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Carbohydrates and carbohydrate metabolism
- Diabetes is a group of metabolic disease characterized by a high blood glucose level (hyperglycaemia). In the short term it leads to ketoacidosis. If left untreated it leads to long-term complications including damage to the retina of the eye, nerve damage and kidney damage. There are two main types of diabetes called type 1 and type 2. Type 1 is where there is an insulin deficiency or production is impaired. Type 2 is where there may be only partial secretion of insulin or the cells are insulin resistant. There is also a third type of diabetes called gestational diabetes that is brought about by pregnancy. This type of diabetes is due to insufficient secretion of insulin.
- Ketone bodies are formed when carbohydrate intake is low and the body uses fat as an energy source. The acetyl-CoA from fatty acid catabolism normally enters the citric acid cycle as long as there is a balanced intake of fat and carbohydrate. This means that there will be sufficient oxaloacetate from carbohydrates to combine with the acetyl-CoA. However, in diabetic patients, the oxaloacetate is used up to produce glucose by the gluconeogenic pathway. The acetyl-CoA cannot then enter the citric acid cycle as there is no oxaloacetate and instead forms keto-acids (known as ketone bodies) including acetoacetate and D-3-hydroxybutyrate which are excreted through the urine (ketonuria).
- In unmanaged diabetic patients, glucose levels in the blood are high, but cells do not absorb it, which means they are starved. The body increase fat and protein breakdown to compensate. By-products of this are keto-acids. These enter the bloodstream and cause the blood to become acidic. This disrupts the homeostasis of electrolytes in the body (potassium is excreted in the urine) and this can have serious effects. There are various symptoms that develop as a consequence of excessive ketones in the blood, including; dehydration, dry skin, fruity smelling breath, vomiting, arrhythmia, fatigue and in severe cases it may lead to a coma.