Nuclear control of respiratory chain expression by nuclear respiratory factors and PGC-1-related coactivator

The Protective Effects of Salidroside from Exhaustive Exercise-Induced Heart Injury by Enhancing the PGC-1 α -NRF1/NRF2 Pathway and Mitochondrial Respiratory Function in Rats

Objective. To test the hypothesis that salidroside (SAL) can protect heart from exhaustive exercise-induced injury by enhancing mitochondrial respiratory function and mitochondrial biogenesis key signaling pathway PGC-1α–NRF1/NRF2 in rats. Methods. Male Sprague-Dawley rats were divided into 4 groups: sedentary (C), exhaustive exercise (EE), low-dose SAL (LS), and high-dose SAL (HS). After one-time exhaustive swimming exercise, we measured the changes in cardiomyocyte ultrastructure and cardiac marker enzymes and mitochondrial electron transport system (ETS) complexes activities in situ. We also measured mitochondrial biogenesis master regulator PGC-1α and its downstream transcription factors, NRF1 and NRF2, expression at gene and protein levels. Results. Compared to C group, the EE group showed marked myocardium ultrastructure injury and decrease of mitochondrial respiratory function (P < 0.05) and protein levels of PGC-1α, NRF1, and NRF2 (P < 0.05) but a significant increase of PGC-1α, NRF1, and NRF2 genes levels (P < 0.05); compared to EE group, SAL ameliorated myocardium injury, increased mitochondrial respiratory function (P < 0.05), and elevated both gene and protein levels of PGC-1α, NRF-1, and NRF-2. Conclusion. Salidroside can protect the heart from exhaustive exercise-induced injury. It might act by improving myocardial mitochondrial respiratory function by stimulating the expression of PGC-1α–NRF1/NRF2 pathway.

The regulation of mitochondrial transcription factor A (Tfam) expression during skeletal muscle cell differentiation

The ATP demand required for muscle development is accommodated by elevations in mitochondrial biogenesis, through the co-ordinated activities of the nuclear and mitochondrial genomes. The most important transcriptional activator of the mitochondrial genome is mitochondrial transcription factor A (Tfam); however, the regulation of Tfam expression during muscle differentiation is not known. Thus, we measured Tfam mRNA levels, mRNA stability, protein expression and localization and Tfam transcription during the progression of muscle differentiation. Parallel 2-fold increases in Tfam protein and mRNA were observed, corresponding with 2-3-fold increases in mitochondrial content. Transcriptional activity of a 2051 bp promoter increased during this differentiation period and this was accompanied by a 3-fold greater Tfam mRNA stabilization. Interestingly, truncations of the promoter at 1706 bp, 978 bp and 393 bp promoter all exhibited 2-3-fold higher transcriptional activity than the 2051 bp construct, indicating the presence of negative regulatory elements within the distal 350 bp of the promoter. Activation of AMP kinase augmented Tfam transcription within the proximal promoter, suggesting the presence of binding sites for transcription factors that are responsive to cellular energy state. During differentiation, the accumulating Tfam protein was progressively distributed to the mitochondrial matrix where it augmented the expression of mtDNA and COX (cytochrome c oxidase) subunit I, an mtDNA gene product. Our data suggest that, during muscle differentiation, Tfam protein levels are regulated by the availability of Tfam mRNA, which is controlled by both transcription and mRNA stability. Changes in energy state and Tfam localization also affect Tfam expression and action in differentiating myotubes.

Lack of aprataxin impairs mitochondrial functions via downregulation of the APE1/NRF1/NRF2 pathway

Ataxia oculomotor apraxia type 1 (AOA1) is an autosomal recessive disease caused by mutations in APTX, which encodes the DNA strand-break repair protein aprataxin (APTX). CoQ10 deficiency has been identified in fibroblasts and muscle of AOA1 patients carrying the common W279X mutation, and aprataxin has been localized to mitochondria in neuroblastoma cells, where it enhances preservation of mitochondrial function. In this study, we show that aprataxin deficiency impairs mitochondrial function, independent of its role in mitochondrial DNA repair. The bioenergetics defect in AOA1-mutant fibroblasts and APTX-depleted Hela cells is caused by decreased expression of SDHA and genes encoding CoQ biosynthetic enzymes, in association with reductions of APE1, NRF1 and NRF2. The biochemical and molecular abnormalities in APTX-depleted cells are recapitulated by knockdown of APE1 in Hela cells and are rescued by overexpression of NRF1/2. Importantly, pharmacological upregulation of NRF1 alone by 5-aminoimidazone-4-carboxamide ribonucleotide does not rescue the phenotype, which, in contrast, is reversed by the upregulation of NRF2 by rosiglitazone. Accordingly, we propose that the lack of aprataxin causes reduction of the pathway APE1/NRF1/NRF2 and their target genes. Our findings demonstrate a critical role of APTX in transcription regulation of mitochondrial function and the pathogenesis of AOA1 via a novel pathomechanistic pathway, which may be relevant to other neurodegenerative diseases.

