HoldsUp

Guido Kroemer

University of Paris Descartes

Guido Kroemer is a professor at the University of Paris Descartes specializing in immunology, cancer biology, aging, and autophagy. His research investigates mechanisms of regulated cell death, including apoptosis, ferroptosis, and immunogenic cell death. His publications also explore cancer immunotherapy, gut microbiota interventions in oncology, and therapeutic targets in metabolic and age-related diseases.

38 claims checked on air: 3 context 1 contradicted 2 overstated 28 supported 4 unverified 3 flagged

What they said on air

0:03:04supportedmoderateDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Specific genetic inhibition of autophagy sensitizes cells to the induction of cell death.

"inhibition of autophagy, which can only be achieved in a specific way by genetic tricks, will actually sensitize cells to cell death induction. And so this means that autophagy is a means of adaptation to stress and a technique of the cell to avoid cell death." (said at 0:03:04)

The statement accurately reflects the established biological consensus on the cytoprotective function of macroautophagy. In cellular biology, autophagy functions primarily as an adaptive response to metabolic or environmental stress, enabling cells to survive adverse conditions. Genetic suppression of essential autophagy-related (ATG) genes disables this adaptive mechanism, thereby sensitizing cells to stress-induced cell death rather than preventing it.

0:07:15unverifiedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Acetyltransferases have a low affinity for acetyl-CoA compared to kinases' affinity for ATP, making protein acetylation highly sensitive to fluctuations in acetyl-CoA levels whereas phosphorylation is relatively insensitive to ATP fluctuations.

"acetyltransferases are having a low affinity for acetyl-CoA as compared to kinases, which have a high affinity for ATP. So if you vary the ATP concentration in the cell, it has little impact on phosphorylation reactions. But if you vary acetyl concentration, it has a major impact on the acetylation level of cellular proteins." (said at 0:07:15)

No published record matching the claim that acetyltransferases have a lower affinity for acetyl-CoA compared to kinases' affinity for ATP—rendering protein acetylation sensitive to acetyl-CoA fluctuations while phosphorylation remains relatively insensitive to ATP fluctuations—was located; this does not prove the claim false.

0:07:59supportedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Depleting glucose, amino acids, or fatty acids lowers cytosolic acetyl-CoA levels, which causes cytosolic protein deacetylation and stimulates autophagy.

"taking away glucose or amino acids or fatty acids will cause a reduction in the acetyl-CoA pool, and which is important to note, it is the cytosolic acetyl-CoA pool that is accounting for autophagy regulation. And this reduction in acetyl-CoA in the cytosol will cause deacetylation at the end of cellular proteins, hundreds of different proteins, and hence a sort of multi-pronged induction of major subpathways of the autophagic process." (said at 0:07:59)

Preclinical studies in cell culture and mouse models demonstrate that nutrient deprivation (depleting metabolic substrates such as sugars, fats, and amino acids) reduces the cytosolic pool of acetyl-coenzyme A (AcCoA). Because cytosolic AcCoA acts as the primary acetyl donor for protein acetyltransferases, its depletion leads to widespread deacetylation of cytosolic proteins and consequent induction of autophagy.

0:09:18supportedmoderateDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Cellular deacetylation reactions trigger downstream inhibition of mTOR and activation of AMPK.

"As a side effect of deacetylation reactions, you usually also observe the inhibition of mTOR and the activation of AMPK kinase." (said at 0:09:18)

Preclinical and mechanistic evidence supports the assertion that cellular deacetylation events (predominantly mediated by sirtuin deacetylases such as SIRT1 and SIRT3) trigger AMPK activation and subsequent mTOR inhibition. Mechanistically, SIRT-mediated deacetylation of the upstream kinase LKB1 enhances its activity, leading to phosphorylation and activation of AMPK, which subsequently inhibits downstream mTOR complex 1 (mTORC1) signaling to promote autophagy and metabolic adaptation.

0:11:38supportedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

During complete caloric starvation, cytoplasmic protein deacetylation occurs across all major cell types throughout the body, except in the brain which is buffered against this effect.

