What is the role of oxidative stress in aging?

Oxidative stress, caused by reactive oxygen species (free radicals) from metabolic processes, contributes to aging by damaging proteins and fatty acids. While antioxidants failed globally in trials, selective inhibition of ROS generation points to a more nuanced role, where ROS also function as signaling molecules.

How does exercise impact mitochondrial health and aging?

Exercising, particularly zone 2 cardio, is believed to improve mitochondrial health and function, thereby reducing the degradation of mitochondrial efficiency that occurs with aging. It is considered one of the best anti-aging interventions.

What role does insulin and IGF-1 play in aging if glucose is a 'dirty fuel'?

High peaks of insulin, elicited by fast-absorbing glucose, are considered detrimental to the aging process. The intensity of these insulin peaks, rather than just average glucose, is a critical factor, suggesting that mitigating these spikes is important for longevity.

Why are GLP-1 agonists like tirzepatide considered promising for longevity?

GLP-1 agonists improve glucose control by increasing GLP-1 in the system, overcoming beta-cell resistance, and leading to better glucose management without necessarily increasing insulin levels. Personal experimentation showed significant improvements in metabolic markers and unexpected satiety, making them potential geroprotectors.

What is the significance of the 'J-curve' phenomenon in health metrics like blood glucose and blood pressure?

The J-curve indicates that for certain health metrics like A1C and blood pressure, lower values (within a healthy range, avoiding symptoms) are generally better for longevity, even if they fall below traditionally 'normal' ranges. This challenges the conventional idea of a broad normal range.

Is excess body fat (adiposity) inherently problematic for longevity, even if metabolically healthy?

While individuals can be metabolically healthy with excess weight, there's concern about the long-term effects. Visceral fat is highly predictive of negative health outcomes. The long-term impact on metabolic health and increased risk of complications from sustained excess weight remain a worry.

Why is the immune system considered the 'fifth horseman' of aging?

The immune system plays a crucial role in aging, as evidenced by the dramatically increased mortality from infections like COVID-19 and influenza in older adults. Immunosenescence, or aging of the immune system, leads to decreased vaccine efficacy and increased susceptibility to severe outcomes.

How does growth hormone affect thymic regeneration and overall aging?

Human growth hormone has been shown to induce thymogenesis (thymus regeneration) and increase naive T-cells, which could theoretically improve immune function. However, it also induces glucose intolerance and has been correlated with shorter lifespans in larger animal species and taller humans, raising concerns about chronic use.

How does rapamycin impact the immune system?

Rapamycin, typically an immunosuppressant at high, continuous doses, can show beneficial, immune-enhancing effects when administered in lower, intermittent doses. Studies have shown it can improve vaccine response in older adults, though its long-term effects on immune function and broader anti-aging benefits in humans are still debated.

Why are NAD+ levels important and why do they decline with age?

NAD+ is a crucial coenzyme for hundreds of metabolic and DNA repair enzymes, including sirtuins. Its levels decline with age primarily due to increased degradation by enzymes like CD38, which acts as an NAD+ hydrolase. This decline reduces metabolic efficiency and impacts DNA repair.

What are the concerns with supplementing NAD+ precursors like NMN and NR?

While NMN and NR raise NAD+ levels, they can lead to an increase in downstream metabolites like methyl nicotinamide, potentially depleting the body's one-carbon cycle (e.g., increasing homocysteine). There are also concerns about these supplementing exacerbating inflammation (SASPs) and potentially accelerating tumor growth in certain models.

Are aging clocks reliable for personalized health management?

Currently, aging clocks are primarily research tools and not ready for routine patient management. While some, like the Dunedin Pace clock, respond to interventions, they can be noisy and show significant variation based on blood cell composition and even time of day. New proteomics-based clocks show promise but carry risks of false positives and over-medicalization.

359 ‒ How metabolic and immune system dysfunction drive the aging process, NAD, aging clocks, & more

Q: Which fuel source is considered 'cleanest' for the body and why?

Ketones, specifically beta-hydroxybutyrate, are considered the cleanest fuel source, generating fewer byproducts and less oxidative stress compared to fatty acids and especially glucose, which is considered the 'dirtiest' fuel.

