Transcriptional Coactivator PGC-1α Research Articles

238-LB: Cold-Dependent Regulation of GOT1 Activity in Brown Adipose Tissue and Its Effect on Thermogenesis

The malate-aspartate shuttle (MAS) is a biochemical system that can transfer electrons from cytosolic NADH to the mitochondrial electron transport chain. The MAS regulates various biological processes in a tissue-specific manner, but its function in brown adipose tissue (BAT) thermogenesis has not been investigated. We found that glutamic-oxaloacetic transaminase 1 (GOT1), one of the key MAS enzymes, exists at very low levels in BAT but is markedly induced during cold exposure or pharmacological stimulation of β3-adrenergic receptors (β3AR) while other MAS enzymes (GOT2 and MDH1/2) remain unchanged. Our studies showed that cold-activated transcriptional coactivator PGC-1α and its splice variant NT-PGC-1α were recruited to the Got1 promoter at the estrogen-related receptor response element (ERRE), leading to an increase in Got1 gene expression. Moreover, GOT1 protein stability was increased by reduced targeting to the proteasomal degradation. BAT-specific overexpression of Got1 in mice by using the Cre-loxP system increased energy expenditure at room temperature and improved BAT theromogeneis upon cold exposure or β3-adrenergic stimulation. Collectively, our data suggest that the β3AR-FL/NT-PGC-1α-GOT1 axis enhances BAT activity through the activation of the malate-aspartate shuttle. Disclosure C. Park: None. J. Chang: None.

Exploring the signal-dependent transcriptional regulation involved in the liver pathology of type 2 diabetes.

Excess glucagon activity in diabetes increases hepatic glucose production via gluconeogenic gene induction, thus exacerbating hyperglycemia. Glucagon receptor-activated cAMP-dependent protein kinase A (PKA) induces proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) expression via the cAMP response element-binding protein (CREB)-regulated transcription coactivator 2 (CRTC2) pathway. Transcriptional coactivator PGC-1α subsequently coactivates transcription factors, such as forkhead box O1 (FoxO1) and hepatocyte nuclear factor 4 alpha (HNF4α), to induce gluconeogenic genes. The current review first summarizes the mechanism by which transcriptional cofactor CBP and p300-activated transactivator with glutamic acid and aspartic acid-rich COOH-terminal domain 2 (CITED2) activates gluconeogenesis via the regulation of PGC-1α and general control of amino acid synthesis protein 5-like 2 (GCN5). Type 2 diabetes is closely linked with non-alcoholic fatty liver disease (NAFLD). Between 10 and 20% of NAFLD progresses to non-alcoholic steatohepatitis (NASH), which can cause liver cirrhosis and can also lead to hepatocellular carcinoma. Liver macrophages are considered to be related to inflammation and fibrosis observed in NASH. This review outlines liver-derived signals underlying the differentiation of liver macrophages and the mechanism of myeloid cell diversification in NASH.

OR19-2 Treatment of Heart Failure with Preserved Ejection Fraction (HFpEF) with Low and High Dose of Triiodothyronine: an Animal Model of Metabolic Syndrome with HFpEF

