Effects of insulin on adipose tissue blood flow in man - PubMed (original) (raw)

Effects of insulin on adipose tissue blood flow in man

Fredrik Karpe et al. J Physiol. 2002.

Abstract

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.

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Figures

Figure 1

Figure 1. Use of the technique of microinfusion to induce a local increase in adipose tissue blood flow

Adipose tissue blood flow (ATBF) in 4 subjects during saline and isoprenaline microinfusion (10−5 mol l−1) at 2 μl min−1.

Figure 2

Figure 2. Plasma hormone and metabolic responses to oral and intravenous insulin–glucose

Plasma responses to 75 g oral glucose (•) and intravenous insulin–glucose (○) in 15 subjects. Results are shown as means and

m.

Subjects attended the oral glucose experiment first. The intravenous insulin–glucose regimen was then devised on an individual basis to mimic the plasma glucose and insulin concentrations measured on the first visit. Full details are given in the text.

Figure 3

Figure 3. Adipose tissue blood flow in response to oral and intravenous insulin–glucose regimens

Adipose tissue blood flow (ATBF) in response to oral glucose (•) and intravenous insulin–glucose (○) in 15 subjects. Results are shown as means and

m.

Subjects attended the oral glucose experiment first. The intravenous insulin–glucose regimen was then devised on an individual basis to mimic the plasma glucose and insulin concentrations measured on the first visit. Full details are given in the text.

Figure 4

Figure 4. Adipose tissue blood flow in response to euglycaemic insulin–glucose regimen

Adipose tissue blood flow (ATBF) after oral glucose (•),

i.v.

insulin–glucose (○) and

i.v.

eu insulin–glucose (▴) in 4 subjects.

Figure 5

Figure 5. Adipose tissue blood flow in response to oral glucose, and the effects of local administration of insulin by microinfusion

Adipose tissue blood flow (ATBF) in response to low- (4 mU ml−1) and high-dose (400 mU ml−1) insulin infusion and oral glucose (•) in nine subjects. For the control (○), diluent was infused. Full details are given in the text. Results are shown as mean and

s.e.m.

References

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