Effect of Chronic Aerobic Exercise on Cutaneous Microcirculatory Flow Response to Insulin Iontophoresis and to Ischemia in Elderly Males

Abstract

The aim of this study was to assess whether chronic aerobic exercise can favourably influence the vascular activity of insulin in elderly subjects. We measured in arbitrary units (A. U.) the cutaneous blood flow basally and in response to iontophoresis of insulin, by the means of a Laser Doppler flowmeter, on the right arm of 10 elderly athletes (10 males, aged 65 +/- 6 years) and of 10 sex- and age-matched sedentary subjects. The cutaneous blood flow response to ischemia was also explored in the right leg of the same subjects by means of the same instrument. No significant differences in cutaneous arm and leg blood flow were observed basally between athletes and sedentary subjects (7.25 +/- 2.65 A. U. versus 6.35 +/- 4.04 A. U. and 9.74 +/- 5.11 A. U. versus 9.41 +/- 6.40 A. U., respectively). Cathodal iontophoresis (six poulses of 0.1 mA each for 20 s, with 40-s interval between stimulations) of regular insulin (0.1 ml Humulin R 100 IU/ml diluted 1/10 with 0.9 % saline) induced a significant increase of cutaneous blood flow in both groups (p < 0.01 in athletes, p < 0.01 in sedentary subjects). However the maximal cutaneous blood flow response to insulin was higher in athletes than in sedentary subjects (24.69 +/- 13.34 A. U. versus 14.33 +/- 7.73 A. U., respectively, p < 0.05) as well as the curve of the net blood flux response to insulin iontophoresis (% change from baseline in response to insulin minus % change from baseline in response to saline iontophoresis) (p < 0.001 ANOVA for repeated measures). After ischemia there was a significant increase of leg cutaneous blood flow in both groups (p < 0.001 in athletes and in sedentary subjects) with higher blood flow response in athletes than in sedentary subjects (38.18 +/- 17.08 A. U. versus 26.01 +/- 6.39 A. U., respectively, p < 0.05). The time reached from the release of ischemia to peak-flow was significantly longer in sedentary subjects than in athletes (43.5 +/- 28.5 s versus 20.0 +/- 9.3 s, p < 0.05, respectively). These results suggest that chronic aerobic exercise increases insulin vasodilatory activity and improves endothelial function in elderly subjects.

Impaired microvascular perfusion: a consequence of vascular dysfunction and a potential cause of insulin resistance in muscle

“…Rossi and colleagues (137)(138)(139) have analyzed the reflected LDF signal from skin to provide indirect assessment of vasomotion (10). In humans they have interpreted the spectrum as follows: the highest frequency peak that manifests in the arterial tree and in the microvascular blood flow signal reflects the heart beat that ranges from 0.6 Hz in sportsmen to 1.6 Hz in subjects with impaired cardiovascular function.…”

“…Accordingly, it is possible that regular exercise leads to a generalized "vascular fitness," along with as well as having a number of beneficial effects in improving endothelial vasodilator function and left ventricular diastolic function and decreasing total and abdominal fat (169). We already know that exercise training of rats enhances insulinmediated capillary recruitment and glucose uptake in muscle (129) as well as skin blood flow responses to insulin in elderly humans (139). Could regular exercise have a general effect to enhance vascular fitness?…”

Transdermal iontophoresis as an in-vivo technique for studying microvascular physiology

“…Histamine has been delivered by iontophoresis to study the effect of antihistamine drugs (Leroy et al, 1998), to analyze neurogenic flare reactions (Bickel et al, 2002) and to assess the pharmacodynamics of histamine itself (Jones et al, 2009). Iontophoresis has also been used to study the effect of exercise (Rossi et al, 2005) and obesity (de Jongh et al, 2008) on the local microvascular responses to insulin as well as to investigate the role of calcitonin gene-related peptide in migraine (Edvinsson and Edvinsson, 2008;Rossi et al, 2007).…”

Skin glucose metabolism and microvascular blood flow during local insulin delivery and after an oral glucose load

“…Transdermal iontophoresis has been used for local delivery of insulin to the skin, in combination with laser Doppler flowmetry for measurement of microvascular responses in the skin. 3,[12][13][14][15] However, the delivery of insulin via iontophoresis has been found challenging because of a substantial nonspecific vasodilatation caused by the diluting medium of the drugs that have been used. 3,12,13 Also, because metabolic effects cannot be directly studied using optical techniques, previous studies using transdermal iontophoresis have been limited to measurement of vascular effects.…”