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      Autophagy-mediated longevity is modulated by lipoprotein biogenesis

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          ABSTRACT

          Autophagy-dependent longevity models in C. elegans display altered lipid storage profiles, but the contribution of lipid distribution to life-span extension is not fully understood. Here we report that lipoprotein production, autophagy and lysosomal lipolysis are linked to modulate life span in a conserved fashion. We find that overexpression of the yolk lipoprotein VIT/vitellogenin reduces the life span of long-lived animals by impairing the induction of autophagy-related and lysosomal genes necessary for longevity. Accordingly, reducing vitellogenesis increases life span via induction of autophagy and lysosomal lipolysis. Life-span extension due to reduced vitellogenesis or enhanced lysosomal lipolysis requires nuclear hormone receptors (NHRs) NHR-49 and NHR-80, highlighting novel roles for these NHRs in lysosomal lipid signaling. In dietary-restricted worms and mice, expression of VIT and hepatic APOB (apolipoprotein B), respectively, are significantly reduced, suggesting a conserved longevity mechanism. Altogether, our study demonstrates that lipoprotein biogenesis is an important mechanism that modulates aging by impairing autophagy and lysosomal lipolysis.

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          Most cited references51

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          Stochastic and genetic factors influence tissue-specific decline in ageing C. elegans.

          The nematode Caenorhabditis elegans is an important model for studying the genetics of ageing, with over 50 life-extension mutations known so far. However, little is known about the pathobiology of ageing in this species, limiting attempts to connect genotype with senescent phenotype. Using ultrastructural analysis and visualization of specific cell types with green fluorescent protein, we examined cell integrity in different tissues as the animal ages. We report remarkable preservation of the nervous system, even in advanced old age, in contrast to a gradual, progressive deterioration of muscle, resembling human sarcopenia. The age-1(hx546) mutation, which extends lifespan by 60-100%, delayed some, but not all, cellular biomarkers of ageing. Strikingly, we found strong evidence that stochastic as well as genetic factors are significant in C. elegans ageing, with extensive variability both among same-age animals and between cells of the same type within individuals.
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            Regulation of the Caenorhabditis elegans longevity protein DAF-16 by insulin/IGF-1 and germline signaling.

            The lifespan of Caenorhabditis elegans is regulated by the insulin/insulin-like growth factor (IGF)-1 receptor homolog DAF-2, which signals through a conserved phosphatidylinositol 3-kinase (PI 3-kinase)/Akt pathway. Mutants in this pathway remain youthful and active much longer than normal animals and can live more than twice as long. This lifespan extension requires DAF-16, a forkhead/winged-helix transcription factor. DAF-16 is thought to be the main target of the DAF-2 pathway. Insulin/IGF-1 signaling is thought to lead to phosphorylation of DAF-16 by AKT activity, which in turn shortens lifespan. Here, we show that the DAF-2 pathway prevents DAF-16 accumulation in nuclei. Disrupting Akt-consensus phosphorylation sites in DAF-16 causes nuclear accumulation in wild-type animals, but, surprisingly, has little effect on lifespan. Thus the DAF-2 pathway must have additional outputs. Lifespan in C. elegans can be extended by perturbing sensory neurons or germ cells. In both cases, lifespan extension requires DAF-16. We find that both sensory neurons and germline activity regulate DAF-16 accumulation in nuclei, but the nuclear localization patterns are different. Together these findings reveal unexpected complexity in the DAF-16-dependent pathways that regulate aging.
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              RNAi-mediated gene silencing in non-human primates.

              The opportunity to harness the RNA interference (RNAi) pathway to silence disease-causing genes holds great promise for the development of therapeutics directed against targets that are otherwise not addressable with current medicines. Although there are numerous examples of in vivo silencing of target genes after local delivery of small interfering RNAs (siRNAs), there remain only a few reports of RNAi-mediated silencing in response to systemic delivery of siRNA, and there are no reports of systemic efficacy in non-rodent species. Here we show that siRNAs, when delivered systemically in a liposomal formulation, can silence the disease target apolipoprotein B (ApoB) in non-human primates. APOB-specific siRNAs were encapsulated in stable nucleic acid lipid particles (SNALP) and administered by intravenous injection to cynomolgus monkeys at doses of 1 or 2.5 mg kg(-1). A single siRNA injection resulted in dose-dependent silencing of APOB messenger RNA expression in the liver 48 h after administration, with maximal silencing of >90%. This silencing effect occurred as a result of APOB mRNA cleavage at precisely the site predicted for the RNAi mechanism. Significant reductions in ApoB protein, serum cholesterol and low-density lipoprotein levels were observed as early as 24 h after treatment and lasted for 11 days at the highest siRNA dose, thus demonstrating an immediate, potent and lasting biological effect of siRNA treatment. Our findings show clinically relevant RNAi-mediated gene silencing in non-human primates, supporting RNAi therapeutics as a potential new class of drugs.
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                Author and article information

                Journal
                Autophagy
                Autophagy
                KAUP
                Autophagy
                Taylor & Francis
                1554-8627
                1554-8635
                February 2016
                15 December 2015
                15 December 2015
                : 12
                : 2
                : 261-272
                Affiliations
                [a ]Department of Molecular Biology, Cell Biology and Biochemistry, Brown University , Providence, RI, USA
                [b ]The Howard Hughes Medical Institute, The Glenn Center for Aging Research, The Salk Institute for Biological Studies , La Jolla, CA, USA
                [c ]The Howard Hughes Medical Institute, Molecular and Cell Biology Department, Li Ka Shing Center, University of California Berkeley , Berkeley, CA, USA
                [d ]Del E. Webb Neuroscience, Aging and Stem Cell Research Center, Program of Development and Aging, Sanford-Burnham Medical Research Institute , La Jolla, CA, USA
                Author notes
                CONTACT Louis R. Lapierre louis_lapierre@ 123456brown.edu

                Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/kaup. #Contributed equally

                Supplemental data for this article can be accessed on the publisher's website.

                Article
                1127464
                10.1080/15548627.2015.1127464
                4836030
                26671266
                0bd79808-750e-46a8-9b33-4b2385b64a8e
                © 2016 The Author(s). Published with license by Taylor & Francis Group, LLC

                This is an Open Access article distributed under the terms of the Creative Commons Attribution-Non-Commercial License ( http://creativecommons.org/licenses/by-nc/3.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. The moral rights of the named author(s) have been asserted.

                History
                : 6 January 2015
                : 16 November 2015
                : 25 November 2015
                Page count
                Figures: 4, Tables: 0, References: 77, Pages: 12
                Categories
                Basic Brief Report

                Molecular biology
                apolipoprotein b,autophagy,c. elegans,fat storage,intestine,life span,lipid metabolism,lipoprotein,tor,vitellogenin

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