Last call! Hormone treatment reduces alcohol consumption in drunken monkeys

Excessive alcohol consumption is a major public health issue which spans demographics and locations. It turns out, it also crosses into other species, with at least some non-human animals intentionally consuming and sometimes overconsuming fermented fruit as a way to catch a buzz.

Recent research has found a link between the production of a hormone called fibroblast growth factor 21 — FGF21 — and the likelihood of a person or animal to overindulge in alcohol consumption.

Kyle Flippo is a scientist at the Department of Neuroscience and Pharmacology at the University of Iowa’s Carver College of Medicine who, along with colleagues, set out to test the impact of FGF21 on alcohol consumption in vervet monkeys. Their findings were published in the journal Cell Metabolism.

“What led us to this question is there are mutations in the receptor that FGF21 signals through, which are associated with increased alcohol consumption in humans,” Flippo told SYFY WIRE. “Our bodies have ways to regulate these processes and genetic contributions can play a large part in how these diseases develop.”

While the exact same physiological processes are not necessarily present in vervet monkeys or in mice, both of which were used as model organisms in the team’s study, they do appear to be impacted by the levels of FGF21 in the body, and those levels appear to have a relationship with how much booze an individual consumes.

According to Flippo, monkeys drink — or eat, as the case may be — alcohol at about the same levels as humans do.

“Ten to fifteen percent of monkeys in this particular species engage in heavy drinking behavior. The monkeys we used in this study were ones who were selected based on that,” Flippo said.

Under ordinary circumstances, when a person or animal consumes alcohol, the liver secretes FGF21 as a way of protecting itself from damage. Once in the bloodstream, FGF21 makes its way to the brain where it activates neurons which suppress alcohol consumption. The team suspected that introducing higher levels of FGF21 might reduce overall consumption of alcohol in animals which regularly overconsume.

To test that idea, the team used an FGF21 analogue which could be administered either through injections or intravenously and waited to see what might happen. Changes in consumption behavior happened pretty quickly and were substantial.

“It took a couple of days before alcohol consumption comes down. That suggests there’s some sort of learning component to it. It’s not like after a single injection that they start drinking less, but after two or three days they do,” Flippo said.

On average, individuals who were treated with the hormone analogue consumed roughly half as much alcohol as they did before. Importantly, it did not change the patterns of their consumption. Vervet monkeys who were treated still drank as often as they usually would, but the amounts consumed declined.

It’s unclear what the user experience of FGF21 treatment is, or why precisely the monkeys reduced their alcohol consumption in the presence of higher hormone levels, but Flippo has some ideas.

“It’s tricky because we can’t really ask them what they’re feeling,” Flippo said. “We’re pretty sure it’s not aversive. It’s not making the animals ill or creating a negative association with alcohol. We think it’s lowering the threshold required to get the rewarding aspects.”

In essence, it appears that the introduction of additional FGF21 lowers tolerance and allows individuals to get what they’re seeking without needing to drink as much. This is supported by the fact that, once treatments were stopped, monkeys tended to return to their previous consumption levels over the course of about a week.

“That’s not necessarily a bad thing, because it means we’re not permanently altering the body physiology. The effects are not permanent, but I don’t know if we would want them to be,” Flippo said.

The question now is if these same treatments might be effective in human populations. At current, that’s unclear. The compound the team used was previously part of a human trial looking at its use as a diabetic therapy. FGF21 was effective in primate and mouse trials but was found to be ineffective in people, owing largely to differences in physiology.

The processes behind its anti-diabetic effect and the suppression of alcohol consumption are different, so those same challenges may not be present. Further studies and human trials are needed before we’ll know for sure. It could be that in the near future we’ll have an easy, safe, and effective way to reduce alcohol overconsumption, at least temporarily.

We’ll drink to that.