The Effects of Fortetropin® on Anabolic and Catabolic Signaling in Skeletal Muscle (MoA Study)
Fortetropin®, a natural bioactive ingredient derived from fertilized chicken egg yolk isolate, augmented gains in muscle growth in resistance trained humans compared to exercise alone. This study investigated the impact of Fortetropin® on protein synthesis and markers of protein degradation in rats after acute exercise. Male wistar rats were fed for 8 days with either 1.2 ml of tap water (control) or 0.39 g Fortetropin® (MYOS RENS Technology Inc.). Rats then underwent an electrically-stimulated lower body unilateral plantarflexion exercise regimen. Muscles in the non-exercised and exercised limbs were harvested at 180 minutes following exercise and analyzed for gene and protein expression in myostatin, mTOR and ubiquitin signaling pathways. Activin IIB receptor mRNA was significantly lowered in the exercise + Fortetropin® group, but not the exercise + control group indicating depression of the myostatin pathway via decreasing receptor expression (p<0.05). An increase in both Ubiquitin monomer protein expression and polyubiquitination, both indicators of protein degradation, were greater in the control + exercise, but not Fortetropin® + exercise (p<0.05). The mRNA expression of the rate limiting E3 ligase Atrogin-1 was depressed in the Fortetropin® + exercise compared to control + exercise (p<0.05). mTOR signaling was elevated as indicated by greater phosphorylation status of 4EBP1, rp6, and p70S6K for both groups. The Fortetropin® + exercise resulted in significant elevations of these markers compared to the control group (p<0.05). Fortetropin® supplementation reduced mRNA expression of the myostatin receptor, Activin IIB. Fortetropin® also appears to promote muscle growth via increasing anabolic (mTOR) and decreasing catabolic (ubiquitin) signaling.