Telmisartan and Losartan in Hypertensive IGT

Background: Both, ACE-inhibitors as well as angiotensin-II-type-1 (AT1) receptor antagonists seem to reduce the development of type-II diabetes in patients with hypertension and/or high vascular risk (1-3). The major drawback of that evidence is that it derives from post-hoc analyses in studies with rather poor metabolic phenotypisation of the populations included. Additionally, all that evidence is based on measurements of fasting plasma glucose.

In subjects with impaired glucose tolerance (IGT), insulin resistance and dysfunction of pancreatic beta-cells (in variable contribution) have already established increased postprandial hyperglycemia with a consecutively increased cardiovascular risk (4, 5). In addition they have a considerable risk for future development of manifest type-II diabetes in the range of 3-6 % within a year (6, 7). In such patients prevention of diabetes may also result in cardiovascular prevention. As subjects with IGT often exhibit a more or less pronounced metabolic syndrome, hypertension is a frequently found comorbidity and vice versa IGT is frequent in hypertensive patients suggesting a possible common soil of the two diseases (8).

Given these evidences, hypertensive subjects with IGT are a very suitable target population to study metabolic and vascular effects of an angiotensin-II-type-1-receptor antagonist.

Finally, it has to be acknowledged that insulin resistance needs to be seen in the context of the proinflammatory changes of the metabolic syndrome, the endothelial dysfunction associated and the possibly central role of the adipocyte (Fig. 1). Within that context, the hypothesis was put forward that blockade of the angiotensin system might prevent type-II diabetes via effects on fat cells (9).

Rationale: The effects of different angiotensin-II-type-1-receptor antagonists on insulin sensitivity have been investigated in various studies with different, either positive (10) or negative (11, 12) results but no in-depht investigations into detailed metabolic and vascular effects have been performed.

Telmisartan is an angiotensin-II-type-1-receptor antagonist that very recently has been described to possess the specific properties of a partial activator of PPARγ (13). This effect is not found for other comparable compunds such as losartan. Genes of whom the expression is under control of that receptor are centrally involved into the pathology of the metabolic syndrome as outlined above and activation of that receptor results in improved insulin sensitivity, ameliorated endothelial dysfunction, reduced inflammation and potentially preserved beta-cell function (for review see (14)). Therefore, telmisartan is a candidate that might possess very specific beneficial properties in addition to its antihypertensive effects.

Objective: To compare the metabolic and vascular effects of telmisartan and metoprolol in hypertensive patients with IGT.