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

Abstract β 2 adrenergic receptors ( β 2 ARs) are important mediators of lipolysis. The β 2 AR gene is highly polymorphic. To determine the contribution of β 2 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 μ mol/min ( P = .007); 2.0 ± 0.61 vs 5.2 ± 2.3 μ mol/(min kg) ( P = .006); 2.5 ± 0.75 vs 7.8 ± 3.4 μ mol/(min kg) ( P = .003); 10 ± 3.7 vs 17 ± 7.4 μ mol/(min kg) ( P = .09); and 144 ± 45.5 vs 392 ± 111 μ mol/d ( P = .0001), respectively. Mean ± SD basal glycerol concentrations were higher in females compared to males: 62 ± 5.6 vs 36 ± 17 μ mol/L ( P = .003). Basal glycerol concentrations and Ra values were similar by β 2 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.