Exercise hormone injections boost mice fitness and overall health

January 26, 2021

It would be ideal if there was a way to beat the hassle of exercise, but still maintain health and fitness. Scientists at the University of Southern California (USC), US, might have found just that – an exercise hormone administered to mice appears to improve fitness and overall health, even in older mice.

The hormone, MOTS-c, is released by the human body during exercise. It is encoded not by the main genome in human cells but the mitochondria, which have their own smaller genome.

“Mitochondria are known as the cell’s energy source, but they are also hubs that coordinate and fine-tune metabolism by actively communicating to the rest of the body. That communication network seems to break down as we age,” said Changhan David Lee, assistant professor at the Leonard Davis School of Gerontology at USC.

First, the USC scientists took samples of skeletal muscle and plasma before, during and after exercise from 10 healthy male volunteers, to measure levels of MOTS-c. In skeletal muscle, MOTS-c levels significantly increased by 11.9 times after exercise, and although they trended back towards the baseline over time; MOTS-c in plasma was also elevated by at least 50% after exercise, but dropped to baseline faster.

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Next, the scientists injected MOTS-c into mice of three different ages – two-month-old young mice, 12-month-old middle-aged mice, and 22-month-old elderly mice – for two weeks, and then had them perform tests on a rotating rod and a treadmill.

Intriguingly, in all age groups, the treated mice performed significantly better than controls. Even the elderly mice appeared rejuvenated by the treatment, with improved grip strength, gait and walking abilities.

“The older mice were the human equivalent of 65 and above and once treated, they doubled their running capacity on the treadmill. They were even able to outrun their middle-aged, untreated cohorts,”adds Lee.

In a follow-up experiment, mice were fed a high-fat diet to mimic instances of high metabolic stress, and treated with different dosages of MOTS-c twice a day. After seven days of treatment, the mice had improved insulin sensitivity, which lessens their risk of diabetes. They also gained less weight on the high-fat diet than untreated mice.

After 10 days, mice on the higher dose of MOTS-c were running further and burning more energy than untreated ones. In fact, 100% of the higher-dose mice were able to complete the final treadmill test – sprinting 23 m (75 ft.) per minute – whereas only 16.6% of mice in the lower dose and control groups managed the feat.

“Indicators of physical decline in humans, such as reduced stride length or walking capacity, are strongly linked to mortality and morbidity,” said Lee.

“Interventions targeting age-related decline and frailty that are applied later in life would be more translationally feasible compared to lifelong treatments – essentially to help older people stay healthier for longer.”

Tags: exercise, fitness, health