Glutathionylation acts as a control switch for uncoupling proteins UCP2 and UCP3.
ABSTRACT: The mitochondrial uncoupling proteins 2 and 3 (UCP2 and -3) are known to curtail oxidative stress and participate in a wide array of cellular functions, including insulin secretion and the regulation of satiety. However, the molecular control mechanism(s) governing these proteins remains elusive. Here we reveal that UCP2 and UCP3 contain reactive cysteine residues that can be conjugated to glutathione. We further demonstrate that this modification controls UCP2 and UCP3 function. Both reactive oxygen species and glutathionylation were found to activate and deactivate UCP3-dependent increases in non-phosphorylating respiration. We identified both Cys(25) and Cys(259) as the major glutathionylation sites on UCP3. Additional experiments in thymocytes from wild-type and UCP2 null mice demonstrated that glutathionylation similarly diminishes non-phosphorylating respiration. Our results illustrate that UCP2- and UCP3-mediated state 4 respiration is controlled by reversible glutathionylation. Altogether, these findings advance our understanding of the roles UCP2 and UCP3 play in modulating metabolic efficiency, cell signaling, and oxidative stress processes.
Project description:Animal and plant uncoupling protein (UCP) homologues form a subfamily of mitochondrial carriers that are evolutionarily related and possibly derived from a proton/anion transporter ancestor. The brown adipose tissue (BAT) UCP1 has a marked and strongly regulated uncoupling activity, essential to the maintenance of body temperature in small mammals. UCP homologues identified in plants are induced in a cold environment and may be involved in resistance to chilling. The biochemical activities and biological functions of the recently identified mammalian UCP2 and UCP3 are not well known. However, recent data support a role for these UCPs in State 4 respiration, respiration uncoupling and proton leaks in mitochondria. Moreover, genetic studies suggest that UCP2 and UCP3 play a part in energy expenditure in humans. The UCPs may also be involved in adaptation of cellular metabolism to an excessive supply of substrates in order to regulate the ATP level, the NAD(+)/NADH ratio and various metabolic pathways, and to contain superoxide production. A major goal will be the analysis of mice that either lack the UCP2 or UCP3 gene or overexpress these genes. Other aims will be to investigate the possible roles of UCP2 and UCP3 in response to oxidative stress, lipid peroxidation, inflammatory processes, fever and regulation of temperature in certain specific parts of the body.
Project description:<h4>Aims/hypothesis</h4>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.<h4>Methods</h4>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.<h4>Results</h4>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).<h4>Conclusions and interpretation</h4>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.
Project description:We examined the role of UCP gene polymorphisms as susceptibility markers for premature coronary artery disease (pCAD). The UCP2 Ala55Val (C/T rs660339), UCP2 -866G/A (rs659366), and UCP3 -55C/T (rs1800849) polymorphisms were genotyped in 948 patients with pCAD, and 763 controls. The distribution of the UCP2 A55V (C/T rs660339) and UCP3 -55 (rs1800849) was similar in patients and controls. However, under a recessive model, the UCP2 -866 (rs659366) A allele was associated with increased risk of developing pCAD (OR = 1.43, Pc = 0.003). On the other hand, patients with pCAD and UCP2 A55V (rs660339) TT showed high levels of visceral abdominal fat (VAF) (Pc = 0.002), low levels of subcutaneous abdominal fat (SAF) (Pc = 0.001) and high VAT/SAT ratio (Pc < 0.001). Also, patients with UCP2 -866 (rs659366) AA showed increased levels of VAF (Pc = 0.003), low levels of SAF (Pc = 0.001) and a high VAT/SAT ratio (Pc = 0.002), whereas patients with the UCP3 -55 (rs1800849) TT presented high levels of VAF (Pc = 0.002). The results suggest the association of the UCP2 -866 (rs659366) polymorphism with risk of developing pCAD. Some polymorphisms were associated with abdominal fat levels and cardiovascular risk factors.
Project description:Energy expenditure decreases with age, but in the oldest-old, energy demand for maintenance of body functions increases with declining health. Uncoupling proteins have profound impact on mitochondrial metabolic processes; therefore, we focused attention on mitochondrial uncoupling protein genes. Alongside resting metabolic rate (RMR), two SNPs in the promoter region of UCP2 were associated with healthy aging. These SNPs mark potential binding sites for several transcription factors; thus, they may affect expression of the gene. A third SNP in the 3'-UTR of UCP3 interacted with RMR. This UCP3 SNP is known to impact UCP3 expression in tissue culture cells, and it has been associated with body weight and mitochondrial energy metabolism. The significant main effects of the UCP2 SNPs and the interaction effect of the UCP3 SNP were also observed after controlling for fat-free mass (FFM) and physical-activity related energy consumption. The association of UCP2/3 with healthy aging was not found in males. Thus, our study provides evidence that the genetic risk factors for healthy aging differ in males and females, as expected from the differences in the phenotypes associated with healthy aging between the two sexes. It also has implications for how mitochondrial function changes during aging.
