The elderly have to work hard for it, but their muscles can have a metabolism almost similar to that of young adults. This is shown by research by Maastricht University and Amsterdam UMC published in Nature Aging. UM researcher Joris Hoeks: ‘It concerns older people who really exercise vigorously.’
When studying the muscle tissue of young and old people, one substance clearly stood out: nicotinamide adenine dinucleotide (NAD⁺). It is less present in older people, especially if they exercise little. Hoeks: ‘The amount of NAD⁺ scales very nicely with the functionality and health of the muscles. Older people who do a lot of sports have levels similar to those of young adults.’
According to Hoeks, the substance is already well known from aging research in laboratory animals. ‘There you also see that it occurs less in older animals, and that at the same time the function of cells decreases. If you administer NAD⁺ as a supplement, worms live longer and mice get fewer metabolic diseases.’ Whether manipulating the amount of NAD⁺ in people ensures that we age in a healthier way is impossible to say on the basis of this research.
The researchers were not specifically looking for the substance NAD⁺ beforehand. ‘By mapping the metabolism in the muscles of different groups of people, we wanted to gain more insight into the aging process and how people can grow old in a healthier way.’ To do this, the researchers compared the metabolism of young adults (20-30 years) who exercise on average with that of three groups of elderly (65-80 years) with different fitness levels. Varying from people who move minimally and, for example, have difficulty getting up from a chair, to people who exercise at least three times a week. ‘Cycling to the city or supermarket or a walk through the park or forest doesn’t count. This concerns older people who swim, cycle or run fanatically,’ says Hoeks. ‘And who take an average of more than 13,000 steps a day. I certainly don’t get that every day.’
A muscle biopsy was taken from all subjects to measure the levels of 137 different metabolites in the muscle tissue and to see to what extent these occurred in the different groups. NAD⁺ immediately stood out. ‘NAD⁺ is mainly located in mitochondria: the power stations of a cell. Nutrients that someone ingests are converted there into energetic molecules that cells can use.’ The functioning of mitochondria, like the levels of NAD⁺, declines with age. ‘But it is too early to say whether this is cause and effect,’ says Hoeks.
profit to be made
People who continue to exercise on average are likely to become less fit with age. ‘The group of elderly people who exercise on average turned out to be remarkably active and took about 10,000 steps a day. This group therefore largely meets the exercise guidelines for the general population. Still, compared to young adults, we see a clear reduction in NAD⁺ levels. So you really have to make a considerable effort in terms of sport to eliminate that.’
Whether exercising more at a later age can actually reverse the aging process in muscles is still unclear, according to Hoeks. ‘For this you should offer people an exercise program, while you follow them for weeks.’ The same applies to the administration of NAD⁺. ‘Increasing NAD⁺ levels through nutritional supplements or a modified diet has already been done in humans. So far, those studies have not been very successful. But it may be effective in combination with exercise. Certainly in the elderly with limited physical fitness.’ Future research should show whether profit can be made there.