Microheterogeneity of serum glycoproteins in alcoholics: is desialo-transferrin the marker of chronic alcohol drinking or alcoholic liver injury?

Systems Pharmacology Study of the Anti-Liver Injury Mechanism of Citri Reticulatae Pericarpium

Liver diseases are mostly triggered by oxidative stress and inflammation, leading to extracellular matrix overproduction and prone to develop into liver fibrosis, cirrhosis and hepatocellular carcinoma. Liver injury (LI) refers to various pathogenic factors leading to the destruction of stem cells that then affect the liver's normal function, causing a series of symptoms and abnormal liver function indicators. Citri Reticulatae Pericarpium (CRP) is one of the most commonly used traditional Chinese medicines; it contains flavonoids including hesperidin, nobiletin, and tangeretin. CRP has antibacterial, antioxidant, and antitumor effects that reduce cholesterol, prevent atherosclerosis and decrease LI. Here we analyzed the components of CRP and their targets of action in LI treatment and assessed the relationships between them using a systems pharmacology approach. Twenty-five active ingredients against LI were selected based on ultra-performance liquid chromatography-quadrupole/time-of-flight mass spectrometry results and databases. The drug targets and disease-related targets were predicted. The 117 common targets were used to construct a protein-protein interaction network. We identified 1719 gene ontology items in LI treatment, including 1,525 biological processes, 55 cellular components, and 139 molecular functions. These correlated with 49 Kyoto Encyclopedia of Genes and Genomes pathways. These findings suggest that CRP may counteract LI by affecting apoptotic, inflammatory, and energy metabolism modules. In vitro experiments suggested that the mechanism may involve hesperidin and naringenin acting on CASP3, BAX, and BCL2 to affect the apoptosis pathway, attenuating liver fibrosis. Naringenin significantly inhibited AKT1 phosphorylation, which in turn mediated activation of the phosphoinositide 3-kinase-Akt signaling pathways against LI. This study provides a reference for systematically exploring the mechanism of CRP's anti-LI action and is also expands of the application of systems pharmacology in the study of traditional Chinese medicine.

Changes in the expression of N- and O-glycopeptides in patients with colorectal cancer and hepatocellular carcinoma quantified by full-MS scan FT-ICR and multiple reaction monitoring

Alternations in the glycosylation of proteins have been described in connection with several cancers, including hepatocellular carcinoma (HCC) and colorectal cancer. Analytical tools, which use combination of liquid chromatography and mass spectrometry, allow precise and sensitive description of these changes. In this study, we use MRM and FT-ICR operating in full-MS scan, to determine ratios of intensities of specific glycopeptides in HCC, colorectal cancer, and liver metastasis of colorectal cancer. Haptoglobin, hemopexin and complement factor H were detected after albumin depletion and the N-linked glycopeptides with fucosylated glycans were compared with their non-fucosylated forms. In addition, sialylated forms of an O-linked glycopeptide of hemopexin were quantified in the same samples. We observe significant increase in fucosylation of all three proteins and increase in bi-sialylated O-glycopeptide of hemopexin in HCC of hepatitis C viral (HCV) etiology by both LC-MS methods. The results of the MRM and full-MS scan FT-ICR analyses provide comparable quantitative readouts in spite of chromatographic, mass spectrometric and data analysis differences. Our results suggest that both workflows allow adequate relative quantification of glycopeptides and suggest that HCC of HCV etiology differs in glycosylation from colorectal cancer and liver metastasis of colorectal cancer.

SIGNIFICANCE

The article compares N- and O-glycosylation of several serum proteins in different diseases by a fast and easy sample preparation procedure in combination with high resolution Fourier transform ion cyclotron resonance mass spectrometry. The results show successful glycopeptides relative quantification in a complex peptide mixture by the high resolution instrument and the detection of glycan differences between the different types of cancer diseases. The presented method is comparable to conventional targeted MRM approach but allows additional curation of the data.

Altered glycomics in liver disease

Chronic liver diseases are a serious health problem worldwide. The biosynthesis of proteins takes place in the liver, and protein glycosylation is the most common form of post-translational modification of proteins, with as many as 70% of all human proteins estimated to contain one or more glycan chains. Protein glycosylation is the enzymatic addition of sugars or oligosaccharides to proteins, which increases the diversity of the proteome to a level unmatched by any other post-translational modifications because of the various aspects of modification, including glycosidic bond, glycan composition, glycan structure, and glycan length. Changes in the glycan structures of proteins are an indication for liver damage, which plays an important role in the pathogenesis and progression of various liver diseases. The aim of this paper is to give an overview of the altered protein glycosylation in different etiologies of hepatitis, liver fibrosis/cirrhosis, hepatocellular carcinoma, alcoholic and fatty liver diseases based on the analysis of serum and saliva using the glycomics technology.

Protein and site specificity of fucosylation in liver-secreted glycoproteins

Chronic liver diseases are a serious health problem worldwide. One of the frequently reported glycan alterations in liver disease is aberrant fucosylation, which was suggested as a marker for noninvasive serologic monitoring. We present a case study that compares site specific glycoforms of four proteins including haptoglobin, complement factor H, kininogen-1, and hemopexin isolated from the same patient. Our exoglycosidase-assisted LC–MS/MS analysis confirms the high degree of fucosylation of some of the proteins but shows that microheterogeneity is protein- and site-specific. MSn analysis of permethylated detached glycans confirms the presence of LeY glycoforms on haptoglobin, which cannot be detected in hemopexin or complement factor H; all three proteins carry Lewis and H epitopes. Core fucosylation is detectable in only trace amounts in haptoglobin but with confidence on hemopexin and complement factor H, where core fucosylation of the bi-antennary glycans on select glycopeptides reaches 15–20% intensity. These protein-specific differences in fucosylation, observed in proteins isolated from the same patient source, suggest that factors other than up-regulation of enzymatic activity regulate the microheterogeneity of glycoforms. This has implications for selection of candidate proteins for disease monitoring and suggests that site-specific glycoforms have structural determinants, which could lead to functional consequences for specific subsets of proteins or their domains.

