The in vivo regulation of glucose homeostasis and lifespan by mTORC2
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7. Project Summary/Abstract The mammalian target of rapamycin (mTOR) signaling pathway is a highly conserved pathway that regulates growth and metabolism in response to the availability of nutrients. mTOR signaling is inhibited by rapamycin, an FDA-approved compound widely used during transplantation surgery as an immunosuppressant, as well as in clinical trials for the treatment of cancer. Treatment with rapamycin extends the lifespan of many model organisms, including mice, and is beneficial for the treatment of diseases of aging, including Alzheimer's disease, in mouse models. Treatment with rapamycin, and inhibition of mTOR complex 1 (mTORC1), is proposed to promote longevity by a mechanism similar to that of calorie restricted (CR) diet, in which caloric intake is reduced while maintaining adequate nutrition. However, we have found that rapamycin also inhibits mTOR complex 2 (mTORC2), disrupting glucose homeostasis and increasing hepatic insulin resistance. While studies in C. elegans have shown increased longevity when mTORC2 signaling is disrupted, the effect of disrupting mTORC2 in mammals is unknown. The work proposed herein will use a genetic approach to determine the effects of decreased mTORC2 signaling on lifespan, and furthermore will examine the contribution of mTORC2 signaling to the effects of a CR diet. Using mice engineered to overexpress Rictor, a key component of mTORC2, we will examine the ability of increased mTORC2 to promote longevity and increase resistance to the negative effects of a high-fat diet on glucose homeostasis. We will use a mass spectrometry based approach to understand the role played by mTORC2 in vivo, and identify pathways regulated by mTORC2 as well as characterize novel mTORC2 substrates. Finally, we will characterize mTORC2 signaling during normal aging. These aims will significantly increase our understanding of how the mTOR signaling pathway functions during pro-longevity interventions, and potentially increase our ability to treat diseases of aging without undesirable side effects. We will also determine if increased mTORC2 signaling can ameliorate the negative consequences of obesity on glucose homeostasis, determining if mTORC2 signaling might be of therapeutic use for the treatment of type 2 diabetes. Our mass spectrometry-based approach will help us to learn more about the in vivo consequences of modulating the mTORC2 pathway, and help us learn about how this pathway changes during the aging process.
