PPDS: dr. Reagan Paulus Rintar Aruan

PPDS: dr. Reagan Paulus Rintar AruanJOURNAL READINGPosttranscriptional Changes of Serum Albumin:Clinical and Prognostic Significance in Hospitalized Patients With Cirrhosis

ABSTRACTINTRODUCTIONHuman serum albumin (HSA) is the most abundant plasma protein, and its oncotic power largely determines the fluid distribution in the different compartments of the body

Besides its oncotic capacity, HSA presents other biological properties, such as antioxidant and scavenging activities, binding and transport of many endogenous and exogenous substances, and regulation of endothelial function and inflammatory responsePhysiological conditions, the occurrence of low-level posttranscriptional changes, resulting from oxidation, glycosylation, and truncation involving the Cys-34 and other molecular sites, contributes to the microheterogeneity of the circulating molecule

In patients with advanced liver disease, HSA is immersed in a stressful microenvironment as a result of the elevated serum concentration of proinflammatory and pro-oxidant substances

INTRODUCTIONDiabetes is present in approximately one third of patients with cirrhosis, additional stress can also derive from hyperglycemia. besides the universal finding of hypoalbuminemia, a significant damage of the molecule can be expected in these patients. And, indeed, the reversible and irreversible oxidation of the Cys-34 residue occurs in advanced cirrhosis

Furthermore, the circulating level of ischemia modified albumin, which predominantly reflects the cobaltchelating activity at the N-terminal portion,6 is significantly increased in patients with acute-on-chronic liver failure

INTRODUCTIONIn the present study, we first analyzed the HAS posttranscriptional changes in a large cohort of patients with cirrhosis admitted to the hospital because of a clinical complication of the disease.

Then, we assessed whether these HSA isoforms are associated with the severity of disease, specific clinical features, and patient prognosis.INTRODUCTIONPATIENTS AND METHODSFrom July 2011 to March 2012, all the patients with cirrhosis admitted to our department

The diagnosis of cirrhosis was based on clinical, biochemical, ultrasound (US), and endoscopic featuresExclusion criteria Age under 18 yearsAdmission for a scheduled procedureHepatocellular carcinoma (HCC) exceeding the Milan criteriaHeart and respiratory failureOrganic renal diseasesOncohematologic disordersProtein-losing syndromesAlbumin infusion in the previous monthOngoing immunosuppressive treatment.Study DesignAt the time of inclusion for outpatients with cirrhosis and controls, and within 24 hours from admission for hospitalized patients, peripheral blood was withdrawn from the brachial vein into pyrogen-free tubes

Blood samples were immediately centrifuged at 3,000xg for 10 minutes, and plasma was aliquoted into cryotubes, and stored at -80C until analysisPosttranscriptional HSA molecular changes were identified and quantified by using a high-performance liquid chromatography/electrospray ionization mass spectrometry technique.

Study DesignClinical and biochemical parameters were also recorded and hospitalized

Patients were followed for up to 1 year.

7 HSA isoforms carrying one or more posttranscriptional changes were identifiedStudy DesignStatistical AnalysisVariables were expressed as mean and SD or frequencies according to their distribution.

Comparisons between categorical variables were made by means of the chi-square (x2) test.

Differences in HSA isoform relative abundance between control subjects, outpatients, and hospitalized patients with cirrhosis were assessed by one-way analysis of variance (ANOVA) with Bonferronis correction for multiple comparisonsThe relationship between relative abundance of HSA isoforms and MELD and Child-Pughscores was evaluated with Spearmans rho.

The univariate analysis of the association between HAS isoforms relative amount, age, MELD and Child-Pugh scores, and specific clinical complication (ascites, renal impairment, and bacterial infection) in hospitalized patients was assessed by means of the Student t test

The association between HSA isoforms, serum albumin concentration, and 1-year survival was assessed using Coxs proportional hazard method.

Statistical AnalysisThe best cutoffs of HSA isoforms significantly associated with patients survival and of serum albumin concentration were determined through receiver operating characteristic (ROC) curve analysis in order to plot survival curves using Kaplan-Meiers method

All tests were two sided, and values of P < 0.05 were considered statistically significant.

The analyses were performed using SPSS Statistics 20.0 softwareStatistical AnalysisTable 1. Clinical Characteristics of PatientsWith Cirrhosis at Study Enrollment

Data are presented as mean SD or frequencies (%).*Renal impairment = serum creatinine >1.5 mg/dL.

Prothrombin time international normalized ratio.RESULTS

Fig. 1. Representative deconvoluted ESI-MS spectra from a control subject (A) and a patient with cirrhosis (B). In addition to native HSA, seven HSA isoforms carrying the following structural alterations were detected: truncation of the last two amino acid residues at the Nterminal portion (HSA-DA); truncation of the last amino acid residue at the C-terminal portion (HSA-L); cysteinylation of the Cys-34 residue (HSA1CYS); sulfinylation of the Cys-34 residue (HSA1SO2H); and glycosylation (HSA1GLYC). Two additional HSA isoforms were generated from the combination of the cysteinylated with the N-terminal truncated form (HSA1CYS-DA) or the glycosylated form (HSA1CYS1GLYC).

DISCUSSIONSIn this study, posttranscriptional structural changes of albumin in cirrhosis were assessed by HPLC/ESIMS for the first time.

This proteomic technique provides a spectrum of molecules with high resolution, discriminating between isoforms whose molecular weight differs by a few Daltons

Fig. 3. Kaplan-Meiers survival curves for HSA1CYS-DA (A), nativeHSA (B), and serum albumin concentration (C) in hospitalized patients with cirrhosis dichotomized according their best cut-off valuesassessed by ROC curve analysisThe first important finding of the present study is that the molecular structure of HSA is extensively altered in patients with cirrhosis. Indeed, the extent of many posttranscriptional molecular changes, which can also be detected at a low, physiological level in healthy subjects, was significantly increased in patientsDISCUSSIONSCONCLUSIONSExtensive posttranscriptional changes of HSA, involving several molecular sites and increasing in parallel with disease severity, occur in patients with cirrhosis.Altered isoforms are independently associated with specific clinical complications, whereas the residual, native HSA isoform independently predicts patient survival. These findings support the concept of the effective albumin concentration, which implies that the global HSA function is related not only to its serum concentration, but also to the preservation of its structural integrity.