Researchers Explore Linkage Between Leptin and Obesity

Adults who possess a very rare genetic mutation that prevents their bodies from producing leptin may shed new light on the linkage between leptin and obesity, according to researchers at the University of California at Los Angeles.

After being injected with leptin, these adults had a dramatic loss of weight, suggesting once again that leptin may have a role in treating obesity.

Leptin is manufactured in fat cells and signals fullness, controls the appetite and tells the brain to stop eating. The release of leptin is triggered by puberty and regulates sexual development. Also, it helps the immune system fight off disease.

Three cousins from Turkey, all with the leptin genetic mutation, were brought to UCLA for treatment with leptin. The cousins ranged in age from late 20s to 40 and one was still prepubescent. All of the cousins were severely obese.

"We hypothesized that leptin deficiency may lead to obesity and, in some cases, delay sexual and psychological maturity," said Dr. Julio Licinio, professor of medicine and lead researcher. "Although this is a small study, it produced striking results."

Ten months after the start of the study, the three cousins had lost half of their body weight -- more than 150 pounds each. The leptin therapy also resulted in physiological and personality changes in the three cousins.

The prepubescent cousin began experiencing physiological changes linked with adolescence and rapidly reached sexual maturity. All three cousins experienced neurological growth, according to the study that will presented at the annual meeting of the Society for Neuroscience.

"At the end of the study, we measured the subjects' brains with MRI and discovered that the organs had expanded a small but significant amount," said Licinio. "While the relevance of this outcome is currently unclear, it poses the first known instance of brain growth in adults."

The dispositions of the cousins also changed. Within two weeks of treatment, they became more assertive and independent.

"The subjects' personality changes suggest that there is a relationship between fat and how we feel," said Licinio. "We plan to explore leptin's link to mood disorders in the future."

Researchers previously thought leptin might be good for weight control but found that obese people produced too much of the hormone and their bodies stopped responding to its appetite control signals.

However, in rare instances like the cousins in Licino's study, people become obese because they manufacture too little of the hormone.

Other sources: UCLA