"What we usually do is we starve mice and sometimes human volunteers completely from any kind of caloric uptake and in this case we do see at the whole body level that in all major cell types, perhaps with the exception of the brain that is somehow buffered against this effect, protein deacetylation occurs mostly in the cytoplasm." (said at 0:11:38)

Preclinical evidence demonstrates that nutrient depletion and starvation cause systemic depletion of cytosolic acetyl-CoA and induce widespread protein deacetylation—predominantly affecting the cytoplasm—across peripheral tissues (such as liver, heart, and skeletal muscle) to stimulate autophagy. Peripheral organs rapidly undergo autophagic flux and protein deacetylation in response to caloric deprivation, whereas the central nervous system is largely protected and metabolically buffered against acute starvation-induced changes. However, these mechanistic insights are derived primarily from animal models (rodents) and in vitro cell cultures, and evidence in humans remains preliminary.

0:11:53unverifiedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Autophagy can be pharmacologically induced via a cell-permeable Beclin-1-activating peptide or via mTOR inhibitors without inducing protein deacetylation.

"when you induce autophagy by pharmacological tricks such as a cell-permeable peptide that dissociates an inhibitory interaction between a Golgi protein and Beclin-1, you can induce autophagy without that protein deacetylation would occur before. And similarly, when you give chemical inhibitors of mTOR like rapamycin or the rapalogs, there's also no protein deacetylation." (said at 0:11:53)

No published record matching the claim that autophagy can be pharmacologically induced via a cell-permeable Beclin-1-activating peptide or via mTOR inhibitors without inducing protein deacetylation was located; this does not prove the claim false.

0:13:28supportedhighDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Autophagy in humans can be measured in circulating leukocytes by assessing the redistribution of LC3 from a diffuse cytosolic pattern to punctate autophagosomal dots using imaging cytofluorometry.

"So, we can draw blood and determine by immunofluorescence the redistribution of LC3 from a diffuse to a punctiform pattern. And this is then a sort of detection of autophagy that can be applied to human beings as well... there are cytofluorometers that take pictures of the cells that are flying in front of the detector and using these pictures and analyzing them by image analysis software allows them to quantitate the redistribution of LC3 to autophagosomes." (said at 0:13:28)

Multispectral imaging flow cytometry (imaging cytofluorometry) combined with image analysis algorithms is an established, validated technique for quantifying autophagy. It captures high-throughput imagery of individual cells in flow to quantify the translocation of diffuse cytosolic microtubule-associated protein 1A/1B-light chain 3 (LC3) into distinct punctate autophagosomes and autolysosomes, including in circulating leukocytes and peripheral blood mononuclear cells.

0:17:15supportedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Hepatic autophagy in mice fluctuates with circadian cycles, showing increased autophagy during the day when mice are not eating.

"E. Kate Thompson published a paper on circadian variations in hepatic autophagy. So, you know that mice don't eat during the day and they eat during the night. So, entire cycle is inversed and he observed that as a result of not eating during the day, there was more autophagy in the liver." (said at 0:17:15)

Hepatic autophagy in nocturnal rodents (such as mice and rats) exhibits a pronounced diurnal/circadian rhythm. Because nocturnal rodents feed primarily at night and rest/fast during the day, hepatic autophagy is robustly up-regulated during the daytime fasting period (nutrient limitation) and suppressed during nocturnal feeding. Disruption of circadian clock genes or alterations in meal timing directly shifts or abolishes this rhythmic induction of hepatic autophagy. Because this evidence is derived from animal physiology, the certainty is graded as very low for human extrapolation.

0:17:50unverifiedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

In humans, fasting for 3 to 4 days is required to observe robust induction of autophagy in circulating leukocytes.

"what we did on circulating leukocytes is that we needed to wait for 3 or 4 days to see massive induction of autophagy." (said at 0:17:50)

No published record matching the specific claim that 3 to 4 days of fasting is required to observe robust or massive induction of autophagy in human circulating leukocytes was located; this does not prove the claim false. While shorter-term fasting and exercise-induced fasting protocols have been studied for their effects on autophagic markers in human tissues and peripheral blood mononuclear cells, specific empirical publications defining a strict 3- to 4-day requirement for leukocyte autophagy induction were not identified in the indexed literature.

0:18:04needs contextmoderateDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Two days of fasting causes about a 20% loss of body weight in mice, whereas four days of fasting in humans causes only a 1% to 2% weight loss.

"The 2 days that you have been alluding to cause a 20% weight loss in mice that are at this time point at the verge of death... In 4 days, a human being only loses 1 to 2% of his or her weight." (said at 0:18:04)

The speaker's comparison illustrates the profound difference in mass-specific metabolic rate between rodents and humans during fasting, but underestimates the typical short-term weight loss in humans. In mice, a 48-hour total fast produces severe physiological stress and substantial weight loss (often approaching 15% to 20% of total body weight). However, in humans, a complete four-day fast typically results in a 3% to 6% reduction in body weight (approximately 2.5 to 4.5 kg in an average adult), driven primarily by acute glycogen depletion and obligate fluid loss alongside tissue catabolism, rather than merely 1% to 2%.

