The mitochondrial uncoupling-protein homologues

Nanogel-based nasal ghrelin vaccine prevents obesity

Obesity is associated with multiple comorbidities such as cardiovascular diseases and has a huge economic impact on the health-care system. However, the treatment of obesity remains insufficient in terms of efficacy, tolerability, and safety. Here we created a nasal vaccine against obesity for the first time. To avoid the injectable administration-caused pain and skin-related adverse event, we focused on the intranasal route of antigen delivery. We developed a vaccine antigen (ghrelin-PspA (pneumococcal surface protein A)), which is a recombinant fusion protein incorporating ghrelin, a hormone that stimulates food intake and decreases energy expenditure, and PspA, a candidate of pneumococcal vaccine as a carrier protein. Ghrelin-PspA antigen was mixed with cyclic di-GMP adjuvant to enhance the immunogenicity and incorporated within a nanometer-sized hydrogel for the effective antigen delivery. Intranasal immunization with ghrelin-PspA vaccine elicited serum immunoglobulin G antibodies against ghrelin and attenuated body weight gain in diet-induced obesity mice. This obesity-attenuating effect was caused by a decrease in fat accumulation and an increase in energy expenditure that was partially due to an increase in the expression of mitochondrial uncoupling protein 1 in brown adipose tissue. The development of this nasal vaccine provides a new strategy for the prevention and treatment of obesity.

Uncoupling protein 2 haplotype does not affect human brain structure and function in a sample of community-dwelling older adults

Uncoupling protein 2 (UCP2) is a mitochondrial membrane protein that plays a role in uncoupling electron transport from adenosine triphosphate (ATP) formation. Polymorphisms of the UCP2 gene in humans affect protein expression and function and have been linked to survival into old age. Since UCP2 is expressed in several brain regions, we investigated in this study whether UCP2 polymorphisms might 1) affect occurrence of neurodegenerative or mental health disorders and 2) affect measures of brain structure and function. We used structural magnetic resonance imaging (MRI), diffusion-weighted MRI and resting-state functional MRI in the neuroimaging sub-study of the Whitehall II cohort. Data from 536 individuals aged 60 to 83 years were analyzed. No association of UCP2 polymorphisms with the occurrence of neurodegenerative disorders or grey and white matter structure or resting-state functional connectivity was observed. However, there was a significant effect on occurrence of mood disorders in men with the minor alleles of -866G>A (rs659366) and Ala55Val (rs660339)) being associated with increasing odds of lifetime occurrence of mood disorders in a dose dependent manner. This result was not accompanied by effects of UCP2 polymorphisms on brain structure and function, which might either indicate that the sample investigated here was too small and underpowered to find any significant effects, or that potential effects of UCP2 polymorphisms on the brain are too subtle to be picked up by any of the neuroimaging measures used.

Specific Interaction of the Human Mitochondrial Uncoupling Protein 1 with Free Long-Chain Fatty Acid

The mitochondrial uncoupling protein 1 (UCP1) generates heat by causing proton leak across the mitochondrial inner membrane that requires fatty acid (FA). The mechanism by which UCP1 uses FA to conduct proton remains unsolved, and it is also unclear whether a direct physical interaction between UCP1 and FA exists. Here, we have shown using nuclear magnetic resonance that FA can directly bind UCP1 at a helix-helix interface site composed of residues from the transmembrane helices H1 and H6. According to the paramagnetic relaxation enhancement data and molecular dynamics simulation, the FA acyl chain appears to fit into the groove between H1 and H6 while the FA carboxylate group interacts with the basic residues near the matrix side of UCP1. Functional mutagenesis showed that mutating the observed FA binding site severely reduced UCP1-mediated proton flux. Our study identifies a functionally important FA-UCP1 interaction that is potentially useful for mechanistic understanding of UCP1-mediated thermogenesis.

The single IGF-1 partial deficiency is responsible for mitochondrial dysfunction and is restored by IGF-1 replacement therapy

BACKGROUND & AIMS

We previously described in cirrhosis and aging, both conditions of IGF-1 deficiency, a clear hepatic mitochondrial dysfunction with increased oxidative damage. In both conditions, the hepatic mitochondrial function was improved with low doses of IGF-1. The aim of this work was to explore if the only mere IGF-1 partial deficiency, without any exogenous insult, is responsible for hepatic mitochondrial dysfunction.

METHODS

Heterozygous (igf1^+/-) mice were divided into two groups: untreated and treated mice with low doses of IGF-1. WT group was used as controls. Parameters of hepatic mitochondrial function were determined by flow cytometry, antioxidant enzyme activities were determined by spectrophotometry, and electron chain transport enzyme levels were determined by immunohistochemistry and immunofluorescence analyses. Liver expression of genes coding for proteins involved in mitochondrial protection and apoptosis was studied by microarray analysis and RT-qPCR.

RESULTS

Hz mice showed a significant reduction in hepatic mitochondrial membrane potential (MMP) and ATPase activity, and an increase in intramitochondrial free radical production and proton leak rates, compared to controls. These parameters were normalized by IGF-1 replacement therapy. No significant differences were found between groups in oxygen consumption and antioxidant enzyme activities, except for catalase, whose activity was increased in both Hz groups. Relevant genes coding for proteins involved in mitochondrial protection and survival were altered in Hz group and were reverted to normal in Hz+IGF-1 group.

CONCLUSIONS

The mere IGF-1 partial deficiency is per se associated with hepatic mitochondrial dysfunction sensitive to IGF-1 replacement therapy. Results in this work prove that IGF-1 is involved in hepatic mitochondrial protection, because it is able to reduce free radical production, oxidative damage and apoptosis. All these IGF-1 actions are mediated by the modulation of the expression of genes encoding citoprotective and antiapoptotic proteins.

The roles of metabolic thermogenesis in body fat regulation in striped hamsters fed high-fat diet at different temperatures

The metabolic thermogenesis plays important roles in thermoregulation, and it may be also involved in body fat regulation. The thermogenesis of brown adipose tissue (BAT) is largely affected by ambient temperature, but it is unclear if the roles in body fat regulation are dependent on the temperature. In the present study, uncoupling protein 1 (ucp1)-based BAT thermogenesis, energy budget and body fat content were examined in the striped hamsters fed high fat diet (HF) at cold (5°C) and warm (30°C) temperatures. The effect of 2, 4-dinitrophenol (DNP), a chemical uncoupler, on body fat was also examined. The striped hamsters showed a notable increase in body fat following the HF feeding at 21°C. The increased body fat was markedly elevated at 30°C, but was significantly attenuated at 5°C compared to that at 21°C. The hamsters significantly increased energy intake at 5°C, but consumed less food at 30°C relative to those at 21°C. Metabolic thermogenesis, indicated by basal metabolic rate, UCP1 expression and/or serum triiodothyronine levels, significantly increased at 5°C, but decreased at 30°C compared to that at 21°C. A significant decrease in body fat content was observed in DNP-treated hamsters relative to the controls. These findings suggest that the roles of metabolic thermogenesis in body fat regulation largely depend on ambient temperature. The cold-induced enhancement of BAT thermogenesis may contribute the decreased body fat, resulting in a lean mass. Instead, the attenuation of BAT thermogenesis at the warm may result in notable obesity.