Total and free serum sialic acid concentration in liver diseases

Background. The objective of this study was to compare the levels of total (TSA) and free (FSA) sialic acid in acute and chronic liver diseases. Materials and Methods. The serum TSA and FSA levels were determined in 278 patients suffering from acute and chronic liver diseases of different etiologies. TSA was estimated by enzymatic method and FSA by the thiobarbituric method modified by Skoza and Mohos. Results. There were no significant differences in the serum TSA concentration between liver diseases of different etiologies, although in most of the liver diseases the mean TSA level was significantly lower than that in the control group. In contrast to TSA, the concentration of FSA appears to differ between liver diseases. In toxic hepatitis it was higher than that in nonalcoholic cirrhosis. However, neither of them differs between alcoholic and nonalcoholic cirrhosis or between liver tumors and tumors with cirrhosis. Conclusions. We conclude that the changes in concentrations of TSA and FSA during the same liver diseases indicate significant disturbances in sialylation of serum glycoproteins.

Site-specific glycoforms of haptoglobin in liver cirrhosis and hepatocellular carcinoma

Haptoglobin is a liver-secreted glycoprotein with four N-glycosylation sites. Its glycosylation was reported to change in several cancer diseases, which prompted us to examine site-specific glycoforms of haptoglobin in liver cirrhosis and hepatocellular carcinoma. To this end, we have used two-dimensional separation composed of hydrophilic interaction and nano-reverse phase chromatography coupled to QTOF mass spectrometry of the enriched glycopeptides. Our results show increased fucosylation of haptoglobin in liver disease with up to six fucoses associated with specific glycoforms of one glycopeptide. Structural analysis using exoglycosidase treatment and MALDI-MS/MS of detached permethylated glycans led to the identification of Lewis Y-type structures observed particularly in the pooled hepatocellular carcinoma sample. To confirm the increase of the Lewis Y structures observed by LC-MS, we have used immunoaffinity detection with Lewis Y-specific antibodies. The presence of multiply fucosylated Lewis Y glycoforms of haptoglobin in the disease context could have important functional implications.

CYP2E1, oxidative stress, post-translational modifications and lipid metabolism

Chronic alcohol-mediated down-regulation of hepatic ST6Gal1 gene leads to defective glycosylation of lipid-carrying apolipoproteins such as apo E and apo J, resulting in defective VLDL assembly and intracellular lipid and lipoprotein transport, which in turn is responsible for alcoholic hepatosteatosis and ALD. The mechanism of ethanol action involves thedepletion of a unique RNA binding protein that specifically interacts with its 3'-UTR region of ST6Gal1 mRNA resulting in its destabilization and consequent appearance of asialoconjugates as alcohol biomarkers. With respect to ETOH effects on Cardio-Vascular Diseases, we conclude that CYP2E1 and ETOH mediated oxidative stress significantly down regulates not only the hepatic PON1 gene expression, but also serum PON1 and HCTLase activities accompanied by depletion of hepatic GSH, the endogenous antioxidant. These results strongly implicate the susceptibility of PON1 to increased ROS production. In contrast, betaine seems to be both hepatoprotective and atheroprotective by reducing hepatosteatosis and restoring not only liver GSH that quenches free radicals, but also the antiatherogenic PON1 gene expression and activity.

Alteration of protein glycosylation in liver diseases

Chronic liver diseases are a serious health problem worldwide. The current gold standard to assess structural liver damage is through a liver biopsy which has several disadvantages. A non-invasive, simple and non-expensive test to diagnose liver pathology would be highly desirable. Protein glycosylation has drawn the attention of many researchers in the search for an objective feature to achieve this goal. Glycosylation is a posttranslational modification of many secreted proteins and it has been known for decades that structural changes in the glycan structures of serum proteins are an indication for liver damage. The aim of this paper is to give an overview of this altered protein glycosylation in different etiologies of liver fibrosis / cirrhosis and hepatocellular carcinoma. Although individual liver diseases have their own specific markers, the same modifications seem to continuously reappear in all liver diseases: hyperfucosylation, increased branching and a bisecting N-acetylglucosamine. Analysis at mRNA and protein level of the corresponding glycosyltransferases confirm their altered status in liver pathology. The last part of this review deals with some recently developed glycomic techniques that could potentially be used in the diagnosis of liver pathology.

Liver Galbeta1,4GlcNAc alpha2,6-sialyltransferase is down-regulated in human alcoholics: possible cause for the appearance of asialoconjugates

Galbetal,4GlcNAc alpha2,6-sialyltransferase (ST6GalI) mediates the glycosylation of proteins and lipids to form functionally important glycoproteins and glycolipids in the Golgi compartment. Our previous work demonstrated that long-term ethanol feeding in rats caused a marked 59% decrease in ST6GalI activity as well as ST6GalI messenger RNA (mRNA) level in the liver that was due to decreased stability of the mRNA. Clinical observations show that down-regulation of ST6GalI gene and consequent impaired activity of ST6GalI seems to be the major cause for the appearance of asialoconjugates in the blood of long-term alcoholics. The plasma carbohydrate-deficient transferrin (CDT) and sialic acid index of plasma apolipoprotein J were also altered in the alcoholic group compared with the nondrinkers. We have now investigated how alcohol affects the gene regulation of ST6GalI and the possible mechanism in postmortem human liver specimens taken from nondrinkers, moderate alcohol drinkers, and heavy alcohol drinkers. Real-time polymerase chain reaction analyses of the liver RNA extract showed that ST6GalI mRNA level was progressively decreased by 49% in moderate drinkers (P < .01) and by 69% in heavy drinkers (P < .01) compared with nondrinkers. Western blot analysis showed that liver ST6GalI protein level was negligibly decreased in moderate drinkers but decreased by 30% (P < .05) in heavy drinkers compared with nondrinkers. We further demonstrated a single ST6GalI mRNA-binding protein complex in the normal human liver extract, which progressively decreased in the liver extracts of moderate and heavy alcohol drinkers. Thus, it is concluded that the appearance of asialoconjugates in alcoholics is possibly due to the down-regulation of ST6GalI gene expression.

