The evolutionary consequences of oxygenic photosynthesis: a body size perspective
Low-birth-weight babies have an increased risk of cardiovascular disease (CVD) in later life. The authors hypothesize that fetal hypoxia alters the structure and function of the developing cardiovascular system resulting in CVD. They investigated the effects of chronic hypoxia on cardiac performance, hemodynamic control, and growth during the second half of embryonic chick development. Three stages of hemodynamic adaptations were identified in hypoxic chick embryos. At embryonic day 13 (E13), heart rate and blood pressure were higher in hypoxic embryos. At E17, this was followed by sympathetic hyperinnervation of peripheral arteries, resulting in increased vasoconstriction during a chemoreflex. This was accompanied by dilatation of the left ventricle and a 50% reduction in cardiac contractility. E19 hypoxic embryos had a 33% higher baseline vascular tone, but failed to maintain blood pressure during acute stress, indicating cardiac failure. Reduced body, heart, and liver weights followed the hemodynamic changes. Chronic hypoxia induces dilated cardiomyopathy and sympathetic hyperinnervation of the peripheral vasculature leading to aberrant fetal hemodynamics and fetal growth restriction. This study identifies that alterations in fetal hemodynamic regulation are in the causal pathway between disturbances in fetal environment, restricted fetal growth and CVD, and establishes fetal hypoxia as a novel risk factor for cardiovascular disease.