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1.  PGC-1 coactivators in β-cells regulate lipid metabolism and are essential for insulin secretion coupled to fatty acids 
Molecular Metabolism  2015;4(11):811-822.
Objectives
Peroxisome proliferator-activated receptor γ coactivator 1 (PPARGCA1, PGC-1) transcriptional coactivators control gene programs important for nutrient metabolism. Islets of type 2 diabetic subjects have reduced PGC-1α expression and this is associated with decreased insulin secretion, yet little is known about why this occurs or what role it plays in the development of diabetes. Our goal was to delineate the role and importance of PGC-1 proteins to β-cell function and energy homeostasis.
Methods
We investigated how nutrient signals regulate coactivator expression in islets and the metabolic consequences of reduced PGC-1α and PGC-1β in primary and cultured β-cells. Mice with inducible β-cell specific double knockout of Pgc-1α/Pgc-1β (βPgc-1 KO) were created to determine the physiological impact of reduced Pgc1 expression on glucose homeostasis.
Results
Pgc-1α and Pgc-1β expression was increased in primary mouse and human islets by acute glucose and palmitate exposure. Surprisingly, PGC-1 proteins were dispensable for the maintenance of mitochondrial mass, gene expression, and oxygen consumption in response to glucose in adult β-cells. However, islets and mice with an inducible, β-cell-specific PGC-1 knockout had decreased insulin secretion due in large part to loss of the potentiating effect of fatty acids. Consistent with an essential role for PGC-1 in lipid metabolism, β-cells with reduced PGC-1s accumulated acyl-glycerols and PGC-1s controlled expression of key enzymes in lipolysis and the glycerolipid/free fatty acid cycle.
Conclusions
These data highlight the importance of PGC-1s in coupling β-cell lipid metabolism to promote efficient insulin secretion.
Graphical abstract
Highlights
•Loss of Pgc-1s in adult β-cells decreases insulin secretion in response to glucose/palmitate.•Pgc-1α/β is not required to maintain basal mitochondrial mass or oxidative capacity in mature β-cells.•Pgc-1α/β regulates expression of the lipolytic enzymes HSL and ATGL in β-cells.•Reduced β-cell Pgc-1 causes accumulation of intracellular acyl-glycerols and cholesterol esters.
doi:10.1016/j.molmet.2015.08.001
PMCID: PMC4632114  PMID: 26629405
Beta cell; PGC-1; Insulin secretion; Lipid metabolism; Mitochondria; Lipolysis
2.  PGC-1α Deficiency Causes Multi-System Energy Metabolic Derangements: Muscle Dysfunction, Abnormal Weight Control and Hepatic Steatosis 
PLoS Biology  2005;3(4):e101.
The gene encoding the transcriptional coactivator peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) was targeted in mice. PGC-1α null (PGC-1α−/−) mice were viable. However, extensive phenotyping revealed multi-system abnormalities indicative of an abnormal energy metabolic phenotype. The postnatal growth of heart and slow-twitch skeletal muscle, organs with high mitochondrial energy demands, is blunted in PGC-1α−/− mice. With age, the PGC-1α−/− mice develop abnormally increased body fat, a phenotype that is more severe in females. Mitochondrial number and respiratory capacity is diminished in slow-twitch skeletal muscle of PGC-1α−/− mice, leading to reduced muscle performance and exercise capacity. PGC-1α−/− mice exhibit a modest diminution in cardiac function related largely to abnormal control of heart rate. The PGC-1α−/− mice were unable to maintain core body temperature following exposure to cold, consistent with an altered thermogenic response. Following short-term starvation, PGC-1α−/− mice develop hepatic steatosis due to a combination of reduced mitochondrial respiratory capacity and an increased expression of lipogenic genes. Surprisingly, PGC-1α−/− mice were less susceptible to diet-induced insulin resistance than wild-type controls. Lastly, vacuolar lesions were detected in the central nervous system of PGC-1α−/− mice. These results demonstrate that PGC-1α is necessary for appropriate adaptation to the metabolic and physiologic stressors of postnatal life.
Eliminating the activity of the gene PGC-1 α in mice reveals its role in post-natal metabolism and provides a link to obesity and some intriguing differences with another report of this knockout
doi:10.1371/journal.pbio.0030101
PMCID: PMC1064854  PMID: 15760270
3.  PGC1α promotes tumor growth by inducing gene expression programs supporting lipogenesis 
Cancer Research  2011;71(21):6888-6898.
Despite the role of aerobic glycolysis in cancer, recent studies highlight the importance of the mitochondria and biosynthetic pathways as well. PPARγ coactivator 1α (PGC1α) is a key transcriptional regulator of several metabolic pathways including oxidative metabolism and lipogenesis. Initial studies suggested that PGC1α expression is reduced in tumors compared to adjacent normal tissue. Paradoxically, other studies show that PGC1α is associated with cancer cell proliferation. Therefore the role of PGC1α in cancer and especially carcinogenesis is unclear. Using Pgc1α-/- and Pgc1α+/+ mice we show that loss of PGC1α protects mice from azoxymethane induced colon carcinogenesis. Similarly, diethylnitrosamine induced liver carcinogenesis is reduced in Pgc1α-/- mice compared to Pgc1α+/+ mice. Xenograft studies using gain and loss of PGC1α expression demonstrated that PGC1α also promotes tumor growth. Interestingly, while PGC1α induced oxidative phosphorylation and TCA cycle gene expression, we also observed an increase in the expression of two genes required for de novo fatty acid synthesis, ACC and FASN. In addition, SLC25A1 and ACLY, which are required for the conversion of glucose in to acetyl CoA for fatty acid synthesis, were also increased by PGC1α, thus linking the oxidative and lipogenic functions of PGC1α. Indeed, using 13C stable isotope tracer analysis we show that PGC1α increased de novo lipogenesis. Importantly, inhibition of fatty acid synthesis blunted these progrowth effects of PGC1α. In conclusion, these studies show for the first time that loss of PGC1α protects against carcinogenesis and that PGC1α coordinately regulates mitochondrial and fatty acid metabolism to promote tumor growth.
doi:10.1158/0008-5472.CAN-11-1011
PMCID: PMC3282487  PMID: 21914785
Cancer metabolism; Warburg Effect; oxidative metabolism; lipogenesis; transcriptional regulation
4.  Sirtuin 3, a New Target of PGC-1α, Plays an Important Role in the Suppression of ROS and Mitochondrial Biogenesis 
PLoS ONE  2010;5(7):e11707.
