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

Abstract

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 kalaemia 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 (S(I)) 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(-1) (step 2 (mean +/- SD)). Without and with potassium supply the insulin sensitivity index measured was comparable (S1 10.6 +/- 3.6 vs. 9.5 +/- 3.5 ml min(-1) m2 per microU 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.

How to Assess the Quality of Glucose Clamps? Evaluation of Clamps Performed With ClampArt, a Novel Automated Clamp Device

“…13,14 Both automated clamps (by means of the Biostator) [1][2][3][4][5][6][7][8][9][10][11][12] and manual clamps have been used for insulin PK/PD assessments. The metabolic effect of the investigated insulin is characterized by the glucose infusion rate (GIR) needed to keep BG constant at a predefined target BG concentration during a euglycemic glucose clamp.…”

“…Clinical glucose clamp trials have frequently been used for the evaluation of the pharmacokinetic/pharmacodynamic (PK/PD) properties of different kinds of insulin formulations 1-12 or for the determination of insulin sensitivity. 13,14 Both automated clamps (by means of the Biostator) 1-12 and manual clamps have been used for insulin PK/PD assessments. The metabolic effect of the investigated insulin is characterized by the glucose infusion rate (GIR) needed to keep BG constant at a predefined target BG concentration during a euglycemic glucose clamp.…”