Relationship between serum sialic acid and sialylated glycoproteins in alcoholics

AIMS

Total sialic acid (TSA) has been suggested as a marker for chronic alcohol abuse. It seems that the elevation of TSA during excessive alcohol consumption reflects the changes in sialylated glycoproteins in the sera. On the other hand, chronic ethanol consumption increases the desialylation rate of many serum glycoproteins. The aim of this study was to evaluate the relationship between the total and free form of sialic acid levels (FSA), and the concentration of sialylated glycoproteins in alcoholics.

METHODS

We determined the serum concentration of many glycoproteins (alpha1-antitrypsin, alpha1-acid glycoprotein, haptoglobin, ceruloplasmin, transferrin, complement C3 protein, fibrinogen and immunoglobulin G) in a sample of 100 alcoholics and 30 healthy controls. Total sialic acid was determined by the enzymatic method and its free form by using a modification of the thiobarbituric acid method.

RESULTS

Among alcoholics, we found increased concentrations of alpha1-antitrypsin and alpha1-acid glycoprotein but decreased levels of transferrin. The concentrations of TSA and FSA were significantly higher in alcoholics than in healthy controls. The tested glycoproteins, except for transferrin and immunoglobulin G, positively correlated with TSA and FSA. The correlations with TSA were higher than that with FSA.

CONCLUSIONS

Chronic alcohol abuse alters the concentrations of some sialylated glycoproteins in the sera. The alpha1-antitrypsin, alpha1-acid glycoprotein, and transferrin are the only affected glycoproteins. The serum level of total and free form of sialic acid in the sera of alcoholics depends on the concentration of the most sialylated glycoproteins.

Serum free sialic acid as a marker of alcohol abuse

BACKGROUND

Previous studies have shown that serum total sialic acid (TSA) concentration significantly increases during alcohol abuse. Chronic ethanol consumption impairs glycosylation of many proteins. The increased desialylation rate of serum glycoproteins is one of the effects of alcohol abuse. The aim of this study was to investigate the diagnostic value of free sialic acid (FSA) as a marker of alcohol abuse.

METHODS

We determined serum FSA concentrations in the group of 156 alcoholic subjects and 35 healthy control subjects by means of a modification of the thiobarbituric acid method. The alcoholic group was divided into subgroups according to their history of abuse.

RESULTS

The FSA concentration was significantly higher in alcoholic subjects than in healthy controls. The subjects who consumed alcohol for longer than a week showed significantly higher FSA level than those who consumed alcohol for a shorter period. The serum FSA concentration was significantly higher in alcoholic subjects with elevated markers of liver dysfunction. The diagnostic accuracy of FSA was high, although it did not differ from TSA, and was limited by its low sensitivity.

CONCLUSIONS

This study shows that FSA concentration in the sera of alcoholic subjects is increased. The low diagnostic sensitivity is accompanied by high specificity, however the accuracy is high and similar to the accuracy of TSA. Free sialic acid does not seem to be a better marker of alcohol abuse than TSA and current markers.

Comparison of the combined marker GGT-CDT and the conventional laboratory markers of alcohol abuse in heavy drinkers, moderate drinkers and abstainers

AIMS

A combined index based on gamma-glutamyltransferase (GGT) and carbohydrate-deficient transferrin (CDT) measurements (GGT-CDT) has been recently suggested to improve the detection of excessive ethanol consumption. The aim of this work was to compare GGT-CDT with the conventional markers of alcohol abuse in individuals with a wide variety of alcohol consumption.

METHODS

A cross-sectional and follow-up analysis was conducted in a sample of 165 heavy drinkers, consuming 40-540 g of ethanol per day, and 86 reference individuals who were either moderate drinkers (n = 51) or abstainers (n = 35).

RESULTS

GGT-CDT (5.35 +/- 1.08) in the heavy drinkers was significantly higher than in the reference individuals (3.30 +/- 0.37). The sensitivity of GGT-CDT (90%) in correctly classifying heavy drinkers exceeded that of CDT (63%), GGT (58%), mean corpuscular volume (MCV) (45%), aspartate aminotransferase (AST) (47%), and alanine aminotransferase (ALT) (50%), being also essentially similar for alcoholics with (93%) or without (88%) liver disease. When comparing the data using either moderate drinkers or abstainers as reference population, the sensitivity of GGT-CDT, CDT, and ALT remained unchanged whereas the sensitivity of GGT, MCV, and AST was found to show variation.

CONCLUSIONS

GGT-CDT improves the sensitivity of detecting excessive ethanol consumption as compared with the traditional markers of ethanol consumption. These findings should be considered in the assessment of patients with alcohol use disorders.

Chronic ethanol consumption upregulates the cytosolic and plasma membrane sialidase genes, but down regulates lysosomal membrane sialidase gene in rat liver

We have previously shown that chronic ethanol feeding stimulates liver cytosolic sialidase (CS) and plasma membrane sialidase (PMS), whereas it decreases lysosomal membrane sialidase (LMS) activities with concomitant alterations in their relative synthetic rate in rat. To understand the molecular mechanism(s) for these changes, we have evaluated the effect of ethanol administration in male Wistar rats as a function of increasing dietary ethanol concentration after 8 weeks of pair-feeding on (i) the expression of CS, PMS, and LMS genes by real-time quantitative polymerase chain reaction method; (ii) their relative transcription rates by nuclear run-on assay; and (iii) the actual amount of these sialidase proteins in the liver fractions of the respective groups by Western blot method. We have demonstrated that the animals fed with 10.6%, 20.8%, and 36% of total calories as ethanol showed a 20% (P<.05), 34% (P<.01), and 69% (P<.01) increase in CS mRNA level, and 22% (P<.05), 26% (P<.01), and 47% (P<.01) increase in PMS mRNA level, but a decrease in LMS mRNA level by 35% (P<.05), 50% (P<.01), and 80% (P<.01), respectively, as compared to controls. Western blot analyses of CS, PMS, and LMS in the liver subfractions showed that changes in protein levels of CS, LMS, and PMS were consistent with the corresponding changes in the respective mRNA levels. Thus, the upregulation of CS and PMS, but not LMS which is down regulated by chronic ethanol, may account for the appearance of asialoconjugates in alcoholics.

