Read a fascinating article in The Economist this morning about recent studies focusing on the relation of senescent cells (nicknamed zombie cells) to age-related diseases. The aforementioned article and this Medium article are much more eloquent summaries of these new findings. The actual studies (Baker Study and Xu Study) provide the most detailed reading. My goal here is to parse it out in layman’s terms for my own understanding.
What are senescent cells?
Senescent cells are worn-out cells that, while still serving their intended cellular duties, have ceased to make new copies of themselves. According to a recent study at Univerity of Connecticut by Dr. Ming Xu, their prevalence has been shown to increase as a result of aging, various chronic diseases, and radiation/chemotherapy treatment.
Why should I be concerned with them?
Long viewed as innocuous, more recent studies have shown that these cells “have been found to actively drive naturally occurring age-related tissue deterioration and contribute to several diseases associated with aging, including atherosclerosis and osteoarthritis” in addition to “show[ing] causal link between the accumulation of senescent cells and cognition-associated neuronal loss”.
So essentially, these zombie cells have been shown to drive both physical (arthritis, etc) and mental (Alzheimer’s, etc) deterioration.
This is a big deal as previously these diseases were something that just happened as you got older. But with these new findings, it leads to the question, “Is there something we can do about them?”
Fighting Senescent Cells with Senolytics
According to both the Xu study and one led by Dr. Darren Baker of the Mayo Clinic, the answer is a tentative yes…in mice. Both studies, working with mice, demonstrated positive results when using drugs (called senolytics) to reduce the numbers of senescent cells in their subjects.
Reduced Physical Deterioration
From the Xu study, “The senolytic cocktail, dasatinib plus quercetin, which causes selective elimination of senescent cells, decreased the number of naturally occurring senescent cells and their secretion of frailty-related proinflammatory cytokines in explants of human adipose tissue.”
They found that by eliminating senescent cells in specific parts of the body, there was a reduction in the cellular signals associated with degenerative physical diseases.
Reduced Mental Deterioration
Working with mice that were predisposed to ‘tangles’ of proteins in their brains caused by senescent cell buildup, the Mayo study found that after subjecting a portion of these mice to a twice-weekly dose senolytic (senescent cell-reducing) drugs:
“By the time these mice reached six months old, the tangles were almost entirely absent. When the mice were presented with objects they had encountered before, they approached them without hesitation, as healthy mice should. In contrast, mice whose brains were full of senescent cells approached the objects tentatively, as if they had never seen them before.”
These results suggest that by clearing out these ‘zombie cells’, researchers may have found a way to increase the period of healthy cognitive function.
And what was really interesting is that these results were shown in extremely old mice (the human equivalent of 80 years old), hinting that reducing these cells could be beneficial even at advanced stages of aging.
A Long Way Off
While I think it’s safe to say these are exciting preliminary findings, all of this was done with mice. Human trials are a long way down the road as are safe, effective senolytics. Despite this, taking steps to decrease your senescent cells through other methods could prove beneficial.
So, how can I decrease my senescent cell count right now?
As you might have guessed, two things have been correlated with reductions in senescent cells other than drugs; diet and exercise.
A 2016 study showed that exercise reduces the accumulation of senescent cells and the detrimental messages they send out to the rest of the body.
Intermittent fasting (the length of which is unclear) has also been shown to have the effect of reducing senescent cells. Not surprising as autophagy (cells recycling the less-optimal parts of themselves – read my experience with a 5-Day FMD here) is one of its primary benefits.
This science could be a big deal, time will tell
The Xu study ends with quite a grandiose claim, “As eliminating senescent cells and/or inhibiting their pro-inflammatory secretome also improves cardiovascular function, enhances insulin sensitivity, and reduces frailty, targeting this fundamental mechanism to prevent age-related bone loss suggests a novel treatment strategy not only for osteoporosis but also for multiple age-related co-morbidities.”
That’s leaving the door wide open for senescent cell reduction to play a huge role our neverending battle against aging.