Acute modulation of adipose tissue lipolysis by intravenous estrogens.
OBJECTIVE
The aim of this study was to determine whether intravenous (IV) conjugated estrogens (EST) acutely enhance the suppression of whole-body or regional subcutaneous adipose tissue (SAT) lipolysis by insulin in postmenopausal women.


METHODS
We assessed whole-body lipolysis by [(2)H(5)]glycerol rate of appearance (Glyc(RA)) and abdominal and femoral SAT lipolysis (interstitial glycerol; Glyc(IS)) by subcutaneous microdialysis. Postmenopausal women (n = 12) were studied on two occasions, with IV EST or saline control (CON), under basal conditions and during a 3-stage (4, 8, and 40 mU/m(2)/min) hyperinsulinemic, euglycemic clamp. Ethanol outflow/inflow ratio and recovery of [(13)C]glycerol during microdialysis were used to assess blood flow changes and interstitial glycerol concentrations, respectively.


RESULTS
Compared with CON, EST did not affect systemic basal or insulin-mediated suppression of lipolysis (Glyc(RA)) or SAT nutritive blood flow. Basal Glyc(IS) in SAT was reduced on the EST day. However, insulin-mediated suppression of lipolysis in SAT was not significantly influenced by EST.


CONCLUSIONS
These findings suggest that estrogens acutely reduce basal lipolysis in SAT through an unknown mechanism but do not alter whole-body or SAT suppression of lipolysis by insulin.
Van Pelt
Rachael E
RE
Department of Medicine, Division of Geriatric Medicine, University of Colorado at Denver and Health Sciences Center, 4200 E. Ninth Ave., Campus Box B-179, Denver, CO 80262, USA. rachael.vanpelt@uchsc.edu
Gozansky
Wendolyn S
WS
Hickner
Robert C
RC
Schwartz
Robert S
RS
Kohrt
Wendy M
WM
D001823:Body Composition / Q000502:physiology; D002247:Carbon Isotopes; D018592:Cross-Over Studies; D004966:Estrogens, Conjugated (USP) / Q000494:pharmacology*; D005260:Female; D015309:Glucose Clamp Technique; D005990:Glycerol / Q000378:metabolism; D006801:Humans; D007275:Injections, Intravenous; D007328:Insulin / Q000378:metabolism*; D008066:Lipolysis / Q000187:drug effects* / Q000502:physiology; D017551:Microdialysis; D008875:Middle Aged; D017698:Postmenopause; D050151:Subcutaneous Fat / Q000187:drug effects* / Q000378:metabolism*
D002247:Carbon Isotopes; D004966:Estrogens, Conjugated (USP); D007328:Insulin; D005990:Glycerol