Pioglitazone and rosiglitazone are insulin sensitizers belonging to the thiazolidinedione class of oral anti-diabetic medications. They directly target insulin resistance; a condition in which the body does not efficiently use the insulin it produces to control blood glucose levels. As an adjunct to diet and exercise, these agents are used as monotherapy to lower blood glucose levels and in combination therapy with insulin, sulfonylureas or metformin.

According to researcher Robert Spanheimer, MD, medical director for diabetes and metabolism, Takeda Pharmaceuticals North America, Lincolnshire, Illinois, United States, at least 2 core metabolic defects contribute to the development of type-2 diabetes -- relative insulin insufficiency and insulin resistance.

Insulin resistance is associated with a cluster of metabolic abnormalities, including dyslipidemia, which increases the risk for cardiovascular disease. The dyslipidemia associated with insulin resistance and type-2 diabetes is characterized by elevated TG levels and decreased HDL-C levels.

"Although low-density lipoprotein [LDL-C] levels may not be significantly elevated in patients with type-2 diabetes, we have observed an increase in the proportion of small, dense LDL-C atherogenic particles," Dr. Spanheimer said.

A total of 155 elderly patients were selected for the randomized, double-blind, parallel-group study. Patients had type-2 diabetes and fasting TG levels >/=150 mg/dL and <600 mg/dL. At randomization, patients taking antihyperglycemic medications discontinued use.

Patients began active therapy with pioglitazone 30 mg once daily, and increased to 45 mg once daily at 12 weeks. Treatment with rosiglitazone was initiated at 4 mg once daily, increasing to 4 mg twice daily at 12 weeks. Changes from baseline in TGs, HDL-C, LDL-C, LDL-C particle concentration, and LDL-C particle size were compared after 24 weeks between the two treatment groups using analysis of covariance with treatment group, region, and baseline value as covariates.

Dr. Spanheimer said patients receiving pioglitazone showed improvements from baseline compared with rosiglitazone in TG, HDL-C, as well as LCL-C particle concentration and size. A statistically mean difference in TG of 65.0 mg/dL was noted between the treatment groups at endpoint (P <.001).

Although both agents increased HDL-C, the increase achieved with pioglitazone was significantly greater, Dr. Spanheimer said.

"Furthermore, pioglitazone caused a shift from small, dense LDL-C particles to larger more buoyant LDL-C particles. This change in the size of the particles was accompanied by a decrease in particle concentration, an effect not observed with rosiglitazone," he added.


[Presentation title: Subanalysis of the Comparative Effects of Pioglitazone and Rosiglitazone on Markers of Diabetic Dyslipidemia in Elderly Patients With Type 2 Diabetes and Dyslipidemia. Abstract 277]

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