The short version of Nuclear receptor fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
GW501516 acts as an agonist at the peroxisome proliferator-activated receptor delta, a nuclear receptor that regulates gene expression. Activation shifts transcription toward genes involved in fatty acid uptake, oxidation, and energy expenditure. The compound does not bind the androgen receptor and therefore differs from anabolic steroids and SARMs. In rodent models, this metabolic shift has been linked to increased running endurance and reduced fat accumulation. The exact downstream pathways in humans remain incompletely characterized.
Early clinical research explored GW501516 for lipid disorders, obesity, and diabetes. Some short-term human studies reported changes in HDL cholesterol, LDL cholesterol, and triglycerides. The development program was discontinued after rodent studies showed dose-dependent tumor formation in multiple tissues, including liver, bladder, stomach, and skin. These findings raised concerns about long-term cancer risk in humans. Because human exposure data are limited, the clinical significance of the rodent tumors remains uncertain.
Literature on cardarine often separates receptor pharmacology from toxicology. Mechanistic papers describe PPARδ activation and gene expression changes, while safety assessments focus on carcinogenicity and species differences. Questions remain about whether rodent tumors arise through PPARδ-dependent or off-target mechanisms. Another open area is how human metabolism and exposure compare with those in animal studies. Analytical methods such as liquid chromatography–mass spectrometry are used to confirm identity in biological and product samples.
Cardarine is the common name for GW501516, a synthetic compound studied as a peroxisome proliferator-activated receptor delta agonist. Researchers developed it to explore treatments for lipid disorders and metabolic conditions. It is not an approved medicine in any country. Early clinical work examined changes in HDL cholesterol and triglycerides, but development was discontinued after animal studies raised concerns about cancer. The compound remains available as a research chemical and appears in discussions of performance enhancement.
At the molecular level, GW501516 binds and activates PPARδ, a nuclear receptor that regulates transcription. Activation shifts expression of genes involved in fatty acid oxidation, energy expenditure, and lipid transport in skeletal muscle and liver. Animal studies report increased endurance and altered lipid profiles after exposure. Human data are limited to small trials and do not establish long-term safety or efficacy. PPARδ also has roles in cell proliferation, so the relationship between activation and cancer risk remains an open question.
| Property | Value | Notes |
|---|---|---|
| Primary target | PPARδ | Nuclear receptor; not androgen receptor |
| Studied indications | Dyslipidemia; obesity; diabetes | Early clinical research; development discontinued |
| Rodent toxicity | Tumor formation in multiple tissues | Dose-dependent findings in some studies |
| Human approval | None | No approved therapeutic use |
| Typical analytical method | LC-MS/MS | Used for identity and quantification |
Activation of PPARδ changes transcription of genes involved in fatty acid transport, mitochondrial function, and skeletal muscle fuel preference. In rodent studies, pharmacological PPARδ activation was associated with increased endurance and altered body composition. These findings generated interest in performance enhancement, but species differences and study designs limit direct extrapolation to humans. Small human trials were conducted in the 2000s and later discontinued. The extent to which cardarine produces similar metabolic or performance effects in people remains an open question.
The compound is typically described as a laboratory compound rather than a therapeutic product. Published reports have explored its role in lipid disorders, insulin sensitivity, and exercise metabolism, yet no major drug regulator has approved it for medical use. Commercial samples sold under the cardarine name may vary in purity and identity. Analytical confirmation is therefore necessary when the material is discussed in scientific or regulatory contexts. Its classification as a prohibited substance in sport further shapes how it is studied and reported.
A common misconception is that cardarine has been proven safe for human use. In reality, human clinical data are limited, and long-term animal studies have raised concerns about cancer. Another misconception is that it is a supplement or vitamin-like compound. It is a synthetic research chemical with no approved medical indication. Scientific discussion often focuses on its mechanism and detection rather than therapeutic use. Regulatory and anti-doping literature treats it primarily as a prohibited substance.
Cardarine is explicitly prohibited by the World Anti-Doping Agency under the class of PPARδ agonists. Its presence in urine or blood samples can be detected using mass spectrometry-based methods, often liquid chromatography-tandem mass spectrometry. Athletes who test positive may face sanctions, including bans from competition. The compound is also regulated as a prescription-only or unapproved drug in many countries. Enforcement varies by jurisdiction, and some regions treat it as a controlled substance. Online sales may occur despite these restrictions, creating quality and legal risks.