Ethanol destabilizes liver Gal beta l, 4GlcNAc alpha2,6-sialyltransferase, mRNA by depleting a 3'-untranslated region-specific binding protein

Asialoconjugates are viable biomarkers for alcohol abuse. We previously showed that chronic ethanol feeding down-regulated liver Gal beta l, 4GlcNAc alpha2,6-sialyltransferase (ST6Gal l) mRNA by destabilizing it. Since RNA-binding proteins are known to stabilize many eukaryotic mRNAs by interacting with the 3'-untranslated region (UTR), we have delineated the possible mechanism by which ethanol destabilizes ST6Gal l mRNA. Using (32)P-labeled RNA probes generated from a 2.7-kb 3'-UTR of ST6Gal l mRNA, we identified a liver cytosolic 41-kDa specific binding protein that interacts with its 3'-UTR domain and protects it from degradation in normal rat liver but disappears after chronic ethanol treatment. Mapping of the binding region revealed that four RNA probes of 80-base pair (bp) length spanning the 304 bp of the 3'-UTR of ST6Gal l mRNA showed equal binding intensity. The corresponding cDNA sequences for the four 80-bp RNA probes share the 13-bp consensus sequence. Mutagenesis analysis identified that four nucleotides, AG and TC, among the consensus sequences were critical for the RNA-protein interaction. Therefore, 5'-CAGCCTCCTCCCT-3' serves as a cis-element critically involved in this interaction. The RNA-protein complex formation progressively decreased with increasing dietary ethanol, resulting in its virtual disappearance with 36% of the dietary calories as ethanol. Concomitantly, the same ethanol diet decreased sialic acid index of plasma apolipoprotein J by 45% (p < 0.05). Thus, depletion of a binding protein that specifically interacts with its 3'-UTR region of ST6Gal l mRNA may account for its destabilization and consequent appearance of asialoconjugates as alcohol biomarkers.

The diagnostic accuracy of carbohydrate-deficient transferrin, sialic acid and commonly used markers of alcohol abuse during abstinence

BACKGROUND

The normalization of alcohol abuse markers during the abstinence depends on the time since the last drinking. The aim of this study was to evaluate the diagnostic accuracy (area under the curve-AUC, sensitivity and specificity) of CDT, sialic acid and others biochemical and hematological markers of chronic alcohol abuse during abstinence.

METHODS

We studied 75 patients admitted to the treatment of alcohol dependence. The blood samples were collected upon admission to the hospital. CDT was estimated using an immunoturbidimetric assay after anion-exchange chromatography and sialic acid by enzymatic colorimetric method.

RESULTS

Mean values of all markers were significantly higher. All tests, except SA, negatively correlated with time of abstinence but not with age, duration of dependence and amounts of weekly alcohol consumption. The area under the curve (AUC) for all tested markers decreased progressively during the abstinence. The highest AUC was obtained for CDT (0.98) and the lowest for ALT (0.78) when alcohol was consumed in the last week. AUC for sialic acid was lower than of CDT but higher than of ALT.

CONCLUSIONS

We conclude that the diagnostic accuracy for tested laboratory markers depends on the self-reported time of abstinence being the highest for CDT in the first week of abstinence. The accuracy of sialic acid was observed between GGT and ALT.

Chronic ethanol feeding controls the activities of various sialidases by regulating their relative synthetic rates in the rat liver

We have determined the concentration effects of feeding for 8 weeks 10.8%, 21.6%, and 36% dietary ethanol calories on the activities and relative synthetic rates (RSRs) of various subcellular sialidases of rat liver. The hepatic RSRs of each species of sialidase was determined based on the ratio of 1-hour incorporation of [35S]-methionine into immunoprecipitable sialidase as percent of the incorporation into total protein in each subcellular fraction. Ganglioside sialidase activities in the hepatic subcellular fractions were also determined. Ethanol feeding at 36% dietary calories caused an increase in the ganglioside sialidase activity of the plasma membrane sialidase (PMS) by 232% (P < .01) and that of cytosolic sialidase (CS) by 184% (P < .05), but decreased the lysosomal membrane sialidase (LMS) by 54% (P < .01) when compared with the control animals. The specificity of each antisialidase antibody was verified by immunoblots. The RSR of PMS was increased by 40% (P < .01), 67% (P < .01), and 220% (P < .01) in the 10.8%, 21.6%, and 36% ethanol groups, respectively. Similarly, the RSR of CS was increased by 17% (P < .01), 19% (P < .01), and 63% (P < .01), respectively, in these ethanol groups. In contrast, the RSR of LMS was inhibited by 36% (P < .01), 34% (P < .01), and 69% (P < .01), respectively, in these ethanol groups. Intralysosomal sialidase failed to hydrolyze gangliosides. Thus, PMS and CS, but not LMS or intralysosomal sialidase, may play important roles in ethanol-modulated desialylation of gangliosides and consequent liver injury and behavioral alterations.

