Risk of recurrent hepatic encephalopathy in patients with liver cirrhosis: a German registry study.

BACKGROUND AND AIMS: Patients with hepatic encephalopathy (HE) show low quality of life, recurrent hospitalizations and an increased mortality. We aimed to assess the natural course of patients after a recent episode of overt HE and to identify risk factors for HE recurrence in Germany. METHODS: Fifteen sites took part in a prospective, observational study including patients with liver cirrhosis who had been hospitalized for HE within 3 months before recruitment. Clinical data, psychometric hepatic encephalopathy score (PHES) and critical flicker frequency were assessed quarterly for 1 year. Primary endpoint was HE recurrence requiring hospitalization, all-cause-mortality was treated as a competing risk factor. RESULTS: From January 2014 to March 2016, a total of 115 patients were recruited. Overall 14 premature deaths were documented. For 78 subjects follow-up data were available in accordance with the protocol. After a median of 118 days, more than half of the per-protocol cohort was readmitted to hospital due to HE (N = 34) or died (N = 11). The risk for hospitalization was significantly increased in patients who had been recruited by liver transplant centers (P = 0.003), had had frequent HE relapses prior to recruitment (P = <0.0001) or an abnormal PHES result of <-4 (P = 0.044). Abnormal PHES results barely missed level of significance as an independent risk factor for re-hospitalization in a multivariable competing risk model (P = 0.093). CONCLUSION: Patients with a history of HE are at high risk for the development of recurrent overt HE demanding hospitalization. The PHES test may aid in detection, monitoring and risk stratification of recurrent HE.

Hangzhou criteria are more accurate than Milan criteria in predicting long-term survival after liver transplantation for HCC in Germany.

BACKGROUND: Milan criteria are used for patient selection in liver transplantation for hepatocellular carcinoma (HCC). Hangzhou criteria have been shown in China to enable access to liver transplantation for more patients when compared to Milan criteria without negative effects on long-term survival. The purpose of this study was to evaluate the Hangzhou criteria in a German cohort. METHODS: One hundred fifty-nine patients transplanted for HCC between 1975 and 2010 were investigated. Patients were categorized into four groups depending on the fulfillment of Milan and Hangzhou criteria. General and tumor baseline characteristics were compared. Overall and tumor-free survival rates were investigated with the Kaplan-Meier analysis. RESULTS: One-, 3-, 5-, and 10-year survival rates for patients fulfilling Milan criteria (n = 68) were 89.7, 83.7, 75.8, and 62.1%, respectively, versus 89.8, 82.2, 75.2, and 62.6% for patients fulfilling Hangzhou criteria (n = 109) (p = 0.833). When comparing patients exceeding Milan or Hangzhou criteria, survival rates were 75.3, 53.2, 48.1, and 41.1% versus 63.3, 31.4, 26.9, and 22.1%, respectively (p = 0.019). The comparison of tumor-free survival rates in patients fulfilling Milan or Hangzhou criteria was statistically not significant (p = 0.785), whereas the comparison of the groups exceeding the criteria showed significantly worse survival for patients outside Hangzhou criteria (p = 0.007). The proportion of patients fulfilling Hangzhou criteria (68.6%) was significantly larger as compared to the proportion fulfilling Milan criteria (42.8%) (p < 0.001). CONCLUSION: Hangzhou criteria are more accurate in predicting long-term survival after liver transplantation for HCC in Germany. Deployment of the Hangzhou criteria for patient selection could enlarge the pool of transplantable patients.

Introduction of the resection severity index as independent risk factor limiting survival after resection of colorectal liver metastases.

