Age-dependent reprogramming of vascular metabolism compromises endothelial resilience to inflammation-induced endothelial dysfunction

Endothelial dysfunction is a hallmark of vascular inflammation and aging. However, the role of cellular bioenergetics in the age-dependent resilience of endothelial function to inflammation has not yet been characterized. Therefore, the aim of this study was to determine whether IL-1β-induced inflammation differentially influences vascular metabolism and endothelial function in the isolated aorta of aged mice compared to young mice. Aorta from young (3-8 months) and old (22-28 months) C57BL/6 mice was isolated and subjected to ex vivo analysis of endothelial function using wire myography and vascular NO production by electron paramagnetic resonance spectroscopy (EPR). Cellular bioenergetics was assessed with the Seahorse extracellular flux analyzer for the measurement of mitochondrial respiration and glycolysis. ¹³C₆-glucose flux and high-energy phosphates were measured by liquid chromatography-tandem mass spectrometry and HPLC, respectively. IL-1β-induced impairment of endothelium-dependent relaxation was more severe in old mice. In young mice, IL-1β triggered metabolic activation characterized by increased mitochondrial respiration, glycolysis, and tricarboxylic acid cycle (TCA) activity. In contrast, in the aorta of aged mice, a blunted metabolic response was observed with a shift to the pentose phosphate pathway (PPP). Pharmacological inhibition of PPP restored endothelial function in the aorta of old but not young mice in the presence of IL-1β, indicating a maladaptive role of PPP hyperactivation in the ageing vasculature. In the aorta of aged mice, pyruvate oxidation and metabolic flux into TCA were impaired in response to IL-1β, with a concomitant activation of anaplerotic pyruvate-derived carbon influx into TCA and the malate-aspartate shuttle (MAS). Furthermore, using specific pharmacological inhibitors of oxidative phosphorylation and glycolysis, we demonstrated that mitochondrial respiration, but not glycolysis, was required for NO-dependent vasodilation in the aorta. In conclusion, our findings reveal that age-dependent metabolic reprogramming drives distinct vascular metabolic responses to IL-1β-induced inflammation, contributing to greater susceptibility of aged vessels to impaired NO-dependent endothelial function in response to IL-1β.