title: Dietary restriction involves NAD⁺ -dependent mechanisms and a shift toward oxidative metabolism.
abstract: Interventions that slow aging and prevent chronic disease may come from an understanding of how dietary restriction (DR) increases lifespan. Mechanisms proposed to mediate DR longevity include reduced mTOR signaling, activation of the NAD⁺ -dependent deacylases known as sirtuins, and increases in NAD⁺ that derive from higher levels of respiration. Here, we explored these hypotheses in Caenorhabditis elegans using a new liquid feeding protocol. DR lifespan extension depended upon a group of regulators that are involved in stress responses and mTOR signaling, and have been implicated in DR by some other regimens [DAF-16 (FOXO), SKN-1 (Nrf1/2/3), PHA-4 (FOXA), AAK-2 (AMPK)]. Complete DR lifespan extension required the sirtuin SIR-2.1 (SIRT1), the involvement of which in DR has been debated. The nicotinamidase PNC-1, a key NAD⁺ salvage pathway component, was largely required for DR to increase lifespan but not two healthspan indicators: movement and stress resistance. Independently of pnc-1, DR increased the proportion of respiration that is coupled to ATP production but, surprisingly, reduced overall oxygen consumption. We conclude that stress response and NAD⁺ -dependent mechanisms are each critical for DR lifespan extension, although some healthspan benefits do not require NAD⁺ salvage. Under DR conditions, NAD⁺ -dependent processes may be supported by a DR-induced shift toward oxidative metabolism rather than an increase in total respiration.
authors.affiliation: Department of Genetics and Complex Diseases, Division of Biological Sciences, Harvard School of Public Health, Boston, MA, USA; Section on Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Genetics, Harvard Medical School, Harvard Stem Cell Institute, Boston, MA, USA.
authors.forename: Natalie
authors.initials: N
authors.lastname: Moroz
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Carmona
authors.forename: Edward
authors.initials: E
authors.lastname: Anderson
authors.forename: Anne C
authors.initials: AC
authors.lastname: Hart
authors.forename: David A
authors.initials: DA
authors.lastname: Sinclair
authors.forename: T Keith
authors.initials: TK
authors.lastname: Blackwell
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D031204:Caloric Restriction; D004032:Diet; D008136:Longevity; D009243:NAD / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology; D015398:Signal Transduction; D037761:Sirtuins / Q000378:metabolism*; D014157:Transcription Factors
chemical_list: D029742:Caenorhabditis elegans Proteins; D014157:Transcription Factors; D009243:NAD; D037761:Sirtuins
keywords: C. elegans; NAD+; aging; dietary restriction; sirtuins; stress response