Beneficial Effect of Flavone Derivatives on Aβ-Induced Memory Deficit Is Mediated by Peroxisome Proliferator-Activated Receptor γ Coactivator 1α: A Comparative Study

In the present study, the neuroprotective effect of 5-hydroxy-6,7,4'-trimethoxyflavone (flavone 1), a natural flavone, was investigated in comparison with another flavone, 5,7,4'-trihydroxyflavone (flavone 2) on the hippocampus of amyloid beta (Aβ)-injected rats. Rats were treated with the 2 flavones (1 mg/kg/d) for 1 week before Aβ injection. Seven days after Aβ administration, memory function of rats was assessed in a passive avoidance test (PAT). Changes in the levels of mitochondrial transcription factor A (TFAM), peroxisome proliferator-activated receptor γ coactivator 1 α (PGC-1α), phospho-adenosine monophosphate (AMP)-activated protein kinase (pAMPK), AMPK, phospho-cAMP-responsive element-binding protein (CREB), CREB, and nuclear respiratory factor 1 (NRF-1) proteins were determined by Western blot analysis. Our results showed an improvement in memory in rats pretreated with flavonoids. At the molecular level, phosphorylation of CREB, known as the master modulator of memory processes, increased. On the other hand, the level of mitochondrial biogenesis factors, PGC-1α and its downstream molecules NRF-1 and TFAM significantly increased by dietary administration of 2 flavones. In addition, flavone 1 and flavone 2 prevented mitochondrial swelling and mitochondrial membrane potential reduction. Our results provided evidence that flavone 1 is more effective than flavone 2 presumably due to its O-methylated groups. In conclusion, it seems that in addition to classical antioxidant effect, flavones exert part of their protective effects through mitochondrial biogenesis.

Angiotensin II blockade: how its molecular targets may signal to mitochondria and slow aging. Coincidences with calorie restriction and mTOR inhibition

Caloric restriction (CR), renin angiotensin system blockade (RAS-bl), and rapamycin-mediated mechanistic target of rapamycin (mTOR) inhibition increase survival and retard aging across species. Previously, we have summarized CR and RAS-bl's converging effects, and the mitochondrial function changes associated with their physiological benefits. mTOR inhibition and enhanced sirtuin and KLOTHO signaling contribute to the benefits of CR in aging. mTORC1/mTORC2 complexes contribute to cell growth and metabolic regulation. Prolonged mTORC1 activation may lead to age-related disease progression; thus, rapamycin-mediated mTOR inhibition and CR may extend lifespan and retard aging through mTORC1 interference. Sirtuins by deacetylating histone and transcription-related proteins modulate signaling and survival pathways and mitochondrial functioning. CR regulates several mammalian sirtuins favoring their role in aging regulation. KLOTHO/fibroblast growth factor 23 (FGF23) contribute to control Ca(2+), phosphate, and vitamin D metabolism, and their dysregulation may participate in age-related disease. Here we review how mTOR inhibition extends lifespan, how KLOTHO functions as an aging suppressor, how sirtuins mediate longevity, how vitamin D loss may contribute to age-related disease, and how they relate to mitochondrial function. Also, we discuss how RAS-bl downregulates mTOR and upregulates KLOTHO, sirtuin, and vitamin D receptor expression, suggesting that at least some of RAS-bl benefits in aging are mediated through the modulation of mTOR, KLOTHO, and sirtuin expression and vitamin D signaling, paralleling CR actions in age retardation. Concluding, the available evidence endorses the idea that RAS-bl is among the interventions that may turn out to provide relief to the spreading issue of age-associated chronic disease.

