- Research is ongoing about potential strategies to prolong life.
- A meta-analysis found that the drug rapamycin prolongs life in several vertebrate species.
- Rapamycin appeared to prolong life at a level similar to dietary restrictions.
How to prolong life is a key area of scientific research. Experts are interested in medications that have the potential to boost longevity.
A recent meta-analysis published in
The results confirmed that dietary restriction appears to prolong life and that rapamycin offers similar benefits.
Researchers also found that metformin did not seem to prolong life. More research is required to see how rapamycin might help boost longevity in people.
In this paper, researchers note that decreasing food intake without malnourishment appears to prolong life but that this strategy is difficult for people to stick to. Thus, looking into possible medications that produce similar effects is an area of research.
The two medications that were the focus of this analysis were rapamycin and metformin. According to the National Cancer Institute,
This analysis involved a systematic literature search to find relevant data. The final analysis included data from 167 papers looking at eight total vertebrate species, seeking to see how both medications affected longevity and how they compared to dietary restrictions.
Researchers extracted information on average and median lifespan from the papers.
For this analysis, the two types of dietary restriction were caloric reduction and fasting, and researchers also sought to see if the results differed based on the sex of the animals involved.
The data came from animals like mice, rats, turquoise killifish, and rhesus macaques. Overall, there were more males studied than females. There was also the most data on dietary restriction, and the most common type of dietary restriction was decreasing the number of calories.
Regarding dietary restriction, the findings suggested great variation regarding the effects.
Overall, researchers found that dietary restriction and rapamycin had a similar impact and appeared to contribute to prolonged life. Metformin appeared to only have a minimal impact on life extension.
Aside from one metformin model, there appeared to be no consistent differences between male and female animals regarding longevity.
Study author Zahida Sultanova, PhD, a Leverhulme Early Career Research Fellow with the University of East Anglia, in the United Kingdom summarized the key findings of the study to Medical News Today:
“We checked whether the two best-known ‘diet-mimic’ drugs increase lifespan similar to eating less in animals. By pooling data from 167 studies, we found that rapamycin is almost as reliable as eating less for increasing lifespan, whereas metformin is not. In other words, a compound that was extracted from soil bacteria 50 years ago seems able to copy many of the biological effects of a permanent diet, at least in lab animals.”
This research analyzed animal data but did not include data about people. Additionally, most of these studies involved these animals in a laboratory setting and only looked at a small number of species.
This meta-analysis was also the work of only three researchers, sometimes with only one researcher doing a component of the work, which could have impacted the results.
Researchers had the least amount of data on metformin, so more research about this medication might be helpful.
They also operated under the assumption that if a paper did not specify male or female subjects, it was a mixed group, which could have been incorrect.
The authors further note that the “results were sensitive to how lifespan was reported.”
Researchers also acknowledge strong publication bias and a lot of heterogeneity. Additionally, the type of measure used in study reporting affected results. In one measurement, the impact on life extension disappeared for rapamycin.
For the most part, the authors did not find a consistent difference in results based on the sex of the animals. They explain this could be because of “differences in taxonomic groups studied […] and the calculated effect size.”
Sultanova noted the following cautions regarding the findings:
“This study includes a high number of scientific studies conducted on different organisms such as mice, fish and monkeys. However, survival results in humans are not included because these drugs were not tested in humans for lifespan extension. Even if they are, the studies will take a long time considering the length of human lifespan. So, we do not recommend people to take rapamycin before the results of human trials consistently show that there are no side effects.”
Researchers suggest the need for research involving other species in natural and laboratory settings. They also note the need to understand the difference in impact for “different strains of the same species exposed to the same treatment.”
Future research can further focus on the differences between rapamycin and metformin and why they impact lifespan differently. More research into the differences in rapamycin’s results in males and females could be helpful as well.
More research can be done to see if rapamycin can promote prolonged life in people, but there may be some challenges in this area.
Mir Ali, MD, a board-certified general surgeon, bariatric surgeon, and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, CA, who was not involved in the study, told MNT that it “shows the contribution of the immune system to lifespan, as rapamycin is an immunosuppressive medication.“
According to him: “The most logical next step is to explore the findings in humans; however, this would be a difficult study to design as rapamycin is a medication used in specific cancers and organ transplant and has significant side effects.”
Despite this, the results show a potential benefit of rapamycin that warrants more research.
Sultanova explained that: “Clinically, that puts rapamycin (and the mTOR pathway it targets) at the front of the queue for future anti-ageing therapies in humans. The compound had already been used for organ-transplant patients, so medical professionals understand its potential side effects.“
“The next step is waiting for the results of ongoing human trials that test lower and intermittent doses of rapamycin and refining the compound to ‘rapalog’ versions that keep the benefits while omitting side-effects such as immune suppression,“ she told us.
