We recently reported that our group (n = 502) of type 2 diabetic subjects did not reveal statistically significant differences in BMI with respect to the three groups of carriers of β2-adrenergic receptor polymorphisms (1). Meirhaghe et al. (1) report that in men not participating in physical activity, Gln27Gln carriers had a higher BMI than the Glu27 (combined heterozygous and homozygous) carriers (27.2 ± 0.4 vs. 25.2 ± 0.3 kg/m2), while no effect on BMI was found in the men not participating in physical activity.

We have not collected data on the physical activity of our subjects. However, taking into account that our subjects had a mean age of 61 ± 9 years (roughly 10 years older than the subjects reported by Meirhaghe et al.), we suspect that the vast majority of them do not participate in much physical activity. In any case, their physical activity is presumably less than that of the subjects studied by Meirhaghe et al. Much to our surprise, we actually find the opposite, which is a lower (and not a higher!) BMI (27.2 ± 3.8) in the Gln27Gln carriers compared with the others (27.9 ± 4.4 for Gln27Glu and 28.2 ± 4.0 kg/m2 for Glu27Glu), although the differences did not attain statistical significance. These findings were similar for men and women when taken together or separately.

Obviously, there are two major differences between these two studies. The subjects in our study (2) had type 2 diabetes and were considerably older. Whether these two differences explain the divergent findings of the study of Meirhaghe et al. and our study is uncertain. However, the suggestion by van Tilburg et al. that, if anything, the BMI was lower (and not higher) in the Gln27Gln27 group might point to a chance finding in the studies by Meirhaghe et al. As for the observations regarding the Arg16Gly polymorphism, we have not studied this polymorphisms in our group of subjects.

It has become more and more clear that association studies of a particular polymorphism with a certain physiological parameter are often hard to replicate; this necessitates the need to perform replication studies before a finding can be regarded as truly positive.

1.
van Tilburg JH, Wijmenga C, van Bakel H, Rozeman L, Pearson PL, van Haeften TW: Relationship of β2-adrenergic receptor polymorphism with obesity in type 2 diabetes (Letter).
Diabetes Care
 
26
:
251
–252,
2003
2.
Meirhaghe A, Helbecque N, Cottel D, Amouyel P: B2-adrenoceptor gene polymorphism, body weight, and physical activity.
Lancet
 
353
:
896
,
1999

Address correspondence to Timon W. van Haeften, MD, Department of Internal Medicine, G 02.228, University Medical Center, P.O. Box 85500, 3508 GA Utrecht, The Netherlands. E-mail: [email protected].

DIABETES CARE
2003