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20.05.2011


PEG-IGF-1: improved IGF-1 analogue

Pharmaceutical giant Roche is experimenting with a new variation of the muscle-strengthening hormone IGF-1. Researchers at Roche will soon publish the results of a study that show that PEG-IGF-1 has fewer side effects that the regular IGF-1. And it probably helps chemical athletes achieve even better results too.

PEG-IGF-1
In August 2010 United States Application US20100210547 appeared, Roche’s patent on a new IGF-1 analogue. [US20100210547] Right after this the researchers submitted an article to the Journal of Biological Chemistry on the tests they had done with PEG-IGF-1 on cells and mice.

The structural formula of PEG-IGF-1 is shown above. The difference with regular IGF-1 is that the PEg-IGF molecule on lysine 68 is PEGylated. This means that a chain of polyethylene glycol units is attached to this location on the chain. The researchers discovered that this what gives PEG-IGF-1 other pharmacological properties.

One of IGF-1's undesirable effects is that it can reduce sugar levels dramatically. This is because IGF-1 imitates the effect of insulin: IGF-1 has its own receptor, but can also attach itself to the insulin receptor. The figure below shows that PEG-IGF-1 doesn't attach as easily to the insulin A and B receptor as IGF-1 does.


PEG-IGF-1: improved IGF-1 analogue


PEG-IGF-1: improved IGF-1 analogue


PEG-IGF-1 has the same effect on the muscle cells' glucose uptake as IGF-1 does. But PEG-IGF-1 results in less glucose uptake by fat cells than IGF-1. Incidentally, the researchers regard this as confirmation of a new theory: that IGF-1 is not as important for muscle cells as was previously thought, and that they require IGF-1 above all for the regulation of glucose uptake.

PEG-IGF-1 is not quite as good a ligand for the IGF-1 receptor as IGF-1 itself. But on the other hand, PEG-IGF-1 remains present for longer in the body, the researchers discovered when they injected mice with this substance. After injecting regular IGF-1, the hormone has almost disappeared from the system after 6 hours, while PEG-IGF-1 has hardly declined even after 48 hours.


PEG-IGF-1: improved IGF-1 analogue


PEG-IGF-1: improved IGF-1 analogue


PEG-IGF-1: improved IGF-1 analogue


The researchers stretched the tibialis anterior [the calf muscle] in ordinary mice [BL/10], and then measured the amount of strength it was capable of developing. The researchers then did the same with the calf muscle of mice with muscular dystrophy. Some of the mice were given a placebo, others received daily injections containing 1 mg IGF-1, and others were given injections containing 0.3 mg PEG-IGF-1.

Dystrophic muscles incur more damage when stretched. That pre-treatment with PEG-IGF-1 reduces the damage indicates that PEG-IGF-1 still has an anabolic effect, according to the researchers. They deduce this from test-tube studies on muscle cells, in which both hormones boosted muscle fibre synthesis equally.

"PEG-IGF-I represents an IGF-I variant with purely homeostatic anabolic properties apparently devoid of short-term side effects", the researchers conclude. "These beneficial properties result presumably from its ability to alter IGF homeostasis and its slower nature of downstream signaling cascade activation. These properties are propitious for safely providing benefit in catabolic conditions and enhancing muscle function."

Source:
J Biol Chem. 2011 Apr 1. [Epub ahead of print].

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