Haplotype analysis of the PPARgamma Pro12Ala and C1431T variants reveals opposing associations with body weight.
BACKGROUND
Variation at the PPARG locus may influence susceptibility to type 2 diabetes and related traits. The Pro12Ala polymorphism may modulate receptor activity and is associated with protection from type 2 diabetes. However, there have been inconsistent reports of its association with obesity. The silent C1431T polymorphism has not been as extensively studied, but the rare T allele has also been inconsistently linked to increases in weight. Both rare alleles are in linkage disequilibrium and the independent associations of these two polymorphisms have not been addressed.


RESULTS
We have genotyped a large population with type 2 diabetes (n = 1107), two populations of non-diabetics from Glasgow (n = 186) and Dundee (n = 254) and also a healthy group undergoing physical training (n = 148) and investigated the association of genotype with body mass index. This analysis has demonstrated that the Ala12 and T1431 alleles are present together in approximately 70% of the carriers. By considering the other 30% of individuals with haplotypes that only carry one of these polymorphisms, we have demonstrated that the Ala12 allele is consistently associated with a lower BMI, whilst the T1431 allele is consistently associated with higher BMI.


CONCLUSIONS
This study has therefore revealed an opposing interaction of these polymorphisms, which may help to explain previous inconsistencies in the association of PPARG polymorphisms and body weight.
Doney
Alex
A
Biomedical Research Centre, Ninewells Hospital and Medical School, University of Dundee, Dundee, DD1 9SY, Scotland, United Kingdom. alex.doney@tuht.scot.nhs.uk
Fischer
Bettina
B
Frew
David
D
Cumming
Alastair
A
Flavell
David M
DM
World
Michael
M
Montgomery
Hugh E
HE
Boyle
Douglas
D
Morris
Andrew
A
Palmer
Colin N A
CN
D000328:Adult; D000409:Alanine / Q000235:genetics* / Q000502:physiology; D019943:Amino Acid Substitution / Q000235:genetics / Q000502:physiology; D015992:Body Mass Index; D001835:Body Weight / Q000235:genetics* / Q000502:physiology; D003596:Cytosine / Q000378:metabolism* / Q000502:physiology; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics; D015444:Exercise / Q000502:physiology; D005260:Female; D006580:Genetic Carrier Screening / Q000379:methods; D005820:Genetic Testing / Q000379:methods; D014644:Genetic Variation / Q000235:genetics*; D005838:Genotype; D006239:Haplotypes / Q000235:genetics* / Q000502:physiology; D006801:Humans; D015810:Linkage Disequilibrium / Q000235:genetics; D008297:Male; D011110:Polymorphism, Genetic / Q000235:genetics / Q000502:physiology; D011392:Proline / Q000235:genetics*; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics* / Q000502:physiology; D012044:Regression Analysis; D013941:Thymine / Q000378:metabolism* / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology
D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D003596:Cytosine; D011392:Proline; D000409:Alanine; D013941:Thymine