Background
Sirtuin 3 (SIRT3) is one of the seven mammalian sirtuins, which are homologs of the yeast Sir2 gene. SIRT3 is the only sirtuin with a reported association with the human life span. Peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) plays important roles in adaptive thermogenesis, gluconeogenesis, mitochondrial biogenesis and respiration. PGC-1α induces several key reactive oxygen species (ROS)-detoxifying enzymes, but the molecular mechanism underlying this is not well understood.
Results
Here we show that PGC-1α strongly stimulated mouse Sirt3 gene expression in muscle cells and hepatocytes. Knockdown of PGC-1α led to decreased Sirt3 gene expression. PGC-1α activated the mouse SIRT3 promoter, which was mediated by an estrogen-related receptor (ERR) binding element (ERRE) (−407/−399) mapped to the promoter region. Chromatin immunoprecipitation and electrophoretic mobility shift assays confirmed that ERRα bound to the identified ERRE and PGC-1α co-localized with ERRα in the mSirt3 promoter. Knockdown of ERRα reduced the induction of Sirt3 by PGC-1α in C2C12 myotubes. Furthermore, Sirt3 was essential for PGC-1α-dependent induction of ROS-detoxifying enzymes and several components of the respiratory chain, including glutathione peroxidase-1, superoxide dismutase 2, ATP synthase 5c, and cytochrome c. Overexpression of SIRT3 or PGC-1α in C2C12 myotubes decreased basal ROS level. In contrast, knockdown of mSIRT3 increased basal ROS level and blocked the inhibitory effect of PGC-1α on cellular ROS production. Finally, SIRT3 stimulated mitochondrial biogenesis, and SIRT3 knockdown decreased the stimulatory effect of PGC-1α on mitochondrial biogenesis in C2C12 myotubes.
Conclusion
Our results indicate that Sirt3 functions as a downstream target gene of PGC-1α and mediates the PGC-1α effects on cellular ROS production and mitochondrial biogenesis. Thus, SIRT3 integrates cellular energy metabolism and ROS generation. The elucidation of the molecular mechanisms of SIRT3 regulation and its physiological functions may provide a novel target for treating ROS-related disease.
doi:10.1371/journal.pone.0011707
PMCID: PMC2908542  PMID: 20661474
5.  PGC-1 Coactivator Activity Is Required for Murine Erythropoiesis 
Molecular and Cellular Biology  2014;34(11):1956-1965.
Peroxisome proliferator-activated receptor gamma (PPARγ) coactivator 1α (PGC-1α) and PGC-1β have been shown to be intimately involved in the transcriptional regulation of cellular energy metabolism as well as other biological processes, but both coactivator proteins are expressed in many other tissues and organs in which their function is, in essence, unexplored. Here, we found that both PGC-1 proteins are abundantly expressed in maturing erythroid cells. PGC-1α and PGC-1β compound null mutant (Pgc-1c) animals express less β-like globin mRNAs throughout development; consequently, neonatal Pgc-1c mice exhibit growth retardation and profound anemia. Flow cytometry shows that the number of mature erythrocytes is markedly reduced in neonatal Pgc-1c pups, indicating that erythropoiesis is severely compromised. Furthermore, hematoxylin and eosin staining revealed necrotic cell death and cell loss in Pgc-1c livers and spleen. Chromatin immunoprecipitation studies revealed that both PGC-1α and -1β, as well as two nuclear receptors, TR2 and TR4, coordinately bind to the various globin gene promoters. In addition, PGC-1α and -1β can interact with TR4 to potentiate transcriptional activation. These data provide new insights into our understanding of globin gene regulation and raise the interesting possibility that the PGC-1 coactivators can interact with TR4 to elicit differential stage-specific effects on globin gene transcription.
doi:10.1128/MCB.00247-14
PMCID: PMC4019057  PMID: 24662048
6.  Endoplasmic Reticulum Stress Links Hepatitis C Virus RNA Replication to Wild-Type PGC-1α/Liver-Specific PGC-1α Upregulation 
Journal of Virology  2014;88(15):8361-8374.
ABSTRACT
Hepatitis C virus (HCV) causes not only severe liver problems but also extrahepatic manifestations, such as insulin resistance (IR). Wild-type peroxisome proliferator-activated receptor gamma coactivator 1 alpha (WT-PGC-1α) is essential in hepatic gluconeogenesis and has recently been demonstrated to link HCV infection to hepatic insulin resistance (IR). A recent study has characterized a novel human liver-specific PGC-1α (L-PGC-1α) transcript, which is proposed to reflect human adaption to more complex pathways. However, the effect of HCV infection on L-PGC-1α expression and the mechanism by which HCV modulates WT-PGC-1α/L-PGC-1α remain unclear. In this study, we showed that HCV infection upregulated both WT-PGC-1α and L-PGC-1α, which further promoted HCV production. The upregulation of both PGC-1α isoforms depended on HCV RNA replication. By using promoter-luciferase reporters, kinase inhibitors, and dominant negative mutants, we further observed that the HCV-induced upregulation of WT-PGC-1α was mediated by the phosphorylation of cyclic AMP (cAMP)-responsive element-binding protein (CREB), whereas that of L-PGC-1α was mediated by CREB phosphorylation and forkhead box O1 dephosphorylation. Moreover, HCV infection induced endoplasmic reticulum (ER) stress, and pharmacological induction of ER stress upregulated WT-PGC-1α/L-PGC-1α and phosphorylated CREB. In contrast, pharmacological inhibition of HCV-induced ER stress impaired WT-PGC-1α/L-PGC-1α upregulation along with decreased phosphorylated CREB. The correlation of hepatic mPGC-1α with ER stress was further confirmed in mice. Overall, HCV infection upregulates both WT-PGC-1α and L-PGC-1α through an ER stress-mediated, phosphorylated CREB-dependent pathway, and both PGC-1α isoforms promote HCV production in turn.