Mechanism of action of ethanol in the down-regulation of Gal(beta)1, 4GlcNAc alpha2,6-sialyltransferase messenger RNA in human liver cell lines

Gal beta l, 4GlcNAc alpha 2,6-sialyltransferase (2,6-ST) mediates the addition of alpha 2,6-linked sialic acid to glycoproteins in the Golgi compartment. Down-regulation of its gene and consequent impaired activity of 2,6-ST seems to be the major cause for the appearance of asialoconjugates in the blood of long-term alcoholics. Therefore, mechanism(s) involved in the regulation of 2,6-ST gene is important and clinically relevant. Our previous work showed that long-term ethanol feeding in rats caused a marked 59% decrease of 2,6-ST activity as well as 2,6-ST messenger RNA (mRNA) level in liver that were due to the decreased stability of its mRNA. We now mimic these actions of ethanol using ( a ) human liver HepG2 cells stably transfected with ethanol-inducible human cytochrome P4502E1 (CYP2E1 cells), or ( b ) with high alcohol dehydrogenase (HAD cells) but not in wild-type HepG2 cells lacking either of the above 2 enzymes as models. Incubation of these cells for 72 hours with 100 mmol/L ethanol caused decreases (up to 76%, P < .05) of 2,6-ST mRNA levels in CYP2E1 and HAD cells but not in the wild type. However, incubation of wild-type cells with acetaldehyde at concentrations of 50 and 100 micro mol/L showed a dramatic decrease (up to 69%, P < .02) in the 2,6-ST mRNA levels. Furthermore, exposure of CYP2E1 cells to 4-hydroxy-2-nonenal, an endogenous lipid peroxidation product of reactive oxygen species, strongly decreased 2,6-ST mRNA level by 61% ( P < .02). These results demonstrate that 2,6-ST gene is highly sensitive to ethanol action in human liver cells either via its oxidation product, acetaldehyde, or via reactive oxygen species leading to the generation of a more reactive aldehyde such as 4-hydroxy-2-nonenal. Thus, this study assumes major importance and clinical relevance because 2,6-ST gene regulation in a human liver cell model is demonstrated within a few days of ethanol exposure, whereas its in vivo regulation in liver generally takes prolonged period of ethanol exposure.

A new modified γ-%CDT method improves the detection of problem drinking: studies in alcoholics with or without liver disease

BACKGROUND

The detection of excessive alcohol consumption by laboratory methods continues to lack sensitivity and specificity. Recent studies have suggested that diagnostic improvement may be achieved by combining carbohydrate-deficient transferrin (CDT) and gamma-glutamyltransferase (GT) measurements into a marker defined as gamma-CDT.

METHODS

We developed a new approach for determining gamma-CDT by using the data obtained from the Axis %CDT turbidimetric assays. Marker results were compared in the assessment of 65 alcoholics, who were either with (n=34) or without (n=31) liver disease, as analysed by clinical, laboratory, and morphological criteria. Reference individuals were 45 healthy volunteers who were either social drinkers or abstainers.

RESULTS

Gamma-GT and CDT results derived from both CDTect and %CDT measurements were used to calculate marker ratios as follows 0.8 x ln(GT)+1.3 x ln(CDT). With the established cut-off of 4.0 for the gamma-%CDT, the sensitivity of this method was 94% for men and 82% for women, as compared to 61% and 46% for %CDT and 70% and 73% for GT. The gamma-%CDT method was less dependent on liver status than the various other markers and showed the highest correlation with self-reported alcohol consumption (r=0.7254).

CONCLUSIONS

The data indicates that the new gamma-%CDT method yields improved diagnostic accuracy for the detection of excessive ethanol consumption.

Diagnostic characteristics of different carbohydrate-deficient transferrin methods in the detection of problem drinking: effects of liver disease and alcohol consumption

AIMS

Due to methodological heterogeneity, conflicting views have been expressed on the validity of CDT measurements in the detection of alcohol misuse.

METHODS

We compared the characteristics of the conventional CDTect method and the Axis turbidimetric CDT assays in the assessment of 62 alcoholics, who were either with (n = 33) or without (n = 29) liver disease, as analysed by combined clinical, laboratory, and morphological indices. Controls were 45 healthy volunteers who were either social drinkers or abstainers.

RESULTS

In the total sample of alcoholics, the sensitivity of the %CDT method, which excludes the trisialotransferrin isoform from the measurement, was 63% for men and 46% for women, as compared to 65% and 36% of CDTect, respectively. Both of these methods showed higher sensitivities than the %CDT-TIA method, which reacts with trisialotransferrin (32% and 25%, respectively). The assay specificities were 100% for men and 91% for women with %CDT, and 96% and 87% with the CDTect, respectively. The correlation between the CDTect and %CDT method was higher in men (r = 0.86) than in women (r = 0.57). The presence of liver disease was found to influence the results of the CDTect method, such that the highest CDT concentrations were observed in patients with mild to moderate liver disease, especially among women, whereas the %CDT method was less sensitive to the effect of liver pathology. The self-reported alcohol consumption from the 4 weeks prior to sampling showed a higher correlation between the %CDT results (r = 0.64, P < 0.0001) than with the CDTect results (r = 0.40; P < 0.01).

CONCLUSIONS

The data indicate that the new %CDT method offers advantages over the previous versions of the CDT methods. The improved characteristics may be most useful in assays for excessive alcohol consumption in female alcoholics, patients with liver disease, and in patients with abnormal serum transferrin concentrations.

Plasma sialic-acid index of apolipoprotein J (SIJ): a new alcohol intake marker

Although plasma carbohydrate-deficient transferrin (CDT) is considered a viable biochemical marker for chronic alcohol consumption, it is valid only when an individual's daily alcohol consumption exceeds 60 g. In addition, it is less sensitive in women drinkers than in men drinkers. We have established that chronic alcohol consumption impairs the hepatic sialylation of a number of glycoproteins by specifically down-regulating Gal-beta-1,4GlcNAc alpha2,6-sialyltransferase mRNA. Significantly, we found that chronic ethanol consumption markedly inhibits hepatic sialylation of apolipoprotein J (Apo J), a 70-kDa N-glycosylated protein of plasma HDL. Because the sialic-acid index of Apo J (SIJ; moles of sialic acid per mole of Apo J protein) is approximately seven times more than that for transferrin (28 vs. 4), we have evaluated whether plasma SIJ would be an even more sensitive marker for chronic ethanol consumption than CDT in both rats and human subjects. The method involves immunoaffinity purification of plasma HDL-Apo J, followed by its sialic acid determination. We have found that chronic ethanol feeding resulted in loss of sialic acid residues of plasma HDL-Apo J in rats. This loss of sialic acid was positively correlated with both amount and duration of ethanol treatment. In human subjects, an intake of about 60 g of alcohol for 30 days led to almost 50% (P <.01) depletion of sialic acid from plasma HDL-Apo J. Further, we established that there was a positive correlation of alteration in SIJ with alcohol consumption, detoxification, abstinence, and relapse in human alcohol-dependent patients (sensitivity, 90%-92%). In addition, plasma SIJ was decreased by 50%-57% (P <.01) in both male and female alcohol-dependent subjects. We suggest that plasma SIJ can be used as a viable marker for early detection of chronic alcohol consumption in human beings.

