Exercise, Blood Flow, and the Skeletal Muscle Microcirculation in Diabetes Mellitus

Abstract

Aerobic exercise capacity is impaired in both type 1 diabetes (T1DM) and type 2 diabetes (T2DM), and this impairment is predictive of future morbidity and mortality. Although the precise etiology of impaired exercise capacity in diabetes remains unclear, several distinct lines of evidence indicate that reduced delivery of oxygen by the cardiovascular system plays a causal role. Cardiac output is often but not always reduced in diabetes. This change is sufficient but not necessary for reduced exercise capacity. Skeletal muscle blood flow is also often but not always reduced in diabetes. This change is also sufficient but not necessary for reduced exercise capacity. In addition, a growing number of animal and simulation studies show that heterogeneous distribution of blood flow within the microcirculation contributes to oxygen delivery limitations in diabetes. Once again, this change is sufficient but not necessary for reduced exercise capacity. In this chapter, we discuss each of these changes in cardiovascular function and their likely causes, beginning with the heart and gradually progressing to capillary level. We then conclude our overview by interpreting the causality or lack thereof of each diabetes-related pathological change as it relates to reduced oxygen delivery to the skeletal muscle.