Figure 3.

Energy- and nutrient-sensing transcription factor–regulated pathways. During caloric excess and obesity, anabolic processes are stimulated via the insulin/IGF-1 and TOR pathways. Additionally, caloric excess suppresses catabolic processes via a decrease in the AMP/ATP ratio, leading to reduced activation of AMPK and downstream activity of PGC1α, sirtuins, and FOXO. Simultaneously, decreased NAD⁺ levels reduce sirtuin activity, inhibiting PPARγ activity and increasing HIF1α activity. Alternatively, during caloric restriction and fasting, catabolic processes are stimulated by the increase in AMP/ATP ratio and consequential activation of AMPK. AMPK also reduces anabolic processes through TOR inhibition. AKT, v-Akt murine thymoma viral oncogene homolog.