Publication Date:
2010-12-24
Description:
The multi-component mechanistic target of rapamycin complex 1 (mTORC1) kinase is the central node of a mammalian pathway that coordinates cell growth with the availability of nutrients, energy and growth factors. Progress has been made in the identification of mTORC1 pathway components and in understanding their functions in cells, but there is relatively little known about the role of the pathway in vivo. Specifically, we have little knowledge regarding the role mTOCR1 has in liver physiology. In fasted animals, the liver performs numerous functions that maintain whole-body homeostasis, including the production of ketone bodies for peripheral tissues to use as energy sources. Here we show that mTORC1 controls ketogenesis in mice in response to fasting. We find that liver-specific loss of TSC1 (tuberous sclerosis 1), an mTORC1 inhibitor, leads to a fasting-resistant increase in liver size, and to a pronounced defect in ketone body production and ketogenic gene expression on fasting. The loss of raptor (regulatory associated protein of mTOR, complex 1) an essential mTORC1 component, has the opposite effects. In addition, we find that the inhibition of mTORC1 is required for the fasting-induced activation of PPARalpha (peroxisome proliferator activated receptor alpha), the master transcriptional activator of ketogenic genes, and that suppression of NCoR1 (nuclear receptor co-repressor 1), a co-repressor of PPARalpha, reactivates ketogenesis in cells and livers with hyperactive mTORC1 signalling. Like livers with activated mTORC1, livers from aged mice have a defect in ketogenesis, which correlates with an increase in mTORC1 signalling. Moreover, we show that the suppressive effects of mTORC1 activation and ageing on PPARalpha activity and ketone production are not additive, and that mTORC1 inhibition is sufficient to prevent the ageing-induced defect in ketogenesis. Thus, our findings reveal that mTORC1 is a key regulator of PPARalpha function and hepatic ketogenesis and suggest a role for mTORC1 activity in promoting the ageing of the liver.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sengupta, Shomit -- Peterson, Timothy R -- Laplante, Mathieu -- Oh, Stephanie -- Sabatini, David M -- CA103866/CA/NCI NIH HHS/ -- CA129105/CA/NCI NIH HHS/ -- R01 CA129105/CA/NCI NIH HHS/ -- R01 CA129105-04/CA/NCI NIH HHS/ -- Canadian Institutes of Health Research/Canada -- Howard Hughes Medical Institute/ -- England -- Nature. 2010 Dec 23;468(7327):1100-4. doi: 10.1038/nature09584.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, Massachusetts 02142, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21179166" target="_blank"〉PubMed〈/a〉
Keywords:
*Aging
;
Animals
;
Cell Line
;
Fasting/*metabolism
;
*Gene Expression Regulation
;
Humans
;
Ketone Bodies/*biosynthesis/metabolism
;
Liver/metabolism
;
Mice
;
Mice, Inbred C57BL
;
Mice, Knockout
;
Multiprotein Complexes
;
Nuclear Receptor Co-Repressor 1/metabolism
;
PPAR alpha/antagonists & inhibitors/metabolism
;
Proteins/genetics/*metabolism
;
TOR Serine-Threonine Kinases
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
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