Increased turnover of Gc-globulin in patients with hepatic encephalopathy

Decreased vitamin D-binding protein level portends poor outcome in acute-on-chronic liver failure caused by hepatitis B virus

BACKGROUND/AIMS

Acute-on-chronic liver failure (ACLF) is a catastrophic illness. Few studies investigated the prognostic value of vitamin D-binding protein (VDBP) for hepatitis B virus (HBV)-related ACLF (HBV-ACLF) resulted in conflicting results.

METHODS

Two prospective HBV-ACLF cohorts (n=287 and n=119) were enrolled to assess and validate the prognostic performance of VDBP.

RESULTS

VDBP levels in the non-survivors were significantly lower than in the survivors (P<0.001). Multivariate Cox regression demonstrated that VDBP was an independent prognostic factor for HBV-ACLF. The VDBP level at admission gradually decreased as the number of failed organs increased (P<0.001), and it was closely related to coagulation failure. The areas under the receiver operating characteristic curve (AUCs) of the Child-Pugh-VDBP and chronic liver failuresequential organ failure assessment (CLIF-SOFA)-VDBP scores were significantly higher than those of Child-Pugh (P<0.001) and CLIF-SOFA (P=0.0013). The AUCs of model for end-stage liver disease (MELD)-VDBP were significantly higher than those of MELD (P= 0.0384) only in the case of cirrhotic HBV-ACLF patients. Similar results were validated using an external multicenter HBV-ACLF cohort. By longitudinal observation, the VDBP levels gradually increased in survivors (P=0.026) and gradually decreased in non-survivors (P<0.001). Additionally, the VDBP levels were found to be significantly decreased in the deterioration group (P=0.012) and tended to be decreased in the fluctuation group (P=0.055). In contrast, they showed a significant increase in the improvement group (P=0.036).

CONCLUSION

The VDBP was a promising prognostic biomarker for HBV-ACLF. Sequential measurement of circulating VDBP shows value for the monitoring of ACLF progression.

Serum vitamin D and vitamin-D-binding protein levels in children with chronic hepatitis B

BACKGROUND

Vitamin D is an essential fat-soluble secosteroid hydroxylated by the liver to form the intermediate metabolite calcidiol {25-hydroxy vitamin D [25(OH)D]}, which is a reliable indicator to investigate individual vitamin D status. Vitamin-D-binding protein (VDBP) is a multifunctional glycoprotein mainly synthesized in the liver and the major transport protein for vitamin D and its metabolites. Serum vitamin D and VDBP are both associated with hepatitis B. However, few studies have reported the relationship and clinical significance of vitamin D and VDBP with hepatitis B virus (HBV) replication and hepatic fibrosis in children with chronic hepatitis B (CHB).

AIM

To explore vitamin D and VDBP serum levels in children with CHB and the association of vitamin D and VDBP with HBV replication and hepatic fibrosis.

METHODS

We enrolled 204 children with CHB admitted to Hunan Children’ Hospital in summer and autumn between 2018 and 2019 and 170 healthy controls. CHB patients included: 164 hepatitis B e antigen (HBeAg) positive and 40 HBeAg negative; 193 hepatitis B surface antigen (HBsAg) positive and 11 HBsAg negative; 164 with detectable HBV deoxyribonucleic acid (DNA) and 40 with undetectable HBV DNA; 131 with HBV genotype B and 23 with HBV genotype C; and 27 without hepatic fibrosis and 97 with hepatic fibrosis. Serum levels of 25(OH)D, VDBP, liver function markers, and other clinical parameters were collected to analyze their association with vitamin D and VDBP. Mann-Whitney U test, Kruskal-Wallis H test, or t test was used to analyze serum 25(OH)D and VDBP levels in different groups. Spearman rank correlation test was utilized to analyze the correlation of 25(OH)D and VDBP with other markers. Statistically significant factors determined by univariate analysis were further analyzed by binary multivariate logistic regression analysis. P < 0.05 was considered statistically significant.

