Via EurekAlert!: researchers have "explained how rapamycin, a drug that extends mouse lifespan, also causes insulin resistance. The researchers showed in an animal model that they could, in principle, separate the effects, which depend on inhibiting two protein complexes, mTORC1 and mTORC2, respectively. The study suggests that molecules that specifically inhibit mTORC1 may combat age-related diseases without the insulin-resistance side effect. ... The mTOR complexes, for mammalian (or mechanistic) target of rapamycin, are proteins that regulate cell growth, movement, and survival, as well as protein synthesis and transcription. Specifically, there are two mTOR complexes and one mTOR protein. The mTOR protein is the core of both complexes (mTORC1 and mTORC2), which behave differently based on their associated proteins. One or both of the mTOR complexes can be inappropriately activated in certain cancers, and dual-specific inhibitors are being developed as chemotherapeutic agents. Several theories have been put forward by researchers to explain the observations that patients receiving rapamycin are more prone to developing glucose intolerance, which can lead to diabetes. Chronic treatment with rapamycin impairs glucose metabolism and the correct functioning of insulin in mice, despite extending lifespan. The research team demonstrated that rapamycin disrupts mTORC2 in the mice, and that mTORC2 is required for the insulin-mediated suppression of glucose metabolism in the liver. On the other hand, they also demonstrated that decreasing mTORC1 signaling was sufficient to extend lifespan independently from changes in glucose metabolism. They used a mouse strain in which mTORC1 activity was decreased and saw that lifespan was extended by 14 percent, yet the animals had normal glucose metabolism and insulin sensitivity."