Diabetes is a condition in which the hormone insulin cannot communicate to the cells when glucose, or blood sugar, is present in the bloodstream. When it goes untreated, diabetes leads to elevated blood glucose levels. It also can lead to an inhibition of enzymes needed to convert lactate, a derivative from glucose metabolism, into energy.
Diabetes
The two main types of diabetes are Type 1 and Type 2 diabetes. Type 1 diabetes is an autoimmune disease in which the immune system attacks the pancreas. This results in a significant reduction in insulin synthesis. Type 2 diabetes occurs when insulin receptors shut down. They can shut down for a variety of reasons, one being a heavy intake of carbohydrates, such as sugar, bread, pasta and rice, over a long time period. Both Type 1 and Type 2 diabetes prevent cells from absorbing glucose from the bloodstream.
Glucose
Cells can normally get energy from other sources than glucose, including fat and amino acids. Furthermore, Type 2 diabetes does not affect all cells at once. There is a gradual shut down of insulin receptors. However, those cells that can absorb glucose are facing a further obstacle. Diabetes can inhibit pyruvate dehydrogenase, an enzyme in the pathway that turns glucose into energy.
Pyruvate to Lactate
When glucose converts into energy, it first turns into pyruvate. Pyruvate converts to the molecule acetyl-CoA, and acetyl-CoA then enters the Krebs cycle, which turns acetyl-CoA into carbon dioxide, water and useable energy. It is the step that turns pyruvate into acetyl-CoA that requires pyruvate dehydrogenase. When pyruvate cannot convert into acetyl-CoA, it converts into lactate, or lactic acid.
Lactate Metabolism
Lactate derives from pyruvate when there is a shortage of oxygen, such as during exercise. When more oxygen becomes available, lactate can convert back into pyruvate, which can then turn into energy. As lactate must turn into pyruvate before it can turn into energy, pyruvate dehydrogenase also is essential to the metabolism of lactate. When pyruvate dehydrogenase is inhibited, lactate accumulates in the muscle cells or enters the blood.
Lactate and Diabetes
As diabetes can inhibit pyruvate dehydrogenase, which is required to metabolize lactate, diabetics often have elevated levels of blood lactate. A population-based study published in the December 2010 issue of “International Journal of Epidemiology” confirms that Type 2 diabetes is strongly associated with an increased concentration of blood lactate across the population of older adults. This condition, which also is known as lactic acidosis, can be fatal. Less severe cases of lactic acidosis can lead to nausea, vomiting, mental confusion, hyperventilation and an altered state of consciousness.
References
- American Diabetes Association: Diabetes Basics
- Ämerican Journal of Physiology"; Endocrinology and Metabolism; Dysregulated Pyruvate Dehydrogenase Complex in Zucker Diabetic Fatty Rats; C.M. Schummer, et al.; October 2007
- University of California, San Diego: Muscle Physiology
- University of Connecticut: Lactic Acidosis
- “International Journal of Epidemiology”; Association of Blood Lactate With Type 2 Diabetes: The Atherosclerosis Risk in Communities Carotid MRI Study; S.O. Crawford, et al.; December 2010