Abstract Introduction Low levels of triiodothyronine (T3) are common in patients with heart failure (HF). It has been proposed that the decreased levels of T3 contribute to metabolic and cardiac dysfunction in HF. We aimed to evaluate the effects of treatment with low dose and high dose of T3 in an animal model of HF with preserved ejection fraction (HFpEF). Materials and Methods We evaluated four groups: ZSF1 Lean (Lean-Ctrl, n=8), ZSF1 obese (rat model of metabolic syndrome with HFpEF, HFpEF-Ctrl, n=13), ZSF1 obese supplemented with a replacement dose of T3 (initially 0.04mg/ml, increased to 0.06mg/ml after 4 weeks; HFpEF-T3high, n=8), and ZSF1 Obese supplemented with a low-dose of T3 (0.03mg/mL; HFpEF-T3low, n=8). T3 was supplemented in drinking water from week 13 to 24. The animals were submitted to anthropometric and metabolic evaluation, echocardiography, VO2max evaluation, hemodynamic evaluation, single cardiomyocyte evaluation, and myocardial tissue collection at 24 weeks. Results HFpEF-Ctrl animals had lower serum and myocardial thyroid hormone levels than Lean-Ctrl. Treatment with low dose and high dose of T3 did not correct serum T3 levels, but increased myocardial T3 levels, with normalization of myocardial T3 levels in the HFpEF-T3high group. In comparison to HFpEF-Ctrl, body weight was significantly decreased in HFpEF-T3low and HFpEF-T3high groups (616±39g, 572±24g and 535±18g respectively, p<0.001). An improvement in glucose metabolism was observed only in HFpEF-T3high, with a decreased AUC of glucose during OGTT and insulin tolerance test. Both treated groups presented an improvement in diastolic function (with decreased isovolumetric relaxation time) and systolic function (with increased peak systolic velocity and decreased ejection time) comparing to HFpEF-Ctrl. These results were supported by enhanced Ca2+ transients during diastole and sarcomere relaxation. Comparing with HFpEF-Ctrl, animals treated with T3 had higher myocardial expression of the calcium transporter RYR2, of the transcriptional coactivator PGC-1α, and of the α-myosin heavy chain (MHC), with a lower expression of β-MHC. VO2max was improved with low-dose and high-dose T3 compared with HFpEF-Ctrl. Comparing with HFpEF-Ctrl, heart rate was increased with high-dose (277.9±30.2 vs 313.5±35.8, p=0.049) but not significantly with low-dose (277.9±30.2 vs 299.8±30.9 bpm, p=0.13). Mortality was increased in the HFpEF-T3high comparing with the other groups (no animals died during the protocol in the Lean-Ctrl, HFpEF-Ctrl and HFpEF-T3low groups; three animals had sudden death in the HFpEF-T3high group). Conclusion Treatment with T3 improves metabolic function, myocardial calcium handling, diastolic and systolic function, and exercise capacity in this animal model of HFpEF. While the low dose was well tolerated and safe, the high dose was associated with increased heart rate and a higher risk of sudden death. Modulation of thyroid hormones may be a potential therapeutic target in HFpEF; however such approaches must take into account a narrow therapeutic window of T3 in HFpEF. Presentation: Monday, June 13, 2022 11:15 p.m. - 11:30 a.m.

PGC-1α4 Interacts with REST to Upregulate Neuronal Genes and Augment Energy Consumption in Developing Cardiomyocytes.

Transcriptional coactivator PGC-1α is a main regulator of cardiac energy metabolism. In addition to canonical PGC-1α1, other PGC-1α isoforms have been found to exert specific biological functions in a variety of tissues. We investigated the expression patterns and the biological effects of the non-canonical isoforms in the heart. We used RNA sequencing data to identify the expression patterns of PGC-1α isoforms in the heart. To evaluate the biological effects of the alternative isoform expression, we generated a transgenic mouse with cardiac-specific overexpression of PGC-1α4 and analysed the cardiac phenotype with a wide spectrum of physiological and biophysical tools. Our results show that non-canonical isoforms are expressed in the heart, and that the main variant PGC-1α4 is induced by β-adrenergic signalling in adult cardiomyocytes. Cardiomyocyte specific PGC-1α4 overexpression in mice relieves the RE1-Silencing Transcription factor (REST)-mediated suppression of neuronal genes during foetal heart development. The resulting de-repression of REST target genes induces a cardiac phenotype with increased cellular energy consumption, resulting in postnatal dilated cardiomyopathy. These results propose a new concept for actions of the PGC-1α protein family where activation of the Pgc-1α gene, through its isoforms, induces a phenotype with concurrent supply and demand for cellular energy. These data highlight the biological roles of the different PGC-1α isoforms, which should be considered when future therapies are developed.

Enhancement of anaerobic glycolysis \u2013 a role of PGC-1\u03b14 in resistance exercise

Resistance exercise training (RET) is an effective countermeasure to sarcopenia, related frailty and metabolic disorders. Here, we show that an RET-induced increase in PGC-1α4 (an isoform of the transcriptional co-activator PGC-1α) expression not only promotes muscle hypertrophy but also enhances glycolysis, providing a rapid supply of ATP for muscle contractions. In human skeletal muscle, PGC-1α4 binds to the nuclear receptor PPARβ following RET, resulting in downstream effects on the expressions of key glycolytic genes. In myotubes, we show that PGC-1α4 overexpression increases anaerobic glycolysis in a PPARβ-dependent manner and promotes muscle glucose uptake and fat oxidation. In contrast, we found that an acute resistance exercise bout activates glycolysis in an AMPK-dependent manner. These results provide a mechanistic link between RET and improved glucose metabolism, offering an important therapeutic target to counteract aging and inactivity-induced metabolic diseases benefitting those who cannot exercise due to many reasons.

