Weight-loss drug that mimics the effect of exercise excites US researchers

Obese mice, taking an experimental drug, became endurance athletes, without the bother of exercising.

Obese mice, taking an experimental drug, became endurance athletes, without the bother of exercising. Photo: Getty

It’s a rare moment when you look at a laboratory mouse mid-experiment, and think: I’ll have what he’s having.

That’s what came to mind when reading about a new kind of drug, developed and tested by University of Florida researchers.

The drug causes “obese mice to lose weight by convincing the body’s muscles that they are exercising more than they really are, boosting the animals’ metabolism”.

In other words, it’s a radical weight-loss drug that works by mimicking exercise.

The compound also increases endurance, helping mice run nearly 50 per cent further than they could before.

“All without the mice lifting a paw,” chirps a statement from the researchers.

Kidding, right?

The drug – called SLU-PP-332, until something jazzier comes along – belongs to a class known as “exercise mimetics”.

These provide “some of the benefits of exercise without increasing physical activity”.

The real point of them is to help people who can’t exercise because of age and mobility issues.

SLU-PP-332 is in the early stages of development, but is intended to one day be tested on people with metabolic diseases.

So there tends to be an honourable motivation at the bottom of ‘exercise mimetic’ research.

But it’s a controversial area because some experimental drugs, intended to help the elderly, have been illegally hijacked by body builders and unscrupulous professional athletes.

The case of SARMs

In 2016, a class of drug called SARMs (selective androgen receptor modulators) were being tested in clinical trials “as a potential treatment to build strength in the elderly and people with wasting diseases”.

No SARM has been fully researched, or approved for human use. But they’re popular among the more reckless body builder set. This is because the drugs were designed to build muscle mass and bone density.

The new drug may prove to be an effective treatment for age-related muscle loss.

Meanwhile, a SARMs-like drug called Cardarine – also known as GW501516 – is an exercise mimetic “widely used by endurance athletes”.

It has been banned by the World Anti-Doping Agency.

So exercise mimetics is a conflicted area.

As a 2017 overview advises (a paper worth reading): “While physical exercise remains the best solution, the development of muscle-targeted ‘exercise mimetics’ may soon provide a pharmaceutical alternative to battle an increasingly sedentary lifestyle.

“At the same time, these advances are fuelling a raging debate on their escalating use as performance-enhancing drugs in high-profile competitions such as the Olympics.”

Read here for what the Australian regulator has to say about SARMs.

More about the new drug

The Florida researchers are hoping that one day their new drug, SLU-PP-332, will be tested in people to treat obesity, diabetes and age-related muscle loss.

They note that drugs like Ozempic – intended as a type 2 diabetes treatment, hijacked by TikTok as a weight-loss discovery – have “provided a breakthrough in reducing appetite, helping treat these metabolic diseases”.

But SLU-PP-332 doesn’t affect appetite or food intake. Nor does it cause mice to exercise more.

Instead, the drug “boosts a natural metabolic pathway that typically responds to exercise”.

In effect, SLU-PP-332 makes the body “act like it is training for a marathon, leading to increased energy expenditure and faster metabolism of fat in the body”.

Dr Thomas Burris, a professor of pharmacy at the University of Florida, who led the recent research, said: “This compound is basically telling skeletal muscle to make the same changes you see during endurance training.”

Burris said that when mice are treated with the drug, “you can see that their whole body metabolism turns to using fatty acids”.

This is very similar to what people use “when they are fasting or exercising”.

And then? “The animals start losing weight.”

Yet the mice kept eating the same amount of food and didn’t exercise any more than usual.

“They use more energy just living,” Burris said.

What’s next?

In other work, soon to be published, Burris and his lab have seen evidence that the compound “can also treat heart failure in mice by strengthening the heart muscle”.

So far, the drug hasn’t generated any severe side effects.

The next step is to refine the drug’s structure, ideally making it available as a pill instead of an injection.

Then the drug would be tested for side effects in more animal models before making the jump to human trials.

In the meantime, we needed to keep it far away from influencers and drug cheats.

The new paper can be found here.

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