In 2012, Assoc Prof Eugene Du Toit and Dr Daniel Donner co-authored a chapter titled “Myocardial Insulin Resistance: An Overview of Its Causes, Effects, and Potential Therapy” in the text book Insulin Resistance published by InTechOpen.
The text book chapter discusses the causes of insulin resistance in the cells and tissues of the heart and describes the possible implications of these conditions for patients with varying metabolic diseases.
Insulin resistance refers to the body’s inability to react properly to normal levels of insulin, a key hormone in regulating the use or ‘uptake’ of sugars for energy in many (most) of our cells. Different tissues and organs can become insensitive or ‘resistant’ to insulin for a variety of reasons with each tissue’s dysfunction manifesting in myriad ways.
In the normal, adult heart, the metabolism (specifically ‘oxidation’) of fatty acids contributes the majority of the energy currency required for it to function. The heart is however incredibly flexible in its preference for different sources of this currency including glucose (a sugar), lactate, ketones and amino acids. These preferences can shift and change depending on the circumstance.
For instance, the foetal heart is known to prefer glucose over other sources of energy which shifts towards a preference for fatty acids following birth and into adulthood.
When adults do things that cause their heart to grow or ‘hypertrophy’ e.g. exercise, one hallmark of the larger heart is its partial shift back towards using glucose for energy.
And during a heart attack, when part of the heart muscle is starved of oxygen, one of the most important sources of energy is, again, glucose. Unlike fatty acids, glucose can be metabolised for energy in the absence of oxygen and is thus a vital and precious resource for energy during a heart attack.
The heart muscle or ‘myocardium’ undergoes complex metabolic and electrochemical responses to different conditions. This influences our approach to the development of new treatments and therapies for patients with varying constellations of diseases. This is an inherently complicated area of research, with new and critical information constantly contributed by medical research. This text book chapter is therefore a primarily introductory resource for researchers and clinicians, of most relevance in 2012 when it was first published. Review of additional literature is essential to grasping our current understanding of these issues.