Effect of Insulin Catheter Wear-Time on Subcutaneous Adipose Tissue Blood Flow and Insulin Absorption in Humans

Abstract

Background: Insertion of an insulin catheter for continuous subcutaneous insulin infusion into the subcutaneous adipose tissue (SAT) causes a tissue trauma that may have consequences for insulin absorption. We evaluated the importance of insulin catheter wear-time on subcutaneous adipose tissue blood flow (ATBF) and absorption of the rapid-acting insulin analog insulin aspart over a period of 4 days. Methods: Teflon insulin catheters (Medtronic, Minneapolis, MN) were inserted into the abdominal SAT of 10 healthy men without diabetes (mean ± SEM age, 23.0 ± 1.1 years; body mass index, 22.1 ± 0.7 kg/m²) and connected to an insulin pump delivering a constant rate of isotonic saline for 4 days. Subjects participated in four study days (days 0, 1, 2, and 4) during which ATBF around the catheter tip was measured by ¹³³Xe clearance and absorption of an insulin aspart bolus (0.1 U/kg) was measured for 4 h. Results: ATBF increased from day 0 to day 2 after catheter insertion (2.6 ± 0.6 to 4.5 ± 0.8 mL/100 g/min; P = 0.030). By day 4, ATBF had returned to day 0 level. Time to peak plasma insulin aspart concentration after bolus administration decreased with catheter wear-time from 55 ± 3 min on day 0 to 45 ± 4 min on day 4 (P = 0.019). Neither peak plasma concentration nor area under the curve of insulin aspart changed significantly. Conclusions: Insertion of a Teflon insulin catheter into the SAT results in increased ATBF and faster absorption of insulin aspart in a period of 4 days without any change in the total amount of insulin aspart absorbed.