Aicar vs LC120

Aicar

AICAR, also called acadesine, is 5-aminoimidazole-4-carboxamide riboside: a synthetic nucleoside, not a peptide or an amino-acid derivative. Its monophosphate, ZMP, is a natural intermediate in the pathway cells use to build purine nucleotides. AICAR became a standard laboratory tool because cells convert it to ZMP, which mimics AMP and switches on AMP-activated protein kinase (AMPK). A large body of cell and rodent work has used it to study energy sensing, glucose uptake and fatty-acid metabolism. Human clinical work has been limited and has not centred on metabolism. A known weakness of the tool is that ZMP acts on other AMP-sensitive enzymes too, so not every effect attributed to AICAR runs through AMPK.

LC120

LC120 is a proprietary nutrient mixture, reported to contain L-carnitine, methionine, inositol and choline, rather than a single compound. The proportions of each ingredient have not been confirmed from published sources, and a mixture has no single formula or molecular weight. Each named component has a defined place in metabolism: L-carnitine carries long-chain fatty acids into mitochondria, methionine is an essential amino acid and the precursor of the methyl donor S-adenosylmethionine, choline is a precursor of phosphatidylcholine and acetylcholine, and inositol forms the core of the phosphoinositide lipids. The mixture itself has no published literature, so everything that can be said about it comes from studies of the components taken separately.

How Aicar acts

AICAR enters cells through adenosine transporters and is phosphorylated by adenosine kinase to ZMP. ZMP binds the regulatory gamma subunit of AMPK at sites that normally sense AMP, and this allosteric activation, together with increased phosphorylation of the catalytic alpha subunit, raises the kinase's activity. Activated AMPK phosphorylates targets such as acetyl-CoA carboxylase, shifting cells away from lipid synthesis and toward processes that generate ATP. ZMP accumulates to high concentrations, however, and has been reported to affect other AMP-regulated enzymes, including fructose-1,6-bisphosphatase and glycogen phosphorylase. Studies that need to separate AMPK-dependent effects often pair AICAR with genetic knockout models.

How LC120 acts

No mechanism has been described for the mixture, and its components are not known to share a target. L-carnitine is the substrate of the carnitine shuttle, which moves long-chain acyl groups into the mitochondrial matrix, where they undergo beta-oxidation. Methionine is converted to S-adenosylmethionine, the main methyl donor for the methylation of DNA, proteins and lipids. Choline provides the polar head group of phosphatidylcholine, which the liver needs to assemble and export very-low-density lipoproteins. Myo-inositol, the usual form of inositol, is incorporated into phosphatidylinositol and its phosphorylated derivatives, which carry signals inside cells. Whether the components alter each other's behaviour in combination has not been studied.

The records side by side

• Type: Aicar, Nucleoside analogue; LC120, Identity not established
• Molecular weight: Aicar, 258.23 g/mol; LC120, not recorded
• Molecular formula: Aicar, C9H14N4O5; LC120, not recorded

Reading a comparison

A comparison places two records side by side; it does not merge them. Each description above is drawn from that compound's own record, and the two were not necessarily characterised by the same methods, at the same time, or to the same level of detail. Before comparing any attribute, it is worth establishing that both records describe the substance you think they describe — names are not identifiers, and two entries sharing a name can differ in salt form, stereochemistry or the convention used to state a mass. Where a figure carries no method beside it, the comparison is between two reported numbers rather than between two measurements.