TYPE 2 DIABETES

Type 2 diabetes (formerly called adult-onset diabetes or non-insulin-dependent diabetes mellitus) is the most common type of diabetes. If you have type 2 dia­betes, you are insulin resistant, which means you need more insulin to lower your blood glucose levels. You also have some beta cell loss in your pancreas, but not to the same extent as in type 1 diabetes. Most of the people with this kind of diabetes are overweight or obese.

Type 2 diabetes is the most common form of diabetes in the world. In the past, it occurred mostly in middle-aged and older individuals, but nowadays it is often seen in younger people, includ­ing children and teenagers. There are more new cases of type 2 diabetes than ever before, and there are many reasons for this:

• Obesity increases the risk for diabetes, and there has been a dramatic increase in the prevalence of obesity (number of people who are obese). The increase in the rate of diabetes parallels the increase in the rate of obesity.
• Diabetes occurs more frequently in older individuals, and the population is aging.
• Ethnic minorities, especially African-Americans, Hispanics, and Asian-Americans, have a higher risk of type 2 diabetes
• There is a heightened awareness of diabetes because it has been widely reported in the media in recent years, and so people may be diagnosed earlier than before.
• Recent changes in the way diabetes is diagnosed (measuring fasting glucose rather than doing a two-hour oral glucose tolerance test) have also made it easier to diagnose diabetes.

CAUSES OF TYPE 2 DIABETES

People get type 2 diabetes because

• They are insulin resistant—that is, compared to an insulin sensitive person, more insulin is needed to have the same effect.
• They have lost beta cells so that they are not able to make enough insulin for the body’s needs.

  Genetic and environmental factors combine to cause both the insulin resistance and the beta cell loss.

Type 2 Diabetes and Genes  

The evidence that genes are important comes from the following observations:

• Some ethnic groups are at very high risk for developing diabetes. For example, over 50 percent of the adult Pima Indians living in Arizona have diabetes. People with Caucasian ancestry generally have a lower risk for type 2 diabetes. The risk of diabetes is less in those Pima Indians who also have some European ancestry.
• Type 2 diabetes runs in families. If one parent has type 2 diabetes, the risk that his or her child will develop diabetes in the future is 40 percent, and the risk increases to 70 percent if both parents have diabetes. Also, if you compare identical to nonidentical twins, the risk of a second twin getting diabetes is higher if they are identical.
• Sequencing of the human genome has allowed researchers to look for genes that increase the risk of developing type 2 diabetes. Recently, studies of families where multiple members have type 2 diabetes have identified ten regions of the human genome where genetic alterations increase the risk for type 2 diabetes. Interestingly, some of the genetic alterations are in genes that regulate the development or func­tion of the insulin-producing beta cells.

Type 2 Diabetes and Environment

Even though you may have the genetic susceptibility to develop type 2 diabetes, whether you actually get the disease greatly depends on your diet and physical activity. The most important environmental factor for type 2 diabetes is obesity, because having more fat causes insulin resistance. However, not all fat is the same as far as insulin resistance is concerned—fat that is inside the abdomen (visceral fat) is particularly problematic. Women with a waist circumference greater than thirty-five inches (88 cm) and men with a waist circumference greater than forty inches (102 cm) are more likely to have visceral fat and be insulin resistant.  People with more visceral fat have higher fatty acid levels in their blood, and this may be important in the development of insulin resistance

The beta cell injury in type 2 diabetes starts several years before the development of diabetes. The factors that cause the beta cell injury are not well understood. Visceral fat again may be important, releasing chemical fac­tors that are harmful to the beta cells. Early in the disease process, there are still sufficient beta cells to keep the glucose levels normal. However, in conditions where there is additional need for insulin, the beta cells may not be able to respond ade­quately and diabetes can develop:

• Gaining weight and not exercising are by far the most common reasons for needing additional insulin.
• Pregnancy increases the need for insulin, and that is why some women get gestational diabetes. After delivery, the insulin needs decline and the diabetes resolves. However, the underlying problem of the injured beta cells does not resolve after delivery, and may even get worse. This means that in future pregnancies the woman will definitely develop diabetes, and may do so even earlier in the pregnancy. Eventually, the beta cell failure progresses so much that even without the additional stress of pregnancy, the glucose levels are elevated and the woman is diagnosed with type 2 diabetes.
• Certain medicines increase insulin needs. For example, steroids (such as prednisone) increase insulin resistance, and when given in large doses for an inflammatory condition such as asthma or rheumatoid arthritis, can  cause diabetes in a person with injured beta cells. Usually the diabetes resolves once the steroids are discontinued. Niacin, a drug used to lower triglyceride levels in the blood, when given in very large doses, can also cause insulin resistance, and if a person is susceptible, he or she will get prediabetes or even diabetes. The medicines given after an organ transplant can affect both beta cell function and insulin resistance, and almost 20 percent of people who are taking medicines to prevent  rejection of a transplant can develop diabetes. Diabetes may resolve once the transplant medicines are adjusted, and the transplant patient should not stop the immunosuppressant medicines just because of the diabetes.

TREATMENT OF TYPE 2 DIABETES

If you are diagnosed with type 2 diabetes, you will be treated for two problems: insulin resistance and impaired insulin release.

The most important thing your doctor will ask you to do, even before prescribing any medicines, is to lose weight by exercising and reducing the calories in your diet. These two things will reduce the insulin resistance significantly. We know that weight loss really works, because when obese patients undergo gastric bypass sur­gery and reduce the total number of calories they eat, a lot of them (up to 80 percent of patients in some clinical studies) are able to stop their diabetes medicines and their glucose levels became normal.

Your doctor will prescribe medicines if exercise and dietary changes do not con­trol your glucose levels. The medicines work in a variety of ways:

• They slow down glucose absorption from the gut.
• They reduce glucose production from the liver.
• They stimulate insulin release from the remaining beta cells.
• They make the body more responsive to the circulating insulin (decrease insulin resistance).
• They slow stomach emptying and suppress your appetite.

  More than one medicine may be necessary to get your glucose levels in the target range. If the oral medicines are not able to adequately control the glucose levels, you are unable to tolerate the side effects, or you have other medical conditions that prevent you taking them, then your doctor will start you on insulin.

During your clinic visit, your doctor will also take into consideration other health issues that are common in people with type 2 diabetes such as high blood pressure and cholesterol problems. If any of these conditions are present, your doctor may give you prescriptions to treat them, as well.