Diabetes

Type 2 diabetes is itself a group of disorders caused by some combination of insulin resistance—which occurs when cells' ability to respond to insulin is compromised—and insulin deficiency, which occurs when the beta cells' ability to make insulin is compromised. T2DM has, in the past, been called adult-onset diabetes, because most people with T2DM were adults. It was also called non-insulin-dependent diabetes mellitus (NIDDM), because people with type 2 diabetes usually do not require insulin injections. In the Unites States, T2DM is especially prevalent among certain ethnic minorities, including African Americans, Mexican Americans, Asian Americans, and Native Americans.

Obesity is a potent risk factor for T2DM. In the last thirty years, due to increased caloric intake and physical inactivity, both of which contribute to obesity, there was an explosion in the prevalence of T2DM, and it started occurring at younger ages—even in children. In addition to its association with an unhealthy lifestyle, T2DM is known to have a strong genetic component.

Scientists have been searching throughout the genome for T2DM-susceptibility genes. One such gene, calpain 10 protease, was identified on chromosome 2. A common variant of this gene may predispose certain individuals to T2DM; however, the true significance of this gene variant remains to be determined. In addition, several candidate genes have shown some evidence of being involved in T2DM. However, the effect of any single candidate gene variant on the risk of developing T2DM is modest. A candidate gene is a gene for which prior knowledge of its function leads researchers to assess whether chemical variation in it is associated with a disease.

As of 2002 there was no clinically available genetic test to predict the onset of type 2 diabetes, but it is anticipated that with a better understanding of the roles of various genes in T2DM, it will eventually be possible to use multiple genetic tests to identify individuals at risk for T2DM and to predict which treatments will be most helpful in specific patients. Although genetic susceptibility plays an important role in determining the risk of developing T2DM, studies have shown that the disease can often be prevented through diet, physical activity, and weight loss.