Angiotensin type 2 receptor activation promotes browning of white adipose tissue and brown adipogenesis

Brown adipose tissue dissipates energy in the form of heat. Recent studies have shown that adult humans possess both classical brown and beige adipocytes (brown-like adipocytes in white adipose tissue, WAT), and stimulating brown and beige adipocyte formation can be a new avenue to treat obesity. Angiotensin II (AngII) is a peptide hormone that plays important roles in energy metabolism via its angiotensin type 1 or type 2 receptors (AT1R and AT2R). Adipose tissue is a major source of AngII and expresses both types of its receptors, implying the autocrine and paracrine role of AngII in regulating adipose functions and self-remodeling. Here, based on the in vitro studies on primary cultures of mouse white adipocytes, we report that, AT2R activation, either by AngII or AT2R agonist (C21), induces white adipocyte browning, by increasing PPARγ expression, at least in part, via ERK1/2, PI3kinase/Akt and AMPK signaling pathways. It is also found that AngII–AT2R enhances brown adipogenesis. In the in vivo studies on mice, administration of AT1R antagonist (ZD7155) or AT2R agonist (C21) leads to the increase of WAT browning, body temperature and serum adiponectin, as well as the decrease of WAT mass and the serum levels of TNFα, triglycerides and free fatty acids. In addition, AT2R-induced browning effect is also observed in human white adipocytes, as evidenced by the increased UCP1 expression and oxygen consumption. Finally, we provide evidence that AT2R plays important roles in hormone T3-induced white adipose browning. This study, for the first time, reveals the browning and brown adipogenic effects of AT2R and suggests a potential therapeutic target to combat obesity and related metabolic disorders.

Mutations in valosin-containing protein (VCP) decrease ADP/ATP translocation across the mitochondrial membrane and impair energy metabolism in human neurons

Mutations in the gene encoding valosin-containing protein (VCP) lead to multisystem proteinopathies including frontotemporal dementia. We have previously shown that patient-derived VCP mutant fibroblasts exhibit lower mitochondrial membrane potential, uncoupled respiration, and reduced ATP levels. This study addresses the underlying basis for mitochondrial uncoupling using VCP knockdown neuroblastoma cell lines, induced pluripotent stem cells (iPSCs), and iPSC-derived cortical neurons from patients with pathogenic mutations in VCP Using fluorescent live cell imaging and respiration analysis we demonstrate a VCP mutation/knockdown-induced dysregulation in the adenine nucleotide translocase, which results in a slower rate of ADP or ATP translocation across the mitochondrial membranes. This deregulation can explain the mitochondrial uncoupling and lower ATP levels in VCP mutation-bearing neurons via reduced ADP availability for ATP synthesis. This study provides evidence for a role of adenine nucleotide translocase in the mechanism underlying altered mitochondrial function in VCP-related degeneration, and this new insight may inform efforts to better understand and manage neurodegenerative disease and other proteinopathies.

Fatty acid binding protein 4/aP2-dependent BLT1R expression and signaling

Previous studies have shown that reduced levels of the adipocyte fatty acid binding protein (FABP)4 (AFABP/aP2), result in metabolic improvement including potentiated insulin sensitivity and attenuated atherosclerosis. Mechanistically, pharmacologic or genetic inhibition of FABP4 in macrophages upregulates UCP2, attenuates reactive oxygen species (ROS) production, polarizes cells toward the anti-inflammatory M2 state, and reduces leukotriene (LT) secretion. At the protein level, FABP4 stabilizes LTA₄ toward chemical hydrolysis, thereby potentiating inflammatory LTC₄ synthesis. Herein, we extend the FABP4-LT axis and demonstrate that genetic knockout of FABP4 reduces expression of the major macrophage LT receptor, LTB₄ receptor 1 (BLT1R), via a ROS-dependent mechanism. Consistent with inflammation driving BLT1R expression, M1 polarized macrophages express increased levels of BLT1R relative to M2 polarized macrophages and treatment with proinflammatory lipopolysaccharide increased BLT1R mRNA and protein expression. In FABP4 knockout macrophages, silencing of UCP2, increased ROS levels and led to increased expression of BLT1R mRNA. Similarly, addition of exogenous H₂O₂ upregulated BLT1R expression, whereas the addition of a ROS scavenger, N-acetyl cysteine, decreased BLT1R levels. As compared with WT macrophages, LTB₄-BLT1R-dependent JAK2-phosphorylation was reduced in FABP4 knockout macrophages. In summary, these results indicate that FABP4 regulates the expression of BLT1R and its downstream signaling via control of oxidative stress in macrophages.

Attenuated mTOR Signaling and Enhanced Glucose Homeostasis by Dietary Supplementation with Lotus Seedpod Oligomeric Procyanidins in Streptozotocin (STZ)-Induced Diabetic Mice

This study investigated the protective role of lotus seedpod oligomeric procyanidins (LSOPC) and synbiotics (Bifidobacterium Bb-12 and xylo-oligosaccharide) against high fat and streptozotocin (STZ)-induced diabetes. Administration of LSOPC or synbiotics had no effect on blood glucose in normal mice. Treatments with LSOPC for 12 weeks markedly reduced blood glucose, FFA, endotoxin, and GHbA1c and improved glucose homeostasis, lipid metabolism, and insulin levels. In addition, administration of LSOPC significantly reversed the increase of mTOR and p66^Shc in liver, skeletal muscle, and white adipose tissue (WAT). LSOPC significantly increased glucose uptake and glycolysis in liver, skeletal muscle, and WAT while improving heat generation in brown adipose tissue (BAT) and inhibiting gluconeogenesis and lipogenesis in liver. Furthermore, synbiotics strengthened the improving effect of LSOPC. These findings demonstrated that LSOPC and synbiotics may regulate glucose disposal in peripheral target tissues through the p66^Shc-mTOR signaling pathway.

Ghrelin suppresses inflammation in HUVECs by inhibiting ubiquitin-mediated uncoupling protein 2 degradation

Atherosclerosis is considered the major cause of heart attack, stroke and gangrene of the extremities, which is responsible for 50% of all mortality in Western countries. The pathogenesis and causes of atherosclerosis remain elusive. Recent studies highlight inflammation as a contributing factor for atherosclerosis in all stages of the disease process. In this study, we demonstrate that the treatment of human umbilical vein endothelial cells (HUVECs) with ghrelin inhibits the oxidized low-density lipoprotein (oxLDL)-induced inflammatory response, In addition, treatment with ghrelin led to the accumulation of uncoupling protein 2 (UCP2) in the cells, thus decreasing reactive oxygen species (ROS) generation. Moreover, the siRNA-mediated knockdown of UCP2 expression suggested that the inhibitory effects of ghrelin on the inflammatory response relied on its ability to induce the accumulation of cellular UCP2 levels. Further analysis indicated that the accumulation of UCP2 in the ghrelin-treated cells was due to the ability of ghrelin to inhibit the ubiquitination of UCP2 and prevent UCP2 degradation, resulting in the extended protein half-life of UCP2. On the whole, our data indicate that ghrelin inhibits the oxLDL-induced inflammatory response in HUVECs, and may thus have potential for use as an anti-atherosclerotic agent. Our data may also provide valuable insight into the pathogenesis of atherosclerosis.

Association and expression analyses of the Ucp2 and Ucp3 gene polymorphisms with body measurement and meat quality traits in Qinchuan cattle

The uncoupling proteins (UCPs) belong to the mitochondrial inner membrane anion carrier superfamily and play an important role in energy homeostasis. Genetic studies have demonstrated that Ucp2 and Ucp3 gene variants are involved in obesity and metabolic syndrome. The aim of this study was to identify associations between polymorphisms of Ucp2 and Ucp3 genes and economically-important traits in Qinchuan cattle. In the present study, one single-nucleotide polymorphism (SNP) in the 5'UTR region (SNP1:g.C-754G) of the Ucp2 gene was identified by direct sequencing of 441 Qinchuan cattle. Two SNPs in exon 3 (SNP2: g.G4877A: SNP3: g.C4902T) of the Ucp3 gene were identified by sequencing and polymerase chain reactionrestriction fragment length polymorphism (PCR-RFLP) among 441 Qinchuan cattle. Association analysis showed that SNP1 and SNP2 were associated with the meat quality traits (MQTs) including back fat thickness, loin muscle area and intramuscular fat content. SNP3 was found to be associated with part of the body measurement traits (BMTs) which referred to withers height and chest depth. In addition, QTL pyramiding analysis showed that individuals with diplotype P3P3 (GG-GG-CC) exhibited the best performance in terms of back fat thickness, loin muscle area, intramuscular fat content, rump length, hip width, chest depth and chest circumference. With regard to the G4877A mutation, real time PCR analysis revealed that individuals with AA genotype of the Ucp3 gene expressed higher mRNA levels than those with GG genotype. These results suggest that the diplotype P3P3 (GG-GG-CC) could be used as a molecular marker of the combined genotypes for future selection of body measurement traits and meat quality traits in Qinchuan cattle.

