Dr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics, Fasting & Protein Acetylation

TIMELINE... • 00:03:22 - How genetically inhibiting autophagy actually increases cellular sensitivity to death and how this was counterintuitive because autophagy was thought, at one time, as a type of activity predominantly concerned with actually initiating cell death. • 00:04:44 - The external signals causing autophagy. • 00:05:29 - The role of growth factors in transporting nutrients from the outside world into the intracellular space. • 00:05:48 - Autophagy as a process that destroys bioenergetic macromolecular reserves including proteins, lipids, and nucleic acids to generate energy. • 00:06:28 - How declines in the ATP (energetic) status of the cell trigger autophagy by increasing the activity of a pathway known as AMP Kinase. • 00:06:36 - How reductions in the cytosolic pool of acetyl-CoA as a consequence of reductions in glycolysis, amino acid catabolism, or beta-oxidation, ultimately result in the de-acetylation of hundreds of cellular proteins involved in autophagy. Nutrient deprivation → ↑ Protein Deacetylation (↓ cytosolic Acetyl CoA) + ↓ mTOR + ↑ AMP Kinase → Autophagy • 00:09:37 - The role of the inhibition of mTOR and activation of AMP Kinase in cellular autophagy. mTOR is a pathway robustly activated by IGF-1 and associated with increases in cell growth, proliferation, motility and protein synthesis. AMP Kinase, on the other hand, is a pathway important in regulating cellular energy homeostasis by inhibiting synthesis of fatty acids and triglycerides and activating fatty acid uptake and beta-oxidation in the liver. • 00:09:37 - The indirect relationship between protein acetylation status (and cytosolic acetyl CoA availability) and the suppression of mTOR and activation of AMP Kinase in cellular autophagy. • 00:10:23 - The possibility of using selective nutrient restriction as an autophagy-inducer instead of more generalized nutrient deprivation or fasting. • 00:11:11 - Cytoplasmic protein deacetylation as a potential surrogate marker for fasting-induced autophagy (still undergoing validation) but possibly not other forms of autophagy, such as the kind pharmacologically induced by interaction with a protein involved in vesicle-trafficking processes called Beclin 1. • 00:12:53 - How a protein called LC3 associate with structures called autophagosomes to facilitate autophagy in response to deacetylation it undergoes. Note: this sirt1-mediated deacetylation of LC3 is induced as an important response to cell starvation. • 00:14:22 - The special flow cytometry needed in order to measure some of the proteins associated with the activation of autophagosomes in autophagy. • 00:15:04 - The desirability of being able to know and test whether or not your fasting is triggering robust autophagy or not. • 00:16:30 - The minimum amount of fasting necessary to activate autophagy. • 00:16:56 - Whether or not time-restricted eating or 16:8 intermittent fasting reliably induces autophagy in any of our tissues. • 00:17:57 - The important differences between prolonged fasting in humans and the rodent animal models used in studies. • 00:19:03 - The ~12-hour half-life of IGF-1 and whether or not that has any implications for the potential of autophagy in shorter duration fasts. • 00:20:12 - The effects of long-term caloric restriction on markers of cellular autophagy in humans. • 00:21:32 - The effect of an every-other-day eating pattern in rodents and how this pattern actually mimics the longevity producing effects of caloric restriction but with the advantage of stabilizing long-term at a more normal body weight. (Note: Dr. Kroemer is quick to point out that this type of intermittent fasting is more dramatic than it would be in humans because of differences in metabolism… the animals actually experience a 10% oscillation in body weight from this pattern!) • 00:24:35 - The effect of exercise (especially endurance exercise) on autophagy in muscle tissue. • 00:25:08 - The role of autophagy as a mediator of the anti-obesity and anti-diabetic effects of endurance exercise. • 00:26:58 - The differences between macroautophagy, microautophagy, and chaperone-mediated autophagy. • 00:28:03 - The difference between autophagy that is dictated by demand (nutrient stress) versus autophagy that occurs as the need arises to recycle damaged organelles. • 00:28:40 - How damaged organelles change the composition of their surfaces in order to decorate them with signals for the stimulation of their engulfment by the autophagosome. • 00:29:07 - The many, many names autophagy has when we are talking about it in the context of specific macromolecular structures and organelles (e.g. mitophagy for mitochondria, pexophagy for peroxisomes, reticulophagy for endoplasmic reticulum, ribophagy for ribosomes, and virophagy for viruses). • 00:29:35 - How autophagy from nutrient deprivation still prefers to first recycle organelles