University of Pittsburgh scientists say they have zeroed in on two brain enzymes that help the fullness hormone leptin do its job in obese mice, a finding that could offer a fresh route to future weight-loss drugs. In rodent tests, compounds that restored leptin signaling led to big drops in fat while largely preserving muscle, according to the team led by Işın Çakır at Pitt’s School of Medicine. The researchers are quick to note that what works in mice often falls flat in people, so any human treatment is still a long way off.
In a paper published Feb. 5 in Nature Communications, the authors identify the focal adhesion kinases FAK and PYK2 as essential go-betweens for leptin receptor signaling in the hypothalamus. The study reports that these kinases phosphorylate STAT3 downstream of the leptin receptor, and that blocking or knocking them down blunts leptin’s appetite-suppressing effects and the weight loss produced by the HDAC6 inhibitor tubastatin A in diet-induced obese mice.
"Leptin resistance is a major barrier to treating obesity," senior author Işın Çakır said in a Pitt news release via UPMC. The team told local reporters that HDAC6-targeting compounds triggered dramatic fat loss in rodents while leaving most muscle mass intact, with WTAE reporting the group’s estimate of roughly a 50% drop in fat during treatment.
How it worked in mice
The researchers used transcriptomic and genetic tools to show that peripheral HDAC6 inhibition boosts hypothalamic expression of FAK and PYK2. Those kinases then phosphorylate STAT3 and switch on leptin’s anorectic program, the paper notes in Nature Communications. When the team infused a dual FAK/PYK2 inhibitor into the brain or used AAV-mediated knockdown in the mediobasal hypothalamus, tubastatin A stopped working as a slimming agent, and treated mice became resistant to the drug’s weight-reducing effect.
Where does this fit with current drugs
GLP-1 receptor agonists such as semaglutide and tirzepatide have already changed the landscape of obesity care, but they come with familiar gastrointestinal side effects listed right on their labels. The Drugs.com prescribing information for Wegovy lists nausea, vomiting, and diarrhea among the most frequent reactions, and Springer clinical analyses show that while most of the weight lost on GLP-1 drugs is fat, measurable reductions in lean mass have turned up in some studies.
Those safety and body-composition concerns are part of why the Pitt group is pushing for muscle-preserving strategies and for testing whether lower-dose combinations with other drugs could deliver benefit with fewer side effects. Çakır and collaborators stress that moving from mice to humans will require time and careful safety work, and that HDAC6 inhibitors, which were originally developed for oncology, may need significant fine-tuning to limit toxicity, according to the Pitt release.
