Diabetes mellitus is a condition wherein blood glucose levels increase due to abnormalities in insulin-mediated regulation. Type 1 diabetes mellitus is a condition of insulin deficiency caused by destruction of the insulin-producing pancreas cells. Type 2 diabetes mellitus is a metabolic disorder characterized by cellular insensitivity to insulin. Various diabetes medications achieve reductions in blood glucose levels through different mechanisms. Treatment of type 2 diabetes often involves two or more medications with different effects on the body.
Increased Cellular Glucose Absorption
Man-made insulins serve as replacement therapy for people with an insulin deficiency, including those with type 1 diabetes and a small subset of type 2 diabetics who have declining insulin production. The effects of prescription insulins mirror those of the naturally occurring hormone.
Most body tissues require insulin to absorb glucose, explains Colorado State University's electronic text, "Pathophysiology of the Endocrine System." When insulin binds to a cell, a reaction occurs that opens the cell "doors," permitting glucose entry. As such, insulin is the key that unlocks cells' glucose entry doors. By promoting the movement of glucose from the blood into the body tissues, insulin lowers the circulating blood glucose level.
Increased Insulin Secretion
Type 2 diabetics typically have normal pancreatic insulin-producing cells, but resistance to the effects of insulin in the tissues leads to elevated blood sugar. To overcome insulin resistance, some type 2 diabetes medications stimulate increased insulin secretion from the pancreas. Drugs that provoke this effect include the sulfonylureas and the meglitinides. The sulfonylureas include glyburide, glipizide, glimepiride, chlorpropamide, tolbutamide and tolazamide. Repaglinide and nateglinide are meglitinides.
Reduced Liver Glucose Production
The type 2 diabetes medication metformin decreases blood glucose primarily by inhibiting liver glucose production, report Joseph Evans, Ph.D., and Dr. Robert Rushakoff in the electronic medical reference "Endotext." Notably, prescription insulins for type 1 diabetes also inhibit liver glucose production. Decreased liver glucose production typically leads to a lower blood glucose level, especially between meals.
Improved Insulin Sensitivity
Type 2 diabetes medications known as thiazolidinediones, including pioglitazone and rosiglitazone, improve insulin sensitivity in fatty tissues and other cell types, report Evans and Rushakoff in "Endotext." Improved insulin sensitivity overcomes the primary metabolic defect of type 2 diabetes, insulin resistance.
Decreased Carbohydrate Digestion and Absorption
Alpha-glucosidase inhibitors, including miglitol and acarbose, partially block the digestion of complex carbohydrates in the intestine. Breads, pasta, potatoes, cereals, beans and rice are rich in complex carbohydrates. Normal breakdown of complex carbohydrates in the intestine yields glucose, which is absorbed into the bloodstream. By partially blocking the breakdown of complex carbohydrates, the amount of glucose absorbed from the diet decreases with a parallel fall in blood sugar levels, explains the National Institute of Diabetes and Digestive and Kidney Diseases.
References
- Colorado State University, Pathophysiology of the Endocrine System: Physiologic Effects of Insulin
- Drugs.com: Insulin
- American Diabetes Association: Insulin Basics
- Endotext.com: Oral Pharmacological Agents for Type 2 Diabetes: Sulfonylureas, Meglitinides, Metformin, Thiazolidinediones, A-Glucosidase Inhibitors, and Emerging Approaches
- National Institute of Diabetes and Digestive and Kidney Diseases: Sulfonylurea
