PPAR agonists for the treatment of cardiovascular disease in patients with diabetes

Diabetes is a complex disease defined by hyperglycaemia; however, strong associations with abdominal obesity, hypertension and dyslipidaemia contribute to the high risk of cardiovascular disease. Although aggressive glycaemic control reduces microvascular complications, the evidence for macrovascular complications is less certain. The theoretical benefits of the mode of action of peroxisome proliferator-activated receptor (PPAR) agonists are clear. In clinical practice, PPAR-α agonists such as fibrates improve dyslipidaemia, while PPAR-γ agonists such as thiazolidinediones improve insulin resistance and diabetes control. However, although these agents are traditionally classed according to their target, they have different and sometimes conflicting clinical benefit and adverse event profiles. It is speculated that this is because of differing properties and specificities for the PPAR receptors (each of which targets specific genes). This is most obvious in the impact on cardiovascular outcomes--in clinical trials pioglitazone appeared to reduce cardiovascular events, whereas rosiglitazone potentially increased the risk of myocardial infarction. The development of a dual PPAR-α/γ agonist may prove beneficial in effectively managing glycaemic control and improving dyslipidaemia in patients with type 2 diabetes. Yet, development of agents such as muraglitazar and tesaglitazar has been hindered by various serious adverse events. Aleglitazar, a balanced dual PPAR-α/γ agonist, is currently the most advanced in clinical development and has shown promising results in phase II clinical trials with beneficial effects on glucose and lipid variables. A phase III study, ALECARDIO, is ongoing and will establish whether improvements in laboratory test profiles translate into an improvement in cardiovascular outcomes.