Exploiting lectin affinity chromatography in clinical diagnosis

Lectin affinity chromatography (LAC) offers a tool that aids purification of cell surface glycoconjugates in sufficient quantities so that studies addressing their structural elucidation could be carried out. It has several advantages over the conventional biochemical methods, such as immunoprecipitation and/or immunoaffinity chromatography, used for the purification of various glycoconjugates. Serial LAC (SLAC) not only helps establish the identity of a glycoprotein or allows purification of a glycoprotein to homogeneity from among a mixture of glycoproteins, but it also successfully resolves the microheterogeneity in these glycoproteins, which is an otherwise impracticable problem to address. Specific cases of the altered expression and maintenance of microheterogeneity of some of the glycoproteins in pathological conditions vis a vis during normal biology are presented. The application of LAC in (i) itself, (ii) a serial fashion, and (iii) conjunction with other techniques such as two-dimensional electrophoresis, capillary electrophoresis, mass spectrometry, etc. in the diagnosis of certain pathological conditions, and the possibility of using this knowledge in designing treatments for various diseases, is discussed.

Carbohydrate-deficient transferrin and sialidase levels in coronary heart disease

Transferrin is a N-glycosylated glycoprotein and plays an important role in iron transport from sites of absorption and storage to sites of utilization. The main component of normal serum transferrin contains two biantennary glycans, each consisting of 2 mol of sialic acid (Tetrasialo transferrin). Normal serum also contains small amounts of tri- and disialotransferrin. We have undertaken this study to investigate the levels of serum carbohydrate-deficient transferrin (Desialotransferrin) and sialidase levels in patients with coronary heart disease. In patient group, serum desialotransferrin and sialidase levels were found to be significantly higher than control group (p < 0.01 and p < 0.001, respectively). We conclude that increased activity of sialidase may be responsible for increased desialotransferrin in patients with coronary heart disease. Serum desialotransferrin levels may be useful critaria to diagnosis and pathogenesis of coronary heart disease.

Changes of alpha1-acid glycoprotein microheterogeneity in acute inflammation stages analyzed by isoelectric focusing using serum obtained postoperatively

The relationship between variations of alpha1-acid glycoprotein (orosomucoid, AGP) microheterogeneity detected from isoelectric focusing (IEF) patterns and clinical stage of acute inflammation based on serum C-reactive protein (CRP) levels and interleukin-6 (IL-6) levels was investigated. Serum samples were obtained from healthy subjects, and from patients with esophageal or stomach carcinoma before and after operation. Samples without neuraminidase treatment were used for AGP microheterogeneity analysis, and samples with neuraminidase treatment for AGP heterogeneity analysis. In AGP microheterogeneity, nine bands were detected in the range of pI 3.18-3.57 in sera obtained from healthy subjects. In patients, AGP microheterogeneity changed the first day after operation; the percentage of bands surrounding pI 3.5 increased, and the highest value appeared in sera taken the first or second day after operation and then decreased quickly. These bands showed reactivity for concanavalin A (Con A). The increase in Con A-reactive AGP occurred later than the increase in IL-6, and occurred earlier than the increase in CRP. On the seventh day after operation, the percentage of bands around pI 3.2 increased. These bands showed the reactivity for Datura stramonium agglutinin. On the other hand, in samples with neuraminidase treatment, little change of AGP heterogeneity was observed in most samples, which did not reflect the stage of inflammation. These findings suggested that AGP microheterogeneity detection was a useful marker for the clinical stage of inflammation.

New detection method after cellulose acetate membrane isoelectric focusing: activity staining for lactate dehydrogenase, detection for sugar chains using lectin and simple western blotting

To extend the clinical applications for cellulose acetate (CA) membrane isoelectric focusing, we designed two detection methods and two blotting methods that improve the characteristics of the CA membrane; that is, detection of the lactate dehydrogenase (LD) isozyme on the CA membrane, detection of the sugar chain in glycoprotein on the CA membrane, and simple and rapid methods for western blotting. In the detection of the LD isozyme, when 50% saturated ammonium sulfate solution was used as a fixing solution, five main LD bands and seven sub LD bands were detected clearly. By treating the CA membrane with 5% sulfosalicylic acid, glycoprotein was fixed on the CA prior to detection of the sugar chain of glycoprotein using Lens Culinaris (LCA), Phasseolus Vulgaris-L(4 )(PHA-L(4)), Maackia Amurensis (MAM), and Sambucus Siedoldiana (SSA) lectins. Using this procedure, clear electrophoretic patterns were obtained. As simple and rapid methods for blotting proteins on polyvinylidene difluoride membranes, we designed natural contact blotting and suction blotting techniques. The natural contact blotting method did not need special apparatus. The suction blotting method completed protein blotting for 10 minutes. By both methods, clear electrophoretic patterns were obtained.

