Hepatic mTORC2 compensates for loss of adipose mTORC2 in mediating energy storage and glucose homeostasis. 2023

Irina C Frei, and Diana Weissenberger, and Christoph Müller, and Michael N Hall, and Mitsugu Shimobayashi
Biozentrum, University of Basel, Basel, Switzerland.

Mammalian target of rapamycin complex 2 (mTORC2) is a protein kinase complex that plays an important role in energy homeostasis. Loss of adipose mTORC2 reduces lipogenic enzyme expression and de novo lipogenesis in adipose tissue. Adipose-specific mTORC2 knockout mice also display triglyceride accumulation in the liver. However, the mechanism and physiological role of hepatic triglyceride accumulation upon loss of adipose mTORC2 are unknown. Here, we show that loss of adipose mTORC2 increases the expression of de novo lipogenic enzymes in the liver, thereby causing accumulation of hepatic triglyceride and hypertriglyceridemia. Simultaneous inhibition of lipogenic enzymes in adipose tissue and liver by ablating mTORC2 in both tissues prevented accumulation of hepatic triglycerides and hypertriglyceridemia. However, loss of adipose and hepatic mTORC2 caused severe insulin resistance and glucose intolerance. Thus our findings suggest that increased hepatic lipogenesis is a compensatory mechanism to cope with loss of lipogenesis in adipose tissue, and further suggest that mTORC2 in adipose tissue and liver plays a crucial role in maintaining whole body energy homeostasis.NEW & NOTEWORTHY Loss of adipose and hepatic mTORC2 causes diabetes.

UI MeSH Term Description Entries
D008099 Liver A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances. Livers
D008322 Mammals Warm-blooded vertebrate animals belonging to the class Mammalia, including all that possess hair and suckle their young. Mammalia,Mammal
D009765 Obesity A status with BODY WEIGHT that is grossly above the recommended standards, usually due to accumulation of excess FATS in the body. The standards may vary with age, sex, genetic or cultural background. In the BODY MASS INDEX, a BMI greater than 30.0 kg/m2 is considered obese, and a BMI greater than 40.0 kg/m2 is considered morbidly obese (MORBID OBESITY).
D005947 Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Dextrose,Anhydrous Dextrose,D-Glucose,Glucose Monohydrate,Glucose, (DL)-Isomer,Glucose, (alpha-D)-Isomer,Glucose, (beta-D)-Isomer,D Glucose,Dextrose, Anhydrous,Monohydrate, Glucose
D006706 Homeostasis The processes whereby the internal environment of an organism tends to remain balanced and stable. Autoregulation
D000076225 Mechanistic Target of Rapamycin Complex 2 A multiprotein complex consisting of mTOR KINASE; MLST8 PROTEIN; rapamycin-insensitive companion of mTOR protein (RICTOR PROTEIN); and PRR5 (proline-rich protein 5). Like mTORC1, it also regulates cell growth and proliferation in response to growth factors but may not be as sensitive to nutrient availability and is insensitive to SIROLIMUS. In contrast to mTORC1, it can regulate the ACTIN CYTOSKELETON through RHO GTPASES to promote the formation of STRESS FIBERS. The mTORC2 complex also plays a critical role in AKT1 PROTEIN KINASE phosphorylation and activation. MTORC-2,TOR Complex 2,TORC2,Target of Rapamycin Complex 2,mTORC2,Complex 2, TOR
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D014280 Triglycerides An ester formed from GLYCEROL and three fatty acid groups. Triacylglycerol,Triacylglycerols,Triglyceride
D015228 Hypertriglyceridemia A condition of elevated levels of TRIGLYCERIDES in the blood. Hypertriglyceridemias
D050155 Lipogenesis De novo fat synthesis in the body. This includes the synthetic processes of FATTY ACIDS and subsequent TRIGLYCERIDES in the LIVER and the ADIPOSE TISSUE. Lipogenesis is regulated by numerous factors, including nutritional, hormonal, and genetic elements. Lipogeneses

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