Researchers have identified a brain chemical that is involved in controlling appetite and obesity -- a finding that could lead to develop treatments to help people with obesity, according to Thursday`s New England Journal of Medicine.

Brain-derived neurotrophic factor (BDNF) was pointed to be important in energy homeostasis in animal, as it helps regulate appetite and weight, but little was known about its role in energy balance in humans.

Previous studies have found that heterozygous, variably sized, contiguous gene deletions cause the Wilms` tumor, aniridia, genitourinary anomalies, and mental retardation (WAGR) syndrome. Hyperphagia and obesity were observed in a subgroup of patients with the WAGR syndrome.

Researchers hypothesized that the subphenotype of obesity in the WAGR syndrome is attributable to deletions that induce haploinsufficiency of BDNF.

They studied the relationship between genotype and body-mass index (BMI) in 33 patients with the WAGR syndrome. Among them, BDNF haploinsufficiency was associated with lower levels of serum BDNF and with childhood-onset obesity.

Normally a person has two copies of the gene that controls BDNF. But the researchers found that most of the WAGR syndrome patients -- 19 of them -- were missing one copy of the gene, and thus had low blood levels of BDNF.

Every one of the 19 was obese by age 10 and had a strong tendency to overeat. The 14 other people who had two working copies of the gene were no more likely than the general population to be obese or overeat.

This strongly suggests BDNF is important for energy homeostasis in humans. Thus, BDNF was add to the understanding of factors underpinning obesity, they said.

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