Peter Attia MD

Science & Technology3 min read152 min video

Aug 4, 2025|86,079 views|1,571|131

Peter Attia MD Dr. Peter Attia Early Medical The Drive Podcast The Drive Longevity Zone 2

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Key Moments

TL;DR

Metabolism and immune health are key to aging, with focus on fuel utilization, NAD+ decline, and immune system aging.

Key Insights

The immune system and central nervous system are rate-limiting organs for aging.

Metabolism, particularly fuel utilization (ketones, fatty acids, glucose), significantly impacts aging.

Oxidative stress, while complex, remains a factor in aging, with antioxidants having nuanced effects.

NAD+ levels decline with age, impacting sirtuin activity and overall metabolism; its supplementation is complex.

The aging immune system shows reduced vaccine response and increased susceptibility to infections, with thymic shrinkage playing a role.

Biomarkers and 'aging clocks' are emerging tools but require further validation for clinical use.

THE CENTRAL ROLE OF THE IMMUNE AND NERVOUS SYSTEMS

The conversation highlights the immune system and the central nervous system as two crucial organs that are rate-limiting in the aging process. Their distributed nature means their function impacts the entire organism. Research indicates that biomarkers measuring aging in these organs are highly predictive of lifespan. Furthermore, studies in mice suggest that impairing the immune system, even through specific genetic mutations affecting DNA repair or mitochondrial function, can accelerate aging across the entire organism, underscoring the immune system's profound influence on systemic aging.

METABOLISM AND FUEL UTILIZATION IN AGING

Metabolism is a cornerstone of aging, with a particular emphasis on fuel utilization. The efficiency with which our bodies burn different substrates—ketones, fatty acids, glucose, and lactate—plays a significant role. Ketones are considered the cleanest fuel, generating fewer byproducts and less oxidative stress. Conversely, glucose, especially rapidly absorbed forms leading to high insulin spikes, is associated with greater metabolic burden and is linked to interventions that have shown lifespan benefits in studies like the ITP.

THE NUANCES OF OXIDATIVE STRESS AND AGING

While the theory that oxidative stress is a primary driver of aging has faced challenges, its role remains significant. The process of energy production in mitochondria inherently leaks electrons, which react with oxygen to form reactive oxygen species (ROS). While ROS can be damaging, they also serve signaling roles, particularly during exercise. The failure of broad-spectrum antioxidants in trials suggests that a targeted approach is needed, rather than general suppression, as ROS can have beneficial as well as detrimental effects depending on the context.

NAD+ METABOLISM, SIRTUINS, AND AGING

Nicotinamide adenine dinucleotide (NAD+) is a critical coenzyme for numerous metabolic reactions and DNA repair via sirtuins. NAD+ levels decline significantly with age, impacting enzyme activity and metabolic efficiency. While supplementation with NAD+ precursors like NMN and NR is popular, it's complex. Production and degradation pathways, involving enzymes like CD38 and PARPs, are crucial. Research suggests that elevated CD38 activity drives NAD+ depletion, and while NMN/NR supplementation can increase NAD+ levels, potential side effects like elevated homocysteine and increased production of pro-inflammatory SASP factors warrant caution and further study.

IMMUNE SYSTEM AGING AND INFECTION SUSCEPTIBILITY

Aging significantly impairs immune function, a phenomenon termed 'immunosenescence'. This decline is linked to thymic involution, where the thymus shrinks and is replaced by fat, reducing the output of naive T-cells crucial for adaptive immunity. Consequently, older adults experience reduced vaccine efficacy and are more vulnerable to infections, as tragically highlighted during the COVID-19 pandemic. While the adaptive immune system develops memory, its ability to mount a robust response diminishes with age.

BIOMARKERS, AGING CLOCKS, AND FUTURE DIRECTIONS

The field of aging research is increasingly utilizing biomarkers and epigenetic clocks to assess biological age. While promising, these tools are still largely research-based and require significant validation before clinical use. Challenges include biological variability, the tenuous link between methylation sites and specific biological functions, and the potential for confounding factors like immune cell composition or pharmaceutical interventions. Emerging approaches, such as proteomic and organ-specific clocks, aim to provide more comprehensive and clinically relevant insights into an individual's aging trajectory.