0:21:30overstatedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

In mice, alternate-day intermittent fasting extends lifespan to the same extent as 30% caloric restriction without resulting in a permanent reduction in body weight.

"in mice, you can obtain exactly the same longevity extension that you would obtain with 30% of caloric restriction by intermittent fasting... the intermittently fasted mouse has the same weight as a normally fed mouse. In difference with the calorically restricted mouse, it weighs also 20 to 30% less. And in spite of this difference in the body weight, intermittent fasting allows for lifetime expansion in the same way as does caloric restriction." (said at 0:21:30)

While some rodent studies have shown that alternate-day intermittent fasting can extend lifespan without reducing overall body weight due to compensatory hyperphagia on feeding days, this effect is highly conditional rather than universal. Preclinical research demonstrates that the impact of every-other-day feeding on body weight and longevity in mice is strongly dependent on genetic background, age of onset, and fasting regimen. In certain inbred strains (such as C57BL/6J), intermittent fasting does lead to significant body weight reduction, and large-scale assessments across genetically diverse mice demonstrate that continuous caloric restriction generally provides more robust lifespan extension than intermittent fasting regimens.

0:25:00supportedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

In mice, the anti-diabetic and anti-obesity effects of endurance exercise depend on the induction of autophagy.

"it is known that endurance training is particularly efficient in mice to induce autophagy and that it mediates anti-obesity and anti-diabetic effects that are depending in a way on autophagy induction. Because genetic modifications of the process that leads to autophagy induction, its inhibition specifically by exercise can prevent these anti-diabetic effects." (said at 0:25:00)

Animal research in mice supports the claim. A landmark 2012 study demonstrated that acute exercise induces autophagy in skeletal muscle, and genetically preventing exercise-induced autophagy (using BCL2 AAA knock-in mice that retain basal autophagy but cannot activate stimulus-induced autophagy) abolished the protective effects of chronic exercise training against high-fat-diet-induced glucose intolerance and insulin resistance. Because this evidence is derived from animal models, the GRADE certainty is very low.

0:31:19supportedhighDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

When a mitochondrion decreases its transmembrane potential due to suboptimal function, surface enzymes are activated that cause ubiquitylation and recruitment of autophagic adaptors for mitophagy.

"when a mitochondrion is suboptimal in its function, it will decrease its mitochondrial transmembrane potential. And this is a signal to activate enzymes on the surface of the mitochondria that cause ubiquitylation, recruitment of autophagic adaptors and leads at the end to autophagy because you offer the organelle, so the organelle in a way offers itself, it it proclaims its sacrifice by autophagy." (said at 0:31:19)

The speaker accurately describes the canonical PINK1/Parkin-dependent mitophagy pathway. A decrease or loss of mitochondrial transmembrane potential in damaged or dysfunctional mitochondria prevents the normal import and degradation of PINK1, leading to its accumulation on the outer mitochondrial membrane. PINK1 then activates the E3 ubiquitin ligase Parkin, which ubiquitylates outer mitochondrial membrane proteins. These ubiquitin chains subsequently serve as signals to recruit autophagy adaptors, targeting the damaged organelle for selective autophagic degradation.

0:32:52supportedlowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

In C. elegans, mitophagy and mitochondrial biogenesis are coupled to regulate overall mitochondrial turnover.

"in C. elegans, it is well studied that actually the whole turnover of mitochondria is regulated. So there's a sort of coupling between mitophagy and mitochondrial biogenesis." (said at 0:32:52)

Experimental research in Caenorhabditis elegans demonstrates that mitophagy and mitochondrial biogenesis are functionally coupled to regulate mitochondrial turnover and content. Studies show that mitophagy impairment triggers a SKN-1-mediated retrograde signaling pathway that concurrently regulates genes involved in both mitochondrial biogenesis and mitophagy (such as DCT-1), forming a homeostatic feedback loop that coordinates mitochondrial turnover. Certainty is graded as low because the evidence is derived from animal model basic science studies.

0:33:32contradictedhighDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Yeast cells placed in a glucose medium shift from oxidative phosphorylation to glycolysis by destroying most of their mitochondria through mitophagy.

