Variation in adrenergic regulation of lipolysis between omental and subcutaneous adipocytes from obese and non-obese men.
Level 4 - case-series / case-control
Cross-sectional comparative ex vivo human tissue study
What was done
Adrenergic regulation of lipolysis was measured and compared ex vivo in isolated omental and subcutaneous adipocytes from 15 obese and 14 non-obese male subjects. Clinical parameters (waist-to-hip ratio, blood pressure, plasma insulin, plasma triglycerides) and adrenoceptor responses (noradrenaline-induced glycerol release, beta-1- and beta-3-adrenoceptor sensitivity and lipolytic rates) were evaluated.
What was found
Obese subjects had increased waist-to-hip ratio, blood pressure, plasma insulin, and plasma triglycerides. In non-obese subjects, regional differences were limited to a slight increase in omental noradrenaline sensitivity (P < 0.05) due to increased beta-1-adrenoceptor sensitivity (P < 0.05). In obese subjects, omental adipocytes showed a 2-fold higher rate of noradrenaline-induced glycerol release (P < 0.005) and 3-fold higher noradrenaline sensitivity (P < 0.05) versus subcutaneous adipocytes. This was driven by a 50-fold increase in omental beta-3-adrenoceptor sensitivity (P < 0.002) and a 6-fold increase in beta-1-adrenoceptor sensitivity (P < 0.02), along with increased lipolytic rates for both subtypes at approximately 50% receptor occupancy (P < 0.05).
Why it matters
This paper identifies receptor-specific mechanisms—predominantly beta-3-adrenoceptor upregulation—underlying the heightened lipolytic response of visceral fat in obese men, which may drive portal free fatty acid delivery and metabolic complications.
Limits
The study is small (29 total subjects) and restricted to men, limiting generalizability. As an ex vivo tissue study, it cannot fully capture in vivo sympathetic nervous tone, regional blood flow, or whole-body endocrine interactions.
Cited by
- supports Visceral adipocytes are more responsive to epinephrine-stimulated lipolysis than subcutaneous adipocytes.