Episode 17: October 7, 2009
by Dr. Rob Lamberts, M.D.
Today’s topic is Diabetes. This disease is one of the most serious and costly diseases, and it is becoming more common. But even though nearly everyone has heard of diabetes, most don’t really understand it--including many people who have diabetes. So today I’m going to imitate Bill Nye and explain the science of the disease. I find that my patients who really understand their disease do much better in controlling it.
What is Diabetes?
The term diabetes actually doesn’t describe a single disease. The word comes from a Greek word meaning to pass through. Before diseases like diabetes were understood, doctors would describe what happened when people had them. Long ago, somebody noticed that certain people drank a lot of liquids and then put out a bunch of urine. They labeled these people as having diabetes because the fluid passed right through them.
Now as disgusting as it sounds, somebody noticed something else about these people: their urine tasted different. You didn’t hear me wrong. One group had urine that tasted very sweet. They labeled those people as having diabetes mellitus, as mellitus means sweet. Another group had normal tasting urine, and so they labeled these people as having diabetes insipidus, with insipidus meaning insipid, or bland. Don’t ask me why they tasted urine. It goes to show what people will do with too much time on their hands.
The type of diabetes I am focusing on today is diabetes mellitus, as diabetes insipidus is really rare. But even diabetes mellitus doesn’t describe a single disease. There are two main types, given the clever names: Type 1 and type 2 diabetes mellitus. Before I explain these two diseases, however, I need to give some more basic information.
What Do Glucose and Insulin Have to Do with Diabetes?
There are two stars in the diabetes mellitus show: glucose and insulin.
The cells in your body need a regular supply of energy to function. Their favorite food is a sugar molecule called glucose. Pretty much any carbohydrate you eat either has glucose in it, or it has other sugars that can be converted to glucose. When you eat carbohydrates, the carbohydrates are broken down in your intestine into glucose and then absorbed into your bloodstream.
Insulin is a hormone put out by your pancreas to make sure the glucose goes from your bloodstream to where it is needed.
How Your Body Uses Glucose
Let me give an analogy that will help make this easier to understand. Our home has a furnace that makes heat by burning natural gas. Now, we could have a huge tank in our back yard to store the gas, but it is far easier to tap into a pipeline that will deliver it to us when we need it. In the same way, the cells of the body don’t store much glucose in their backyards. Instead, they tap into the body’s pipeline system: the bloodstream.
The cells of the body tap into the body’s pipeline system-- the bloodstream--when they need glucose.
When the cells need energy to do their specific job, they get glucose from the bloodstream; then they combine it with oxygen--or burn it--to create energy, carbon dioxide and water. That is actually the exact same thing that happens in the furnace, just on a much smaller scale.
The Glucose Insulin Connection
Let’s say a muscle cell or nerve needs to do some work. All cells have access to the bloodstream, and so can get glucose whenever they want. How do they get the glucose? They dangle special proteins, called insulin receptors, in the bloodstream. That is basically like a big "I need glucose" sign put on the surface of the cell. Insulin, which, remember, is made in the pancreas, gets the memo and moves from the pancreas to the bloodstream where it binds with the insulin receptors. When the insulin binds to the insulin receptors glucose can then move from the bloodstream, into the cells.
Insulin receptors also keep your blood sugar levels from getting too high. So if you ignore the Nutrition Diva and eat a bag of jellybeans, the sugar will go from your intestine into your bloodstream. This sugar-saturated blood then passes by the pancreas and into your liver. In response to this sweet assault, the pancreas puts out insulin, and the liver cells put out insulin receptors. These hook up and send the sugar into the liver cells, where it is stored for future use by the cells.
Let me summarize to keep this from getting confusing:
Cells burn glucose for energy.
They put out insulin receptors when they need more fuel to do their jobs.
Insulin binds with insulin receptors which lets glucose into the cells
The liver stores excess glucose and keeps blood sugar levels stable.
What is the Difference Between Type 1 Diabetes and Type 2 Diabetes?
But in diabetes mellitus, this process goes wrong. The two types of diabetes differ in where this process breaks down.
Type 1 diabetes (also called juvenile onset diabetes) happens when the body stops making insulin. Without insulin, the cells starve because they can’t get glucose. The sugar levels in the bloodstream also go up because the liver is prevented from taking the glucose out of the bloodstream and storing it. Only 5-10% of diabetics are type 1.
Type 2 diabetes (also called adult onset diabetes) is by far more common than type 1. In a type 2 diabetic, the insulin receptors become defective and so instead of reading "I need glucose," they read, "I need gulcose." Some of the insulin doesn’t bind with this defective receptor, not realizing that "gulcose" is actually "glucose." Initially this is OK, because the pancreas puts out more insulin and enough of it recognizes the defective receptor so that things stay normal.
But as time goes by, these receptors gets more and more defective, requiring more and more insulin to overcome this defect and get cells the glucose they need. When the pancreas can’t put out any more insulin, the glucose in the blood doesn’t go to the cells or the liver, and so blood sugar levels in the bloodstream go up.
Why do the insulin receptors get defective? Researchers are trying to figure that out, but genetics clearly play a big role in this.
Just in case your head is swimming, I’ll summarize:
Type 1 Diabetes happens when the body stops making insulin.
Type 2 Diabetes happens when insulin receptors mess up.
In both types, the cells starve for glucose while the blood sugar levels in the bloodstream go up.
Whew! I am done with the biology lesson. So what’s the big deal? Why is all of this important? Those high blood sugars cause all sorts of trouble in your body--kind of like when someone puts sugar in the gas tank of a car. It messes things up big-time, leading to bad consequences, such as:
Kidney damage leading to kidney failure
Nerve and blood vessel damage that leads to ulcers in the feet, and eventually amputation.
I am stopping here. In my next diabetes article I’ll discuss more about these consequences, the risk factors of the disease, and what you can do to keep from getting diabetes.
If you have questions you want answered, send them to firstname.lastname@example.org. You can find me on Twitter as @housecalldoc and on Facebook under "House Call Doctor."
Remember: this article is for informational purposes only. My goal is to add to your medical knowledge and translate some of the weird medical stuff you hear, so when you do go to your doctor, your visits will be more fruitful. I don’t intend to replace your doctor; he or she is the one you should always consult about your own medical condition.
Catch you next time! Stay Healthy!