"The easiest example is yeast that you suddenly place in a glucose-containing medium to allow for the fermentation of glucose in wine or beer production. So these yeast cells don't need much oxidative phosphorylation and they essentially rely during the process on glycolysis. So they adapt to this change by destroying most of their mitochondria by mitophagy." (said at 0:33:32)

The claim states that transferring yeast to a glucose-containing medium causes the cells to adapt by destroying most of their mitochondria through mitophagy. In Saccharomyces cerevisiae, high-glucose conditions actually repress and suppress mitophagy (for example, by maintaining low expression of the essential mitophagy receptor Atg32). Conversely, mitophagy is induced by glucose starvation, carbon depletion (such as ethanol depletion), or stationary phase growth, rather than by glucose exposure.

0:34:04supportedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Retinal ganglion cell differentiation during embryonic development and macrophage differentiation from M0 to M1 involve a metabolic transition to glycolysis coupled with mitophagy, and inhibiting mitophagy prevents differentiation in both cases.

"And you have similar examples in the embryonic development of the retina for retinal ganglion cells or the differentiation of macrophages from so-called M0 to M1 macrophages in which the cells change from oxidative phosphorylation, respiration to an essentially glycolytic metabolism that is coupled to mitophagy. And so inhibition of mitophagy actually avoids the differentiation process in both examples that I just gave to you." (said at 0:34:04)

The speaker accurately describes the findings of preclinical study in mouse models and cell cultures. During embryonic retinal ganglion cell (RGC) differentiation and M1 macrophage polarization, programmed NIX/BNIP3L-dependent mitophagy drives a metabolic transition from oxidative phosphorylation to glycolysis. Furthermore, pharmacological or genetic inhibition of mitophagy prevents differentiation in both cell types.

0:35:24supportedmoderateDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Most neurodegenerative diseases are caused by the accumulation of toxic protein aggregates resulting from either excessive unfolded protein production or deficiencies in autophagic and lysosomal machineries.

"most known neurodegenerative diseases are either caused by the aggregation of poorly built proteins that somehow create protein aggregates that are toxic for the cell. Or they can also be caused by subtle deficiencies in the autophagic and lysosomal machineries that lead to the accumulation of unfolded proteins at the end. And so either the excessive production of unfolded proteins or their reduced removal causes a slow accumulation of these toxic protein aggregates." (said at 0:35:24)

The speaker's statement accurately reflects the widely accepted proteostasis framework in neurodegenerative disease pathology. Major neurodegenerative disorders—including Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis (ALS)—are characterized by the toxic accumulation of misfolded protein aggregates. This accumulation arises from an imbalance in cellular protein homeostasis (proteostasis), driven either by increased production/misfolding of aberrant proteins or by defects and age-related declines in clearance pathways, particularly the autophagy-lysosomal system (aggrephagy) and the ubiquitin-proteasome system.

0:37:29supportedhighDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

The PINK/Parkin pathway marks damaged mitochondria for destruction, and inhibiting this pathway leads to the accumulation of dysfunctional mitochondria, reactive oxygen species production, and apoptotic trigger potential.

"the PINK/Parkin pathway is one pathway among others that allows for marking mitochondria that are damaged for destruction. And so inhibition of this pathway leads to the accumulation of malfunctioning mitochondria with major consequences for the cell that harbors those mitochondria because all of a sudden, bioenergetic metabolism becomes inefficient. Reactive oxygen species are produced and as you know, mitochondria are latent bombs in the sense that they enclose potentially dangerous proteins that once released will activate the apoptotic machinery and cause cellular suicide." (said at 0:37:29)

The speaker's description accurately reflects the established biological consensus regarding the PINK1/Parkin-mediated mitophagy pathway. PINK1 (PTEN-induced kinase 1) and Parkin (an E3 ubiquitin ligase) operate as a core mitochondrial quality control mechanism that identifies damaged or depolarized mitochondria and targets them for selective autophagic degradation (mitophagy). When this pathway is inhibited or defective, damaged mitochondria fail to be eliminated, resulting in impaired bioenergetics, accumulation of reactive oxygen species (ROS), and permeabilization/release of mitochondrial proteins (such as cytochrome c) that activate the intrinsic apoptotic pathway.

0:39:06supportedlowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Valter Longo's research showed that mice undergoing 48-hour fasts experienced destruction of 50% to 75% of their leukocytes, which could be regenerated in a few days.

