Type 2 diabetes is caused by either inadequate production of the hormone insulin or a lack of response to insulin by various cells of the body.
Normal regulation of blood sugar
Glucose is an important source of energy in the body. It is mainly obtained from carbohydrates in the diet which are broken down into glucose for the various cells of the body to utilize. The liver is also able to manufacture glucose from its glycogen stores.
In a healthy person, a rise in blood sugar after a meal triggers the pancreatic beta cells to release the hormone insulin. Insulin, in turn, stimulates cells to take up the glucose from the blood. When blood glucose levels fall, during exercise for example, insulin levels also decline.
As well as insulin stimulating the uptake of glucose from the blood by body cells, it also induces the:
Stimulates the conversion of glucose to pyruvate (glycolysis) to release free energy
Conversion of excess glucose to glycogen for storage in the liver (glycogenesis)
Uptake and synthesis of amino acids, proteins, and fat
Pathology of type 2 diabetes
In type 2 diabetes, the body either produces inadequate amounts of insulin to meet the demands of the body or insulin resistance has developed. Insulin resistance refers to when cells of the body such as the muscle, liver and fat cells fail to respond to insulin, even when levels are high. In fat cells, triglycerides are instead broken down to produce free fatty acids for energy; muscle cells are deprived of an energy source and liver cells fail to build up glycogen stores.
This also leads to an overall rise in the level of glucose in the blood. Glycogen stores become markedly reduced and there is less glucose available for release when it may be needed. Obesity and lack of physical activity are thought to be major causes of insulin resistance.