Post-prandial hyperlipidaemia results in systemic nitrosative stress and impaired cerebrovascular function in the aged

Abstract

Post-prandial hyperlipidaemia (PPH) acutely impairs systemic vascular endothelial function, potentially attributable to a free radical-mediated reduction in vascular nitric oxide (NO) bioavailability (oxidative-nitrosative stress). However, it remains to be determined whether this extends to the cerebrovasculature. To examine this, 38 (19 young (≤35 years) and 19 aged (≥60 years)) healthy males were recruited. Cerebrovascular function (middle cerebral artery velocity, MCAv) and cerebrovascular reactivity to hypercapnea (CVR_CO₂_Hyper) and hypocapnea (CVR_CO2Hypo) were determined via trans-cranial Doppler ultrasound and capnography. Venous blood samples were obtained for the assessment of triglycerides (photometry), glucose (photometry), insulin (radioimmunoassay), ascorbate free radical (A^•-, electron paramagnetic resonance spectroscopy) and nitrite (NO₂^-, ozone-based chemiluminescence) in the fasted state prior to and 4 h following consumption of a standardized high-fat meal (1362 kcal; 130 g of fat). Circulating triglycerides, glucose and insulin increased in both groups following the high-fat meal (<i>P</i><0.05), with triglycerides increasing by 1.37 ± 1.09 mmol/l in the young and 1.54 ± 1.00 mmol/l in the aged (<i>P</i><0.05). This resulted in an increased systemic formation of free radicals in the young (<i>P</i><0.05) but not the aged (<i>P</i>>0.05) and corresponding reduction in NO₂^- in both groups (<i>P</i><0.05). While the meal had no effect on MCAv in either age group, CVR_CO2Hyper was selectively impaired in the aged (<i>P</i><0.05). These findings indicate that PPH causes acute cerebrovascular dysfunction in the aged subsequent to systemic nitrosative stress.