In search of the genes determining our life expectancy, a team of scientists has identified in mice several specific sites of the genome that are associated with longevity. Among these, genetic regions affecting body weight and growth in early life have been shown to be closely linked to longevity, not only in mice, but also in humans.
To conduct their research, the scientists at the École polytechnique de Lausanne had the DNA sequence of 3,276 genetically inherited mice from three US research centers, as well as data on their age at death, weight at different times in their lives and the size of the litter they came from.
The genomic regions (called loci) that they identified as being likely linked to longevity were not the same in females as in males, with only one locus being shared by both sexes. “This is not surprising, as males and females have different life histories. In general, females live longer than males, [c’est ce que nous avons observé chez les souris]just like in humans”, points out Maroun Bou Sleiman, first author of the article, published in Science, which reports the results of this study.
“This does not exclude the possibility that similar processes could contribute to the regulation of aging and longevity in both sexes,” the researchers argue in their paper.
It also appeared that certain loci affected life expectancy only after a certain age.
The researchers then tried to find in these loci – which can contain 50 to 100 genes – which genes probably played a role in the longevity of the mice. To confirm the involvement of these genes in longevity, they then showed that blocking these genes in the worm Caenorhabditis elegant decreased the life expectancy of these model animals, which have long been used in longevity studies. “We know that the function of genes which are very important is generally conserved during evolution”, underlines Mr. Bou Sleiman to explain the use of these animals.
“The results of our study do not allow us to attribute causal roles to the genes that we have uncovered. However, they provide candidate genes, hypotheses for more in-depth studies,” explained Mr. Bou Sleiman.
The researchers noted that certain loci associated with longevity overlapped with loci known to mediate body weight or growth, particularly in males, indicating the importance of the latter two factors determined in part by genetics in longevity. In this regard, the researchers observed an inverse relationship between body weight early in life in mice and their longevity, and this relationship was more pronounced in males.
In particular, they found that mice that were born into large litters — and therefore had less access to nutrients early in life — weighed less at six months than animals from of a small range. But their small weight meant that they lived longer than the mice that had grown faster and had reached a greater weight.
The study authors then found these same links between pre-puberty weight and longevity in large human databases. “Aging, growth and development are interconnected. The more rapid and significant growth one has, the less, in general, one will have a great longevity. It has been shown in humans, as well as in various model organisms, such as the worm and Drosophila. The message is therefore that, if we want to intervene on longevity, we cannot ignore the history of the organism from its very beginning and the fact that there are genetic and non-genetic factors which come into play”, emphasizes Mr. Bou Suleiman.
This observation that weight in early life is related to longevity comes as no surprise to pediatrician and lipidologist Julie St-Pierre. “This new study is a continuation of what we already knew, that children who are born heavier than average and who grow in weight more than height during childhood are at greater risk of cardiometabolic diseases in adulthood. The study of Science now shows the corollary, that it also harms longevity,” she says.
Aging, growth and development are interconnected. The more rapid and significant growth one has, the less, in general, one will have a great longevity. It has been shown in humans, as well as in various model organisms, such as the worm and Drosophila. So the message is that if you want to intervene on longevity, you can’t ignore the history of the organism from its beginning and the fact that there are genetic and non-genetic factors that come into play.
If a child is born with a certain genetic predisposition for being overweight or obese, it is however possible to counteract the effect of genetics by intervening in the choice of food, as well as the time spent in front of screens and the time spent to physical activity, points out the specialist, who is a professor at McGill University.
“We never impose a diet on a child, because limiting calories while the brain and bones are growing would be catastrophic,” she says.
Rather, it is recommended to “early diversify” the diet, in particular by introducing solids a little earlier. “This diversification helps to prevent food allergies, but also to develop a better microbiota, which will protect the baby against obesity,” she points out.
Up to six months, breastfeeding is the food par excellence, especially since it promotes the development of a better microbiota. But after the feedings, we will introduce fruits, vegetables, whole grains, good vegetable and animal proteins, so that at six months, we arrive at a diet that resembles that of adults, advises the DD St Pierre.
Replace smooth purees with ones that contain whole fiber. And we don’t cut dairy products. “There has been a fashion to cut out dairy products in babies and turn to veganism. This is absolutely not recommended because dairy products promote the development of a better microbiota. We recommend dairy products, such as kefir, natural yogurts and cheeses, ”says the pediatrician.
We advise against low-fat products, except for people with familial hypercholesterolemia, and fruit juices, even if they are 100% fruit and free of added sugar. In fact, we ban all free sugars for children under two years old and we limit the intake to 5% of total calorie consumption in a day for children from two to eight years old, she continues.
By free sugars, we mean not only the sugar that could be added to yogurt, but also processed fruits, such as compotes that are too smooth and fruit juices.
On the other hand, we recommend the consumption of 7 to 10 servings of fruits and vegetables per day.
Although almost 80% of the problem of obesity is food-related, physical activity, time spent in front of screens and quality of sleep also play a very important role. “The appearance of baby chairs designed to hold a tablet is madness. We don’t get babies out of the stroller fast enough. We don’t make them do enough exercises on their stomachs when they’re awake”, laments the DD St Pierre.
The latter mentions that, among the hundreds of families of all origins who have adopted this nutritional approach, 94% have succeeded in thwarting their child’s genetics and thus protecting his cardiometabolic health, and even ensuring greater longevity.