IMPORTANCE HCV causes not only severe liver problems but also extrahepatic manifestations, such as insulin resistance (IR). As a key regulator in energy metabolism, wild-type PGC-1α (WT-PGC-1α), has recently been demonstrated to link HCV infection to hepatic IR. A recent study has characterized a novel human liver-specific PGC-1α (L-PGC-1α), which reflects human adaption to more complex pathways. However, the effect of HCV infection on L-PGC-1α expression and the mechanism by which HCV regulates WT-PGC-1α/L-PGC-1α remain unclear. In this study, we showed that HCV infection upregulated both WT-PGC-1α and L-PGC-1α, which further promoted HCV production. WT-PGC-1α upregulation was mediated by CREB phosphorylation, whereas L-PGC-1α upregulation was mediated by CREB phosphorylation and FoxO1 dephosphorylation. HCV-induced ER stress mediated WT-PGC-1α/L-PGC-1α upregulation and CREB phosphorylation. Overall, this study provides new insights into the mechanism by which HCV upregulates WT-PGC-1α/L-PGC-1α and highlights the novel intervention of HCV-ER stress-PGC-1α signaling for HCV therapy and HCV-induced IR therapy.
doi:10.1128/JVI.01202-14
PMCID: PMC4135942  PMID: 24829353
7.  Metabolomic Analysis of the Skeletal Muscle of Mice Overexpressing PGC-1α 
PLoS ONE  2015;10(6):e0129084.
Peroxisome proliferator-activated receptor (PPAR) γ coactivator 1α (PGC-1α) is a coactivator of various nuclear receptors and other transcription factors whose expression increases in the skeletal muscle during exercise. We have previously made transgenic mice overexpressing PGC-1α in the skeletal muscle (PGC-1α-Tg mice). PGC-1α upregulates the expression of genes associated with red fibers, mitochondrial function, fatty acid oxidation, and branched chain amino acid (BCAA) degradation. However, global analyses of the actual metabolic products have not been investigated. In this study, we conducted metabolomic analysis of the skeletal muscle in PGC-1α-Tg mice by capillary electrophoresis with electrospray ionization time-of-flight mass spectrometry. Principal component analysis and hierarchical cluster analysis showed clearly distinguishable changes in the metabolites between PGC-1α-Tg and wild-type control mice. Changes were observed in metabolite levels of various metabolic pathways such as the TCA cycle, pentose phosphate pathway, nucleotide synthesis, purine nucleotide cycle, and amino acid metabolism, including BCAA and β-alanine. Namely, metabolic products of the TCA cycle increased in PGC-1α-Tg mice, with increased levels of citrate (2.3-fold), succinate (2.2-fold), fumarate (2.8-fold), and malate (2.3-fold) observed. Metabolic products associated with the pentose phosphate pathway and nucleotide biosynthesis also increased in PGC-1α-Tg mice. Meanwhile, BCAA levels decreased (Val, 0.7-fold; Leu, 0.8-fold; and Ile, 0.7-fold), and Glu (3.1-fold) and Asp (2.2-fold) levels increased. Levels of β-alanine and related metabolites were markedly decreased in PGC-1α-Tg mice. Coordinated regulation of the TCA cycle and amino acid metabolism, including BCAA, suggests that PGC-1α plays important roles in energy metabolism. Moreover, our metabolomics data showing the activation of the purine nucleotide pathway, malate–aspartate shuttle, as well as creatine metabolism, which are known to be active during exercise, further suggests that PGC-1α regulates metabolism in exercise. Thus, we demonstrated the roles of PGC-1α in the skeletal muscle at the metabolite level.
doi:10.1371/journal.pone.0129084
PMCID: PMC4482640  PMID: 26114427
8.  Post-natal induction of PGC-1α protects against severe muscle dystrophy independently of utrophin 
Skeletal Muscle  2014;4:2.
Background
Duchenne muscle dystrophy (DMD) afflicts 1 million boys in the US and has few effective treatments. Constitutive transgenic expression of the transcriptional coactivator peroxisome proliferator-activated receptor gamma coactivator (PGC)-1α improves skeletal muscle function in the murine “mdx” model of DMD, but how this occurs, or whether it can occur post-natally, is not known. The leading mechanistic hypotheses for the benefits conferred by PGC-1α include the induction of utrophin, a dystrophin homolog, and/or induction and stabilization of the neuromuscular junction.
Methods
The effects of transgenic overexpression of PGC-1β, a homolog of PGC-1α in mdx mice was examined using different assays of skeletal muscle structure and function. To formally test the hypothesis that PGC-1α confers benefit in mdx mice by induction of utrophin and stabilization of neuromuscular junction, PGC-1α transgenic animals were crossed with the dystrophin utrophin double knock out (mdx/utrn-/-) mice, a more severe dystrophic model. Finally, we also examined the effect of post-natal induction of skeletal muscle-specific PGC-1α overexpression on muscle structure and function in mdx mice.
Results
We show here that PGC-1β does not induce utrophin or other neuromuscular genes when transgenically expressed in mouse skeletal muscle. Surprisingly, however, PGC-1β transgenesis protects as efficaciously as PGC-1α against muscle degeneration in dystrophin-deficient (mdx) mice, suggesting that alternate mechanisms of protection exist. When PGC-1α is overexpressed in mdx/utrn-/- mice, we find that PGC-1α dramatically ameliorates muscle damage even in the absence of utrophin. Finally, we also used inducible skeletal muscle-specific PGC-1α overexpression to show that PGC-1α can protect against dystrophy even if activated post-natally, a more plausible therapeutic option.
Conclusions
These data demonstrate that PGC-1α can improve muscle dystrophy post-natally, highlighting its therapeutic potential. The data also show that PGC-1α is equally protective in the more severely affected mdx/utrn-/- mice, which more closely recapitulates the aggressive progression of muscle damage seen in DMD patients. The data also identify PGC-1β as a novel potential target, equally efficacious in protecting against muscle dystrophy. Finally, the data also show that PGC-1α and PGC-1β protect against dystrophy independently of utrophin or of induction of the neuromuscular junction, indicating the existence of other mechanisms.
doi:10.1186/2044-5040-4-2
PMCID: PMC3914847  PMID: 24447845
PGC-1α; PGC-1β; mdx; Duchenne Muscle Dystrophy; Utrophin; Neuromuscular junction
9.  Ablation of PGC-1β Results in Defective Mitochondrial Activity, Thermogenesis, Hepatic Function, and Cardiac Performance 
PLoS Biology  2006;4(11):e369.
