Effects of UCP2 and UCP3 variants on the manifestation of overweight in Korean children

Solute Carrier Transporters as Potential Targets for the Treatment of Metabolic Disease

The solute carrier (SLC) superfamily comprises more than 400 transport proteins mediating the influx and efflux of substances such as ions, nucleotides, and sugars across biological membranes. Over 80 SLC transporters have been linked to human diseases, including obesity and type 2 diabetes (T2D). This observation highlights the importance of SLCs for human (patho)physiology. Yet, only a small number of SLC proteins are validated drug targets. The most recent drug class approved for the treatment of T2D targets sodium-glucose cotransporter 2, product of the SLC5A2 gene. There is great interest in identifying other SLC transporters as potential targets for the treatment of metabolic diseases. Finding better treatments will prove essential in future years, given the enormous personal and socioeconomic burden posed by more than 500 million patients with T2D by 2040 worldwide. In this review, we summarize the evidence for SLC transporters as target structures in metabolic disease. To this end, we identified SLC13A5/sodium-coupled citrate transporter, and recent proof-of-concept studies confirm its therapeutic potential in T2D and nonalcoholic fatty liver disease. Further SLC transporters were linked in multiple genome-wide association studies to T2D or related metabolic disorders. In addition to presenting better-characterized potential therapeutic targets, we discuss the likely unnoticed link between other SLC transporters and metabolic disease. Recognition of their potential may promote research on these proteins for future medical management of human metabolic diseases such as obesity, fatty liver disease, and T2D. SIGNIFICANCE STATEMENT: Given the fact that the prevalence of human metabolic diseases such as obesity and type 2 diabetes has dramatically risen, pharmacological intervention will be a key future approach to managing their burden and reducing mortality. In this review, we present the evidence for solute carrier (SLC) genes associated with human metabolic diseases and discuss the potential of SLC transporters as therapeutic target structures.

Association between UCP polymorphisms and adipokines with obesity in Mexican adolescents

BACKGROUND

It has been reported that the uncoupling proteins (UCPs) can contribute to energy metabolism, and are thus involved in the pathogenesis of obesity. The objective of the study was to analyze the association between UCP polymorphisms, clinical parameters and leptin and adiponectin plasma levels in an adolescent population with overweight and obesity.

METHODS

We analyzed the UCP1 -3826 C/T, UCP2-866 G/A, Ala55Val and UCP3 -55 C/T polymorphisms and the levels of adipokines in adolescents with normal weight and with overweight or obesity. The study included 270 students aged between 12 and 18 years categorized according to the percentiles from Mexico City. Adipokines levels were measured by immunoassay methods and the UCP polymorphisms were determined using Taqman real-time polymerase chain reaction (RT-PCR).

RESULTS

No significant differences were found in the UCP polymorphisms in seven inheritance models studied. Most of the significant differences in the clinical parameters were found under a recessive model, the UCP2 -866 polymorphism was associated with diastolic blood pressure (p=0.008), triglycerides (p=0.045), low-density lipoprotein-cholesterol (LDL-C) (p=0.003), high-density lipoprotein-cholesterol (HDL-C) (p=0.050) and plasma levels of leptin (p<0.001). Also, the obese group was found to have higher leptin levels and lower adiponectin levels in GA+AA vs. GG (recessive model).

CONCLUSIONS

This study demonstrated a direct relationship between the clinical characteristics and UCP2-866 in a recessive model, associated with high levels of leptin and decreased levels of adiponectin in an obese or overweight Mexican adolescent population.

