Thiazolidinediones--the new insulin enhancers

Insulin resistance, characterized by reduced responsiveness to normal circulating levels of insulin, leads to hyperglycemia and hyperinsulinemia resulting in a deadly quartet of non-insulin dependent diabetes mellitus, obesity, hypertension and dyslipidemia These complications, also referred to as 'Syndrome X' have been associated with an increased risk of coronary heart disease. A number of non-pharmacological and pharmacological interventions are available for prevention and treatment of insulin resistance. However, introduction of thiazolidinediones, the new orally active class of drug, has proved to be a major breakthrough in this field. These agents have been shown to reduce insulin resistance by a novel mechanism of action. By interacting with a family of nuclear receptors known as peroxisome proliferator activated receptors thiazolidinediones are thought to enhance the actions of insulin, thereby increasing insulin dependent glucose disposal and reducing hepatic glucose output. A series of animal and clinical studies in patients with impaired Glucose Tolerance and NIDDM have demonstrated the safety and effect of various thiazolidinediones including ciglitazone, pioglitazone and troglitazone. Thus, thiazolidinediones by unlocking insulin resistance act as a key to glycemic control and hence are likely to prove a useful and rational therapy in NIDDM and possibly other disorders resulting from insulin resistance.