Breakdown product boosts brain energy
Alcohol may give heavy drinkers more than just a buzz. It can also fuel their brains, a new study suggests.
Long-term booze use boosts brain levels of acetate, an energy-rich by-product of alcohol metabolism, researchers report online March 8 in the Journal of Clinical Investigation. In the study, people who downed at least eight drinks per week also sucked more energy from acetate than their light-drinking counterparts.
The extra energy may give heavy drinkers more incentive to imbibe, says study coauthor Graeme Mason of Yale University. And the caloric perk might help explain why alcohol withdrawal is so hard.
“I think it's a very good hypothesis,” says biochemical geneticist Ting-Kai Li of Duke University. Scientists had suspected that heavy drinkers absorb and burn more acetate, but, he adds, “Graeme Mason showed that this is actually happening.”
Acetate is best known as a chemical in vinegar. But when people drink a glass of wine or drain a can of beer, their liver breaks down the alcohol and pumps out acetate as leftovers. The bloodstream then delivers acetate throughout the body, including to the brain.
Human brains typically run on sugar. But with enough acetate in the blood, Mason thought, brains might crank up their ability to burn it too. To find out if his suspicion was correct, Mason and his colleagues peered into the brains of seven heavy drinkers and seven light drinkers, who quaffed fewer than two drinks per week.
The team injected sober volunteers with a form of acetate that was tagged with a traceable atom. Then the volunteers lay on their backs for two hours in a magnetic resonance imaging, or MRI, machine while Mason’s group tracked the tagged acetate.
The scientists shot brief bursts of radio waves into the participants’ brains that delivered tiny bits of energy to the tagged atoms and jostled out a return signal. The return signal varied slightly in frequency if the brain had burned acetate, so Mason’s team could measure not only how much acetate was there but also how much fuel the participants were using.
Heavy drinkers transported more acetate to their brains and burned the chemical about twice as fast as light drinkers, Mason’s group found. Like a car that can switch to ethanol when it runs out of gasoline, heavy drinkers’ brains could tap energy from an alternate fuel source.
When Mason first saw the results, he says, “I jumped out of my chair and threw my fist in the air.” He had suspected that people with high blood acetate levels would be better at wringing energy from the chemical, but he says, “the effect was way bigger than I thought.”
For many years, scientists thought that the brain could use only sugar as a source of energy, says Nora Volkow, director of the National Institute on Drug Abuse in Bethesda, Md. But that’s changing, she says: Mason and colleagues’ study contributes to the shifting view of the brain because “they showed a huge effect.”
Next, Mason wants to figure out whether taking acetate would ease alcohol addicts’ withdrawal symptoms. But he cautions, “I don’t want people to start chugging vinegar.” Because the liver is very good at turning alcohol into acetate, he says, people would have to ingest quarts of vinegar to get as much acetate as they do from drinking alcohol.