Bardoxolone-methyl inhibits migration and metabolism in MCF7 cells

Bardoxolone-methyl (BAR) is reported to have anti-inflammatory, anti-proliferative and anti-fibrotic effects. BAR activates Nrf2 and may ameliorate oxidative stress through induction of antioxidant genes. However, off-target effects, probably concentration and NFkB-dependent, have limited the clinical use of BAR. Nrf2 regulates expression of antioxidant and mitochondrial genes and has been proposed as a target for both obesity and breast cancer. Therefore, we explored whether BAR can alter migration and proliferation in the MCF7 cell line and whether metabolic function is affected by BAR. Incubation with BAR caused a time-dependent migratory inhibition and an associated decrease in mitochondrial respiration. Both migratory and mitochondrial inhibition by BAR were further enhanced in the presence of fatty acids. In addition to the activation of Nrf2, BAR altered the expression of target mRNA GCLC and UCP1. After 24 h, BAR inhibited both glycolytic capacity, reserve (p < 0.05) and oxidative phosphorylation (p < 0.001) with an associated increase in mitochondrial ROS and loss of intracellular glutathione in MCF7 cells; however, impairment of mitochondrial activity was prevented by N-acetyl cysteine. The fatty acid, palmitate, increased mitochondrial ROS, impaired migration and oxidative phosphorylation but palmitate toxicity towards MCF7 could not be inhibited by N-acetyl cysteine suggesting that they exert effects through different pathways. BAR-activated AKT, induced DNA damage and inhibited cell proliferation. When the proteasome was inhibited, there was loss of BAR-mediated changes in p65 phosphorylation and SOD2 expression suggesting non-canonical NFkB signaling effects. These data suggest that BAR-induced ROS are important in inhibiting MCF7 migration and metabolism by negatively affecting glycolytic capacity and mitochondrial function.

Effect of miR-146 targeted HDMCP up-regulation in the pathogenesis of nonalcoholic steatohepatitis

BACKGROUNDS/AIMS

Mitochondrial dysfunction plays an important role inthe pathogenesis of nonalcoholic steatohepatitis (NASH), where uncoupling protein (UCP) is actively involved. We previously reported the uncoupling activity of HDMCP and its role in liver steatosis. We now aim to investigate the degree and therapeutic effect of HDMCP in NASH and the regulatory role of miR-146 on HDMCP.

METHODS

NASH animal model was established by feeding BALB/c mice with MCD diet while L02 cell was cultured with high concentration of fatty acid (HFFA) for 72h to mimic the steatosis and inflammation of NASH in-vitro appearance. The steatosis level was assessed by H-E/oil-red staining and serum/supernatant marker detection. The inflammation activity was evaluated by levels of Hepatic activity index, transwell, apoptosis degree (TUNEL/flow cytometry) and serum/supernatant marker. HDMCP level was detected by western blot and miRNA expression was tested by qRT-PCR. NASH severity change was recorded after RNA interference while the regulatory role of miR-146 on HDMCP was confirmed by dual luciferase report system. The H2O2 and ATP levels were measured for mechanism exploration.

RESULTS

Increased HDMCP expression was identified in NASH animal model and HFFA-72h cultured L02 cell. Moreover, under regulation of miR-146, NASH alleviation was achieved after HDMCP downregulation in both in vivo and in vitro, according to the declination of steatosis and inflammation related markers. Though H2O2 and ATP levels were increased and decreased in NASH models, HDMCP down regulation both increased their levels.

CONCLUSIONS

The miR-146-HDMCP-ATP/H2O2 pathway may provide novel mechanism and treatment option for NASH.

The sympathetic neuro-adipose connection and the control of body weight

In recent decades, obesity has become a global public health crisis irrespective of age or gender [20]. But according to historic records, concerns over appropriate maintenance of body size have been long established. For more than to 2 millennia, the main therapeutic approach to curb excess weight has been to recommend dietary restrictions and regular exercise (Haslam, 2016). Nevertheless, more contemporary studies indicate that the employment of such approaches in the treatment of severely obese patients causes metabolic adaptions which impair their long-term success in weight management [8]. These evidences highlight thus, the urgency in the search for a more comprehensive knowledge of the mechanisms that underlie the control of body weight, which would be essential for the development of effective strategies for the treatment of obesity and its comorbidities. Importantly, the discovery of the hormone leptin [33]and the use of novel techniques in targeted transgenesis [32] have enabled progress in defining some of the key players and the molecular mechanisms that are involved in the processes that control body size homeostasis and energy balance, and how obesity may disrupt leptin's feedback loop and lead to the pathology of metabolic syndrome. On the light of such findings, here we review how the sympathetic nervous system modulates adipose tissue metabolism downstream of leptin's action on the CNS, with particular focus on how this system may be disrupted in the context of excess adiposity, plus highlight the potential clinical implications arising from a better understanding of the physiologic control of the sympathetic neuro-adipose connection.

Effects of apelin on reproductive functions: relationship with feeding behavior and energy metabolism

Apelin is an adipose tissue derived peptidergic hormone. In this study, 40 male Sprague-Dawley rats were used (four groups; n = 10). Apelin-13 at three different dosages (1, 5 and 50 μg/kg) was given intraperitoneally while the control group received vehicle the same route for a period of 14 days. In results, apelin-13 caused significant decreases in serum testosterone, luteinizing hormone and follicle-stimulating hormone levels (p < 0.05). Administration of apelin-13 significantly increased body weights, food intake, serum low-density lipoprotein and total cholesterol levels (p < 0.05), but caused significant decreases in high-density lipoprotein levels (p < 0.05). Serum glucose and triglyceride levels were not significantly altered by apelin-13 administration. Significant decreases in both uncoupling protein (UCP)-1 levels in the white and brown adipose tissues and UCP-3 levels in the biceps muscle (p < 0.05) were noted. The findings of the study suggest that apelin-13 may not only lead to obesity by increasing body weight but also cause infertility by suppressing reproductive hormones.

SRF and MKL1 Independently Inhibit Brown Adipogenesis

Active brown adipose tissue is responsible for non-shivering thermogenesis in mammals which affects energy homeostasis. The molecular mechanisms underlying this activation as well as the formation and activation of brite adipocytes have gained increasing interest in recent years as they might be utilized to regulate systemic metabolism. We show here that the transcriptional regulators SRF and MKL1 both act as repressors of brown adipogenesis. Loss-of-function of these transcription factors leads to a significant induction of brown adipocyte differentiation, increased levels of UCP1 and other thermogenic genes as well as increased respiratory function, while SRF induction exerts the opposite effects. Interestingly, we observed that knockdown of MKL1 does not lead to a reduced expression of typical SRF target genes and that the SRF/MKL1 inhibitor CCG-1423 had no significant effects on brown adipocyte differentiation. Contrary, knockdown of MKL1 induces a significant increase in the transcriptional activity of PPARγ target genes and MKL1 interacts with PPARγ, suggesting that SRF and MKL1 independently inhibit brown adipogenesis and that MKL1 exerts its effect mainly by modulating PPARγ activity.

Transient Opening of the Mitochondrial Permeability Transition Pore Induces Microdomain Calcium Transients in Astrocyte Processes

Astrocytes extend highly branched processes that form functionally isolated microdomains, facilitating local homeostasis by redistributing ions, removing neurotransmitters, and releasing factors to influence blood flow and neuronal activity. Microdomains exhibit spontaneous increases in calcium (Ca²⁺), but the mechanisms and functional significance of this localized signaling are unknown. By developing conditional, membrane-anchored GCaMP3 mice, we found that microdomain activity that occurs in the absence of inositol triphosphate (IP3)-dependent release from endoplasmic reticulum arises through Ca²⁺ efflux from mitochondria during brief openings of the mitochondrial permeability transition pore. These microdomain Ca²⁺ transients were facilitated by the production of reactive oxygen species during oxidative phosphorylation and were enhanced by expression of a mutant form of superoxide dismutase 1 (SOD1 G93A) that causes astrocyte dysfunction and neurodegeneration in amyotrophic lateral sclerosis (ALS). By localizing mitochondria to microdomains, astrocytes ensure local metabolic support for energetically demanding processes and enable coupling between metabolic demand and Ca²⁺ signaling events.

