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#09 - David Sabatini, M.D., Ph.D.: rapamycin and the discovery of mTOR — the nexus of aging and longevity?

Aug 13, 2018 1h 11m 13 insights
<p>In this episode, my good friend David Sabatini delves into his extensive work with the mechanistic target of rapamycin—better known as mTOR—and rapamycin. The compound rapamycin is the only known pharmacological agent to extend lifespan all the way from yeast to mammals—across a billion years of evolution. David, a professor of biology and a member of the Whitehead Institute at MIT, shares his remarkable journey and discovery of mTOR in mammalian cells and its central role in nutrient sensing and longevity. Fasting, rapamycin, mTOR, autophagy, gedankenexperiments: having this conversation with David is like being the proverbial kid in the world's greatest candy store.</p> <p>We discuss:</p> <ul> <li>mTOR and David's student years [4:30];</li> <li>Rapamycin and the discovery of mTOR [8:15];</li> <li>The connection between rapamycin, mTOR, and longevity [30:30];</li> <li>mTOR as the cell's general contractor [34:45];</li> <li>The effect of glucose, insulin, and amino acids on mTORC1 [42:50];</li> <li>Methionine sensing and restriction [49:45];</li> <li>An intermittent approach to rapamycin [54:30];</li> <li>Rapamycin's effects on cancer, cardiovascular disease, and neurodegeneration [57:00];</li> <li>Gedankenexperiment: couch potatoes on rapamycin vs perfectly behaved humans [1:03:15];</li> <li>David's dream experiment with no resource constraints [1:07:00]; and</li> <li>More.</li> </ul> <p> <span> Learn more at <a href="http://www.peterattiamd.com/"><span><u>www.PeterAttiaMD.com</u></span></a></span></p> <p> <span>Connect with Peter on <a href=""> <span> <u>Facebook</u></span></a> | <a href=""> <span> <u>Twitter</u></span></a> | <a href=""> <span> <u>Instagram</u></span></a>.</span></p>
Actionable Insights

1. Prioritize Anabolism-Catabolism Cycling

Recognize that cycling between anabolic and catabolic states is potentially the single most important factor for cellular health and longevity, as both too little and too much mTOR activity or autophagy can be toxic.

2. Intermittent Rapamycin Dosing

If considering rapamycin for longevity, an intermittent dosing approach is recommended to induce a relatively weak autophagy and allow the system to rebuild, aligning with the crucial principle of anabolism-catabolism cycling.

3. Consider Methionine Restriction

Explore methionine restriction as a dietary intervention for beneficial effects on glucose homeostasis and lifespan extension, as it significantly drops during fasting and its metabolite, SAM, directly inhibits the mTOR pathway when reduced.

4. Modulate mTOR for Systemic Rejuvenation

To broadly impact cellular state, rejuvenate cells, and slow aging, target mTOR because it acts as a ‘general contractor’ for the cell, influencing numerous processes simultaneously, which is more effective than targeting individual pathways.

5. Avoid Complete mTORC1 Inhibition

Do not completely inhibit mTORC1 as it is essential for the growth of normal cells; full inhibition would mimic a crude chemotherapeutic agent, leading to atrophy and cell death.

6. Leucine & Arginine Activate mTORC1

Understand that leucine (and to a lesser extent isoleucine, but not valine in their findings) and arginine directly activate mTORC1 by binding to intracellular receptors, signaling nutrient availability and driving anabolism.

7. mTOR Modulation Differs from Fasting

Be aware that while mTOR modulation can mimic some effects of fasting, systemic nutrient levels remain high, potentially leading to nutrient accumulation in cells, unlike actual fasting where nutrient levels are lower.

8. SAM May Counter Methionine Restriction

Be aware that the beneficial effects of methionine restriction, which work by reducing SAM and inhibiting mTOR, could potentially be bypassed or counteracted by supplementing with SAM (S-adenosylmethionine).

9. Glucose and Insulin Activate mTORC1

Recognize that both glucose and insulin activate mTORC1 through independent pathways, which aligns with its role as a nutrient sensor, signaling a fed state.

10. mTORC1 Senses Diverse Cellular States

Understand that mTORC1 activity is regulated by a wide array of cellular conditions, including nutrients, oxygen levels, pH, growth factors, and osmotic pressure, making it a central hub for cellular state sensing.

11. Integrate Local & Global Nutrient Signals

When assessing the body’s anabolic/catabolic state, consider both global signals (like insulin reflecting overall organismal fed state) and local signals (like specific nutrient availability within cells) as mTOR integrates both.

12. Rapamycin May Mitigate Cancer Growth

While rapamycin is an immunosuppressant, it appears to have direct anti-cancer effects that can mitigate the increased cancer risk from immune suppression, potentially by affecting the growth and immune evasion of existing cancer cells rather than preventing initial mutations.

13. Foster Independent Project Ownership

Allow individuals, especially students, complete freedom to pursue their own projects, as this can be a foundational experience for developing into an independent scientist or professional.