From arylamine N-acetyltransferase to folate-dependent acetyl CoA hydrolase : impact of folic acid on the activity of (HUMAN)NAT1 and its homologue (MOUSE)NAT2

Acetyl Coenzyme A-dependent N-, O- and N,O-acetylation of aromatic amines and hydrazines by arylamine N-acetyltransferases is well characterised. Here, we describe experiments demonstrating that human arylamine N-acetyltransferase Type 1 and its murine homologue (Type 2) can also catalyse the direct hydrolysis of acetyl Coenzyme A in the presence of folate. This folate-dependent activity is exclusive to these two isoforms; no acetyl Coenzyme A hydrolysis was found when murine arylamine N-acetyltransferase Type 1 or recombinant bacterial arylamine N-acetyltransferases were incubated with folate. Proton nuclear magnetic resonance spectroscopy allowed chemical modifications occurring during the catalytic reaction to be analysed in real time, revealing that the disappearance of acetyl CH3 from acetyl Coenzyme A occurred concomitantly with the appearance of a CH3 peak corresponding to that of free acetate and suggesting that folate is not acetylated during the reaction. We propose that folate is a cofactor for this reaction and suggest it as an endogenous function of this widespread enzyme. Furthermore, in silico docking of folate within the active site of human arylamine N-acetyltransferase Type 1 suggests that folate may bind at the enzyme's active site, and facilitate acetyl Coenzyme A hydrolysis. The evidence presented in this paper adds to our growing understanding of the endogenous roles of human arylamine N-acetyltransferase Type 1 and its mouse homologue and expands the catalytic repertoire of these enzymes, demonstrating that they are by no means just xenobiotic metabolising enzymes but probably also play an important role in cellular metabolism. These data, together with the characterisation of a naphthoquinone inhibitor of folate-dependent acetyl Coenzyme A hydrolysis by human arylamine N-acetyltransferase Type 1/murine arylamine N-acetyltransferase Type 2, open up a range of future avenues of exploration, both for elucidating the developmental role of these enzymes and for improving chemotherapeutic approaches to pathological conditions including estrogen receptor-positive breast cancer

Evolution of Frailty profile in elderly after 78 months of initial evaluation, subproject of network FIBRA

INTRODUÇÃO: A fragilidade é reconhecida como uma síndrome geriátrica multidimensional, resultado de danos em sistemas fisiológicos complexamente interligados, ocasionando uma redução do limiar do funcionamento, favorecendo o aumento da vulnerabilidade para desfechos indesejáveis como quedas, incapacidade, institucionalização e morte prematura. OBJETIVO: Determinar a evolução da síndrome de fragilidade, em um período médio de 78 meses. MÉTODOS: Analisar variáveis relacionadas às características sócio demográficas, dados clínicos, medidas antropométricas, auto relato de doenças e sintomas, função física, presença de dor diária, além dos cinco critérios de fragilidade: velocidade de marcha, força de preensão, exaustão, atividade física, perda de peso. Além dos possíveis desfechos como: quedas, internações e óbitos. Foram contatados 150 idosos dos 385 avaliados inicialmente em 2008, participantes do projeto FIBRA, com idade >= 65 anos, residentes em Ribeirão Preto. Foi utilizado o instrumento padrão da avaliação inicial. RESULTADOS: Entre os 150 voluntários contatados, 87 (58%) foram reavaliados e 63 (42%) foram perdas. A média de idade foi de 80,43 anos (±6,7 DP) na avaliação atual. A maioria do sexo feminino (60,53%), raça branca (85,53%), casado (61,84%), com baixo nível de escolaridade (55,26%) e baixa renda familiar (47,37%). De acordo com o fenótipo da fragilidade de Fried et al (2001), foram classificados em: normais (N), pré frágeis (PF) e frágeis (F). A prevalência de fragilidade foi de 3,95% na AI e 42,11% na AA (p= 65 years, living in Ribeirão Preto. It used the same pattern as the initial assessment instrument. OUTCOMES: Among the 150 volunteers contacted, 87 (58%) were evaluated again and 63 (42%) were lost. The average age was 80.43 years (SD ± 6,7) in the current evaluation. Majority are women (60.53 %), white (85.53 %), married (61.84 %), with low education level (55.26 %) and low income (47.37%). According to the phenotype of frailty, Fried et al (2001) were classified as: normal (N), pre frail (PF) and frail (F). The prevalence of frailty was at 3,95% in the AI and 42.11% on AA (p<0,01). In relation the time between the two evaluations were expressive changes as: a greater number of individuals report their health now worse (p<0,01), most of chronic diseases (p<0,01), drugs daily used (p<0,01), frequency of hospitalizations (p<0,01) and frequency of falls (p<0,01). There was an increase of people with loss functional on IADL (42.11 % to 50 %) and elderly totally dependent (p<0,01), beyond increase of dependent for performing ADL (15.79% to 50 %), p <0,01. All chronic diseases were more frequent in AA and among pre frail and frail than the initial assessment (AI). There was a modification of frailty criteria with time, fatigue and walking speed showed significant differences (p<0,01). The risk of worsening frailty was associated with the loss of the IADL, p<0,01, OR (IC 1.26; 10.86). There was 12.64 % of deaths in the term between two valuations. The main features of the deaths were: male, worse functionality, need assistance to perform ADL, cognitive loss and pre frail. The change in the mini mental was associated with risk of death, p=0,09, adjusted OR 7.28 (IC 1.27; 41.84) as well as dependence to perform at least one function of ADL, p<0,01, adjusted OR 9.15 (IC 1.63; 51.29). CONCLUSIONS: The results show association with loss of IADL and risk of worsening frailty, and loss of ADL with risk of death in this sample. To assess the risks interfering early can change undesirables outcomes in the evolution of fragility

Arylamine N-acetyltransferases: from drug metabolism and pharmacogenetics to drug discovery.

Arylamine N-acetyltransferases (NATs) are polymorphic drug-metabolizing enzymes, acetylating arylamine carcinogens and drugs including hydralazine and sulphonamides. The slow NAT phenotype increases susceptibility to hydralazine and isoniazid toxicity and to occupational bladder cancer. The two polymorphic human NAT loci show linkage disequilibrium. All mammalian Nat genes have an intronless open reading frame and non-coding exons. The human gene products NAT1 and NAT2 have distinct substrate specificities: NAT2 acetylates hydralazine and human NAT1 acetylates p-aminosalicylate (p-AS) and the folate catabolite para-aminobenzoylglutamate (p-abaglu). Human NAT2 is mainly in liver and gut. Human NAT1 and its murine homologue are in many adult tissues and in early embryos. Human NAT1 is strongly expressed in oestrogen receptor-positive breast cancer and may contribute to folate and acetyl CoA homeostasis. NAT enzymes act through a catalytic triad of Cys, His and Asp with the architecture of the active site-modulating specificity. Polymorphisms may cause unfolded protein. The C-terminus helps bind acetyl CoA and differs among NATs including prokaryotic homologues. NAT in Salmonella typhimurium supports carcinogen activation and NAT in mycobacteria metabolizes isoniazid with polymorphism a minor factor in isoniazid resistance. Importantly, nat is in a gene cluster essential for Mycobacterium tuberculosis survival inside macrophages. NAT inhibitors are a starting point for novel anti-tuberculosis drugs. Human NAT1-specific inhibitors may act in biomarker detection in breast cancer and in cancer therapy. NAT inhibitors for co-administration with 5-aminosalicylate (5-AS) in inflammatory bowel disease has prompted ongoing investigations of azoreductases in gut bacteria which release 5-AS from prodrugs including balsalazide