Effects of the type 2 diabetes-associated PPARG P12A polymorphism on progression to diabetes and response to troglitazone.
BACKGROUND
The common P12A polymorphism in PPARG (a target for thiazolidinedione medications) has been consistently associated with type 2 diabetes.


OBJECTIVE
We examined whether PPARG P12A affects progression from impaired glucose tolerance to diabetes, or responses to preventive interventions (lifestyle, metformin, or troglitazone vs. placebo).


METHODS
This study included 3548 Diabetes Prevention Program participants.


METHODS
We performed Cox regression analysis using genotype at PPARG P12A, intervention, and their interactions as predictors of diabetes incidence. We also genotyped five other PPARG variants implicated in the response to troglitazone and assessed their effect on insulin sensitivity at 1 yr.


RESULTS
Consistent with prior cross-sectional studies, P/P homozygotes at PPARG P12A appeared more likely to develop diabetes than alanine carriers (hazard ratio, 1.24; 95% confidence interval, 0.99-1.57; P=0.07) with no interaction of genotype with intervention. There was a significant interaction of genotype with body mass index and waist circumference (P=0.03 and 0.002, respectively) with the alanine allele conferring less protection in more obese individuals. Neither PPARG P12A nor five other variants significantly affected the impact of troglitazone on insulin sensitivity in 340 participants at 1 yr.


CONCLUSIONS
The proline allele at PPARG P12A increases risk for diabetes in persons with impaired glucose tolerance, an effect modified by body mass index. In addition, PPARG P12A has little or no effect on the beneficial response to troglitazone.
Florez
Jose C
JC
Center for Human Genetic Research and Department of Medicine, Massachusetts General Hospital, and Harvard Medical School, Boston 02114, USA. jcflorez@partners.org
Jablonski
Kathleen A
KA
Sun
Maria W
MW
Bayley
Nick
N
Kahn
Steven E
SE
Shamoon
Harry
H
Hamman
Richard F
RF
Knowler
William C
WC
Nathan
David M
DM
Altshuler
David
D
D019943:Amino Acid Substitution; D002839:Chromans / Q000627:therapeutic use*; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy / Q000235:genetics* / Q000503:physiopathology / Q000523:psychology; D018450:Disease Progression; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use*; D008019:Life Style; D008687:Metformin / Q000627:therapeutic use; D047495:PPAR gamma / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D045162:Thiazolidinediones / Q000627:therapeutic use*; D000077288:Troglitazone
D002839:Chromans; D007004:Hypoglycemic Agents; D047495:PPAR gamma; D045162:Thiazolidinediones; D008687:Metformin; D000077288:Troglitazone