Carbohydrate deficient transferrin in the assessment of alcohol misuse: absolute or relative measurements? A comparison of two methods with regard to total transferrin concentration

Carbohydrate deficient transferrin (CDT) is now accepted as a potentially useful marker for the detection of alcohol misuse. It is not clear whether absolute values or values expressed relative to the total transferrin concentration provide the same diagnostic efficiency. CDT was measured in 35 patients with alcohol related liver disease, 35 subjects abusing alcohol without evidence of liver disease and 35 patients with chronic viral hepatitis using two commercial methods (CDTect and %CDT). To compare the methods, results were normalised by dividing the actual result by the upper limit of the reference range. Subtracting normalised %CDT results from the normalised CDTect results demonstrated a linear relationship between CDTect and total transferrin. This linear relationship could be abolished by calculating the CDTect/total transferrin ratio. The sensitivity of the methods was similar with CDTect (43 and 57%) being slightly superior to %CDT (40 and 46%). Specificity was similar (78%) for both methods. Calculation of the CDTect/total transferrin ratio improved the sensitivity and specificity slightly. The linear relationship between CDTect and total transferrin may produce misleading results in populations with a high prevalence of abnormal total transferrin concentrations and could cause difficulties in method comparisons unless taken into account.

A comparative study between carbohydrate-deficient transferrin and gamma-glutamyltransferase for the diagnosis of excessive drinking in a liver unit

AIM

To compare the efficacy of carbohydrate-deficient transferrin and gamma-glutamyltransferase for the diagnosis of excessive alcohol intake in patients admitted in a liver unit.

METHODS

The 346 patients were divided into three groups of alcoholics: 57 patients (31 men, 26 women) with a normal liver, 77 patients (51 men, 26 women) with non-cirrhotic alcoholic liver disease, and 61 patients (43 men, 18 women) with alcoholic cirrhosis; and three groups of non-alcoholics: 35 abstainers (21 men, 14 women), and 58 healthy blood donors (26 men, 32 women), and 58 patients (32 men, 26 women) who had a non-alcoholic liver disease. Carbohydrate-deficient transferrin and gamma-glutamyltransferase were measured at admission using commercially available kits.

RESULTS

Carbohydrate-deficient transferrin was more sensitive than gamma-glutamyltransferase in patients without alcoholic liver disease, in both men (85 vs 54%) and women (64 vs 36%). Carbohydrate-deficient transferrin sensitivity decreased slightly but not significantly according to the severity of the liver disease in men and women. The sensitivity of gamma-glutamyltransferase which was low in men and women without alcoholic liver disease, improved in groups with moderate or severe alcoholic liver disease: not less than 80% in men and up to 100% in women. The specificity of carbohydrate-deficient transferrin in patients with non-alcoholic liver disease was consistently higher than that of gamma-glutamyltransferase (80% vs 60%).

CONCLUSIONS

In liver units, carbohydrate-deficient transferrin can help to identify excessive drinkers without liver disease with a higher efficacy than that of gamma-glutamyltransferase; carbohydrate-deficient transferrin can also be used to distinguish between alcoholics with moderate liver disease and patients with non-alcoholic liver diseases.

Carbohydrate-deficient transferrin as a marker of alcohol consumption in male patients with liver disease

Carbohydrate-deficient transferrin (CDT) has been proposed as a marker of alcohol abuse. However, its value in patients with associated liver disease is still controversial. The aim of the study was to investigate the usefulness of CDT as a marker of alcohol consumption in patients with liver disease. We measured serum levels of CDT and those of commonly used hematological and biochemical markers, mean corpuscular volume (MCV), transaminases (AST and ALT), and gamma-glutamyltransferase in 179 male subjects divided into four groups: 45 active drinkers (13 with normal liver, 21 with fibrosteatosis, and 11 with liver cirrhosis), 45 abstinent chronic alcoholics (18 with and 27 without liver disease), 58 patients with nonalcoholic liver disease, and 31 healthy controls. Serum CDT in active alcoholics was 37.5 +/- 3.6 units/liter, being significantly higher than that of abstinent alcoholics (20.3 +/- 1.5 units/liter), patients with nonalcoholic liver disease (18.1 +/- 1.1 units/liter), and controls (13.1 +/- 0.8 units/liter). Contrary to the other markers, no significant differences were observed in CDT values in relation with the presence and severity of liver disease in either the active drinkers or in the abstinent alcoholics. The sensitivity and specificity of CDT as a marker of alcoholism in the series as a whole was 64% and 82%, respectively, similar to the best conventional marker, MCV (64 and 82%). In patients with liver disease, CDT maintained good sensitivity (72%) and specificity (83%). Receiver operating characteristic analysis confirmed that CDT had a similar diagnostic value to that of MCV, but better than gamma-glutamyl-transferase and transaminases for the detection of alcohol abusers. The good diagnostic efficacy of CDT remained unchanged when analyzing only patients with liver disease. We conclude that serum CDT is a good marker of alcoholism and is less influenced than the currently used biochemical markers for associated liver disease. Thus, CDT is an effective laboratory test to detect alcohol abuse regardless of the presence of alcoholic liver disease.

Serum carbohydrate-deficient transferrin in patients with nonalcoholic liver disease and with hepatocellular carcinoma

Serum carbohydrate-deficient transferrin (CDT) is used as a reliable and specific marker of alcohol consumption. However, recent studies have shown false-positive CDT test results in nonalcoholic liver disease. We examined the clinical significance of serum CDT in nonalcoholic liver disease, especially hepatocellular carcinoma. Serum CDT was measured in 23 teetotallers, 56 patients with alcoholic liver disease, 84 patients with viral liver disease and 67 patients with hepatocellular carcinoma, with an Axis %CDT radioimmunoassay kit, and the results were expressed as percentages of the total transferrin (%CDT). The mean serum %CDT value was increased 1.8-fold in alcoholic liver fibrosis and 3.8-fold in alcoholic liver cirrhosis compared with the teetotallers. The serum %CDT values in viral chronic hepatitis were similar to those of the teetotallers, and were increased 2.0-fold in viral liver cirrhosis. False-positive results were found in 10 (37%) of the 27 patients with viral liver cirrhosis. The mean serum %CDT value was increased 2.5-fold in hepatocellular carcinoma, and false-positive results were found in 31 (46%) of the 67 patients. The serum %CDT value was related to the severity of Child grade, the size of tumor and the grade of histological differentiation. These results suggest that the ability of serum CDT test to detect chronic alcoholism may be reduced in patients with nonalcoholic liver cirrhosis and those with hepatocellular carcinoma.

