What Is IGF-1 DES (1-3)? Truncated IGF-1, Binding-Protein Escape and Research Use

Take human insulin-like growth factor 1 and delete the opening triplet Gly-Pro-Glu, and what remains is IGF-1 DES: 67 residues, 7,371.30 g/mol. That deletion takes away the glutamate on which the IGF binding proteins depend for tight contact, so the shortened protein moves and signals with little interference from the IGFBP system while still fully activating the IGF-1 receptor. Unusually for an analogue of this kind, IGF-1 DES (1-3) was not dreamt up in a laboratory — it was first recovered from bovine colostrum and brain tissue, and a specific N-terminal protease generates it in vivo.

Peptide Medix EU offers IGF-1 DES (1-3) as lyophilized powder in 0.1 mg and 1 mg vials, part of the IGF and muscle peptides range. It is sold for laboratory research only.

IGF-1 DES defined

Its name simply describes it: "des" is chemistry's prefix for something removed, and (1-3) names the residues that are absent. Native IGF-1 is a single 70-residue chain folded like proinsulin and held by three disulfide bridges, made largely by liver cells under the direction of growth hormone. IGF-1 DES is the identical chain beginning at residue 4, so its fold, disulfide arrangement and receptor-contact surface are untouched — all that is missing is the floppy tripeptide at the front.

It is catalogued under CAS 112603-35-7 with a molecular weight of 7,371.30 g/mol, about 278 Da less than the intact hormone. Being a 67-residue protein, it comes from recombinant expression rather than stepwise chemical assembly and is supplied as lyophilized powder.

Origin and structure

This molecule sits in an unusual dual role — a peptide that occurs naturally and, at the same time, a purpose-built research reagent. Researchers found it in bovine colostrum during the late 1980s, and afterwards in porcine uterus and in mammalian brain; an acid protease capable of clipping the Gly-Pro-Glu triplet off IGF-1 has been characterised. That same cleavage liberates GPE, or glypromate, which carries a modest neuroprotection literature of its own unconnected to the IGF-1 receptor — so the reaction yields two fragments of scientific interest, not an active molecule plus debris.

Functionally, the deletion matters only for contact with binding proteins. Position 3's glutamate forms an electrostatic interaction with the IGFBP surface, and removing it has been reported to cut binding-protein affinity by one to two orders of magnitude, varying with which IGFBP is assayed. Affinity for the receptor is essentially untouched; indeed some binding studies report IGF-1 DES engaging IGF-1R marginally more tightly than the intact protein does.

Mechanism of action

At the immediate level this is plain agonism at IGF-1R, a receptor tyrosine kinase with α2β2 architecture. Once bound, the β subunits autophosphorylate, insulin receptor substrate adaptors are recruited, and signalling proceeds down PI3K/Akt/mTOR — the branch linked in the literature to protein synthesis and survival endpoints — and down Ras/MEK/ERK, linked to proliferation.

Experimentally, what sets DES apart from the native hormone is availability rather than signalling. Put native IGF-1 into any system containing binding proteins — serum-supplemented medium, conditioned medium from IGFBP-secreting cultures, or real tissue — and most of it is captured and held. An equal number of moles of IGF-1 DES remains largely unbound. Where such systems report potency differences of several-fold, sometimes approaching tenfold, those figures reflect how much IGFBP the model contains, not an intrinsic difference between the molecules: strip the binding proteins out and the two perform alike.

A more subtle consideration applies to tissue in which IGFBPs are actively degraded. Where local proteases free IGF-1 from its carriers, the edge held by a binding-protein-evading analogue shrinks. This is among the reasons investigators deliberately choose between DES and the substitution-based analogue instead of treating them as interchangeable.

Research applications

Potency in culture and its IGFBP dependence

The most thoroughly documented work sets DES against native IGF-1 in cell systems that differ in binding-protein content. Cultures of fibroblasts, myoblasts and osteoblasts demonstrated that the potency gap grows as IGFBP levels climb — the observation that pinned down the mechanism. These are in-vitro experiments with defined endpoints such as thymidine uptake and receptor phosphorylation.