"what Valter has been observing, if I remember well, is destruction of leukocytes, white blood cells, which are very easily to be rebuilt. And so the the loss of 50% or 75% of leukocytes can be easily repaired in a few days." (said at 0:39:06)

Research led by Valter Longo demonstrated that prolonged fasting (48 hours in mouse models) leads to a reduction in circulating immune cells and triggers hematopoietic stem cell (HSC) self-renewal and immune system regeneration upon refeeding. Because the finding is based primarily on preclinical mouse models and preliminary patient data, the overall level of evidence certainty is low.

0:40:39supportedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Ruslan Medzhitov published a Cell study showing that force-feeding mice or restoring glucose levels to normal concentrations made an otherwise survivable bacterial infection lethal.

"Ruslan Medzhitov published a paper in Cell last year showing that force-feeding mice, or just increasing the glucose levels to a normal concentration, was sufficient to make bacterial infection that otherwise would have been able to cope with lethal." (said at 0:40:39)

A 2016 study published in Cell by Ruslan Medzhitov and colleagues demonstrated that infection-induced anorexia is protective in mouse models of bacterial inflammation (Listeria monocytogenes and LPS-induced sepsis). Providing nutritional supplementation (gavage feeding) or supplementing with glucose alone was sufficient to convert a sublethal, survivable bacterial challenge into a lethal infection, whereas blocking glucose utilization with 2-deoxy-D-glucose (2DG) protected against bacterial mortality. Because the evidence is derived entirely from animal models, the certainty of evidence for human clinical implications is very low.

0:42:38supportedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Chloroquine specifically enriches in lysosomal membranes due to its charge, causing lysosomal membrane damage and releasing toxic lysosomal contents into the cytosol rather than acting solely by inhibiting autophagy.

"chloroquine is a lysosomal inhibitor. It's a molecule that, due to its charge, will specifically enrich in the membranes of lysosomes, and then causes lysosomal membrane damage, potentially also inhibition of autophagy, but fundamentally also liberates the potentially toxic content of lysosomes into the cytosolic space. And so, there are a few reports around, showing that inhibition of autophagy is not the sole mechanism by which chloroquine can mediate cytotoxic effects." (said at 0:42:38)

Published preclinical mechanistic studies support the claim. Chloroquine is a lysosomotropic, weak-base compound that accumulates in acidic compartments like lysosomes, causing lysosomal membrane destabilization and permeabilization (LMP). This triggers the leakage of toxic lysosomal contents (such as cathepsins) into the cytosol, inducing cell death pathways independently of autophagy inhibition. The GRADE certainty is very low because the evidence is derived entirely from in vitro and preclinical mechanistic models.

0:43:33supportedmoderateDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Clinical trials testing chloroquine or hydroxychloroquine combined with chemotherapy or radiotherapy to treat cancer have not produced convincing results.

"chloroquine and hydroxychloroquine, which are antimalaria agents that have been used for a long period, and also actually used for the treatment of rheumatoid arthritis because they have anti-inflammatory properties, are only introduced into clinical trials, mostly in combination with chemotherapy or radiotherapy to treat cancer. And those clinical trials so far are not convincing." (said at 0:43:33)

Published systematic reviews and oncology evaluations confirm that clinical trials evaluating chloroquine and hydroxychloroquine (as repurposed autophagy inhibitors) combined with chemotherapy or radiotherapy have produced mixed, modest, and generally inconclusive results. While preliminary trials have shown modest signals in specific small subgroups, they have lacked definitive clinical efficacy, prompting ongoing efforts to develop more potent and selective next-generation autophagy inhibitors.

0:43:33supportedhighDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Chloroquine and hydroxychloroquine are antimalarial agents that are used to treat rheumatoid arthritis due to their anti-inflammatory properties.

"chloroquine and hydroxychloroquine, which are antimalaria agents that have been used for a long period, and also actually used for the treatment of rheumatoid arthritis because they have anti-inflammatory properties" (said at 0:43:33)

Chloroquine and hydroxychloroquine were originally developed as antimalarial drugs and have been used for decades as conventional synthetic disease-modifying antirheumatic drugs (DMARDs) to treat autoimmune conditions, including rheumatoid arthritis and systemic lupus erythematosus. Their clinical utility in these diseases is attributed to their immunomodulatory and anti-inflammatory mechanisms, such as increasing lysosomal pH, inhibiting antigen presentation, and suppressing inflammatory cytokine production.

0:44:24supportedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Inhibition of autophagy during early oncogenesis promotes genomic instability and malignant transformation, and direct inhibition of autophagy is sufficient to cause oncogenesis, particularly in leukemia.

