What Is AICAR?
AICAR, also known as acadesine or AICA-riboside, is a synthetic purine nucleoside analog. Its chemical structure contains an aminoimidazole carboxamide group attached to a ribose sugar, giving AICAR the basic structure of a nucleoside.
AICAR is also known by the chemical name 5-aminoimidazole-4-carboxamide riboside. It is a small-molecule compound, not a peptide- or protein-based molecule.
Research Overview Table
Chemical and Molecular Characteristics
AICAR is an imidazole nucleoside analog consisting of a 5-aminoimidazole-4-carboxamide group linked to a β-D-ribofuranoside. This structure gives the compound its characteristic ribonucleoside architecture.
Its molecular structure contains an imidazole ring and a ribose sugar, with the aminoimidazole carboxamide group forming the characteristic base portion of the molecule. These structural features distinguish AICAR from peptide-based compounds and other molecular classes.
Certificates:
Mechanism of Action Under Investigation
AICAR enters cells and is phosphorylated to form 5-aminoimidazole-4-carboxamide ribonucleotide (ZMP). ZMP is an intermediate in purine biosynthesis and can mimic AMP in its interaction with AMP-activated protein kinase (AMPK). Early studies showed that ZMP can directly activate AMPK and promote its phosphorylation without the changes in cellular ATP, ADP, and AMP normally associated with other ways of activating the enzyme.
Once AMPK is activated, AICAR treatment has been associated with changes in several downstream targets. Early studies reported reduced activity of HMG-CoA reductase, lower fatty acid and sterol synthesis, and inhibition of isoprenaline-stimulated lipolysis. These findings helped establish AICAR as a useful tool for studying AMPK-regulated pathways.
AICAR does not, however, act exclusively through AMPK. Later research has identified several AMPK-independent effects of AICAR and ZMP, including effects on mitochondrial oxidative phosphorylation and other cellular signaling pathways. For that reason, responses produced by AICAR cannot always be attributed to AMPK activation alone.
Scientific Research Context
AICAR has played an important role in experimental research as a pharmacological tool for studying cellular energy and metabolic regulation. Researchers have used it to examine how changes in energy status influence intracellular signaling and metabolic processes. Its research history began with studies of AMP-sensitive cellular regulation and later expanded into broader investigations of metabolism, exercise, cardiovascular function, nucleotide metabolism and cancer biology.
AICAR Biology and Biological Pathways
Primary Biological Function
AICAR has been used as an experimental tool to study how cells respond when their energy balance changes. Research has focused on how cells adjust energy use and metabolism during periods of metabolic stress. AICAR became widely used in this area because it can influence AMPK, an enzyme involved in regulating cellular energy balance.
Relevant Metabolic or Signaling Pathways
AICAR has been studied in pathways involved in cellular energy sensing and metabolic regulation. Its best-established signaling connection is AMPK, which responds to changes in cellular energy status. Research has also examined AICAR-related effects on purine and pyrimidine metabolism, as well as other cellular signaling pathways. However, these effects cannot always be attributed to AMPK because AICAR and its metabolite ZMP can produce AMPK-independent responses.
Tissue-Specific Biology
Skeletal muscle has been one of the primary tissues used in AICAR research, particularly in studies of glucose uptake, glycogenolysis, fatty acid oxidation, protein synthesis, and exercise. Liver studies have examined gluconeogenesis, fatty acid oxidation, and cholesterol synthesis. Cardiac investigations have focused on ischemia and adenosine metabolism. Leukemia and other cancer models have been used to study cell proliferation, differentiation, and nucleotide metabolism. Together, these studies show how the same compound has been used to investigate distinct metabolic processes in different tissues.
Experimental Biomarkers
AICAR research has measured changes in glucose uptake, glycogen breakdown, fatty acid oxidation, and protein synthesis, especially in skeletal muscle. Liver studies have tracked gluconeogenesis and cholesterol synthesis, while cardiac studies have examined adenosine metabolism. In leukemia and cancer models, researchers have measured cell growth, cell differentiation, and nucleotide metabolism. These measurements help scientists compare biological activity in different tissues.
Laboratory Investigation Methods
Researchers have studied AICAR in cultured cells, isolated tissues, animal models, and a limited number of human studies. Laboratory methods have included Western blotting to measure protein phosphorylation, gene expression analysis, metabolomic profiling, biochemical assays, cell proliferation assays, and cell-cycle analysis. Some studies have also used genetic models and metabolite profiling to examine changes in purine and pyrimidine metabolism.
Experimental Models Used in Published Research
Researchers have studied AICAR using several experimental models, including cultured cells, isolated tissues, animal models, genetically modified animals, and human studies. Researchers use these models because each provides a different level of biological complexity and allows AICAR-related effects to be examined under different experimental conditions.
Cell Culture Models
Cell-based models have been used extensively in AICAR research. Studies have included skeletal muscle cells, hepatocytes, cardiomyocytes, fibroblasts, endothelial cells, leukemia cells, glioma cells, and myeloma cells. These experiments have measured glucose metabolism, fatty acid metabolism, nucleotide metabolism, cell proliferation, and cell differentiation. Their main limitation is that isolated cells cannot reproduce whole-body physiology.
Isolated Tissue Models
Researchers have used isolated tissue preparations mainly in skeletal muscle and cardiac studies. These models allow researchers to study intact tissue outside the whole organism. However, isolated tissue systems cannot reproduce interactions between different organs.
Animal Models
Mouse and rat models make up a substantial part of the AICAR research literature. These models allow researchers to study AICAR in an intact organism and examine responses across multiple tissues.
