Welcome to Part 2 of my “freshman lecture” on Diabetes.
Now we get to Type 2 Diabetes Mellitus. Interestingly enough, although this is “Type 2”, it is in fact by far the Number 1 form of Diabetes numerically, with 90 to 95% of Diabetics falling into Type 2…and that number is likely, if anything, to become larger.
Individuals with Type 2 Diabetes do produce insulin, despite what you might think. In fact, oddly enough, many of them produce way MORE insulin than is good for their bodies. So what’s the problem, how can they be Diabetic? Well, the problem in Type 2 Diabetes involves insulin resistance by the cells of the body…especially the fat cells.
This insulin resistance usually starts off as just a sort of predisposition, where some people’s cells respond to insulin a bit more sluggishly than others. At first this doesn’t produce any obvious clinical results, because the pancreas responds to that sluggishness by just putting out more insulin when the glucose doesn’t get taken up fast enough. Unfortunately, this only works for a little while. That’s because the insulin resistance tends to increase as the cells respond to the higher amounts of insulin. In a way, they get used to it, rather like someone losing their hearing when being surrounded by loud noise all the time. Eventually, despite the fact that the islet cells are putting out way more insulin than they would in a healthy state, the body just stops responding well to it at all, and the blood sugar goes above normal levels. This is the clinical onset of Diabetes Type 2, but I think you can see that the real disease starts a long time before this happens.
Type 2 Diabetes is only very rarely associated with the horror of ketoacidosis, but that doesn’t mean it doesn’t have horrors all its own, and though they are subtle, they affect far, FAR more lives than any aspect of Type 1 Diabetes. Long before the blood glucose starts to goes up, individuals heading toward Type 2 Diabetes have chronically elevated blood insulin levels, and this has effects on more than just the blood sugar. It leads to elevation of serum triglycerides, for one thing, and as you may know, this is one of the “bad” forms of lipids (often collectively referred to as “cholesterol” though that’s not strictly accurate). The triglycerides in particular—and elevated insulin itself—increase the risk of coronary artery disease and other vascular diseases, and it’s probable that the chronically high insulin contributes to an increased risk of hypertension (also known as high blood pressure). The heart, the kidneys, the blood vessels, the eyes…eventually all the systems of the body are damaged by these processes.
Once the blood sugar is elevated, the overall effects of Type 1 and Type 2 Diabetes overlap a great deal, except as discussed above. Unfortunately, having extra blood sugar, as you might guess, doesn’t give a person extra energy. Quite the contrary, it usually leads to low energy, partly through dehydration as the sugar spilled in the urine takes water away with it, and partly from a simple inability of the body to use the glucose appropriately. People with untreated Diabetes tend to lose weight, but it’s not a good kind of weight loss. They lose lean body mass for one thing, and lean body mass is the tissue that responds best to insulin and helps lower the blood sugar and improve the overall health.
People with Diabetes also, unfortunately, develop a lot of complications from having just too much sugar throughout their system. You see, sugar is not a completely benign substance. Your mother probably made this clear to you long ago, but you may not realize just why it’s so. Glucose is a very chemically active substance, which is why it’s useful as a source of energy. But when it’s around in large quantities for a long period of time, it tends to react chemically with things with which we don’t really want it to react. For one thing, it binds very nicely—without any help—to various kinds of proteins, and then doesn’t tend to unbind itself. This can actually be useful in measuring how the long-term blood sugar has been, and is the subject of a test called the hemoglobin A1C, which measures how much of a certain type of glucose-bound-hemoglobin there is in the blood, giving a good estimate of how the blood sugar has been over about the last 4 months (Why four months? Red blood cells live about four months in the body, and they are where all the hemoglobin is).
Still, glucose binds to lots of other proteins in much less useful ways than this, and over time this binding tends to create dysfunction in the proteins, and in the structures of which they are part. Such binding happens in the proteins that make up small blood vessels—such as those that feed nerve endings, for instance—narrowing those vessels down until the nerve endings or any other tissues the vessels supply start to die. This (plus a bit of contribution from thickening of the vessel walls due to elevated insulin in the Type 2 Diabetes patient) is the cause of “Diabetic Neuropathy,” a numbness that develops, usually starting in the extremities and working its way up. Though the inability to feel pain might sound nice at first, it leads people to be unaware when they have, for instance, developed blisters and cuts on their feet. Cuts and blisters that are unknown tend to be untreated and thus prone to infection. To top that off, the elevated blood glucose itself makes a person with Diabetes an especial treat for many kinds of bacteria, and it interferes directly with the function of the immune system. This combination of factors leads many uncontrolled Diabetics to face the frightening prospect of infections that cannot be adequately treated and that lead to amputations.
Elevated blood sugar also affects the eyes in a number of ways: The effects of elevated insulin and sugar narrow the arteries in the retina (the sensing surface on the back of the eye) and lead to various consequent visual problems. In addition, the sugar causes fogging of the lens of the eye as it binds with proteins there, producing cataracts.
The kidneys, dealing with the high load of fluid and with the glucose that gums up its complex structure by binding to the proteins—complicated by the often-coexisting problem of high blood pressure—tend to deteriorate under the influence of Diabetes, and many Diabetics progress to kidney failure, requiring dialysis to stay alive.
There are, of course, many treatments available for the complications of Diabetes, though none are quite perfect. There are also treatments for Diabetes itself. Type 2 Diabetics can receive extra insulin to help overcome their insulin resistance, but this extra insulin can cause problems of its own and tends to lead to weight gain…and that gain is often in the fatty tissues, which leads to increased insulin resistance, and so the spiral continues.
There are medications—called sulfonylureas, not that the name is that important here—which stimulate the pancreas to release more insulin in response to blood glucose. But as with giving extra insulin from outside, this tends over time to increase resistance and can thus only go so far.
There are a number of other medications that can help with Type 2 Diabetes. Some suppress the liver’s uncontrolled creation of new blood sugar when it’s not responding to normal suppression by insulin. Some try to increase the body’s cells’ sensitivity to insulin. These medications all have their place and they all work to one degree or another. Yet none of them work as well as avoiding Diabetes in the first place, when possible.
Yes, in many people Diabetes can be avoided and/or largely corrected by some simple changes in lifestyle—well, they’re simple in concept, though carrying them out requires willpower and determination. The main interventions are: diet and exercise. Simply put, keep the intake of simple carbohydrates (that’s sugars and white starches, basically) to a minimal amount, and do regular exercise, especially aerobic exercise (exercise where you keep moving without break, such as walking, swimming, running, biking and so on) three or more times a week for a good half hour or more at a time. Of course, if you have underlying health problems, you need to check with your doctor before starting an exercise routine, and you certainly shouldn’t try to achieve Olympic level results right from the start. But the problems of Diabetes in individuals who are predisposed CAN often be minimized and even sometimes reversed by appropriate lifestyle choices, for as long as those choices are continued. It’s not literally a cure, but it can sometimes be the next best thing.
Well, this has been a very quick rundown of Diabetes, aimed at those who don’t know much more than the term itself and that it’s related to high blood sugar (and is NOT a good thing). I hope it’s answered some questions and…just maybe…stimulated some new questions in the reader. If you have any such questions, please, by all means, leave a comment with your question, whether it’s about something you’d like to know more about or just about something I wasn’t clear enough on in my explanation. I’d be delighted to respond.
Trying to help more people understand more about medicine and science is, after all, the whole reason I’m doing this.