(18-05-08) New Anti-Obesity Drugs Could Stunt Kids' Brains

The potential problems of a once-promising class of weight-loss drugs just keep growing.
In a study published today in Neuron, Massachusetts Institute of Technology researchers found that a cannabinoid receptor antagonist -- in layman's terms, a munchies-blocker -- stunted the brains of juvenile mice.
Their findings raise the troubling possibility that such drugs could have similar effects on human children.
"We used animal models, but there's a good parallel to human physiology," said study co-author Cheng-Hang Liu.
Several new anti-obesity treatments, including Merck's taranabant and rimonabant -- sold in Europe as Acomplia by Sanofi-Aventis but as-yet-unapproved in the United States -- promise to reduce appetite by blocking the brain's cannabinoid receptors. Those are the receptors activated by marijuana, resulting in appetite surges.
But while the drugs do reduce dietary cravings, they may have disturbing side effects that are only now becoming apparent.
Other researchers have found that cannabinoid receptor blockers interfere with neural connectivity in rat brains -- a phenomenon that in humans is associated with depression. The Food and Drug Administration has refused to approve Acomplia because it appears to cause anxiety, depression and suicidal thoughts.
To study the drugs' neurological effects, Liu's team used a common model for testing brain adaptiveness: mice with one eye covered. Such mice usually experience a rewiring of the visual cortex, with the brain disconnecting from the unused eye while strengthening connections to the other. But that's not what happened in Liu's mice.
"The drug partially blocked this type of plasticity," he said.
This is especially troubling because the mice were young. "The juvenile stage of mice is parallel to what we know as the infant stage in humans, when the brain is plastic and prone to modification," said Liu.
Beyond interfering with neurological development during the critical stage of infancy, could cannabinoid receptor blockers also keep adult brains from developing?
Liu said he hadn't yet tested adult mice, much less adult humans, but warned that physiological pathways targeted by drugs like rimonabant and taranabant are important for keeping bodies and brains at equilibrium.
"You can envision a situation where the adult brain is more fragile under the influence of this drug," he said.
Cannabinoid Receptor Blockade Reveals Parallel Plasticity Mechanisms in Different Layers of Mouse Visual Cortex [Neuron}

By Brandon Keim May 07, 2008 | PMCategories: Brain, Medicine & Medical Procedures

Source: Wired Science

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