Association between gene polymorphisms and obesity and physical fitness in Korean children

Obesity is affected by genetic factors and environmental influences. This research was undertaken to identify single nucleotide polymorphisms (SNPs) related to obesity and physical fitness and then to analyse and compare interactions between physical fitness and obesity-associated genotypes. To investigate relationships between physical fitness and major SNPs previously reported to be related to obesity, 68 SNPs in 32 genes were genotyped in 71 Korean children. Tests were conducted to evaluate five elements of physical fitness (speed, aerobic endurance, muscular endurance, muscular strength, and flexibility). The results obtained showed significant (P<0.02) differences in physical fitness scores for the following genotypes: CNR1 (rs1049353; GG), LEP (rs7799039; AA+AG), HHEX (rs1111875; TT), GC (rs16847015; TG+GG), LRP5 (rs4988300; GG+GT), NPY2R (rs2880415; CT+CC), PPY (rs231472; GG), UCP2 (rs660339; CT+TT), CDKN2B (rs10811661; AA+AG), and ADIPOQ (rs266729; CG+GG). Ten physical fitness-related genotypes were newly identified during the present study. This study suggests that classification of genotypes by physical fitness level could be used as an index for predicting the risk of obesity and for selecting individuals for intervention programmes. Furthermore, the study shows that even children participating in the same physical fitness improvement programme can exhibit different genotype dependencies.

Role of the Polymorphisms of Uncoupling Protein Genes in Childhood Obesity and Their Association with Obesity-Related Disturbances

BACKGROUND

Obesity, one of the most common disorders observed in clinical practice, has been associated with energy metabolism-related protein genes such as uncoupling proteins (UCPs). Herein, we evaluated UCPs as candidate genes for obesity and its morbidities.

METHODS

A total of 268 obese and 185 nonobese children and adolescents were enrolled in this study. To determine dyslipidemia, hypertension, and insulin resistance, laboratory tests were derived from fasting blood samples. UCP1-3826 A/G, UCP2 exon 8 deletion/insertion (del/ins), and UCP3-55C/T variants were also genotyped, and the relationships among the polymorphisms of these UCPs and obesity morbidities were investigated.

RESULTS

The mean ages of the obese and control groups were 11.61 ± 2.83 and 10.74 ± 3.36 years, respectively. The respective genotypic frequencies of the AA, AG, and GG genotypes of UCP1 were 46.3%, 33.2%, and 20.5% in obese subjects and 46.5%, 42.2%, and 11.4% in the controls (p = 0.020). G alleles were more frequent in obese subjects with hypertriglyceridemia (42.9%; p = 0.048) than in those without, and the GG genotype presented an odds ratio for obesity of 2.02 (1.17-3.47; p = 0.010). The polymorphisms of UCP2 exon 8 del/ins and UCP3-55C/T did not influence obesity risk (p > 0.05). The I (ins) allele was associated with low HDL cholesterolemia (p = 0.023).

CONCLUSION

The GG genotype of the UCP1-3826 A/G polymorphism appears to contribute to the onset of childhood obesity in Turkish children. The GG genotype of UCP1, together with the del/del genotype of the UCP2 polymorphism, may increase the risk of obesity with synergistic effects. The ins allele of the UCP2 exon 8 del/ins polymorphism may contribute to low HDL cholesterolemia.

The Gene-Lifestyle Interaction on Leptin Sensitivity and Lipid Metabolism in Adults: A Population Based Study

Background: Obesity has been associated with leptin resistance and this might be caused by genetic factors. The aim of this study was to investigate the gene-lifestyle interaction between −866G/A UCP2 (uncoupling protein 2) gene polymorphism, dietary intake and leptin in a population based study. Methods: This is a cross sectional study conducted in adults living at urban area of Yogyakarta, Indonesia. Data of adiposity, lifestyle, triglyceride, high density lipoprotein (HDL) cholesterol, leptin and UCP2 gene polymorphism were obtained in 380 men and female adults. Results: UCP2 gene polymorphism was not significantly associated with adiposity, leptin, triglyceride, HDL cholesterol, dietary intake and physical activity (all p > 0.05). Leptin was lower in overweight subjects with AA + GA genotypes than those with GG genotype counterparts (p = 0.029). In subjects with AA + GA genotypes there was a negative correlation between leptin concentration (r = −0.324; p < 0.0001) and total energy intake and this correlation was not seen in GG genotype (r = −0.111; p = 0.188). Conclusions: In summary, we showed how genetic variation in −866G/A UCP2 affected individual response to leptin production. AA + GA genotype had a better leptin sensitivity shown by its response in dietary intake and body mass index (BMI) and this explained the protective effect of A allele to obesity.

