Researchers at McGill University have identified a molecular switch that activates an alternative heat-producing pathway in brown fat, a discovery that could lead to new treatments for bone diseases and metabolic disorders. The finding, published in a new study, reveals how a simple byproduct of fat breakdown can trigger a previously unknown energy-burning mechanism in the body.
Unlike white fat, which stores energy, brown fat burns calories to generate heat and help maintain body temperature in cold conditions. Scientists long believed this process relied on a single biological pathway. But the McGill team, led by Lawrence Kazak at the university’s Rosalind and Morris Goodman Cancer Institute, has now uncovered the trigger for a second mechanism known as the futile creatine cycle. When the body is exposed to cold, stored fat breaks down to produce heat and releases glycerol as a byproduct. The researchers discovered that glycerol binds to an enzyme called TNAP in a region they call the “glycerol pocket,” activating the alternative heat-producing pathway.
“This is the first time we’ve identified how an alternative heat-producing pathway is activated, independent of the classic system,” said Kazak, an associate professor in the Department of Biochemistry and Canada Research Chair in Adipocyte Biology. “That opens the door to understanding how multiple energy-burning systems work together to keep the body warm at the just-right temperature.”
Immediate Promise for Bone Disease Treatment
Although brown fat is often studied for its role in obesity and metabolism, the researchers say the most immediate applications of the discovery may relate to bone health. TNAP plays a vital role in building and maintaining strong bones by supporting calcification. Genetic mutations that affect the enzyme can cause hypophosphatasia, a rare disorder sometimes described as “soft bones” that leads to fractures, pain and skeletal deformities. By testing TNAP mutations in the lab, the team found that the same molecular switch involved in energy-burning cells also has a direct role in the mineralization process that hardens bone.
“This finding opens the door to a new kind of treatment, where increasing the activity of the TNAP enzyme through its glycerol pocket by natural or synthetic bioactive compounds could potentially boost the beneficial actions of the enzyme in patients, to help restore deficient bone mineralization to healthy levels,” said Marc McKee, a professor in the Faculty of Dental Medicine and Oral Health Sciences and Canada Research Chair in Biomineralization.
The researchers have already identified dozens of potential drug candidates for further investigation. While much of the work remains in early stages, the discovery offers a clear molecular target for developing therapies that could one day help patients with rare bone disorders regain healthier, stronger bones.