UCP2 up-regulation within the course of autoimmune encephalomyelitis correlates with T-lymphocyte activation

Multiple sclerosis (MS) is an inflammatory demyelinating autoimmune disorder of the central nervous system (CNS) associated with severe neurological disability. Reactive oxygen species (ROS) and mitochondrial dysfunction play a pivotal role in the pathogenesis of this disease. Several members of the mitochondrial uncoupling protein subfamily (UCP2-UCP5) were suggested to regulate ROS by diminishing the mitochondrial membrane potential and constitute therefore a promising pharmacological target for MS. To evaluate the role of different uncoupling proteins in neuroinflammation, we have investigated their expression patterns in murine brain and spinal cord (SC) during different stages of experimental autoimmune encephalomyelitis (EAE), an animal model for MS. At mRNA and protein levels we found that only UCP2 is up-regulated in the SC, but not in brain. The increase in UCP2 expression was antigen-independent, reached its maximum between 14 and 21days in both OVA and MOG immunized animals and correlated with an augmented number of CD3⁺ T-lymphocytes in SC parenchyma. The decrease in abundance of UCP4 was due to neuronal injury and was only detected in CNS of MOG-induced EAE animals. The results provide evidence that the involvement of mitochondrial UCP2 in CNS inflammation during EAE may be mainly explained by the invasion of activated T-lymphocytes. This conclusion coincides with our previous observation that UCP2 is up-regulated in activated and rapidly proliferating T-cells and participates in fast metabolic re-programming of cells during proliferation.

Mitochondrial activation chemicals synergize with surface receptor PD-1 blockade for T cell-dependent antitumor activity

Although immunotherapy by PD-1 blockade has dramatically improved the survival rate of cancer patients, further improvement in efficacy is required to reduce the fraction of less sensitive patients. In mouse models of PD-1 blockade therapy, we found that tumor-reactive cytotoxic T lymphocytes (CTLs) in draining lymph nodes (DLNs) carry increased mitochondrial mass and more reactive oxygen species (ROS). We show that ROS generation by ROS precursors or indirectly by mitochondrial uncouplers synergized the tumoricidal activity of PD-1 blockade by expansion of effector/memory CTLs in DLNs and within the tumor. These CTLs carry not only the activation of mechanistic target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK) but also an increment of their downstream transcription factors such as PPAR-gamma coactivator 1α (PGC-1α) and T-bet. Furthermore, direct activators of mTOR, AMPK, or PGC-1α also synergized the PD-1 blockade therapy whereas none of above-mentioned chemicals alone had any effects on tumor growth. These findings will pave a way to developing novel combinatorial therapies with PD-1 blockade.

FABP4/aP2 Regulates Macrophage Redox Signaling and Inflammasome Activation via Control of UCP2

Obesity-linked metabolic disease is mechanistically associated with the accumulation of proinflammatory macrophages in adipose tissue, leading to increased reactive oxygen species (ROS) production and chronic low-grade inflammation. Previous work has demonstrated that deletion of the adipocyte fatty acid-binding protein (FABP4/aP2) uncouples obesity from inflammation via upregulation of the uncoupling protein 2 (UCP2). Here, we demonstrate that ablation of FABP4/aP2 regulates systemic redox capacity and reduces cellular protein sulfhydryl oxidation and, in particular, oxidation of mitochondrial protein cysteine residues. Coincident with the loss of FABP4/aP2 is the upregulation of the antioxidants superoxide dismutase (SOD2), catalase, methionine sulfoxide reductase A, and the 20S proteasome subunits PSMB5 and αβ. Reduced mitochondrial protein oxidation in FABP4/aP2^-/- macrophages attenuates the mitochondrial unfolded-protein response (mtUPR) as measured by expression of heat shock protein 60, Clp protease, and Lon peptidase 1. Consistent with a diminished mtUPR, FABP4/aP2^-/- macrophages exhibit reduced expression of cleaved caspase-1 and NLRP3. Secretion of interleukin 1β (IL-1β), in response to inflammasome activation, is ablated in FABP4/aP2^-/- macrophages, as well as in FABP4/aP2 inhibitor-treated cells, but partially rescued in FABP4/aP2-null macrophages when UCP2 is silenced. Collectively, these data offer a novel pathway whereby FABP4/aP2 regulates macrophage redox signaling and inflammasome activation via control of UCP2 expression.

Mitochondrial metabolism: a driver of energy utilisation and product quality?

High feed efficiency is a very desirable production trait as it positively influences resource utilisation, profitability and environmental considerations, albeit at the possible expense of product quality. The modern broiler is arguably the most illustrative model species as it has been transformed over the past half century into an elite feed converter. Some producers are currently reporting that 42-day-old birds gain 1 kg of wet weight for every 1.35 kg of dry weight consumed. Its large breast muscle is exclusively composed of large, low mitochondrial-content Type IIB fibres, which may contribute to low maintenance costs and high efficiency. In an effort to gain a better understanding of individual variation in chicken feed efficiency, our group has been exploring the biology of the mitochondrion at multiple levels of organisation. The mitochondrion is the organelle where much biochemical energy transformation occurs in the cell. Using Cobb-Vantress industrial birds as our primary experimental resource, we have explored the tissue content, structure and function of the mitochondrion and its relationship to growth, development, efficiency and genetic background. While much remains to be understood, recent highlights include (1) variation in muscle mitochondrial content that is associated with performance phenotypes, (2) altered muscle mitochondrial gene and protein expression in birds differing in feed efficiency, (3) variation in isolated mitochondrial function in birds differing in feed efficiency and (4) evidence for an unexpected role for the mitochondrially localised progesterone receptor in altering bird muscle metabolism. Mitochondrial function is largely conserved across the vertebrates, so the same metabolic principles appear to apply to the major production species, whether monogastric or ruminant. A speculative role for the mitochondria in aspects of meat quality and in influencing postmortem anaerobic metabolism will conclude the manuscript.

Inter-organ regulation of adipose tissue browning

Adaptive thermogenesis is an important component of energy expenditure. Brown adipocytes are best known for their ability to convert chemical energy into heat. Beige cells are brown-like adipocytes that arise in white adipose tissue in response to certain environmental cues to dissipate heat and improve metabolic homeostasis. A large body of intrinsic factors and external signals are critical for the function of beige adipocytes. In this review, we discuss recent advances in our understanding of neuronal, hormonal, and metabolic regulation of the development and activation of beige adipocytes, with a focus on the regulation of beige adipocytes by other organs, tissues, and cells. Understanding the cellular and molecular mechanisms of inter-organ regulation of adipose tissue browning may provide an avenue for combating obesity and associated diseases.

Xanthoangelol and 4-hydroxyderrcin suppress obesity-induced inflammatory responses

OBJECTIVE

Obesity-induced inflammation plays a pivotal role in the pathogenesis of insulin resistance and type 2 diabetes. Xanthoangelol (XA) and 4-hydroxyderrcin (4-HD), phytochemicals extracted from Angelica keiskei, have been reported to possess various biological properties. Whether XA and 4-HD alleviate obesity-induced inflammation and inflammation-induced adipocyte dysfunction was investigated.

METHODS

For the in vitro study, a co-culture system composed of macrophages and adipocytes and macrophages stimulated with conditioned medium derived from fully differentiated adipocytes was conducted. For the in vivo study, mice were fed a high-fat diet supplemented with XA for 14 weeks.