Targets of selection in the Thoroughbred genome contain exercise-relevant gene SNPs associated with elite racecourse performance

Athletic performance is influenced by a complex interplay among the environment and a suite of genes, which contributes to system-wide structure and function. In a panel of elite and non-elite Thoroughbred horses (n=148), we genotyped 68 SNPs in 17 putative exercise-relevant genes chosen from a genome scan for selection. We performed a series of case-control and quantitative association tests for relationships with racecourse performance. Thirteen SNPs in nine genes were significantly (P<0.05) associated with a performance phenotype. We selected five SNPs in four genes (ACSS1, ACN9, COX4I1, PDK4) for validation in an independent sample set of elite and non-elite Thoroughbreds (n=130). Two SNPs in the PDK4 gene were validated (P<0.01) for associations with elite racing performance. When all samples were considered together (n=278), the PDK4_ 38973231 SNP was strongly associated (P<0.0005) with elite racing performance. Individuals with the A:A and A:G genotypes had a 16.2-16.6 lb advantage over G:G individuals in terms of handicap rating. Re-sequencing of the PDK4 gene and further genotyping will be required to identify the causative variant that is likely influencing exercise-induced variation in expression of the gene. Notwithstanding, this information may be employed as a marker for the selection of racehorses with the genetic potential for superior racing ability.

CAPER is vital for energy and redox homeostasis by integrating glucose-induced mitochondrial functions via ERR-α-Gabpa and stress-induced adaptive responses via NF-κB-cMYC

Ever since we developed mitochondria to generate ATP, eukaryotes required intimate mito-nuclear communication. In addition, since reactive oxygen species are a cost of mitochondrial oxidative phosphorylation, this demands safeguards as protection from these harmful byproducts. Here we identified a critical transcriptional integrator which eukaryotes share to orchestrate both nutrient-induced mitochondrial energy metabolism and stress-induced nuclear responses, thereby maintaining carbon-nitrogen balance, and preserving life span and reproductive capacity. Inhibition of nutrient-induced expression of CAPER arrests nutrient-dependent cell proliferation and ATP generation and induces autophagy-mediated vacuolization. Nutrient signaling to CAPER induces mitochondrial transcription and glucose-dependent mitochondrial respiration via coactivation of nuclear receptor ERR-α-mediated Gabpa transcription. CAPER is also a coactivator for NF-κB that directly regulates c-Myc to coordinate nuclear transcriptome responses to mitochondrial stress. Finally, CAPER is responsible for anaplerotic carbon flux into TCA cycles from glycolysis, amino acids and fatty acids in order to maintain cellular energy metabolism to counter mitochondrial stress. Collectively, our studies reveal CAPER as an evolutionarily conserved 'master' regulatory mechanism by which eukaryotic cells control vital homeostasis for both ATP and antioxidants via CAPER-dependent coordinated control of nuclear and mitochondrial transcriptomic programs and their metabolisms. These CAPER dependent bioenergetic programs are highly conserved, as we demonstrated that they are essential to preserving life span and reproductive capacity in human cells-and even in C. elegans.

SIRT1/PGC-1α signaling protects hepatocytes against mitochondrial oxidative stress induced by bile acids

Oxidative stress and mitochondrial dysfunction are hypothesized to contribute to the pathogenesis of chronic cholestatic liver diseases. Silent information regulator 1 (SIRT1) attenuates oxidative stress and improves mitochondrial biogenesis in numerous mitochondrial-related diseases; however, a functional role for SIRT1 in chronic liver cholestasis, characterized by increased levels of toxic bile acids, remains unknown. We show decrease in SIRT1 levels and its activity and impairment of mitochondrial biogenesis in the liver of patients with extrahepatic cholestasis. Moreover, we found that glycochenodeoxycholic acid (GCDCA) stimulated cytotoxicity, disrupted the mitochondrial membrane potential, increased reactive oxygen species production, and decreased mitochondrial mass and mitochondrial DNA content in L02 cells. Consistent with this finding, GCDCA was found to decrease SIRT1 protein expression and activity, thus promoting the deacetylation of peroxisome proliferator-activated receptor gamma, coactivator 1 alpha (PGC-1α), a key enzyme involved in mitochondrial biogenesis and function. Conversely, GCDCA-induced mitochondrial injury was efficiently attenuated by SIRT1 overexpression. In summary, these findings indicate that the loss of SIRT1 may play a crucial role in the pathogenesis of liver damage observed in patients with extrahepatic cholestasis. The findings also indicate that genetic supplementation of SIRT1 can ameliorate GCDCA-induced hepatotoxicity through the activation of PGC-1α-dependent mitochondrial biogenesis.