Examining for an association between candidate gene polymorphisms in the metabolic syndrome components on excess weight and adiposity measures in youth: a cross-sectional study

Background

A polymorphism in a gene may exert its effects on multiple phenotypes. The aim of this study is to explore the association of 10 metabolic syndrome candidate genes with excess weight and adiposity and evaluate the effect of perinatal and socioeconomic factors on these associations.

Methods

The anthropometry, socioeconomic and perinatal conditions and 10 polymorphisms were evaluated in 1081 young people between 10 and 18 years old. Genotypic associations were calculated using logistic and linear models adjusted by age, gender, and pubertal maturation, and a genetic risk score (GRS) was calculated by summing the number of effect alleles.

Results

We found that AGT-rs699 and the IRS2-rs1805097 variants were significantly associated with excess weight, OR = 1.25 (CI 95% 1.01–1.54; p = 0.034); OR = 0.77 (CI 95% 0.62–0.96; p = 0.022), respectively. AGT-rs699 and FTO-rs17817449 variants were significantly and directly associated with body mass index (BMI) (p = 0.036 and p = 0.031), while IRS2-rs1805097 and UCP3-rs1800849 were significantly and negatively associated with BMI and waist circumference, correspondingly. Each additional effect allele in GRS was associated with an increase of 0.020 log(BMI) (p = 0.004). No effects from the socioeconomic and perinatal factors evaluated on the association of the candidate genes with the phenotypes were detected.

Conclusions

Our observation suggests that AGT-rs699 and FTO-rs17817449 variants may contribute to the risk development of excess weight and an increase in the BMI, while IRS2-rs1805097 showed a protector effect; in addition, UCP3- rs1800849 showed a decreasing waist circumference. Socioeconomic and perinatal factors had no effect on the associations of the candidate gene.

Electronic supplementary material

The online version of this article (doi:10.1186/s12263-017-0567-1) contains supplementary material, which is available to authorized users.

Effects of energy expenditure gene polymorphisms on obesity-related traits in obese children

OBJECTIVE

To assess the frequencies of common polymorphisms of genes associated with energy expenditure among Hungarian obese children and investigate their influences on obesity-related traits and metabolic complications of common childhood obesity.

RESEARCH METHODS AND PROCEDURES

In a total of 528 obese children (age 13.2±2.6 years) an oral glucose tolerance test and determination of fasting serum lipid levels were carried out, blood pressure and resting energy expenditure were measured and the children were genotyped for the following gene polymorphisms: Trp64Arg of β3-adrenoreceptor (ADRB3), -3826 A/G of uncoupling protein (UCP)-1, exon 8 45 bp del/ins and -866 G/A of UCP-2, -55 C/T of UCP-3, and Pro12Ala of peroxisome-proliferator activated receptor gamma-2.

RESULTS

Carriers of the ADRB3 Arg64 allele had a significantly higher relative body weight and relative body mass index compared with non-carriers. The UCP-2 exon 8 del/ins polymorphism was associated with higher degree of obesity, insulin resistance, dyslipideamia and lower adjusted metabolic rate. Children with UCP-3 -55 T/T genotype had a significantly lower adjusted metabolic rate than the C allele carriers.

CONCLUSION

We found evidence for associations between common polymorphisms of the ADRB3, the UCP-2 and UCP-3 genes and basic metabolic rate as well as level and metabolic consequences of common obesity among Hungarian school-aged children.

Meta-analysis reveals the association of common variants in the uncoupling protein (UCP) 1-3 genes with body mass index variability

Background

The relationship between uncoupling protein (UCP) 1–3 polymorphisms and susceptibility to obesity has been investigated in several genetic studies. However, the impact of these polymorphisms on obesity is still under debate, with contradictory results being reported. Until this date, no meta-analysis evaluated the association of UCP polymorphisms with body mass index (BMI) variability. Thus, this paper describe a meta-analysis conducted to evaluate if the -3826A/G (UCP1); -866G/A, Ala55Val and Ins/Del (UCP2) and -55C/T (UCP3) polymorphisms are associated with BMI changes.

