Grant: Project Grant

Brown fat is the only organ able to burn energy to directly produce heat. This tissue allows small animals to live in cold environments without having to rely on muscle shivering. Brown fat is present in adults and can be seen using 'positron emission tomography' imaging (or 'PET imaging') with injection of a radioactive sugar label (or 'sugar tracer') that is taken up by brown fat when it is activated upon cold exposure. PET imaging with a sugar tracer is currently the standard method to measure brown fat. We have found that brown fat in adults burns energy mostly by utilizing its own fat content. We have demonstrated that PET imaging with a sugar tracer underestimates the total contribution of brown fat to energy expenditure, especially in people with type 2 diabetes. The contribution of brown fat to energy balance cannot be precisely determined using the current methods we have. As brown fat is currently viewed as a promising target for the treatment of obesity and type 2 diabetes, it is essential to quantify its role in energy expenditure in people without and with obesity and/or type 2 diabetes. We propose here to develop and validate new methods to quantify brown fat energy expenditure by measuring its own fat utilization with a combination of PET imaging with a novel fat tracer and magnetic resonance imaging techniques. We will apply these novel techniques during cold exposure and stimulation with a drug known to activate brown fat in people. Our laboratory has made outstanding contributions to the field of brown fat research through the imaging innovations we made and our integrated approach to the study of energy metabolism directly in people. This project will lead to new standard methods to measure brown fat energy expenditure and will provide essential knowledge on brown fat as a target to prevent and treat obesity and type 2 diabetes.