Fibroblast Growth Factor-21 Is a Promising Dietary Restriction Mimetic
Panorama Research Institute, 1230 Bordeaux Dr, Sunnyvale, California, United States, 94089, 408-747-5201Rejuvenation Research (Impact Factor: 3.31). 11/2012; 15(6). DOI: 10.1089/rej.2012.1392
Dietary or caloric restriction (DR or CR), typically a 30-40% reduction in ad libitum or "normal" nutritional energy levels, has been reported to extend lifespan and healthspan in diverse organisms, including mammals. Although the lifespan benefit of DR in primates and humans is unproven, preliminary evidence suggests that DR confers healthspan benefits. A serious effort is underway to discover or engineer DR mimetics. The most straightforward path to a DR mimetic requires a detailed understanding of the molecular mechanisms that underlie DR and related lifespan-enhancing protocols. Increased expression of FGF21, a putative mammalian starvation master regulator, promotes many of the same beneficial physiological changes seen in DR animals, including decreased glucose levels, increased insulin sensitivity, and improved fatty acid/lipid profiles. Ectopic over-expression of FGF21 in transgenic mice (FGF21-Tg) extends lifespan to a similar extent as DR in a recent study. FGF21 may achieve these effects by attenuating GH/IGF1 signaling. Although FGF21 expression does not increase during DR, and therefore is unlikely to mediate DR, it does increase during short-term starvation in rodents which is a critical component of alternate day fasting, a DR-like protocol that also increases lifespan and healthspan in mammals. Various drugs have been reported to induce FGF21, including PPARa agonists such as fenoﬁbrate, the histone deacetylase inhibitor sodium butyrate, and AMP kinase activators metformin and AICAR. Of these, only metformin has been reported to extend lifespan in mammals, and the extent of benefit is less than that seen with ectopic FGF21 expression. Perhaps the most parsimonious explanation is that high, possibly unphysiological, levels of FGF21 are needed to achieve maximum life- and healthspan benefits and that sufficiently high levels are not achieved by the identified FGF21 inducers. More in-depth studies of the effects of FGF21 and its inducers on longevity and healthspan are warranted.
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ABSTRACT: Calorie lowering slows the aging process and extends life span in diverse species by so far unknown mechanisms. The inverse linear relationship between calorie intake and life span suggests that regulators of energy metabolism are of importance in aging. The present study shows that lifelong caloric restriction in mice induces a metabolic adaptation with reduced lipogenesis and enhanced lipolysis and ketogenesis. This process, that is, the reprogramming of hepatic fat metabolism, is associated with a marked rise of fibroblastic growth factor 21 as a putative starvation master regulator. Due to the life span-extending properties of fibroblastic growth factor 21, the rise in fibroblastic growth factor 21 might contribute to the markedly better health status found in mice upon lifelong caloric restriction feeding. In addition, adropin, known as a peptide that controls lipid homeostasis, is significantly upregulated, underlining the diminution of lipogenesis that was further substantiated by decreased expression of liver-X-receptor α and its target genes sterol regulatory element-binding protein-1c, fatty acid synthase, and member 1 of human transporter subfamily ABCA upon lifelong caloric restriction feeding.The Journals of Gerontology Series A Biological Sciences and Medical Sciences 10/2013; 69(8). DOI:10.1093/gerona/glt160 · 5.42 Impact Factor
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ABSTRACT: Third World quasi-vegan cultures have been characterized by low risks for "Western" cancers, autoimmune disorders, obesity, and diabetes. The relatively low essential amino acid contents of many vegan diets may play a role in this regard. It is proposed that such diets modestly activate the kinase GCN2 - a physiological detector of essential amino acid paucity - within the liver, resulting in up-regulated production of fibroblast growth factor 21 (FGF21). FGF21, by opposing the stimulatory effect of growth hormone on hepatic IGF-I production, may be responsible for the down-regulation of plasma IGF-I observed in vegans consuming diets of modest protein content. Decreased IGF-I bioactivity throughout life can be expected to have a favorable impact on cancer risk, as observed in rodents that are calorie restricted or genetically defective in IGF-I activity. Increased FGF21 in vegans might also contribute to their characteristic leanness and low LDL cholesterol by promoting hepatic lipid oxidation while inhibiting lipogenesis. Direct trophic effects of FGF21 on pancreatic beta-cells may help to explain the low risk for diabetes observed in vegans, and the utility of vegan diets in diabetes management. And up-regulation of GCN2 in immune cells, by boosting T regulatory activity, might play some role in the reduced risk for autoimmunity reported in some quasi-vegan cultures. The fact that bone density tends to be no greater in vegans than omnivores, despite consumption of a more "alkaline" diet, might be partially attributable to the fact that FGF21 opposes osteoblastogenesis and decreases IGF-I. If these speculations have merit, it should be possible to demonstrate that adoption of a vegan diet of modest protein content increases plasma FGF21 levels.Medical Hypotheses 06/2014; 83(3). DOI:10.1016/j.mehy.2014.06.014 · 1.07 Impact Factor
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ABSTRACT: Since the initial observation that a calorie-restricted (CR) diet can extend rodent lifespan, many genetic and pharmaceutical interventions that also extend lifespan in mammals have been discovered. The mechanism by which CR and these other interventions extend lifespan is the subject of significant debate and research. One proposed mechanism is that CR promotes longevity by increasing insulin sensitivity, but recent findings that dissociate longevity and insulin sensitivity cast doubt on this hypothesis. These findings can be reconciled if longevity is promoted not via increased insulin sensitivity, but instead via decreased PI3K/Akt/mTOR pathway signaling. This review presents a unifying hypothesis that explains the lifespan-extending effects of a variety of genetic mutations and pharmaceutical interventions and points towards new molecular pathways which may also be leveraged to promote healthy aging.SpringerPlus 12/2014; 3(1):735. DOI:10.1186/2193-1801-3-735
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