RESULTS

XA and 4-HD suppressed inflammatory factors in co-culture system. Moreover, treatment of RAW macrophages with XA and 4-HD moderated the suppression of uncoupling protein 1 promoter activity and gene expression in C3H10T1/2 adipocytes, which was induced by conditioned medium derived from LPS-stimulated RAW macrophages. Also, XA and 4-HD inhibited c-Jun N-terminal kinase phosphorylation, nuclear factor-κB, and activator protein 1, the last two being transcription activators in activated macrophages. Furthermore, in mice fed the high-fat diet, XA reduced inflammatory factors within the white adipose tissue.

CONCLUSIONS

These results suggest that XA and 4-HD might be promising phytochemicals to suppress obesity-induced inflammation and inflammation-induced adipocyte dysfunction.

UCP1: A transporter for H+ and fatty acid anions

Adaptive thermogenesis regulates core body temperature, controls fat deposition, and contributes strongly to the overall energy balance. This process occurs in brown fat and requires uncoupling protein 1 (UCP1), an integral protein of the inner mitochondrial membrane. Classic biochemical studies revealed the general principle of adaptive thermogenesis: in the presence of long-chain fatty acids (FA), UCP1 increases the permeability of the inner mitochondrial membrane for H⁺, which makes brown fat mitochondria produce heat rather than ATP. However, the exact mechanism by which UCP1 increases the membrane H⁺ conductance in a FA-dependent manner has remained a fundamental unresolved question. Recently, the patch-clamp technique was successfully applied to the inner mitochondrial membrane of brown fat to directly characterize the H⁺ currents carried by UCP1. Based on the patch-clamp data, a new model of UCP1 operation was proposed. In brief, FA anions are transport substrates of UCP1, and UCP1 operates as an unusual FA anion/H⁺ symporter. Interestingly, in contrast to short-chain FA anions, long-chain FA anions cannot easily dissociate from UCP1 due to strong hydrophobic interactions established by their carbon tails, and a single long-chain FA participates in many H⁺ transport cycles. Therefore, in the presence of long-chain FA, endogenous activators of brown fat thermogenesis, UCP1 effectively operates as an H⁺ uniport. In addition to their transport function, long-chain FA competitively remove tonic inhibition of UCP1 by cytosolic purine nucleotides, thus enabling activation of the thermogenic H⁺ leak through UCP1 under physiological conditions.

Impact of intracellular ion channels on cancer development and progression

Cancer research is nowadays focused on the identification of possible new targets in order to try to develop new drugs for curing untreatable tumors. Ion channels have emerged as "oncogenic" proteins, since they have an aberrant expression in cancers compared to normal tissues and contribute to several hallmarks of cancer, such as metabolic re-programming, limitless proliferative potential, apoptosis-resistance, stimulation of neo-angiogenesis as well as cell migration and invasiveness. In recent years, not only the plasma membrane but also intracellular channels and transporters have arisen as oncological targets and were proposed to be associated with tumorigenesis. Therefore, the research is currently focusing on understanding the possible role of intracellular ion channels in cancer development and progression on one hand and, on the other, on developing new possible drugs able to modulate the expression and/or activity of these channels. In a few cases, the efficacy of channel-targeting drugs in reducing tumors has already been demonstrated in vivo in preclinical mouse models.

Identification of Genes Potentially Associated with the Fertility Instability of S-Type Cytoplasmic Male Sterility in Maize via Bulked Segregant RNA-Seq

S-type cytoplasmic male sterility (CMS-S) is the largest group among the three major types of CMS in maize. CMS-S exhibits fertility instability as a partial fertility restoration in a specific nuclear genetic background, which impedes its commercial application in hybrid breeding programs. The fertility instability phenomenon of CMS-S is controlled by several minor quantitative trait locus (QTLs), but not the major nuclear fertility restorer (Rf3). However, the gene mapping of these minor QTLs and the molecular mechanism of the genetic modifications are still unclear. Using completely sterile and partially rescued plants of fertility instable line (FIL)-B, we performed bulk segregant RNA-Seq and identified six potential associated genes in minor effect QTLs contributing to fertility instability. Analyses demonstrate that these potential associated genes may be involved in biological processes, such as floral organ differentiation and development regulation, energy metabolism and carbohydrates biosynthesis, which results in a partial anther exsertion and pollen fertility restoration in the partially rescued plants. The single nucleotide polymorphisms (SNPs) identified in two potential associated genes were validated to be related to the fertility restoration phenotype by KASP marker assays. This novel knowledge contributes to the understanding of the molecular mechanism of the partial fertility restoration of CMS-S in maize and thus helps to guide the breeding programs.

Uncoupling protein 2 in the glial response to stress: implications for neuroprotection

Reactive oxygen species (ROS) are free radicals thought to mediate the neurotoxic effects of several neurodegenerative disorders. In the central nervous system, ROS can also trigger a phenotypic switch in both astrocytes and microglia that further aggravates neurodegeneration, termed reactive gliosis. Negative regulators of ROS, such as mitochondrial uncoupling protein 2 (UCP2) are neuroprotective factors that decrease neuron loss in models of stroke, epilepsy, and parkinsonism. However, it is unclear whether UCP2 acts purely to prevent ROS production, or also to prevent gliosis. In this review article, we discuss published evidence supporting the hypothesis that UCP2 is a neuroprotective factor both through its direct effects in decreasing mitochondrial ROS and through its effects in astrocytes and microglia. A major effect of UCP2 activation in glia is a change in the spectrum of secreted cytokines towards a more anti-inflammatory spectrum. There are multiple mechanisms that can control the level or activity of UCP2, including a variety of metabolites and microRNAs. Understanding these mechanisms will be key to exploitingthe protective effects of UCP2 in therapies for multiple neurodegenerative conditions.

Exercise-induced hormesis and skeletal muscle health

Hormesis refers to the phenomenon that an exposure or repeated exposures of a toxin can elicit adaptive changes within the organism to resist to higher doses of toxin with reduced harm. Skeletal muscle shows considerable plasticity and adaptions in response to a single bout of acute exercise or chronic training, especially in antioxidant defense capacity and metabolic functions mainly due to remodeling of mitochondria. It has thus been hypothesized that contraction-induced production of reactive oxygen species (ROS) may stimulate the hormesis-like adaptations. Furthermore, there has been considerable evidence that select ROS such as hydrogen peroxide and nitric oxide, or even oxidatively degraded macromolecules, may serve as signaling molecules to stimulate such hermetic adaptations due to the activation of redox-sensitive signaling pathways. Recent research has highlighted the important role of nuclear factor (NF) κB, mitogen-activated protein kinase (MAPK), and peroxisome proliferator-activated receptor γ co-activator 1α (PGC-1α), along with other newly discovered signaling pathways, in some of the most vital biological functions such as mitochondrial biogenesis, antioxidant defense, inflammation, protein turnover, apoptosis, and autophagy. The inability of the cell to maintain proper redox signaling underlies mechanisms of biological aging, during which inflammatory and catabolic pathways prevail. Research evidence and mechanisms connecting exercise-induced hormesis and redox signaling are reviewed.

Cell Death and Heart Failure in Obesity: Role of Uncoupling Proteins

Metabolic diseases such as obesity, metabolic syndrome, and type II diabetes are often characterized by increased reactive oxygen species (ROS) generation in mitochondrial respiratory complexes, associated with fat accumulation in cardiomyocytes, skeletal muscle, and hepatocytes. Several rodents studies showed that lipid accumulation in cardiac myocytes produces lipotoxicity that causes apoptosis and leads to heart failure, a dynamic pathological process. Meanwhile, several tissues including cardiac tissue develop an adaptive mechanism against oxidative stress and lipotoxicity by overexpressing uncoupling proteins (UCPs), specific mitochondrial membrane proteins. In heart from rodent and human with obesity, UCP2 and UCP3 may protect cardiomyocytes from death and from a state progressing to heart failure by downregulating programmed cell death. UCP activation may affect cytochrome c and proapoptotic protein release from mitochondria by reducing ROS generation and apoptotic cell death. Therefore the aim of this review is to discuss recent findings regarding the role that UCPs play in cardiomyocyte survival by protecting against ROS generation and maintaining bioenergetic metabolism homeostasis to promote heart protection.

