Human Molecular Genetics Advance Access originally published online on September 1, 2006
Human Molecular Genetics 2006 15(20):2980-2987; doi:10.1093/hmg/ddl240
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Dipsogenic genes associated with weight changes during Ironman Triathlons
1 Medical Research Council of South Africa and 2 Department of Human Biology, MRC/UCT Research Unit for Exercise Science and Sports Medicine, University of Cape Town, South Africa, 3 Molecular Genetics Department B and Laboratory of Forensic Genetics, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus and 4 Cardiovascular Diagnostic Centre, Nicosia, Cyprus
* To whom correspondence should be addressed at:, MRC/UCT Research Unit for Exercise Science and Sports Medicine, PO Box 115, Newlands 7725, South Africa. Tel: +27 21 650 4574; Fax: +27 21 686 7530; Email: mcollins{at}sports.uct.ac.za
Received July 12, 2006; Revised August 17, 2006; Accepted August 24, 2006
Thirst is regulated by a complex interaction of signalling pathways within the central nervous system, including components of the renin–angiotensin and kalikrein kinin systems, as well as the serotonergic pathways. The aim of this study was to determine whether there were any associations between polymorphisms within the ACE, BDKRB2, NOS3 and/or 5-HTT genes with weight changes during the 2000 and 2001 226 km South African Ironman Triathlons. Pre- and post-race serum [Na+] and body weights, as well as genotype data, were collected from 428 (61.1%) Caucasian male triathletes who were divided into three groups according to their relative weight loss during the triathlon (0–3, 3–5 and >5%). There was a significant linear trend for the distribution of both the BDKRB2 +9/+9 genotype and the 5-HTT SS genotype between the three weight loss groups, with the >5% group having the highest percentage of athletes with the +9/+9 genotype (
2=5.3, P=0.021) and the highest percentage of athletes with the SS genotype (2=5.8, P=0.016). Likewise, the >5% group had the highest percentage of athletes with the combined SS 5-HTT and/or +9/+9 BDKRB2 genotypes (2=7.4, P=0.007). In conclusion, the functional SS genotype of the serotonin transporter-linked polymorphic region (5-HTTLPR) within the 5-HTT gene and the functional +9/+9 genotype of the BDKBR2 gene were associated with larger weight losses during the Ironman Triathlons. These findings suggest the involvement of the serotonergic pathways in the control of thirst and drinking behaviour and provide further evidence for the dipsogenic effect of circulating bradykinin.