"it is part of the process that leads to cellular transformation because autophagy is a homeostatic mechanism that, if inhibited, favors genomic instability and malignant transformation of the cells. So, there are examples in the literature also that direct inhibition of autophagy is sufficient to cause oncogenesis, in particular in the context of leukemia." (said at 0:44:24)

Preclinical animal research supports the claim that loss or inhibition of basal autophagy promotes DNA damage, genomic instability, and neoplastic transformation, particularly in the hematopoietic system. In mouse models, conditional deletion of the core autophagy gene Atg7 in adult hematopoietic stem and progenitor cells leads to reactive oxygen species accumulation, elevated DNA damage, severe myeloproliferation, and premature lethality, demonstrating that functional autophagy is required to prevent malignant hematopoietic transformation.

0:46:35supportedmoderateDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Autophagy is required for stressed cancer cells to release extracellular ATP as a danger signal that attracts myeloid cells via purinergic receptors to initiate an anti-cancer immune response.

"Autophagy, for instance, is required for stressed cells to release ATP into the microenvironment. ... And ATP, when it appears all of a sudden outside of the cell, is considered as non-physiological. It is a danger signal. It is perceived by so-called purinergic receptors that are present, among other cell types, on leukocytes, in particular myeloid cells. And a cell that undergoes autophagy may, especially when this occurs before cell death, release ATP to attract myeloid cells into its proximity and to start an immune response against tumor antigens in the context of the initial oncogenic events." (said at 0:46:35)

Preclinical and mechanistic evidence directly supports the speaker's statement. Autophagy is required for stressed and dying cancer cells to release extracellular ATP, which serves as a danger-associated molecular pattern (DAMP). Extracellular ATP engages purinergic receptors (such as P2Y2 and P2X7) on myeloid cells—including dendritic cell precursors and macrophages—recruiting them to the tumor microenvironment to process tumor antigens and drive an adaptive antitumor immune response.

0:48:21overstatedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Long-term clinical efficacy of chemotherapy depends on inducing cancer cell death that elicits an anti-cancer immune response via autophagy induction.

"chemotherapy must provoke this cell death in a way that it later leads to an immune response. And so, if you have a long-term effect of chemotherapy for years or decades, that continues beyond removal of the drug. It is due to an anti-cancer immune response. And so, since this is so important, the capacity of the chemotherapeutic agent to induce autophagy is actually required for the long-term efficacy of the treatment." (said at 0:48:21)

The speaker generalizes findings from the immunogenic cell death (ICD) paradigm to all long-term chemotherapy efficacy. Preclinical studies in mouse models and cancer cell lines (such as those by Michaud et al., 2011, 2012) established that certain chemotherapeutics (e.g., anthracyclines, oxaliplatin) require premortem autophagy to release ATP, recruit dendritic cells and T cells, and achieve durable immune-mediated tumor control. However, asserting that any long-term remission lasting years or decades from chemotherapy is universally dependent on autophagy induction overstates the evidence. Chemotherapeutic agents possess diverse mechanisms of cytotoxicity (e.g., direct DNA damage, mitotic arrest, cellular senescence) that can eliminate tumor clones without ICD, and autophagy in many clinical contexts can conversely promote chemoresistance and tumor survival rather than antitumor immunity.

0:51:41supportedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

ATP citrate lyase is the primary enzyme generating the cytosolic acetyl-CoA pool, and hydroxycitrate inhibits it, causing acetyl-CoA depletion, deacetylation, and autophagy.

"The enzyme that generates acetyl-CoA in our cells, the most important one for the cytosolic pool, is ATP citrate lyase, and hydroxycitrate or pharmacological compounds that inhibit this enzyme cause acetyl-CoA depletion, deacetylation, and autophagy." (said at 0:51:41)

Preclinical and biochemical studies demonstrate that ATP citrate lyase (ACLY) is a central enzyme generating the nucleo-cytosolic acetyl-CoA pool. Pharmacological inhibition of ACLY using compounds such as hydroxycitrate (a competitive inhibitor of ACLY) leads to cytosolic acetyl-CoA depletion, a concomitant reduction in the acetylation of cellular proteins, and the induction of autophagy in cultured human cells and rodent models. Because the evidence supporting this specific mechanistic cascade is derived from in vitro and animal models, the certainty is rated very low.

0:52:02supportedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Spermidine and C646 induce autophagy and protein deacetylation by specifically inhibiting the protein acetyltransferase EP300.