Asiatic acid uncouples respiration in isolated mouse liver mitochondria and induces HepG2 cells death

Asiatic acid, one of the triterpenoid components isolated from Centella asiatica, has received increasing attention due to a wide variety of biological activities. To date, little is known about its mechanisms of action. Here we examined the cytotoxic effect of asiatic acid on HepG2 cells and elucidated some of the underlying mechanisms. Asiatic acid induced rapid cell death, as well as mitochondrial membrane potential (MMP) dissipation, ATP depletion and cytochrome c release from mitochondria to the cytosol in HepG2 cells. In mitochondria isolated from mouse liver, asiatic acid treatment significantly stimulated the succinate-supported state 4 respiration rate, dissipated the MMP, increased Ca(2+) release from Ca(2+)-loaded mitochondria, decreased ATP content and promoted cytochrome c release, indicating the uncoupling effect of asiatic acid. Hydrogen peroxide (H2O2) produced by succinate-supported mitochondrial respiration was also significantly inhibited by asiatic acid. In addition, asiatic acid inhibited Ca(2+)-induced mitochondrial swelling but did not induce mitochondrial swelling in hyposmotic potassium acetate medium which suggested that asiatic acid may not act as a protonophoric uncoupler. Inhibition of uncoupling proteins (UCPs) or blockade of adenine nucleotide transporter (ANT) attenuated the effect of asiatic acid on MMP dissipation, Ca(2+) release, mitochondrial respiration and HepG2 cell death. When combined inhibition of UCPs and ANT, asiatic acid-mediated uncoupling effect was noticeably alleviated. These results suggested that both UCPs and ANT partially contribute to the uncoupling properties of asiatic acid. In conclusion, asiatic acid is a novel mitochondrial uncoupler and this property is potentially involved in its toxicity on HepG2 cells.

Dynamic regulation of uncoupling protein 2 expression by microRNA-214 in hepatocellular carcinoma

Gemcitabine (GEM), a commonly used chemotherapeutic agent in hepatocellular carcinoma (HCC) patients, uses oxidative stress induction as a common effector pathway. However, GEM alone or in combination with oxaliplatin hardly renders any survival benefits to HCC patients. We have recently shown that this is part due to the overexpression of the mitochondrial uncoupling protein 2 (UCP2) that in turn mediates resistance to GEM in HCC patients. However, not much is known about regulatory mechanisms underlying UCP2 overexpression in HCC. Differential protein expression in HCC cell lines did not show a concomitant change in UCP2 transcript level, indicating post-transcriptional or post-translational regulatory mechanism. In situ analysis revealed that UCP2 is a putative target of miR-214 miR-214 expression is significantly down-regulated in HCC patient samples as compared with normal adjacent tissues and in cell line, human hepatoblastoma cells (HuH6), with high UCP2 protein expression. We demonstrated using miR-214 mimic and antagomir that the miRNA targeted UCP2 expression by directly targeting the wild-type, but not a miR-214 seed mutant, 3' UTR of UCP2 Overexpression of miR-214 significantly attenuated cell proliferation. Finally, analysis in 20 HCC patients revealed an inverse correlation in expression of UCP2 and miR-214 (Pearson's correlation coefficient, r=-0.9792). Cumulatively, our data indicate that in the context of HCC, miR-214 acts as a putative tumour suppressor by targeting UCP2 and defines a novel mechanism of regulation of UCP2.

PPARγ Inhibits VSMC Proliferation and Migration via Attenuating Oxidative Stress through Upregulating UCP2

Increasing evidence showed that abnormal proliferation and migration of vascular smooth muscle cells (VSMCs) are common event in the pathophysiology of many vascular diseases, including atherosclerosis and restenosis after angioplasty. Among the underlying mechanisms, oxidative stress is one of the principal contributors to the proliferation and migration of VSMCs. Oxidative stress occurs as a result of persistent production of reactive oxygen species (ROS). Recently, the protective effects of peroxisome proliferator-activated receptor γ (PPARγ) against oxidative stress/ROS in other cell types provide new insights to inhibit the suggests that PPARγ may regulate VSMCs function. However, it remains unclear whether activation of PPARγ can attenuate oxidative stress and further inhibit VSMC proliferation and migration. In this study, we therefore investigated the effect of PPARγ on inhibiting VSMC oxidative stress and the capability of proliferation and migration, and the potential role of mitochondrial uncoupling protein 2 (UCP2) in oxidative stress. It was found that platelet derived growth factor-BB (PDGF-BB) induced VSMC proliferation and migration as well as ROS production; PPARγ inhibited PDGF-BB-induced VSMC proliferation, migration and oxidative stress; PPARγ activation upregulated UCP2 expression in VSMCs; PPARγ inhibited PDGF-BB-induced ROS in VSMCs by upregulating UCP2 expression; PPARγ ameliorated injury-induced oxidative stress and intimal hyperplasia (IH) in UCP2-dependent manner. In conclusion, our study provides evidence that activation of PPARγ can attenuate ROS and VSMC proliferation and migration by upregulating UCP2 expression, and thus inhibit IH following carotid injury. These findings suggest PPARγ may represent a prospective target for the prevention and treatment of IH-associated vascular diseases.

The Role of Uncoupling Protein 2 During Myocardial Dysfunction in a Canine Model of Endotoxin Shock

To explore the role of uncoupling protein 2 (UCP2) during myocardial dysfunction in a canine model of endotoxin shock, 26 mongrel canines were randomly divided into the following four groups: A (control group; n = 6), B2 (shock after 2 h; n = 7), B4 (shock after 4 h; n = 7), and B6 (shock after 6 h; n = 6). Escherichia coli endotoxin was injected into the canines via the central vein, and hemodynamics were monitored. Energy metabolism, UCP2 mRNA and protein expression, and UCP2 localization were analyzed, and the correlation between energy metabolism changes, and UCP2 expression was determined. After the canine endotoxin shock model was successfully established, the expression of UCP2 mRNA and protein was found to increase, with later time points showing significant increases (P < 0.05). Immunofluorescence assays of UCP2 in heart tissue showed that UCP2 was localized in the cytoplasm, and its expression pattern was the same as that found in the mRNA and protein analyses. The energy metabolism results revealed that the ADP levels increased, but the ATP and phosphocreatine (PCr) levels and ATP/ADP and PCr/ATP ratios decreased in the model. In particular, the PCr/ATP ratio was significantly different from that of the control group 6 h after shock (P < 0.05). Furthermore, correlation analysis showed that the UCP2 protein and mRNA levels were negatively correlated with myocardial energy levels. In summary, decreased energy synthesis can occur in the myocardium during endotoxin shock, and UCP2 may play an important role in this process. The negative correlation between UCP2 expression and energy metabolism requires further study, as the results might contribute to the treatment of sepsis with heart failure.

A functional NMR for membrane proteins: dynamics, ligand binding, and allosteric modulation

By nature of conducting ions, transporting substrates and transducing signals, membrane channels, transporters and receptors are expected to exhibit intrinsic conformational dynamics. It is therefore of great interest and importance to understand the various properties of conformational dynamics acquired by these proteins, for example, the relative population of states, exchange rate, conformations of multiple states, and how small molecule ligands modulate the conformational exchange. Because small molecule binding to membrane proteins can be weak and/or dynamic, structural characterization of these effects is very challenging. This review describes several NMR studies of membrane protein dynamics, ligand-induced conformational rearrangements, and the effect of ligand binding on the equilibrium of conformational exchange. The functional significance of the observed phenomena is discussed.

