Effects of insulin on adipose tissue blood flow in man.
Adipose tissue blood flow (ATBF) rises after nutrient ingestion. It is not clear whether this is due to insulin. The aim of this study was to investigate the role of insulin in the regulation of subcutaneous ATBF. We have investigated the role of insulin in the regulation of ATBF in normal, healthy subjects in a three-step procedure to determine the functional level at which insulin may potentially exert its effect. Fifteen subjects were studied on two occasions. On the first visit, 75 g oral glucose was given. In the second, similar plasma concentrations of insulin and glucose were achieved by dynamic intravenous infusions of insulin and glucose. The increase in ATBF after oral glucose (4.2 +/- 1.4 ml min(-1) (100 g tissue)(-1), P = 0.01) was significantly greater (P < 0.05) than that after intravenous infusions (1.5 +/- 0.6 ml min(-1) (100 g tissue)(-1) P < 0.05). For the local delivery of potentially vasoactive substances and simultaneous measurement of ATBF, we describe a novel combination of methods, which we have called 'microinfusion'. We have used this technique to show that locally infused insulin, even at pharmacological concentrations, had no demonstrable effect on ATBF in nine subjects. We conclude that whilst insulin does not have a direct effect on ATBF, it is likely to be an important mediator, possibly acting via sympathetic activation. In the postprandial state, other candidate peptides and hormones are also likely to play important roles.
Karpe
Fredrik
F
Oxford Lipid Metabolism Group, Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Infirmary, Oxford OX2 6HE, UK. fredrik.karpe@oxlip.ox.ac.uk
Fielding
Barbara A
BA
Ardilouze
Jean-Luc
JL
Ilic
Vera
V
Macdonald
Ian A
IA
Frayn
Keith N
KN
D000273:Adipose Tissue / Q000098:blood supply*; D000284:Administration, Oral; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005947:Glucose / Q000008:administration & dosage; D015309:Glucose Clamp Technique; D006801:Humans; D006946:Hyperinsulinism; D007262:Infusions, Intravenous; D007328:Insulin / Q000008:administration & dosage / Q000097:blood* / Q000494:pharmacology*; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D012039:Regional Blood Flow / Q000187:drug effects*; D013997:Time Factors
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D005947:Glucose; D007545:Isoproterenol