In a new study published in the journal Nature Communications, researchers have taken a close look at three treatment approaches that have been widely believed to slow the ageing process. However, when tested in mice, these treatments proved largely ineffective in their supposed impact on ageing.
“There is no internal clock of ageing that you can regulate with a simple switch – at least not in the form of the treatments studied here,” concludes Dr Dan Ehninger of the German Centre for Neurodegenerative Diseases (DZNE), the initiator of the study. The team has developed a new analytical approach to make influences on ageing processes measurable.
“We chose three regulators for our interventions that many experts believe slow down aging,” explains Prof Martin Hrab de Angelis, who also drove the project with his team. One of them is intermittent fasting, in which the calories consumed are reduced. Number two targets a central node of cell metabolism (mTOR), which is also the target of the supposed “anti-ageing drug” rapamycin. Number three, in turn, interferes with the release of growth hormone. Similar treatments are also used by humans, although their efficacy with regard to ageing has not been sufficiently proven.
For the assessment in mice, the scientists developed a new answer to the question of how to measure ageing. “Many researchers in recent decades have used lifespan as an indirect measure of ageing,” explains Dan Ehninger, who is a senior scientist at DZNE. So, for example, how old do mice get – and how can that lifespan be extended? “It is often assumed that if they just live longer, they will also age more slowly. But the problem is that mice, like many other organisms, do not die from general old age, but from very specific diseases,” says Ehninger. For example, up to 90 percent of mice die from tumors that form in their bodies at an advanced age. “So, if you were to look at the whole genome for factors that make mice become long-lived, you would like find many genes that suppress tumor development – and not necessarily genes that play a general role in aging.”
For their study, the scientists therefore chose an approach that does not emphasize lifespan, but rather focused on a comprehensive investigation of age-related changes in a wide range of bodily functions. “You can think of it as a complete health status survey,” says Martin Hrab de Angelis: “The health check results in a compendium of hundreds of factors covering many areas of physiology” – an exact description of the state of the animal at the moment of examination. That’s exactly the approach the researchers applied to the animals subjected to one of the three treatment approaches that supposedly slow ageing. Across different life stages, they were analysed and compared: How much does each parameter typically change at a given stage of life? And, do parameters change more slowly when the mice are given one of the three treatments? This study design makes it possible to determine precisely whether the natural aging process can be slowed, and with it the deterioration of important physiological functions.
The results were unambiguous: Although the researchers were able to identify individual cases in which old mice looked younger than they actually were, it was clear that “this effect was not due to slowing down aging, but rather due to age-independent factors,” says Dan Ehninger. “The fact that a treatment already has its effect in young mice – prior to the appearance of age-dependent change in health measures – proves that these are compensatory, general health-promoting effects, not a targeting of aging mechanisms.”
The DZNE and Helmholtz Diabetes Center teams have now set their sights on the next goal: They want to investigate other treatment approaches that experts believe can slow aging. The researchers hope that the new research method will provide a more comprehensive picture of possible treatment approaches and their effectiveness.
