|Understanding Diabetes: Part 1 of a Three-Part Series|
|Thursday, September 12, 2013|
In 2011, nearly 26 million people in the United States were affected by diabetes – and two-thirds of those people were unaware of their disease. In an effort to increase awareness of this chronic health condition, my next three months’ health articles will focus on diabetes: the disease itself; treatment options; and recommended screenings and interventions.
The two most common forms of diabetes are Type 1 diabetes mellitus and Type 2diabetes mellitus. In the U.S., most adult diabetics - about 90% of the diabetic population – are diagnosed with Type 2. For the purposes of these articles, we will concentrate on the more common entity: Type 2 diabetes.
So what is diabetes? Diabetes mellitus, as it is more formally known, is a disease in which the body becomes unable to properly respond to dietary sugar. In a non-diabetic, sugar intake triggers responses from a number of different body systems to help properly digest sugar. These responses are directed by insulin and other chemicals secreted by gastrointestinal organs. Chronically elevated levels of glucose, as seen in diabetes, result in decreased responsiveness to regulatory chemicals. You may be surprised to learn that many organs participate in glucose (sugar) breakdown and use: these include the pancreas, kidneys, liver, brain, gastrointestinal tract, fat cells and muscle cells.
The pancreas has two types of cells that control blood sugar -- they are referred to as alpha and beta cells. Alpha cells respond to low blood sugar levels by secreting a chemical that causes the liver to release stored glucose to prevent blood sugar from dropping too low. Beta cells secrete insulin in response to elevated blood glucose levels; insulin directs the body to take up and store the glucose in muscle and fat cells.
The kidneys function as the body’s filters for liquid waste products. In patients with normal blood sugar levels, almost all of the glucose filtered through the kidneys is reabsorbed into the blood stream. However, as blood sugar levels rise in diabetes, the kidney reaches a limit past which it is unable to reabsorb glucose; all additional sugar exits through the body’s urine. It is at this point that patients may notice increased urination, increased thirst, and even weight loss.
The liver functions to store glucose in times of high blood sugar levels (such as after a meal), and release stored glucose in times of lower blood sugar levels. Whether the liver stores or produces glucose is largely determined by insulin released by the pancreas. In diabetes, the liver becomes unable to respond to insulin signals, causing it to release glucose even when blood sugar levels are elevated.
Our brains respond to blood sugar levels by emitting signals to control food intake, energy expenditure, and glucose balance. It is thought that insulin acts in the brain to suppress appetite, so in times of increased blood sugar (and thus increased insulin levels), our brains should signal us to stop eating. In obese persons with chronically elevated insulin levels, appetite suppression may be impaired due to failure of this signaling mechanism.
Muscle cells and fat cells each play important roles in taking up glucose to remove it from the blood stream. Again, insulin plays a key role in telling these cells when to do their job. In obese patients with diabetes, the cells become resistant to insulin signals and thus are less able to take up sugar. This contributes to the increased blood glucose levels of diabetes.
Finally, the gastrointestinal tract plays a significant role in regulating blood glucose levels. Through hormonal signaling, the cells of the intestines increase insulin secretion in response to elevated levels of glucose; they also block the secretion of stored sugar from the liver.
As you can see, diabetes is a very complex illness that causes dysfunction in a number of organ systems. Next month, I will discuss some of the interventions used to treat diabetes and how they repair some of these dysfunctions.