Influence of sex and β2 adrenergic receptor haplotype on resting and terbutaline-stimulated whole body lipolysis

β2 adrenergic receptors (β2 ARs) are important mediators of lipolysis. The β2 AR gene is highly polymorphic. To determine the contribution of β2 AR polymorphisms to variability in whole body lipolysis, we compared basal and terbutaline-stimulated lipolytic rates (Ra) using tracer techniques in 14 healthy, non-obese males (n = 7) and females (n = 7) who were homozygous for Cys−19/Arg16/Gln27 or Arg−19/Gly16/Glu27 haplotypes. Fasting (overnight) Ra values were higher in females compared to males. Mean ± SD Ra, Ra/body weight, Ra/fat free mass, Ra/fat, and Ra/energy expenditure rates in males and females were 155 ± 46 vs 311 ± 111 μmol/min (P = .007); 2.0 ± 0.61 vs 5.2 ± 2.3 μmol/(min kg) (P = .006); 2.5 ± 0.75 vs 7.8 ± 3.4 μmol/(min kg) (P = .003); 10 ± 3.7 vs 17 ± 7.4 μmol/(min kg) (P = .09); and 144 ± 45.5 vs 392 ± 111 μmol/d (P = .0001), respectively. Mean ± SD basal glycerol concentrations were higher in females compared to males: 62 ± 5.6 vs 36 ± 17 μmol/L (P = .003). Basal glycerol concentrations and Ra values were similar by β2 AR haplotype. Basal glucose and insulin concentrations tended to be higher in males compared to females and were similar by haplotype. Terbutaline-stimulated changes in glycerol concentrations were variable and are not related to either sex or haplotype. We conclude that compared to haplotype, sex is a more important determinant of basal lipolysis after a 12-hour fast in healthy, non-obese individuals.