Nuclear receptor is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2026-06-20. Numbers and descriptions here follow the published literature rather than marketing material.
Human trials of GW501516 were small and short in duration. They examined lipid levels, glucose handling, and other metabolic markers, but the programs were halted after the animal cancer findings. No approved therapeutic product exists, and published human data are insufficient for establishing long-term safety. Reports of use for athletic performance come mainly from non-clinical settings and cannot be verified through controlled trials. Independent testing of products sold as cardarine has found inconsistent purity and labeling.
Laboratory studies indicate that GW501516 activates PPARδ, a nuclear receptor involved in fatty acid oxidation and energy metabolism. In rodent experiments, treated animals often showed increased endurance and reduced fat mass. These effects were observed under controlled conditions and do not establish safe or effective use in humans. The exact dose-response relationship in humans remains poorly characterized. Species differences in metabolism can affect how results translate across animals and people.
Safety concerns emerged from long-term animal studies. In rodents given the compound for extended periods, researchers found an increased incidence of certain cancers, including liver and bladder tumors. These findings contributed to the discontinuation of clinical development. Whether similar risks apply to short-term or low-level exposure in humans is not established, and controlled human safety data are limited. The relevance of high-dose rodent carcinogenicity findings to human use remains a subject of debate.
Handling and quality assessment of cardarine reference material follow general laboratory practices for poorly characterized compounds. It typically appears as a white to off-white powder and is sparingly soluble in water but soluble in organic solvents such as dimethyl sulfoxide and ethanol. Storage recommendations usually specify a cool, dry, dark place, with long-term storage at low temperature and desiccation. Purity may be checked by high-performance liquid chromatography with ultraviolet detection, while identity is confirmed by mass spectrometry and nuclear magnetic resonance. No pharmacopeial monograph exists, so reported purity and stability depend on the supplier’s methods.
GW501516 acts as a selective agonist at PPARδ, a nuclear receptor that regulates transcription of genes involved in lipid handling and energy metabolism. Activation of PPARδ in preclinical models increases fatty acid oxidation, mitochondrial biogenesis, and exercise endurance in rodents. These effects have made the compound a subject of metabolic research and also a target for sport anti-doping rules. In humans, however, controlled studies are limited, and whether similar endurance or metabolic changes occur at tolerated exposures remains an open question. The receptor’s broad tissue distribution also means downstream effects may vary by organ and condition.
Detection of GW501516 in biological samples generally relies on liquid chromatography coupled with tandem mass spectrometry. Urine is a common matrix in anti-doping analysis, while blood or plasma may be used in research settings. Sample preparation can involve enzymatic hydrolysis, protein precipitation, or solid-phase extraction before instrumental analysis. Because the compound undergoes metabolism, assays may target the parent molecule, one or more metabolites, or both. Detection windows are not fixed; they depend on factors such as dose, route, individual metabolism, and assay sensitivity. Reference standards are required for accurate identification and quantification.
| Property | Value | Notes |
|---|---|---|
| Primary target | PPARδ (NR1C2) | Nuclear receptor involved in lipid metabolism |
| Preclinical effect | Increased fatty acid oxidation | Observed in rodent studies |
| Key safety signal | Tumors in rodents after long-term exposure | Contributed to halted clinical development |
| Human trial status | No approved product; development stopped | Limited short-term metabolic data |
| Sport regulatory status | Prohibited at all times | WADA hormone and metabolic modulators class |
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.
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.
Safety discussions about cardarine frequently cite rodent carcinogenicity findings reported in the 2000s. In those studies, treated animals developed tumors at multiple sites, leading sponsors to discontinue clinical development. The relevance of these findings to humans has not been resolved, but they are a major reason the compound is not approved. Current literature emphasizes uncertainty about long-term effects and the risks of unregulated use. Regulators and health agencies have not established a safe human exposure level.
Cardarine is a synthetic compound also known as GW501516, GW-501516, and sometimes endurobol. It was developed as a selective agonist of peroxisome proliferator-activated receptor delta, a nuclear receptor involved in fatty acid oxidation and energy metabolism. The compound was studied in preclinical models for metabolic and cardiovascular conditions, but it did not become a marketed human medicine. In regulatory and anti-doping contexts, it is treated as a prohibited substance rather than a licensed medicine.