Transcriptional coactivator PGC-1α contributes to decidualization by forming a histone-modifying complex with C/EBPβ and p300

We previously reported that CCAAT/enhancer-binding protein beta (C/EBPβ) is the pioneer factor inducing transcription enhancer mark H3K27 acetylation (H3K27ac) in the promoter and enhancer regions of genes encoding insulin-like growth factor–binding protein-1 (IGFBP-1) and prolactin (PRL) and that this contributes to decidualization of human endometrial stromal cells (ESCs). Peroxisome proliferator–activated receptor gamma coactivator 1-alpha (PGC-1α; PPARGC1A) is a transcriptional coactivator known to regulate H3K27ac. However, although PGC-1α is expressed in ESCs, the potential role of PGC-1α in mediating decidualization is unclear. Here, we investigated the involvement of PGC-1α in the regulation of decidualization. We incubated ESCs with cAMP to induce decidualization and knocked down PPARGC1A to inhibit cAMP-induced expression of IGFBP-1 and PRL. We found cAMP increased the recruitment of PGC-1α and p300 to C/EBPβ-binding sites in the promoter and enhancer regions of IGFBP-1 and PRL, corresponding with increases in H3K27ac. Moreover, PGC-1α knockdown inhibited these increases, suggesting PGC-1α forms a histone-modifying complex with C/EBPβ and p300 at these regions. To further investigate the regulation of PGC-1α, we focused on C/EBPβ upstream of PGC-1α. We found cAMP increased C/EBPβ recruitment to the novel enhancer regions of PPARGC1A. Deletion of these enhancers decreased PGC-1α expression, indicating that C/EBPβ upregulates PGC-1α expression by binding to novel enhancer regions. In conclusion, PGC-1α is upregulated by C/EBPβ recruitment to novel enhancers and contributes to decidualization by forming a histone-modifying complex with C/EBPβ and p300, thereby inducing epigenomic changes in the promoters and enhancers of IGFBP-1 and PRL.

Pharmacologic induction of PGC-1α stimulates fetal haemoglobin gene expression.

Sickle cell disease (SCD) is a genetic disorder that affects millions around the world. Enhancement of fetal γ-globin levels and fetal haemoglobin (HbF) production in SCD patients leads to diminished severity of many clinical features of the disease. We recently identified the transcriptional co-activator PGC-1α as a new protein involved in the regulation of the globin genes. Here, we report that upregulation of PGC-1α by infection with a lentivirus expressing PGC-1α or by the small-molecule PGC-1α agonist ZLN005 in human primary erythroid progenitor CD34+ cells induces both fetal γ-globin mRNA and protein expression as well as the percentage of HbF-positive cell (F cells) without significantly affecting cell proliferation and differentiation. We further found that the combination of ZLN005 and hydroxyurea (hydroxycarbamide) exhibited an additive effect on the expression of γ-globin and the generation of F cells from cultured CD34+ cells. In addition, ZLN005 induced robust expression of the murine embryonic βh1-globin gene and to a lesser extent, human γ-globin gene expression in sickle mice. These findings suggest that activation of PGC-1α by ZLN005 might provide a new path for modulating HbF levels with potential therapeutic benefit in β-hemoglobinopathies.

Elucidating exercise-induced skeletal muscle signaling pathways and applying relevant findings to preemptive therapy for lifestyle-related diseases.