Laboratory detection of cardarine typically involves sample preparation followed by chromatographic separation and mass spectrometric identification. Urine is the most common matrix for anti-doping tests, though blood and hair have also been explored. Methods can target the parent compound or its metabolites, depending on the expected window of detection. Reference standards are required for accurate quantification. Matrix effects and dilution can influence results, so laboratories use internal standards and validation protocols. The exact detection window varies with dose, route, and individual metabolism.
In the fitness and bodybuilding literature, cardarine is frequently discussed as an endurance agent or fat-loss compound, although such claims are not supported by robust clinical evidence. Online descriptions often mix animal data, user anecdotes, and marketing language. Researchers who study PPARδ agonists distinguish between receptor activation in controlled experiments and unsupervised use of unverified products. The latter introduces unknown purity, dose, and interactions, making reported experiences difficult to interpret scientifically.
GW501516 acts as an agonist at peroxisome proliferator-activated receptor delta, a nuclear receptor involved in transcription of genes related to lipid handling and energy use. Activation of PPARδ can shift skeletal muscle toward greater fatty acid oxidation in animal models, which is one reason it drew interest for metabolic disease and exercise research. The exact downstream effects depend on tissue, species, dose, and duration. Human data are sparse, so many proposed benefits remain hypotheses rather than established clinical outcomes.
It can do this by abstracting a proton with its basic nitrogen to make a positively charged intermediate and then use another molecule, a buffer, to extract the proton from its acidic nitrogen. In carbonic anhydrases, a histidine proton shuttle is utilized to rapidly shuttle protons away from a zinc-bound water molecule to quickly regenerate the active form of the enzyme. In helices E and F of hemoglobin, histidine influences binding of dioxygen as well as carbon monoxide. This interaction enhances the affinity of Fe(II) for O2 but destabilizes the binding of CO, which binds only 200 times stronger in hemoglobin, compared to 20,000 times stronger in free heme. The tautomerism and acid-base properties of the imidazole side chain has been characterized by 15N NMR spectroscopy. The two 15N chemical shifts are similar (about 200 ppm, relative to nitric acid on the sigma scale, on which increased shielding corresponds to increased chemical shift). NMR spectral measurements shows that the chemical shift of N1-H drops slightly, whereas the chemical shift of N3-H drops considerably (about 190 vs. 145 ppm). This change indicates that the N1-H tautomer is preferred, possibly due to hydrogen bonding to the neighboring ammonium. The shielding at N3 is substantially reduced due to the second-order paramagnetic effect, which involves a symmetry-allowed interaction between the nitrogen lone pair and the excited π* states of the aromatic ring. At pH > 9, the chemical shifts of N1 and N3 are approximately 185 and 170 ppm.
=== Brust-Schiffrin method === This method was discovered by Brust and Schiffrin in the early 1990s, and can be used to produce gold nanoparticles in organic liquids that are normally not miscible with water (like toluene). It involves the reaction of a chlorauric acid solution with tetraoctylammonium bromide (TOAB) solution in toluene and sodium borohydride as an anti-coagulant and a reducing agent, respectively. Here, the gold nanoparticles will be around 5–6 nm. NaBH4 is the reducing agent, and TOAB is both the phase transfer catalyst and the stabilizing agent. TOAB does not bind to the gold nanoparticles particularly strongly, so the solution will aggregate gradually over the course of approximately two weeks. To prevent this, one can add a stronger binding agent, like a thiol (in particular, alkanethiols), which will bind to gold, producing a near-permanent solution. Alkanethiol protected gold nanoparticles can be precipitated and then redissolved. Thiols are better binding agents because there is a strong affinity for the gold-sulfur bonds that form when the two substances react with each other. Tetra-dodecanthiol is a commonly used strong binding agent to synthesize smaller particles. Some of the phase transfer agent may remain bound to the purified nanoparticles, this may affect physical properties such as solubility. In order to remove as much of this agent as possible, the nanoparticles must be further purified by soxhlet extraction.
While not prescribed as a pharmaceutical in the West, in Russia and certain other Eastern European countries it is available as a prescription medicine under brand names including Phenotropil (also spelled Fenotropil, Phenotropyl, and Fenotropyl), Actitropil, and Nanotropil, among others. Phenylpiracetam is not scheduled by the United States Drug Enforcement Administration (DEA) as of 2016.
