Vasodilatory and vascular mitochondrial respiratory function with advancing age: evidence of a free radically mediated link in the human vasculature.

Recognizing the age-related decline in skeletal muscle feed artery (SMFA) vasodilatory function, this study examined the link between vasodilatory and mitochondrial respiratory function in the human vasculature. Twenty-four SMFAs were harvested from young (35 ± 6 yr, = 9) and old (71 ± 9 yr, = 15) subjects. Vasodilation in SMFAs was assessed, by pressure myography, in response to flow-induced shear stress, acetylcholine (ACh), and sodium nitroprusside (SNP) while mitochondrial respiration was measured, by respirometry, in permeabilized SMFAs. Endothelium-dependent vasodilation was significantly attenuated in the old, induced by both flow (young: 92 ± 3, old: 45 ± 4%) and ACh (young: 92 ± 3, old: 54 ± 5%), with no significant difference in endothelium-independent vasodilation. Complex I and I + II state 3 respiration was significantly lower in the old (CI young: 10.1 ± 0.8, old: 7.0 ± 0.4 pmol·s·mg; CI + II young: 12.3 ± 0.6, old: 7.6 ± 0.4 pmol·s·mg). The respiratory control ratio (RCR) was also significantly attenuated in the old (young: 2.2 ± 0.1, old: 1.1 ± 0.1). Furthermore, state 3 (CI + II) and 4 respiration, as well as RCR, were significantly correlated ( = 0.49-0.86) with endothelium-dependent, but not endothelium-independent, function. Finally, the direct intervention with mitochondrial-targeted antioxidant (MitoQ) significantly improved endothelium-dependent vasodilation in the old but not in the young. Thus, the age-related decline in vasodilatory function is linked to attenuated vascular mitochondrial respiratory function, likely by augmented free radicals. In human skeletal muscle feed arteries, the well-recognized age-related fall in endothelium-dependent vasodilatory function is strongly linked to a concomitant fall in vascular mitochondrial respiratory function. The direct intervention with the mitochondrial-targeted antioxidant restored vasodilatory function in the old but not in the young, supporting the concept that exacerbated mitochondrial-derived free radical production is linked to age-related vasodilatory dysfunction. Age-related vasodilatory dysfunction in humans is linked to attenuated vascular mitochondrial respiratory function, likely a consequence of augmented free radical production.