BACKGROUND: The purpose of this study is to evaluate the influence of the recently introduced resection severity index (RSI) in patients with liver resection for hepatocellular carcinoma on survival after resection of colorectal liver metastases. The RSI quantifies pre-operatively the liver cellular damage, liver synthetic function and loss of organ parenchyma. METHODS: All consecutive patients who underwent liver resection for metastases of colorectal cancer (CLM) between 2000 and 2015 were included in this study. Risk factors limiting survival were analyzed using univariable and multivariable Cox regression analyses. RESULTS: The median survival after liver resection for CLM was 3.0 years. Significant independent risk factors for mortality were the RSI (p = 0.029; hazard ratio (HR): 1.088, 95%-confidence interval (95%-CI): 1.009-1.174), age at resection in years (p = 0.001; HR: 1.017, 95%-CI: 1.007-1.027), pre-operative hemoglobin level (p = 0.041; HR: 0.932, 95%-CI: 0.891-0.997), the cecum as location of primary CRC (p < 0.001; HR: 2.023, 95%-CI: 1.403-2.833), adjuvant chemotherapy (p < 0.001; HR: 1.506, 95%-CI: 1.212-1.878), local relapse of the primary tumor (p = 0.027; HR: 1.591, 95%-CI: 1.057-2.297), the units of intra-operatively transfused packed red blood cells (p < 0.001; HR: 1.068, 95%-CI: 1.033-1.104), the size of the largest metastasis (p = 0.002; HR: 1.005, 95%-CI: 1.002-1.008) and the metastasis' distance to the resection margin (p = 0.014; HR: 0.984, 95%-CI: 0.972-0.997). CONCLUSION: The RSI is an independent prognostic factor for survival after liver resection for CLM. Besides the extent of liver resection certain primary tumor characteristics have to be taken into account to ensure long-term survival.

No evidence of substantial growth progression or complications of large focal nodular hyperplasia during pregnancy.

OBJECTIVE: Focal nodular hyperplasia (FNH) is a benign liver tumor considered to develop under the influence of estrogens. Whether women with known FNH are at higher risk of growth progression and complications during pregnancy is still controversially discussed. The authors investigated the growth pattern of FNH during pregnancy and possible related complications. MATERIALS AND METHODS: Twenty pregnant women with FNH were followed by the authors' center. Before pregnancy, diagnosis of FNH was usually established by contrast-enhanced ultrasound. During pregnancy, monitoring of FNH was performed by conventional ultrasound. Furthermore, a questionnaire was sent to all patients. RESULTS: Patient's age ranged from 24 to 36 years. Mean size of FNH before pregnancy was 58.5 ± 22.7 mm. It did not vary significantly during pregnancy (fourth month of pregnancy: 58.1 ± 23.0 mm; after pregnancy: 55.5 ± 26.8 mm; -8%; n.s.). Only in three patients, growth of FNH by 18 ± 6% was observed, while FNH size remained constant in 7 patients and even declined by -11 ± 6% in 10 patients. There were no FNH-related complications. The questionnaire was sent back by 16 patients (80%). All responding patients took oral contraceptives in the past over a mean 12.4 ± 4.4 years. Previous pregnancies were reported by 38% of patients. FNH-related fears were expressed by 63% of patients, but no FNH-related complications or symptoms during pregnancy were noted. CONCLUSIONS: This study demonstrates that women with FNH are not at risk of significant growth progression or FNH-related complications. Pregnancy should not be discouraged in these patients but careful advice and guidance are necessary.

Identification of CD4 T-cell epitopes in soluble liver antigen/liver pancreas autoantigen in autoimmune hepatitis.

BACKGROUND & AIMS: Autoimmune hepatitis (AIH) is a chronic inflammatory liver disease associated with autoantibodies and liver-infiltrating lymphocytes. Although autoantibodies are tested routinely to diagnose and classify AIH, liver-infiltrating lymphocytes are regarded as the primary factor for disease pathogenesis. The purpose of this study was to identify and characterize autoantigenic peptides within human AIH-specific soluble liver antigen/liver pancreas antigen (SLA/LP) that are targeted by CD4(+) T cells and restricted by the disease susceptibility gene HLA-DRB1*0301. METHODS: HLA-DRB1*0301 transgenic mice were immunized with SLA/LP. Antibody and T-cell responses were analyzed with SLA/LP-overlapping peptides in enzyme immunoassay, proliferation, and enzyme-linked immunospot (ELISpot) assays. Minimal optimal T-cell epitopes were identified, characterized with cloned T-cell hybridomas, and confirmed in tetramer and ELISpot assays with AIH patients' peripheral blood mononuclear cells. RESULTS: All mice developed SLA/LP-specific IgG1/IgG2a antibodies against the same SLA/LP peptides as human beings. T cells targeted several peptides within SLA/LP, 2 of which were DR3-restricted and one overlapped the sequence recognized by human autoantibodies. Minimal optimal epitopes were mapped, DRB1*0301/epitope-tetramers were generated, and the frequency and function of HLA-DRB1*0301-restricted autoantigen-specific T cells in AIH patients were analyzed with tetramer and interferon-gamma ELISpot assays. CONCLUSIONS: This study identified T-cell epitopes within SLA/LP, restricted by the disease susceptibility gene DRB1*0301 and in close proximity to the human autoantibody epitope. These results and the generated reagents now provide the opportunity to directly monitor autoreactive T cells in AIH patients in clinical studies.

