title: The Four Layers of Aging.
abstract: Instead of considering aging in terms of discrete hallmarks, we suggest that it operates in four layers, each at a different biological scale. Malfunctions within each layer-and connections between them-produce the aged phenotype and its associated susceptibility to disease.
authors.affiliation: State Key Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100005, P.R. China.
authors.forename: Ran
authors.initials: R
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100005, P.R. China. Electronic address: chenhouzao@ibms.cams.cn.
authors.forename: Hou-Zao
authors.initials: HZ
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100005, P.R. China. Electronic address: liudp@pumc.edu.cn.
authors.forename: De-Pei
authors.initials: DP
authors.lastname: Liu
keywords: Aging; adaptive response; age-related diseases; dietary/caloric restriction; evolutionary fitness