Arterio-venous differences in peripheral blood mononuclear cells across human adipose tissue and the effect of adrenaline infusion

Recent evidence indicates that adipose tissue macrophages and lymphocytes have a major role in the pathophysiology of obesity. The arterio-venous (A-V) difference technique has been used very effectively to understand adipose tissue metabolism in humans in vivo, and we set out to investigate whether it is possible to apply and use this technique to determine A-V differences for peripheral blood mononuclear cells (PBMCs) across human adipose tissue. We used flow-cytometric analysis of arterial blood and venous blood draining upper-(abdominal) and lower-body (femoral) adipose tissue depots in middle-aged volunteers (age 45 +/- 8 years, BMI 25.9 +/- 4.1 kg m(-2)). We determined A-V differences for various PBMCs. In basal conditions, there was evidence of modest retention of some PBMCs in adipose tissue, whereas the infusion of low-dose (physiological) adrenaline led to a marked release of many PBMCs (with little evidence of depot-specific differences). In addition to the demonstration that this approach is technically feasible, these results also indicate that physiological stimuli that change adrenaline concentrations and/or adipose tissue blood flow (such as physical activity) provoke the release of PBMCs from femoral and abdominal adipose depots.