Diabetes mellitus is a syndrome caused by either lack of insulin secretion or decreased sensitivity to insulin. There are two main types: type 1 diabetes results from lack of insulin secretion due to destruction of pancreatic beta cells, while type 2 diabetes initially stems from reduced tissue sensitivity to insulin. For both types, metabolism of carbohydrates, fats, and proteins is impaired, leading to high blood glucose as cells cannot efficiently use glucose for energy.

2. Diabetes Mellitus
Diabetes mellitus is a syndrome of impaired carbohydrate,
fat, and protein metabolism caused by either lack of insulin
secretion or decreased sensitivity of the tissues to insulin.
There are two general types of diabetes mellitus:
1. Type 1 diabetes, also called insulin-dependent Diabetes mellitus, is caused
by lack of insulin secretion
2. Type 2 diabetes, also called non–insulin-dependent Diabetes mellitus, is
initially caused by decreased sensitivity of target tissues to the metabolic
effect of insulin. This reduced sensitivity to insulin is often called insulin
resistance.

3. In both types of diabetes mellitus, metabolism of all the
main foodstuffs is altered. The basic effect of insulin
deficiency
or insulin resistance on glucose metabolism is to
prevent efficient uptake and utilization of glucose by most
cells of the body, except those of the brain. As a result,
blood glucose concentration increases, cell utilization of
glucose falls increasingly lower, and utilization of fats and
proteins increases.

4. Type 1 Diabetes—Deficiency of Insulin Production by
Beta Cells of the Pancreas
Injury to the beta cells of the pancreas or diseases that impair
insulin production can lead to type 1 diabetes. Viral
infections or autoimmune disorders may be involved in the
destruction of beta cells in many patients with type 1
diabetes,
although heredity also plays a major role in determining
the susceptibility of the beta cells to destruction by
these insults. In some cases, persons may have a hereditary
tendency for beta cell degeneration even without viral
infections or autoimmune disorders.

5. However, type 1 diabetes
can occur at any age, including adulthood, following
disorders that lead to the destruction of pancreatic beta
cells. Type 1 diabetes may develop abruptly, over a period
of a few days or weeks, with three principal sequelae:
(1) increased blood glucose levels,
(2) increased utilization of fats for energy and for formation of
cholesterol by the liver
(3) depletion of the body’s proteins.
Approximately 5% to 10% of people with diabetes mellitus have
the type form of the disease.