There is substantial evidence in the literature that the
adoption of a sedentary lifestyle, obesity, ageing and
chronic diseases lead to an attenuation of endothelial NO
production by reductions in eNOS expression and protein
content (McAllister & Laughlin, 2006) and increases in
NAD(P)Hox expression and protein content (Brandes &
Kreuzer 2005, Silveret al.2007) in the macrovasculature.
Whether these adaptations also occur in the muscle
microvasculature is currently unknown. In obese and
elderly individuals and patients with type 2 diabetes and
cardiovascular disease, an attenuated NO production in
the muscle microvasculature has been implicated in the
development of skeletal muscle insulin resistance (Barrett
et al.2009; Barrettet al.2011), and anabolic resistance
to insulin and amino acids leading to sarcopaenia and
reductions in muscle capillary density (Wagenmakers
et al. 2006). An attenuated endothelial NO production
hasalsobeenimplicatedinthereductioninexercise
hyperaemia that is known to occur in elderly humans
(Schrage et al. 2007; Creceliuset al. 2010) with Spier
et al. (2007) providing evidence that this impairment
indeed occurs in isolated muscle arterioles of old rats
and can be restored by exercise training. Krentzet al.
(2009) have also made the observation that functional
impairments in NO-dependent muscle microvascular
function precede macrovascular impairments in humans
and, therefore, suggested that the muscle microvasculature
should be regarded as a primary target for therapeutic
interventions.
There is substantial evidence in the literature that the
adoption of a sedentary lifestyle, obesity, ageing and
chronic diseases lead to an attenuation of endothelial NO
production by reductions in eNOS expression and protein
content (McAllister & Laughlin, 2006) and increases in
NAD(P)Hox expression and protein content (Brandes &
Kreuzer 2005, Silveret al.2007) in the macrovasculature.
Whether these adaptations also occur in the muscle
microvasculature is currently unknown. In obese and
elderly individuals and patients with type 2 diabetes and
cardiovascular disease, an attenuated NO production in
the muscle microvasculature has been implicated in the
development of skeletal muscle insulin resistance (Barrett
et al.2009; Barrettet al.2011), and anabolic resistance
to insulin and amino acids leading to sarcopaenia and
reductions in muscle capillary density (Wagenmakers
et al. 2006). An attenuated endothelial NO production
hasalsobeenimplicatedinthereductioninexercise
hyperaemia that is known to occur in elderly humans
(Schrage et al. 2007; Creceliuset al. 2010) with Spier
et al. (2007) providing evidence that this impairment
indeed occurs in isolated muscle arterioles of old rats
and can be restored by exercise training. Krentzet al.
(2009) have also made the observation that functional
impairments in NO-dependent muscle microvascular
function precede macrovascular impairments in humans
and, therefore, suggested that the muscle microvasculature
should be regarded as a primary target for therapeutic
interventions.
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