Stress, Health & Disease - Why Zebras Don't Get Ulcers (ch4)

Chapter 4: Liquidating your assets

In cases of crisis (e.g. running away from a lion), your cardiovascular system kicks into high gear and is delivering oxygen and energy to your exercising muscles.

Where does the extra energy come from?

• By digestion, complex food matter is broken down into smaller building blocks (e.g.: amino acids, glucose) . These building blocks can be burned by the body to provide the energy to do constructions and operate new structures
• In immediate physical emergency, your body stops storing energy (digesting). The activation in your sympathetic nervous system is turned up, and the parasympathetic is turned down, along with the insulin secretion.
• With the onset of the emergency, you secrete glucocorticoids, which block the transport of nutrients into fat cells
• Stored nutrients are converted into a simpler form. Then, amino acids are converted into glucose, as it is a better source of energy. This glucose is now readily available for energy during the disaster.
• Not being able to mobilize during crisis is a characteristic of Addison’s disease, where people cannot secrete adequate amounts of glucocorticoids, or in Shy-Drager syndrome, where it is epinephrine and norepinephrine that are inadequate

Why do we get sick?

• Every time you store energy away from the circulation and then return it, you lose some of the potential energy. It takes energy to shuttle nutrients in and out of the bloodstream to power the enzymes that glue them together. As a consequence, you tire more easily
• Your muscles may waste away. If you are stressed chronically, your muscles never get the chance to rebuild
• Having lots of fat and glucose perpetually circulating in your blood stream increases your chances of it glomming on to some damaged blood vessel and worsening atherosclerosis.
• If you are stressed too often, the metabolic features of the stress-response can increase your risk of cardiovascular disease.

Juvenile diabetes

• Also called type 1 or insulin dependent diabetes
• Because a person with type 1 diabetes can no longer secrete adequate amounts of insulin, there is little ability to promote the uptake of glucose into target cells. Cells starve, there’s not enough energy and organs don’t function right
• The hormones of the stress-response cause even more glucose and fatty acids to be mobilized into the bloodstream, which, for a juvenile diabetic, increases the likelihood of pathologies of glucose and fatty acids gumming up in the wrong places
• Stress promotes insulin resistance, which creates an imbalance within the body
• Stress,  including psychological stress, can wreak havoc with metabolic control in    a juvenile diabetic
• There are higher rates of major stressors suffered by people during three years before the onset of their juvenile diabetes than would be expected by chance

Adult-onset diabetes

• Also known as type 2, non-insulin diabetes, involves the failure to respond to insulin
• Arises from the fact that many people gain weight as they age. Once you are an adolescent, the number of fat cells you have is fixed, so if you put on weight, the individual fat cells are distended.
• All the circulating glucose and fatty acids damage the blood vessels
• The fat cells become less responsive to insulin. The pancreas responds by secreting even more insulin than usual. This leads to the insulin-secreting cells to burn out in the pancreas, destroying them.
• Even if you get your adult-onset diabetes under control (e.g. with exercise and losing weight), you will develop juvenile diabetes because of your damage to the pancreas
• Stress-response causes your fat cells to be less responsive to insulin, which worsens the diabetes

Metabolic Syndrome (Syndrome X)

• The metabolic and cardiovascular systems are interconnected. The term “metabolic syndrome” refers to this interconnection
• It involves several symptoms (e.g.: insulin resistance, too much cholesterol in the blood)
• The symptoms together predict a high chance of disease
• It shows that even if there’s no single measure that’s certifiably wrong, if there are many things that are at the verge of abnormal, that is enough to predict a health problem

Resources: Sapolsky, R. Why zebras don’t get ulcers: The acclaimed guide to stress, stress-related diseases, and coping. New York (NY): Henry Holt and Company. 2004 3rd edition