AICAR Research Guide

Overview

AICAR (5-Aminoimidazole-4-carboxamide ribonucleoside, also referred to in the literature as AICA riboside or acadesine) is a naturally occurring purine nucleoside analog and a widely used laboratory tool compound for studying AMP-activated protein kinase (AMPK) signaling. Its molecular formula is C₉H₁₄N₄O₅, with a molecular weight of approximately 258.2 g/mol, and it is registered under CAS number 2627-69-2. AICAR is a naturally occurring intermediate in de novo purine biosynthesis, meaning it is present endogenously in cells at low concentrations before being incorporated into inosine monophosphate synthesis.

Note on nomenclature: published pharmacology literature has observed that the compound most commonly studied and referred to as “AICAR” in cell and animal research is more precisely the riboside (AICA riboside), while the term “AICAR” was originally reserved for the phosphorylated ribotide form (ZMP) that occurs naturally as a purine synthesis intermediate. This guide follows common laboratory usage in referring to the riboside compound as AICAR, consistent with the majority of the published literature. Available for research at Iron Peak Peptides: AICAR.

Since its introduction as a pharmacological AMPK activator in the mid-1990s, AICAR has become one of the most extensively cited tool compounds in skeletal muscle metabolism, exercise physiology, and cellular energy-sensing research, cited in more than 1,700 published articles indexed on PubMed relating to AMPK research alone.

Molecular Profile & Structure

Structurally, AICAR consists of an imidazole ring bearing an amino group and a carboxamide substituent, linked to a ribofuranose sugar moiety — a structural arrangement that closely parallels adenosine monophosphate (AMP), the endogenous energy-status signaling molecule that AICAR is designed to mimic pharmacologically. Upon entry into cells, AICAR is phosphorylated by adenosine kinase to form the monophosphate metabolite ZMP, which is the active intracellular species responsible for AICAR’s downstream pharmacological effects.

• Common names: AICAR, AICA riboside, acadesine
• Chemical class: Purine nucleoside analog / AMPK activator
• Molecular formula: C₉H₁₄N₄O₅
• Molecular weight: Approximately 258.23 g/mol
• CAS number: 2627-69-2
• Active intracellular metabolite: ZMP (AICAR monophosphate), an AMP-mimetic nucleotide
• Appearance: White to off-white crystalline or lyophilized powder
• Storage: Store lyophilized material at -20°C, protected from moisture and light. Reconstituted solutions should be stored at 2-8°C and used within the timeframe established by the supplying laboratory; repeated freeze-thaw cycling should be avoided to preserve compound integrity.

Mechanism of Action

The pharmacological activity of AICAR is proposed to derive primarily from its intracellular conversion to ZMP, a nucleotide monophosphate that structurally mimics AMP. Because AMPK is allosterically regulated by the cellular AMP:ATP ratio — a key indicator of cellular energy status — ZMP accumulation is described in the literature as activating AMPK independently of an actual change in the cell’s true energy charge, effectively creating a pharmacological “low energy” signal without requiring ATP depletion.

Once activated, AMPK phosphorylates a range of downstream substrates involved in cellular metabolism, including acetyl-CoA carboxylase (ACC), which regulates fatty acid oxidation, and components of the mTOR signaling pathway, which governs anabolic processes including protein synthesis. In skeletal muscle research specifically, AICAR-induced AMPK activation has been described as promoting GLUT4 transporter translocation to the plasma membrane, thereby increasing glucose uptake independent of insulin signaling — a mechanism of particular interest to researchers studying insulin-independent glucose disposal pathways.

Published research has also identified AMPK-independent effects of AICAR, including direct modulation of AMP-sensitive enzymes such as fructose-1,6-bisphosphatase and glycogen phosphorylase, as well as interactions with adenosine receptor signaling. A 2021 systematic review specifically catalogued these AMPK-independent mechanisms, noting that a substantial portion of AICAR’s reported cellular effects in the published literature may not be attributable to AMPK activation alone, a distinction that is important for researchers designing mechanistic studies using this compound (Guigas & Viollet, 2021).

In a widely cited mouse study, AICAR administration was shown to synergize with (and, notably, to independently replicate some effects of) PPARδ pathway activation, driving transcriptional reprogramming of skeletal muscle toward an oxidative, fatigue-resistant fiber phenotype, and increasing markers of mitochondrial biogenesis even in the absence of an exercise stimulus, positioning AMPK activation as a molecular node connecting cellular energy sensing to exercise-associated adaptations (Narkar et al., 2008).

