Chuck Bednar for redOrbit.com – Your Universe Online
A pair of naturally occurring hormones could be a secret weapon in the battle against obesity, according to research published last week in the peer-reviewed journal Cell.
The findings could provide new insight into the ways in which a person’s brain regulates body fat, and could result in the development of more effective ways to shed fat and prevent weight-gain by converting white fat to brown fat.
White fat, or white adipose tissue, serves as an energy store and a thermal insulator. Brown fat, or brown adipose tissue, is primarily used to generate body heat (especially in infants or animals during hibernation). It contains smaller fat droplets and requires more oxygen than white fat.
In their research, Tony Tiganis from the Monash University Department of Biochemistry and Molecular Biology and his colleagues discovered a molecular mechanism that relies upon the combined action of the hormones leptin and insulin to stimulate the fat-burning process.
Leptin is an appetite suppressant generated in fat cells, and insulin is produced in the pancreas in response to rising levels of glucose in the blood, the researchers explained. By working together, however, they can cause the brain to burn off fat instead of storing it. They do this by acting on a group of neurons in the brain that triggers body fat to be burned through the nervous system.
“These hormones give the brain a comprehensive picture of the fatness of the body,” Tiganis explained. “Because leptin is produced by fat cells, it measures the level of existing fat reserves – the more fat, the more leptin. Whereas insulin provides a measure of future fat reserves because glucose levels rise when we eat.”
He explains that fat in adult humans is typically stored in adipocytes, which are specialized cells made from white fat tissue. However, fat cells made from brown adipocytes can be found around a person’s neck and shoulders, and these cells can be induced to burn fat instead of storing it.
Tiganis and his fellow researchers found that leptin and insulin interact with neurons in the brain’s hypothalamus. The hormones can cause these proopiomelanocortin (POMC) neurons to send signals through the nervous system to convert white fat into brown fat, ultimately causing excess fat to be burned off.
In their laboratory work, the researchers were able to demonstrate that the process in regulated within these neurons by enzymes known as phosphatases. Phosphatases inhibit the actions of both leptin and insulin, they explained, and when these inhibitors were reduced, they found that the browning and burning of fat within the body increased.
Typically, this process is used to help a person maintain his or her body weight. However, Professor Tiganis explained that it goes awry in patients with diet-induced obesity, and he said that targeting these two enzymes could ultimately help people lose weight and shed unwanted fat.
“Turning white fat into brown fat is a very exciting new approach to developing weight loss agents. But it is not an easy task, and any potential therapy is a long way off,” he added.
In addition to Monash University, researchers from Harvard Medical School, the Indiana University School of Medicine, the Pennington Biomedical Research Center, the University of Pennsylvania, and the University of Toronto were also involved in the research.
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