In addition to white adipose tissue, or fat, which stores energy, the human body also contains a second type of fat: brown adipose tissue. This discovery by Prof. Wouter van Marken Lichtenbelt, professor of Human Biology at Maastricht, made global headlines a few years ago. Brown adipose tissue's primary function is to produce heat by burning fatty acids and glucose. It is known to be activated by exposure to cold (see the PET scans showing a subject before and after exposure to cold). By producing heat, the adipose tissue ensures the body maintains a stable temperature. This process requires energy, which is why brown adipose tissue could play a role in combating overweight and obesity.

In the cold
However, besides exposure to cold there are other ways of activating brown adipose tissue. In her research, Broeders shows that brown adipose tissue can also be activated by administering substances naturally found in the body, such as thyroid hormone and/or bile acids. Her research focused on patients with thyroid cancer. After their thyroid has been surgically removed, these patients have hardly any thyroid hormone in their blood. They are administered thyroid hormone in tablets, causing the hormone level to rise over the course of a number of months. This made it possible to analyse the effect of thyroid hormone on brown adipose tissue. As it turned out, thyroid hormone boosts the activity of brown adipose tissue. A second study focused on the effects of bile acids, which are known to stimulate brown adipose tissue in animals. Broeders and her colleagues now studied this effect in human subjects, and revealed that administering bile acid tablets causes a rise in both energy consumption and brown adipose tissue activity.

Further research needed
Future research will have to show whether it is indeed possible for overweight and obese people to lose weight by taking substances normally found in the body, such as thyroid hormone and bile acids. Broeders explained, ‘We still have a long way to go, but this approach offers prospects. Administering combination drugs may be one way to go.’ Bile acid tablets, a well-known medication used to treat cholesterol gallstones, are already available. Broeders recently defended her PhD thesis, entitled Pathways for brown adipose tissue activation in humans, at Maastricht University.