Type 2 Diabetes: The Vicious Circle

Type 2 diabetes does not always require insulin injections, but this form of the disease is the more insidious. Type 2 diabetes is sometimes only diagnosed after it causes a serious complication, such as loss of sight or ulceration of a foot or leg. Like type 1 diabetes, type 2 diabetes has both a genetic component and an environmental trigger. And type 2 diabetes develops in a vicious circle of events.

Some people are born with a genetic defect—actually a genetic characteristic that confers greater likelihood of survival between conception and birth—that causes every cell in their bodies to react to insulin in an unusual way. The outer membrane of every cell in the body holds proteins that act as a lock for which insulin is the key. These receptors grasp insulin and take it inside the cell. In people who are prone to type 2 diabetes, cells reduce the number of receptor sites for insulin if the amount of insulin in the bloodstream increases. That is, if they body makes more insulin, cells change so that they are less, rather than more, able to respond to it.

When people with this genetic characteristic gain weight or become physically inactive or have to spend extended time recovering from illness or injury, a vicious cycle sets in. Increased body fat, especially over the abdomen, physically blocks the flow of blood to the fat cells that ordinarily store and convert sugar. Since glucose cannot reach fatty tissues, it remains in the bloodstream. The pancreas senses the additional sugar and makes more insulin. The additional insulin, however, causes fat cells to lose insulin receptor sites. Both sugar and insulin stay in the bloodstream, and cells lose still more insulin receptor sites, so the pancreas produces still more insulin.

Even when people have a genetic tendency toward type 2 diabetes and become overweight, however, diabetes is not necessarily inevitable. Vigorous daily exercise maintains circulation. If increased circulatory health keeps the blood flowing, the fat cells that use insulin to “catch” circulating glucose and turn it into fat can keep blood sugar levels normal. Alternatively, expanded muscle mass, also from exercise, enables muscle cells to use more glucose and also keep bloodstream glucose levels low.

But when overweight people with a hereditary tendency to diabetes become inactive diabetes results. Even while cells all over the body are losing their ability to respond to insulin, fat cells undergo changes that make them accumulate fats more readily but release them more slowly, compounding poor circulation caused by lack of exercise. As fat cells become “stuffed” with triglycerides, even if sugar reaches them, they cannot process it. Gaining weight becomes easier. The muscle cells are forced to do more and more of the work of keeping blood sugar levels normal, even while their own insulin resistance eventually forces them to use fats and their own proteins for fuel.

The metabolic disruption caused by diabetes affects every cell of the body, but especially the eyes and nervous system. Unlike other tissues, the eyes, the brain, and the nerves do not have to rely on insulin transporters as their only way to receive glucose fuel.

When blood sugars are high, glucose pours into these tissues faster than they can use it, and toxic waste products build up. For this reason, especially in type 2 diabetes, the first obvious symptoms are usually psychological. Excess sugar “revs up” the brain so that many untreated type 2 diabetics appear slightly manic, with racing thoughts, racing speech, and a “go-go mind with a so-so body.” Having too little energy for too much to do is a good time to see a doctor to make sure you do not have diabetes.