The Role of Mitochondrial Functional Proteins in ROS Production in Ischemic Heart Diseases

Ischemic heart diseases (IHD) have become the leading cause of death around the world, killing more than 7 million people annually. In IHD, the blockage of coronary vessels will cause irreversible cell injury and even death. As the “powerhouse” and “apoptosis center” in cardiomyocytes, mitochondria play critical roles in IHD. Ischemia insult can reduce myocardial ATP content, resulting in energy stress and overproduction of reactive oxygen species (ROS). Thus, mitochondrial abnormality has been identified as a hallmark of multiple cardiovascular disorders. To date, many studies have suggested that these mitochondrial proteins, such as electron transport chain (ETC) complexes, uncoupling proteins (UCPs), mitochondrial dynamic proteins, translocases of outer membrane (Tom) complex, and mitochondrial permeability transition pore (MPTP), can directly or indirectly influence mitochondria-originated ROS production, consequently determining the degree of mitochondrial dysfunction and myocardial impairment. Here, the focus of this review is to summarize the present understanding of the relationship between some mitochondrial functional proteins and ROS production in IHD.

Insulin-like growth factor 1 (IGF-1) therapy: Mitochondrial dysfunction and diseases

This review resumes the association between mitochondrial function and diseases, especially neurodegenerative diseases. Additionally, it summarizes the major role of IGF-1 as a mitochondrial protector, as studied in several experimental models (cirrhosis, aging …). The contribution of mitochondrial dysfunction to impairments in insulin metabolic signaling is also suggested by gene array analysis showing that reductions in gene expression, that regulates mitochondrial ATP production, are associated with insulin resistance and type 2 diabetes mellitus. Moreover, reductions in oxidative capacity of mitochondrial electron transport chain are manifested in obese, insulin-resistant and diabetic patients. Genetic and environmental factors, oxidative stress, and alterations in mitochondrial biogenesis can adversely affect mitochondrial function, leading to insulin resistance and several pathological conditions, such as type 2 diabetes. Finally, it remains essential to know the exact mechanisms involved in mitochondrial generation and metabolism, mitophagy, apoptosis, and oxidative stress to establish new targets in order to develop potentially effective therapies. One of the newest targets to recover mitochondrial dysfunction could be the administration of IGF-1 at low doses. In the last years, it has been observed that IGF-1 therapy has several beneficial effects: restores physiological IGF-1 levels; improves insulin resistance and lipid metabolism; exerts mitochondrial protection; and has hepatoprotective, neuroprotective, antioxidant and antifibrogenic effects. In consequence, treatment of mitochondrial dysfunctions with low doses of IGF-1 could be a powerful and useful effective therapy to restore normal mitochondrial functions.

Single nucleotide polymorphisms linked to mitochondrial uncoupling protein genes UCP2 and UCP3 affect mitochondrial metabolism and healthy aging in female nonagenarians

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.

Diet-induced obesity and insulin resistance are associated with brown fat degeneration in SIRT1-deficient mice

OBJECTIVE

Recent studies have revealed that SIRT1 gain-of-function could promote adipose tissue browning for the adaptive thermogenesis under normal diet. This study investigated the role of SIRT1 loss-of-function in diet-induced obesity and insulin resistance and the mechanism involved in adipose tissue thermogenesis.

METHODS

Male SIRT1(+/-) and wild-type (WT) mice were fed with a high-fat diet (HFD) for 16 weeks to induce obesity and insulin resistance, while mice on a chow diet were used as lean controls. The phenotype data were collected, and different adipose tissue depots were used for mechanism research.

RESULTS

Compared with WT mice, SIRT1(+/-) mice exhibited increased adiposity and more severe insulin resistance with less thermogenesis under HFD challenge. Strikingly, SIRT1(+/-) mice displayed an exacerbated brown adipose tissue (BAT) degeneration phenotype, which was characterized by lower thermogenic activity, aggravated mitochondrial dysfunction, and more mitochondrial loss. In addition, SIRT1(+/-) mice showed aggravated inflammation and dysfunction in epididymal adipose tissue after HFD intervention, which also contributed to the systemic insulin resistance.

CONCLUSIONS

Diet-induced obesity and insulin resistance are associated with BAT degeneration in SIRT1-deficient mice, which further underlined the beneficial role of SIRT1 in obesity-associated metabolic disorders.

UCP3 is associated with Hax-1 in mitochondria in the presence of calcium ion

Uncoupling protein 3 (UCP3) is known to regulate energy dissipation, proton leakage, fatty acid oxidation, and oxidative stress. To identify the putative protein regulators of UCP3, we performed yeast two-hybrid screens. Here we report that UCP3 interacted with HS-1 associated protein X-1 (Hax-1), an anti-apoptotic protein that was localized in the mitochondria, and is involved in cellular responses to Ca(2+). The hydrophilic sequences within loop 2, and the matrix-localized hydrophilic domain of mouse UCP3, were necessary for binding to Hax-1 at the C-terminal domain, adjacent to the mitochondrial inner membrane. Interestingly, interaction of these proteins occurred in a calcium-dependent manner. Moreover, the NMR spectrum of the C-terminal domain of Hax-1 was dramatically changed by removal of Ca(2+), suggesting that the C-terminal domain of Hax-1 underwent a Ca(2+)-induced conformational change. In the Ca(2+)-free state, the C-terminal Hax-1 tended to unfold, suggesting that Ca(2+) binding may induce protein folding of the Hax-1 C-terminus. These results suggested that the UCP3-Hax-1 complex may regulate mitochondrial functional changes caused by mitochondrial Ca(2+).

The Ablation of Mitochondrial Protein Phosphatase Pgam5 Confers Resistance Against Metabolic Stress

Phosphoglycerate mutase family member 5 (PGAM5) is a mitochondrial protein phosphatase that has been reported to be involved in various stress responses from mitochondrial quality control to cell death. However, its roles in vivo are largely unknown. Here, we show that Pgam5-deficient mice are resistant to several metabolic insults. Under cold stress combined with fasting, Pgam5-deficient mice better maintained body temperature than wild-type mice and showed an extended survival rate. Serum triglycerides and lipid content in brown adipose tissue (BAT), a center of adaptive thermogenesis, were severely reduced in Pgam5-deficient mice. Moreover, although Pgam5 deficiency failed to maintain proper mitochondrial integrity in BAT, it reciprocally resulted in the dramatic induction of fibroblast growth factor 21 (FGF21) that activates various functions of BAT including thermogenesis. Thus, the enhancement of lipid metabolism and FGF21 may contribute to the cold resistance of Pgam5-deficient mice under fasting condition. Finally, we also found that Pgam5-deficient mice are resistant to high-fat-diet-induced obesity. Our study uncovered that PGAM5 is involved in the whole-body metabolism in response to stresses that impose metabolic challenges on mitochondria.

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The ablation of Pgam5, a mitochondria-resident protein phosphatase, protected mice from some metabolic stresses.

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Pgam5-deficient mice were resistant to a cold plus fasting stress and a high fat diet-induced obesity.

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Our study revealed that PGAM5 acts as a metabolic regulator in vivo.

Here, we revealed that the ablation of Pgam5, a mitochondria-resident protein phosphatase, protects mice from some metabolic stresses. When fasted mice were exposed to cold condition, Pgam5 deficiency promoted the lipid metabolism and the expression of metabolic hormone FGF21 in brown adipose tissue, a center of heat production, suggesting that these metabolic changes might ultimately contribute to their resistance. In addition, we found that Pgam5-deficient mice were dramatically resistant to high-fat diet-induced obesity. Our study not only provides the evidence that PGAM5 acts as a metabolic regulator in vivo but also raises the potential therapeutic target for metabolic diseases.

