Description: <b>Caloric restriction mimetics (CRMs)</b><br>
<br>
Examples of the most studied CRM and their anti-cancer effects include metformin, rapamycin, aspirin, and resveratrol and its by-products.<br>
<p><b>Calorie Restriction Mimetics</b> — Calorie restriction mimetics (CRMs) are a mechanistic class of compounds intended to reproduce selected biochemical effects of caloric restriction without requiring sustained energy restriction. They are best viewed as a research/therapeutic concept rather than a single drug entity or a formally approved regulatory class. Standard abbreviation: CRM or CRMs. In the oncology literature, the most commonly cited CRMs are metformin, rapamycin or rapalogs, aspirin or salicylate, resveratrol, spermidine, and hydroxycitrate; broader candidate lists often also include EP300-inhibitory or sirtuin-linked dietary compounds such as curcumin, garcinol, anacardic acid, EGCG, and some synthetic sirtuin activators. Their shared functional identity is partial imitation of nutrient-deprivation signaling, especially autophagy induction, lowered protein acetylation, AMPK-SIRT engagement, and relative suppression of anabolic growth signaling. In practice, however, CRM biology is highly heterogeneous, agent-specific, and often limited by pharmacokinetics, dose ceilings, or context-dependent tumor effects.</p>
<p><b>Primary mechanisms (ranked):</b></p>
<ol>
<li>Autophagy induction and proteostasis remodeling, often via reduced cytosolic acetyl-CoA signaling and lower global protein acetylation</li>
<li>AMPK activation with downstream suppression of PI3K-AKT-mTOR growth signaling and reduced anabolic drive</li>
<li>EP300 acetyltransferase inhibition or functional opposition, promoting deacetylation-linked fasting-like signaling</li>
<li>Sirtuin-linked stress adaptation and mitochondrial remodeling, especially with resveratrol-like or NAD-related CRM candidates</li>
<li>Systemic insulin-glucose-IGF axis attenuation, reducing nutrient availability and mitogenic support for susceptible tumors</li>
<li>Immune-context effects, including improved chemotherapy responsiveness and, in some models, enhanced anticancer immunosurveillance</li>
<li>Secondary anti-inflammatory and HIF-1α-glycolysis dampening effects in subsets of CRMs</li>
</ol>
<p><b>Bioavailability / PK relevance:</b> PK is not class-uniform. Metformin is orally available but hydrophilic and tissue-distribution dependent; rapamycin is orally active but shows variable exposure and clinically important immunosuppressive toxicity; aspirin is systemically available but dose-limited by bleeding risk; resveratrol has poor oral bioavailability and rapid metabolism; spermidine supplementation can show only modest increases in circulating polyamines because of strong homeostatic control. Many “dietary CRM” candidates therefore have more convincing mechanistic than translational PK support.</p>
<p><b>In-vitro vs systemic exposure relevance:</b> This is a major translation issue for the class. Many in-vitro CRM studies use concentrations that are not cleanly achievable in human plasma or tumors, especially for metformin and several polyphenols such as resveratrol. Accordingly, class-level conclusions should prioritize pathway directionality and combination/adjunct effects over direct cytotoxicity observed at high in-vitro doses.</p>
<p><b>Clinical evidence status:</b> Mixed and agent-dependent. For cancer, CRM evidence is strongest at the preclinical and adjunct-mechanistic level. Human data exist mainly for individual agents such as metformin, aspirin, and rapalogs rather than for “CRMs” as a validated class, and results remain heterogeneous across tumor types and trial designs. At present, CRMs are better regarded as a translational framework and combination strategy than as an established standalone oncology therapy category.</p>
<h3>CRM Product/Priority Table</h3>
<table border="1" cellpadding="4" cellspacing="0">
<tr>
<th>Tier</th>
<th>Priority</th>
<th>Agent</th>
<th>CRM Strength</th>
<th>Main Rationale</th>
<th>Comments</th>
</tr>
<tr>
<td>1</td>
<td>1</td>
<td><a href="https://nestronics.ca/dbx/tbResList.php?qv=386">Spermidine</a></td>
<td>Very strong</td>
