ByToby SmithsonandAlan L. Rubin Diabetes mellitus is defined simply as having higher than normal levels of glucose in your blood too often, a condition called hyperglycemia. Blood glucose is sometimes calledblood sugar, but glucose is a very special sugar when it comes to diabetes. For the sake of accuracy,blood glucoseis the correct terminology. The actual wordsdiabetes mellitusare Greek and Latin, loosely translated to mean constantly flowing sweet urine. Frequent urination is a common symptom of diabetes as your body works to remove excess blood glucose through your kidneys, and it’s reasonable to assume that urine would be sweet. In fact, tasting urine to detect the sweetness of excess blood glucose was a diagnostic test that doctors would perform in the days before the chemistry was well understood. Fortunately, there are now better ways to detect hyperglycemia than urine tasting. Whereas there are several different ways a person can acquire diabetes — injury or damage by toxins for example — type 1 and type 2 diabetes are the most common “natural” forms. Explaining the role of glucose diabetes Glucose is a sugar; in chemistry terms, a “simple” sugar or monosaccharide. There are many chemical varieties of sugars; for example, you’ve probably heard of fructose and lactose. But glucose is especially important because it’s your body’s favorite fuel to provide the energy needed for activity like muscular movement, body heat, and, most importantly, brain function. You may see your brain as mostly important for thinking, but there are many really important activities that depend on signals from your brain that happen with no thinking required. Your brain accounts for 20 percent of your energy use, some of which goes to support rather important activities like automatically breathing. Sugars are unique chemical compounds. Glucose and fructose, for instance, have exactly the same chemical formula with 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms — C6H12O6— but differ remarkably because the chemical bonds between the carbon atoms and other elements are very different. Fructose is much sweeter in taste and doesn’t raise blood glucose levels except slightly from a small amount of fructose that is converted to glucose in the liver. Your body doesn’t have a central location where glucose is burned for energy, like a roaring fireplace or the cylinders of a car’s engine. Instead, glucose is converted to energy on a microscopic level inside trillions and trillions of the individual cells that make up you. You can understand how this works by thinking about muscles. When you raise your fist toward your shoulder, your bicep muscle gets shorter; it contracts to bend your elbow and pull the lower arm upward. You can actually measure the difference in bicep muscle length, first with your arm extended straight out and again with your arm bent toward your shoulder. The contraction of your bicep muscle is actually the contraction in unison of millions of individual muscle cells that go together to make a bicep — the cells themselves contract. Movement requires energy, and each individual muscle cell is burning glucose to provide that energy. If you add a 20 pound dumbbell to your muscle movements it’s easy to feel the increasing energy requirement, the heat given off, and eventually the depletion of fuel as the muscle becomes exhausted. The real action to generate this energy takes place inside of individual cells. Cells come in all shapes and sizes, but most are way too small to see without a microscope. The different kinds of materials and structures that make a cell, including your DNA, are contained within what’s called a cell membrane. Cell membranes aren’t completely impermeable and can be influenced to let materials come into or leave the cell through the membrane. And if glucose is converted to energy inside of your cells, it’s apparent that glucose found its way into those cells somehow. Simplifying insulin Although not always the case, many important cell types including muscle cells won’t allow glucose to freely pass through the cell membrane without a mediator. That’s where insulin becomes so important. Insulin is a hormone produced by specialized cells in your pancreas calledbetacells or islet cells. Hormones are chemicals released from one location within a body that affect cells in other parts of the body. In the case of insulin and glucose, it’s insulin that signals individual cells to allow glucose passage through the cell membrane. This process is often illustrated with insulin as a key unlocking a door that glucose can use to enter the cell, and in many ways this picture is accurate. Both glucose and insulin circulate in your blood to deliver fuel to almost every cell that requires energy to perform its duty. The main issue here, to define diabetes, is to understand that if the marvelous and precise ability of insulin to convince cells to open the door and take glucose inside is lost or diminished, glucose remains in the bloodstream. This means cells needing, or at least greatly preferring, glucose for energy don’t have any. This also means glucose levels in your blood remain higher than normal, even as your kidneys slowly try to remove the excess. This abnormal state is hyperglycemia, and if this abnormal state becomes your “normal” state, then you have diabetes. People who know someone with diabetes may associate low blood glucose, hypoglycemia, as a symptom of diabetes. Hypoglycemia deprives the brain of adequate energy, so the signs of low blood glucose are obvious, mimicking alcohol intoxication and leading to unconsciousness. However, hypoglycemia is a result of diabetes treatment, with injected insulin or other medications that stimulate natural production of insulin from islet cells, not diabetes. It’s high blood glucose levels, hyperglycemia, that defines diabetes, and this condition can be unnoticeable.