Effects of intratracheally instilled laser printer-emitted engineered nanoparticles in a mouse model: A case study of toxicological implications from nanomaterials released during consumer use

Incorporation of engineered nanomaterials (ENMs) into toners used in laser printers has led to countless quality and performance improvements. However, the release of ENMs during printing (consumer use) has raised concerns about their potential adverse health effects. The aim of this study was to use "real world" printer-emitted particles (PEPs), rather than raw toner powder, and assess the pulmonary responses following exposure by intratracheal instillation. Nine-week old male Balb/c mice were exposed to various doses of PEPs (0.5, 2.5 and 5 mg/kg body weight) by intratracheal instillation. These exposure doses are comparable to real world human inhalation exposures ranging from 13.7 to 141.9 h of printing. Toxicological parameters reflecting distinct mechanisms of action were evaluated, including lung membrane integrity, inflammation and regulation of DNA methylation patterns. Results from this in vivo toxicological analysis showed that while intratracheal instillation of PEPs caused no changes in the lung membrane integrity, there was a pulmonary immune response, indicated by an elevation in neutrophil and macrophage percentage over the vehicle control and low dose PEPs groups. Additionally, exposure to PEPs upregulated expression of the Ccl5 (Rantes), Nos1 and Ucp2 genes in the murine lung tissue and modified components of the DNA methylation machinery (Dnmt3a) and expression of transposable element (TE) LINE-1 compared to the control group. These genes are involved in both the repair process from oxidative damage and the initiation of immune responses to foreign pathogens. The results are in agreement with findings from previous in vitro cellular studies and suggest that PEPs may cause immune responses in addition to modifications in gene expression in the murine lung at doses that can be comparable to real world exposure scenarios, thereby raising concerns of deleterious health effects.

Overexpression of mitochondrial uncoupling protein 1 (UCP1) induces a hypoxic response in Nicotiana tabacum leaves

Mitochondrial uncoupling protein 1 (UCP1) decreases reactive oxygen species production under stress conditions by uncoupling the electrochemical gradient from ATP synthesis. This study combined transcriptome profiling with experimentally induced hypoxia to mechanistically dissect the impact of Arabidopsis thaliana UCP1 (AtUCP1) overexpression in tobacco. Transcriptomic analysis of AtUCP1-overexpressing (P07) and wild-type (WT) plants was carried out using RNA sequencing. Metabolite and carbohydrate profiling of hypoxia-treated plants was performed using (1)H-nuclear magnetic resonance spectroscopy and high-performance anion-exchange chromatography with pulsed amperometric detection. The transcriptome of P07 plants revealed a broad induction of stress-responsive genes that were not strictly related to the mitochondrial antioxidant machinery, suggesting that overexpression of AtUCP1 imposes a strong stress response within the cell. In addition, transcripts that mapped into carbon fixation and energy expenditure pathways were broadly altered. It was found that metabolite markers of hypoxic adaptation, such as alanine and tricarboxylic acid intermediates, accumulated in P07 plants under control conditions at similar rates to WT plants under hypoxia. These findings indicate that constitutive overexpression of AtUCP1 induces a hypoxic response. The metabolites that accumulated in P07 plants are believed to be important in signalling for an improvement in carbon assimilation and induction of a hypoxic response. Under these conditions, mitochondrial ATP production is less necessary and fermentative glycolysis becomes critical to meet cell energy demands. In this scenario, the more flexible energy metabolism along with an intrinsically activated hypoxic response make these plants better adapted to face several biotic and abiotic stresses.

Mitochondrial oxidative metabolism and uncoupling proteins in the failing heart

Despite significant progress in cardiovascular medicine, myocardial ischemia and infarction, progressing eventually to the final end point heart failure (HF), remain the leading cause of morbidity and mortality in the USA. HF is a complex syndrome that results from any structural or functional impairment in ventricular filling or blood ejection. Ultimately, the heart's inability to supply the body's tissues with enough blood may lead to death. Mechanistically, the hallmarks of the failing heart include abnormal energy metabolism, increased production of reactive oxygen species (ROS) and defects in excitation-contraction coupling. HF is a highly dynamic pathological process, and observed alterations in cardiac metabolism and function depend on the disease progression. In the early stages, cardiac remodeling characterized by normal or slightly increased fatty acid (FA) oxidation plays a compensatory, cardioprotective role. However, upon progression of HF, FA oxidation and mitochondrial oxidative activity are decreased, resulting in a significant drop in cardiac ATP levels. In HF, as a compensatory response to decreased oxidative metabolism, glucose uptake and glycolysis are upregulated, but this upregulation is not sufficient to compensate for a drop in ATP production. Elevated mitochondrial ROS generation and ROS-mediated damage, when they overwhelm the cellular antioxidant defense system, induce heart injury and contribute to the progression of HF. Mitochondrial uncoupling proteins (UCPs), which promote proton leak across the inner mitochondrial membrane, have emerged as essential regulators of mitochondrial membrane potential, respiratory activity and ROS generation. Although the physiological role of UCP2 and UCP3, expressed in the heart, has not been clearly established, increasing evidence suggests that these proteins by promoting mild uncoupling could reduce mitochondrial ROS generation and cardiomyocyte apoptosis and ameliorate thereby myocardial function. Further investigation on the alterations in cardiac UCP activity and regulation will advance our understanding of their physiological roles in the healthy and diseased heart and also may facilitate the development of novel and more efficient therapies.

Protective Effect of Peroxisome Proliferator-Activated Receptor α Activation against Cardiac Ischemia-Reperfusion Injury Is Related to Upregulation of Uncoupling Protein-3

Activation of peroxisome proliferator-activated receptor α (PPARα) confers cardioprotection, while its mechanism remains elusive. We investigated the protective effect of PPARα activation against cardiac ischemia-reperfusion injury in terms of the expression of uncoupling protein (UCP). Myocardial infarct size and UCP expression were measured in rats treated with WY-14643 20 mg/kg, a PPARα ligand, or vehicle. WY-14643 increased UCP3 expression in vivo. Myocardial infarct size was decreased in the WY-14643 group (76 ± 8% versus 42 ± 12%, P<0.05). During reperfusion, the incidence of arrhythmia was higher in the control group compared with the WY-14643 group (9/10 versus 3/10, P<0.05). H9c2 cells were incubated for 24 h with WY-14643 or vehicle. WY-14643 increased UCP3 expression in H9c2 cells. WY-14643 decreased hypoxia-stimulated ROS production. Cells treated with WY-14643 were more resistant to hypoxia-reoxygenation than the untreated cells. Knocking-down UCP3 by siRNA prevented WY-14643 from attenuating the production of ROS. UCP3 siRNA abolished the effect of WY-14643 on cell viability against hypoxia-reoxygenation. In summary, administration of PPARα agonist WY-14643 mitigated the extent of myocardial infarction and incidence of reperfusion-induced arrhythmia. PPARα activation conferred cytoprotective effect against hypoxia-reoxygenation. Associated mechanisms involved increased UCP3 expression and resultant attenuation of ROS production.

Interactions between uncoupling protein 2 gene polymorphisms, obesity and alcohol intake on liver function: a large meta-analysed population-based study

BACKGROUND AND OBJECTIVE

Given the role of uncoupling protein 2 (UCP2) in the accumulation of fat in the hepatocytes and in the enhancement of protective mechanisms in acute ethanol intake, we hypothesised that UCP2 polymorphisms are likely to cause liver disease through their interactions with obesity and alcohol intake. To test this hypothesis, we investigated the interaction between tagging polymorphisms in the UCP2 gene (rs2306819, rs599277 and rs659366), alcohol intake and obesity traits such as BMI and waist circumference (WC) on alanine aminotransferase (ALT) and gamma glutamyl transferase (GGT) in a large meta-analysis of data sets from three populations (n=20 242).

DESIGN AND METHODS

The study populations included the Northern Finland Birth Cohort 1966 (n=4996), Netherlands Study of Depression and Anxiety (n=1883) and LifeLines Cohort Study (n=13 363). Interactions between the polymorphisms and obesity and alcohol intake on dichotomised ALT and GGT levels were assessed using logistic regression and the likelihood ratio test.

RESULTS

In the meta-analysis of the three cohorts, none of the three UCP2 polymorphisms were associated with GGT or ALT levels. There was no evidence for interaction between the polymorphisms and alcohol intake on GGT and ALT levels. In contrast, the association of WC and BMI with GGT levels varied by rs659366 genotype (Pinteraction=0.03 and 0.007, respectively; adjusted for age, gender, high alcohol intake, diabetes, hypertension and serum lipid concentrations).

CONCLUSION

In conclusion, our findings in 20 242 individuals suggest that UCP2 gene polymorphisms may cause liver dysfunction through the interaction with body fat rather than alcohol intake.