The study by Goldberg et al. (1) in the July issue of Diabetes Care concluded that, compared with rosiglitazone, pioglitazone was associated with improvements in triglycerides, HDL cholesterol, LDL concentration, and LDL particle size.
It should first be noted that 4,410 subjects were screened to obtain 735 eligible subjects. This was a highly selective group, and therefore this was an enriched study. Second, recognized goals for the diabetic patient were not reached with either pioglitazone or rosiglitazone for triglycerides, non-HDL cholesterol, and LDL cholesterol. Third, HDL particle size, which should have been available from the proton nuclear magnetic resonance spectroscopy of Liposcience, was not reported. Why was this omitted from both the American Heart Association presentation and the Diabetes Care study?
Finally, and most importantly, based on the Collaborative Atorvastatin Diabetes and Heart Protection Studies (2,3), it is now well recognized that irrespective of LDL levels, all type 2 diabetic patients benefit from statin therapy. Without concomitant statin therapy, these results have little clinical significance. This is especially important since two studies have clearly shown that when simvastatin or ezetimibe are coadministered with thiazolidinediones there are no significant differences in the lipid profile of those subjects on pioglitazone or rosiglitazone (4,5).
It is now clear for many studies that rosiglitazone does not decrease fasting triglycerides. However, two recent studies have shown that rosiglitazone does significantly decrease postprandial triglyceride levels. One study has shown that this is not the case with pioglitazone (8). While uncertainty surrounds the role of fasting triglycerides as a cardiac risk factor, there is little doubt that elevated postprandial triglycerides are a risk factor (9).
