Effect of -55CT Polymorphism of UCP3 on Insulin Resistance and Cardiovascular Risk Factors after a High Protein/Low Carbohydrate versus a Standard Hypocaloric Diet

BACKGROUND: The C/C genotype of a polymorphism in the uncoupling protein3 (UCP3) promoter (-55C->T) (rs1800849) is associated with an increased body mass index. OBJECTIVE: The aim of our study was to investigate the effect of polymorphism on the UCP3 promoter (-55C->T) on insulin resistance and cardiovascular risk factors secondary to a high protein/low carbohydrate vs. a standard hypocaloric diets (1,000 kcal/day). DESIGN: A population of 283 obese subjects was analyzed in a randomized trial. A nutritional evaluation was performed at the beginning and at the end of a 9-month period in which subjects received 1 of 2 diets (diet HP: high protein/low carbohydrate vs. diet S: standard diet). RESULTS: Weight improvement was higher in non-T carriers. With both diets and only in wild genotype (diet HP vs. diet S), total cholesterol (-9.7 ± 4.0 vs. -11.1 ± 2.0 mg/dl; p > 0.05) and low density lipoprotein (LDL) cholesterol (-8.3 ± 3.0 vs. -5.5 ± 2.7 mg/dl; p > 0.05) decreased. The improvement in these parameters was similar in subjects with diet HP than HS. With diet HP and only in wild genotype, glucose (-5.2 ± 2.2 mg/dl; p < 0.05), triglycerides (-15.5 ± 3.9 mg/dl; p < 0.05), insulin levels (-3.9 ± 3.1 UI/l; p < 0.05) and homeostasis model assessment (HOMA-R; -0.6 ± 0.1 units; p < 0.05) decreased. CONCLUSION: Carriers of T allele have a different response than non-carrier subjects, with a lack of decrease of LDL cholesterol, glucose, insulin levels and HOMA-R. The weight loss was lower in T carriers. HP diet showed a better metabolic response than S diet in 55CC homozygous.