Noradrenaline-induced lipolysis in isolated mesenteric, omental and subcutaneous adipocytes from obese subjects.
Level 5 - mechanism / opinion, no new human data
Ex vivo physiological laboratory study on isolated human tissue samples
PubMed 9368819 · doi:10.1038/sj.ijo.0800504
What was done
Researchers isolated mesenteric, omental, and subcutaneous adipocytes from 13 otherwise healthy obese individuals (9 females, 4 males). In vitro lipolytic responses (glycerol release) were compared across depots under stimulation with varying concentrations of noradrenaline, isoprenaline, selective beta-1 (dobutamine), beta-2 (terbutaline), and beta-3 (CGP 12177) agonists, and noradrenaline in the presence of the alpha-2 adrenoceptor antagonist yohimbine.
What was found
Noradrenaline-induced lipolytic response was identical between omental and mesenteric adipocytes but was 50% higher than in subcutaneous adipocytes (P < 0.05). Noradrenaline sensitivity, intrinsic activity, and isoprenaline sensitivity (5 times higher) were greater in the visceral depots than in subcutaneous fat cells. Yohimbine increased noradrenaline intrinsic activity close to that of isoprenaline. CGP 12177 sensitivity and intrinsic activity were significantly higher in visceral adipocytes compared to subcutaneous adipocytes, while no significant differences across depots were found for dobutamine and terbutaline.
Why it matters
This study demonstrates that mesenteric and omental fat depots exhibit similar adrenoceptor responsiveness, with both visceral depots showing greater catecholamine-induced lipolytic sensitivity than subcutaneous fat due to enhanced beta-3 and reduced alpha-2 adrenoceptor activity.
Limits
The study is limited by a small sample size (n = 13) and an exclusively obese population without lean controls. The findings derive from an ex vivo isolated cell incubation model, which does not account for in vivo physiological variables such as tissue perfusion, hormonal milieu, or neural regulation.
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- supports Visceral adipocytes are more responsive to epinephrine-stimulated lipolysis than subcutaneous adipocytes.