The transcriptional coactivator peroxisome proliferator-activated receptor-gamma coactivator-1β (PGC-1β) has been implicated in important metabolic processes. A mouse lacking PGC-1β (PGC1βKO) was generated and phenotyped using physiological, molecular, and bioinformatic approaches. PGC1βKO mice are generally viable and metabolically healthy. Using systems biology, we identified a general defect in the expression of genes involved in mitochondrial function and, specifically, the electron transport chain. This defect correlated with reduced mitochondrial volume fraction in soleus muscle and heart, but not brown adipose tissue (BAT). Under ambient temperature conditions, PGC-1β ablation was partially compensated by up-regulation of PGC-1α in BAT and white adipose tissue (WAT) that lead to increased thermogenesis, reduced body weight, and reduced fat mass. Despite their decreased fat mass, PGC1βKO mice had hypertrophic adipocytes in WAT. The thermogenic role of PGC-1β was identified in thermoneutral and cold-adapted conditions by inadequate responses to norepinephrine injection. Furthermore, PGC1βKO hearts showed a blunted chronotropic response to dobutamine stimulation, and isolated soleus muscle fibres from PGC1βKO mice have impaired mitochondrial function. Lack of PGC-1β also impaired hepatic lipid metabolism in response to acute high fat dietary loads, resulting in hepatic steatosis and reduced lipoprotein-associated triglyceride and cholesterol content. Altogether, our data suggest that PGC-1β plays a general role in controlling basal mitochondrial function and also participates in tissue-specific adaptive responses during metabolic stress.
The authors conduct an in-depth analysis of a PGC-1β knockout mouse; these animals posses specific defects in basal mitochondrial function and adaptation to metabolic stress.
doi:10.1371/journal.pbio.0040369
PMCID: PMC1634886  PMID: 17090215
10.  The transcriptional coregulator PGC-1β controls mitochondrial function and anti-oxidant defence in skeletal muscles 
Nature Communications  2015;6:10210.
The transcriptional coregulators PGC-1α and PGC-1β modulate the expression of numerous partially overlapping genes involved in mitochondrial biogenesis and energetic metabolism. The physiological role of PGC-1β is poorly understood in skeletal muscle, a tissue of high mitochondrial content to produce ATP levels required for sustained contractions. Here we determine the physiological role of PGC-1β in skeletal muscle using mice, in which PGC-1β is selectively ablated in skeletal myofibres at adulthood (PGC-1β(i)skm−/− mice). We show that myofibre myosin heavy chain composition and mitochondrial number, muscle strength and glucose homeostasis are unaffected in PGC-1β(i)skm−/− mice. However, decreased expression of genes controlling mitochondrial protein import, translational machinery and energy metabolism in PGC-1β(i)skm−/− muscles leads to mitochondrial structural and functional abnormalities, impaired muscle oxidative capacity and reduced exercise performance. Moreover, enhanced free-radical leak and reduced expression of the mitochondrial anti-oxidant enzyme Sod2 increase muscle oxidative stress. PGC-1β is therefore instrumental for skeletal muscles to cope with high energetic demands.
PGC-1 family transcription factors are important regulators of cellular energy metabolism. Here the authors use tissue-specific, inducible PGC-1β KO mice to show that PGC-1 family members are not functionally redundant and that PGC-1β is required to maintain mitochondrial function in skeletal muscle.
doi:10.1038/ncomms10210
PMCID: PMC4703903  PMID: 26674215
11.  Parvalbumin Deficiency and GABAergic Dysfunction in Mice Lacking PGC-1α 
The transcriptional coactivator peroxisome proliferator activated receptor γ coactivator 1α (PGC-1α) is a master regulator of metabolism in peripheral tissues, and it has been proposed that PGC-1α plays a similar role in the brain. Recent evidence suggests that PGC-1α is concentrated in GABAergic interneurons, so we investigated whether male and female PGC-1α −/− mice exhibit abnormalities in interneuron gene expression and/or function. We found a striking reduction in the expression of the Ca2+ binding protein parvalbumin (PV), but not other GABAergic markers, throughout the cerebrum in PGC-1α +/− and −/− mice. Furthermore, PGC-1α overexpression in cell culture was sufficient to robustly induce PV expression. Consistent with a reduction in PV rather than a loss of PV-expressing interneurons, spontaneous synaptic inhibition was not altered in PGC-1α −/− mice. However, evoked synaptic responses displayed less paired pulse depression and dramatic facilitation in response to repetitive stimulation at the gamma frequency. PV transcript expression was also significantly reduced in retina and heart of PGC-1α −/− animals, suggesting that PGC-1α is required for proper expression of PV in multiple tissues. Together these findings indicate that PGC-1α is a novel regulator of interneuron gene expression and function and a potential therapeutic target for neurological disorders associated with PGC-1α dysregulation.
doi:10.1523/JNEUROSCI.0698-10.2010
PMCID: PMC2888101  PMID: 20505089
interneuron; early postnatal development; calcium; γ-aminobutyric acid; PPARGC1A
12.  Peroxisome proliferator–activated receptor γ coactivator-1 promotes cardiac mitochondrial biogenesis 
Journal of Clinical Investigation  2000;106(7):847-856.
Cardiac mitochondrial function is altered in a variety of inherited and acquired cardiovascular diseases. Recent studies have identified the transcriptional coactivator peroxisome proliferator–activated receptor γ coactivator-1 (PGC-1) as a regulator of mitochondrial function in tissues specialized for thermogenesis, such as brown adipose. We sought to determine whether PGC-1 controlled mitochondrial biogenesis and energy-producing capacity in the heart, a tissue specialized for high-capacity ATP production. We found that PGC-1 gene expression is induced in the mouse heart after birth and in response to short-term fasting, conditions known to increase cardiac mitochondrial energy production. Forced expression of PGC-1 in cardiac myocytes in culture induced the expression of nuclear and mitochondrial genes involved in multiple mitochondrial energy-transduction/energy-production pathways, increased cellular mitochondrial number, and stimulated coupled respiration. Cardiac-specific overexpression of PGC-1 in transgenic mice resulted in uncontrolled mitochondrial proliferation in cardiac myocytes leading to loss of sarcomeric structure and a dilated cardiomyopathy. These results identify PGC-1 as a critical regulatory molecule in the control of cardiac mitochondrial number and function in response to energy demands.
