UCP2 I/D modulated change in BMI during a lifestyle modification intervention study in Japanese subjects

Association of 45-bp ins/del polymorphism of uncoupling protein 2 (UCP2) and susceptibility to nonalcoholic fatty liver and type 2 diabetes mellitus in North-west of Iran

OBJECTIVE

Uncoupling protein 2 (UCP2) plays a crucial role in energy homeostasis via insulin secretion regulation, free fatty acid concentrations, and lipid metabolism. This study aimed to investigate the association of 45-bp ins/del polymorphism of UCP2 with susceptibility to NAFLD (Non-Alcoholic Fatty Liver Disease) and T2DM (Type 2 Diabetes Mellitus). DNA was extracted from the white blood cells of the subjects, and the gene polymorphism was determined using polymerase chain reaction (PCR). In this study, 72 patients with NAFLD, 71 healthy individuals as control, 80 patients with T2DM, and 77 healthy controls were enrolled in the study.

RESULTS

A higher prevalence of insertion/insertion genotype was observed in T2DM patients compared to the controls (p- value˂ 0.05). There was no difference in genotype distribution between NAFLD patients and controls (p-value > 0.05). NAFLD patients with D/D, D/I genotype had higher triglyceride, ALT, and AST levels; however, their HDL levels were lower than healthy controls. Patients with T2DM with D/D or D/I genotype also had significantly higher fasting serum glucose (FSG). While we found an association between the 45 bp I/D polymorphism in 3'UTR of UCP2 and T2DM, no correlation between this polymorphism and NAFLD was identified.

-866G/A and Ins/Del polymorphisms in UCP2 gene are associated with reduced short-term weight loss in patients who underwent Roux-en-Y gastric bypass

BACKGROUND

Uncoupling protein 2 (UCP2) plays an important role in energy expenditure regulation. Previous studies have associated the common -866G/A (rs659366) and Ins/Del polymorphisms in the UCP2 gene with metabolic and obesity-related phenotypes. However, it is still unclear whether these polymorphisms influence weight loss after bariatric surgery.

OBJECTIVES

To investigate whether UCP2 -866G/A and Ins/Del polymorphisms are associated with weight loss outcomes after bariatric surgery.

SETTING

Longitudinal study in a university hospital.

METHODS

We retrospectively evaluated 186 patients who underwent Roux-en-Y gastric bypass (RYGB) surgery for clinical and laboratory characteristics in the preoperative period, 6, 12, and 18 months after RYGB. The -866G/A (rs659366) polymorphism was genotyped using real-time PCR, while the Ins/Del polymorphism was genotyped by direct separation of PCR products in 2.5% agarose gels.

RESULTS

Patients with the -866A/A genotype showed higher body mass index (BMI) after 6, 12, and 18 months of surgery and excess body weight after 6 and 12 months compared with G/G patients. They also showed lower excess weight loss (EWL%) after 6 and 12 months of surgery. Ins allele carriers (Ins/Ins + Ins/Del) had lower delta (Δ) BMI 12 months after surgery compared with Del/Del patients. Accordingly, patients carrying haplotypes with ≥2 risk alleles of these polymorphisms had higher BMI and excess weight and lower EWL% during follow-up.

CONCLUSION

UCP2 -866A/A genotype is associated with higher BMI and excess weight and lower EWL% during an 18-month follow-up of patients who underwent RYGB, while the Ins allele seems to be associated with lower ΔBMI 12 months after surgery. Further studies are needed to confirm the associations of the -866G/A and Ins/Del polymorphisms with weight loss after bariatric surgery.

The interaction between energy intake, physical activity and UCP2 -866G/A gene variation on weight gain and changes in adiposity: an Indonesian Nutrigenetic Cohort (INDOGENIC)

The present study aimed to investigate an interaction between energy intake, physical activity and UCP2 gene variation on weight gain and adiposity changes in Indonesian adults. This is a prospective cohort study conducted in 323 healthy adults living in the city of Yogyakarta, Indonesia. Energy intake, physical activity, body weight, BMI, percentage body fat and waist:hip ratio (WHR) were measured at baseline and after 2 years while UCP2 -866G/A gene variation was determined at baseline. We reported that after 2 years subjects had a significant increment in body weight, BMI, body fat and reduction in WHR (all P < 0·05). In all subjects, total energy intake was significantly correlated with changes in body weight (β = 0·128, P = 0·023) and body fat (β = 0·123, P = 0·030). Among subjects with the GG genotype, changes in energy intake were positively correlated with changes in body weight (β = 0·232, P = 0·016) and body fat (β = 0·201, P = 0·034). These correlations were insignificant among those with AA + GA genotypes (all P > 0·05). In summary, we show that UCP2 gene variation might influence the adiposity response towards changes in energy intake. Subjects with the GG genotype of UCP2 -866G/A gene were more responsive to energy intake, thus more prone to weight gain due to overeating.