Sources: en.wikipedia.org
==== MeSH D13.695.827 – ribonucleotides ==== MeSH D13.695.827.068 – adenine nucleotides MeSH D13.695.827.068.124 – adenosine diphosphate MeSH D13.695.827.068.124.070 – adenosine diphosphate sugars MeSH D13.695.827.068.124.070.075 – adenosine diphosphate glucose MeSH D13.695.827.068.124.070.125 – adenosine diphosphate ribose MeSH D13.695.827.068.124.070.125.040 – o-acetyl-adp-ribose MeSH D13.695.827.068.124.070.125.195 – cyclic adp-ribose MeSH D13.695.827.068.180 – adenosine monophosphate MeSH D13.695.827.068.180.080 – adenosine phosphosulfate MeSH D13.695.827.068.236 – adenosine triphosphate MeSH D13.695.827.068.236.050 – adenylyl imidodiphosphate MeSH D13.695.827.068.236.250 – ethenoadenosine triphosphate MeSH D13.695.827.068.309 – clofarabine MeSH D13.695.827.068.382 – coenzyme a MeSH D13.695.827.068.382.300 – acyl coenzyme a MeSH D13.695.827.068.382.300.020 – acetyl coenzyme a MeSH D13.695.827.068.382.300.500 – malonyl coenzyme a MeSH D13.695.827.068.382.300.700 – palmitoyl coenzyme a MeSH D13.695.827.068.395 – cyclic amp MeSH D13.695.827.068.395.225 – 8-bromo cyclic adenosine monophosphate MeSH D13.695.827.068.395.250 – bucladesine MeSH D13.695.827.068.506 – flavin-adenine dinucleotide MeSH D13.695.827.068.694 – nad MeSH D13.695.827.068.749 – nadp MeSH D13.695.827.068.850 – phosphoadenosine phosphosulfate MeSH D13.695.827.232 – cytosine nucleotides MeSH D13.695.827.232.115 – cyclic cmp MeSH D13.695.827.232.150 – cytidine diphosphate MeSH D13.695.827.232.150.180 – cytidine diphosphate choline MeSH D13.695.827.232.150.210 – cytidine diphosphate diglycerides MeSH D13.695.827.232.370 – cytidine monophosphate MeSH D13.695.827.232.370.250 – cytidine monophosphate n-acetylneuraminic acid MeSH D13.695.827.232.400 – cytidine triphosphate MeSH D13.695.827.349 – flavin mononucleotide MeSH D13.695.827.426 – guanine nucleotides MeSH D13.695.827.426.160 – cyclic gmp MeSH D13.695.827.426.160.325 – dibutyryl cyclic gmp MeSH D13.695.827.426.340 – guanosine diphosphate MeSH D13.695.827.426.340.350 – guanosine diphosphate sugars MeSH D13.695.827.426.340.350.400 – guanosine diphosphate fucose MeSH D13.695.827.426.340.350.500 – guanosine diphosphate mannose MeSH D13.695.827.426.400 – guanosine monophosphate MeSH D13.695.827.426.440 – guanosine pentaphosphate MeSH D13.695.827.426.480 – guanosine tetraphosphate MeSH D13.695.827.426.504 – guanosine triphosphate MeSH D13.695.827.426.504.380 – guanosine 5'-o-(3-thiotriphosphate) MeSH D13.695.827.426.504.400 – guanylyl imidodiphosphate MeSH D13.695.827.426.700 – rna caps MeSH D13.695.827.426.700.710 – rna cap analogs MeSH D13.695.827.519 – inosine nucleotides MeSH D13.695.827.519.300 – cyclic imp MeSH D13.695.827.519.400 – inosine diphosphate MeSH D13.695.827.519.500 – inosine monophosphate MeSH D13.695.827.519.800 – inosine triphosphate MeSH D13.695.827.648 – nicotinamide mononucleotide MeSH D13.695.827.708 – nucleoside diphosphate sugars MeSH D13.695.827.708.070 – adenosine diphosphate sugars MeSH D13.695.827.708.070.075 – adenosine diphosphate glucose MeSH D13.695.827.708.070.125 – adenosine diphosphate ribose MeSH D13.695.827.708.070.125.040 – o-acetyl-adp-ribose MeSH D13.695.827.708.070.125.195 – cyclic adp-ribose MeSH D13.695.827.708.070.125.600 – poly adenosine diphosphate ribose MeSH D13.695.827.708.260 – cytidine diphosphate diglycerides MeSH D13.695.827.708.400 – guanosine diphosphate sugars MeSH D13.695.827.708.400.410 – guanosine diphosphate fucose MeSH D13.695.827.708.400.500 – guanosine diphosphate mannose MeSH D13.695.827.708.727 – uridine diphosphate sugars MeSH D13.695.827.708.727.100 – uridine diphosphate n-acetylgalactosamine MeSH D13.695.827.708.727.120 – uridine diphosphate n-acetylglucosamine MeSH D13.695.827.708.727.150 – uridine diphosphate n-acetylmuramic acid MeSH D13.695.827.708.727.300 – uridine diphosphate galactose MeSH D13.695.827.708.727.350 – uridine diphosphate glucose MeSH D13.695.827.708.727.375 – uridine diphosphate glucuronic acid MeSH D13.695.827.708.727.800 – uridine diphosphate xylose MeSH D13.695.827.919 – uracil nucleotides MeSH D13.695.827.919.600 – uridine diphosphate MeSH D13.695.827.919.600.677 – uridine diphosphate sugars MeSH D13.695.827.919.600.677.100 – uridine diphosphate n-acetylgalactosamine MeSH D13.695.827.919.600.677.120 – uridine diphosphate n-acetylglucosamine MeSH D13.695.827.919.600.677.150 – uridine diphosphate n-acetylmuramic acid MeSH D13.695.827.919.600.677.300 – uridine diphosphate galactose MeSH D13.695.827.919.600.677.350 – uridine diphosphate glucose MeSH D13.695.827.919.600.677.375 – uridine diphosphate glucuronic acid MeSH D13.695.827.919.600.677.800 – uridine diphosphate xylose MeSH D13.695.827.919.877 – uridine monophosphate MeSH D13.695.827.919.877.500 – sofosbuvir MeSH D13.695.827.919.950 – uridine triphosphate
Cobalt-60 (60Co) is a synthetic radioactive isotope of cobalt with a half-life of 5.2714 years. It is produced artificially in nuclear reactors through neutron activation of 59Co (of which natural cobalt consists entirely). Measurable quantities are also produced as a by-product of typical nuclear power plant operation and may be detected externally when leaks occur. In the latter case, the incidentally produced 60Co is largely the result of multiple stages of neutron activation of iron isotopes in the reactor's steel structures via the creation of its 59Co precursor. The simplest case of the latter would result from the activation of 58Fe. 60Co undergoes beta decay to an excited state of the stable isotope nickel-60 (60Ni), which then emits two gamma rays with energies of 1.17 MeV and 1.33 MeV. The overall equation of the nuclear reaction (activation and decay) is: 5927Co + n → 6027Co → 6028Ni + e− + νe + 2γ
== Protein kinase activation == The cGMP-dependent protein kinase (PKG) activation pathway begins with the production of cGMP by guanylyl cyclase enzymes, which can be activated by signaling molecules such as nitric oxide (NO) or natriuretic peptides. Elevated cGMP levels then lead to the activation of some protein-dependent kinases like PKG. For example, PKG (protein kinase G) is a dimer consisting of one catalytic and one regulatory unit, with the regulatory units blocking the active sites of the catalytic units. cGMP binds to sites on the regulatory units of PKG and activates the catalytic units, enabling them to phosphorylate their substrates. Unlike with the activation of some other protein kinases, notably PKA, the PKG is activated but the catalytic and regulatory units do not disassociate. Once activated, PKG phosphorylates various target proteins, altering their function and contributing to cellular processes such as smooth muscle relaxation, ion channel regulation, and inhibition of platelet aggregation. This pathway is also significant in cardiovascular physiology, where it helps maintain vascular tone and blood pressure.
The poem revolves around an isolated and anxious man who runs throughout the city, his anxiety and fears taking on the personified image of a grandiose beast that has the makeup of a dragon and lion. While not inherently stated, the beast is likely that of a decadent form of a sphinx due to its appearance and grand nature.
Sources: en.wikipedia.org
It targets PPARδ, a nuclear receptor involved in lipid and energy metabolism. It does not act primarily on androgen receptors. This distinction separates it from SARMs.
Rodent studies found dose-dependent tumors in several organs. The sponsor discontinued the program over cancer concerns. Human risk from long-term use remains unknown.
Controlled human endurance trials are lacking. Animal studies show increased exercise capacity under some conditions. Anecdotal reports are not equivalent to clinical evidence.
Cardarine is a common name for the investigational compound GW501516. It acts as a PPARδ agonist and is not approved for human use. It is prohibited in sport.