Genetically Modified Models
Knockout and transgenic mice have been used to distinguish between biological effects that depend on specific molecular pathways and those that do not. These models have been particularly useful for examining pathway-dependent and pathway-independent effects. Genetically modified models may also differ from normal physiology, which should be considered when interpreting the findings.
Human Studies
Human studies of AICAR have included healthy volunteers, patients undergoing coronary artery bypass graft surgery, patients with chronic stable angina, and patients with hematological malignancies. These studies have examined pharmacokinetics, myocardial ischemia, vascular responses, and drug safety. Human studies represent a smaller part of the AICAR literature, with most published research based on cell and animal models.
AICAR Published Scientific Research
Metabolic Research
Metabolic research has examined how AICAR affects glucose and lipid metabolism. Studies have reported changes in glucose uptake, glycogen metabolism, fatty acid oxidation, glucose oxidation, gluconeogenesis, lipogenesis, and cholesterol synthesis. In skeletal muscle, AICAR has been shown to increase glucose uptake and fatty acid oxidation, while studies in liver cells have found that AICAR can inhibit gluconeogenesis. Other research has examined its effects on glucose metabolism at the whole-body level.
Exercise Physiology Research
Exercise research has examined how AICAR affects skeletal muscle and how its effects compare with those of exercise. Studies have looked at glucose transport, glycogen metabolism, fuel use, GLUT4 expression, and exercise-related metabolic changes. Research comparing AICAR with exercise has also found that AICAR does not reproduce every metabolic response produced by physical activity.
Hypoxia and Cardiac Research
Research in hypoxia and cardiac biology has examined AICAR in relation to myocardial ischemia and cardiac metabolism. Studies have investigated glucose uptake and GLUT-4 translocation in cardiac muscle during hypoxia and ischemic conditions, as well as changes in myocardial function and metabolism. Human studies have also examined AICAR in exercise-induced and pacing-induced myocardial ischemia and during coronary artery bypass surgery.
Purine and Pyrimidine Metabolism Research
AICAR research has also examined the relationship between AICAR-related metabolism and nucleotide synthesis. Studies have investigated changes in purine and pyrimidine nucleotide pools and how these changes affect cellular metabolism. Research in leukemia cells, for example, found that AICAr altered nucleotide pools and disrupted pyrimidine biosynthesis, producing downstream effects on RNA transcription, DNA replication, and cell survival.
Cancer and Leukemia Research
Cancer research has examined how AICAR affects cancer cell growth, survival, differentiation, cell-cycle progression, cellular metabolism, and nucleotide metabolism. Studies in acute lymphoblastic leukemia found that AICAR inhibited cell proliferation and induced apoptosis, with nucleotide-pool disturbances contributing to these effects. Research in acute myeloid leukemia has also found that AICAR can induce differentiation in a subset of primary leukemia cells.
Limitations of Current Research
Evidence Is Predominantly Preclinical
AICAR has been investigated in hundreds of studies, but most of the evidence has come from cultured cells, isolated tissues, animal models, and transgenic mice. Human studies have been limited to a small number of clinical investigations involving healthy volunteers, coronary artery bypass graft surgery, chronic stable angina, and a few hematological disorders. The published literature therefore remains heavily dependent on experimental models rather than clinical research.
Human Clinical Evidence
Human studies of AICAR have been limited to a small number of investigations in healthy volunteers and selected patient populations, including coronary artery disease, chronic stable angina, chronic lymphocytic leukemia, and myelodysplastic syndrome. Most studies were early-phase clinical trials with relatively short treatment periods. In addition, several cardiovascular findings reported in earlier studies were not confirmed in later trials.
Species Differences
AICAR research has been conducted in several experimental systems, including cultured cells, isolated tissues, mice, rats, dogs, and humans. Researchers later re-examined many metabolic findings in transgenic and knockout mouse models. At the same time, the number of human studies remained relatively small. As a result, observations reported in experimental models cannot always be compared directly across species.
Study Design Limitations
Several reported effects of AICAR were found to be AMPK-independent. The literature therefore recommends caution when interpreting studies that rely on AICAR alone. Studies in transgenic mice and models with AMPK downregulation or knockout have been used to re-examine these observations.
Independent Replication
Many early findings were later re-examined in transgenic mice and in cells with AMPK overexpression or downregulation. The literature also recommends combining AICAR with other AMPK agonists and appropriate methods for AMPK downregulation when evaluating AMPK-dependent effects.
Long-Term Evidence
The literature provides very little information about long-term exposure in humans. The review specifically notes poor oral bioavailability and discusses several short-term clinical studies, but it does not identify a large body of long-duration human research. As a result, long-term evidence remains limited.
Analytical Documentation
HPLC is used to assess purity and to detect impurities in AICAR samples. LC-MS is used to confirm molecular identity and to quantify the compound in research samples. NMR, when available, is used to confirm the molecular structure.
Analytical results are typically reported in a Certificate of Analysis (CoA), which includes batch-specific information such as identity, purity, and molecular weight.
Analytical verification is important because it confirms that the material used in laboratory research matches the expected chemical composition. Analytical documentation verifies product identity and quality rather than biological performance.
Storage and Laboratory Handling
Store AICAR according to the product specifications provided for the selected batch and formulation. Only qualified personnel may handle the material, and they must follow standard laboratory procedures during storage and preparation. Use clean laboratory equipment and handling practices to prevent contamination. AICAR is intended for laboratory research use only.
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