RESUMO
Down syndrome (DS) is the most common chromosomal disorder, resulting from the failure of normal chromosome 21 segregation. Studies have suggested that impairments within the one-carbon metabolic pathway can be of relevance for the global genome instability observed in mothers of individuals with DS. Based on the association between global DNA hypomethylation, genome instability, and impairments within the one-carbon metabolic pathway, the present study aimed to identify possible predictors, within the one-carbon metabolism, of global DNA methylation, measured by methylation patterns of LINE-1 and Alu repetitive sequences, in mothers of individuals with DS and mothers of individuals without the syndrome. In addition, we investigated one-carbon genetic polymorphisms and metabolites as maternal predisposing factors for the occurrence of trisomy 21 in children. Eighty-three samples of mothers of children with DS with karyotypically confirmed free trisomy 21 (case group) and 84 of mothers who had at least one child without DS or any other aneuploidy were included in the study. Pyrosequencing assays were performed to access global methylation. The results showed that group affiliation (case or control), betaine-homocysteine methyltransferase (BHMT) G742A and transcobalamin 2 (TCN2) C776G polymorphisms, and folate concentration were identified as predictors of global Alu DNA methylation values. In addition, thymidylate synthase (TYMS) 28-bp repeats 2R/3R or 3R/3R genotypes are independent maternal predisposing factors for having a child with DS. This study adds evidence that supports the association of impairments in the one-carbon metabolism, global DNA methylation, and the possibility of having a child with DS.
Assuntos
Carbono/metabolismo , Metilação de DNA/genética , Síndrome de Down/genética , Síndrome de Down/metabolismo , Estudo de Associação Genômica Ampla , Instabilidade Genômica/genética , Relações Mãe-Filho , Mães , Adolescente , Adulto , Idoso , Elementos Alu/genética , Betaína-Homocisteína S-Metiltransferase/genética , Betaína-Homocisteína S-Metiltransferase/metabolismo , Feminino , Ácido Fólico/metabolismo , Predisposição Genética para Doença/genética , Humanos , Elementos Nucleotídeos Longos e Dispersos/genética , Masculino , Pessoa de Meia-Idade , Polimorfismo Genético , Transdução de Sinais/genética , Transdução de Sinais/fisiologia , Timidilato Sintase/genética , Transcobalaminas/genética , Transcobalaminas/metabolismo , Adulto JovemRESUMO
The aim of the present study was to evaluate the effects of heat stress (HS) and methionine supplementation on the markers of stress and on the gene expression levels of uncoupling proteins (UCP), betaine-homocysteine methyltransferase (BHMT), cystathionine ß-synthase (CBS), glutathione synthetase (GSS) and glutathione peroxidase 7 (GPx7). Broilers from 1 to 21 d and from 22 to 42 d of age were divided into three treatment groups related to methionine supplementation: without methionine supplementation (MD); recommended level of methionine supplementation (DL1); excess methionine supplementation (DL2). The broilers were either kept at a comfortable thermal temperature or exposed to HS (38°C for 24 h). During the starter period, we observed the effects of the interaction between diet and environment on the gene expression levels of UCP, BHMT and GSS. Higher gene expression levels of UCP and BHMT were observed in broilers that were maintained at thermal comfort conditions and received the MD diet. HS broilers fed the DL1 and DL2 diets had the highest expression level of GSS. The expression levels of the CBS and GPx7 genes were influenced by both the environment and methionine supplementation. During the grower period, the gene expression levels of BHMT, CBS, GSS and GPx7 were affected by the diet × environment interaction. A higher expression level of BHMT was observed in broilers maintained at thermal comfort conditions and on the MD diet. HS induced higher expression levels of CBS, GSS and GPx7 in broilers that received the DL1 and DL2 diets. The present results suggest that under HS conditions, methionine supplementation could mitigate the effects of stress, since methionine contributed to the increased expression levels of genes related to antioxidant activity.