Structure and catalytic mechanism of eukaryotic selenocysteine synthase.

In eukaryotes and Archaea, selenocysteine synthase (SecS) converts O-phospho-L-seryl-tRNA [Ser]Sec into selenocysteyl-tRNA [Ser]Sec using selenophosphate as the selenium donor compound. The molecular mechanisms underlying SecS activity are presently unknown. We have delineated a 450-residue core of mouse SecS, which retained full selenocysteyl-tRNA [Ser]Sec synthesis activity, and determined its crystal structure at 1.65 A resolution. SecS exhibits three domains that place it in the fold type I family of pyridoxal phosphate (PLP)-dependent enzymes. Two SecS monomers interact intimately and together build up two identical active sites around PLP in a Schiff-base linkage with lysine 284. Two SecS dimers further associate to form a homotetramer. The N terminus, which mediates tetramer formation, and a large insertion that remodels the active site set SecS aside from other members of the family. The active site insertion contributes to PLP binding and positions a glutamate next to the PLP, where it could repel substrates with a free alpha-carboxyl group, suggesting why SecS does not act on free O-phospho-l-serine. Upon soaking crystals in phosphate buffer, a previously disordered loop within the active site insertion contracted to form a phosphate binding site. Residues that are strictly conserved in SecS orthologs but variant in related enzymes coordinate the phosphate and upon mutation corrupt SecS activity. Modeling suggested that the phosphate loop accommodates the gamma-phosphate moiety of O-phospho-l-seryl-tRNA [Ser]Sec and, after phosphate elimination, binds selenophosphate to initiate attack on the proposed aminoacrylyl-tRNA [Ser]Sec intermediate. Based on these results and on the activity profiles of mechanism-based inhibitors, we offer a detailed reaction mechanism for the enzyme.

New developments in selenium biochemistry: selenocysteine biosynthesis in eukaryotes and archaea.

We used comparative genomics and experimental analyses to show that (1) eukaryotes and archaea, which possess the selenocysteine (Sec) protein insertion machinery contain an enzyme, O-phosphoseryl-transfer RNA (tRNA) [Ser]Sec kinase (designated PSTK), which phosphorylates seryl-tRNA [Ser]Sec to form O-phosphoseryl-tRNA [Ser]Sec and (2) the Sec synthase (SecS) in mammals is a pyridoxal phosphate-containing protein previously described as the soluble liver antigen (SLA). SecS uses the product of PSTK, O-phosphoseryl-tRNA[Ser]Sec, and selenophosphate as substrates to generate selenocysteyl-tRNA [Ser]Sec. Sec could be synthesized on tRNA [Ser]Sec from selenide, adenosine triphosphate (ATP), and serine using tRNA[Ser]Sec, seryl-tRNA synthetase, PSTK, selenophosphate synthetase, and SecS. The enzyme that synthesizes monoselenophosphate is a previously identified selenoprotein, selenophosphate synthetase 2 (SPS2), whereas the previously identified mammalian selenophosphate synthetase 1 did not serve this function. Monoselenophosphate also served directly in the reaction replacing ATP, selenide, and SPS2, demonstrating that this compound was the active selenium donor. Conservation of the overall pathway of Sec biosynthesis suggests that this pathway is also active in other eukaryotes and archaea that contain selenoproteins.

Selenophosphate synthetase 2 is essential for selenoprotein biosynthesis.

Selenophosphate synthetase (SelD) generates the selenium donor for selenocysteine biosynthesis in eubacteria. One homologue of SelD in eukaryotes is SPS1 (selenophosphate synthetase 1) and a second one, SPS2, was identified as a selenoprotein in mammals. Earlier in vitro studies showed SPS2, but not SPS1, synthesized selenophosphate from selenide, whereas SPS1 may utilize a different substrate. The roles of these enzymes in selenoprotein synthesis in vivo remain unknown. To address their function in vivo, we knocked down SPS2 in NIH3T3 cells using small interfering RNA and found that selenoprotein biosynthesis was severely impaired, whereas knockdown of SPS1 had no effect. Transfection of SPS2 into SPS2 knockdown cells restored selenoprotein biosynthesis, but SPS1 did not, indicating that SPS1 cannot complement SPS2 function. These in vivo studies indicate that SPS2 is essential for generating the selenium donor for selenocysteine biosynthesis in mammals, whereas SPS1 probably has a more specialized, non-essential role in selenoprotein metabolism.