The pharmacological interest in cardarine centers on PPARδ activation and its downstream effects on lipid handling and mitochondrial function. In animal studies, PPARδ agonists have been associated with changes in exercise endurance and fatty acid utilization, though results vary by model and protocol. Human data remain sparse, and the absence of large controlled trials limits conclusions about efficacy. Researchers often describe the compound as a tool for probing PPARδ biology rather than a proven therapeutic agent.
== Evolution == By virtue of its antibacterial properties, it has been speculated that sv-LAAOs are in part responsible for the maintenance and stabilization of both the venom and venom gland in snake species.
No.5 Squadron South African Air Force operated Mustang Mk IIIs (P-51B/C) and Mk IVs (P-51D/K) in Italy during World War II, beginning in September 1944, when the squadron converted to the Mustang Mk III from Kittyhawks. The Mk IV and Mk IVA came into SA service in March 1945. These aircraft were generally camouflaged in the British style, having been drawn from RAF stocks; all carried RAF serial numbers and were struck off charge and scrapped in October 1945. In 1950, 2 Squadron SAAF was supplied with F-51D Mustangs by the United States for Korean War service. The type performed well in South African hands before being replaced by the F-86 Sabre in 1952 and 1953. South Korea
=== Spin column === Spin column-based nucleic acid purification is a method of purifying DNA, RNA or plasmid from a sample using a spin column filter. The method is based on the principle of selectively binding nucleic acids to a solid matrix in the spin column, while other contaminants, such as proteins and salts, are washed away. The conditions are then changed to elute the purified nucleic acid off the column using a suitable elution buffer.
=== Global market === During the 2000s, Biocon established its subsidiary Biocon Biologics and substantially grew its production of existing drugs for the American and European markets. Regulatory bodies such as the American Food and Drug Administration and various European state agencies (later the European Commission) have approved Biocon for production of many such products, starting with lovastatin in 2001. Biocon's production largely focused on generics, which as of 2022 had saved European healthcare systems some €30 billion in drug costs. In the 2010s, Biocon began rapidly expanding its production and market reach. In 2008, Biocon acquired a 70% stake in German pharmaceutical company AxiCorp GmbH. The following year, Biocon established a partnered research facility in Bengaluru with American pharmaceutical corporation Bristol Myers Squibb, and announced a strategic collaboration with Mylan to enter the global generic biologics market. The following years saw a steady expansion of major Biocon production facilities in Asian nations, including Malaysia in 2010, and in Bangalone in 2016 with partner Amgen.
Eventually, blood clots are reorganized and resorbed by a process termed fibrinolysis. The main enzyme responsible for this process is plasmin, which is regulated by plasmin activators and plasmin inhibitors.
Sources: en.wikipedia.org
== Clinical significance == Erectile dysfunction, the inability to achieve or maintain an erection, is the most common disorder of the penis, and most commonly results from vascular disease. Penile fracture is a rupture of the tunica albuginea caused by severe blunt trauma to the erect penis, which raises cavernosal pressure beyond what the tunica can withstand. Most cases occur during sexual intercourse. During erection the circular fibres of the tunica thin from around 2 mm to about 0.25 mm, and the weakest point lies on the ventral side of the shaft immediately adjacent to the urethra, where most ruptures occur; the urethra is involved in roughly 20% of cases. Buck's fascia normally confines the resulting haematoma and swelling to the penile shaft. Penile fracture is regarded as a urological surgical emergency, as delayed treatment can result in long-lasting sexual dysfunction. In Peyronie's disease, fibrous plaques containing excessive collagen form within the tunica albuginea, causing focal inelasticity and curvature of the penis. The condition is usually benign but may be associated with painful erections or erectile dysfunction. Its underlying pathogenesis is not known, although evidence suggests that repeated microtrauma leads to fibrin deposition from microvascular injury. Priapism is a prolonged, rigid erection occurring in the absence of appropriate stimulation, conventionally defined as one lasting four hours or longer and not relieved by ejaculation.
