The Heart-Brain Axis
EQUINE METABOLIC SYNDROME STUDY
The last two weeks have been relentlessly grey, damp and cold, making everything feel heavier and harder. Add this to the backdrop of negativity that is being poured onto any of us who engage with global news, it is no wonder that the general mood amongst the majority of people I have encountered over the last two weeks, has been low to say the least. It is at times like this that meeting and being around inspirational people is more important than ever to help lift our spirits. To be inspiring is not the same as being continually, and sometimes inappropriately, optimistic; for me inspiring people are those who, either on a grand or a modest scale, seek to make the lives of others around them better i.e. it is not just the story of ‘me, me, my’. In tricky times, being in the presence of these people can feel even more precious, as the contrast with the background noise is so marked. Perhaps even more important in trying times is to avoid prolonged exposure to those who display ‘parasitic’ negativity; these are the people who actively seek to infect you with their negative feelings, ultimately bringing your mood down to match their own. This ability for some people’s negativity to be contagious often arises from their often unexpressed feelings of jealousy, anger or envy, that can be directed at you, and if you are not aware of it, they can damage your psyche and drop your energy and resilience. Luckily for me, I have been in the presence of some extraordinary individuals over these two gloomy weeks, who have made it possible for me to maintain some psychic balance and make it through to today, Imbolc, the Celtic festival celebrating the first stirrings of spring, and return of the light.
Clusters of pathology are a common feature in clinical practice and recently I have witnessed a cluster of heart pathology amongst my human patients. Then as if in divine synchrony a paper, published in Cell on 27th January, lands in my inbox. The research that has recently been published has shown, in mouse models, that much of the damage from a heart attack is coming from signals from the brain and could be an important target of therapy for heart attacks in the future.
The interdependence of the brain and heart has become a major area of interest for some researchers, and the term ‘heart-brain axis’ (HBA) has entered the language and is now used to describe this bidirectional interplay. There is research dating back decades that makes the critical link between these two major organs of the body. Communication occurs through several interconnected pathways that integrate neural, hormonal and immune mechanisms, which together maintain cardiovascular homeostasis while influencing brain structure and function.
In this latest paper it is shown that, in mice at least, it is a brain-immune circuit that worsens cardiovascular pathology during and following a heart attack. Neurons in the vagus nerve relay signals between the heart and brain, which in turn activate immune and inflammatory responses that then cause widespread damage to the heart. They were able to demonstrate that blocking this crosstalk between the brain and the heart limited the damage to the heart following a heart attack. Heart attacks occur when the blood flow to areas of the heart become blocked or compromised.
The lack of oxygen to the heart muscle signals the brain creating a fight/flight response, meaning that the sympathetic nervous system is activated, which then causes inflammation that in turn impairs cardiac function. This activation was tracked to an area in the brain known as the paraventricular nucleus (PVN). The researchers were able to show that a subset of sympathetic nerves that connect to the heart increase their projections to the heart after a heart attack and carried increased levels if molecules released by immune cells including inflammatory cytokines.
Heart disease has always been associated with raised anxiety states in the patient, which at first glance might seem obvious, given how essential to life the heart is. This information shines a different light on this anxiety as it might be that the heart itself is creating the raised anxiety through direct signalling to the brain. Subtle changes in anxiety states in individuals where there are no obvious external drivers might be an early signal that the heart is in trouble and should be taken seriously perhaps?
EQUINE METABOLIC SYNDROME STUDY
I have mentioned Equine Metabolic Syndrome (EMS) in previous posts as the scourge of metabolic diseases in all domesticated species and humans is on the rise largely through changes in diet and lifestyle. Thus whenever we read about developments in another species it is well worth paying attention, even if you have never worked with horses in your life, as there may be things to learn about the disease in humans. Today I am reporting on a recently published study that looks at specific dietary supplements in the management of insulin in EMS affected ponies.
The defining feature of EMS is insulin dysregulation (ID), which may present as tissue insulin resistance, baseline or post eating high insulin spiking (postprandial hyperinsulinaemia). Equine obesity, that is estimated to affect 60% of the UK leisure horse population, also plays a significant role in the disease; sound familiar?
