About Modesto Cordell
Compelling evidence has described that the incidence of hypertension and left ventricular hypertrophy (LVH) in postmenopausal women is significantly increased worldwide. Effect of glucose deprivation on induction of cell death in high testosterone- or… Effect of concomitant glucose deprivation and bicalutamide treatment on cell growth and cell… AR signaling and expression of mTOR regulators. AR signaling and expression of… The research team identified the next priority as determining whether the same abnormal nerve cell overactivity occurs in human SBMA patients. Additionally, genes responsible for activating nerve cells, especially glutamate receptors, were abnormally overactive in SBMA mice in the first week of life and caused motor neurons to become overactive.ND restored IGF-1 expression and Akt/mTORC1 signaling while repressing expression of FoxO transcriptional targets. Muscle AMPK and raptor phosphorylation, mTOR inhibitors, were not altered by low testosterone. TL induced expression of FoxO transcriptional targets, MuRF1, atrogin1 and REDD1. Therefore, the purpose of this study is to determine the effect of androgen availability on muscle Akt/mTORC1/FoxO3a regulation in skeletal muscle and cultured C(2)C(12) myotubes. T1 - Testosterone signals through mTOR and androgen receptor to induce muscle hypertrophy
However, S6K1 -/- skeletal muscle has high mitochondrial content accompanied by increased expression of mitochondrial genes, which protect against diet-induced obesity together with enhanced β-oxidation in white adipose tissue (WAT) (Um et al., 2004). On the other hand, rapamycin abolished the effects of testosterone-induced cardiac hypertrophy, decreased the systolic and diastolic blood pressure of SHR, and inhibited the activation of mTOR/S6K1/4EBP1 signaling pathway in a concentration-dependent manner. The purpose of this study was to evaluate the role of mammalian rapamycin receptor (mTOR) signaling pathway in myocardial hypertrophy in androgen-induced postmenopausal hypertension and whether mTOR inhibitors can protect the myocardium from androgen-induced interference to prevent and treat cardiac hypertrophy. Researchers at Nagoya University have found that a natural burst of testosterone right after birth causes a mutant protein to overactivate the nerve cells that control muscles (motor neurons) in newborn mice carrying the SBMA mutation.
In addition, follistatin, an inhibitor of myostatin, activates Akt/mTOR/p70S6K1/S6 signaling in muscle growth, which exists independently of myostatin-driven mechanisms (Winbanks et al., 2012), supporting the disconnection between myostatin and mTOR signaling. However, on the other hand, several studies suggested that mTOR signaling and myostatin signaling could separately regulate muscle growth. Hence, the studies suggested that myostatin attenuates protein synthesis in muscle by coordinating the crosstalk between myostatin-mediated and mTOR signaling. The knockdown of rictor itself inhibits muscle cell differentiation, and does not affect myostatin-induced pSmad2 and muscle differentiation. The depletion of raptor increases myostatin-induced Smad2 phosphorylation, followed by further inhibition of myostatin-induced muscle differentiation. Supporting the negative regulation of myostatin in mTORC1 signaling, genetic deletion of myostatin elevates the activities and the expression levels of Akt, p70S6K1, and S6 (Lipina et al., 2010). The deletion of myostatin in mice results in muscle hyperplasia and hypertrophy, and more than doubles skeletal muscle (McPherron et al., 1997).
The effect of AR siRNA knockdown on mTOR, TSC1 and TSC2 was studied in both the low and high testosterone conditions. In summary, the positive regulation of mTOR by AR was operative in low or high testosterone condition, and generally a strong AR signal would produce a more vibrant mTOR response. On the other hand, the phosphorylation of 4EBP-1 appeared to be much less sensitive. By comparing the results of Figures 1 and 2, it is evident that AR knockdown produced a much more pronounced decrease of AR activity than mTOR activity. This observation affirmed that the low testosterone condition is insufficient to support the full function of AR.
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