Background & Objectives: Expanding adipose tissue in obesity requires effective vasoreactivity to combat hypoxia and its consequences, such as insulin resistance and type 2 diabetes. While recent evidence suggests that the adipose tissue is highly angiogenic, the tissue arteriolar vasoreactivity has been less investigated. Furthermore, the omental adipose tissue (OAT) synthesizes greater levels of vasocontrictive molecules, such as cytokines and catecholamines, compared to the sub-cutaneous (SAT) depot and these are likely to impact the maintenance of vascular tone leading to greater susceptibility to hypoxia. The aim of the study was to investigate differences in the contractile responses of adipose tissue arterioles between the SAT and OAT depots in an insulin-resistance prone, morbidly obese Qatari population. Methods: SAT and OAT from obese non-diabetic Qatari patients (age 29, BMI 43, HOMA 2.69), undergoing weight reducing surgery were used to investigate tissue noradrenaline (NA)-mediated vasoconstriction by wire myography. Vessels were cut into segments (~2 mm) and mounted on a dual wire myograph (510A) for measurement of isometric tension. Cumulative concentration-response curves were then constructed for noradrenaline (10-9 -10-5 M). Curves were also constructed for potassium Chloride (KCl, 1-70 mM). Results: Arterioles from SAT showed greater sensitivity to NA compared to OAT (log EC50 -6.9±0.1 vs -6.1±0.2 p<0.05). The SAT curve was clearly shifted to the left of OAT although the maximum tensions for both were not statistically different. For KCl, maximum tension was greater in the SAT than in the OAT vessels but there were no differences in their sensitivities. Conclusions: OAT arterioles from morbidly obese Qataris were less sensitive to noradrenaline mediated vasoconstriction compared to SAT vessels; however, the contractile responses of the two depots to KCl were comparable. Therefore differences in adrenoceptor density/function may underlie the depot specific responses. The consequences of these differences between the arterioles are currently under investigation.


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