17β-estradiol prevents cardiac diastolic dysfunction by stimulating mitochondrial function: a preclinical study in a mouse model of a human hypertrophic cardiomyopathy mutation

OBJECTIVE

We investigated the effect of ovariectomy (OVX) and 17β-estradiol (E2) replacement on both mitochondrial and myocardial function in cTnT-Q92 transgenic mice generated by cardiac-restricted expression of a human hypertrophic cardiomyopathy (HCM) mutation.

METHODS

The cTnT-Q92 mice were ovariectomized at twenty weeks of age and were treated with either placebo (OVX group) or E2 (OVX+E2 group) for twelve weeks before being sacrificed. Wild-type and cTnT-Q92 female mice receiving sham operation were used as controls. Indices of diastolic function such as mitral early (E) and late (A) inflow as well as isovolumic relaxation time (IVRT) were measured by echocardiography. A Clark-type electrode was used to detect respiratory control, and ATP levels were determined at the mitochondrial level using HPLC. Key components related to mitochondrial energy metabolism, such as peroxisome proliferator-activated receptor α (PPARα), PPARγ coactivator 1α (PGC-1α) and nuclear respiratory factor-1 (NRF-1), were also analyzed using Western blot and RT-PCR. The levels of oxidative stress markers were determined by measuring malondialdehyde (MDA) using the thiobarbituric acid assay.

RESULTS

The cTnT-Q92 mice had impaired diastolic function compared with wild-type mice (E/A ratio, 1.39 ± 0.04 vs. 1.21 ± 0.01, p<0.001; IVRT, 19.17 ± 0.85 vs. 22.15 ± 1.43 ms, p=0.028). In response to ovariectomy, cardiac function further decreased compared with that observed in cTnT-Q92 mice that received the sham operation (E/A ratio, 1.15 ± 0.04 vs. 1.21 ± 0.01, p<0.001; IVRT, 28.31 ± 0.39 vs. 22.15 ± 1.43 ms, p=0.002). Myocardial energy metabolism, as determined by ATP levels (3.49 ± 0.31 vs. 5.07 ± 0.47 μmol/g, p<0.001), and the mitochondrial respiratory ratio (2.04 ± 0.10 vs. 2.63 ± 0.11, p=0.01) also decreased significantly. By contrast, myocardial concentrations of MDA increased significantly in the OVX group, and PGC-1α, PPARα and NRF-1decreased significantly. E2 supplementation significantly elevated myocardial ATP levels (4.55 ± 0.21 vs. 3.49 ± 0.31 μmol/g, p=0.003) and mitochondrial respiratory function (3.93 ± 0.05 vs. 2.63 ± 0.11, p=0.001); however, it reduced the MDA level (0.21 ± 0.02 vs. 0.36 ± 0.03 nmol/g, p<0.001), which subsequently improved diastolic function (E/A ratio, 1.35 ± 0.06 vs. 1.15 ± 0.04, p<0.001; IVRT, 18.22 ± 1.16 vs. 28.31 ± 0.39 ms, p=0.007).

CONCLUSIONS

Our study has shown that 17β-estradiol improved myocardial diastolic function, prevented myocardial energy dysregulation, and reduced myocardial oxidative stress in cTnT-Q92 mice.

Mitochondrial Diseases Part III: Therapeutic interventions in mouse models of OXPHOS deficiencies

Mitochondrial defects are the cause of numerous disorders affecting the oxidative phosphorylation system (OXPHOS) in humans leading predominantly to neurological and muscular degeneration. The molecular origin, manifestations, and progression of mitochondrial diseases have a broad spectrum, which makes very challenging to find a globally effective therapy. The study of the molecular mechanisms underlying the mitochondrial dysfunction indicates that there is a wide range of pathways, enzymes and molecules that can be potentially targeted for therapeutic purposes. Therefore, focusing on the pathology of the disease is essential to design new treatments. In this review, we will summarize and discuss the different therapeutic interventions tested in some mouse models of mitochondrial diseases emphasizing the molecular mechanisms of action and their potential applications.