Serum markers for hepatic fibrosis in alcoholic liver disease: which is the best marker, type III procollagen, type IV collagen, laminin, tissue inhibitor of metalloproteinase, or prolyl hydroxylase?

Although various serum markers for the evaluation of hepatic fibrosis have been introduced, it remains unclear which is the best marker to evaluate the hepatic fibrosis observed in alcoholic liver disease (ALD). In this study, we measured serum concentrations of the immunoreactive beta-subunit of prolyl hydroxylase, procollagen type III peptide, the 7S domain (7S-IV) and triple-helix domain (TH-IV) of type IV collagen, laminin, and tissue inhibitor of metalloproteinase (TIMP) in patients with and without ALD (non-ALD), and controls to evaluate the best serum marker reflecting the characteristic histologic features of ALD. After Azan-Mallory and silver-impregnated reticulin staining, histologic specimens were examined; and the degree of hepatic fibrosis was classified as mild, moderate, or severe. Although serum concentrations of all markers, except for TIMP, in patients with each type and stage of liver disease were higher than cut-off values and these concentrations increases with the progression of liver disease, statistical analyses indicate that serum TH-IV concentration is the best marker to distinguish ALD from non-ALD. A good correlation was also found between the hepatic type IV collagen content and serum TH-IV, but not serum 7S-IV concentration. Moreover, after abstinence from alcohol, serum concentrations of TH-IV decreased more quickly than other serum markers. These results clearly suggest that, compared with other markers, serum concentration of TH-IV may more strongly reflect the histologic features of ALD. However, other serum markers, except for TIMP, may be useful in evaluating the degree of hepatic fibrosis.

Sensitivity and specificity of carbohydrate-deficient transferrin as a marker of alcohol abuse are significantly influenced by alterations in serum transferrin: comparison of two methods

Despite a number of investigations suggesting the value of carbohydrate-deficient transferrin (CDT) as a marker of alcohol abuse, a variety of issues on the applicability of CDT measurements in clinical settings have remained unexplored. Earlier studies in this field have focused on the relationship of CDT and the amount of alcohol consumption or presence of liver disease, whereas the influence of alterations in serum transferrin concentrations on CDT has received less attention. In this study, we compared two different methods for measuring CDT (CDTect and %CDT) and total transferrin concentrations in a sample of 83 alcohol abusers (20 patients with alcoholic liver disease and 63 heavy drinkers who were devoid of liver disease, despite excessive alcohol consumption) and 89 controls, who were social drinkers or abstainers. The control population included 53 hospitalized patients with expected abnormalities in serum transferrin concentrations caused by conditions such as negative iron balance, pregnancy, or nonalcoholic liver disease. Both methods gave significantly higher values in alcohol abusers than in controls (p < 0.01), but the overall sensitivity for detecting alcohol abuse was clearly higher for CDTect (59%) than for %CDT (34%). The correlation between the results obtained by the two methods (r = 0.629) significantly improved, when the CDTect values were replaced by the ratio of CDTect/total transferrin (r = 0.770) (p < 0.05). There was a positive correlation between the CDTect and serum transferrin (r = 0.201, p < 0.01), which was significant both in the alcoholics (r = 0.240, p < 0.05), and especially in the controls (r = 0.727, p < 0.001). A significant inverse correlation emerged between %CDT and total transferrin (r = -0.302, p < 0.01). The sensitivities of CDTect and %CDT for correctly classifying alcohol abusers in the subgroup of alcoholic liver disease patients were 90% and 70% and in the subgroup of heavy drinkers without liver disease (49% and 22%), respectively. Specificities for CDTect and %CDT in this sample were 81% and 100%, respectively. However, in the subgroup of hospitalized control patients with abnormal serum transferrin, the specificity of CDTect was only 48%. According to present data, CDTect seems to be more sensitive than %CDT for detecting alcohol abuse. However, any alteration in serum total transferrin concentration markedly decreases the assay specificity. This should be considered when interpreting the assay results in patients with elevated serum transferrin, such as iron deficiency, pregnancy, or liver diseases.

Carbohydrate-deficient transferrin as a marker of alcohol abuse: relationship to alcohol consumption, severity of liver disease, and fibrogenesis

Carbohydrate-deficient transferrin (CDT) measurements have been widely examined as a marker of excessive alcohol consumption, yet the information on the sensitivity of this method has remained controversial. In addition, little is known of the relationship of this marker and the severity of alcoholic liver disease (ALD). To clarify these issues, we analyzed serum samples from 373 alcohol abusers, including 200 problem drinkers with no apparent liver pathology, 173 patients with clinical or morphological evidence of ALD, and 42 healthy controls. CDT was analyzed by anion-exchange chromatography followed by radioimmunoassay. At a specificity of 100%, the sensitivity of CDT was 36% in problem drinkers reporting a mean of 710 +/- 80 (mean +/- 2SE) g of ethanol/week, as compared with the sensitivities of 44% and 35% for gamma-glutamyltranspeptidase (GGT) and mean corpuscular volume (MCV), respectively. In a subgroup of problem drinkers (n = 51) with the highest ethanol intakes (1160 +/- 180 g of ethanol/week) and severe dependence, the sensitivity of CDT increased to 64%, compared with 55% for GGT and 39% for MCV. In ALD, the CDT values were significantly higher than in the alcoholics with nonliver pathology. However, when such patients were classified according to the clinical, laboratory, and morphological severity of liver disease, CDT was found to be primarily elevated in those with the early stage of ALD, such that there was a significant negative correlation between CDT and the combined morphological index of disease severity (rs = -0.315, p < 0.05). ALD markers of fibrogenesis were elevated more frequently than CDT, showing significant positive correlations with the indices of disease severity.(ABSTRACT TRUNCATED AT 250 WORDS)