Key Research Findings

Early foundational work by Merrill and colleagues characterized AICAR’s effects on skeletal muscle glucose transport, reporting that AICAR administration stimulated glucose uptake and GLUT4 translocation in isolated rat skeletal muscle preparations through a mechanism distinct from insulin signaling, establishing AICAR as a pharmacological tool for dissecting insulin-independent glucose transport pathways (Merrill et al., 1997).

Narkar and colleagues, in a study published in Cell, reported that four weeks of AICAR administration alone was sufficient to increase running endurance by approximately 44% in sedentary mice, without any accompanying exercise training, through genetic reprogramming of skeletal muscle metabolism involving both AMPK activation and PPARδ-dependent transcriptional changes. This study is among the most frequently cited references establishing AICAR’s characterization in the literature as a pharmacological “exercise mimetic” tool compound (Narkar et al., 2008).

Jørgensen and colleagues examined the role of specific AMPK catalytic subunit isoforms in mediating AICAR-stimulated glucose uptake in skeletal muscle, using genetically modified mouse models to demonstrate that the AMPKα2 isoform is required for the full glucose-uptake response to AICAR, refining the mechanistic understanding of isoform-specific AMPK signaling (Jørgensen et al., 2004).

A 2021 systematic review by Guigas and Viollet comprehensively catalogued both AMPK-dependent and AMPK-independent effects of AICAR reported across the published literature, concluding that while AICAR remains among the most widely used AMPK activators in laboratory research, careful interpretation of experimental results requires accounting for its off-target, AMPK-independent activities (Guigas & Viollet, 2021).

Additional published research has examined AICAR’s antiproliferative effects in cultured cancer cell lines, including retinoblastoma cells, reporting that AICAR-induced AMPK activation was associated with decreased cyclin expression, S-phase cell cycle arrest, and increased apoptosis in vitro, extending AICAR’s research utility beyond metabolic and muscle physiology into cell cycle and proliferation research (retinoblastoma cell line study, 2013).

Research Applications

AICAR is used extensively across cellular and molecular biology research as a pharmacological activator of AMPK signaling. Core research applications include studies of skeletal muscle glucose transport and insulin-independent metabolic signaling, investigations into the transcriptional and mitochondrial biogenesis pathways associated with exercise adaptation, and mechanistic dissection of AMPK’s role as a cellular energy sensor across diverse tissue and cell-line models.

Because AICAR activates AMPK without requiring genetic manipulation or an exercise stimulus, it is frequently used in comparative pharmacology research alongside other AMPK-pathway modulators (such as metformin) to distinguish AMPK-dependent from AMPK-independent cellular responses, and alongside PPARδ agonists in exercise-mimetic research paradigms examining fiber-type switching and endurance-related gene expression programs.

AICAR is also employed as a tool compound in cancer cell biology research examining AMPK’s role in regulating cell proliferation, cell cycle progression, and apoptosis, as well as in broader cellular stress-response research given AMPK’s central role integrating nutrient and energy status signals with downstream autophagy and catabolic pathways. Researchers frequently pair AICAR with genetic AMPK knockdown or knockout models to help distinguish AMPK-mediated effects from the AMPK-independent activities documented in the systematic review literature.

References

1. Merrill GF, Kurth EJ, Hardie DG, Winder WW. (1997). AICA riboside increases AMP-activated protein kinase, fatty acid oxidation, and glucose uptake in rat muscle. American Journal of Physiology.
2. Narkar VA, Downes M, Yu RT, et al. (2008). AMPK and PPARδ agonists are exercise mimetics. Cell.
3. Jørgensen SB, et al. (2004). Knockout of the α2 but not α1 5′-AMP-activated protein kinase isoform abolishes 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside but not contraction-induced glucose uptake in skeletal muscle. Journal of Biological Chemistry.
4. Guigas B, Viollet B. (2021). AICAr, a Widely Used AMPK Activator with Important AMPK-Independent Effects: A Systematic Review. Cells.
5. Aminoimidazole Carboxamide Ribonucleotide (AICAR) Inhibits the Growth of Retinoblastoma Cells In Vitro. (2013). Investigative Ophthalmology & Visual Science.