Measurement of insulin sensitivity: Influence of potassium supply during euglycaemic glucose clamps in healthy volunteers

Summary

Insulin sensitivity can be quantitatively measured by the hyperinsulinaemic euglycaemic glucose clamp technique. Infusion of insulin during the clamp procedure leads to a decline of kalae-mia unless potassium is supplied. We investigated whether supplementation of potassium during euglycaemic glucose clamps influences insulin sensitivity. In a randomised study the insulin sensitivity index (SO was determined with two-step hyperinsulinaemic (insulin infusion rates 0.25 (step 1) and 1.0 mU kg⁻¹ min⁻¹ (step 2)) euglycaemic (5.0 mmol L⁻¹) glucose clamps in 20 healthy male volunteers on two different study days. On one day blood potassium was kept constant by means of a variable i.v. potassium chloride infusion (“eukalaemic potassium clamp”), whereas on the other day the decline in blood potassium was monitored only. Without potassium supply kalaemia decreased from basal levels of 4.35 ±0.18 mval L⁻¹ to 4.25 ±0.17 (step 1) and further to 3.88 ± 0.14 mval L^−l (step 2 (mean ± SD)). Without and with potassium supply the insulin sensitivity index measured was comparable (S_r 10.6 ± 3.6 vs. 9.5 ± 3.5 ml min⁻¹ m² per μU ml⁻¹, n.s.; glucose infusion rates 3.6 ± 1.6/12.6 ± 2.6 (step 1/step 2) vs. 3.7 ± 1,5/12.2 ± 2.7 mg kg⁻¹ min⁻¹, n.s.). In conclusion, this study shows that potassium supply during hyperinsulinaemic euglycaemic glucose clamps in healthy subjects does not influence the insulin sensitivity index.

Key words

Insulin sensitivity - insulin secretion - blood potassium - euglycaemic glucose clamp