Peroxisome proliferator-activated receptor γ coactivator 1 in caloric restriction and other models of longevity

Dietary restriction of calories (caloric restriction [CR]) increases longevity in phylogenetically diverse species. CR retards or prevents age-dependent deterioration of tissues and an array of spontaneous and chemically induced diseases associated with obesity including cardiovascular disease, diabetes, and cancer. An understanding of the molecular mechanisms that underlie the beneficial effects of CR will help identify novel dietary, pharmacological, and lifestyle strategies for slowing the rate of aging and preventing these diseases as well as identify factors which modulate chemical toxicity. Here, we review the involvement of transcriptional coactivator proteins, peroxisome proliferator-activated receptor (PPAR) gamma coactivator 1 (PGC-1) alpha and beta, and regulated nuclear receptors (NR) in mediating the phenotypic changes found in models of longevity which include rodent CR models and mouse mutants in which insulin and/or insulin-like growth factor-I signaling is attenuated. PGC-1 alpha is transcriptionally or posttranslationally regulated in mammals by: 1) forkhead box "other" (FoxO) transcription factors through an insulin/insulin-like growth factor-I-dependent pathway, 2) glucagon-stimulated cellular AMP (cAMP) response element binding protein, 3) stress-activated kinase signaling through p38 mitogen-activated protein kinase, and 4) the deacetylase and longevity factor sirtuin 1 (SIRT1). PGC-alpha and PGC-beta regulate the ligand-dependent and -independent activation of a large number of NR including PPAR alpha and constitutive activated receptor (CAR). These NR regulate genes involved in nutrient and xenobiotic transport and metabolism as well as resistance to stress. CR reverses age-dependent decreases in PGC-alpha, PPAR alpha, and regulated genes. Strategies that target one or multiple PGC-1-regulated NR could be used to mimic the beneficial health effects found in models of longevity.