"inhibiting the uh protein acetyltransferases. Uh Some of them have been identified like EP300, which appears extremely important for autophagy regulation. Uh and specific inhibitors of EP300 such as spermidine, a natural compound, or C646, which is a pharmacological compound specifically designed for this function. They can also cause deacetylation and autophagy." (said at 0:52:02)

Preclinical cell culture and in vitro biochemical research demonstrates that EP300 (E1A-binding protein p300) acts as an endogenous repressor of autophagy, and that both the natural polyamine spermidine and the synthetic pharmacological inhibitor C646 inhibit EP300 acetyltransferase activity, leading to protein deacetylation and activation of autophagic flux. Because this evidence comes entirely from in vitro biochemical assays and cell culture models, the certainty level is graded as very low.

0:52:27supportedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Resveratrol induces autophagy by activating protein deacetylases that remove acetyl groups from proteins, leading to hypoacetylation.

"And finally, it is possible to activate deacetylases or enzymes that remove acetyl groups from proteins and cause hypoacetylation and autophagy. And one example that is well known is resveratrol contained in red wine uh that uh induces autophagy through this pathway." (said at 0:52:27)

Preclinical and cellular evidence supports the claim that resveratrol induces autophagy by activating the protein deacetylase Sirtuin 1 (SIRT1), leading to protein hypoacetylation. Because this mechanistic pathway has been demonstrated primarily in cell cultures and model organisms rather than human clinical trials, the certainty of evidence is very low.

0:53:58supportedhighDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Spermidine is naturally present in the nuclei or nucleoids of all cellular organisms, including bacteria, yeast, plant, and animal cells.

"spermidine, to come to the source of spermidine, is contained in the nuclei of all kind of cells. So, in the nucleoid of bacteria, but also in the nuclei from yeast cells or from uh plant cells or animal cells. So, all uh food items that contain uh nucleated cells actually contain spermidine." (said at 0:53:58)

Spermidine is a ubiquitous, naturally occurring aliphatic polyamine present across all cellular life, including bacteria, fungi/yeast, plants, and animals. Due to its polycationic nature at physiological pH, it binds strongly to negatively charged nucleic acids in the cell nucleus (or bacterial nucleoid) and is involved in chromatin organization, transcription, translation, and cellular homeostasis. Consequently, whole foods composed of intact cellular material inherently contain spermidine.

0:54:50supportedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Oral administration of spermidine via food or drinking water is sufficient to induce autophagy in mice without requiring fasting or caloric restriction.

"So, spermidine uh has uh the capacity to induce autophagy uh when it is taken up uh with food or with the drinking water when we treat mice." (said at 0:54:50)

Preclinical research in mice supports the claim that oral administration of spermidine via food or drinking water induces autophagy. In a controlled animal study, oral spermidine supplementation in mice was shown to enhance cardiac autophagy, mitophagy, and mitochondrial function, resulting in extended lifespan and cardioprotective effects.

0:55:17needs contextlowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Approximately one-third of the spermidine in the human body is produced by the intestinal microbiota.

"it is produced by our microbiota. So, 1/3 of the spermidine in our bodies is probably produced in the intestine." (said at 0:55:17)

The body's pool of polyamines, including spermidine, is derived from three primary pathways: endogenous (de novo cellular) synthesis, dietary intake, and production by the gut microbiota. Attributing roughly one-third of the body's supply to intestinal microbial synthesis represents a common conceptual approximation among these three sources, though exact individual contributions vary and are challenging to quantify precisely in humans.

0:55:34supportedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

A Japanese research group published findings showing that specific gut bacteria overproducing polyamines reduce colon cancer development and aging.

"there's a Japanese group that has been publishing that specific bacteria overproducing polyamines can be used to uh reduce the development of colon cancer or to uh reduce aging." (said at 0:55:34)

A Japanese research group (led by Mitsuharu Matsumoto and colleagues) published studies demonstrating that administration of the probiotic strain Bifidobacterium animalis subsp. lactis LKM512—which upregulates intestinal polyamine production—extended lifespan, suppressed colonic senescence and inflammation, and reduced tumor incidence in aging mice. Because this research is restricted to rodent models, clinical efficacy in humans remains unestablished.

0:56:33supportedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Combining caloric restriction mimetics like spermidine, hydroxycitrate, or resveratrol with chemotherapy enhances the anti-cancer immune response, and this benefit is lost if malignant cell autophagy is inhibited, extracellular ATP is destroyed, or T cells are removed.

