MTOR and chronic obstructive pulmonary disease: The age-related changes may be abnormally augmented in COPD patients due to several factors, such as telomere shortening, cellular senescence, activation of the phosphatidylinositol-3-kinase (PI3K)/mammalian target of rapamycin (mTOR) signaling pathway, defective DNA repair, abnormal microRNA patterns, epigenetic alterations, decreased anti-aging molecules, mitochondrial dysfunction, impaired autophagy, senescence, and progenitor cell exhaustion (Barnes 2017; Hikichi et al. 2019).