While it is well recognized that exercise represents a radical preventive and therapeutic measure for lifestyle-related diseases, it is clear that contemporary lifestyles abound with situations where exercise may be found difficult to implement on a continuous basis. Indeed, this has led to global expectations for elucidation of the exercise-activated skeletal muscle signaling pathways as well as for development of exercise mimics that effectively activate such pathways. It is shown that exercise activates the transcriptional coactivator PGC-1α via AMPK/SIRT1 in muscle, thereby not only enhancing mitochondrial function and muscle endurance but upregulating energy metabolism. Further, adipocyte-derived adiponectin is also shown to activate AMPK/SIRT1/PGC-1α via its receptor AdipoR1 in skeletal muscles. Thus, adiponectin/AdipoR1 signaling is thought to constitute exercise-mimicking signaling. Indeed, it has become clear that AMPK, SIRT1 and AdipoR activators act as exercise mimetics. With the crystal structures of AdipoR elucidated and humanized AdipoR mice generated toward optimization of candidate AdipoR-activators for human use, expectations are mounting for the clinical application in the near future of AdipoR activators as exercise mimetics in humans. This review provides an overview of molecules activated by exercise and compounds activating these molecules, with a focus on the therapeutic potential of AdipoR activators as exercise mimetics.

PV-specific loss of the transcriptional coactivator PGC-1α slows down the evolution of epileptic activity in an acute ictogenic model.

The transcriptional coactivator, PGC-1α (peroxisome proliferator-activated receptor γ coactivator 1α), plays a key role in coordinating energy requirement within cells. Its importance is reflected in the growing number of psychiatric and neurological conditions that have been associated with reduced PGC-1α levels. In cortical networks, PGC-1α is required for the induction of parvalbumin (PV) expression in interneurons, and PGC-1α deficiency affects synchronous GABAergic release. It is unknown, however, how this affects cortical excitability. We show here that knocking down PGC-1α specifically in the PV-expressing cells (PGC-1αPV-/-) blocks the activity-dependent regulation of the synaptic proteins, SYT2 and CPLX1. More surprisingly, this cell class-specific knockout of PGC-1α appears to have a novel antiepileptic effect, as assayed in brain slices bathed in 0 Mg2+ media. The rate of occurrence of preictal discharges developed approximately equivalently in wild-type and PGC-1αPV-/- brain slices, but the intensity of these discharges was lower in PGC-1αPV-/- slices, as evident from the reduced power in the γ range and reduced firing rates in both PV interneurons and pyramidal cells during these discharges. Reflecting this reduced intensity in the preictal discharges, the PGC-1αPV-/- brain slices experienced many more discharges before transitioning into a seizure-like event. Consequently, there was a large increase in the latency to the first seizure-like event in brain slices lacking PGC-1α in PV interneurons. We conclude that knocking down PGC-1α limits the range of PV interneuron firing and this slows the pathophysiological escalation during ictogenesis.NEW & NOTEWORTHY Parvalbumin expressing interneurons are considered to play an important role in regulating cortical activity. We were surprised, therefore, to find that knocking down the transcriptional coactivator, PGC-1α, specifically in this class of interneurons appears to slow ictogenesis. This anti-ictogenic effect is associated with reduced activity in preictal discharges, but with a far longer period of these discharges before the first seizure-like events finally start. Thus, PGC-1α knockdown may promote schizophrenia while reducing epileptic tendencies.

Mitophagy mediates metabolic reprogramming of induced pluripotent stem cells undergoing endothelial differentiation

Pluripotent stem cells are known to shift their mitochondrial metabolism upon differentiation, but the mechanisms underlying such metabolic rewiring are not fully understood. We hypothesized that during differentiation of human induced pluripotent stem cells (hiPSCs), mitochondria undergo mitophagy and are then replenished by the biogenesis of new mitochondria adapted to the metabolic needs of the differentiated cell. To evaluate mitophagy during iPSC differentiation, we performed live cell imaging of mitochondria and lysosomes in hiPSCs differentiating into vascular endothelial cells using confocal microscopy. We observed a burst of mitophagy during the initial phases of hiPSC differentiation into the endothelial lineage, followed by subsequent mitochondrial biogenesis as assessed by the mitochondrial biogenesis biosensor MitoTimer. Furthermore, hiPSCs undergoing differentiation showed greater mitochondrial oxidation of fatty acids and an increase in ATP levels as assessed by an ATP biosensor. We also found that during mitophagy, the mitochondrial phosphatase PGAM5 is cleaved in hiPSC-derived endothelial progenitor cells and in turn activates β-catenin-mediated transcription of the transcriptional coactivator PGC-1α, which upregulates mitochondrial biogenesis. These data suggest that mitophagy itself initiates the increase in mitochondrial biogenesis and oxidative metabolism through transcriptional changes during endothelial cell differentiation. In summary, these findings reveal a mitophagy-mediated mechanism for metabolic rewiring and maturation of differentiating cells via the β-catenin signaling pathway. We propose that such mitochondrial-nuclear cross talk during hiPSC differentiation could be leveraged to enhance the metabolic maturation of differentiated cells.