Methods

A literature search was run to identify all studies that investigated associations between UCP1-3 polymorphisms and BMI. Weighted mean differences (WMD) were calculated for different inheritance models.

Results

Fifty-six studies were eligible for inclusion in the meta-analysis. Meta-analysis results showed that UCP2 55Val/Val genotype was associated with increased BMI in Europeans [Random Effect Model (REM) WMD 0.81, 95% CI 0.20, 1.41]. Moreover, the UCP2 Ins allele and UCP3-55T/T genotype were associated with increased BMI in Asians [REM WMD 0.46, 95% CI 0.09, 0.83 and Fixed Effect Model (FEM) WMD 1.63, 95% CI 0.25, 3.01]. However, a decreased BMI mean was observed for the UCP2-866 A allele in Europeans under a dominant model of inheritance (REM WMD −0.18, 95% CI −0.35, −0.01). There was no significant association of the UCP1-3826A/G polymorphism with BMI mean differences.

Conclusions

The meta-analysis detected a significant association between the UCP2-866G/A, Ins/Del, Ala55Val and UCP3-55C/T polymorphisms and BMI mean differences.

The energy intake modulates the association of the -55CT polymorphism of UCP3 with body weight in type 2 diabetic patients

BACKGROUND

Previous association studies of the -55CT polymorphism of the uncoupling protein 3 (UCP3) gene with body mass index (BMI) have provided inconsistent results. The study aim is twofold: (1) to evaluate the association of the -55CT polymorphism of UCP3 with BMI in two independent populations to verify the reproducibility of the finding; (2) to evaluate whether this association is modulated by energy intake.

METHODS

Study participants are 736 males and females with type 2 diabetes belonging to independent populations (N=394 population 1; N=342 population 2). Anthropometry and laboratory parameters were measured; in population 2, energy intake and physical exercise were also assessed.

RESULTS

The -55CT polymorphism was associated with a significantly lower BMI in population 1 (27.8±3.9 vs 28.9±4.6 kg m(-2); P<0.02), the finding was confirmed in population 2 (that is, 30.3±6.0 vs 32.1±5.9 kg m(-2); P<0.01) independent of gender, age, HbA1c, use of drugs and energy intake. To evaluate the role of diet in population 2, the study participants were stratified by genotype and tertiles of energy intake. In both genotype groups, BMI increased with increasing caloric intake with a significant trend (P<0.001), the BMI difference between the two genotype groups was large and statistically significant in the lower tertile (27.6 vs 31.2 kg m(-2); P<0.001), intermediate in the second tertile and negligible in the upper tertile (32.8 vs 32.9; kg m(-2); nonsignificant). The multivariate regression analysis confirmed a significant interaction between genotype and energy intake as correlates of BMI independent of age, gender, glucose control, physical activity and medications for diabetes (P=0.004).

CONCLUSIONS

The study replicates in two independent populations the association between the -55CT polymorphism of UCP3 and a lower BMI. This association was modulated by energy intake, thus suggesting that the unmeasured effect of diet may partly account for inconsistencies of prior association studies.

Bioenergetics in human evolution and disease: implications for the origins of biological complexity and the missing genetic variation of common diseases

