It is old news that diet may have a life-extending effect. Researchers from Leibniz Institute on Aging – Fritz Lipmann Institute (FLI) in Jena, Germany, show that on the one hand stem-cell function is improved in mice by caloric restriction, but also leads to a fatal weakening of their immune system. This fatal weakening contracts the life-lengthening effect of diet delete. The results are published in the Journal of Experimental Medicine.
A few years ago, scientists were successful in extending the life span of a worm, fruit fly, and rats approximately 50% by initiating a simple caloric restriction. This finding immediately gave hope of having found one key to a longer life for humans. When these results were transferred, to long-lived primates shortly after, it was not equally successful
and enthusiasm waned. A scientist on aging Karl Lenhard Rudolph, Scientific Director at the Leibniz Institute on Aging – Fritz Lipmann Institute (FLI) in Jena, Germany, and his team went on to show, “that caloric restriction even has a severe downside. In feeding experiments, the stem cells of mice, which were set on a diet, were found to age slower – but the murine immune system was almost completely cut down. Outside of optimal, sterile laboratory conditions, this could lead to severe live-shortening infections” (Kästner, 2016). The results of the study are published in the March 7, 2016, issue of the Journal of Experimental Medicine.
This study specifically focused on the effects of calorie restriction on blood stem cells. The stem cells are responsible for making red blood cells or lymphocytes (immune cells). As in any other adult stem cell, blood cell functionality decreases with every single cell division, the stem cells age. This is why they stay in a resting phase called quiescence most of the time. Stem cells are only activated when a massive cell reproduction is required, for example after great blood loss.
In this study, researchers investigated how only a 30% food restriction affects stem cell aging in mice. One main result was that the red blood stem cells remained quiescent even as simulated stress would have required their activation. Diet duration had no effect. The upside of all this was that blood stem cells did not age in their functionality to make new blood cells remained as strong as ever even one year after diet.
The downside of the long-term diet evidenced the mice’s immune system was almost completely shut down. The diet had no strong effect on the overall blood cell count but the production of lymphocytes (immune cells), needed for immune defense, and decreased by up to 75%. Consequently, the mice were severely prone to bacterial infections.
“The study provides the first experimental evidence that long-term caloric restriction – as intervention to slow down aging – increases stem cell functionality, but results in immune defects in the context of prolonged bacterial infection, too. Thus, positive effects of a diet are not transferable to humans one to one,” Rudolph sums up the study results. Even if – under laboratory conditions – aging of single cells or tissues may be slowed down through a diet, the immune suppression may have fatal consequences in real life. To benefit from caloric restriction or medicinal mimetika aiming at increasing health in the elderly, possible risks of such interventions to come down with life-threatening infections remain to be elucidated. “In sepsis patients, we see a higher survival rate for those with a higher body mass than for patients who are very lean,” Prof. Dr. Michael Bauer, Director of the Center for Sepsis Control and Care at University Hospital Jena (UKJ), concurs (Kästner, 2016).
Dietary restriction improves repopulation but impairs lymphoid differentiation capacity of hematopoietic stem cells in early aging, Tang D, Tao S, Chen Z, Koliesnik IO, Gebert N, Calmes PG, Hörr V, Löffler B, Morita Y, Rudolph KL, Journal of Experimental Medicine, doi: 10.1084/jem.20151100, published 7 March 2016.
Kästner, D. E. (2016, March 14). THE UP AND DOWN SIDE OF CALORIC RESTRICTION FOR AGING AND HEALTH. Retrieved March 15, 2016, from fli Leibniz Institute on Aging – Fritz Lipmann Institute: http://www.leibniz-fli.de/nc/institute/public-relations/detailpage/?tx_news_pi1%5Bnews%5D=2510&cHash=7d5cbe951317dc513959534631b4def2
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