PMCID: PMC517815  PMID: 11018072
13.  PGC−1α Promoter Methylation in Parkinson’s Disease 
PLoS ONE  2015;10(8):e0134087.
The etiopathogenesis of sporadic Parkinson’s disease (PD) remains elusive although mitochondrial dysfunction has long been implicated. Recent evidence revealed reduced expression of peroxisome proliferator-activated receptor gamma coactivator−1 α (PGC−1α) and downstream regulated nuclear encoded respiratory complex genes in affected brain tissue from PD patients. We sought to determine whether epigenetic modification of the PGC−1α gene could account for diminished expression. In substantia nigra from PD patients but not control subjects, we show significant promoter-proximal non-canonical cytosine methylation of the PGC−1α gene but not an adjacent gene. As neuroinflammation is a prominent feature of PD and a mediator of epigenetic change, we evaluated whether the pro-inflammatory fatty acid, palmitate, would stimulate PGC−1α promoter methylation in different cell types from the CNS. Indeed, in mouse primary cortical neurons, microglia and astrocytes, palmitate causes PGC−1α gene promoter non-canonical cytosine methylation, reduced expression of the gene and reduced mitochondrial content. Moreover, intracerebroventricular (ICV) injection of palmitate to transgenic human α−synuclein mutant mice resulted in increased PGC−1α promoter methylation, decreased PGC−1α expression and reduced mitochondrial content in substantia nigra. Finally we provide evidence that dysregulation of ER stress and inflammatory signaling is associated with PGC−1α promoter methylation. Together, these data strengthen the connection between saturated fatty acids, neuroflammation, ER stress, epigenetic alteration and bioenergetic compromise in PD.
doi:10.1371/journal.pone.0134087
PMCID: PMC4552803  PMID: 26317511
14.  NT-PGC-1α Activation Attenuates High-Fat Diet–Induced Obesity by Enhancing Brown Fat Thermogenesis and Adipose Tissue Oxidative Metabolism 
Diabetes  2014;63(11):3615-3625.
The transcriptional coactivator peroxisome proliferator–activated receptor γ coactivator (PGC)-1α and its splice variant N terminal (NT)-PGC-1α regulate adaptive thermogenesis by transcriptional induction of thermogenic and mitochondrial genes involved in energy metabolism. We previously reported that full-length PGC-1α (FL-PGC-1α) is dispensable for cold-induced nonshivering thermogenesis in FL-PGC-1α−/− mice, since a slightly shorter but functionally equivalent form of NT-PGC-1α (NT-PGC-1α254) fully compensates for the loss of FL-PGC-1α in brown and white adipose tissue. In the current study, we challenged FL-PGC-1α−/− mice with a high-fat diet (HFD) to investigate the effects of diet-induced thermogenesis on HFD-induced obesity. Despite a large decrease in locomotor activity, FL-PGC-1α−/− mice exhibited the surprising ability to attenuate HFD-induced obesity. Reduced fat mass in FL-PGC-1α−/− mice was closely associated with an increase in body temperature, energy expenditure, and whole-body fatty acid oxidation (FAO). Mechanistically, FL-PGC-1α−/− brown adipose tissue had an increased capacity to oxidize fatty acids and dissipate energy as heat, in accordance with upregulation of thermogenic genes UCP1 and DIO2. Furthermore, augmented expression of FAO and lipolytic genes in FL-PGC-1α−/− white adipose tissue was highly correlated with decreased fat storage in adipose tissue. Collectively, our data highlight a protective effect of NT-PGC-1α on diet-induced obesity by enhancing diet-induced thermogenesis and FAO.
doi:10.2337/db13-1837
PMCID: PMC4207386  PMID: 24848065
15.  A Critical Function of Mad2l2 in Primordial Germ Cell Development of Mice 
PLoS Genetics  2013;9(8):e1003712.
The development of primordial germ cells (PGCs) involves several waves of epigenetic reprogramming. A major step is following specification and involves the transition from the stably suppressive histone modification H3K9me2 to the more flexible, still repressive H3K27me3, while PGCs are arrested in G2 phase of their cycle. The significance and underlying molecular mechanism of this transition were so far unknown. Here, we generated mutant mice for the Mad2l2 (Mad2B, Rev7) gene product, and found that they are infertile in both males and females. We demonstrated that Mad2l2 is essential for PGC, but not somatic development. PGCs were specified normally in Mad2l2−/− embryos, but became eliminated by apoptosis during the subsequent phase of epigenetic reprogramming. A majority of knockout PGCs failed to arrest in the G2 phase, and did not switch from a H3K9me2 to a H3K27me3 configuration. By the analysis of transfected fibroblasts we found that the interaction of Mad2l2 with the histone methyltransferases G9a and GLP lead to a downregulation of H3K9me2. The inhibitory binding of Mad2l2 to Cyclin dependent kinase 1 (Cdk1) could arrest the cell cycle in the G2 phase, and also allowed another histone methyltransferase, Ezh2, to upregulate H3K27me3. Together, these results demonstrate the potential of Mad2l2 in the regulation of both cell cycle and the epigenetic status. The function of Mad2l2 is essential in PGCs, and thus of high relevance for fertility.
Author Summary
Primordial germ cells (PGCs) are the origin of sperm and oocytes, and are responsible for transferring genetic information to the next generation faithfully. PGCs are first specified from pluripotent epiblast cells early in embryonic development. Second, they reprogram their epigenetic signature by changing histone modifications. This developmental event is specific to germ cells but not somatic cells. Although many players in the specification of PGCs are identified, only little is known about the genes essential for the regulation of the second phase. Here, we report that the Mad2l2 gene product plays an important role in the epigenetic reprogramming of PGCs. In wild type PGCs the cell cycle is arrested, and the methylation of histone 3 on residue K9 is replaced by methylation on K27. Our findings indicate that Mad2l2 is involved in this coordination of cell cycle and epigenetic reprogramming. The elucidation of this mechanism would help to identify the genetic basis of infertility.
