AICAR: Complete Research Guide & Chemical Profile

AICAR (5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside) is a nucleoside analog with the molecular formula C9H14N4O5 and a molecular weight of 258.23 Da. It is also known by its INN name acadesine and the developmental code GP-1-110. AICAR is an intermediate in the de novo purine biosynthesis pathway and occurs naturally at low concentrations in mammalian cells. The compound is a white to off-white crystalline powder that is freely soluble in DMSO and moderately soluble in aqueous buffers at physiological pH.

Structurally, AICAR consists of a 5-aminoimidazole-4-carboxamide (AICA) base linked to a ribose sugar via a beta-N-glycosidic bond. Upon cellular uptake via adenosine transporters, AICAR is phosphorylated by adenosine kinase to generate ZMP (AICAR monophosphate, 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranosyl 5-monophosphate). ZMP is the pharmacologically active metabolite that mimics AMP and allosterically activates AMPK. The conversion to ZMP is essential for AICAR biological activity, and adenosine kinase inhibitors block its effects.

AICAR is distinct from peptide research compounds in that it is a small molecule nucleoside rather than an amino acid polymer. However, it appears in peptide vendor catalogs because of its relevance to metabolic and exercise physiology research that frequently intersects with peptide-based investigations of growth hormone secretagogues, myostatin inhibitors, and other metabolic modulators. Researchers should note this classification distinction when designing experiments.

• Chemical name: 5-Aminoimidazole-4-carboxamide ribonucleoside
• Synonyms: Acadesine, AICA-riboside, GP-1-110
• Molecular formula: C9H14N4O5
• Molecular weight: 258.23 Da
• CAS number: 2627-69-2
• Active metabolite: ZMP (AICAR monophosphate)
• Solubility: Freely soluble in DMSO; moderately soluble in water
• Storage: -20°C desiccated; protect from light

AMP-activated protein kinase (AMPK) is a heterotrimeric serine/threonine kinase composed of catalytic alpha, scaffolding beta, and regulatory gamma subunits. AMPK functions as a cellular energy sensor that is activated when the AMP:ATP ratio increases, as occurs during energy stress. ZMP, the intracellular metabolite of AICAR, binds to the gamma subunit CBS domains (cystathionine beta-synthase domains) at the same allosteric sites as AMP, promoting conformational changes that activate the kinase.

ZMP binding to AMPK produces three cooperative effects: (1) allosteric activation of the kinase domain, increasing catalytic activity approximately 5-fold; (2) promotion of Thr172 phosphorylation on the alpha subunit by upstream kinases LKB1 and CaMKKbeta; and (3) protection of Thr172 from dephosphorylation by protein phosphatases (PP2C family). The net result is a sustained increase in AMPK activity that persists for the duration of elevated intracellular ZMP concentrations. Typical research concentrations of AICAR (0.5-2.0 mM) produce robust AMPK activation within 30-60 minutes in cultured cells.

It is important to note that AICAR/ZMP is not a completely selective AMPK activator. ZMP also modulates other AMP-sensitive enzymes, including fructose-1,6-bisphosphatase (inhibition), glycogen phosphorylase (activation), and ATIC (the enzyme that normally converts ZMP to IMP in purine biosynthesis). These off-target effects must be controlled for in experimental design, and AMPK-independent actions of AICAR have been documented at concentrations above 1 mM. The use of Compound C (dorsomorphin) as an AMPK inhibitor control or genetic AMPK-knockout models is recommended.

AICAR gained widespread attention as an exercise mimetic following the landmark 2008 study by Narkar and colleagues demonstrating that AICAR treatment in sedentary mice improved running endurance by 44% without any exercise training. This effect was mediated through AMPK-dependent activation of a transcriptional program that upregulated oxidative metabolism genes, promoted slow-twitch (type I) muscle fiber characteristics, and enhanced mitochondrial biogenesis in skeletal muscle.

The exercise mimetic effects of AICAR involve coordinated activation of several AMPK downstream targets. Phosphorylation of PGC-1alpha (peroxisome proliferator-activated receptor gamma coactivator 1-alpha) drives mitochondrial biogenesis and oxidative gene expression. AMPK-mediated phosphorylation of ACC (acetyl-CoA carboxylase) relieves malonyl-CoA inhibition of CPT1 (carnitine palmitoyltransferase 1), enhancing fatty acid transport into mitochondria for beta-oxidation. Additionally, AMPK activates SIRT1 through increased NAD+ availability, creating a positive feedback loop that amplifies oxidative metabolic capacity.

