Submitted on June 24, 2008
Revised on April 16, 2009
Accepted on April 23, 2009
Greater systemic lipolysis in women compared to men during moderate dose infusion of epinephrine and/or norepinephrine
Tracy J. Horton1*, Suzanne Dow2, Michael Armstrong2, and William Troy Donahoo3
1 University Colorado Denver
2 University of Colorado Denver
3 University of Colorado of Endocrinology
* To whom correspondence should be addressed. E-mail: tracy.horton{at}ucdenver.edu.
Women have lower circulating catecholamine levels during metabolic perturbations such as exercise or hypoglycemia, but similar rates of systemic lipolysis and, in certain studies, lower glucose turnover. This suggests women may be more sensitive to the lipolytic action of catcholamines, while maintaining similar glucoregulatory effects. The aim of the current study, therefore, was to determine if women have higher rates of systemic lipolysis compared to men in response to matched peripheral infusion of catceholamines, but similar rates of glucose turnover. Healthy, non-obese women (n=11) and men (n =10) were recruited and studied on 3 separate days with the following infusions: epinephrine (Epi), norepinephrine (Norepi) or the two combined. Tracer infusions of glycerol and glucose were used to determine systemic lipolysis and glucose turnover, respectively. Following basal measurements of substrate kinetics, the catecholamine infusion commenced and measures of substrate kinetics continued for 60 mins. Catecholamine concentrations were similarly elevated in women and men during each infusion; epinephrine,182-197 pg/ml and norepeinephrine, 417-507 pg/ml. There was a significant sex difference in glycerol Ra and Rd with the catecholamine infusions (p<0.0001), mainly due to a significantly greater glycerol turnover during the first 30 minutes of each infusion: glycerol Ra during Epi only was 268 ±18 vs 206 ±21 µmol/min in women and men, respectively; during Norepi only 173 ±13 vs 153 ±17 µmol/min, respectively, and during Epi+Norepi 303 ±24 vs 257 ±21µmol/min, respectively . No sex differences were observed in glucose kinetics under any condition. In conclusion, these data suggest that women are more sensitive to the lipolytic action of catecholamines, but have no difference in their glucoregulatory response. Thus, the lower catcholamine levels observed in women vs men during exercise and other metabolic perturbations, may allow women to maintain a similar or greater level of lipid mobilization while minimizing changes in glucose turnover.
