Estradiol acutely inhibits whole body lipid oxidation and attenuates lipolysis in subcutaneous adipose tissue: a randomized, placebo-controlled study in postmenopausal women

Context: Estradiol (E-2) promotes and maintains the female phenotype characterized by subcutaneous fat accumulation. There is evidence to suggest that this effect is due to increased anti-lipolytic alpha 2A-adrenergic receptors, but whether this requires long-term exposure to E-2 or is an immediate effect is not clear. Objective: To study acute effects of a single dose (4 mg) of 17 beta-E-2 on regional and systemic lipolysis. Methods: Sixteen postmenopausal women (age, 59 +/- 5 years; weight, 67 +/- 10 kg; and BMI, 24.8 +/- 2.9) were studied in a crossover design: i) placebo and ii) 4 mg E-2. Basal and adrenaline-stimulated regional lipolysis was assessed by microdialysis and substrate oxidation rates by indirect calorimetry. Tissue biopsies were obtained to assess lipoprotein lipase activity and mRNA expression of adrenergic, estrogen, cytokine, and vascular reactivity receptors. Results: Acute E-2 stimulation significantly attenuated catecholamine-stimulated lipolysis in femoral subcutaneous adipose tissue (interstitial glycerol concentration (micromole/liter) ANOVA time vs treatment interaction, P = 0.01) and lipolysis in general in abdominal adipose tissue (ANOVA treatment alone, P < 0.05). E-2 also reduced basal lipid oxidation ((mg/kg per min) placebo, 0.58 +/- 0.06 vs E-2, 0.45 +/- 0.03; P = 0.03) and induced a significantly higher expression of anti-lipolytic alpha 2A-adrenergic receptor mRNA (P = 0.02) in skeletal muscle tissue as well as an upregulation of eNOS (NOS3) mRNA (P = 0.02). Conclusion: E-2 acutely attenuates the lipolytic response to catecholamines in subcutaneous adipose tissue, shifts muscular adrenergic receptor mRNA toward anti-lipolytic alpha 2A-receptors, decreases whole body lipid oxidation, and enhances expression of markers of vascular reactivity.