Emerging links between E2F control and mitochondrial function

The family of E2F transcription factors is the key downstream target of the retinoblastoma tumor suppressor protein (pRB), which is frequently inactivated in human cancer. E2F is best known for its role in cell-cycle regulation and triggering apoptosis. However, E2F binds to thousands of genes and, thus, could directly influence a number of biologic processes. Given the plethora of potential E2F targets, the major challenge in the field is to identify specific processes in which E2F plays a functional role and the contexts in which a particular subset of E2F targets dictates a biologic outcome. Recent studies implicated E2F in regulation of expression of mitochondria-associated genes. The loss of such regulation results in severe mitochondrial defects. The consequences become evident during irradiation-induced apoptosis, where E2F-deficient cells are insensitive to cell death despite induction of canonical apoptotic genes. Thus, this novel function of E2F may have a major impact on cell viability, and it is independent of induction of apoptotic genes. Here, we discuss the implications of these findings in cancer biology.

Regulation of PGC-1α Isoform Expression in Skeletal Muscles

The coactivator PGC-1α is the key regulator of mitochondrial biogenesis in skeletal muscle. Skeletal muscle expresses several PGC-1α isoforms. This review covers the functional role of PGC-1α isoforms and the regulation of their exercise-associated expression in skeletal muscle. The patterns of PGC-1α mRNA expression may markedly differ at rest and after muscle activity. Different signaling pathways are activated by different physiological stimuli, which regulate the expression of the PGC-1α gene from the canonical and alternative promoters: expression from a canonical (proximal) promoter is regulated by activation of the AMPK; expression from an alternative promoter, via a β2-adrenergic receptor. All transcripts from both promoters are subject to alternative splicing. As a result, truncated isoforms that possess different properties are translated: truncated isoforms are more stable and predominantly activate angiogenesis, whereas full-length isoforms manly regulate mitochondrial biogenesis. The existence of several isoforms partially explains the broad-spectrum function of this protein and allows the organism to adapt to different physiological stimuli. Regulation of the PGC-1α gene expression by different signaling pathways provides ample opportunity for pharmacological influence on the expression of this gene. Those opportunities might be important for the treatment and prevention of various diseases, such as metabolic syndrome and diabetes mellitus. Elucidation of the regulatory mechanisms of the PGC-1α gene expression and their functional role may provide an opportunity to control the expression of different isoforms through exercise and/or pharmacological intervention.

A non-erythropoietic peptide derivative of erythropoietin decreases susceptibility to diet-induced insulin resistance in mice

BACKGROUND AND PURPOSE

The haematopoietic activity of erythropoietin (EPO) is mediated by the classic EPO receptor (EpoR) homodimer, whereas tissue-protective effects are mediated by a heterocomplex between EpoR and the β-common receptor (βcR). Here, we investigated the effects of a novel, selective ligand of this heterocomplex - pyroglutamate helix B surface peptide (pHBSP) - in mice fed a diet enriched in sugars and saturated fats.

EXPERIMENTAL APPROACH

Male C57BL/6J mice were fed a high-fat high-sucrose diet (HFHS) for 22 weeks. pHBSP (30 μg·kg(-1) s.c.) was administered for the last 11 weeks. Biochemical assays, histopathological and immunohistochemical examinations and Western blotting were performed on serum and target organs (liver, kidney and skeletal muscle).

KEY RESULTS

Mice fed with HFHS diet exhibited insulin resistance, hyperlipidaemia, hepatic lipid accumulation and kidney dysfunction. In gastrocnemius muscle, HFHS impaired the insulin signalling pathway and reduced membrane translocation of glucose transporter type 4 and glycogen content. Treatment with pHBSP ameliorated renal function, reduced hepatic lipid deposition, and normalized serum glucose and lipid profiles. These effects were associated with an improvement in insulin sensitivity and glucose uptake in skeletal muscle. Diet-induced overproduction of the myokines IL-6 and fibroblast growth factor-21 were attenuated by pHBSP and, most importantly, pHBSP markedly enhanced mitochondrial biogenesis in skeletal muscle.

CONCLUSIONS AND IMPLICATIONS

Chronic treatment of mice with an EPO derivative, devoid of haematopoietic effects, improved metabolic abnormalities induced by a high-fat high-sucrose diet, by affecting several levels of the insulin signalling and inflammatory cascades within skeletal muscle, while enhancing mitochondrial biogenesis.