doi:10.1371/journal.pgen.1003712
PMCID: PMC3757036  PMID: 24009519
16.  Transcriptional Control of Cardiac Fuel Metabolism and Mitochondrial Function 
As a persistent pump, the mammalian heart demands a high-capacity mitochondrial system. Significant progress has been made in delineating the gene regulatory networks that control mitochondrial biogenesis and function in striated muscle. The PPARγ coactivator-1 (PGC-1) coactivators serve as inducible boosters of downstream transcription factors that control the expression of genes involved in mitochondrial energy transduction, ATP synthesis, and biogenesis. PGC-1 gain-of-function and loss-of-function studies targeting two PGC-1 family members, PGC-1α and PGC-1β, have provided solid evidence that these factors are both necessary and sufficient for perinatal mitochondrial biogenesis and maintenance of high-capacity mitochondrial function in postnatal heart. In humans, during the development of heart failure owing to hypertension or obesity-related diabetes, the activity of the PGC-1 coactivators, and several downstream target transcription factors, is altered. Gene targeting studies in mice have demonstrated that loss of PGC-1α and PGC-1β in heart leads to heart failure. Interestingly, the pattern of dysregulation within the PGC-1 transcriptional regulatory circuit distinguishes the heart disease caused by hypertension from that caused by diabetes. This transcriptional regulatory cascade and downstream metabolic pathways should be considered as targets for novel etiology-specific therapeutics aimed at the early stages of heart failure.
doi:10.1101/sqb.2011.76.011965
PMCID: PMC3340448  PMID: 22096028
17.  ApoE−/− PGC-1α−/− Mice Display Reduced IL-18 Levels and Do Not Develop Enhanced Atherosclerosis 
PLoS ONE  2010;5(10):e13539.
Background
Atherosclerosis is a chronic inflammatory disease that evolves from the interaction of activated endothelial cells, macrophages, lymphocytes and modified lipoproteins (LDLs). In the last years many molecules with crucial metabolic functions have been shown to prevent important steps in the progression of atherogenesis, including peroxisome proliferator activated receptors (PPARs) and the class III histone deacetylase (HDAC) SIRT1. The PPARγ coactivator 1 alpha (Ppargc1a or PGC-1α) was identified as an important transcriptional cofactor of PPARγ and is activated by SIRT1. The aim of this study was to analyze total PGC-1α deficiency in an atherosclerotic mouse model.
Methodology/Principal Findings
To investigate if total PGC-1α deficiency affects atherosclerosis, we compared ApoE−/− PGC-1α−/− and ApoE−/− PGC-1α+/+ mice kept on a high cholesterol diet. Despite having more macrophages and a higher ICAM-1 expression in plaques, ApoE−/− PGC-1α−/− did not display more or larger atherosclerotic plaques than their ApoE−/− PGC-1α+/+ littermates. In line with the previously published phenotype of PGC-1α−/− mice, ApoE−/− PGC-1α−/− mice had marked reduced body, liver and epididymal white adipose tissue (WAT) weight. VLDL/LDL-cholesterol and triglyceride contents were also reduced. Aortic expression of PPARα and PPARγ, two crucial regulators for adipocyte differentitation and glucose and lipid metabolism, as well as the expression of some PPAR target genes was significantly reduced in ApoE−/− PGC-1α−/− mice. Importantly, the epididymal WAT and aortic expression of IL-18 and IL-18 plasma levels, a pro-atherosclerotic cytokine, was markedly reduced in ApoE−/− PGC-1α−/− mice.
Conclusions/Significance
ApoE−/− PGC-1α−/− mice, similar as PGC-1α−/− mice exhibit markedly reduced total body and visceral fat weight. Since inflammation of visceral fat is a crucial trigger of atherogenesis, decreased visceral fat in PGC-1α-deficient mice may explain why these mice do not develop enhanced atherosclerosis.
doi:10.1371/journal.pone.0013539
PMCID: PMC2962638  PMID: 21042583
18.  Dynamic Partnership between TFIIH, PGC-1α and SIRT1 Is Impaired in Trichothiodystrophy 
PLoS Genetics  2014;10(10):e1004732.
The expression of protein-coding genes requires the selective role of many transcription factors, whose coordinated actions remain poorly understood. To further grasp the molecular mechanisms that govern transcription, we focused our attention on the general transcription factor TFIIH, which gives rise, once mutated, to Trichothiodystrophy (TTD), a rare autosomal premature-ageing disease causing inter alia, metabolic dysfunctions. Since this syndrome could be connected to transcriptional defects, we investigated the ability of a TTD mouse model to cope with food deprivation, knowing that energy homeostasis during fasting involves an accurate regulation of the gluconeogenic genes in the liver. Abnormal amounts of gluconeogenic enzymes were thus observed in TTD hepatic parenchyma, which was related to the dysregulation of the corresponding genes. Strikingly, such gene expression defects resulted from the inability of PGC1-α to fulfill its role of coactivator. Indeed, extensive molecular analyses unveiled that wild-type TFIIH cooperated in an ATP-dependent manner with PGC1-α as well as with the deacetylase SIRT1, thereby contributing to the PGC1-α deacetylation by SIRT1. Such dynamic partnership was, however, impaired when TFIIH was mutated, having as a consequence the disruption of PGC1-α recruitment to the promoter of target genes. Therefore, besides a better understanding of the etiology of TFIIH-related disease, our results shed light on the synergistic relationship that exist between different types of transcription factors, which is necessary to properly regulate the expression of protein coding genes.
Author Summary
In eukaryotes, the expression of genes encoding proteins requires the action of hundreds of factors, together with the RNA polymerase II. While these factors are timely and selectively required for the expression of a given gene, little is known about their partnership upon gene expression. Our results reveal a cooperation between different types of transcription factors, namely the general transcription factor TFIIH, the cofactor PGC-1α and the deacetylase SIRT1. Such partnership is however impaired when TFIIH is mutated, as observed in Trichothiodystrophy patients that develop premature ageing. These results thus shed light on the coordinated action of factors during transcription and allow us to better understand molecular deficiencies observed in many human diseases.
doi:10.1371/journal.pgen.1004732
PMCID: PMC4207666  PMID: 25340339
19.  PGC1β Mediates PPARγ Activation of Osteoclastogenesis and Rosiglitazone-Induced Bone Loss 
Cell metabolism  2010;11(6):503-516.