that have been slightly marked… in other words, that are already aged or slightly damaged. • 00:31:15 - How mitochondrial use ubiquitination, a process which occurs when these organelles begin to lose their membrane potential, in order to signal damage and to ensure preferential targeting by the autophagic machinery. ↓ mitochondrial transmembrane potential → ↑ ubiquitination → ↑ mitophagy • 00:32:42 - The coordinated manner in which mitophagy and mitochondrial biogenesis act together in a closed feedback loop in order to preserve mitochondrial quality while preserving the total pool of functioning mitochondria. • 00:33:34 - The changes that can occur in total mitochondrial pool as cells adapt to take on new metabolic profiles through a mitophagy-mediated process. This can occur as cells differentiate into new cell types that are specialized for glycolytic energy generation. • 00:35:13 - The role autophagy plays in the prevention of neurodegenerative diseases caused by protein aggregates. • 00:37:18 - How autosomal recessive mutations (where both parents must contribute a defective gene for PD to arise in the offspring) in a kinase protein called PINK1 disrupts its ability to recruit a protein called Parkin that mediates the targeting of mitochondria for mitophagy. ↓ PINK1’s kinase activity → ↓ parkin recruitment → ↓ mitophagy → ↑ accumulation of damaged mitochondria • 00:38:01 - Mitochondrial membrane permeabilization as a death signal due to the release of dangerous proteins contained in the mitochondria. • 00:39:05 - Dr. Valter Longo’s research demonstrating a cycle of prolonged fasting followed by a refeeding can recycle 28% of the white blood cells, and reduce the severity of an autoimmune disease (multiple sclerosis). • 00:39:52 - The evolutionarily-conserved sickness response (food avoidance) as a way of beneficially altering immune responses through through altered metabolism and autophagy. • 00:41:02 - The surprising increase in lethality that happens when mice are force fed (glucose in this case) while exhibiting sickness response from a bacterial challenge. • 00:42:27 - The effects of an anti-malarial known as chloroquine which has some cytotoxic effects in cancer cells, but is actually (surprisingly) an inhibitor of autophagy. • 00:43:12 - Studies of the lysosomal disrupter and anti-malarial chloroquine in combination with chemotherapy in the treatment of cancer. • 00:44:04 - The differential roles autophagy plays in the progression of cancer in pre-malignant cells, when it is suppressed, versus in malignant cells, when it is sometimes used as an adaptation helpful to the survival of malignant cells experiencing environmental stress. ↓ tumor suppressor gene activity → ↓ autophagy → survival of pre-malignant cells → ↑ autophagy as a malignant adaptation • 00:44:49 - How inhibition of autophagy by itself is sufficient to induce oncogenesis, particularly in leukemia. • 00:48:10 - How cells undergoing autophagy can release ATP into the extracellular space where it can function as a signal that recruits and activates immune cells against tumor antigens through the activities of purinergic receptors. ↑ autophagy → ↑ extracellular ATP → activation of purinergic receptor-mediated immunosurveillance • 00:48:49 - The importance of the triggering of this immunosurveilance system as part of the cell death associated with chemotherapy. • 00:50:27 - The class of compounds known as “caloric restriction mimetics” that affect autophagy by perturbing various pathways in such a way as to reductions in cytosolic acetyl CoA and protein deacetylation in a manner similar to nutrient deprivation. Examples include: hydroxycitrate (inhibits ATP citrate lyase), spermidine (inhibits Ep300, a protein acetyltransferase), and resveratrol (activates deacetylases). • 00:55:27 - How intestinal bacteria may produce as much as 1/3rd of the body’s spermidine and how this production rate can be manipulated by probiotic and dietary interventions. • 00:56:17 - How the ability of caloric restriction mimetics (CRMs) to induce a type of autophagy that provokes immunosurveillance potentially offers an opportunity for synergy when used in combination with chemotherapeutic agents in the treatment of cancer. • 00:56:56 - How the inhibition of autophagy in malignant cells or destruction of the extracellular ATP released by cells undergoing autophagy is able to abolish the favorable interaction between caloric restriction mimetic drugs and chemotherapy. • 00:58:02 - The tendency for dietary consumption of caloric restriction mimetics, particularly hydroxy citrate, to induce autophagy and reduce weight gain in mice fed an obesogenic diet. • 00:59:17 - Dr. Kroemer’s personal intermittent and prolonged fasting practices and his habit of consuming foods that may contain some natural quantities of caloric restriction mimicking compounds. • 01:01:40 - The autophagy-enhancing effect of coffee (with and without caffeine).