Project description:We explored the associations of three variants in the uncoupling protein 2 (UCP2) gene, one variant in the UCP2-UCP3 intergenic region and five variants in the uncoupling protein 3 (UCP3) gene with obesity and diabetes related traits in subjects with impaired glucose tolerance participating in Finnish Diabetes Prevention Study. Altogether 507 overweight individuals (body mass index: 31.2 +/- 4.5 kg/m2, age: 55 +/- 7 years) for whom DNA was available were randomized to either an intensified diet and physical activity group or to a conventional care control group.We analysed the data from the baseline and annual follow-up visits from years 1, 2 and 3. Measurements of anthropometry, plasma glucose and serum insulin in oral glucose tolerance test, serum total cholesterol, HDL-cholesterol and triglycerides were included. The median follow-up time for type 2 diabetes incidence was 7 years. Genetic variants were screened by restriction fragment length polymorphism or Illumina method.UCP3 gene variant rs3781907 was associated with increased serum total and LDL-cholesterol levels, at baseline and during the follow-up period. The same variant was associated with a higher risk of type 2 diabetes. Variants rs1726745, rs11235972 and rs1800849 in the UCP3 gene associated with serum total and LDL-cholesterol at baseline. Haploblock including variants rs659366, rs653529, rs15763, and rs1726745 was associated with measures of abdominal obesity at baseline and in the longitudinal analysis. The haplotype comprising alleles rs659366-G, rs653529-A, rs15763-G and rs1726745-A was associated with higher waist-to-hip ratio, and haplotype comprising alleles rs3781907-G, rs11235972-A, and rs1800849-T was associated with increased serum total and LDL-cholesterol concentrations.Genetic variation in the UCP2-UCP3 gene cluster may act as a modifier increasing serum lipid levels and indices of abdominal obesity, and may thereby also contribute to the metabolic aberrations observed in obesity and type 2 diabetes.
Project description:BACKGROUND:There are disparities for the association between uncoupling proteins (UCP) and type 2 diabetes (T2DM). The study was to examine the associations of genetic variants of UCP2 and UCP3 with prediabetes and T2DM in a rural Chinese population. METHODS:A population-based case-control study of 397 adults with T2DM, 394 with prediabetes and 409 with normal glucose tolerance (NGT) was carried out in 2014 in a rural community in eastern China. Three groups were identified through a community survey and the prediabetes and NGT groups were frequently matched by age and gender with the T2DM group and they were not relatives of T2DM subjects. With r2???0.8 and minor allele frequency (MAF) ?0.05 for tag single nucleotide polymorphisms (SNPs) with potential function, three (rs660339, rs45560234 and rs643064) and six (rs7930460, rs15763, rs647126, rs1800849, rs3781907 and rs1685356) SNPs were selected respectively for UCP2 and UCP3 and genotyped in real time using the MassARRAY system (Sequenom; USA). The haplotypes, gene-environmental interaction and association between genetic variants of UCP2 and UCP3 and prediabetes or T2DM were explored. RESULTS:There were no significant differences in age and sex among three study groups. After the adjustment for possible covariates, the A allele of rs1800849 in UCP3 was significantly associated with prediabetes (aORAA vs GG?=?1.68, 95% CI: 1.02-2.78), and the association was also significant under the recessive model (aOR AA vs GA?+?GG?=?1.64, 95% CI: 1.02-2.66). Also, rs15763 was found to be marginally significantly associated with T2DM under dominant model (ORGA?+?AA vs GG?=?0.73, 95% CI: 0.52-1.03, P?=?0.072). No haplotype was significantly associated with prediabetes or T2DM. Multiplicative interactions for rs660339-overweight on T2DM were observed. In addition, the AA genotype of rs660339 was associated with an increased risk of T2DM in overweight subjects (OR?=?1.48, 95%CI: 0.87-2.52) but with a decreased risk in those with normal weight (OR?=?0.54, 95%CI: 0.28-1.05). CONCLUSIONS:Rs1800849 in UCP3 was significantly associated with prediabetes. Overweight might modify the effects of rs660339 of UCP2 on T2DM.
