Marked resistance of femoral adipose tissue blood flow and lipolysis to adrenaline in vivo.
OBJECTIVE
Fatty acid entrapment in femoral adipose tissue has been proposed to prevent ectopic fat deposition and visceral fat accumulation, resulting in protection from insulin resistance. Our objective was to test the hypothesis of femoral, compared with abdominal, adipose tissue resistance to adrenergic stimulation in vivo as a possible mechanism.


METHODS
Regional fatty acid trafficking, along with the measurement of adipose tissue blood flow (ATBF) with (133)Xe washout, was studied with the arteriovenous difference technique and stable isotope tracers in healthy volunteers. Adrenergic agonists (isoprenaline, adrenaline [epinephrine]) were infused either locally by microinfusion or systemically. Local microinfusion of adrenoceptor antagonists (propranolol, phentolamine) was used to characterise specific adrenoceptor subtype effects in vivo.


RESULTS
Femoral adipose tissue NEFA release and ATBF were lower during adrenaline stimulation than in abdominal tissue (p < 0.001). Mechanistically, femoral adipose tissue displayed a dominant α-adrenergic response during adrenaline stimulation. The α-adrenoceptor blocker, phentolamine, resulted in the 'disinhibition' of the femoral ATBF response to adrenaline (p < 0.001).


CONCLUSIONS
Fatty acids, once stored in femoral adipose tissue, are not readily released upon adrenergic stimulation. Femoral adipose tissue resistance to adrenaline may contribute to the prevention of ectopic fatty acid deposition.
Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford, UK. k.manolopoulos@bham.ac.uk
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Karpe
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Frayn
D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage; D000318:Adrenergic beta-Agonists / Q000008:administration & dosage; D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage; D000328:Adult; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D004837:Epinephrine / Q000008:administration & dosage*; D005227:Fatty Acids / Q000378:metabolism; D005260:Female; D005269:Femur; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D050152:Intra-Abdominal Fat / Q000098:blood supply / Q000187:drug effects / Q000378:metabolism; D007545:Isoproterenol / Q000008:administration & dosage; D008066:Lipolysis / Q000187:drug effects / Q000502:physiology*; D008297:Male; D010646:Phentolamine / Q000008:administration & dosage; D011433:Propranolol / Q000008:administration & dosage; D012727:Sex Characteristics; D050151:Subcutaneous Fat / Q000098:blood supply / Q000187:drug effects / Q000378:metabolism; D014655:Vascular Resistance / Q000187:drug effects / Q000502:physiology*; D014980:Xenon Radioisotopes
D000317:Adrenergic alpha-Antagonists; D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D005227:Fatty Acids; D014980:Xenon Radioisotopes; D011433:Propranolol; D007545:Isoproterenol; D004837:Epinephrine; D010646:Phentolamine