Two major inconsistencies exist in the current neo-Darwinian evolutionary theory that random chromosomal mutations acted on by natural selection generate new species. First, natural selection does not require the evolution of ever increasing complexity, yet this is the hallmark of biology. Second, human chromosomal DNA sequence variation is predominantly either neutral or deleterious and is insufficient to provide the variation required for speciation or for predilection to common diseases. Complexity is explained by the continuous flow of energy through the biosphere that drives the accumulation of nucleic acids and information. Information then encodes complex forms. In animals, energy flow is primarily mediated by mitochondria whose maternally inherited mitochondrial DNA (mtDNA) codes for key genes for energy metabolism. In mammals, the mtDNA has a very high mutation rate, but the deleterious mutations are removed by an ovarian selection system. Hence, new mutations that subtly alter energy metabolism are continuously introduced into the species, permitting adaptation to regional differences in energy environments. Therefore, the most phenotypically significant gene variants arise in the mtDNA, are regional, and permit animals to occupy peripheral energy environments where rarer nuclear DNA (nDNA) variants can accumulate, leading to speciation. The neutralist-selectionist debate is then a consequence of mammals having two different evolutionary strategies: a fast mtDNA strategy for intra-specific radiation and a slow nDNA strategy for speciation. Furthermore, the missing genetic variation for common human diseases is primarily mtDNA variation plus regional nDNA variants, both of which have been missed by large, inter-population association studies.

Uncoupling protein-2 gene polymorphisms are associated with obesity in Hungarian children

AIM

To determine the frequency of common polymorphisms of genes associated with energy metabolism among normal weight and overweight/obese children to look for effects on childhood obesity.

METHODS

Among 709 overweight/obese and 637 normal weight children (age 6-17 years), anthropometric measurements were carried out and genotyping for the following gene polymorphisms: β3 -adrenoreceptor Trp64Arg, uncoupling protein (UCP) -1 -3826 A/G, UCP-2 -866 G/A and exon 8 del/ins, UCP-3 -55 C/T and peroxisome proliferator-activated receptor-γ Pro12Ala.

RESULTS

On multivariate regression analysis adjusted for age and gender heterozygosity and homozygosity for the UCP-2 -866 A variant was associated with an odds ratio (OR) for obesity of 0.69 (95% CI: 0.52-0.92; p = 0.013) and 0.50 (95% CI: 0.32-0.79; p = 0.003), respectively, compared with G/G homozygotes. Heterozygotes and homozygotes for the UCP-2 exon 8 ins allele had an OR for obesity of 1.66 (95% CI: 1.24-2.23; p = 0.001) and 2.12 (95% CI: 1.23-3.63; p = 0.006), respectively, compared with del/del homozygotes. There were no significant differences in obesity risk in association with the other examined gene polymorphisms.

CONCLUSION

Common polymorphisms of the UCP-2 gene might influence the propensity to overweight/obesity in Hungarian children.

UCP2 -866G/A, Ala55Val and UCP3 -55C/T polymorphisms in association with obesity susceptibility - a meta-analysis study

AIMS/HYPOTHESIS

Variants of UCP2 and UCP3 genes have been reported to be associated with obesity, but the available data on the relationship are inconsistent. A meta-analysis was performed to determine whether there are any associations between the UCP2 -866G/A, Ala55Val, and UCP3 -55C/T polymorphisms and obesity susceptibility.

METHODS

The PubMed, Embase, Web of Science and CNKI, CBMdisc databases were searched for all relevant case-control studies. The fixed or random effect pooled measure was determined on the bias of heterogeneity test among studies. Publication bias was examined by the modified Begg's and Egger's test.

RESULTS

Twenty-two published articles with thirty-two outcomes were included in the meta-analysis: 12 studies with a total of 7,390 cases and 9,860 controls were analyzed for UCP2 -866G/A polymorphism with obesity, 9 studies with 1,483 cases and 2,067 controls for UCP2 Ala55Val and 8 studies with 2,180 cases and 2,514 controls for UCP3 -55C/T polymorphism. Using an additive model, the UCP2 -866G/A polymorphism showed no significant association with obesity risk in Asians (REM OR = 0.81, 95% CI: 0.65-1.01). In contrast, a statistically significant association was observed in subjects of European descent (FEM OR = 1.06, 95% CI: 1.01-1.12). But neither the UCP2 Ala55Val nor the UCP3 -55C/T polymorphism showed any significant association with obesity risk in either subjects of Asian (REM OR = 0.84, 95% CI: 0.67-1.06 for Ala55Val; REM OR = 0.94, 95% CI: 0.55-1.28 for -55C/T) or of European descent (REM OR = 1.04, 95% CI: 0.80-1.36 for Ala55Val; FEM OR = 1.08, 95% CI: 0.97-1.20 for -55C/T).

