RESUMO
These last 20 years, several techniques have been developed for quantifying DNA methylation, the most studied epigenetic marks in eukaryotes, including the gold standard method, whole-genome bisulphite sequencing (WGBS). WGBS quantifies genome-wide DNA methylation but has several inconveniences rendering it less suitable for population-scale epigenetic studies. The high cost of deep sequencing and the large amounts of data generated prompted us to seek an alternative approach. Restricting studies to parts of the genome would be a satisfactory alternative had there not been a major limitation: the need to select upstream targets corresponding to differentially methylated regions (DMRs) as targets. Given the need to study large numbers of samples, we propose a strategy for investigating DNA methylation variation in natural populations, considering the structural complexity of the genomes with their size and their content in unique as coding regions versus repeated regions as transposable elements. We first identified regions of highly variable DNA methylation in a representative subset of genotypes representative of the biological diversity in the population by WGBS. We then analysed the variations of DNA methylation in these targeted regions at the population level by Sequencing Capture Bisulphite (SeqCapBis). The entire strategy was then validated by applying it to another species. Our strategy was developed as a proof of concept on natural populations of two forest species: Populus nigra and Quercus petraea.
RESUMO
Simultaneously to the rapid increase of overweight and obesity a great number of products oriented to weight loss have emerged in the market. The aim of this study was to evaluate the scientific evidence supporting the use of three products designed for weight loss available in Chile: a lipidic emulsion that stimulates ileal brake, a protease inhibitor and an amylase inhibitor. The results indicate that the amylase and protease inhibitors efficiently inhibit the respective enzymatic activities in vitro; however, they do not affect weight control in clinical trials carried out in normal weight as well as in obese subjects. Thus, there is not enough evidence supporting the use of these products for weight control. On the other hand, the results concerning the lipidic emulsion are conflicting and more studies are needed to confirm its possible effect on weight control.
Paralelamente al rápido aumento de la prevalencia de sobrepeso y obesidad han surgido en el mercado múltiples productos que prometen estimular la pérdida de peso sin modificar la dieta y estilo de vida de los individuos. El objetivo de este trabajo es evaluar la evidencia científica que apoye el uso de tres productos disponibles en Chile para el control ponderal y la reducción de sobrepeso y obesidad: una emulsión lipídica que estimula el freno ileal, un inhibidor de proteasa y un inhibidor de amilasa. Los resultados indican que el inhibidor de amilasa y el inhibidor de proteasa, si bien parecen funcionar in vitro, no muestran ningún efecto sobre el control ponderal en los ensayos clínicos realizados tanto en sujetos normopeso como en obesos. El nivel de evidencia que apoya el uso de estos productos para el control ponderal es por lo tanto insuficiente. En caso de la emulsión lipídica, los resultados son conflictivos y más estudios son necesarios para confirmar su eventual efecto sobre el control del peso corporal.