"when you combine chemotherapy with caloric restriction mimetics, all the caloric restriction mimetics that I mentioned including spermidine and uh uh hydroxycitrate and resveratrol will enhance the anti-cancer immune response that makes the uh therapy durable. So, uh the we have been able to show that inhibition of autophagy in the malignant cells or destruction of the extracellular ATP that is released as a result of autophagy is sufficient to abolish the favorable interaction between caloric restriction mimetics and chemotherapy. And similarly, actually, it is sufficient to uh remove T cells from the system and you will uh um lose any kind of tumor growth reduction induced by chemotherapy combined with caloric restriction mimetics" (said at 0:56:33)

The speaker accurately describes published preclinical research from their laboratory investigating caloric restriction mimetics (CRMs) such as spermidine and hydroxycitrate in combination with chemotherapy in mouse models. In these studies, combining CRMs with immunogenic chemotherapy enhanced antitumor immune responses and tumor growth inhibition. This therapeutic benefit was demonstrated to be dependent on tumor-cell autophagy, the preservation of extracellular ATP release, and the presence of functional T lymphocytes, with the combination effect being lost in autophagy-deficient tumors or immunocompromised/T-cell-deficient mice. Because the supporting evidence is currently limited to preclinical animal models and in vitro experiments, the certainty of evidence for clinical human efficacy is rated as very low.

0:58:43supportedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Administering spermidine to mice fed a high-fat diet reduces weight gain.

"And in mice you actually can give uh a combination of high-fat diet that usually would cause obesity with spermidine to uh reduce weight gain through mechanisms that we don't understand and that we believe to be autophagy-dependent" (said at 0:58:43)

Animal studies demonstrate that oral administration of spermidine reduces weight gain, insulin resistance, and obesity-related metabolic alterations in mice fed a high-fat or hypercaloric diet. Research evaluating the role of autophagy indicates that pharmacological stimulation of autophagy using spermidine helps counteract diet-induced weight gain. Because evidence for this effect is limited to preclinical animal models, the certainty is rated as very low.

0:59:51unverifiedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Combining an acetyltransferase inhibitor and a deacetylase activator produces a synergistic effect on autophagy in mice.

"inhibiting the acetyltransferase and activating the deacetylase will have, of course, a synergistic effect. ... Well, you can show this in mice" (said at 0:59:51)

No published record matching the claim that combining an acetyltransferase inhibitor and a deacetylase activator produces a synergistic effect on autophagy in mice was located; this does not prove the claim false.

1:01:44supportedvery lowDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Administering caffeinated or decaffeinated coffee continuously to mice via drinking water induces autophagy in a caffeine-independent manner driven by polyphenols.

"Yes, we published a study in mice um uh giving them a non-toxic dose of caffeinated or decaffeinated coffee with the drinking water uh continuously, and we could show that this was magnificently inducing autophagy." (said at 1:01:44)

A 2014 study from the speaker's research group evaluated the effects of caffeinated and decaffeinated coffee administered to mice and demonstrated that both formulations rapidly induced autophagy in multiple organs (liver, muscle, and heart) in vivo within 1 to 4 hours, accompanied by mTORC1 inhibition and broad protein deacetylation. Because the findings derive entirely from preclinical animal models, the certainty of evidence regarding human physiology is graded as very low.

1:02:14needs contextmoderateDr. Guido Kroemer on Autophagy, Caloric Restriction Mimetics

Heavy coffee consumption is epidemiologically associated with a reduced risk of cardiovascular and neurodegenerative diseases.

"Well, coffee use has been linked to major uh health-promoting effects. So, uh most cardiovascular and neurodegenerative diseases are actually reduced in heavy coffee drinkers as an independent link between lifestyle and pathology." (said at 1:02:14)

Epidemiological studies and umbrella reviews consistently show that coffee consumption is associated with a lower risk of cardiovascular disease (CVD), cardiovascular mortality, and certain neurodegenerative diseases (particularly Parkinson's disease). However, the dose-response relationship differs by outcome: for cardiovascular disease, the relationship is non-linear (U-shaped), with the largest risk reductions observed at moderate intake (3 to 5 cups per day) and attenuated risk reduction among heavy drinkers. In contrast, inverse associations for neurodegenerative outcomes like Parkinson's disease show a more linear, dose-dependent decrease in risk. Additionally, because the evidence is observational, these associations reflect epidemiological correlations rather than established causation.

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