#036 Judith Campisi, Ph.D. on Cellular Senescence, Mitochondrial Dysfunction, Cancer & Aging
Dr. Judith Campisi, a professor of biogerontology at the Buck Institute for Research on Aging, discusses cellular senescence's pivotal role in aging and cancer. The conversation explores how damaged cells accumulate with age, contributing to chronic inflammation, and how lifestyle interventions like prolonged fasting and moderate exercise may improve healthspan.
Deep Dive Analysis
21 Topic Outline
Introduction to Dr. Judith Campisi and Cellular Senescence
Molecular and Cellular Processes Driving Aging
Inflammation and its Role in Aging (Inflammaging)
Understanding Cellular Senescence: Definition and Evolutionary Purpose
The Double-Edged Sword of Senescent Cell Secretions
Senescent Cells' Role in Cancer Progression
Clearing Senescent Cells: Healthspan vs. Lifespan Extension
Senescent Cells in the Brain and Neurodegeneration
Mechanisms Causing Cellular Senescence: DNA Damage
Mitochondrial Dysfunction as a Driver of Senescence
Impact of Prolonged Fasting on Senescent Cells and Immune System
mTOR Pathway, Rapamycin, and Senescent Cell Secretion
Effects of Senescent Cells on Stem Cell Function
Evolutionary Purpose of Mitochondrial Dysfunction-Induced Senescence
Lifestyle Factors Influencing DNA Damage and Telomere Length
Exercise Benefits for Healthspan and Aging
Challenges of Clinical Assays for DNA Damage and Senescence
Stochastic Variation in Aging Markers and Biological Messiness
NAD Precursors and Fasting Mimetics in Relation to Senescence
Cellular Senescence in Different Animal Species and Rapidly Proliferating Cells
Personal Lifestyle Practices for Healthy Aging
7 Key Concepts
Cellular Senescence
Cellular senescence is a stress response where cells lose the ability to divide essentially irreversibly and tend not to die easily, accumulating with age. These cells also secrete a variety of bioactive molecules, making it a double-edged sword that prevents cancer and aids wound healing, but later drives chronic inflammation and tissue degradation.
Inflammaging
Inflammaging, a term coined by Claudio Franceschi, refers to the low-level sterile chronic inflammation characteristic of almost all aging tissues. It involves the infiltration of innate immune cells without a pathogen, leading to gradual tissue degradation and loss of function.
Secretory Phenotype (SASP)
The secretory phenotype is a program activated in senescent cells that causes them to secrete 50-70 bioactive molecules, including cytokines, chemokines, growth factors, proteases, and lipids. These secretions can attract the immune system, remodel tissue, and influence neighboring cells, sometimes beneficially for repair but often detrimentally in chronic contexts.
Median vs. Maximum Lifespan
Median lifespan refers to the average lifespan of a population, while maximum lifespan is the longest an individual in that population can live. Studies clearing senescent cells in mice have shown increases in median lifespan (healthspan) but not significant increases in maximum lifespan.
Mitochondrial Dysfunction-Associated Senescence (MIDAS)
MIDAS is a distinct phenotype of cellular senescence induced by bad mitochondria and an altered NAD-NADH ratio, even without DNA damage. Cells undergoing MIDAS exhibit a different complement of secreted molecules compared to DNA damage-induced senescence, suggesting a different pathway of activation.
Hormetic Stress
Hormetic stress is a low-level stress, such as that induced by moderate exercise, that primes the body's stress responses to be hypervigilant. This allows the body to be better able to deal with subsequent, more severe stressors, potentially mitigating damage and improving overall resilience.
Stochastic Variation in Aging
Stochastic variation in aging refers to the observation that even genetically identical animals, sometimes in the same cage, show increasing variability in aging markers like senescent cell burden as they age. This suggests that random, messy aspects of biology, rather than just genetics, contribute to individual differences in aging outcomes.
9 Questions Answered
Most people who work on aging believe there are a few fundamental molecular and cellular processes that drive aging in multiple tissues, but the exact number and major drivers in each tissue are not precisely known. These processes almost certainly drive tissue health, but what actually drives lifespan is still unknown.
Cellular senescence is a stress response where cells stop dividing essentially irreversibly and tend not to die. It evolved as a double-edged sword, with the growth arrest being crucial for preventing cancer, and the secreted factors being beneficial for tissue repair and wound healing.
