Blood as the elusive ‘fountain of youth’?
The existence of a mythical ‘fountain of youth’ and the quest to locate this is a centuries old tale. Recent scientific discoveries have suggested that “young blood” may be the anti-ageing serum long sought after. A series of studies since 2005, culminating in a ground-breaking publication in Nature Medicine in 2014. In this study, older mice were treated with blood from younger animals where it was demonstrated that this “young blood” could reverse the cognitive impairments and reduced synaptic plasticity (associated with learning and memory) connected with ageing. This research used an interesting technique where the circulation of the young and old mice were co-joined by suture, in a process known as parabiosis. Essentially, the two animals shared the same blood supply. Parabiosis of these older mice with their younger counterparts led to a reversal in the loss of their cognitive function with age. Effectively, they were rejuvenated! So, what are the properties of young blood which leads to these improvements? Is it one factor or several?
What is in blood?
It is probably best at this point to describe what blood is made up of. Human blood is comprised of blood cells suspended in a fluid known as plasma. The blood cells are made up of red blood cells which are responsible for carrying oxygen, white blood cells which are involved in the function of the immune system and platelets which are responsible for clotting to prevent blood loss through injury. The plasma contains proteins, nutrients, hormones, minerals and gases required by all cells for survival. It also contains small packages known as vesicles which transport material which facilitates a sort of long distance communication between tissues.
What does the blood represent?
Therefore, the blood in some ways represents the health of the function of the overall system as it is the environment in which our cells exist. This can be impacted by our genetics, by disease, but also by our external environment and behaviours. For example, our physical activity and exercise regimens can influence the makeup and activity of the blood, and thus, effect the health and function of all cells in the body.
How does exercise influence blood?
The primary function of skeletal muscle is to support locomotion and movement. Relatively recently, the muscle was discovered to also be an active endocrine organ, releasing factors such as proteins (known as myokines) and vesicles containing important material (DNA, mRNA, small proteins) which can regulate the function of other tissues in the body. When we consider this, it makes perfect sense, the muscle cannot act in isolation, requires cooperation with other tissues and the blood represents the medium for this communication. As physiologists we refer to this as crosstalk. The minutes and hours after exercise represents a particularly active period when the muscle is releasing myokines and vesicles to the circulation.
PESS research using human blood to treat muscle
In the Human Sciences Research Group here in the Physical Education and Sport Sciences department at UL, we are interested in optimising muscle metabolism for both health and performance, including prevention of the loss of muscle mass (sarcopenia) associated with ageing. We have recently developed a model to regulate muscle metabolism (here), similar in concept to parabiosis, but at the cellular rather than whole body level. What we are doing is influencing the makeup of the blood of both young and older participants through different interventions such as feeding and exercise. For example, we can exercise a young healthy adult, and extract blood during the post-exercise period when the muscle is particularly active in releasing myokines and vesicles to the circulation. We can then use that blood to condition the media in which we grow muscle cells in culture and monitor the effect this then has on the muscle. Similarly, we can feed an athlete or older adult a particular nutrient, and extract their blood in the fed state to treat these muscle cells in the same way. This enables us to investigate the role of exercise and feeding on muscle metabolism. This is a far more advanced way of treating muscle cells than just applying a single myokine or nutrient of interest direct to the muscle cells, as that is never what will happen in human physiology. The blood represents the integrated milieu of several factors and is a more relevant means of conditioning these cells. This can help us understand how exercise and nutrition prevent the effects of ageing, such as sarcopenia. We are also using different exercise paradigms including endurance, sprint interval and resistance training to investigate the time course and release of novel myokines.
If you are interested further in this area I have included some video and content at links below
Human Sciences Research Group Video
- PESS Model to study muscle metabolism
- “Contraction-induced myokine production and release:
is skeletal muscle an endocrine organ?” - “The potential of endurance exercise-derived exosomes to treat metabolic diseases”
- “The Fountain of Youth: A Tale of Parabiosis, Stem Cells, and Rejuvenation”
- “Fountain of Youth? Young Blood Infusions “Rejuvenate” Old Mice”
Dr Brian Carson is a Lecturer in Physiology and Course Director for the BSc in Sport & Exercise 
Sciences in the department of Physical Education & Sport Sciences at the University of Limerick. His current research interests include the plasticity and metabolic adaptation of skeletal muscle in response to physical activity and nutrition. Contact Brian via email at brian.carson@ul.ie or follow Brian on TWITTER
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