Bioregulators, FOXO4 Peptides and Mitochondrial-Derived Peptides

The bioregulators are di- to tetrapeptides described by Khavinson and colleagues, named after the tissue extract each was modelled on: epithalon (Ala-Glu-Asp-Gly), pinealon (Glu-Asp-Arg), cartalax, livagen and others. The proposed mechanism is direct interaction with DNA or histone proteins and changes in gene expression, reported in cell culture. Studies of epithalon report telomerase activity in cultured cells, measured by the TRAP assay.

FOXO4-DRI is a D-retro-inverso peptide built from the reversed sequence of a FOXO4 segment in D-amino acids, which makes it resistant to proteases. It is designed to disrupt the binding of FOXO4 to p53 and is studied in senescent cell culture models. SS-31 (elamipretide) is a Szeto-Schiller tetrapeptide, D-Arg-Dmt-Lys-Phe-NH2, that concentrates at the inner mitochondrial membrane by binding cardiolipin.

MOTS-c is a 16-residue peptide encoded by a short open reading frame in the mitochondrial 12S rRNA gene; studies in cell culture report AMPK activation and translocation to the nucleus. Humanin is a 24-residue peptide encoded in the 16S rRNA region that binds IGFBP-3 and a receptor complex including gp130, and is studied in cytoprotection assays in cultured cells.

Identity is established by mass spectrometry: an intact mass, or a precursor and fragment transition (MRM) matched against a reference standard, confirms that the sequence in the vial is the one on the label. Purity is a chromatographic figure, the principal peak area by reversed-phase HPLC, and it bounds peptide-related impurities only; it says nothing about counterion, water or residual solvent content, which is why net peptide content is reported separately. Lyophilised material is stored cold, dry and dark, and a certificate states what was measured on one named lot. Very short peptides such as the bioregulators are poorly retained on standard reversed-phase columns, so method choice matters, and their low masses make a specific MS transition essential to tell them from contaminants. Much of the bioregulator literature comes from a single research network, which is the main caveat when reading it.