The main objective for treatments of diabetes is prevention of hyperglycemia and reduction of protein glycation to avert complications. The success of treatment is commonly monitored via Hb A1c levels. Furthermore, since diabetes may greatly increase risk for cardiovascular diseases, it is essential to control blood pressure and cholesterol levels as part of the treatment regimen. Here, we mainly discuss the pharmacological treatment options for managing blood glucose levels. The strategies discussed include altering specific functions in glucose homeostasis using small molecule drugs and/or including specific hormones and/or its analogs to enhance their levels and functions.
Treating type 1 diabetes: The treatment for type 1 diabetes is administration of insulin via injection or pump (see Insulin in Figure 1). Short-acting and long-acting insulins are typically used in combination. Long-acting insulins direct a basal level of sugar uptake by cells throughout the day, while short-acting insulins cover glucose level increases following meals.
Treating type 2 diabetes: There are various classes of non-insulin anti-diabetes medications that are used to treat type 2 diabetes. Here we discuss five main strategies for managing blood glucose levels (see Figure 1):
- Increasing insulin secretion may be accomplished by various classes of drugs. Some drugs increase release of insulin stored within the pancreatic β-cells, while other drugs promote insulin production and release.
- Increasing insulin function can enhance glucose uptake and utilization thereby facilitating lowering of blood glucose.
- Decreasing glucose production from liver stores of glycogen can reduce elevated blood glucose levels after overnight fasting.
- Decreasing glucose absorption from the food can be accomplished by blocking the breakdown of starch into glucose. Undigested starch is excreted in feces.
- Decreasing glucose reabsorption from the kidneys reduces blood glucose levels. Excess glucose is eliminated in urine.
Figure 1: Glucose homeostasis concept map showing strategies for treating type 2 Diabetes. The red arrows indicate how an individual would respond to high blood sugar. Processes targeted for treatment are colored and shaded - processes in green boxes (vertical line shading) are increased in treatment, while processes in red boxes (diagonal line shading) are decreased for treatment. Exogenous hormone analogs used for treatment are shown in bold italics and highlighted in yellow colored boxes.
How does the doctor decide which drug(s) to prescribe?
If the individual has type 1 diabetes, the only approved treatment is insulin administration.
Treatment plans for type 2 diabetes have various options and require careful decision. Immediately after a pre-diabetes diagnosis, the first line of action should be to make lifestyle changes to restrict calories, eat healthier, and exercise more to reduce weight and become active. If these measures fail to manage high blood glucose levels, the first drug commonly prescribed for treating type 2 diabetes is Metformin. The strategy here is to reduce glucose production by the liver and increase insulin sensitivity. If increasing dosage of this drug does not work (or if the individual has renal disease), Sulfonylureas (such as Glipizide) may be added to increase insulin secretion. Other classes of drugs (such as incretins or DPP4 inhibitors or Meglitinides) may also be used to achieve the same result - increased insulin secretion. When increased endogenous insulin fails to manage high blood glucose, the individual probably has severe insulin resistance, and drugs that increase insulin sensitivity (such as Thiazolidinediones) are often prescribed. At this stage, the doctor may also resort to alternative approaches to reducing the blood sugar load (e.g., alpha glucosidase inhibitors can reduce the amount of glucose absorbed from food or SGLT-2 inhibitors can reduce the reabsorption of glucose from kidneys so that the excess sugar is eliminated in urine). Finally, if all these approaches fail, the doctor may resort to adding insulin or completely switching to insulin for blood glucose management.
Ideally, diabetes treatment plans should be reviewed every 3-4 months to evaluate whether the prescribed drug(s) are adequate to manage the individual's diabetes. Many factors such as medication costs, access to medications, ability to tolerate the side-effects, and other medical conditions, may play critical roles in deciding the individual's treatment plans.
FDA-Approved Diabetes Medicines: www.fda.gov/ForPatients/Illness/Diabetes/ucm408682.htm