Diabetes is a disease of disordered carbohydrate metabolism. Whether you are a type 1 or type 2 diabetic, your ability to process carbohydrates normally is impaired. Type 1 diabetes is a state of insulin deficit, while type 2 diabetes is predominantly a state of insulin resistance. Both conditions lead to elevated blood glucose levels, which causes inappropriate physiological responses in your cells. When diabetes is treated, carbohydrate metabolism normalizes to a certain degree.
Cellular Switches
Although all of your cells possess the ability to process glucose, your liver is your body's primary site of carbohydrate metabolism. Your liver's cells contain an array of enzymes that can convert glucose to fat or glycogen for storage, and another set of enzymes to break down fats and glycogen to release fatty acids and glucose. The opposing processes are controlled by molecules called "transcription factors," which are the "switches" that turn on -- or turn off -- the enzymatic machinery that determines which metabolic process is working at any given time.
Fed State
When you eat a meal containing carbs, they are broken down into simple sugars, such as glucose, which are absorbed into your bloodstream. In healthy people, rising blood glucose levels stimulate the release of insulin from the pancreas. Insulin and glucose then trigger the cellular switches in your liver that convert glucose to glycogen first, then to fat if you have consumed more carbs than your body needs. In diabetics, the absence or a shortage of insulin -- or insulin resistance -- tends to push your cellular machinery into a predominantly "fat-storage" mode.
Fasting State
In healthy fasting people, falling blood glucose levels trigger switches in liver cells that stimulate the breakdown of glycogen to produce glucose, which then enters the bloodstream and travels to other organs and tissues that use the glucose for energy. An August 2008 "Endocrine Journal" review suggests that the intracellular switches in diabetics are not appropriately triggered in response to changing glucose levels, which leads to an imbalance in glucose and fat metabolism.
Considerations
Diabetes interferes with normal carb metabolism due to imbalances in your cells' enzymatic machinery. A lack of insulin or a state of insulin resistance leads to the triggering of cellular transcription factors that route carbs into fat-storage pathways, rather than glycogen-storage pathways. This further increases your cells' resistance to insulin, which creates a cycle of amplified insulin resistance and fat storage.
References
- "Biochemical Journal"; "New Perspectives in the Regulation of Hepatic Glycolytic and Lipogenic Genes by Insulin and Glucose: A Role for the Transcription Factor Sterol Regulatory Element Binding Protein-1c"; F. Foufelle et al; September 2002
- "Endocrine Journal"; "ChREBP: A Glucose-Activated Transcription Factor Involved in the Development of the Metabolic Syndrome"; K. IIzuka and Y. Horikawa; August 2008
