High Cholesterol Causes Heart Disease? : Part 10

This is will be the final double post about cholesterol and heart disease. Today, I would want to share with you guys about how stress relates to autonomic nervous system, which then could lead to heart disease. Let's waste no time and dive straight into this crucial discussion. Now, because if the neurohormonal system gets seriously out of balance, you are likely to suffer catastrophic metabolic problems, then heart disease and other life-threatening disease such as cancer, diabetes, etc. 

The hormones involved on the 'stress' side include adrenaline, cortisol, growth hormone and glucagon. On the 'relaxation' side, for the purposes of this discussion, I shall concentrate on insulin. Release of stress hormones is controlled by the hypothalamus and pituitary gland acting in unison. Under a stressful situation, for instance, a man pointing a gun at you, the hypothalamus sends alarm messages to the pituitary gland, which then fires off hormonal messengers to the adrenal glands to get them release adrenaline and cortisol, among other things. 

This three part hormonal system, consisting of hypothalamus, pituitary gland and adrenal glands, if often referred to as the HPA axis. The HPA is intimately connected to, and intertwined with the autonomic nervous system. The autonomic nervous system has two divisions, the sympathetic and parasympathetic systems. Neither of these divisions is under your conscious control, unless you are some sort of expert Guru or master. 

The sympathetic nervous system has a wide range of actions. These include speeding up with heart rate, reducing saliva production and redirecting blood supply to your muscles. It also stimulates the liver to release glucose, thus pushing up blood sugar levels, and triggers the release of various clotting factors. These are the sorts of things you need when physical danger threatens, which is why this whole process is sometimes called the 'fight or flight' response. 

On the other hand, the parasympathetic nervous system has directly opposing actions. It slows your heart, stimulates insulin production and the release of bile. It also increases the flow of saliva, and directs blood to the guts to aid digestion. 

Well, another way to look at this is to say that an activated sympathetic nervous system is working in conjunction with raised 'stress' hormones, which represents 'catabolic' state. You have probably experienced this state after a physical activity such as tennis or badminton, when you know that you should be hungry, but find that when you sit down to eat, you have no appetite. Reason? The stress hormones are still ruling your metabolism, and are telling you that you are not yet ready to eat.

On the other hand, an activated parasympathetic nervous system, working in conjunction with a raised insulin level, represents the 'anabolic' state, a state in which you are ready to eat, digest and store energy. Within our bodies, we have these two systems, that are essentially directly antagonistic to each other. Anabolism and catabolism.

Remember this, if you are stressed, and then tried to eat, your metabolism would be thrown into confusion. You would be commading the neurohormonal system to activate catabolism and anabolism simultaneously. This would mean high levels of insulin. Adipose tissue would be under instructions to both absorb and pump out fats into the bloodstream. At the same time, the liver would be trying to store and release glucose. 

With food inside them, your guts would be automatically switched to 'absorption'. But, the sympathetic system would be fighting to direct blood away from the guts to the muscles. Wherever you looked, a fight for metabolic supremacy would be going on. Perhaps the most important battle would be for control of blood sugar levels, a battle ending up with  'spikes' of blood sugar, as insulin tried, and most likely to failed. 

In short, eating under stress was likely to be pretty unhealthy. Still munching on those whole grain breads while working out in the gym? Or egg whites and protein powder shakes immediately after workout session? 

Now, I will discuss the causes of dsyfunctional HPA axis in the following . Please do read carefully and try to understand as I try to be as non technical as possible. I do hope so. 

Causes of Dysfunctional HPA axis

Let's see. Probably the most dramatic dysfunction of the HPA axis occurs when a tumor develops in the pituitary gland, which then proceeds to pump out for too much in the way of stress hormones. Several types of these tumors can develop. A tumor producing too much of growth hormones can lead to gigantism, a tumor producing too much adrenaline can cause a condition known as phaeochromocytoma. 

In this discussion, I will focus on corticotropin, or also known as ACTH. ACTH is a precursor hormone, which in turn, stimulates cortisol secretion from the adrenal glands. So, a tumour in the pituitary gland effectively increases blood cortisol levels. This condition is known as Cushing's disease.

Cushing's disease, in turn, has a wide range of different effects, which are a direct result of the many actions that cortisol has around the body. Below are some of the examples:

• Triggers the liver to release its stores of glucose.
• Stimulates the breakdown of triglyceride stores in adipose tissue, leading to an increase in free fatty acids in the blood.
• Activates breakdown of muscle protein into amino acids.

People with too much cortisol surging about in the system, have high blood sugar levels, and a high degree of what is known as insulin resistance. In fact, most people with Cushing's disease develop diabetes. People with Cushing's disease also lose muscle bulk, due to breakdown of muscle proteins.

There is also a redistribution of fat from the periphery, which is arms and legs, to the abdomen. The reason why this happens is because you have two very different types of fat in your body. Both of these fats are known as visceral and subcutaneous. Subcutaneous fat sits just underneath the skin, and is found all over the arms, legs, neck, etc. Sumo wrestlers have lots of this type of fat.

Visceral fat, on the other hand, is mainly found around the organs in your abdomen. It is the type of fat that builds up in those who develop 'beer belly'. While both types of adipose tissue can each store and release fat, that is the beginning and end of any similarity.

From a metabolic perspective, one is fat, one is anti-fat. I will try to explain this as plain and layman as possible, as both is enormously complex. Cortisol stimulates subcutaneous adipose tissue to release fat, thus, making it shrink in size. On the other hand, cortisol stimulates visceral fat to do the exact opposite, by storing fat.

Now, what causes visceral fat to build up and accumulate in our body? Can anyone tell me? The thing is, visceral fat doesn't just build up by itself. No matter how you would believe or heard from whichever media or source, it doesn't just accumulate or sort of happens. And no, it is not due to genetic susceptibility as well.

Stay tuned to find out...I'm just darn tired to continue writing.