Subsequent studies refined the exercise mimetic concept. AICAR treatment combined with exercise training produced additive improvements in endurance capacity and metabolic flexibility in rodent models. However, AICAR alone did not fully replicate all exercise adaptations; mechanical load-dependent signals (mTOR-mediated hypertrophy, bone remodeling) and neuromuscular adaptations were not engaged by AICAR. Thus, AICAR is more accurately described as a partial exercise mimetic that recapitulates the metabolic/oxidative component of exercise adaptation.

AICAR stimulates glucose uptake in skeletal muscle through an insulin-independent mechanism. AMPK activation promotes translocation of GLUT4 glucose transporters to the plasma membrane via phosphorylation of TBC1D1 and AS160/TBC1D4 (Rab-GTPase activating proteins). This AMPK-dependent glucose uptake pathway is distinct from the PI3K/Akt pathway activated by insulin, and the two pathways produce additive effects when co-stimulated. AICAR-stimulated glucose uptake is preserved in insulin-resistant muscle, making it a valuable research tool for studying insulin-independent glucose disposal.

In whole-animal studies, acute AICAR administration produces dose-dependent hypoglycemia through a combination of enhanced peripheral glucose uptake and suppressed hepatic glucose production. The hepatic effect involves AMPK-mediated transcriptional repression of gluconeogenic enzymes PEPCK and G6Pase through phosphorylation and nuclear exclusion of the transcriptional coactivator CRTC2 (CREB-regulated transcription coactivator 2). Chronic AICAR treatment in rodent models of type 2 diabetes (db/db mice, Zucker fatty rats) improved glucose tolerance and insulin sensitivity.

The glucose-lowering effects of AICAR share mechanistic overlap with the diabetes medication metformin, which also activates AMPK, albeit through indirect mitochondrial complex I inhibition rather than direct allosteric activation. Comparative studies have shown that AICAR produces more rapid and potent AMPK activation than metformin in skeletal muscle, while metformin shows greater hepatic selectivity. These pharmacological differences make AICAR and metformin complementary research tools for dissecting tissue-specific AMPK functions.

AMPK activation by AICAR profoundly stimulates fatty acid oxidation while simultaneously inhibiting fatty acid synthesis. The dual effect is mediated primarily through phosphorylation of ACC1 (cytoplasmic, lipogenic) and ACC2 (mitochondrial-associated, regulatory). Phosphorylation of ACC1 at Ser79 inhibits malonyl-CoA synthesis, reducing substrate availability for de novo lipogenesis. Phosphorylation of ACC2 at Ser212 decreases the local malonyl-CoA pool near mitochondria, relieving allosteric inhibition of CPT1 and enhancing long-chain fatty acid transport into mitochondria.

In hepatocytes, AICAR treatment reduces lipogenic gene expression by phosphorylating and inactivating SREBP-1c (sterol regulatory element-binding protein 1c), the master transcriptional regulator of fatty acid synthesis. Simultaneously, AMPK activates PPARalpha-dependent transcription of fatty acid oxidation genes. These coordinated effects produce a net shift from lipid storage to lipid oxidation. In high-fat diet rodent models, chronic AICAR administration reduced hepatic steatosis, decreased circulating triglycerides, and improved the hepatic lipid profile.

In adipose tissue, AICAR inhibits lipolysis through AMPK-mediated phosphorylation of HSL (hormone-sensitive lipase) at Ser565, which prevents PKA-activating phosphorylation at Ser563. This anti-lipolytic effect may seem contradictory to the pro-oxidative metabolic shift, but it serves to prevent excessive free fatty acid release that could exacerbate hepatic steatosis and insulin resistance. The tissue-specific effects of AICAR on lipid metabolism highlight the context-dependent nature of AMPK signaling.

AICAR demonstrates cardioprotective properties in ischemia-reperfusion injury models. AMPK activation during ischemia promotes glycolysis for anaerobic ATP generation and activates autophagy to recycle damaged organelles. In isolated perfused heart models and in vivo coronary occlusion studies, AICAR pretreatment reduced infarct size by 30-50%, preserved contractile function, and decreased cardiomyocyte apoptosis. The protective mechanism involves AMPK-dependent phosphorylation of eNOS, increasing nitric oxide production and improving coronary flow during reperfusion.

Clinical investigation of AICAR (as acadesine) in cardiovascular medicine reached Phase III trials for reduction of perioperative myocardial infarction in patients undergoing coronary artery bypass graft (CABG) surgery. While early Phase II results were promising, the Phase III trial did not meet its primary endpoint. Post-hoc analyses suggested potential benefit in specific patient subgroups, but the cardiovascular clinical development program was ultimately discontinued. The clinical data nonetheless provided extensive human pharmacokinetic and safety information for AICAR.

