Effects of Type 2 Diabetes on Arterial Endothelium

Abstract

The endothelium, the innermost layer of blood vessels, has many important biological functions which are responsible for regulating vascular tone and structure. One of the major functions of a healthy endothelium is to ensure adequate blood supply to the different tissues. This particular process is regulated by the release and interaction of different vasoactive substances (i.e. vasodilators and vasoconstrictors), which are under tight balance. On the other hand, it is well known that the chronic exposure to certain stresses (e.g. inflammation, oxidative stress, and hyperglycemia) promotes changes in the endothelium leading to endothelial dysfunction. Type 2 diabetes mellitus (T2DM) is among those chronic diseases that are associated with endothelial dysfunction which may contribute to limited glucose uptake in skeletal muscle. In fact, diabetes-related endothelial dysfunction has been reported to lead to morphologic and structural vascular changes present throughout the course of diabetes (Taylor and Poston, 1994). There are around 17 million people in the United States who have diabetes, of whom close to 95% have T2DM. Cardiovascular disease (CVD) is the major cause of morbidity and mortality in people with T2DM (Ness et al., 1999), and coronary heart disease is the most common cause of death among those individuals. For instance, people with T2DM are two to four times more likely to develop CVD compared with people without the condition (Stamler et al., 1993). Interestingly, physical activity is an important therapeutic tool to maintain endothelial function. In fact, regular physical exercise has been reported to be effective in the prevention and delay of onset of T2DM (Bassuk and Manson, 2005; Sanz et al., 2010; Stewart, 2002). Thus the primary purpose of this chapter is to summarize the current available literature concerning the effects of T2DM on arterial endothelium. In addition, this chapter is intended to summarize evidence of the beneficial effects of physical activity on the untoward cardiovascular effects of T2DM and/or the apparent ability of physical activity to prevent progression of diabetes-induced CVD.