Human Molecular Genetics Advance Access published online on September 1, 2006
Human Molecular Genetics, doi:10.1093/hmg/ddl240
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1 Department of Human Biology, University of Cape Town, South Africa
* To whom correspondence should be addressed. Thirst is regulated by a complex interaction of signalling pathways within the central nervous system including components of the renin-angiotensin (RAS) and kalikrein kinin (KKS) 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 226km 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 (
Received July 12, 2006
Revised August 17, 2006
Accepted August 24, 2006
Article
Dipsogenic genes associated with weight changes during ironman triathlons
Colleen J. Saunders 1, Liesl de Milander 1, Tamara Hew-Butler 1, Stavroulla L. Xenophontos 2, Marios A. Cariolou 2, Lakis C. Anastassiades 3, Timothy D. Noakes 1, and Malcolm Collins 4 *
2 Molecular Genetics Department B & Laboratory of Forensic Genetics, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
3 Cardiovascular Diagnostic Centre, Nicosia, Cyprus
4 Medical Research Council of South Africa; Department of Human Biology, University of Cape Town, South Africa; UCT/MRC Research Unit for Exercise Science and Sports Medicine, P.O. Box 115, Newlands 7725, South Africa
Malcolm Collins, E-mail: mcollins{at}sports.uct.ac.za
Abstract 
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.
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