Abstract 2595: Cancer cachexia is mediated by the suppression of PGC1-alpha expression in the skeletal muscle vasculature

Abstract Background: Cancer patients experience cachexia which is characterized by extensive skeletal muscle wasting that worsens the quality of life and increases mortality. However, there are no approved treatments that can effectively counteract cancer cachexia. Prior research has focused on the changes within the muscle tissue but little is known about the role of the muscle vasculature in mediating cancer cachexia. Vascular endothelial cells (ECs) are essential for maintaining tissue perfusion, nutrient supply and preventing inappropriate transmigration of immune cells into the tissue. We therefore hypothesized that endothelial dysfunction in the skeletal muscle results in the development of cachexia in cancer. The transcriptional co-activator PGC1α (peroxisome proliferation activator receptor-γ coactivator1-α) regulates endothelial health. Methods and Results: To evaluate whether skeletal muscle EC-PGC1α is modulated in the setting of malignancy, we isolated muscle ECs from control and melanoma bearing mice at 1, 2, and 3 weeks after melanoma implantation. PGC1α expression was significantly decreased in mECs of melanoma bearing mice from early stage (1 week) compared with control mice. Thus, we generated an EC-specific inducible PGC1α deletion mouse model (ECΔPGC1α) to investigate the mechanistic role of EC-PGC1α in cancer cachexia in vivo. Interestingly, vascular density and muscle area were significantly decreased in the gastrocnemius (GC) of ECΔPGC1α mice compared with ECWT mice using an innovative tissue clearing and high-resolution 3D-tissue imaging system. Tumor bearing ECWT mice had decreased GC mass and weight compared with no tumor mice by enhancing cachexia marker genes, MuRF1 and Atrogin1. The tumor bearing ECΔPGC1α mice had further decreased muscle mass and weight, and grip strength than tumor bearing ECWT mice. We assessed the role of EC-PGC1α in the regulation of capillary function in vivo, and observed that ECΔPGC1α mice demonstrated significantly greater vascular leak than ECWT mice. Conclusion: These data suggest that the presence of melanoma suppresses PGC1α expression in the skeletal muscle endothelium. Endothelial PGC1α, in turn, is essential for maintaining the integrity of the skeletal muscle vascular barrier. Our study suggests that restoring muscle endothelial dysfunction could be a novel therapeutic approach to prevent or reverse cancer cachexia. Citation Format: Young-Mee Kim, Georgina Mancinelli, Paul Grippo, Jalees Rehman. Cancer cachexia is mediated by the suppression of PGC1-alpha expression in the skeletal muscle vasculature [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2595.

Resveratrol-induced Sirt1 phosphorylation by LKB1 mediates mitochondrial metabolism

The NAD+-dependent deacetylase Sirt1 has been implicated in the prevention of many age-related diseases, including cancer, type 2 diabetes, and cardiovascular disease. Resveratrol, a plant polyphenol, exhibits antiaging, antitumor, and vascular protection effects by activating Sirt1. However, the molecular mechanism of Sirt1 activation as induced by resveratrol remains unclear. By knockdown/rescue experiments, fluorometric Sirt1 activity assay, immunoprecipitation, and pull-down assays, we identify here that the tumor suppressor LKB1 (liver kinase B1) as a direct activator of Sirt1 elicited by resveratrol. Resveratrol promotes the binding between LKB1 and Sirt1, which we first reported, and this binding leads to LKB1-mediated phosphorylation of Sirt1 at three different serine residues in the C terminus of Sirt1. Mechanistically, LKB1-mediated phosphorylation increases intramolecular interactions in Sirt1, such as the binding of the C terminus to the deacetylase core domain, thereby eliminating DBC1 (Deleted in Breast Cancer 1, Sirt1 endogenous inhibitor) inhibition and promoting Sirt1–substrate interaction. Functionally, LKB1-dependent Sirt1 activation increases mitochondrial biogenesis and respiration through deacetylation and activation of the transcriptional coactivator PGC-1α. These results identify Sirt1 as a context-dependent target of LKB1 and suggest that a resveratrol-stimulated LKB1-Sirt1 pathway plays a vital role in mitochondrial metabolism, a key physiological process that contributes to numerous age-related diseases.

