
Originally Posted by
Deep_Fried
Ditto.
Metformin is a good GDA and mediator of decreased insulin secretion for dieting.
However, it actually has a significant negative impact on hypertrophy via decreased Insulin, decreased hepatic IGF-1, raised IGF1BP, as well as inhibition of the signaling pathways mediated via IGF-1 that activate mTOR.
A snipet about Metformin from Datbtrue:
Metformin
Metformin chronically activates AMP-activated kinase (AMPK). AMPK slows '> liver glucose output by down-regulating expression of glucose-6-phosphatase and phosphoenolpyruvate carboxykinase; in skeletal muscle, it boosts the efficiency of '> insulin-stimulated glucose uptake by increasing expression of GLUT-4. These effects mandate a down-regulation of '> insulin secretion.
The resulting reduction of '> liver insulin activity will suppress '> liver production of '> IGF-I while boosting that of IGFBP-1, thereby decreasing plasma free '> IGF-I.
Stimulation of AMPK with Metformin also interferes with the Ras–Raf–MEK–ERK pathway of '> IGF-I signaling by inhibiting the ability of '> IGF-I to activate ras and its downstream targets.
Stimulation of AMPK with Metformin also blocks the ability of the PI3K-Akt pathway to activate mTOR.
Since the Ras–Raf–MEK–ERK cascade, as well as mTOR and its downstream targets, are key mediators of '> IGF-I’s ability to increase hypertrophy a systemic increase in AMPK activity as brought about by Metformin will hinder the potential for hypertrophy not only by diminishing plasma levels of '> insulin and free '> IGF-I, but also by intervening in the post-receptor intracellular pathways mediated events which bring about these '> bodybuilding effects.