<td>Among the cleanest strict CRMs; promotes autophagy and opposes protein acetylation through EP300-related mechanisms</td>
<td>Best fit for a mechanistically strict CRM</td>
</tr>
<tr>
<td>1</td>
<td>2</td>
<td><a href="https://nestronics.ca/dbx/tbResList.php?qv=96">Hydroxycitrate</a></td>
<td>Very strong</td>
<td>Strong strict CRM; reduces acetyl-CoA availability, lowers protein acetylation, and induces autophagy</td>
<td>Also has notable anticancer adjunct evidence</td>
</tr>
<tr>
<td>1</td>
<td>3</td>
<td><a href="https://nestronics.ca/dbx/tbResList.php?qv=1">Aspirin</a>/ salicylate</td>
<td>Strong</td>
<td>Can inhibit EP300 and induce fasting-like autophagy signaling</td>
<td>Good translational relevance compared with many dietary CRMs</td>
</tr>
<tr>
<td>2</td>
<td>4</td>
<td><a href="https://nestronics.ca/dbx/tbResList.php?qv=11">Metformin</a></td>
<td>Strong but indirect</td>
<td>Major CRM-associated drug due to AMPK activation, reduced anabolic signaling, and host metabolic effects</td>
<td>Important in oncology, though less strict mechanistically than tier 1</td>
</tr>
<tr>
<td>2</td>
<td>5</td>
<td>Rapamycin / rapalogs</td>
<td>Strong but indirect</td>
<td>Suppresses mTOR and reproduces part of the nutrient-deprivation program</td>
<td>Highly important, but more targeted than classic acetylation-centered CRMs</td>
</tr>
<tr>
<td>2</td>
<td>6</td>
<td><a href="https://nestronics.ca/dbx/tbResList.php?qv=141">Resveratrol</a></td>
<td>Moderate to strong</td>
<td>Historically prominent due to SIRT1-linked and autophagy-related fasting-like signaling</td>
<td>Limited by weak pharmacokinetics and broader mechanistic ambiguity</td>
</tr>
<tr>
<td>3</td>
<td>7</td>
<td><a href="https://nestronics.ca/dbx/tbResList.php?qv=73">EGCG</a></td>
<td>Moderate</td>
<td>Often included as a putative CRM because it can affect acetyltransferase activity and autophagy-related signaling</td>
<td>Less central than higher-tier agents</td>
</tr>
<tr>
<td>3</td>
<td>8</td>
<td><a href="https://nestronics.ca/dbx/tbResList.php?qv=65">Curcumin</a></td>
<td>Moderate</td>
<td>Frequently listed as a CRM-like dietary compound through acetylation and autophagy-related effects</td>
<td>Not a class-defining CRM</td>
</tr>
<tr>
<td>3</td>
<td>9</td>
<td><a href="https://nestronics.ca/dbx/tbResList.php?qv=83">Garcinol</a></td>
<td>Moderate</td>
<td>Mechanistically interesting EP300-related candidate</td>
<td>Mostly preclinical and less developed clinically</td>
</tr>
<tr>
<td>3</td>
<td>10</td>
<td>Anacardic acid</td>
<td>Moderate</td>
<td>Acetyltransferase-inhibitory CRM candidate</td>
<td>Mainly mechanistic and preclinical</td>
</tr>
<tr>
<td>4</td>
<td>11</td>
<td>Acarbose</td>
<td>Plausible but broad</td>
<td>Blunts postprandial glucose and nutrient signaling</td>
<td>More of a systemic metabolic mimic than a strict autophagy-centered CRM</td>
</tr>
<tr>
<td>4</td>
<td>12</td>
<td>Glucosamine</td>
<td>Plausible but weak</td>
<td>Sometimes classified as a CRM-like metabolic agent</td>
<td>Cancer-specific relevance is much weaker</td>
</tr>
<tr>
<td>4</td>
<td>13</td>
<td><a href="https://nestronics.ca/dbx/tbResList.php?qv=268">Nicotinamide </a>/ nicotinamide riboside / other NAD-linked agents</td>
<td>Debatable</td>
<td>Occasionally placed in broad CRM lists</td>
<td>Less standardized as oncology CRMs</td>
</tr>
</table>
<h3>Mechanistic Pathway Table</h3>
<table border="1" cellpadding="4" cellspacing="0">
<tr>
<th>Rank</th>
<th>Pathway / Axis</th>
<th>Cancer Cells</th>
<th>Normal Cells</th>
<th>Primary Effect</th>
<th>Notes / Interpretation</th>
</tr>
<tr>
<td>1</td>
<td>Autophagy induction</td>
<td>↑ autophagic flux; may reduce growth fitness, stress tolerance mismatch, or therapy resistance</td>
<td>↑ stress adaptation, proteostasis, organelle quality control</td>
<td>Core fasting-like reprogramming</td>
<td>This is the most coherent class-defining mechanism across stricter CRMs. In cancer, benefit is context-dependent because autophagy can also support survival in some settings.</td>
</tr>
<tr>
<td>2</td>
<td>AMPK activation</td>
<td>↑ energy stress signaling; proliferation programs ↓</td>
<td>↑ metabolic efficiency and adaptive stress signaling</td>
<td>Nutrient-sensing reset</td>
