Capacity and Hypoxic Response of Subcutaneous Adipose Tissue Blood Flow in Humans

Abstract

The vasodilatation capacity of human subcutaneous adipose blood flow appears to be comparable to, or even higher, than that induced by moderate intensity exercise. Furthermore, the reduced blood flow response in subcutaneous adipose tissue during systemic hypoxia is likely to contribute, in part, to the redistribution of blood flow to exercising muscle in a condition of reduced oxygen availability.

The Circulatory and Metabolic Responses to Hypoxia in Humans – With Special Reference to Adipose Tissue Physiology and Obesity

“…This fact is well illustrated by cell culture studies, where exposure of adipocytes to low oxygen levels alters the gene expression of over 1000 genes (25). However, no change in subcutaneous adipose tissue blood flow is necessarily observed at rest in humans in response to moderate systemic hypoxia (37). Adipose tissue blood flow in humans is under the regulation of the sympathetic nervous system (38), and it is, therefore, reasonable to assume that moderate systemic hypoxia simply does not create a high enough stimulus for sympathetic neural vasoconstrictor activation to reduce blood flow in healthy human adipose tissue.…”

“…Furthermore, at rest, but not during exercise, subcutaneous adipose blood flow is under the control of nitric oxide (42). In contrast to resting conditions, subcutaneous adipose blood flow is reduced during exercise, when subjects breathe hypoxic air (37). This novel finding is likely based on the constriction of adipose tissue vasculature by hypoxia-triggered enhanced sympathetic nervous system activity, which redistributes limb blood flow to exercising muscles, which depend more critically on adequate oxygen supply in response to exercise.…”

“…In this regard, a novel finding is that the vasodilatory capacity of human subcutaneous adipose tissue determined by infusion of exogenous dilator compounds approaches the physiological level reached during moderate intensity exercise (37). Furthermore, during this maximal vasodilation, vascular conductance can reach a level even higher than that induced by exercise.…”

High-Intensity Interval Training in Normobaric Hypoxia Improves Cardiorespiratory Fitness in Overweight Chinese Young Women

“…This plateau in adipose tissue blood flow during high-intensity exercise is considered an important mechanism for decreasing free fatty acid mobilization during the exercise (Romijn et al, 1993), and alternatively, increasing the contribution of aerobic/anaerobic glycolysis to ATP generation. Recently, it was found that adipose tissue blood flow is further reduced during exercise with hypoxic breathing, possibly due to hypoxia-triggered enhanced sympathetic vasoconstriction in adipose tissue vasculature (Heinonen et al, 2014). Although the present study did not examine fat metabolism during the 5-wk HIIT, it is reasonable to postulate that a marked increase in fat metabolism in the HYP group in comparison to that of NORM group is unlikely to occur during the intervention period.…”

Metabolic imaging in obesity: underlying mechanisms and consequences in the whole body

“…Similarly, 11 weeks of moderate‐ or higher‐intensity aerobic exercise training in overweight subjects led to a reduction in fat masses, but did not modify insulin‐mediated glucose uptake in subcutaneous femoral adipose tissue . Interestingly, the exercise stimulation of blood flow occurring in adipose tissue adjacent to working muscles is abolished under moderate hypoxia . Different from these two short‐term lifestyle interventions, bariatric surgery was accompanied by an increased insulin sensitivity in several adipose tissue depots after 6 months .…”