Figure 1.

Pathways involved in stem cell hemostasis via regulation of nutrient sensing. The LKB1/AMPK pathway senses cellular energy levels and, when low, activates glucose uptake and inhibits mTOR. SIRT1 senses when NAD⁺ levels become high (oxidative environment) and activates the expression of FOXO proteins, which activate genes to combat oxidative stress. The PI3K/AKT pathway is activated by insulin or other growth factors to culminate in protein synthesis through mTOR, which can also be activated by glucose and amino acids. Items in red denote inhibitory paths or processes.