Cerebrolysin vs Selank

Cerebrolysin

Cerebrolysin is a mixture of short peptides and free amino acids made by controlled enzymatic digestion of pig brain protein. Because it is a mixture, it has no single sequence, formula or molecular weight; its composition is defined by the manufacturing process and by batch standardisation. Laboratory and animal studies have examined it for activity resembling that of neurotrophic factors. It has also been studied in human clinical trials, mainly in acute stroke, traumatic brain injury and dementia, and systematic reviews of those trials have reached differing conclusions. The biologically relevant components of the mixture have not been identified, which limits how far any single mechanism can be attributed to it.

Selank

Selank is a synthetic seven-residue peptide, Thr-Lys-Pro-Arg-Pro-Gly-Pro, made by adding Pro-Gly-Pro to the tetrapeptide tuftsin. Tuftsin is a fragment of the heavy chain of immunoglobulin G, studied in immunology for its actions on phagocytic cells; the Pro-Gly-Pro extension was added to slow enzymatic breakdown. Selank was developed in Russia, and most published work on it comes from Russian groups. That literature consists mainly of rodent behavioural and gene-expression studies, with some small clinical studies, many of them published in Russian-language journals. Independent work outside Russia is limited.

How Cerebrolysin acts

No single molecular target has been assigned to Cerebrolysin, since it contains many peptides and amino acids. Cell and animal studies have described activity resembling that of neurotrophic factors, the proteins that regulate neuronal survival and differentiation, and have examined markers of apoptosis, synaptic density and neurogenesis in rodent models of stroke, brain injury and neurodegeneration. Some papers have proposed involvement of specific signalling routes downstream of neurotrophic receptors. How much of the peptide content crosses the blood–brain barrier, and which components account for which reported observation, have not been established.

How Selank acts

No single receptor for Selank has been identified. Rodent studies have reported that it changes the expression of genes involved in GABAergic neurotransmission, and some experiments suggest it modulates GABA-A receptor function allosterically. It has also been reported to inhibit enkephalin-degrading enzymes in blood serum, to affect monoamine metabolism in the brain, and to alter the expression of cytokines including interleukin-6. Increased expression of brain-derived neurotrophic factor (BDNF) in the rat hippocampus has also been described. Much of this evidence comes from a small number of laboratories and awaits independent replication.

The records side by side

• Type: Cerebrolysin, Proprietary mixture; Selank, Synthetic tuftsin analog (heptapeptide)
• Length: Cerebrolysin, not recorded; Selank, 7 amino acids
• Molecular weight: Cerebrolysin, not recorded; Selank, 751.9 g/mol
• Molecular formula: Cerebrolysin, not recorded; Selank, C33H57N11O9

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.