In a recent issue of Diabetes Care, Pershadsingh and Kurtz (1) reported an interesting case subject with impaired glucose tolerance, whose insulin resistance and triglycerides improved on the angiotensin II type 1 receptor blocker telmisartan. Telmisartan has a unique agonist activity of the peroxisome proliferator–activated receptor γ (PPARγ) in vitro (2). It reduces glucose, insulin, and triglyceride levels in rats fed a high-fat, high-carbohydrate diet (2). These results suggest that telmisartan may have a beneficial effect on glycemic control in type 2 diabetes.
We investigated the effect of telmisartan or candesartan on glycemic control in 38 Japanese patients with type 2 diabetes and hypertension (22 men and 16 women, mean age 67.0 ± 9.11 years [means ± SD]). Two different doses of telmisartan (20 and 40 mg/day) were given in 20 subjects (n = 9 and n = 11, respectively), and candesartan (8 mg/day) was given in 18 subjects. HbA1c levels were measured before and 3 months after administration. In the 40-mg telmisartan group, HbA1c was significantly decreased after 3 months (from 8.12 ± 0.97 to 7.43 ± 0.79%, P < 0.05, paired t test), whereas no significant change in HbA1c was found in the 20-mg telmisartan group or the control group (7.49 ± 0.70 to 7.45 ± 0.75% and 7.40 ± 1.38 to 7.32 ± 1.28%, respectively).
Since this study was limited by the fact that it was not a randomized study and that it included only a small number of patients, the effect of confounding factors could not be excluded. Therapy was changed during the observation period in some cases (insulin doses were increased up to 2 units in one case or decreased up to 2 units in three cases, whereas no change was made in oral medications), but no apparent correlation could be found between the changes in insulin dose and those in glycemic control. Despite these limitations, this preliminary result is in line with the hypothesis that telmisartan has an insulin-sensitizing ef-fect through PPARγ activation (1). However, our result is not compatible with another report (3) on type 2 diabetes, in which no change in HbA1c was observed after administration of 40 mg telmisartan. The baseline HbA1c level was low in that report (6.45%) compared with our study. In our study, there were considerable variations in HbA1c changes after telmisartan, similar to those after thiazolidnedione ligands of PPARγ, and the patients with lower HbA1c showed a smaller decrease after telmisartan than those with a higher HbA1c. A randomized control study with a larger number of subjects may be justified to test whether telmisartan may improve glycemic control in type 2 diabetes.
