Importance of beta-adrenoceptor function in fat cells for lipid mobilization.
The role of peripheral catecholamine sensitivity in lipid mobilization was investigated in 78 healthy non-obese subjects by comparing beta-adrenergic regulation of lipolysis in isolated adipocytes with circulating catecholamines and glycerol (lipolysis index). Small intra-individual variations (5-7%) in adipocyte lipolytic beta-adrenoceptor sensitivity (ED50) for isoprenaline were found. However, large inter-individual variations (almost 10(5)-fold) in isoprenaline ED50 were observed in abdominal or gluteal adipocytes, which correlated (r = 0.52) negatively with the resting plasma noradrenaline levels. A correlation was also observed between circulating noradrenaline and adipocyte ED50 for noradrenaline (r = -0.38). In subjects with high (ED50 less than 10(-11) mol l-1) as compared to low isoprenaline sensitivity (ED50 greater than 10(-10) mol l-1) physical exercise induced a two times greater increase in plasma glycerol (P less than 0.01), in spite of a 50% less marked increase of plasma noradrenaline (P less than 0.01). Findings with beta-adrenoceptor mRNA and with total beta-adrenoceptor number or affinity for agonist did not show any strong correlation with the resting plasma noradrenaline level (r less than 0.25). In conclusion, inter-individual variations in beta-adrenoceptor sensitivity and its relation to circulating noradrenaline can be ascribed to specific modulations of either BAR-subtypes or in the postreceptor activation of lipolysis. These variations in adipocyte beta-adrenoceptor sensitivity may participate in the regulation of peripheral nervous activity and play a putative role in lipolysis during exercise when subjects with high beta-adrenoceptor sensitivity increased their ability to mobilize lipids despite a reduced noradrenaline response.
Wahrenberg
H
H
Karolinska Institute, Huddinge Hospital, Sweden.
Lönnqvist
F
F
Hellmér
J
J
Arner
P
P
D000273:Adipose Tissue / Q000166:cytology / Q000378:metabolism*; D000328:Adult; D002395:Catecholamines / Q000097:blood; D005260:Female; D005990:Glycerol / Q000097:blood; D006801:Humans; D066298:In Vitro Techniques; D008066:Lipolysis / Q000502:physiology*; D008297:Male; D012333:RNA, Messenger / Q000235:genetics; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000235:genetics / Q000502:physiology*
D002395:Catecholamines; D012333:RNA, Messenger; D011943:Receptors, Adrenergic, beta; D005990:Glycerol