Sulfonylurea effects on target tissues for insulin

Area of Science:

• Pharmacology
• Endocrinology
• Metabolic Diseases

Background:

• Sulfonylureas are commonly prescribed hypoglycemic agents.
• Their extrapancreatic actions are not fully understood.
• Insulin resistance is a hallmark of type II diabetes mellitus.

Purpose of the Study:

• To investigate the nonpancreatic effects of sulfonylureas on insulin responsiveness.
• To determine the impact of sulfonylureas on insulin target tissues: liver and fat.
• To elucidate the cellular mechanisms underlying sulfonylurea action.

Main Methods:

• In vivo administration of tolazamide and glipizide to rats.
• Measurement of postabsorptive serum glucose and insulin levels.
• In vitro culture of rat adipose tissue to assess insulin action and glucose transport.
• Analysis of hepatic insulin receptor number and affinity.
• Assessment of transglutaminase activity in hepatic tissue.

Main Results:

• In vivo sulfonylurea administration significantly reduced serum glucose levels without altering insulin levels.
• Sulfonylureas markedly potentiated insulin action in cultured fat cells, primarily augmenting insulin-stimulated glucose transport.
• No alterations in hepatic or adipose tissue insulin receptor number or affinity were observed.
• In vivo and in vitro treatments with sulfonylureas did not affect transglutaminase activity.

Conclusions:

• Sulfonylureas enhance insulin responsiveness in key target tissues (liver and fat).
• The primary mechanism involves potentiation of insulin-stimulated glucose transport in adipose tissue.
• These findings suggest sulfonylureas may act by correcting cellular defects contributing to insulin resistance in type II diabetes mellitus.