CONCLUSIONS AND INTERPRETATION

Our meta-analysis revealed that the UCP2 -866G/A polymorphism may be a risk factor for susceptibility to obesity in subjects of European descent, but not in individuals of Asian descent. And our results did not support the association between UCP2 Ala55Val, UCP3 -55C/T polymorphisms and obesity in the populations investigated. This conclusion warrants confirmation by further studies.

The role of uncoupling protein 2 and 3 genes polymorphism and energy expenditure in obese Indonesian children

AIM

Uncoupling protein (UCP) genes, which may contribute to energy metabolism in mitochondria, may be involved in the pathogenesis of obesity. We analyzed the differences in energy expenditure between single nucleotide polymorphisms (SNPs) UCP3-55C/T, UCP3 Y210Y, and UCP2 A55V among Indonesian children.

METHODS

The study included 76 schoolchildren (36 obese and 40 healthy; mean age, 12.8 years) in Semarang, Indonesia. Body composition was measured by bioelectrical impedance analysis; resting energy expenditure (REE) by indirect calorimetry; physical activity by uniaxial accelerometer; and total energy expenditure (TEE) by the equations extrapolated from REE and physical activity. UCP3-55C/T, UCP3 Y210Y, and UCP2 A55V were examined by restriction length fragment polymorphism analysis.

RESULTS

The TEE of the subjects with the T/T genotype at UCP3-55C/T after adjusting for fat-free mass (63.2±7.2 kcal/kg/day) and T/T at UCP2 A55V (62.8±5.6 kcal/kg/day) was lower than that of the subjects with the C/C and C/T genotypes (p<0.05). The REE of the subjects with these T/T genotypes tended to be lower than that of the subjects with C/C and C/T (p≥0.05). No significant differences in REE or TEE were found between the UCP3 Y210Y genotypes.

CONCLUSIONS

The subjects with the T/T genotypes of UCP3-55C/T or UCP2 A55V had lower TEE than those with other genotypes.

Differential Association of Uncoupling Protein 2 Polymorphisms with Pattern Identification among Korean Stroke Patients: A Diagnostic System in Traditional Korean Medicine

Uncoupling protein 2 (UCP2), a mitochondrial protein present in many organs and cell types, is known to dissipate the proton gradient formed by the electron transport chain. Its function is correlated with predictive parameters, such as obesity, diabetes, and metabolic syndromes. We analyzed the distribution of UCP2 polymorphisms in stroke patients diagnosed with one of the following four stroke subtypes based on the TKM standard pattern identification (PI): Qi-deficiency (QD), Dampness and Phlegm (D&P), Yin-deficiency (YD), and Fire and Heat (F&D). We studied a total of 1,786 stroke patients (397/QD, 645/D&P, 223/YD, and 522/F&D, 586/normal). Genotyping for the G-1957A, G-866A and A55V UCP2 polymorphisms was performed using the TaqMan. G-866A and A55V were significantly associated with the D&P and H&F subtypes. The frequency of subjects with the A allele of G-866A was significantly lower than the frequency of subjects with the GG type. The A55V polymorphism was also shown similar effect with G-866A in the dominant model. In contrast, no SNPs were shown to be associated with the QD or YD subtypes in this study. These results showed that the G-866A and A55V UCP2 polymorphisms may be genetic factors for specific PI types among Korean stroke patients.