AMPK activation by AICAR produces cytostatic and cytotoxic effects in various cancer cell lines. The anti-proliferative mechanisms include: (1) inhibition of mTORC1 through AMPK-mediated phosphorylation of TSC2 and Raptor, reducing protein synthesis and cell growth; (2) cell cycle arrest at G1/S through p53 phosphorylation and p21 upregulation; (3) induction of apoptosis in cells with defective p53 through metabolic crisis. Cancer cells with high glycolytic dependence (Warburg effect) are particularly sensitive to AICAR-induced metabolic stress.

The tumor suppressor kinase LKB1, which is the primary upstream kinase for AMPK, is frequently mutated in certain cancers (Peutz-Jeghers syndrome, lung adenocarcinoma). In LKB1-null cancer cells, AICAR fails to activate AMPK, providing a genetic tool for confirming AMPK-dependence of observed effects. Conversely, some studies have reported AMPK-independent anti-cancer effects of AICAR, particularly at high concentrations, attributed to ZMP-mediated inhibition of de novo purine synthesis depleting nucleotide pools required for DNA replication.

AICAR occupies a unique position in intermediary metabolism as a natural intermediate in the de novo purine biosynthesis pathway. Endogenous AICAR (as ZMP) is normally converted to IMP by the bifunctional enzyme ATIC (5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase). When exogenous AICAR is administered at pharmacological concentrations, the resulting ZMP accumulation exceeds ATIC capacity, leading to both AMPK activation and disruption of purine metabolism.

The purine biosynthesis interference has several research-relevant consequences. ZMP accumulation inhibits adenosine deaminase and adenylosuccinate lyase, altering the balance of adenine and guanine nucleotides. At high concentrations (>2 mM), AICAR can deplete cellular ATP pools as adenosine kinase consumes ATP during ZMP generation. These off-target effects necessitate careful dose-response characterization and appropriate controls. Time-course studies should monitor cellular ATP levels alongside AMPK activity to ensure that observed effects reflect specific AMPK activation rather than metabolic toxicity.

More selective AMPK activators have been developed as pharmacological tools, including A-769662 (beta1-selective allosteric activator), MK-8722 (pan-AMPK activator), and the thienopyridone compound 991. These compounds activate AMPK through the ADaM (allosteric drug and metabolite) site on the alpha-beta interface rather than the gamma subunit CBS domains, providing mechanistically distinct activation. Researchers are increasingly using these newer tools alongside AICAR to confirm AMPK-dependence and distinguish gamma-site from ADaM-site activation.

AICAR identity and purity are routinely assessed by HPLC, with UV detection at 260 nm exploiting the nucleoside chromophore. Reverse-phase C18 HPLC with aqueous/acetonitrile mobile phases provides baseline separation of AICAR from related nucleoside impurities. Research-grade AICAR should meet a purity specification of 98% or greater by HPLC area normalization. Identity confirmation by 1H-NMR, 13C-NMR, or high-resolution mass spectrometry (HRMS; expected [M+H]+ = 259.1042) is recommended for new supplier qualification.

For quantification of AICAR and ZMP in biological samples, LC-MS/MS methods using HILIC (hydrophilic interaction liquid chromatography) or ion-pairing reversed-phase chromatography provide the necessary sensitivity and selectivity. Stable isotope-labeled AICAR (13C or D-labeled) serves as an internal standard. Intracellular ZMP levels are typically measured from acid-extracted cell lysates, with concentrations ranging from 0.1-5 mM depending on AICAR dose, treatment duration, and cell type. Monitoring the ZMP:AMP ratio provides a functional readout of AICAR uptake and phosphorylation efficiency.

The following publications represent key research on AICAR and AMPK pharmacology across metabolic, cardiovascular, and exercise physiology research areas.

• Read more: TRH (Thyrotropin-Releasing Hormone): Research Guide & Chemical Profile → https://www.chemverify.com/learn/trh-thyrotropin-releasing-hormone-research-guide
• Read more: Ipamorelin + CJC-1295 (No DAC) Stack: Synergy Research Guide → https://www.chemverify.com/learn/ipamorelin-cjc-1295-no-dac-stack-synergy
• Read more: TP508 (Chrysalin): Research Guide & Chemical Profile → https://www.chemverify.com/learn/tp508-chrysalin-research-guide-chemical-profile
• Read more: Semax for Cognitive Research: ACTH(4-10) Analog Mechanism → https://www.chemverify.com/learn/semax-cognitive-research-acth-mechanism