As senescent cells gradually accumulate with age, they begin to drive chronic inflammation through their secreted factors, attracting immune cells that cause tissue destruction and degeneration. They can also change neighboring epithelial cell behavior, leading to loss of tissue function and contributing to late-life cancer.
In mouse models, selectively causing senescent cells to die has improved healthspan, meaning animals were healthier in many respects and showed an increase in median lifespan, but not necessarily an increase in maximum lifespan.
Anything that causes severe or persistent damage to the genome, such as DNA damage or critically short telomeres, will drive cells into senescence. Additionally, mitochondrial dysfunction (having bad mitochondria) can also cause cells to senesce even in the absence of DNA damage.
Prolonged fasting may dampen mTOR activity, which suppresses the inflammatory arm of the secretory phenotype of senescent cells without killing them. It could also eliminate senescent cells and release stem cells from suppression, allowing them to proliferate and regenerate tissue.
If a cell has bad mitochondria, it's probably beneficial to prevent that cell from propagating to avoid clones of cells with defective mitochondria. This mechanism likely protects against accumulating degeneration within a tissue, rather than primarily against cancer.
Exercise is considered the single most important intervention that cuts across multiple diseases of aging, extending healthspan. It can have some effects on senescent cells in vivo, possibly by acting as a hormetic stress that primes other stress responses to be more vigilant.
Yes, it is possible to assess DNA damage load and senescent cell burden using peripheral blood or buccal swabs, with good antibodies and multiple markers. However, the difficulty lies in assaying tissue-specific senescence without invasive biopsies, and human data tends to be very messy due to individual and stochastic variation.
11 Actionable Insights
1. Prioritize Moderate Exercise
Engage in moderate but persistent exercise, as it is considered the single most important intervention for improving health span and mitigating multiple age-related diseases like sarcopenia.
2. Utilize Periodic Prolonged Fasting
Consider periodic prolonged fasts (e.g., 48 hours for mice, translating to ~4 days for humans) to robustly clear damaged cells, including senescent cells, and replenish stem cell populations.
3. Periodically Clear Senescent Cells
Explore strategies to incrementally knock down senescent cells every few months (in mice) or potentially every few years (in people) to improve health span, as senescent cells gradually accumulate.
4. Adopt Healthy Lifestyle Habits
Incorporate moderate exercise, maintain a good diet rich in greens and vegetables, and avoid smoking, as these are personal practices adopted by Dr. Campisi based on her research.
5. Manage Lifestyle for Telomere Health
Manage lifestyle factors such as stress, vitamin D levels, omega-3 intake, and sugar consumption, as these have been associated with telomere length and may help prevent the accumulation of cellular senescence.
6. Mimic mTOR Dampening with Fasting
Engage in periodic prolonged fasts, which may mimic the effects of mTOR dampening drugs by suppressing the inflammatory arm of the senescent cell secretory phenotype, thereby breaking feedback loops.
7. Clear Senescent Cells Naturally
Employ dietary and lifestyle interventions to help clear out senescent cells, which accumulate with age and contribute to chronic inflammation and aging pathologies.
8. Exercise During Chemotherapy
Incorporate moderate but persistent exercise into your regimen during chemotherapy to potentially mitigate some of the treatment’s side effects.
9. Exercise Caution with Senolytics
If senolytic drugs become available, exercise caution and avoid taking them around the time of surgery, as senescent cells play a beneficial role in wound healing.
10. Re-evaluate Fasting Mimetics for Senescence
Be aware that some ‘fasting mimetics’ like resveratrol may not directly affect senescent cells or their pro-inflammatory cytokine secretion, even if they offer other health benefits.
11. Support the Podcast
Contribute financially to the podcast by creating a pay-what-you-can subscription at foundmyfitness.com/crowdsponsor to help fund research, content creation, and community nurturing.
5 Key Quotes
Nobody dies of good health.
Dr. Judy Campisi
If you don't have this process, you die of cancer. If you do have this process, you're still going to get cancer.
Dr. Judy Campisi
I plan to die at 110 from a bullet wound from a jealous husband.
Thurgood Marshall (quoted by Dr. Judy Campisi)
I think exercise is probably the single most important intervention that cuts across multiple diseases.
Dr. Judy Campisi
human data tends to be messy.
Dr. Judy Campisi