Influence of the Prader-Willi syndrome imprinting center on the DNA methylation landscape in the mouse brain

Reduced representation bisulfite sequencing (RRBS) was used to analyze DNA methylation patterns across the mouse brain genome in mice carrying a deletion of the Prader-Willi syndrome imprinting center (PWS-IC) on either the maternally- or paternally-inherited chromosome. Within the ~3.7 Mb imprinted Angelman/Prader-Willi syndrome (AS/PWS) domain, 254 CpG sites were interrogated for changes in methylation due to PWS-IC deletion. Paternally-inherited deletion of the PWS-IC increased methylation levels ~2-fold at each CpG site (compared to wild-type controls) at differentially methylated regions (DMRs) associated with 5' CpG island promoters of paternally-expressed genes; these methylation changes extended, to a variable degree, into the adjacent CpG island shores. Maternal PWS-IC deletion yielded little or no changes in methylation at these DMRs, and methylation of CpG sites outside of promoter DMRs also was unchanged upon maternal or paternal PWS-IC deletion. Using stringent ascertainment criteria, ~750,000 additional CpG sites were also interrogated across the entire mouse genome. This analysis identified 26 loci outside of the imprinted AS/PWS domain showing altered DNA methylation levels of ≥25% upon PWS-IC deletion. Curiously, altered methylation at 9 of these loci was a consequence of maternal PWS-IC deletion (maternal PWS-IC deletion by itself is not known to be associated with a phenotype in either humans or mice), and 10 of these loci exhibited the same changes in methylation irrespective of the parental origin of the PWS-IC deletion. These results suggest that the PWS-IC may affect DNA methylation at these loci by directly interacting with them, or may affect methylation at these loci through indirect downstream effects due to PWS-IC deletion. They further suggest the PWS-IC may have a previously uncharacterized function outside of the imprinted AS/PWS domain.

Nonalcoholic Fatty liver disease: pathogenesis and therapeutics from a mitochondria-centric perspective

Nonalcoholic fatty liver disease (NAFLD) describes a spectrum of disorders characterized by the accumulation of triglycerides within the liver. The global prevalence of NAFLD has been increasing as the obesity epidemic shows no sign of relenting. Mitochondria play a central role in hepatic lipid metabolism and also are affected by upstream signaling pathways involved in hepatic metabolism. This review will focus on the role of mitochondria in the pathophysiology of NAFLD and touch on some of the therapeutic approaches targeting mitochondria as well as metabolically important signaling pathways. Mitochondria are able to adapt to lipid accumulation in hepatocytes by increasing rates of beta-oxidation; however increased substrate delivery to the mitochondrial electron transport chain (ETC) leads to increased reactive oxygen species (ROS) production and eventually ETC dysfunction. Decreased ETC function combined with increased rates of fatty acid beta-oxidation leads to the accumulation of incomplete products of beta-oxidation, which combined with increased levels of ROS contribute to insulin resistance. Several related signaling pathways, nuclear receptors, and transcription factors also regulate hepatic lipid metabolism, many of which are redox sensitive and regulated by ROS.

Effects of PPARα/PGC-1α on the myocardial energy metabolism during heart failure in the doxorubicin induced dilated cardiomyopathy in mice

OBJECTIVE

This study aims to investigate the effects and their mechanisms of PPARα and PGC-1α pathways in doxorubicin induced dilated cardiomyopathy in mice.

METHODS

The model of dilated cardiomyopathy (DCM) was established by injecting doxorubicin in mice. The 40 surviving mice were divided randomly into control group, doxorubicin model group, PPARα inhibitor and PPARα agonist group. The PPARα/PGC-1α proteins were detected. The size of adenine acid pool (ATP, ADP, AMP) and phosphocreatine (Pcr) in mitochondria were measured by HPLC. The ANT activity was detected by the atractyloside-inhibitor stop technique. The echocardiography and hemodynamic changes were detected in each group after PPARα inhibitor and PPARα agonist treatment for 2 weeks.

RESULTS

The DOX induced DCM model were successfully established. The expression of PPARα and PGC-1α protein level in normal group were significantly higher than that in DOX model group (P<0.05). Both the high-energy phosphate content and the transport activity of ANT were decreased in DOX group (P<0.05), and the hemodynamic parameters were disorder (P<0.01). Compared with Dox group, PPARα inhibitor intervention significantly reduce the expression of PPARα/PGC-1α, high-energy phosphate content in the mitochondria had no significant change (P>0.05), but the ANT transport activity of mitochondria decreased significantly (P<0.05), the left ventricular function decreased. On the other side, PPARα agonist intervention significantly increased the expression of PPARα and PGC-1α, improved transport activity of ANT, the hemodynamic parameters was ameliorated (P<0.05), but the high-energy phosphate content of mitochondria did not change significantly (P>0.05).

