Effect of beta-adrenergic stimulation on whole-body and abdominal subcutaneous adipose tissue lipolysis in lean and obese men.
OBJECTIVE
Obesity is characterised by increased triacylglycerol storage in adipose tissue. There is in vitro evidence for a blunted beta-adrenergically mediated lipolytic response in abdominal subcutaneous adipose tissue (SAT) of obese individuals and evidence for this at the whole-body level in vivo. We hypothesised that the beta-adrenergically mediated effect on lipolysis in abdominal SAT is also impaired in vivo in obese humans.


METHODS
We investigated whole-body and abdominal SAT glycerol metabolism in vivo during 3 h and 6 h [2H5]glycerol infusions. Arterio-venous concentration differences were measured in 13 lean and ten obese men after an overnight fast and during intravenous infusion of the non-selective beta-adrenergic agonist isoprenaline [20 ng (kg fat free mass)(-1) min(-1)].


RESULTS
Lean and obese participants showed comparable fasting glycerol uptake by SAT (9.7+/-3.4 vs 9.3+/-2.5% of total release, p=0.92). Furthermore, obese participants showed an increased whole-body beta-adrenergically mediated lipolytic response versus lean participants. However, their fasting lipolysis was blunted [glycerol rate of appearance: 7.3+/-0.6 vs 13.1+/-0.9 micromol (kg fat mass)(-1) min(-1), p<0.01], as was the beta-adrenergically mediated lipolytic response per unit SAT [Delta total glycerol release: 140+/-71 vs 394+/-112 nmol (100 g tissue)(-1) min(-1), p<0.05] compared with lean participants. Net triacylglycerol flux tended to increase in obese compared with lean participants during beta-adrenergic stimulation [Delta net triacylglycerol flux: 75+/-32 vs 16+/-11 nmol (100 g tissue)(-1) min(-1), p=0.06].


CONCLUSIONS
We demonstrated in vivo that beta-adrenergically mediated lipolytic response is impaired systematically and in abdominal SAT of obese versus lean men. This may be important in the development or maintenance of increased triacylglycerol stores and obesity.
Department of Human Biology, Nutrition and Toxicology Research Institute Maastricht (NUTRIM), Maastricht University, and Department of Nuclear Medicine, University Hospital Maastricht, Maastricht, The Netherlands. J.Jocken@HB.Unimaas.nl
J W E
JW
Jocken
G H
GH
Goossens
A M J
AM
van Hees
K N
KN
Frayn
M
M
van Baak
J
J
Stegen
M T W
MT
Pakbiers
W H M
WH
Saris
E E
EE
Blaak
D000273:Adipose Tissue / Q000187:drug effects* / Q000378:metabolism; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000328:Adult; D001823:Body Composition; D015992:Body Mass Index; D005215:Fasting; D005230:Fatty Acids, Nonesterified / Q000097:blood / Q000378:metabolism; D005260:Female; D005990:Glycerol / Q000097:blood / Q000378:metabolism; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D008066:Lipolysis / Q000187:drug effects*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood / Q000378:metabolism*; D010865:Pilot Projects; D050151:Subcutaneous Fat / Q000187:drug effects / Q000378:metabolism; D013851:Thinness / Q000097:blood / Q000378:metabolism*; D014280:Triglycerides / Q000097:blood / Q000378:metabolism
D000318:Adrenergic beta-Agonists; D005230:Fatty Acids, Nonesterified; D014280:Triglycerides; D007545:Isoproterenol; D005990:Glycerol