Brain ‘switch’ tells body to burn fat after eating

CT and PET imaging has helped Monash University researchers find a mechanism in the brain that coordinates feeding with energy expenditure – a discovery that could lead to novel targets for the treatment of obesity.

Dr Garron Dodd and Professor Tony Tiganis

Prof Tony Tiganis and Dr Garron Dodd from the Monash Biomedicine Discovery Institute’s Metabolic Disease and Obesity Program showed in mice models that feeding controls the conversion of white fat, which stores energy, into beige fat, which expends it. Fat in the human body is stored in specialised cells called adipocytes, some of which can change from white to beige states and back again, a process referred to as ‘browning'.

Their study, published in Cell Metabolism, showed that after a meal the brain responds to circulating insulin, which is increased after a rise in blood glucose. The brain then sends signals to promote the browning of fat to expend energy. By contrast, after a fast, the brain instructs these browned adipocytes to once more convert into white adipocytes, storing energy. These processes help prevent both excess weight gain and excess weight loss in response to feeding and fasting, meaning body weight remains relatively stable over time.

The Monash Biomedical Imaging preclinical team performed the PET and CT imaging using the Inveon PET-SPECT-CT and provided imaging data analysis for the study.

For the PET imaging, the MBI preclinical team injected mice with a radioactive glucose tracer and imaged the distribution of glucose throughout the body.

CT imaging located individual fat pads and then determined the amount of glucose tracer that had been taken up within each specific fat pad.

The PET and CT imaging results clearly demonstrated that mice can activate standard white fat cells to become brown fat cells that take up and utilise more glucose from the blood post-feeding to help control blood glucose levels and use excess energy.

Read more about this study on the Monash Biomedicine Discovery Institute website news page.

PET imaging demonstrates how feeding changed white fat into brown fat in mice.
PET imaging demonstrates how feeding changed white fat into brown fat in mice. The arrows point to the inguinal fat pads on either side of the mice in the fed and fasted groups. Glucose uptake is shown in the heat map with yellow indicating high uptake. The large glucose rich structure in the lower abdominal cavity is the bladder.