MIGHTY
MITOCHONDRIA
(AND WHY YOUR CLIENTS SHOULD LOVE THEM)
The often forgotten ‘powerhouse’ of the cell, the more mitochondria we have, the lower our risk for
developing many chronic diseases. So how can we get more of them?
WORDS: TONY BOUTAGY PhD
he vast majority of focus in the fitness industry is on skeletal
muscle and its ability to contract, with the emphasis on
how to make it bigger, stronger and more functional.
The often forgotten aspect of muscle is the mitochondria. Often
called the ‘powerhouse’ of the cell, for its ability to oxidise fuel
sources to create energy, mitochondria are critical for health and the
evolution of the human species. The more mitochondria we have, the
lower our risk for developing many chronic diseases. The average
individual may have literally billions of mitochondria in their skeletal
muscles, and the trained individual even more. It has been estimated
to comprise around 10 per cent of an individual’s body mass.
Given the strong relationship between mitochondria and
healthy ageing, it makes sense to further our understanding of the
microscopic world of this ancient ‘bacteria’ by exploring how the
body grows them, the contribution of exercise to their development
and function, and the role nutrition plays in keeping them healthy.
T
Mitochondria – five decades ago
50 years ago, pioneering research by John Holloszy showed, for
the first time, that endurance training could cause an increase in
the number of mitochondria found in the muscle of rats. Holloszy
discovered increased oxygen and energy utilisation in rats that were
exercised on a treadmill compared to their sedentary peers, and it
was this finding that explained their improved endurance fitness.
Since 1967, our understanding of mitochondrial regulation in
muscle has progressed rather slowly until modern times, when
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advancements in molecular biology have allowed researchers to
use state-of-the-art techniques to measure the cellular triggers
causing the growth and expansion of new mitochondria, termed
mitochondrial biogenesis.
It is now understood that our mitochondria is regulated by a complex
interaction between several ‘energy sensors’ in the muscle and ‘co-
activators’ which cause the proteins to become transcribed and formed
into mitochondria. The primary energy sensor in the muscle is a kinase
called AMPK. Muscle contraction (both intensity and duration), as well
as the ‘energy status’ of the muscle (i.e. depleted levels of glycogen)
cause the activation of AMPK. This, in turn, upregulates the co-activator
PGC-1α to start the process of mitochondrial biogenesis.
There has been incredible interest in recent years in exploring
the AMPK/ PGC-1α pathway in mitochondrial biogenesis, as
mitochondrial dysfunction is now regarded as an important
component of different diseases associated with ageing, such as
type 2 diabetes and Alzheimer’s disease. It has also been shown that
AMPK activity decreases with age and sedentary lifestyles, which
may contribute to decreased mitochondrial biogenesis and function
with ageing and disuse.
Exercise and mitochondria
Muscle contraction during exercise increases the activity of AMPK
(which detects falling energy availability in the muscle), which, in
turn, increases the expression of PGC-1α and signals the growth and
proliferation of mitochondria.