PGC-1α deficiency reveals sex-specific links between cardiac energy metabolism and EC-coupling during development of heart failure in mice.

AimsBiological sex has fundamental effects on mammalian heart physiology and pathogenesis. While it has been established that female sex is a protective factor against most cardiovascular diseases (CVDs), this beneficial effect may involve pathways associated with cardiac energy metabolism. Our aim was to elucidate the role of transcriptional coactivator PGC-1α in sex dimorphism of heart failure (HF) development.Methods and resultsHere, we show that mice deficient in cardiac expression of the peroxisome proliferator-activated receptor gamma (PPAR-γ) coactivator-1α (PGC-1α) develop dilated HF associated with changes in aerobic and anaerobic metabolism, calcium handling, cell structure, electrophysiology, as well as gene expression. These cardiac changes occur in both sexes, but female mice develop an earlier and more severe structural and functional phenotype associated with dyssynchronous local calcium release resulting from disruption of t-tubular structures of the cardiomyocytes.ConclusionsThese data reveal that the integrity of the subcellular Ca2+ release and uptake machinery is dependent on energy metabolism and that female hearts are more prone to suffer from contractile dysfunction in conditions with compromised production of cellular energy. Furthermore, these findings suggest that PGC-1α is a central mediator of sex-specific differences in heart function and CVD susceptibility.

Acidic ambiance induced post-oxidative stress affects AMPK- PGC1α-SIRT1 axis in the skeletal muscles of zebrafish Danio rerio Hamilton, 1822

The present study was aimed to understand whether acidic pH induces oxidative stress in zebrafish affecting metabolic sensor protein and thereby, the mitochondrial functions in the skeletal muscle of zebrafish. The experiments performed in aquaria involved the study of the changes of HIF1α, AMPK, PGC1α and SIRT1 levels together with the levels of mitochondrial Tfam and Nrf1. The results obtained from investigation of superoxide dismutase (SOD), catalase and glutathione revealed that the fish undergoes oxidative stress within a short duration of exposure to acidic ambiance. Further analysis with MDA and HIF1α helped to understand the effects of post oxidative stress on skeletal muscle of the fish at pH 5.0 (± 0.5). Of the three tissues studied (gill, brain and skeletal muscle) the effect was maximum in skeletal muscle as depicted by MDA level at 2 hours beyond which it declines augmenting death or mortality (15%) to the fish. Consequently, HIF1α was increased as an adaptive strategy against metabolic disruption during the first 2 hours period. However, on exposure to pH 5.0 (± 0.5) for 2 hours, there were decrease of the metabolic sensors viz. AMPK and SIRT1 followed by mitochondrial gene transcriptional co-activator PGC1α. The expression of mitochon-drial transcription factors Tfam and Nrf1 were also reduced confirming perturbation in mitochondrial function affecting low ATP production compared to control. This was also supported by the decrease of COXII as well as mitochondrial complex I activity. All these results confirm that the metabolic machinery of zebrafish is affected when pH was lowered to 5.0 (± 0.5).

Glitazones, PPAR-γ and Neuroprotection.

The transcriptional factor PPAR-γ belongs to the nuclear receptor family, which has become a potential therapeutic target for several neurodegenerative diseases and metabolic disorders. Interestingly, PPAR-γ has been reported to have beneficial effects in various chronic neurological conditions via upregulation of its transcriptional co-activator PGC-1α and followed by regulation of multiple molecular events. Although several factors contribute to the progression of neurodegeneration, the dysfunction of PGC-1α expression is primarily interlinked with the pathogenesis of major neurodegenerative diseases. This review gives an insight that ligand-dependent activation of PPAR-γ by glitazones could initiate the structural conformational changes of the secondary proteins, thus recruiting the PGC-1α to form a stable regulatory complex that hampers the various molecular pathways contributing to neurodegeneration. The promising outcomes of the preliminary in silico studies included in this review support that PPAR-γ dependent activation of central PGC-1α signaling by novel glitazones is an encouraging strategy to enhance the oxy-radicals detoxifying system, antiinflammatory responses, and mitochondrial biogenesis required for neuroprotection in various neurodegenerative conditions.

