According to a study, the number of copies of a gene used to digest complex sugars promotes obesity. Each less copy of this gene increases this risk by 20%.
What if the mysteries of obesity lay in the saliva? In any case, this is what is suggested by a recent study based on a genetic analysis and carried out by a team bringing together researchers from the CNRS, the Institut Pasteur de Lille, and the Imperial College London. According to this work published on Sunday in the specialist journal Nature Genetics, people who have the fewest copies of the salivary amylase gene (and thus little of this enzyme in their blood) have a 10-fold risk of becoming obese. And for Professor Philippe Froguel, coordinator of the study, each less copy of this gene increases the risk of obesity by 20%. This is the first time that the genetic link between the digestion of complex carbohydrates (starches) and obesity has been demonstrated.
Two hypotheses to explore to explain this link
According to these scientists, “we do not yet know why salivary amylase deficiency promotes obesity.” However, two hypotheses are being considered by this international team. On the one hand, chewing foods and their partial digestion in the mouth could have a hormonal effect leading to satiety which would be reduced in the event of a deficiency in salivary amylase (AMY1).
On the other hand, the poor digestion of starches could modify the intestinal flora and thus indirectly contribute to obesity or even diabetes as suggested by the first studies carried out in people with high or low salivary amylase. Thus, people with low salivary amylase have abnormally high blood sugar levels when they are fed starch.
Prospects for the treatment of obesity
In addition, these results open up prospects for the prevention and treatment of obesity, taking into account the digestion of food and its intestinal fate, these researchers confide.
And the latter recall that today, a billion people are overweight. If at the level of an entire population it is the deleterious environment that promotes obesity, at the individual level genetic factors explain 70% of the genetic risk of people predisposed to obesity.
Finally, about 5% of very obese people carry a mutation in one of the genes controlling appetite that is sufficient to make them obese. “By itself, the region of the genome containing the AMY1 gene would explain nearly 10% of the genetic risk,” the team concludes.
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