SUMMARY
Long-term usage of rosiglitazone, a synthetic PPARγ agonist, increases fracture rates among diabetic patients. PPARγ suppresses osteoblastogenesis while activating osteoclastogenesis, suggesting that rosiglitazone decreases bone formation while sustaining or increasing bone resorption. Using mouse models with genetically altered PPARγ, PGC1β or ERRα, here we show that PGC1β is required for the resorption-enhancing effects of rosiglitazone. PPARγ activation indirectly induces PGC1β expression by down-regulating β-catenin and derepressing c-jun. PGC1β in turn functions as a PPARγ coactivator to stimulate osteoclast differentiation. Complementarily, PPARγ also induces ERRα expression, which coordinates with PGC1β to enhance mitochondrial biogenesis and osteoclast function. ERRα knockout mice exhibit osteoclast defects, revealing ERRα as an important regulator of osteoclastogenesis. Strikingly, PGC1β deletion in osteoclasts confers complete resistance to rosiglitazone-induced bone loss. These findings identify PGC1β as an essential mediator for the PPARγ stimulation of osteoclastogenesis by targeting both PPARγ itself and ERRα, thus activating two distinct transcriptional programs.
doi:10.1016/j.cmet.2010.04.015
PMCID: PMC3521515  PMID: 20519122
20.  PGC-1α regulates the cell cycle through ATP and ROS in CH1 cells* #  
Peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) is a transcriptional co-activator involved in mitochondrial biogenesis, respiratory capacity, and oxidative phosphorylation (OXPHOS). PGC-1α plays an important role in cellular metabolism and is associated with tumorigenesis, suggesting an involvement in cell cycle progression. However, the underlying mechanisms mediating its involvement in these processes remain unclear. To elucidate the signaling pathways involved in PGC-1α function, we established a cell line, CH1 PGC-1α, which stably overexpresses PGC-1α. Using this cell line, we found that over-expression of PGC-1α stimulated extra adenosine triphosphate (ATP) and reduced reactive oxygen species (ROS) production. These effects were accompanied by up-regulation of the cell cycle checkpoint regulators CyclinD1 and CyclinB1. We hypothesized that ATP and ROS function as cellular signals to regulate cyclins and control cell cycle progression. Indeed, we found that reduction of ATP levels down-regulated CyclinD1 but not CyclinB1, whereas elevation of ROS levels down-regulated CyclinB1 but not CyclinD1. Furthermore, both low ATP levels and elevated ROS levels inhibited cell growth, but PGC-1α was maintained at a constant level. Together, these results demonstrate that PGC-1α regulates cell cycle progression through modulation of CyclinD1 and CyclinB1 by ATP and ROS. These findings suggest that PGC-1α potentially coordinates energy metabolism together with the cell cycle.
doi:10.1631/jzus.B1500158
PMCID: PMC4757583  PMID: 26834014
Peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α); Mitochondria; Oxidative phosphorylation (OXPHOS); Cell cycle; CyclinD1; CyclinB1
21.  PGC-1α Provides a Transcriptional Framework for Synchronous Neurotransmitter Release from Parvalbumin-Positive Interneurons 
The Journal of Neuroscience  2014;34(43):14375-14387.
Accumulating evidence strongly implicates the transcriptional coactivator peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) in the pathophysiology of multiple neurological disorders, but the downstream gene targets of PGC-1α in the brain have remained enigmatic. Previous data demonstrate that PGC-1α is primarily concentrated in inhibitory neurons and that PGC-1α is required for the expression of the interneuron-specific Ca2+-binding protein parvalbumin (PV) throughout the cortex. To identify other possible transcriptional targets of PGC-1α in neural tissue, we conducted a microarray on neuroblastoma cells overexpressing PGC-1α, mined results for genes with physiological relevance to interneurons, and measured cortical gene and protein expression of these genes in mice with underexpression and overexpression of PGC-1α. We observed bidirectional regulation of novel PGC-1α-dependent transcripts spanning synaptic [synaptotagmin 2 (Syt2) and complexin 1 (Cplx1)], structural [neurofilament heavy chain (Nefh)], and metabolic [neutral cholesterol ester hydrolase 1 (Nceh1), adenylate kinase 1 (Ak1), inositol polyphosphate 5-phosphatase J (Inpp5j), ATP synthase mitochondrial F1 complex O subunit (Atp5o), phytanol-CoA-2hydroxylase (Phyh), and ATP synthase mitrochondrial F1 complex α subunit 1 (Atp5a1)] functions. The neuron-specific genes Syt2, Cplx1, and Nefh were developmentally upregulated in an expression pattern consistent with that of PGC-1α and were expressed in cortical interneurons. Conditional deletion of PGC-1α in PV-positive neurons significantly decreased cortical transcript expression of these genes, promoted asynchronous GABA release, and impaired long-term memory. Collectively, these data demonstrate that PGC-1α is required for normal PV-positive interneuron function and that loss of PGC-1α in this interneuron subpopulation could contribute to cortical dysfunction in disease states.
doi:10.1523/JNEUROSCI.1222-14.2014
PMCID: PMC4205559  PMID: 25339750
Barnes maze; cortical development; Huntington disease; ppargc1a; schizophrenia; strontium
22.  Deletion of the metabolic transcriptional coactivator PGC1β induces cardiac arrhythmia 
Cardiovascular Research  2011;92(1):29-38.
Aims
Peroxisome proliferator-activated receptor-γ coactivators PGC1α and PGC1β modulate mitochondrial biogenesis and energy homeostasis. The function of these transcriptional coactivators is impaired in obesity, insulin resistance, and type 2 diabetes. We searched for transcriptomic, lipidomic, and electrophysiological alterations in PGC1β−/− hearts potentially associated with increased arrhythmic risk in metabolic diseases.
Methods and results
Microarray analysis in mouse PGC1β−/− hearts confirmed down-regulation of genes related to oxidative phosphorylation and the electron transport chain and up-regulation of hypertrophy- and hypoxia-related genes. Lipidomic analysis showed increased levels of the pro-arrhythmic and pro-inflammatory lipid, lysophosphatidylcholine. PGC1β−/− mouse electrocardiograms showed irregular heartbeats and an increased incidence of polymorphic ventricular tachycardia following isoprenaline infusion. Langendorff-perfused PGC1β−/− hearts showed action potential alternans, early after-depolarizations, and ventricular tachycardia. PGC1β−/− ventricular myocytes showed oscillatory resting potentials, action potentials with early and delayed after-depolarizations, and burst firing during sustained current injection. They showed abnormal diastolic Ca2+ transients, whose amplitude and frequency were increased by isoprenaline, and Ca2+ currents with negatively shifted inactivation characteristics, with increased window currents despite unaltered levels of CACNA1C RNA transcripts. Inwardly and outward rectifying K+ currents were all increased. Quantitiative RT-PCR demonstrated increased SCN5A, KCNA5, RYR2, and Ca2+-calmodulin dependent protein kinase II expression.