Skeletal muscle and satellite cell models

Studies in C2C12 cells and primary myoblasts have used IGF-1 DES to examine proliferation and differentiation signalling in settings where secreted IGFBP-5 and IGFBP-6 would otherwise cloud interpretation. The findings apply at cell level and say nothing about whole-organism outcomes.

Neural biology and colostrum-derived roles

Since the molecule is naturally present in brain tissue, a number of rodent studies have investigated DES(1-3) IGF-1 in models of neuronal survival and injury, frequently in parallel with the liberated GPE tripeptide. This work remains preclinical and exploratory.

Head-to-head analogue studies

IGF-1 DES is regularly compared with IGF-1 LR3, which achieves the same binding-protein escape by swapping in arginine at position 3 and appending an N-terminal extension. The pair differ in size, isoelectric point, reported clearance and conduct in proteolytically active tissue; the practical grounds for choosing between them appear in our IGF-1 LR3 versus IGF-1 DES comparison, with the engineering rationale covered in why these modifications exist.

Available formats and vial sizes

A 0.1 mg vial suits plate-scale culture work, where working concentrations fall in the nanogram-per-millilitre range, while the 1 mg vial is the sensible unit for an extended series that ought to run on one lot throughout. Our IGF-1 DES buying guide covers what to check in a supplier.

Reconstitution and storage at the bench

Treat IGF-1 DES as a recombinant protein, not as a short synthetic peptide. Because it dissolves poorly at neutral pH, the usual practice is to take it up in dilute acid — published product literature conventionally uses 10 mM hydrochloric acid or 0.1% acetic acid — before diluting into medium or assay buffer. Pipetting neutral buffer straight onto the cake risks incomplete dissolution and aggregation, which shows up as erratic activity rather than visible cloudiness.

The arithmetic is undemanding: bring a 1 mg vial to 1 mL and you have 1 mg/mL, equivalently 1,000 mcg/mL, so 0.1 mL of stock holds 100 mcg. Working solutions sit several dilutions lower, and at that point loss to tube walls becomes the dominant problem — the standard remedy is adding a carrier protein such as 0.1% bovine serum albumin. The general method is described in our reconstitution guide.

Keep sealed lyophilized vials at −20 °C or colder, shielded from light and moisture. Aliquot reconstituted stock immediately and freeze it, since repeated freeze-thaw is the principal practical hazard for a 7 kDa disulfide-bonded protein. Wider handling practice is covered in how to store peptides.

Purity and reading the certificate of analysis

A certificate for a recombinant product should offer more than a purity percentage. Mass spectrometry provides the identity check that counts most: an observed mass around 7,371 g/mol confirms the truncated analogue, roughly 7,649 g/mol would mean full-length IGF-1, and anything above 9,000 g/mol would mean the LR3 analogue. Since these three products are easily confused on a label yet unmistakable on a spectrum, that line rewards careful reading. An SDS-PAGE lane reveals things a reversed-phase trace can conceal, dimers and clipped species in particular, and endotoxin levels matter wherever the material enters cell culture. Our guide to reading a peptide certificate of analysis goes through each section.

Regulatory position

IGF-1 DES (1-3) is not authorised as a medicine in any country. Recombinant human IGF-1 (mecasermin) is an approved prescription treatment for a rare growth disorder, but that product is the complete 70-residue protein and a different substance from the truncated analogue sold here. Material on this site is intended for qualified laboratory staff and is neither a supplement nor a medicine, nor is it for human consumption. Anti-doping rules prohibit IGF-1 and its analogues in sport.

Related compounds and further reading

Its nearest comparators are IGF-1 LR3, the substitution-plus-extension analogue, and MGF, the E-domain peptide derived from the IGF-1 Ec splice variant — an entirely separate molecule that does not act at IGF-1R and addresses a different experimental question.