Project description:The proton-transport activity of UCP1 (uncoupling protein 1) triggers mitochondrial uncoupling and thermogenesis. The exact role of its close homologues, UCP2 and UCP3, is unclear. Mounting evidence associates them with the control of mitochondrial superoxide production. Using CHO (Chinese-hamster ovary) cells stably expressing UCP3 or UCP1, we found no evidence for respiration uncoupling. The explanation lies in the absence of an appropriate activator of UCP protonophoric function. Accordingly, the addition of retinoic acid uncouples the respiration of the UCP1-expressing clone, but not that of the UCP3-expressing ones. In a glucose-containing medium, the extent of the hyperpolarization of mitochondria by oligomycin was close to 22 mV in the five UCP3-expressing clones, contrasting with the variable values observed with the 15 controls. Our observations suggest that, when glycolysis and mitochondria generate ATP, and in the absence of appropriate activators of proton transport, UCPs do not transport protons (uncoupling), but rather other ions of physiological relevance that control mitochondrial activity. A model is proposed using the known passive transport of pyruvate by UCP1.
Project description: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.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.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.The present investigation suggests that the UCP gene cluster variation may not be useful predictor for T2DM risk assessment.
Project description:The role of reactive oxygen species (ROS) in glucose-stimulated insulin release remains controversial because ROS have been shown to both amplify and impede insulin release. In regard to preventing insulin release, ROS activates uncoupling protein-2 (UCP2), a mitochondrial inner membrane protein that negatively regulates glucose-stimulated insulin secretion (GSIS) by uncoupling oxidative phosphorylation. With our recent discovery that the UCP2-mediated proton leak is modulated by reversible glutathionylation, a process responsive to small changes in ROS levels, we resolved to determine whether glutathionylation is required for UCP2 regulation of GSIS. Using Min6 cells and pancreatic islets, we demonstrate that induction of glutathionylation not only deactivates UCP2-mediated proton leak but also enhances GSIS. Conversely, an increase in mitochondrial matrix ROS was found to deglutathionylate and activate UCP2 leak and impede GSIS. Glucose metabolism also decreased the total amount of cellular glutathionylated proteins and increased the cellular glutathione redox ratio (GSH/GSSG). Intriguingly, the provision of extracellular ROS (H(2)O(2), 10 ?M) amplified GSIS and also activated UCP2. Collectively, our findings indicate that the glutathionylation status of UCP2 contributes to the regulation of GSIS, and different cellular sites and inducers of ROS can have opposing effects on GSIS, perhaps explaining some of the controversy surrounding the role of ROS in GSIS.
Project description:<h4>Background</h4>Some studies have reported associations between five uncoupling protein (UCP) 1-3 polymorphisms and type 2 diabetes mellitus (T2DM). However, other studies have failed to confirm the associations. This paper describes a case-control study and a meta-analysis conducted to attempt to determine whether the following polymorphisms are associated with T2DM: -3826A/G (UCP1); -866G/A, Ala55Val and Ins/Del (UCP2) and -55C/T (UCP3).<h4>Methods</h4>The case-control study enrolled 981 T2DM patients and 534 nondiabetic subjects, all of European ancestry. A literature search was run to identify all studies that investigated associations between UCP1-3 polymorphisms and T2DM. Pooled odds ratios (OR) were calculated for allele contrast, additive, recessive, dominant and co-dominant inheritance models. Sensitivity analyses were performed after stratification by ethnicity.<h4>Results</h4>In the case-control study the frequencies of the UCP polymorphisms did not differ significantly between T2DM and nondiabetic groups (P>0.05). Twenty-three studies were eligible for the meta-analysis. Meta-analysis results showed that the Ala55Val polymorphism was associated with T2DM under a dominant model (OR = 1.27, 95% CI 1.03-1.57); while the -55C/T polymorphism was associated with this disease in almost all genetic models: allele contrast (OR = 1.17, 95% CI 1.02-1.34), additive (OR = 1.32, 95% CI 1.01-1.72) and dominant (OR = 1.18, 95% CI 1.02-1.37). However, after stratification by ethnicity, the UCP2 55Val and UCP3 -55C/T alleles remained associated with T2DM only in Asians (OR = 1.25, 95% CI 1.02-1.51 and OR = 1.22, 95% CI 1.04-1.44, respectively; allele contrast model). No significant association of the -3826A/G, -866G/A and Ins/Del polymorphisms with T2DM was observed.<h4>Conclusions</h4>In our case-control study of people with European ancestry we were not able to demonstrate any association between the UCP polymorphisms and T2DM; however, our meta-analysis detected a significant association between the UCP2 Ala55Val and UCP3 -55C/T polymorphisms and increased susceptibility for T2DM in Asians.