Conclusion
PGC1β−/− hearts showed a lysophospholipid-induced cardiac lipotoxicity and impaired bioenergetics accompanied by an ion channel remodelling and altered Ca2+ homeostasis, converging to produce a ventricular arrhythmic phenotype particularly during adrenergic stress. This could contribute to the increased cardiac mortality associated with both metabolic and cardiac disease attributable to lysophospholipid accumulation.
doi:10.1093/cvr/cvr155
PMCID: PMC3172981  PMID: 21632884
Mitochondria; Cardiac arrhythmia; Peroxisome proliferator-activated receptor-γ coactivator 1β; Metabolic disease; Lysophosphatidylcholine
23.  Truncated Peroxisome Proliferator-Activated Receptor-γ Coactivator 1α Splice Variant Is Severely Altered in Huntington's Disease 
Neuro-Degenerative Diseases  2011;8(6):496-503.
Background
Reduced peroxisome proliferator-activated receptor-γ coactivator 1α (PGC1α) gene expression has been observed in striatal cell lines, transgenic mouse models of Huntington's disease (HD), and brain tissue from HD patients. As this protein is a key transcription regulator of the expression of many mitochondrial proteins, these observations strongly support the role of aberrant mitochondrial function in the pathogenesis of HD. The PGC1α protein undergoes posttranslational modifications that affect its transcriptional activity. The N-truncated splice variant of PGC1α (NT-PGC1α) is produced in tissues, but the role of truncated splice variants of PGC1α in HD and in the regulation of mitochondrial gene expression has not been elucidated.
Objective
To examine the expression and modulation of expression of NT-PGC1α levels in HD.
Methods and Results
We found that the NT-PGC1α protein, a splice variant of ∼38 kDa, but not full-length PGC1α is severely and consistently altered in human HD brain, human HD myoblasts, mouse HD models, and HD striatal cells. NT-PGC1α levels were significantly upregulated in HD cells and mouse brown fat by physiologically relevant stimuli that are known to upregulate PGC1α gene expression. This resulted in an increase in mitochondrial gene expression and cytochrome c content.
Conclusion
Our data suggest that NT-PGC1α is an important component of the PGC1α transcriptional network, which plays a significant role in the pathogenesis of HD.
Copyright © 2011 S. Karger AG, Basel
doi:10.1159/000327910
PMCID: PMC3186722  PMID: 21757867
Neurodegeneration; PGC1α; Mitochondrial gene expression; Alternative splicing; Huntington's disease; Striatal neurons
24.  Impaired PGC-1α function in muscle in Huntington's disease 
Human Molecular Genetics  2009;18(16):3048-3065.
We investigated the role of PPAR γ coactivator 1α (PGC-1α) in muscle dysfunction in Huntington's disease (HD). We observed reduced PGC-1α and target genes expression in muscle of HD transgenic mice. We produced chronic energy deprivation in HD mice by administering the catabolic stressor β-guanidinopropionic acid (GPA), a creatine analogue that reduces ATP levels, activates AMP-activated protein kinase (AMPK), which in turn activates PGC-1α. Treatment with GPA resulted in increased expression of AMPK, PGC-1α target genes, genes for oxidative phosphorylation, electron transport chain and mitochondrial biogenesis, increased oxidative muscle fibers, numbers of mitochondria and motor performance in wild-type, but not in HD mice. In muscle biopsies from HD patients, there was decreased PGC-1α, PGC-1β and oxidative fibers. Oxygen consumption, PGC-1α, NRF1 and response to GPA were significantly reduced in myoblasts from HD patients. Knockdown of mutant huntingtin resulted in increased PGC-1α expression in HD myoblast. Lastly, adenoviral-mediated delivery of PGC-1α resulted increased expression of PGC-1α and markers for oxidative muscle fibers and reversal of blunted response for GPA in HD mice. These findings show that impaired function of PGC-1α plays a critical role in muscle dysfunction in HD, and that treatment with agents to enhance PGC-1α function could exert therapeutic benefits. Furthermore, muscle may provide a readily accessible tissue in which to monitor therapeutic interventions.
doi:10.1093/hmg/ddp243
PMCID: PMC2733807  PMID: 19460884
25.  MICE LACKING THE TRANSCRIPTIONAL COACTIVATOR PGC-1α EXHIBIT ALTERATIONS IN INHIBITORY SYNAPTIC TRANSMISSION IN THE MOTOR CORTEX 
Neuroscience  2014;271:137-148.
Peroxisome proliferator activated receptor γ coactivator 1α (PGC-1α) is a transcriptional coactivator known to regulate gene programs in a cell-specific manner in energy-demanding tissues, and its dysfunction has been implicated in numerous neurological and psychiatric disorders. Previous work from the Cowell laboratory indicates that PGC-1α is concentrated in inhibitory interneurons and required for the expression of the calcium buffer parvalbumin (PV) in the cortex; however, the impact of PGC-1α deficiency on inhibitory neurotransmission in the motor cortex is not known. Here, we show that mice lacking PGC-1α exhibit increased amplitudes and decreased frequency of spontaneous inhibitory postsynaptic currents in layer V pyramidal neurons. Upon repetitive train stimulation at the gamma frequency, decreased GABA release is observed. Furthermore, PV-positive interneurons in PGC-1α −/− mice display reductions in intrinsic excitability and excitatory input without changes in gross interneuron morphology. Taken together, these data show that PGC-1α is required for normal inhibitory neurotransmission and cortical PV-positive interneuron function. Given the pronounced motor dysfunction in PGC-1α −/− mice and the essential role of PV-positive interneurons in maintenance of cortical excitatory:inhibitory balance, it is possible that deficiencies in PGC-1α expression could contribute to cortical hyperexcitability and motor abnormalities in multiple neurological disorders.
doi:10.1016/j.neuroscience.2014.04.023
PMCID: PMC4068733  PMID: 24769433

Results 1-25 (1245364)