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Figure 4. Key regulatory pathways involved in the aging process. Extracellular signals (nutrients, growth factors) and intracellular signals (genomic instability, mitochondrial dysfunction, and oxidative stress) initiate aging-associated signaling events. Cellular glucose uptake acts through the AMPK pathway, while growth factors, insulin, and insulin-like growth factors bind to their respective receptors and transmit signals through the Ras and PI3K-AKT pathways. Similarly, intracellular oxidative stress (ROS) and DNA damage-associated stress signals activate the PI3K, NFκB, SIRT1, and FOXO pathways. These pathways, either directly or through mTORC1, modulate cellular processes (elevated inflammation, reduced cell growth and proliferation rate, and inhibition of autophagy), leading to the aging phenotype.