Bioenergetic origins of complexity and disease

The organizing power of energy flow is hypothesized to be the origin of biological complexity and its decline the basis of "complex" diseases and aging. Energy flow through organic systems creates nucleic acids, which store information, and the annual accumulation of information generates today's complexity. Energy flow through our bodies is mediated by the mitochondria, symbiotic bacteria whose genomes encompass the mitochondrial DNA (mtDNA) and more than 1000 nuclear genes. Inherited and/or epigenomic variation of the mitochondrial genome determines our initial energetic capacity, but the age-related accumulation of somatic cell mtDNA mutations further erodes energy flow, leading to disease. This bioenergetic perspective on disease provides a unifying pathophysiological and genetic mechanism for neuropsychiatric diseases such as Alzheimer and Parkinson Disease, metabolic diseases such as diabetes and obesity, autoimmune diseases, aging, and cancer.

Genetic Variance in Uncoupling Protein 2 in Relation to Obesity, Type 2 Diabetes, and Related Metabolic Traits: Focus on the Functional -866G>A Promoter Variant (rs659366)

Uncoupling proteins (UCPs) are mitochondrial proteins able to dissipate the proton gradient of the inner mitochondrial membrane when activated. This decreases ATP-generation through oxidation of fuels and may theoretically decrease energy expenditure leading to obesity. Evidence from Ucp((-/-)) mice revealed a role of UCP2 in the pancreatic β-cell, because β-cells without UCP2 had increased glucose-stimulated insulin secretion. Thus, from being a candidate gene for obesity UCP2 became a valid candidate gene for type 2 diabetes mellitus. This prompted a series of studies of the human UCP2 and UCP3 genes with respect to obesity and diabetes. Of special interest was a promoter variant of UCP2 situated 866bp upstream of transcription initiation (-866G>A, rs659366). This variant changes promoter activity and has been associated with obesity and/or type 2 diabetes in several, although not all, studies. The aim of the current paper is to summarize current evidence of association of UCP2 genetic variation with obesity and type 2 diabetes, with focus on the -866G>A polymorphism.

Mitochondrial uncoupling protein gene cluster variation (UCP2-UCP3) and the risk of incident type 2 diabetes mellitus: the Women's Genome Health Study

OBJECTIVE

Uncoupling protein 2, mitochondrial, (UCP2) gene variation has recently been implicated in type 2 diabetes mellitus (T2DM). To date, no prospective epidemiological data are available.

METHODS

The association between 14 UCP (UCP2-UCP3) gene cluster tagging-SNPs and incident T2DM was investigated in 22,715 Caucasian participants of the prospective Women's Genome Health Study. All were free of known cardiovascular disease and diabetes at baseline. During a 13-year follow-up period, 1445 participants developed an incident T2DM. Multivariable Cox regression analysis was performed to investigate the relationship between genotypes and T2DM risk assuming an additive model. Stratified analysis by smoking status, and haplotype analysis were also performed.

RESULTS

No evidence for an association of any of the tagging-SNPs tested with T2DM risk. Further investigation using stratified analysis, and haplotype-based approach showed similar null findings.

CONCLUSION

The present investigation suggests that the UCP gene cluster variation may not be useful predictor for T2DM risk assessment.

Effect of the common -866G/A polymorphism of the uncoupling protein 2 gene on weight loss and body composition under sibutramine therapy in an obese Taiwanese population

BACKGROUND

Sibutramine, a serotonin and norepinephrine reuptake inhibitor, is used as an anti-obesity drug. Several pharmacogenetic studies have shown correlations between sibutramine effects and genetic variants, such as the 825C/T (rs5443) single nucleotide polymorphism (SNP) in the guanine nucleotide binding protein beta polypeptide 3 (GNB3) gene.

OBJECTIVE

In this study, our goal was to investigate whether a common SNP, -866G/A (rs659366), in the uncoupling protein 2 (UCP2) gene could influence weight reduction and body composition under sibutramine therapy in an obese Taiwanese population.

METHODS

The study included 131 obese patients, 44 in the placebo group and 87 in the sibutramine group. We assessed the measures of weight loss and body fat reduction at the end of a 12-week treatment period by analysis of covariance (ANCOVA) models using gender, baseline weight, and body fat percentage at baseline as covariates.

