Mechanism of Action of Oral Hypoglycemic Agents in Type 2 Diabetes

Primary Mechanisms by Drug Class

The American Diabetes Association notes that oral hypoglycemic agents work through five distinct mechanisms to lower blood glucose in type 2 diabetes, targeting different pathophysiologic defects including insulin resistance, impaired insulin secretion, and excessive hepatic glucose production 1
Metformin improves insulin sensitivity primarily in the liver and muscle tissue without directly affecting β-cell function, according to the American Association of Clinical Endocrinologists 2
Thiazolidinediones improve peripheral insulin sensitivity by acting as insulin sensitizers in muscle and adipose tissue, as recommended by the American Diabetes Association 1, 2
Alpha-glucosidase inhibitors slow the hydrolysis of complex carbohydrates in the small intestine, thereby slowing carbohydrate absorption, as noted by the American Diabetes Association 2

The American Diabetes Association states that type 2 diabetes results from defects in both insulin secretion and insulin action, requiring agents that target different mechanisms, with elevated basal hepatic glucose production in the presence of hyperinsulinemia being the primary cause of fasting hyperglycemia 1
The UKPDS demonstrated that improved glycemic control, irrespective of the agent used, decreased microvascular complications by 25%, as reported by the National Institute of Diabetes and Digestive and Kidney Diseases 3

In advanced chronic kidney disease, decreased insulin clearance and reduced gluconeogenesis by the kidney alter the effectiveness and safety profile of oral hypoglycemic agents, according to the National Kidney Foundation 4, 5
Patients with ESKD experience decreased insulin degradation by kidney, liver, and muscle due to uremia, leading to reduced requirements for exogenous insulin and oral agents, as noted by the American Society of Nephrology 4, 5

Sodium-glucose cotransporter-2 (SGLT-2) inhibitors prevent renal glucose reabsorption and increase glycosuria, representing a novel insulin-independent mechanism for glucose lowering, according to the American Diabetes Association 6
SGLT-2 inhibitors work through the kidneys rather than targeting insulin resistance or secretion directly, as stated by the American College of Physicians 7, 8

Metformin is recommended as first-line treatment because it addresses the primary defect of excessive hepatic glucose production without causing hypoglycemia, as recommended by the American College of Physicians 7, 9, 10, 11
When a second oral therapy is needed, clinicians should consider adding either a sulfonylurea, thiazolidinedione, SGLT-2 inhibitor, or DPP-4 inhibitor to metformin based on complementary mechanisms of action, according to the American Association of Clinical Endocrinologists 7, 8, 9, 10, 11