Calorie restriction and NAD⁺/sirtuin counteract the hallmarks of aging

Among diverse environmental factors that modify aging, diet has a profound effect. Calorie restriction (CR), which entails reduced calorie consumption without malnutrition, is the only natural regimen shown to extend maximum and mean lifespan, as well as healthspan in a wide range of organisms. Although the knowledge about the biological mechanisms underlying CR is still incipient, various approaches in biogerontology research suggest that CR can ameliorate hallmarks of aging at the cellular level including telomere erosion, epigenetic alterations, stem cells depletion, cellular senescence, mitochondrial dysfunction, genomic instability, proteostasis imbalance, impaired nutrient sensing and abnormal intercellular communication. Currently, the NAD + /sirtuin pathway is one of the few mechanisms described to mediate CR effects and sirtuin-activating compounds (STACs) mimic many effects of CR. Herein, we discuss the effects of CR on healthspan with emphasis on neuroprotection, how CR counteracts cellular aging, how sirtuin pathways intertwine with CR, and the relevance of STACs in mimicking CR effects.