The combination of UCP3–55CT and PPARγ2Pro12Ala polymorphisms affects BMI and substrate oxidation in two diabetic populations

• UCP3 and PPARγ2 gene polymorphism modulate BMI with additive effects.
• The finding was replicated in two different populations supporting the independence of the finding from environmental factors.
• A differential impact on substrate oxidation is one likely mechanism linking these genetic traits with body weight.

Background and AimTo evaluate the combined contribution of UCP3–55CT and PPARγ2 Pro12Ala polymorphisms as correlates of BMI, energy expenditure (REE) and substrate oxidation in people with type 2 diabetes.Methods and ResultsTwo independent population with type 2 diabetes were studied: population A, n = 272; population B, n = 269. Based on both UCP3 and PPARγ2 genotypes three groups were created. Carriers of the PPARγ2 Pro12Ala in combination with the CC genotype of UCP3 (ProAla/CC, group 1); carriers of only one of these genotypes (either CC/ProPro or CT-TT/ProAla, group 2); people with neither variants (CT-TT/ProPro, group 3). In both populations BMI (kg/m2) was highest in group 1, intermediate in group 2 and lowest in group 3, independent of energy intake (i.e 35.3 ± 6.7 vs 33.4 ± 5.4 vs 31.8 ± 3, p < 0.02, population A; 32.4 ± 4.2 vs 31.7 ± 3.8 vs 30.1 ± 2.7; p < 0.03, population B). People with the ProAla/CC genotype (group 1) showed similar REE, but lower lipid oxidation (10.9 vs 13.9 g/kg fat free mass/day; p = 0.04) and higher carbohydrate oxidation (23.6 vs 15.6 g/kg fat free mass/day; p = 0.02) than carriers of other genotypes.ConclusionsThe combination of UCP3–55 CC and PPARγ2 Pro12Ala genotypes is associated with significantly higher BMI than other PPARγ2-UCP3 genotype combinations, partly due to a reduced ability in lipids oxidation. The relative importance of these mechanism(s) may be different in non diabetic people.