Assuntos
Doenças das Aves/prevenção & controle , Dieta/veterinária , Regulação da Expressão Gênica no Desenvolvimento , Transtornos de Estresse por Calor/veterinária , Metionina/uso terapêutico , Estresse Oxidativo , Músculos Peitorais/enzimologia , Animais , Animais Endogâmicos , Antioxidantes/administração & dosagem , Antioxidantes/uso terapêutico , Proteínas Aviárias/genética , Proteínas Aviárias/metabolismo , Betaína-Homocisteína S-Metiltransferase/genética , Betaína-Homocisteína S-Metiltransferase/metabolismo , Biomarcadores/sangue , Biomarcadores/metabolismo , Doenças das Aves/dietoterapia , Doenças das Aves/metabolismo , Doenças das Aves/patologia , Galinhas , Ingestão de Energia , Glutationa Peroxidase/genética , Glutationa Peroxidase/metabolismo , Glutationa Sintase/genética , Glutationa Sintase/metabolismo , Transtornos de Estresse por Calor/dietoterapia , Transtornos de Estresse por Calor/metabolismo , Transtornos de Estresse por Calor/prevenção & controle , Homocisteína/sangue , Canais Iônicos/genética , Canais Iônicos/metabolismo , Isoenzimas/genética , Isoenzimas/metabolismo , Masculino , Metionina/administração & dosagem , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismo , Músculos Peitorais/metabolismo , Músculos Peitorais/patologia , Proteína Desacopladora 1 , Aumento de PesoRESUMO
Essential amino acids (EAA) consist of a group of nine amino acids that animals are unable to synthesize via de novo pathways. Recently, it has been found that most metazoans lack the same set of enzymes responsible for the de novo EAA biosynthesis. Here we investigate the sequence conservation and evolution of all the metazoan remaining genes for EAA pathways. Initially, the set of all 49 enzymes responsible for the EAA de novo biosynthesis in yeast was retrieved. These enzymes were used as BLAST queries to search for similar sequences in a database containing 10 complete metazoan genomes. Eight enzymes typically attributed to EAA pathways were found to be ubiquitous in metazoan genomes, suggesting a conserved functional role. In this study, we address the question of how these genes evolved after losing their pathway partners. To do this, we compared metazoan genes with their fungal and plant orthologs. Using phylogenetic analysis with maximum likelihood, we found that acetolactate synthase (ALS) and betaine-homocysteine S-methyltransferase (BHMT) diverged from the expected Tree of Life (ToL) relationships. High sequence conservation in the paraphyletic group Plant-Fungi was identified for these two genes using a newly developed Python algorithm. Selective pressure analysis of ALS and BHMT protein sequences showed higher non-synonymous mutation ratios in comparisons between metazoans/fungi and metazoans/plants, supporting the hypothesis that these two genes have undergone non-ToL evolution in animals.
Assuntos
Aminoácidos Essenciais/biossíntese , Sequência Conservada/genética , Acetolactato Sintase/genética , Acetolactato Sintase/metabolismo , Sequência de Aminoácidos , Animais , Betaína-Homocisteína S-Metiltransferase/genética , Betaína-Homocisteína S-Metiltransferase/metabolismo , Evolução Biológica , Fungos/enzimologia , Fungos/genética , Humanos , Filogenia , Plantas/enzimologia , Plantas/genética , Sacaropina Desidrogenases/genética , Sacaropina Desidrogenases/metabolismoRESUMO
Betaine-homocysteine S-methyltransferase (BHMT) is an enzyme that converts homocysteine (Hcy) to methionine using betaine as a methyl donor. Betaine also acts as osmolyte in kidney medulla, protecting cells from high extracellular osmolarity. Hepatic BHMT expression is regulated by salt intake. Hormones, particularly corticosteroids, also regulate BHMT expression in rat liver. We investigated to know whether the corticoadrenal activity plays a role in kidney BHMT expression. BHMT activity in rat kidneys is several orders of magnitude lower than in rat livers and only restricted to the renal cortex. This study confirms that corticosteroids stimulate BHMT activity in the liver and, for the first time in an animal model, also up-regulate the BHMT gene expression. Besides, unlike the liver, corticosteroids in rat kidney down-regulate BHMT expression and activity. Given that the classical effect of adrenocortical activity on the kidney is associated with sodium and water re-absorption by the distal tubule leading to volume expansion, by promoting lesser use of betaine as a methyl donor, corticosteroids would preserve betaine for its other role as osmoprotectant against changes in the extracellular osmotic conditions. We conclude that corticosteroids are, at least in part, responsible for the inhibition of BHMT expression and activity in rat kidneys.