Brain gene is tied to obesity.

Researchers studying the DNA of people in Finland and Sweden have amassed evidence that a gene involved in brain chemistry influences whether a person is thin or fat.

Few specific genes have been convincingly linked to human obesity. A research team headed by Paivi Pajukanta of the University of California, Los Angeles now points the finger at one called solute carrier family 6 member 14 (SLC6A14).

The investigators originally studied obese and thin siblings within a group of Finnish families. They found evidence that a region on the X chromosome might account for some of the weight differences, within that region were several genes, including SLC6A14.

In the Dec. 1, 2003 Journal of Clinical Investigation, the researchers describe what they learned from a closer look at the gene in about 1,000 obese Finlanders and Swedes and a similar number of nonobese peers. The investigators identified a subtle mutation that creates a second version of the SLC6A14 gene and determined that the two variants weren't equally distributed between obese and nonobese people. One variant appeared significantly more often in obese people, suggesting that it predisposes them to gain weight or that the other variant somehow wards off obesity.

The gene produces a protein that probably regulates an important precursor to serotonin, a neurotransmitter implicated in the control of appetite and body weight, the researchers note.

In a commentary accompanying the new report, Hemant K. Tiwari and David B. Allison, both of University of Alabama at Birmingham, call the new results impressive but stress the need for follow-up studies to confirm SLC6A14's role in obesity.--J.T.