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mTOR Signaling in X/A‐Like Cells Contributes to Lipid Homeostasis in Mice
Author(s) -
Li Ziru,
Yu Ruili,
Yin Wenzhen,
Qin Yan,
Ma Liangxiao,
Mulholland Michael,
Zhang Weizhen
Publication year - 2019
Publication title -
hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.488
H-Index - 361
eISSN - 1527-3350
pISSN - 0270-9139
DOI - 10.1002/hep.30229
Subject(s) - ghrelin , pi3k/akt/mtor pathway , lipid metabolism , endocrinology , medicine , adipose tissue , biology , protein kinase b , lipogenesis , steatosis , signal transduction , chemistry , microbiology and biotechnology , hormone
Gastric mechanistic target of rapamycin (mTOR) signaling is inversely associated with the expression and secretion of ghrelin, a 28‐aa peptide hormone produced by gastric X/A‐like cells. Ghrelin contributes to obesity and hepatic steatosis. We sought to control global lipid metabolism via the manipulation of gastric mTOR signaling in X/A‐like cells. We established a ghrl‐cre transgene in which the Cre enzyme is expressed in X/A‐like cells under the control of the ghrelin‐promoter. mTOR flox/flox and tuberous sclerosis 1 ( TSC1) flox/flox mice were separately bred with ghrl‐cre mice to generate mTOR‐ghrl‐cre or TSC1‐ghrl‐cre mice, within which mTOR signaling was suppressed or activated, respectively. Lipid metabolism in liver and adipose depots was analyzed. Under the control of the ghrelin‐promoter, the Cre enzyme was exclusively expressed in stomach X/A‐like cells in adult animals. Knockout of mTOR in X/A‐like cells increased circulating acyl‐ghrelin and promoted hepatic lipogenesis with effects on adipose depots. Activation of mTOR signaling by deletion of its upstream inhibitor, TSC1, decreased ghrelin expression and secretion, altering lipid metabolism as evidenced by resistance to high‐fat diet–induced obesity and hepatic steatosis. Both ghrelin administration and injection of rapamycin, an inhibitor of mTOR, altered the phenotypes of TSC1‐ghrl‐cre mice. Conclusion: Gastric mTOR signaling in X/A‐like cells contributes to organism lipid homeostasis by regulating hepatic and adipose lipid metabolism. Gastric mTOR signaling may provide an alternative strategy for intervention in lipid disorders.