How to reverse aging in muscles
"Mark Tarnopolsky: About 12 years ago people stumbled onto a serendipitous observation when they did muscle biopsies from patients who developed sporadic mitochondrial disease. So what happened was one of my colleagues simultaneously in Montreal and also in England, when they did a muscle biopsy and they took the biopsy and put it in culture what happened is that all the mature muscle fibres die and then there's a stem cell precursor called a satellite cell which represents about 2% to 4% of the muscle nuclei that are present. They start to grow and form a myoblast.
Norman Swan: This is the process of processing new muscle?
Mark Tarnopolsky: Correct, so what the two folks were hoping for was that they could then use this cell culture technique to study the biology of mitochondrial disease. But to their surprise what they found is that when they grew up the new muscle fibres they were completely normal. So in the mature muscle when they did a muscle biopsy there were deletions of the mitochondrial DNA, there was dysfunction, there was decrease in enzyme activity.
Norman Swan: So they rebooted the muscle in a sense?
Mark Tarnopolsky: Exactly.
Norman Swan: Inadvertently these researchers had renewed the muscle and purged it of the prematurely stuffed mitochondria. Somehow these satellite cells, the ones which were a bit like muscle stem cells, had remained aloof from the ageing process and when given their head so to speak regenerated normal muscle containing young mitochondria. And what seemed to have made this happen was the stress and injury caused by the muscle biopsy in the laboratory testing. Mark Tarnopolsky.
Mark Tarnopolsky: So when I heard this I was immediately interested in exercise as a more acceptable way of damaging the muscle and one that older adults may take advantage of. So we've done some experiments which we can talk about.
Norman Swan: In other words in some way by damaging the muscle you revive the mitochondria?
Mark Tarnopolsky: Correct. So what we've done was we've actually done muscle biopsies from young people and old people and we look in the mature muscle and the satellite cells. In the mature muscle what we find is that with ageing there is a reduction in mitochondrial enzyme activity, there's an increase in damage to the mitochondrial DNA so we see things called deletions, we see an increase in oxidative stress and when we do the myoblast cultures from the satellite cells we see none of this. So the older adult satellite cell seems to have a very young phenotype and it has no deletions and no damage. So our theory was that if we exercise people -
Norman Swan: They had the raw material to be able to produce decent muscle?
Mark Tarnopolsky: Exactly and we could bring in the good mitochondria, remove the old mitochondria because of the damage of exercise and in a sense shift down the bad mitochondria, shift them out.
Norman Swan: So what did you do?
Mark Tarnopolsky: So we trained older adults for six months twice a week for an hour.
Norman Swan: What sort of training?
Mark Tarnopolsky: It was weight training because with weight training you tend to get more damage to the muscle and the key here, what we feel is that you actually have to activate the satellite cells to get the benefit.
Norman Swan: This is what muscle builders and people who want to buff their body have known for years is that you've actually got to go over the hill to actually tear muscle fibres in order to build muscle?
Mark Tarnopolsky: Essentially that's true, I mean you may not have to cause frank damage, it may just be a high degree of strain but we do know that if you do for example marathon running, you're lean and you don't get muscle hypertrophy, the only way to get hypertrophy is to do a fairly high percentage of your maximum and doing few repetitions, for example we would say the one repetition maximum is your maximal, if you drop that to 70% and you do that ten or fifteen times with three sets that would be a typical set which would induce muscle hypertrophy.
Norman Swan: Now if you're not a gym junkie you probably don't have a clue what Mark's taking about. The idea is that you find out the maximum weight you can manage for one single movement, it's called a repetition, so if it's your biceps it would be lifting the weight with your hand toward you. Once you know what your maximal weight is you then drop down to about two thirds of that weight or less for your actual training. The training usually involves three rounds of ten or so repetitions of that exercise so if you can manage 5 kilos just once you'd probably start training on 2 or 3 kilogram weights then work up.
Mark Tarnopolsky: So we set out to do that in old people and we showed as folks have known since the 70s that there's an increase in strength and function in the older adults.
Norman Swan: Work in Tufts in Boston showed that with the extreme elderly in nursing homes.
Mark Tarnopolsky: Oh yeah, even folks into their 80s and 90s and what we found is that after the six months of training there actually is an increase in mitochondrial enzyme activity which doesn't happen in young people. These people were fairly active, walking their dog, playing tennis and doing recreational activity, clearly the weight training was more than what they normally did but it was no different to what activity our younger people had been doing when we've done weight training and yet with young people we never see an increase in mitochondrial activity. But if you think about it they have healthy mature muscle fibres with normal mitochondria so when you do weight training you just get a shifting of good to good. What's cool about the older adults is that -
Norman Swan: You've got the garbage disposal.
Mark Tarnopolsky: Right so there's a process called autophagy which removes the old damaged mitochondria, the new ones come in from these relatively acquired satellite cells and bang, we get an increase in mitochondrial function."