== Selected bibliography == Daly, Marie M.; Mirsky, A.E. (June 1949). "Chromatography of Purines and Pyrimidines on Starch Columns". Journal of Biological Chemistry. 179 (2): 981–982. doi:10.1016/S0021-9258(19)51291-1. PMID 18150028. Daly, M.M.; Allfrey, V.G.; Mirsky, A.E. (May 20, 1950). "Purine and Pyrimidine Contents of Some Desoxypentose Nucleic Acids" (PDF). Journal of General Physiology. 33 (5): 497–510. doi:10.1085/jgp.33.5.497. PMC 2147206. PMID 15422104. Daly, Marie; Mirsky, A.E.; Ris, Hans (March 20, 1951). "The Amino Acid Composition and Some Properties of Histones" (PDF). The Journal of General Physiology. 34 (4): 439–450. doi:10.1085/jgp.34.4.439. PMC 2147226. PMID 14824510. Daly, Marie M.; Mirsky, A.E. (November 1952). "Formation of Protein in the Pancreas". Journal of General Physiology. 36 (2): 243–254. doi:10.1085/jgp.36.2.243. PMC 2147369. PMID 13011280. Daly, Marie M.; Allfrey, V.G.; Mirsky, A.E. (November 1952). "Uptake of Glycine-N15 by Components of Cell Nuclei" (PDF). Journal of General Physiology. 36 (2): 173–179. doi:10.1085/jgp.36.2.173. PMC 2147362. PMID 13011275. Allfrey, V.; Daly, M.M.; Mirsky, A.E. (November 20, 1953). "Synthesis of protein in the pancreas. II. The role of ribonucleoprotein in protein synthesis". Journal of General Physiology. 37 (2): 157–175. doi:10.1085/jgp.37.2.157. PMC 214743. PMID 13109153. Mirsky, A.E.; Allfrey, V.G.; Daly, M.M. (September 1954). "The Uptake of N15-Labelled Glycine by Liver Proteins". Journal of Histochemistry and Cytochemistry. 2 (5): 376–377. doi:10.1177/2.5.376. PMID 13192326. S2CID 40223958.
=== CD4+ T-cells === Tetramers that bind to helper T-cells have also been developed. Helper T-cells or CD4+ T-cells express CD4 co-receptors. They bind to class II MHC molecules, which are only expressed in professional antigen-presenting cells like dendritic cells or macrophages. Class II MHC molecules present extracellular antigens, allowing helper T-cells to detect bacteria, fungi, and parasites. Class II MHC tetramer use is becoming more common, but the tetramers are more difficult to create than class I tetramers and the bond between helper T-cells and MHC molecules is even weaker.
=== CD200 === Basophil function is inhibited by CD200. Herpesvirus-6, herpesvirus-7, and herpesvirus-8 produce a CD200 homolog which also inhibits basophil function. This suggests that basophils may play a role in the immune response to these viruses. The role of basophils in the immune response to these viruses is further supported by findings that the CD200 receptor is expressed more frequently in basophils than in other circulating leukocytes.
Complications may occur immediately following the myocardial infarction or may take time to develop. Disturbances of heart rhythms, including atrial fibrillation, ventricular tachycardia and fibrillation and heart block can arise as a result of ischemia, cardiac scarring, and infarct location. Stroke is also a risk, either as a result of clots transmitted from the heart during PCI, as a result of bleeding following anticoagulation, or as a result of disturbances in the heart's ability to pump effectively as a result of the infarction. Regurgitation of blood through the mitral valve is possible, particularly if the infarction causes dysfunction of the papillary muscle. Cardiogenic shock as a result of the heart being unable to adequately pump blood may develop, dependent on infarct size, and is most likely to occur within the days following an acute myocardial infarction. Cardiogenic shock is the largest cause of in-hospital mortality. Rupture of the ventricular dividing wall or left ventricular wall may occur within the initial weeks. Dressler's syndrome, a reaction following larger infarcts and a cause of pericarditis is also possible. Heart failure may develop as a long-term consequence, with an impaired ability of heart muscle to pump, scarring, and an increase in the size of the existing muscle. Aneurysm of the left ventricle myocardium develops in about 10% of MI and is itself a risk factor for heart failure, ventricular arrhythmia, and the development of clots.
