Métodos para la determinación del estado del magnesio en humanos / Methods of assessment of magnesium status in humans / Métodos para a determinação do estado do magnésio em humanos

En la actualidad, datos epidemiológicos sugieren que, en países occidentales, la ingesta de magnesio no satisface la ingesta recomendada, lo que apoya un riesgo de deficiencia de magnesio latente en estas poblaciones. La evaluación del estado de magnesio sigue siendo un desafío para el laboratorio clínico ya que el magnesio se encuentra distribuido mayoritariamente en el hueso y tejidos blandos. Existe la necesidad de conciliación entre una prueba de fácil acceso, rápida, sensible y representativa del magnesio intracelular. La utilidad de diferentes biomarcadores en sujetos sanos ha sido evaluada; se ha reportado que el magnesio en plasma, eritrocitos y orina parecen ser biomarcadores sensibles a la ingesta dietética y útiles como biomarcadores en la población general. Sin embargo, esto no es concluyente, ya que se resalta que aún se requieren estudios mejor diseñados, que impliquen factores como mayor población empleada, dosis y tiempo de suplementación. El progreso en la genética y la genómica abren perspectivas interesantes en la búsqueda de estos biomarcadores que permitan cuantificar los niveles de magnesio celular así como también las reservas de todo el cuerpo, para poder así establecer recomendaciones dietéticas mejor ajustadas a la población.

Epidemiological studies suggest that dietary magnesium in the Western countries does not meet the recommended intake, supporting a risk of latent magnesium deficiency with Western diet behavior. Assessment of magnesium status remains a major challenge for the clinical laboratory, since, magnesium storage is mostly found in bone and soft tissues. The conciliation between an easy obtained sample, rapid and robust laboratory test, and the parameter representative for intracellular magnesium is extremely difficult to reach. In a current systematic review study, the usefulness of magnesium status biomarkers in healthy subjects has been evaluated. It is proposed that plasma and erythrocyte magnesium, and urinary magnesium excretion which respond to dietary manipulation appear to be useful biomarkers in the general population. However, it is emphasized that well-designed studies of sufficient size with varying doses and duration of magnesium supplementation are still required. The development of specific and sensible biomarkers, making it possible to obtain cell magnesium levels as well as body magnesium pool evaluation, relevant to study individuals, small and large populations, remains a major challenge for the assessment of magnesium status. A progress in genetics and genomics opens new interesting perspectives in the search of these biomarkers.

Na atualidade, dados epidemiológicos sugerem que, nos países ocidentais, a ingestão de magnésio não supre a ingestão recomendada, o que apoia um risco de deficiência de magnésio latente nestas populações. A avaliação do estado do magnésio continua sendo um desafio para o laboratório clínico, visto que o magnésio se encontra distribuído principalmente no osso e nos tecidos moles. Há a necessidade de conciliar evidência facilmente acessível, rápida, sensível e representativa do magnésio intracelular. A utilidade de vários biomarcadores em indivíduos saudáveis foi avaliada, e foi relatado que o magnésio em plasma, eritrócitos e urina parecem ser biomarcadores sensíveis à ingestão dietética e úteis como biomarcadores na população geral. No entanto, esta não é conclusiva, uma vez que se destaca que são requeridos ainda estudos melhor desenhados, envolvendo fatores como utilização de maior população, dosagem e tempo de suplementação. Um avanço na genética e na genômica abre perspectivas interessantes na busca desses biomarcadores para poder quantificar os níveis de magnésio celular bem como as reservas do corpo inteiro, e assim poder estabelecer melhores recomendações na dieta adaptadas à população.

The Structure and Metabolic Diversity of Population of Pea Microsymbionts Isolated from Root Nodules.

Aims: The study of strains belonging to local rhizobial population, concerning their diversity in the genetic, metabolic and symbiotic properties, and their prevalence in the microsymbiont population. Methodology: 257 rhizobial isolates recovered from nodules of five pea (Pisum sativum cv. Ramrod) plants grown at one site were classified using PCR-RFLP analysis of 16-23S rRNA ITS. After that, for representative group of 55 strains, 16-23S rRNA ITS region was sequenced, nodA-F region was analyzed by PCR-RFLP and sequencing, metabolic capabilities were studied using Biolog`s and growth tests and symbiotic performance in plant tests were assayed. Results: Individual plants were infected by numerous and diverse strains, however, in the entire sampled population of microsymbionts, only three large clusters of strains could be distinguished on the basis of PCR-RFLP and sequence analyses of 16S-23S rRNA ITS region. Rhizobium strains belonging to different groups varied in plasmid number and the amount of plasmid DNA, utilization of carbon and energy sources, growth on soil extractbased media and the ability for symbiotic plant growth promotion. The most numerous group of the isolates was characterized by the high plasmid DNA content, low number of utilized sugar substrates, and comprised numerous strains with low symbiotic efficiency. Conclusion: Sampled population of pea microsymbionts had its own characteristic structure with clearly distinguishable sub-populations, composed of numerous strains - probably descendants of a few old lineages, which diversified in the lapse of time. These strains are still competing during root nodule colonization, resulting in the symbiosis of individual pea plants with broad spectrum of different Rhizobium strains.