Interactions of the PPARγ2 polymorphism with fat intake affecting energy metabolism and nutritional outcomes in obese women

Background/aims: To determine the influence of the Pro12Ala polymorphism of the PPARγ2 gene and the dietary lipid intake on energy metabolism and nutritional outcomes in obese women after an acute fat load or following a low-calorie diet for 10 weeks.

Methods: Sixty obese women (aged 30-46 years) participated in the study and were assigned to 2 groups depending on the genotype: Pro12Pro and Pro12Ala/Ala12Ala carriers. At baseline and after 2 nutritional (short- or long-term) interventions, measurement of anthropometrical and body composition (bioelectrical impedance) variables, dietary assessments, energy metabolism (indirect calorimetry) measurements as well as biochemical and molecular (PPARγ2 genotype) analyses were performed. All women received a high-fat test meal to determine the postprandial metabolism (short term) and an energy-restricted diet for 10 weeks (long term).

Results: The frequencies of the Pro12Pro and Pro12Ala/Ala12Ala genotypes were 83.33 and 16.67%, respectively, and reached Hardy-Weinberg equilibrium. Interestingly, the postprandial energy expenditure after the fat load was higher in subjects carrying the Ala allele. At baseline, the habitual monounsaturated fatty acid (MUFA) intake inversely correlated with fat oxidation and body mass index in the obese Pro12Ala/Ala12Ala carriers, while a lower PUFA intake (%) in the long-term trial was associated with an increase in the respiratory quotient only in Ala carriers but not in the Pro12Pro genotyped group.

Conclusions: The Pro12Ala polymorphism in the PPARγ2 gene influenced energy metabolism in the assayed short- and long-term situations since the response to both nutritional interventions differed according to the genotype. The results suggest that fat oxidation and energy expenditure may be lower in Pro12Pro carriers compared to Pro12Ala/Ala12Ala genotypes, while in obese women with Pro12Ala/Ala12Ala polymorphisms in the PPARγ2 gene fat oxidation was negatively correlated with the MUFA and PUFA (%) intake.