Biosynthesis of selenocysteine on its tRNA in eukaryotes.

Selenocysteine (Sec) is cotranslationally inserted into protein in response to UGA codons and is the 21st amino acid in the genetic code. However, the means by which Sec is synthesized in eukaryotes is not known. Herein, comparative genomics and experimental analyses revealed that the mammalian Sec synthase (SecS) is the previously identified pyridoxal phosphate-containing protein known as the soluble liver antigen. SecS required selenophosphate and O-phosphoseryl-tRNA([Ser]Sec) as substrates to generate selenocysteyl-tRNA([Ser]Sec). Moreover, it was found that Sec was synthesized on the tRNA scaffold from selenide, ATP, and serine using tRNA([Ser]Sec), seryl-tRNA synthetase, O-phosphoseryl-tRNA([Ser]Sec) kinase, selenophosphate synthetase, and SecS. By identifying the pathway of Sec biosynthesis in mammals, this study not only functionally characterized SecS but also assigned the function of the O-phosphoseryl-tRNA([Ser]Sec) kinase. In addition, we found that selenophosphate synthetase 2 could synthesize monoselenophosphate in vitro but selenophosphate synthetase 1 could not. Conservation of the overall pathway of Sec biosynthesis suggests that this pathway is also active in other eukaryotes and archaea that synthesize selenoproteins.

SECIS elements in the coding regions of selenoprotein transcripts are functional in higher eukaryotes.

Expression of selenocysteine (Sec)-containing proteins requires the presence of a cis-acting mRNA structure, called selenocysteine insertion sequence (SECIS) element. In bacteria, this structure is located in the coding region immediately downstream of the Sec-encoding UGA codon, whereas in eukaryotes a completely different SECIS element has evolved in the 3'-untranslated region. Here, we report that SECIS elements in the coding regions of selenoprotein mRNAs support Sec insertion in higher eukaryotes. Comprehensive computational analysis of all available viral genomes revealed a SECIS element within the ORF of a naturally occurring selenoprotein homolog of glutathione peroxidase 4 in fowlpox virus. The fowlpox SECIS element supported Sec insertion when expressed in mammalian cells as part of the coding region of viral or mammalian selenoproteins. In addition, readthrough at UGA was observed when the viral SECIS element was located upstream of the Sec codon. We also demonstrate successful de novo design of a functional SECIS element in the coding region of a mammalian selenoprotein. Our data provide evidence that the location of the SECIS element in the untranslated region is not a functional necessity but rather is an evolutionary adaptation to enable a more efficient synthesis of selenoproteins.

Evidence for direct roles of two additional factors, SECp43 and soluble liver antigen, in the selenoprotein synthesis machinery.

Selenocysteine (Sec) is inserted into selenoproteins co-translationally with the help of various cis- and trans-acting factors. The specific mechanisms of Sec biosynthesis and insertion into protein in eukaryotic cells, however, are not known. Two proteins, SECp43 and the soluble liver antigen (SLA), were previously reported to interact with tRNA([Ser]Sec), but their functions remained elusive. Herein, we report that knockdown of SECp43 in NIH3T3 or TCMK-1 cells using RNA interference technology resulted in a reduction in the level of methylation at the 2'-hydroxylribosyl moiety in the wobble position (Um34) of Sec tRNA([Ser]Sec), and consequently reduced glutathione peroxidase 1 expression. Double knockdown of SECp43 and SLA resulted in decreased selenoprotein expression. SECp43 formed a complex with Sec tRNA([Ser]Sec) and SLA, and the targeted removal of one of these proteins affected the binding of the other to Sec tRNA([Ser]Sec). SECp43 was located primarily in the nucleus, whereas SLA was found in the cytoplasm. Co-transfection of both proteins resulted in the nuclear translocation of SLA suggesting that SECp43 may also promote shuttling of SLA and Sec tRNA([Ser]Sec) between different cellular compartments. Taken together, these data establish the role of SECp43 and SLA in selenoprotein biosynthesis through interaction with tRNA([Ser]Sec) in a multiprotein complex. The data also reveal a role of SECp43 in regulation of selenoprotein expression by affecting the synthesis of Um34 on tRNA([Ser]Sec) and the intracellular location of SLA.