Conditional Deletion of PGC-1α Results in Energetic and Functional Defects in NK Cells.

SummaryDuring an immune response, natural killer (NK) cells activate specific metabolic pathways to meet the increased energetic and biosynthetic demands associated with effector functions. Here, we found in vivo activation of NK cells during Listeria monocytogenes infection-augmented transcription of genes encoding mitochondria-associated proteins in a manner dependent on the transcriptional coactivator PGC-1α. Using an Ncr1Cre-based conditional knockout mouse, we found that PGC-1α was crucial for optimal NK cell effector functions and bioenergetics, as the deletion of PGC-1α was associated with decreased cytotoxic potential and cytokine production along with altered ADP/ATP ratios. Lack of PGC-1α also significantly impaired the ability of NK cells to control B16F10 tumor growth in vivo, and subsequent gene expression analysis showed that PGC-1α mediates transcription required to maintain mitochondrial activity within the tumor microenvironment. Together, these data suggest that PGC-1α-dependent transcription of specific target genes is required for optimal NK cell function during the response to infection or tumor growth.

Role of zinc transporter ZIP12 in susceptibility-weighted brain magnetic resonance imaging (MRI) phenotypes and mitochondrial function.

Brain zinc dysregulation is linked to many neurological disorders. However, the mechanisms regulating brain zinc homeostasis are poorly understood. We performed secondary analyses of brain MRI GWAS and exome sequencing data from adults in the UK Biobank. Coding ZIP12 polymorphisms in zinc transporter ZIP12 (SLC39A12) were associated with altered brain susceptibility weighted MRI (swMRI).Conditional and joint association analyses revealed independent GWAS signals in linkage disequilibrium with 2 missense ZIP12 polymorphisms, rs10764176 andrs72778328, with reduced zinc transport activity.ZIP12 rare coding variants predicted to be deleterious were associated with similar impacts on brain swMRI. In Neuro-2a cells, ZIP12 deficiency by short hairpin RNA (shRNA) depletion or CRISPR/Cas9 genome editing resulted in impaired mitochondrial function, increased superoxide presence, and detectable protein carbonylation.Inhibition of Complexes I and IV of the electron transport chain reduced neurite outgrowth in ZIP12 deficient cells.Transcriptional coactivator PGC-1α, mitochondrial superoxide dismutase (SOD2), and chemical antioxidants α-tocopherol, MitoTEMPO, and MitoQ restored neurite extension impaired by ZIP12 deficiency. Mutant forms of α-synuclein and tau linked to familial Parkinson's disease and frontotemporal dementia, respectively, reduced neurite outgrowth in cells deficient in ZIP12.Zinc and ZIP12 may confer resilience against neurological diseases or premature aging of the brain.

GATA3 induces the upregulation of UCP-1 by directly binding to PGC-1α during adipose tissue browning

