RESUMO
OBJECTIVE: A decline in the function of all organs can be detected during ageing. Although the trend appears to be stable, deviation within the elderly population is much greater in comparison to young controls. The aim of the study was to identify a marker of senescence which correlates to heart function. Advanced glycation endproducts (AGEs) accumulate with age and are associated with degenerative diseases. METHODS: Carboxymethyllysine (CML) concentrations in the pericardial fluid (as a measure of AGEs) were analysed with ELISA technique in 75 patients undergoing cardiac surgery and correlated with clinical parameters and outcome of these patients. RESULTS: CML content of pericardial fluid increases significantly with age. AGEs show an inverse correlation to left ventricular ejection fraction. High CML levels correlate with poor outcome of patients as shown by adverse cardiac events, prolonged ventilation time and prolonged stay within the Intensive Care Unit. Within all parameters, AGE concentration of the pericardial fluid fits better with the outcome of the patients in comparison to age alone. Interestingly, medical treatment with nitrates correlates with increased CML content. CONCLUSION: AGEs, in addition to being a marker of senescence, appear to represent a prognostic factor in cardiac surgery, which can be used as a predictor of patient outcome.
Assuntos
Envelhecimento/fisiologia , Biomarcadores/análise , Ponte de Artéria Coronária , Produtos Finais de Glicação Avançada/análise , Adulto , Idoso , Idoso de 80 Anos ou mais , Coração/crescimento & desenvolvimento , Coração/fisiologia , Humanos , Lisina/análogos & derivados , Lisina/análise , Pessoa de Meia-Idade , Derrame Pericárdico/fisiopatologia , Valor Preditivo dos Testes , Resultado do TratamentoRESUMO
The four genes required for selenocysteine incorporation were isolated from the gram-positive, amino acid-fermenting anaerobe Eubacterium acidaminophilum, which expresses various selenoproteins of different functions. The sel genes were located in an unique organization on a continuous fragment of genomic DNA in the order selD1 (selenophosphate synthetase 1), selA (selenocysteine synthase), selB (selenocysteine-specific elongation factor), and selC (selenocysteine-specific tRNA). A second gene copy, encoding selenophosphate synthetase 2 (selD2), was present on a separate fragment of genomic DNA. SelD1 and SelD2 were only 62.9% identical, but the two encoding genes, selD1 and selD2, contained an in-frame UGA codon encoding selenocysteine, which corresponds to Cys-17 of Escherichia coli SelD. The function of selA, selB, and selC from E. acidaminophilum was investigated by complementation of the respective E. coli deletion mutant strains and determined as the benzyl viologen-dependent formate dehydrogenase activity in these strains after anaerobic growth in the presence of formate. selA and selC from E. acidaminophilum were functional and complemented the respective mutant strains to 83% (selA) and 57% (selC) compared to a wild-type strain harboring the same plasmid. Complementation of the E. coli selB mutant was only observed when both selB and selC from E. acidaminophilum were present. Under these conditions, the specific activity of formate dehydrogenase was 55% of that of the wild type. Transformation of this selB mutant with selB alone was not sufficient to restore formate dehydrogenase activity.
Assuntos
Proteínas de Drosophila , Eubacterium/metabolismo , Genes Bacterianos , Selenocisteína/metabolismo , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Sequência de Bases , Clonagem Molecular , Escherichia coli/enzimologia , Escherichia coli/genética , Eubacterium/genética , Eubacterium/crescimento & desenvolvimento , Formiato Desidrogenases/genética , Formiato Desidrogenases/metabolismo , Teste de Complementação Genética , Dados de Sequência Molecular , Família Multigênica , Conformação de Ácido Nucleico , Fosfotransferases/química , Fosfotransferases/genética , Fosfotransferases/metabolismo , RNA Mensageiro/química , RNA Mensageiro/genética , Aminoacil-RNA de Transferência/química , Aminoacil-RNA de Transferência/genética , Selenocisteína/genética , Transcrição Gênica , Transferases/genética , Transferases/metabolismoRESUMO
Electron transfer reactions for the reduction of glycine in Eubacterium acidaminophilum involve many selenocysteine (U)- and thiol-containing proteins, as shown by biochemical and molecular analysis. These include an unusual thioredoxin system (-CXXC-), protein A (-CXXU-) and the substrate-specific protein B of glycine reductase (-UXXCXXC-). Most probably a selenoether is formed at protein B by splitting the C-N-bond after binding of the substrate. The carboxymethyl group is then transferred to the selenocysteine of protein A containing a conserved motif. The latter protein acts as a carbon and electron donor by giving rise to a protein C-bound acetyl-thioester and a mixed selenide-sulfide bond at protein A that will be reduced by the thioredoxin system. The dithiothreitol-dependent D-proline reductase of Clostridium sticklandii exhibits many similarities to protein B of glycine reductase including the motif containing selenocysteine. In both cases proprotein processing at a cysteine residue gives rise to a blocked N-terminus, most probably a pyruvoyl group. Formate dehydrogenase and some other proteins from E. acidaminophilum contain selenocysteine, e.g., a 22 kDa protein showing an extensive homology to peroxiredoxins involved in the detoxification of peroxides.
