β2-Adrenergic Receptor Polymorphism and Obesity in Type 2 Diabetes: Response to van Tilburg et al.

We read with interest the observation letter by van Tilburg et al. (1) reporting that the Glu27Gln polymorphism of the β2-adrenergic receptor (B2ADR) has no important effect on BMI, metabolic control, or plasma lipids. However, the authors did not mention the physical activity and diet regimen in their study. B2ADR is a major lipolytic receptor in human adipocytes, activated by catecholamines especially during a weight reduction regimen. Meirhaeghe et al. (2) reported that B2ADR Glu27Gln polymorphism is significantly associated with obesity in individuals who do not have regular physical activity, while no effect of such polymorphism is found in those who do have physical activity, and suggested that obese individuals with B2ADR Glu27Gln genotype may benefit from physical activity to reduce their body weight. We also demonstrated the same association between another B2ADR polymorphism (Arg16Gly) and obesity in individuals treated with a combined low-energy diet and exercise regimen (3). Therefore, the authors should have further divided the subjects according to the degree of their physical activity and analyzed the data, because body weight and body fat or metabolic control are influenced by physical activity and dietary changes, especially in individuals with such polymorphisms.