<td>Especially relevant for metformin-like CRMs; often linked secondarily to mTOR suppression and lower biosynthetic drive.</td>
</tr>
<tr>
<td>3</td>
<td>mTORC1 anabolic signaling</td>
<td>↓ protein synthesis, cell growth, and proliferation</td>
<td>↓ excessive anabolism; may support maintenance programs</td>
<td>Antiproliferative restraint</td>
<td>Rapamycin and rapalogs act most directly here. This axis has strong industry relevance because it is already druggable and clinically validated in oncology for specific agents.</td>
</tr>
<tr>
<td>4</td>
<td>EP300 acetyltransferase and protein acetylation</td>
<td>↓ protein acetylation; fasting-like deacetylation programs ↑</td>
<td>↓ acetylation tone; autophagy competence ↑</td>
<td>Autophagy-permissive deacetylation</td>
<td>Hydroxycitrate acts upstream through acetyl-CoA depletion; spermidine and salicylate can oppose EP300 activity more directly. This is a key stricter CRM-defining axis.</td>
</tr>
<tr>
<td>5</td>
<td>Acetyl-CoA supply and citrate-ACLY axis</td>
<td>↓ lipogenic and acetylation-supportive substrate availability</td>
<td>↓ anabolic surplus signaling</td>
<td>Metabolic substrate restriction</td>
<td>Most class-relevant for hydroxycitrate-like CRMs. Mechanistically central in strict CRM literature, but less clinically deployed than AMPK-mTOR agents.</td>
</tr>
<tr>
<td>6</td>
<td>Sirtuin signaling and NAD-linked stress adaptation</td>
<td>↑ stress-response remodeling; growth signaling ↓ (context-dependent)</td>
<td>↑ mitochondrial maintenance and stress resilience</td>
<td>CR-like adaptive signaling</td>
<td>Most associated with resveratrol and synthetic sirtuin activators. Mechanistically plausible, but human translational strength is weaker than for metformin or rapamycin.</td>
</tr>
<tr>
<td>7</td>
<td>Insulin glucose IGF signaling</td>
<td>↓ nutrient-driven mitogenic support</td>
<td>Improved insulin sensitivity and metabolic control</td>
<td>Systemic host-level antitumor pressure</td>
<td>Important because some CRM benefits may be host-mediated rather than directly tumoricidal. Likely most relevant in hyperinsulinemic or metabolically dysregulated settings.</td>
</tr>
<tr>
<td>8</td>
<td>Mitochondrial energetics and OXPHOS stress</td>
<td>↓ mitochondrial energy throughput or biosynthetic support (agent-dependent)</td>
<td>Adaptive remodeling more likely than outright injury at therapeutic exposure</td>
<td>Bioenergetic constraint</td>
<td>Metformin-like CRMs can stress complex I-linked metabolism, but many direct mitochondrial effects reported in vitro occur at supra-clinical concentrations.</td>
</tr>
<tr>
<td>9</td>
<td>HIF-1α glycolysis axis</td>
<td>↓ hypoxia-adaptive and glycolytic signaling (secondary, context-dependent)</td>
<td>Usually limited or indirect effect</td>
<td>Secondary metabolic suppression</td>
<td>This is not universal across CRMs, but often appears downstream of AMPK-mTOR and lower anabolic signaling.</td>
</tr>
<tr>
<td>10</td>
<td>Inflammation COX prostaglandin signaling</td>
<td>Inflammatory support programs ↓</td>
<td>Inflammation tone ↓</td>
<td>Microenvironmental restraint</td>
<td>Most relevant to aspirin or salicylate-containing CRM interpretations. Important clinically, but not a universal class-defining axis.</td>
</tr>
<tr>
<td>11</td>
<td>Chemosensitization and anticancer immunity</td>
<td>Therapy responsiveness ↑ in selected models</td>
<td>Normal-tissue stress tolerance may improve (context-dependent)</td>
<td>Adjunct therapeutic leverage</td>
<td>Preclinical work with hydroxycitrate and spermidine suggests improved chemotherapy efficacy and altered tumor immune contexture, but this remains incompletely validated in human oncology.</td>
</tr>
<tr>
<td>12</td>
<td>Clinical Translation Constraint</td>
<td>Heterogeneous exposure-response; tumor context strongly modifies benefit</td>
<td>Host toxicity and metabolic background shape tolerability</td>
<td>Limits class-wide deployment</td>
<td>The CRM concept is stronger than the class-level clinical evidence. Main constraints are nonuniform PK, supra-physiologic in-vitro dosing, immunosuppression for rapamycin-class agents, bleeding for aspirin, renal/lactic-acidosis concerns for metformin, and weak systemic exposure for several dietary polyphenols.</td>
</tr>
</table>