Systemic nicotine stimulates human adipose tissue lipolysis through local cholinergic and catecholaminergic receptors.
OBJECTIVE
To evaluate whether the lipolytic effects of systemic nicotine are not only attributed to indirect adrenergic mechanisms, but also to a direct action of nicotine on fat cells.


METHODS
The effect of a systemic nicotine infusion (0.5 microg/kg/min for 30 min) on lipolysis in subcutaneous adipose tissue was investigated in situ in 11 non-obese, non-smoking, healthy male subjects under placebo-controlled conditions.


METHODS
By using microdialysis probes the glycerol levels (lipolysis index) and blood flow were monitored locally in subcutaneous adipose tissue.


RESULTS
Plasma nicotine levels peaked (7.2 ng/ml) at the end of the infusion. Nicotine induced a mean (+/-s.e.) percentage peak increase in adrenaline and noradrenaline plasma levels of 213+/-30% (P<0.01) and 118+/-5% (P<0.05), respectively. Nicotine increased venous plasma glycerol levels by 144+/-9% (P<0.001), arterialized plasma glycerol levels by 148+/-12% (P<0.001) and adipose glycerol levels by 148+/-16% (P<0.001), but did not alter blood flow. By inducing a local cholinoceptor blockade with mecamylamine (10(-5) M) via the microdialysis system, the increase in adipose glycerol levels was inhibited by approximately 45% (P=0.02). A corresponding local beta-adrenoceptor blockade with propranolol (10(-4) M), inhibited the increase in adipose glycerol levels by approximately 60% (P=0.02). Infusion of saline (ie placebo) had no effect on the parameters mentioned above.


CONCLUSIONS
Systemically administered nicotine induces lipolysis, in part by activating the classical adrenergic mechanism (mediated by a nicotine-induced release of catecholamines stimulating beta-adrenoceptors), and in part by directly activating a nicotinic cholinergic lipolytic receptor located in adipose tissue.
Andersson
K
K
Department of Medicine and Research Center, Huddinge Hospital, Karolinska Institute, Huddinge, Sweden.
Arner
P
P
D000273:Adipose Tissue / Q000378:metabolism*; D000328:Adult; D005990:Glycerol / Q000097:blood; D006801:Humans; D007262:Infusions, Intravenous; D007700:Kinetics; D008066:Lipolysis / Q000187:drug effects*; D008297:Male; D017551:Microdialysis; D009538:Nicotine / Q000008:administration & dosage* / Q000097:blood*; D018722:Nicotinic Agonists / Q000494:pharmacology; D017983:Receptors, Catecholamine / Q000378:metabolism*; D011950:Receptors, Cholinergic / Q000378:metabolism*
D018722:Nicotinic Agonists; D017983:Receptors, Catecholamine; D011950:Receptors, Cholinergic; D009538:Nicotine; D005990:Glycerol