Diabetes Mellitus (Type 1 and Type 2)

What is diabetes?

Diabetes mellitus is a group of metabolic diseases characterized by high blood sugar (glucose) levels that result from defects in insulin secretion, its action, or both.

Normally, blood glucose levels are tightly controlled by insulin, a hormone produced by the pancreas. Insulin lowers the blood glucose level. When the blood glucose elevates (for example, after eating), insulin is released from the pancreas to normalize the glucose level by promoting the uptake of glucose into body cells. In patients with diabetes, the absence of insufficient production of or lack of response to insulin causes hyperglycemia. Diabetes is a chronic medical condition, meaning that although it can be controlled, it lasts a lifetime.

What is type 1 diabetes?

In autoimmune diseases, such as type 1 diabetes, the immune system mistakenly manufactures antibodies and inflammatory cells that are directed against and cause damage to patients' own body tissues. In persons with type 1 diabetes, the beta cells of the pancreas, which are responsible for insulin production, are attacked by the misdirected immune system. It is believed the tendency to develop abnormal antibodies in type 1 diabetes is, in part, genetically inherited, though the details are not fully understood.

Exposure to certain viral infections (such as mumps and Coxsackie viruses) or other environmental toxins may serve to trigger abnormal antibody responses that cause damage to the pancreas cells where insulin is made. Some of the antibodies seen in type 1 diabetes include anti-islet cell antibodies, anti-insulin antibodies, and anti-glutamic decarboxylase antibodies. These antibodies can be detected in the majority of patients and may help determine which individuals are at risk for developing type 1 diabetes.

At present, the American Diabetes Association does not recommend general screening of the population for type 1 diabetes, though screening of high-risk individuals, such as those with a first-degree relative (sibling, parent, child) with type 1 diabetes are encouraged. Type 1 diabetes tends to occur in young, lean individuals, usually before 30 years of age; however, older patients do present with this form of diabetes on occasion. This subgroup is referred to as latent autoimmune diabetes in adults (LADA). LADA is a slow, progressive form of type 1 diabetes. Of all the people with diabetes, only approximately 10% have type 1 diabetes and the remaining 90% have type 2 diabetes.

What is type 2 diabetes?

Type 2 diabetes was also previously referred to as non-insulin-dependent diabetes mellitus (NIDDM), or adult-onset diabetes mellitus (AODM). In type 2 diabetes, patients can still produce insulin but do so relatively inadequately for their body's needs, particularly in the face of insulin resistance as discussed above. In many cases, this actually means the pancreas produces larger than normal quantities of insulin. A major feature of type 2 diabetes is a lack of sensitivity to insulin by the cells of the body (particularly fat and muscle cells).

In addition to the problems with an increase in insulin resistance, the release of insulin by the pancreas may also be defective and suboptimal. There is a known steady decline in beta cell production of insulin in type 2 diabetes that contributes to worsening glucose control. (This is a major factor for many patients with type 2 diabetes who ultimately require insulin therapy.) Finally, the liver in these patients continues to produce glucose through a process called gluconeogenesis despite elevated glucose levels. The control of gluconeogenesis becomes compromised.

Type 2 diabetes occurs mostly in individuals over 30 years old and the incidence increases with age, but an alarming number of patients with type 2 diabetes are barely in their teen years. Most of these cases are a direct result of poor eating habits, higher body weight, and lack of exercise.

While there is a strong genetic component to developing this form of diabetes, there are other risk factors - the most significant of which is obesity. There is a direct relationship between the degree of obesity and the risk of developing type 2 diabetes, and this holds true in children as well as adults. It is estimated the chance to develop type 2 diabetes doubles for every 20% increase over desirable body weight. The U.S. Preventive Services Task Force (USPSTF) recommends screening for prediabetes and type 2 diabetes in adults aged 35 to 70 years who have overweight or obesity.

Regarding age, data shows that for each decade after 40 years of age regardless of weight there is an increase in the incidence of diabetes. The prevalence of diabetes in persons 65 years of age and older is around 29%. Type 2 diabetes is also more common in certain ethnic groups.

What causes diabetes?

Insufficient production of insulin (either absolutely or relative to the body's needs), production of defective insulin (uncommon), or the inability of cells to use insulin properly and efficiently leads to high blood sugar levels (hyperglycemia) and diabetes.

• This latter condition affects mostly the cells of muscle and fat tissues and results in a condition known as insulin resistance. This is the primary problem in type 2 diabetes.

• The absolute lack of insulin, usually secondary to a destructive process affecting the insulin-producing beta cells in the pancreas, is the main disorder in type 1 diabetes.

In type 2 diabetes, there also is a steady decline of beta cells that adds to the process of elevated blood sugars. Essentially, if someone is resistant to insulin, the body can, to some degree, increase the production of insulin and overcome the level of resistance. After a time, if production decreases and insulin cannot be released as vigorously, hyperglycemia develops.

What is glucose?

Glucose is a simple sugar found in food that is an essential nutrient that provides energy for the proper functioning of the body cells. Carbohydrates are broken down in the small intestine and the glucose in digested food is then absorbed by the intestinal cells into the bloodstream and is carried by the bloodstream to all the cells in the body where it is utilized. However, glucose cannot enter the cells alone and needs insulin to aid in its transport into the cells. Without insulin, the cells become starved of glucose energy despite the presence of abundant glucose in the bloodstream. The abundant, unutilized glucose is excreted in the urine.

What is insulin?

Insulin is a hormone produced by specialized cells (beta cells) of the pancreas, a deep-seated organ in the abdomen located behind the stomach. In addition to helping glucose enter the cells, insulin is also important in tightly regulating the level of glucose in the blood. After a meal, the blood glucose level rises. In response to the increased glucose level, the pancreas normally releases more insulin into the bloodstream to help glucose enter the cells and lower blood glucose levels after a meal. When the blood glucose levels are lowered, the insulin release from the pancreas is turned down. Even in the fasting state there is a low steady release of insulin than fluctuates a bit and helps to maintain a steady blood sugar level during fasting. In normal individuals, this regulatory system helps keep blood glucose levels in a tightly controlled range. But in patients with diabetes, insulin is either absent, insufficient for the body's needs, or not used properly by the body. All of these factors cause elevated levels of blood glucose (hyperglycemia).