ObjectiveObesity is recognized as the cause of multiple metabolic diseases and is rapidly increasing worldwide. As obesity is due to an imbalance in energy homeostasis, the promotion of energy consumption through browning of white adipose tissue (WAT) has emerged as a promising therapeutic strategy to counter the obesity epidemic. However, the molecular mechanisms of the browning process are not well understood. In this study, we investigated the effects of the GATA family of transcription factors on the browning process. MethodsWe used qPCR to analyze the expression of GATA family members during WAT browning. In order to investigate the function of GATA3 in the browning process, we used the lentivirus system for the ectopic expression and knockdown of GATA3. Western blot and real-time qPCR analyses revealed the regulation of thermogenic genes upon ectopic expression and knockdown of GATA3. Luciferase reporter assays, co-immunoprecipitation, and chromatin immunoprecipitation were performed to demonstrate that GATA3 interacts with proliferator-activated receptor-γ co-activator-1α (PGC-1α) to regulate the promoter activity of uncoupling protein-1 (UCP-1). Enhanced energy expenditure by GATA3 was confirmed using oxygen consumption assays, and the mitochondrial content was assessed using MitoTracker. Furthermore, we examined the in vivo effects of lentiviral GATA3 overexpression and knockdown in inguinal adipose tissue of mice. ResultsGata3 expression levels were significantly elevated in the inguinal adipose tissue of mice exposed to cold conditions. Ectopic expression of GATA3 enhanced the expression of UCP-1 and thermogenic genes upon treatment with norepinephrine whereas GATA3 knockdown had the opposite effect. Luciferase reporter assays using the UCP-1 promoter region showed that UCP-1 expression was increased in a dose-dependent manner by GATA3 regardless of norepinephrine treatment. GATA3 was found to directly bind to the promoter region of UCP-1. Furthermore, our results indicated that GATA3 interacts with the transcriptional coactivator PGC-1α to increase the expression of UCP-1. Taken together, we demonstrate that GATA3 has an important role in enhancing energy expenditure by increasing the expression of thermogenic genes both in vitro and in vivo. ConclusionGATA3 may represent a promising target for the prevention and treatment of obesity by regulating thermogenic capacity.

Colchicine treatment impairs skeletal muscle mitochondrial function and insulin sensitivity in an age-specific manner.

The aim of the study was to investigate the impact of autophagy inhibition on skeletal muscle mitochondrial function and glucose homeostasis in young and aged mice. The transcriptional co-activator PGC-1α regulates muscle oxidative phenotype which has been shown to be linked with basal autophagic capacity. Therefore, young and aged inducible muscle-specific PGC-1α knockout (iMKO) mice and littermate lox/lox controls were used in three separate experiments performed after either saline or colchicine injections on two consecutive days: (1) Euthanization in the basal state obtaining skeletal muscle for mitochondrial respirometry, (2) whole body glucose tolerance test, and (3) in vivo insulin-stimulated 2-deoxyglucose (2-DG) uptake into skeletal muscle. Muscle PGC-1α was not required for maintaining basal autophagy flux, regardless of age. Colchicine-induced inhibition of autophagy was associated with impairments of skeletal muscle mitochondrial function, including reduced ADP sensitivity and altered mitochondrial redox balance in both young and aged mice. Colchicine treatment reduced the glucose tolerance in aged, but not young mice, and similarly in iMKO and lox/lox mice. Colchicine reduced insulin-stimulated 2-DG uptake in soleus muscle in aged mice, independently of PGC-1α, and without affecting insulin-regulated phosphorylation of proximal or distal mediators of insulin signaling. In conclusion, the results indicate that autophagy regulates the mitochondrial ADP sensitivity and redox balance as well as whole body glucose tolerance and skeletal muscle insulin sensitivity in aged mice, with no additional effects of inducible PGC-1α deletion.

Targeting Mitochondrial Network Architecture in Down Syndrome and Aging.

Mitochondria are organelles that mainly control energy conversion in the cell. In addition, they also participate in many relevant activities, such as the regulation of apoptosis and calcium levels, and other metabolic tasks, all closely linked to cell viability. Functionality of mitochondria appears to depend upon their network architecture that may dynamically pass from an interconnected structure with long tubular units, to a fragmented one with short separate fragments. A decline in mitochondrial quality, which presents itself as an altered structural organization and a function of mitochondria, has been observed in Down syndrome (DS), as well as in aging and in age-related pathologies. This review provides a basic overview of mitochondrial dynamics, from fission/fusion mechanisms to mitochondrial homeostasis. Molecular mechanisms determining the disruption of the mitochondrial phenotype in DS and aging are discussed. The impaired activity of the transcriptional co-activator PGC-1α/PPARGC1A and the hyperactivation of the mammalian target of rapamycin (mTOR) kinase are emerging as molecular underlying causes of these mitochondrial alterations. It is, therefore, likely that either stimulating the PGC-1α activity or inhibiting mTOR signaling could reverse mitochondrial dysfunction. Evidence is summarized suggesting that drugs targeting either these pathways or other factors affecting the mitochondrial network may represent therapeutic approaches to improve and/or prevent the effects of altered mitochondrial function. Overall, from all these studies it emerges that the implementation of such strategies may exert protective effects in DS and age-related diseases.