RESULTS

Children with CHB had lower serum 25(OH)D (56.64 ± 17.89 nmoL/L) and VDBP [122.40 (70.74-262.84 μg/L)] levels than healthy controls had (P < 0.001). Serum 25(OH)D and VDBP levels were significantly different among the different grades of hepatic fibrosis (P < 0.05). VDBP levels in children with HBV genotype C, HBsAg, HBeAg, and detectable HBV DNA were significantly lower than those in children with HBV genotype B, no HBsAg, no HBeAg, and undetectable HBV DNA (P < 0.05). Serum 25(OH)D level was negatively correlated with age and serum total bilirubin level (r = -0.396 and -0.280, respectively, P < 0.001). Serum VDBP level was negatively correlated with HBV DNA (log₁₀ IU/mL) (r = -0.272, P < 0.001). Serum 25(OH)D level was not correlated with VDBP level (P > 0.05). Univariate (P < 0.05) and multivariate logistic regression analysis showed that low level of 25(OH)D (odds ratio = 0.951, 95% confidence interval: 0.918-0.985) and high level of HBV DNA (odds ratio = 1.445, 95% confidence interval: 1.163-1.794) were independently correlated with hepatic fibrosis (P < 0.01).

CONCLUSION

Serum levels of 25(OH)D and VDBP are decreased in children with CHB. Serum VDBP level is negatively correlated with HBV replication. Low level of 25(OH)D is independently associated with hepatic fibrosis in children with CHB. There is no significant association between serum levels of 25(OH)D and VDBP.

Vitamin D-binding protein as a biomarker of active disease in acute intermittent porphyria

Acute intermittent porphyria (AIP) is an autosomal dominant metabolic disorder caused by a deficiency of hepatic porphobilinogen deaminase (PBGD). The disease is characterized by life threatening acute neurovisceral attacks. The aim of this study was to identify metabolites secreted by the hepatocytes that reflect differential metabolic status in the liver and that may predict response to the acute attack treatment. Plasma vitamin D binding protein (VDBP) from a mouse model of AIP displayed an abnormal migration in 2D-electrophoresis that is efficiently recovered upon gene therapy leading to liver specific over-expression of the PBGD protein. The change in VDBP mobility results from a differential isoelectric point suggesting a post-translational modification that takes place preferably in the liver. Liquid chromatography-mass spectrometry (LC-MS) analysis of human samples before and after glycosidase treatment revealed glycosylated plasma VDBP specifically in patients with recurrent attacks of AIP. Glycosylated VDBP recovered normal values in three severely afflicted AIP patients submitted to therapeutic liver transplantation. Our findings suggest that post-translational modification of VDBP might be considered as a promising biomarker to study and monitor the liver metabolic status in patients with AIP.

SIGNIFICANCE

We describe an increased glycosylation of VDBP in porphyric livers. Normal glycosylation was recovered upon liver gene therapy in a mouse model of porphyria or after liver transplantation in severely afflicted patients with AIP. Moreover, quantification of glycosylated VDBP by our ELISA immunoassay or LC-MS protocol in patients undergoing PBGD-gene therapy (www.aipgene.org) may be used as a marker indicating improvement or normalization of the patient's hepatic metabolism. This article is part of a Special Issue entitled: HUPO 2014.

Plasma Actin-free Gc-globulin in Patients with Chronic or Acute-on-chronic Liver Failure Caused by Hepatitis B Virus

Background

Previous studies have confirmed that serum concentrations of actin-free Gc globulin (Af-Gc globulin) may provide prognostic information in patients withacute liver failure (ALF). However, until now the relation between plasma Af-Gc globulin levels and chronic or acute-on-chronic liver failure (CLF or ACLF) caused by HBV is unknown.

Methods

Plasma Af-Gc globulin in 56 patients with liver failure, in 23 patients with compensated liver cirrhosis (CR), and in 25 healthy controls were measured using enzyme-linked immunosorbent assay (ELISA). Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), choline esterase (CHE), Albumin (ALB), total bilirubin (TBIL), palsma international normalized ratio of prothrombin time (INR), and platelet (PLT) were also detected. The Child-Pugh score was calculated for each patient on admission.