RESULTS AND CONCLUSION

By comparing the placebo and sibutramine groups with ANCOVA, our data showed a strong effect of sibutramine on weight loss in the combined UCP2 -866 AA + GA genotype groups (p < 0.001). Similarly, a strong effect of sibutramine on body fat percentage loss was found for individuals with the AA or GA genotypes (p < 0.001). In contrast, sibutramine had no significant effect on weight loss (p = 0.063) or body fat percentage loss (p = 0.194) for individuals with the wild-type GG genotype, compared with the placebo group of the same genotype. Moreover, a potential gene-gene interaction between UCP2 and GNB3 was identified by multiple linear regression models for the weight loss (p < 0.001) and for the percent fat loss (p = 0.031) in response to sibutramine. The results suggest that the UCP2 gene may contribute to weight loss and fat change in response to sibutramine therapy in obese Taiwanese patients.

A preliminary candidate genotype-intermediate phenotype study of satiation and gastric motor function in obesity

Stomach motility contributes significantly to fullness sensation while eating and cessation of food intake in humans. Genes controlling adrenergic and serotonergic mechanisms (ADRA2A, GNB3, and SLC6A4) affect gastric emptying (GE), volume (GV), and satiation. Fat mass and obesity-associated gene (FTO) is linked with satiety. Our aim was to examine the association of these candidate genes with stomach functions that signal postprandial fullness: GE, GV, and maximum tolerated volume (MTV). These biomarkers constitute a component of the intermediate phenotype of satiation. A total of 62 overweight or obese participants underwent genotyping of the candidate genes, and validated measurements of GE of solids and liquids by scintigraphy, fasting and postprandial change in GV by SPECT (single photon emission computed tomography), and MTV by nutrient drink test. These markers of satiation were compared for 38 genetic variants in ADRA2A, ADR2C, ADRB3, uncoupling protein (UCP)-2 and -3, GNB3, FTO, and SLC6A4 using a recessive model of inheritance. ADRA2A, ADR2C, UCP-3, GNB3, and FTO loci were significantly associated with the intermediate phenotype markers of satiation: ADR2C (Ins-Del322_325) with accelerated GE; GNB3 (rs1047776) with delayed GE; ADRA2A (rs491589 and rs553668) and GNB3 (rs2269355, rs10849527, and rs3759348) with decreased postprandial GV; ADRA2A (rs3750625) and GNB3 (rs4963517 and rs1129649) with increased postprandial GV; UCP-3 (rs1685356) with increased MTV, and FTO (rs9939609) decreased MTV. Genetic susceptibility to postprandial satiation can be identified through intermediate phenotype markers. With independent validation, these markers may guide patient selection of weight-loss therapies directed at gastric motor functions.

Association of common variants of UCP2 gene with low-grade inflammation in Swedish children and adolescents; the European Youth Heart Study

We examined the associations of two functional variants 866G>A and DEL/INS polymorphisms of UCP2 gene with low-grade inflammatory proteins (C-reactive protein, fibrinogen, complement C3 [C3], and complement C4 [C4]) in 131 children (52.7% boys, aged 9.5 +/- 0.4 y) and 118 adolescents (44.1% males, aged 15.5 +/- 0.4 y) selected from the European Youth Heart Study. Differences in inflammatory markers among the genotype variants of the two UCP2 gene polymorphisms were analyzed after adjusting for sex, age, pubertal stage, fitness, and fatness. The results showed that fibrinogen, C3, and C4 were higher in GG carriers than in subjects carrying the A allele of the 866G>A polymorphism of the UCP2 gene (UCP2 -866G>A) polymorphism (all p < 0.05). The DEL/DEL genotype of 45nt deletion/insertion variant polymorphism of the UCP2 gene (UCP2 DEL/INS) was associated with higher C3 (p < 0.05) than DEL/INS and INS/INS genotypes. This study provides evidence of a role of UCP2 -866G>A in modifying low-grade inflammatory state in apparently healthy children and adolescents. Given the implication of complement factors on atherosclerosis process, these results contribute to explain the reduced cardiovascular risk associated with the A allele of the UCP2 -866G>A polymorphism.