It may be possible to turn back the clock on biological aging, a preliminary study published in Aging Cell has found. A three-drug cocktail – including: one growth hormone and two anti-diabetic drugs – shaved, on average, 2.5 years off nine patients during a year-long trial.
While we tend to define age as the number of years we have been alive – our "chronological age", so to speak – there is another definition, which relates to how fast our body is aging and when we can expect to see symptoms and disease associated with old age: it is our "biological age". Scientists can work out someone's biological age by measuring chemical changes to our DNA that occur with time. The result is that five 35-year-olds may share the same birth year but have a different biological age, some older and some younger than their chronological age.
In the past, scientists have built "epigenetic clocks" (aka a biochemical test to calculate biological age) to predict a person's mortality. For this study, they used epigenetic clocks to determine the effectiveness of the drug cocktail when it comes to biological aging.
Nine patients were put on a regimen that required they take one growth hormone and two diabetes drugs (dehydroepiandrosterone, or DHEA, and metformin). Researchers used four epigenetic clocks to determine the volunteers' biological age and, to their surprise, found the drug cocktail reversed biological aging by an average of 2.5 years. The results were consistent across each patient and each test – so while the exact number of years shed might vary across patients, each saw a reversal. What's more, blood samples provided by six patients six months after the trial showed the effects continued even though they had stopped taking the drugs.
"I’d expected to see slowing down of the clock, but not a reversal," Steve Horvath, a geneticist at the University of California, Los Angeles, told Nature.
Not only were the results unexpected, but they were the result of a study intended for something else. The researchers had originally designed the trial to find out if a growth hormone could (safely) rebuild tissue in the thymus gland, a key feature of an efficient immune system. (Which it can.) The antidiabetic drugs were included to counteract the added risk of diabetes accrued by taking the growth hormone. Testing its effect on biological aging was an add-on.
Still, as the researchers are keen to stress, the trial was preliminary and it remains to be seen whether or not the findings can be replicated. It is important to note that the trial was extremely small with just nine participants – all of whom were white, male, and middle-aged (51 to 65 years old). It will be interesting to see if the results are as consistent across different ethnicities, genders, and ages.
Gregory Fahy, the immunologist who led the trial, told Nature he believes the drugs in the cocktail might affect biological aging separately through independent mechanisms – something it may be possible to explore in larger trials.