Effects of calcium antagonists on insulin secretion

Aim

Citolic calcium levels influence glucose-stimulated insulin secretion. In vitro studies have shown that calcium antagonists can inhibit insulin secretion and thus to alter glucose metabolism.

The aim of our work was to study if long-term calcium-antagonists treatment alters insulin secretion in vivo.

Patients and Methods

Two groups of essentiai hypertensive patients were studied: one with obesity (n=18) and the other one without obesity (n=8). All of the patients had normoglucose tolerance and no family history of diabetes mellitus. All patients underwent a frequently sampled intravenous glucose tolerance test for 180 minutes (FSIVGTT). The obese group was placed on Diltiazem (360mg/d) and the group without obesity on Nitrendipine (20mg/d), for 12 weeks, and the FSIVGTT was repeated. Insulin secretion was calculated as the area under the curve.

Results

Patients placed on Nitrendipine did not show any significant difference neither in fasting insulin (11±5 vs. 9±5, µU/mL) nor in total insulin secretion (3273±1458 vs. _i3114±1220, µU/ml.min). The peak of insulin was similar (66±27 vs. 72±22, µU/mL). Patients placed on Diltiazem did not show any significant differences neither in fasting insulin (17±9 vs. 17±9, µU/mL) nor in totall insulin secrction (6052±3096 vs. 5698±3319, µU/mL.min). The peak of insulin was also similar (112±99 vs. 118±87, µU/mL). Moreover, both calcium antaginists did not cause delay on insulin secretion, and we did not find any significant difference in C-peptide levels.

Conclusions

Our data suggest that calcium-antagonists do not impair intravenous glucose-stimulated insulin secretion in vivo.