Mentioned in This Episode

●Supplements

●Companies

●Organizations

●Concepts

●People Referenced

Common Questions

The central nervous system and the immune system are considered rate-limiting organs for aging. This is because both are distributed throughout the organism, and their systemic activity can influence the functioning of every other organ.

Topics

Rapamycin Sirtuins Aging Clocks Thymus

Mentioned in this video

personMartin Brand

A colleague of Eric's at the Buck Institute and a leader in bioenergetics, who identified sites of reactive oxygen species generation and developed specific inhibitors.

conceptInterleukin-11 (IL-11)

An inflammatory marker, blocking which has been shown to extend lifespan in mice. Inhibitors exist and could become part of anti-aging strategies.

personRalph DeFronzo

A world's authority on the gut's role in metabolism and GLP-1's role in beta cell activity.

conceptSirtuins

A class of proteins that rely on NAD+ as a substrate in DNA repair; their field of study is considered complex and still being clarified despite controversy.

personDan Belsky

Developer of the 'Dunedin Pace' epigenetic clock, which measures the rate of aging and appears to respond to interventions.

conceptCD38

A major driver of NAD+ decrease during aging, shown by Eduardo Chini's work. CD38 knockouts have stable NAD+ levels and live 15% longer.

conceptERCC1 DNA damage repair

A genetic mutation that, when knocked out in bone marrow of mice, induces accelerated aging and senescence in the whole organism.

supplementGLP-1 Agonists (e.g., Tirzepatide, Semaglutide)

Drugs predicted to emerge as geroprotectors due to their effects on glucose metabolism and satiety, noted for dramatically improving metabolic numbers in personal experimentation.

supplementUrolithin A

Used as an example of a supplement company that conducts rigorous clinical trials and publishes in top journals, in contrast to the NAD+ field.

personMorgan Levine

Researcher who, along with others like Dan Belsky, has contributed to the development of epigenetic aging clocks.

organizationBuck Institute for Research on Aging

The institution Eric now leads, where his lab focuses on epigenetics, immunology, and metabolism.

conceptMitochondrial dysfunction

Inducing this condition only in the immune system of mice leads to secondary senescence in the entire organism.

organizationIntervention Testing Program (ITP)

A program mentioned for identifying drugs targeting glucose metabolism that extend lifespan in mice.

personMatt Camberlin

Famously purchased and tested multiple commercially available aging clocks, finding significant disagreement between and within them. Also discussed his expertise on rapamycin.

supplementAcarbose

A drug that blocks glucose absorption, identified by the ITP as targeting glucose metabolism and extending lifespan.

personEduardo Chini

First to show that CD38 is the major driver of NAD+ decrease during aging, publishing that CD38 knockout mice do not experience this decline and live longer.

personMike McHugh

Colleague of Eric's at the Gladstone Institute, whose work on HIV patients inspired a trial for thymic regeneration using human growth hormone.

personLenny Guarente

Published a paper on sirtuins in yeast, paving the way for further research into sirtuins and NAD+.

personRich Miller

Speaker mentioned that Rich Miller has been a guest on the podcast several times, likely discussing the ITP.

personMark Davis

A collaborator at Stanford on the 10,000 Immunome Project, who co-developed 'I age' and studies aging in the human immune system.

companyTrue Diagnostic

A company that provides multiple epigenetic aging clocks (using the 'epic array'), which Eric uses to measure his own aging markers.

organizationJoslin Clinic

Where Eric first did a postdoc working on diabetes and metabolism after medical school.

conceptChronic Inflammation (Inflammaging)

A process induced by aging that itself accelerates aging, playing a central role in the aging process.

personSteve Austad

Coined the 'longevity quotient' concept, which highlights the correlation between animal size and lifespan.

conceptCD157

Another NAD+ hydrolase, less studied than CD38, also contributing to NAD+ metabolism.

diseaseHIV

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