Association of uncoupling protein (Ucp) gene polymorphisms with cardiometabolic diseases

The hereditary aspect of obesity is a major focus of modern medical genetics. The genetic background is known to determine a higher-than-average prevalence of obesity in certain regions, like Oceania. There is evidence that dysfunction of brown adipose tissue (BAT) may be a risk factor for obesity and type 2 diabetes (T2D). A significant number of studies in the field focus on the UCP family. The Ucp genes code for electron transport carriers. UCP1 (thermogenin) is the most abundant protein of the UCP superfamily and is expressed in BAT, contributing to its capability of generating heat. Single nucleotide polymorphisms (SNPs) of Ucp1-Ucp3 were recently associated with risk of cardiometabolic diseases. This review covers the main Ucp SNPs A-3826G, A-1766G, A-112C, Met229Leu, Ala64Thr (Ucp1), Ala55Val, G-866A (Ucp2), and C-55 T (Ucp3), which may be associated with the development of obesity, disturbance in lipid metabolism, T2D, and cardiovascular diseases.

Polymorphisms in the Uncoupling Protein 2 Gene Are Associated with Diabetic Retinopathy in Han Chinese Patients with Type 2 Diabetes

BACKGROUND

The uncoupling protein 2 (UCP2) gene plays an important role in the complications of type 2 diabetes (T2D). However, the association between variants in the UCP2 gene and diabetic retinopathy (DR) in Han Chinese T2D patients remains unclear.

METHODS

Two single-nucleotide polymorphisms (SNPs) [rs659366 (-866G/A) and a 45-bp insertion/deletion (I/D) in the 3'-UTR] in the UCP2 gene were genotyped in a study cohort of 209 T2D patients with DR and 199 T2D patients without DR by direct DNA sequencing.

RESULTS

Logistic regression analysis showed that the AA and GA genotypes of rs659366 were significantly associated with an increased risk for nonproliferative DR (NPDR) in the codominant model (corrected p-value <0.01) and the dominant model (corrected p-value = 0.006). Patients harboring the II and DI genotypes had a higher risk for PDR in the codominant model (corrected p-value = 0.011) and the dominant model (corrected p-value = 0.006), and the DI genotype showed a higher risk for NPDR in the dominant model (corrected p-value = 0.007) or codominant model (corrected p-value = 0.006). Further, haplotype analyses verified that the A-I haplotype is a risk haplotype for NPDR and PDR.

CONCLUSION

This study suggests that the UCP2 gene may be involved in the pathogenesis of NPDR and PDR in Han Chinese patients with T2D.

The Ala55Val and -866G>A polymorphisms of the UCP2 gene could be biomarkers for weight loss in patients who had Roux-en-Y gastric bypass

OBJECTIVE

The aim of this study was to investigate whether the Ala55Val and -866G>A polymorphisms of the UCP2 gene are related to weight loss and changes in body composition after bariatric surgery performed by Roux-en-Y gastric bypass (RYGB).

METHODS

This longitudinal study enrolled obese patients submitted to RYGB. Data regarding weight (kg), body mass index (kg/m²), fat-free mass (FFM; kg), fat mass (kg), weight loss (kg and %), and percent excess weight loss were collected from both preoperative and 1-y postoperative medical records. Polymorphisms were genotyped by allelic discrimination using real-time polymerase chain reaction and TaqMan-predesigned single nucleotide polymorphism Genotyping Assay kits (Applied Biosystems, Foster City, CA, USA). The t test was used to compare variables between genotypes of each polymorphism to analyze the dominant and recessive models. Linear regression models were used to adjust the effects of initial weight, age, and sex on the variation of weight and body composition (P < 0.05).

RESULTS

We analyzed 150 severely obese individuals (age 47.2 ± 10.5 y; 80% women). Genotype analysis showed a greater prevalence of heterozygous GA (41.3%) for -866G>A polymorphism and CT (39.3%) for Ala55Val polymorphism. Individuals who carried the T (CT+TT) and A (GA+AA) mutated alleles for Ala55Val and -866G>A, respectively, showed a higher weight and FFM loss.

CONCLUSION

The mutated alleles T for Ala55Val and A for -866G>A polymorphism could be biomarkers of weight loss 1 y after RYGB.