCS-treated and control groups.To determine whether PCS treatment had any effect on mice's cardiac function,M-mode echocardiography with the small animal echocardiography analysis system was performed.LV systolic and diastolic diameters,LV systolic and diastolic volumes,stroke volume,LF mass,ejection fraction,fraction shortening,cardiac output,IVS diameters,LVPW diameters,and E/E' ratio were calculated.Plus,haemodynamic measurement was performed with a 1.4 F micro-conductance pressure catheter positioned in the LV through right external carotid artery.Systolic function was quantified by LV end-systolic pressure(ESP)and the slope of the ESP–volume relationship(ESPVR).Diastolic function was measured by LV end-diastolic pressure(LVEDP)and end diastolic pressure–volume relationship(EDPVR),which is an indicator of LV stiffness,as determined from an exponential fit to the end-diastolic pressure–volume points.Finally,plasma samples were collected from each mice,and interleukin(IL)-1?,IL-6,TNF-a,and monocyte chemotactic protein(MCP)-1 were measured.Results1.Of the 170 patients,a significantly greater prevalence of LV diastolic dysfunction was present in patients with higher plasma PCS levels(? 0.85 ?g/ml)than those with lower plasma PCS levels(< 0.85 ?g/ml).2.Over 4 h,PCS was significantly higher in the plasma of CRF mice(63.28 ± 2.76mg/L),compared to UNX mice(3.11 ± 0.64 mg/L)and controls(0.39 ± 0.12 mg/L).The PCS half-life was greatest in CRF mice(12.07 ± 0.12 h),compared to 0.79 ± 0.04 h in UNX mice and 0.48 ± 0.02 h in control mice.However,the potential presence of additional uremic toxins along with PCS in CRF mice and rapid PCS clearance in control mice suggest that the UNX mouse would be a better PCS model to study toxicity.3.Animal study revealed a significantly greater prevalence of LV diastolic dysfunction in PCS-treated mice than control group.Conclusion1.LV diastolic dysfunction was associated with plasma free PCS levels in CKD patients.2.UNX mouse would be a better model to study PCS toxicity.3.PCS contributes to diastolic dysfunction and that targeting PCS may be a therapeutic strategy in CKD.