Results

Plasma Af-Gc globulin levels in CLF, ACLF and CR were significantly lower than that of healthy controls (P < 0.001, respectively). The median (range) Af-Gc globulin level at admission for the liver failure (CLF or ACLF) was significantly reduced compared with that of CR group (P ≤ 0.001); additionally, there was significant difference between CLF and ACLF patients (P < 0.001). In liver failure cohort, plasma Af-Gc globulin was significantly positive correlated with ALB, ALT, AST and CHE (P was 0.001, 0.001, 0.001, < 0.001, respectively). Meanwhile, there was significantly negative correlation between plasma Af-Gc globulin and Child-Pugh score (P = 0.02). The level of Af-Gc globulin in ascites or hydrothorax-infected liver failure patients were markedly lower than that of non-infected (P = 0.015), the levels of Af-Gc in encephalopathy presence were lower than in encephalopathy absence. No significant difference of Af-Gc was noted between non-survivors and survivors during the follow-up period in liver failure patients.

Conclusions

Plasma Af-Gc globulin levels in liver failure patients are significantly reduced compared with compensated liver cirrhosis patients and healthy controls, however, it might not be used in the prognosis of liver failure.

Predictive value of actin-free Gc-globulin in acute liver failure

Serum concentrations of the actin scavenger Gc-globulin may provide prognostic information in acute liver failure (ALF). The fraction of Gc-globulin not bound to actin is postulated to represent a better marker than total Gc-globulin but has been difficult to measure. We tested a new rapid assay for actin-free Gc-globulin to determine its prognostic value when compared with the King's College Hospital (KCH) criteria in a large number of patients with ALF. A total of 252 patients with varying etiologies from the U.S. ALF Study Group registry were included; the first 178 patients constituted the learning set, and the last 74 patients served as the validation set. Actin-free Gc-globulin was determined with a commercial enzyme-linked immunosorbent assay kit. The median (range) actin-free Gc-globulin level at admission for the learning set was significantly reduced compared with controls (47 [0-183] mg/L vs. 204 [101-365] mg/L, respectively, P < 0.001). Gc-globulin levels were significantly higher in spontaneous survivors than in patients who died or were transplanted (53 [0-129] mg/L vs. 37 [0-183] mg/L, P = 0.002). A receiver operating characteristic curve analysis showed that a 40 mg/L cutoff level carried the best prognostic information, yielding positive and negative predictive values of 68% and 67%, respectively, in the validation set. The corresponding figures for the KCH criteria were 72% and 64%. A new enzyme-linked immunosorbent assay for actin-free Gc-globulin provides the same (but not optimal) prognostic information as KCH criteria in a single measurement at admission.

Gc-globulin and prognosis in acute liver failure

Serum concentrations of the actin scavenger Gc-globulin are reduced in acute liver failure (ALF). Prospectively, we tested Gc-globulin's value to predict outcome following ALF using sera from 182 patients with ALF from the U.S. ALF Study Group. Admission serum levels of Gc-globulin (normal range: 350-500 mg/L) were studied by an immunonephelometric method. The median (range) serum Gc-globulin level on admission for the entire group was 91 (5-307) mg/L. Gc-globulin levels were significantly higher in spontaneous survivors than in patients who died or underwent transplantation (113 [5-301] mg/L vs. 73 [5-307] mg/L, P < 0.001). Those surviving non-acetaminophen (paracetamol)-induced ALF without transplantation had higher Gc-globulin levels than nonsurvivors (102 [5-301] mg/L vs. 61 [5-232] mg/L, P = 0.002), whereas there was no significant difference in levels between the groups in patients with acetaminophen-induced ALF. A cutoff level of 80 mg/L in the non-acetaminophen group yielded positive and negative predictive values of 85% and 43%, respectively. The corresponding figures for the King's College criteria were 90% and 49%, respectively. In conclusion, we found that Gc-globulin levels were markedly decreased in patients with ALF; the lowest levels were observed in patients who died or were transplanted. In contrast to previous studies, this study demonstrated that Gc-globulin has prognostic value in patients with non-acetaminophen-induced ALF, in the same range as the King's College criteria. Further refinements of the assay would be necessary to make it more accurate and of practical utility.

Therapeutic potential of vitamin D-binding protein

Vitamin D-binding protein (DBP) is a multi-functional plasma protein with many important functions. These include transport of vitamin D metabolites, control of bone development, binding of fatty acids, sequestration of actin and a range of less-defined roles in modulating immune and inflammatory responses. Exploitation of the unique properties of DBP could enable the development of important therapeutic agents for the treatment of a variety of diseases.