Sources: en.wikipedia.org
In 1974, Torbert left NRPS; he and Matthew Kelly co-founded the band Kingfish (best known for Bob Weir's membership during the Grateful Dead's late-1974 to mid-1976 touring hiatus) the year before. Initially he was replaced by Skip Battin (formerly of Skip & Flip and the early 1970s lineup of The Byrds), who briefly emerged as the dominant creative force in the band due to his prolific songwriting collaboration with controversial Hollywood impresario Kim Fowley. Stephen A. Love of Rick Nelson's Stone Canyon Band and the Roger McGuinn Band replaced Battin after he left the group to co-found a reconstituted lineup of The Flying Burrito Brothers in 1976. Shortly thereafter, Spencer Dryden relinquished his performance duties to manage the group in 1977. His musical replacement was Patrick Shanahan. Allen Kemp joined on bass in 1978 before emerging as a co-frontman on guitar and vocals, contributing prominently to the songwriting for the band's last major label release, 1981's Feelin' All Right. In 1982, Nelson and Cage left the band, leaving Dawson as the sole remaining member from the classic lineup.
=== Stem cells === The precursor of the melanocyte is the melanoblast. In adults, stem cells are contained in the bulge area of the outer root sheath of hair follicles. When a hair is lost and the hair follicle regenerates, the stem cells are activated. These stem cells develop into both keratinocyte precursors and melanoblasts - and these melanoblasts supply both hair and skin (moving into the basal layer of the epidermis). There is additionally evidence that melanocyte stem cells are present in cutaneous nerves, with nerve signals causing these cells to differentiate into melanocytes for the skin.
The US government responded by saying the Rhodesian mission and its staff had no official diplomatic status and violated no US laws. Portugal pursued a middle path with Rhodesia. While not officially recognising Rhodesia under Ian Smith, the government of António Salazar did permit Rhodesia to establish a representative mission in Lisbon, and permitted Rhodesian exports and imports through their province of Mozambique. The Portuguese government in power at that time, authoritarian and ardently anti-communist, gave active behind-the-scenes support in Rhodesia's fight against the guerrilla groups. South Africa, itself under international pressure as a white minority government, pursued a policy of détente with the black African states at the time. These states wanted South Africa to pressure Ian Smith to accept a faster transition to majority rule in Rhodesia, in return for pledges of non-interference in South Africa's internal affairs. Prime Minister John Vorster, believing majority rule in Rhodesia would lead to international acceptance for South Africa, used a number of tactics to pressure Smith. The South African government held up shipments of fuel and ammunition and pulled out friendly South African forces from Rhodesia. The combined loss of Mozambique and the loss of support from South Africa dealt critical blows to the Rhodesian government.
==== MeSH D12.776.835.725.934 – prokaryotic initiation factors ==== MeSH D12.776.835.725.934.374 – prokaryotic initiation factor-1 MeSH D12.776.835.725.934.562 – prokaryotic initiation factor-2 MeSH D12.776.835.725.934.750 – prokaryotic initiation factor-3
==== Synthetic cannabinoids ==== Synthetic cannabinoids, members of the aminoalkylindole class, made its first appearance in 2008. It was given the name 'JWH' because a chemist called John W. Huffman synthesized them in the 1960s. Most synthetic analogs of cannabinoids mimic the structure of 9-tetrahydrocannabinol (THC), which makes them an agonist to the CB1(Type I) and CB2 (Type II) cannabinoid receptors. CB1 in particular, is expressed in the central nervous system and largely responsible for the psychoactive effect.. A typical agonist consists of the following components: head, linker core and tail. Altering the structure from each component will affect the drug's affinity to the cannabinoid receptors. For instance, when a fluoride or nitrile group is attached to the carbon chains, the affinity for CB1 will increase. The aromatic rings from the aminoalkylindole class also play the role of enhancing the affinity by forming a hydrophobic cavity to stabilize the CB1 receptors. As legislation becomes tightened under the monitoring of Early Warning System (EWS), attempts are made to alter the structure which produce new analogues such as the Cyclopropylindoles (UR-144) and adamantylindoles (APINACA).
Sources: en.wikipedia.org
Rodent studies reported increased endurance and fat oxidation after GW501516 exposure. Long-term studies also found higher rates of some tumors, which led to halted development.
Small short-term human trials examined metabolic markers such as lipids and glucose. The trials did not continue after rodent cancer findings, so long-term human safety is unknown.
Controlled human trials have not established a performance benefit. Anecdotal reports exist, but they are not reliable evidence.
Cardarine targets PPARδ, a nuclear receptor involved in lipid and energy metabolism. It does not bind the androgen receptor in the way SARMs do.