I consider myself very fortunate to be living in an age when this type of information is so readily available to the common man.

How intelligent is this guy! Wow, a knockout interview. Also, I can tell you took the time to edit the closed captioning, which isn't easy or quick. Wanted to express my appreciation for that, because having captions on helps me concentrate and retain information. Thank you for producing all these high quality, informative videos.

I really appreciate your interview technique - you let the guest talk, and then summarize and help expand the guest's points. Thank you!

Rare to find a raw , unfiltered podcast that focuses on the science , without dumbing it down to pander to the audience. I didn't understand a lot of the cellular mechanisms entirely , but the numerous papers being cited, motivate me enough to find out. Dr Guido seems like on of the most knowledgeable persons I've seen on your podcast, its impressive to hear the breadth of his knowledge. P.S Spermidine in cheese in synergy with resveratrol in wine , would be interesting to see if this is a reason behind the French longevity paradox.

Fantastic interview, even more remarkable when you think that English is the second language from Dr Kroemer! He speaks better English than most of us native speakers. I find that the people with the most knowledge and intelligence are very calm and don't let their emotions get involved with their answers. I didn't understand everything he was talking about but bit by bit, I am getting very interested in fasting and autophagy. When a man like Dr.Kroemer is on OMAD plus prolonged fasting, not to mention wine and cheese! That is good enough for me Thanks and keep them coming!

That baby is gonna be immortal

If you watched this video, you qualify for 3 College credit hours.

Top 10, or even 5 here Rhonda, this was an exceptional interview! There is beauty in science, you know how to waltz with intellects and match them step for step. There were so many "connect the dots" moments for me in this one, I'm sharing it far and wide, and coming back for the encore. Bravo, and many thanks to Guido for coming on, he clearly appreciated your considerate, intelligent interview style. So grateful for your work, thank you.

The way Dr. Kroemer pronounces autophagy is borderline ASMR. I could listen to 9 more hours of this.

Nice job Dr. Patrick, your videos are getting better and better :) The extra multimedia inserts make these things so much easier to understand for the rest of us.

This was an excellent episode. What a brilliant mind, and a superb moderator/scientist asking all the right questions. Fascinating!

This guy is the real deal. He's got 'skills to pay the bills'.

This is one of the best interviews I've seen on this channel! Super comprehensive!!!!

Great video! Have been following you since I came across your lecture on hypothermic conditioning and epigenetic mechanisms. You have a great way of expressing information so it's easily understood. I have put your science into practice and have seen tremendous results at 39. Eating 1 meal a day for 7 months I've lost 45lbs and gained a whopping 18lbs of lean muscle mass. After around 18hrs my t levels and igf-1 literally go through the roof so it feels. I hope you read this because I really want express my gratitude for your work and helping people. Great work Dr Patrick!

The quality of information and how it's presented is ridiculously good! I'm learning more here than in my Cellular biology class at University.

This became my favorite youtube channel in less than 24h, the best ever! Big hello from East Europe!

Another excellent interview, Dr. Patrick. You maximized this opportunity! Thanks so much to both Docs, and soon I'll be supporting at Patreon.

Definitely watching this when I get out of work. Thank you Dr. Rhonda!!!

Wow ..that was an amazing interview. I think I'm going to have to listen a few more times to absorb all this great information.