Endothelial function in the post-prandial state
Introduction
Modern man in westernised cultures lives in a post-prandial state most of the day. This situation is different from historic times when man was essentially a hunter–gatherer with infrequent meals when shortage of food supply was more common. Long periods of a post-absorptive state ensued when food was scarce and survival was dependent on adaptive metabolic mechanisms to deal with food-deprived situations. Not only the quantity of food has changed over times. The composition of food has changed from a diet high in carbohydrates and fibres to diets with a substantial amount of fat. Nutritional surplus has led to overindulgence in eating which is largely responsible for a startling rise in the incidence of obesity and type 2 diabetes, both conditions being important risk factors for cardiovascular disease. Furthermore, the frequency of meals, including snacks, is such that most people in the western world are in an absorptive state for at least 16 hours per day. It could be argued that food consumption has changed from a means for survival to a severe cardiovascular risk factor in a substantial proportion of affluent populations.
Food intake is associated with both acute and chronic effects on the cardiovascular system. Chronic effects of excessive food intake are related to the development of obesity, type 2 diabetes, hypertension and other metabolic changes such as dyslipidemia, all of which are important risk factors for cardiovascular disease. In addition, specific meal components acutely affect vascular function. Whether these acute meal-induced challenges confer an extra cardiovascular risk over chronic challenges to the vasculature remains an important question to be determined.
Section snippets
Endothelium
Since the landmark studies by Furchgott and Zawadski in 1980 showing that acetylcholine-induced vasorelaxation is dependent on a functional endothelial lining of blood vessels, the endothelium has been assigned a central role in maintaining vascular integrity [1]. The endothelium releases a large number of factors with differential effects. A delicate balance between vasodilating, anti-thrombotic, anti-proliferative, anti-inflammatory, angiogenic factors (nitric oxide (NO), endothelium-derived
Endothelium-dependent vasodilation
Endothelium-dependent vasorelaxation in the forearm can be measured by invasive and non-invasive techniques. The forearm microcirculation can be assessed by intra-arterial administration of vasoactive substances followed by measurement of forearm blood flow (FBF) using venous occlusion strain gauge plethysmography. The brachial conduit artery can be used to assess flow-mediated vasodilation (FMD) after forearm ischemia by a high-resolution vascular ultrasound technique. The vascular ultrasound
Cardiovascular disease and the post-prandial state
The frequent meals together with the abundance of food lead to a prolonged absorptive state. This state is characterised by several features which are associated with an increased risk for cardiovascular disease: glucose excursions, hypertriglyceridemia and increased remnant particles, proneness of low-density lipoprotein to oxidation, increased PAI-1, increased sympathetic tone and hypertension and increased oxidative stress [8].
During the past 5 years many publications have appeared on
Conclusions
Most studies show that the post-prandial state, either induced by a mixed meal or by a glucose, fat or methionine challenge, is associated with impaired endothelium-dependent vasorelaxation. The significance of this transient impairment of vasorelaxation after a meal for the development and/or progression of atherosclerosis is as yet unclear. The attenuation of post-prandial endothelial function by antioxidants such as vitamin C and E suggests that enhanced production of reactive oxygen species
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