Type 2 Diabetes

Diabetes mellitus type 2 or Type 2 Diabetes (formerly called non-insulin-dependent diabetes (NIDDM), obesity-related diabetes, or adult-onset diabetes) is a metabolic disorder that is primarily characterized by insulin resistance, relative insulin deficiency and hyperglycemia. It is often managed by engaging in exercise and modifying one's diet. It is rapidly increasing in the developed world, and there is some evidence that this pattern will be followed in much of the rest of the world in coming years. The CDC has characterized the increase as an epidemic.^[1] In addition, whereas this disease used to be seen primarily in adults over age 45, in contrast to Diabetes mellitus type 1, it is now increasingly seen in children and adolescents, an increase thought to be linked to rising rates of obesity in this age group. ^[2]

Unlike Type 1 diabetes, there is little tendency toward ketoacidosis in Type 2 diabetes, though it is not unknown. One effect that can occur is nonketonic hyperglycemia which also quite dangerous, though it must be treated very differently. Complex and multifactorial metabolic changes very often lead to damage and function impairment of many organs, most importantly the cardiovascular system in both types. This leads to substantially increased morbidity and mortality in both Type 1 and Type 2 patients, but the two have quite different origins and treatments despite the similarity in complications.

Pathophysiology

Insulin resistance means that body cells do not respond appropriately when insulin is present.

Other important contributing factors:

• increased hepatic glucose production (e.g., from glycogen degradation), especially at inappropriate times
• decreased insulin-mediated glucose transport in (primarily) muscle and adipose tissues (receptor and post-receptor defects)
• impaired beta-cell function—loss of early phase of insulin release in response to hyperglycemic stimuli
• Cancer survivors who received allogenic Hematopoietic Cell Transplantation (HCT) are 3.65 times more likely to report type 2 diabetes than their siblings. Total body irradiation (TBI) is also associated with a higher risk of developing diabetes.

Type 2 may go unnoticed for years in a patient before diagnosis, since the symptoms are typically milder (no ketoacidosis) and can be sporadic. However, severe complications can result from improperly managed Type 2 diabetes, including renal failure, blindness, wounds that are slow to heal (including surgical incision), and arterial disease, including coronary artery disease. The onset of Type 2 is most common in middle age and later life, though a form of it, called MODY is being much more frequently seen in adolescents.

Diabetes mellitus type 2 is presently of unknown etiology (i.e., origin). Diabetes mellitus with a known etiology, such as secondary to other diseases, known gene defects, trauma or surgery, or the effects of drugs, is more appropriately called secondary diabetes mellitus. Examples include diabetes mellitus caused by hemochromatosis, pancreatic insufficiencies, or certain types of medications (e.g. long-term steroid use).

About 90–95% of all North American cases of diabetes are type 2^[3], and about 20% of the population over the age of 65 has diabetes mellitus type 2. The fraction of type 2 diabetics in other parts of the world varies substantially, almost certainly for environmental and lifestyle reasons, though these are not known in detail. Diabetes affects over 150 million people worldwide and this number is expected to double by 2025^[3]. There is also a strong inheritable genetic connection in type 2 diabetes: having relatives (especially first degree) with type 2 increases risks of developing type 2 diabetes very substantially. In addition there is also a mutation to the Islet Amyloid Polypeptide gene that results in an earlier onset, more severe, form of diabetes^[4],[5]. About 55 percent of type 2 are obese^[6] —chronic obesity leads to increased insulin resistance that can develop into diabetes, most likely because adipose tissue is a (recently identified) source of several chemical signals to other tissues (hormones and cytokines). Other research shows that type 2 diabetes causes obesity.^[7]

Diabetes mellitus type 2 is often associated with obesity, hypertension, elevated cholesterol (combined hyperlipidemia), and with the condition often termed Metabolic syndrome (it is also known as Syndrome X, Reavan's syndrome, or CHAOS). It is also associated with acromegaly, Cushing's syndrome and a number of other endocrinological disorders. Additional factors found to increase risk of type 2 diabetes include aging^[8], high-fat diets^[9] and a less active lifestyle^[10].

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