CONCLUSION

There was lower expression of PPARα and PGC-1α in DOC induced DCM in mice. Promotion of PPARα can improve myocardia energy metabolism and delay the occurrence of heart failure.

GABP transcription factor (nuclear respiratory factor 2) is required for mitochondrial biogenesis

Mitochondria are membrane-bound cytoplasmic organelles that serve as the major source of ATP production in eukaryotic cells. GABP (also known as nuclear respiratory factor 2) is a nuclear E26 transformation-specific transcription factor (ETS) that binds and activates mitochondrial genes that are required for electron transport and oxidative phosphorylation. We conditionally deleted Gabpa, the DNA-binding component of this transcription factor complex, from mouse embryonic fibroblasts (MEFs) to examine the role of Gabp in mitochondrial biogenesis, function, and gene expression. Gabpα loss modestly reduced mitochondrial mass, ATP production, oxygen consumption, and mitochondrial protein synthesis but did not alter mitochondrial morphology, membrane potential, apoptosis, or the expression of several genes that were previously reported to be GABP targets. However, the expression of Tfb1m, a methyltransferase that modifies ribosomal rRNA and is required for mitochondrial protein translation, was markedly reduced in Gabpα-null MEFs. We conclude that Gabp regulates Tfb1m expression and plays an essential, nonredundant role in mitochondrial biogenesis.

Delphinidin inhibits VEGF induced-mitochondrial biogenesis and Akt activation in endothelial cells

Delphinidin, an anthocyanin present in red wine, has been reported to exert vasculoprotective properties on endothelial cells, including vasorelaxing and anti-apoptotic effects. Moreover, delphinidin treatment in a rat model of post-ischemic neovascularization has been described to exert anti-angiogenic property. Angiogenesis is an energetic process and VEGF-induced angiogenesis is associated with mitochondrial biogenesis. However, whether delphinidin induces changes in mitochondrial biogenesis has never been addressed. Effects of delphinidin were investigated in human endothelial cells at a concentration described to be anti-angiogenic in vitro (10(-2)g/l). mRNA expression of mitochondrial biogenesis factors, mitochondrial respiration, DNA content and enzyme activities were assessed after 48 h of stimulation. Delphinidin increased mRNA expression of several mitochondrial biogenesis factors, including NRF1, ERRα, Tfam, Tfb2m and PolG but did not affect neither mitochondrial respiration, DNA content nor enzyme activities. In presence of delphinidin, VEGF failed to increase mitochondrial respiration, DNA content, complex IV activity and Akt activation in endothelial cells. These results suggest a possible association between inhibition of VEGF-induced mitochondrial biogenesis through Akt pathway by delphinidin and its anti-angiogenic effect, providing a novel mechanism sustaining the beneficial effect of delphinidin against pathologies associated with excessive angiogenesis such as cancers.

Salidroside stimulates mitochondrial biogenesis and protects against H₂O₂-induced endothelial dysfunction

Salidroside (SAL) is an active component of Rhodiola rosea with documented antioxidative properties. The purpose of this study is to explore the mechanism of the protective effect of SAL on hydrogen peroxide- (H₂O₂-) induced endothelial dysfunction. Pretreatment of the human umbilical vein endothelial cells (HUVECs) with SAL significantly reduced the cytotoxicity brought by H₂O₂. Functional studies on the rat aortas found that SAL rescued the endothelium-dependent relaxation and reduced superoxide anion (O2^∙−) production induced by H₂O₂. Meanwhile, SAL pretreatment inhibited H₂O₂-induced nitric oxide (NO) production. The underlying mechanisms involve the inhibition of H₂O₂-induced activation of endothelial nitric oxide synthase (eNOS), adenosine monophosphate-activated protein kinase (AMPK), and Akt, as well as the redox sensitive transcription factor, NF-kappa B (NF-κB). SAL also increased mitochondrial mass and upregulated the mitochondrial biogenesis factors, peroxisome proliferator-activated receptor gamma-coactivator-1alpha (PGC-1α), and mitochondrial transcription factor A (TFAM) in the endothelial cells. H₂O₂-induced mitochondrial dysfunction, as demonstrated by reduced mitochondrial membrane potential (Δψm) and ATP production, was rescued by SAL pretreatment. Taken together, these findings implicate that SAL could protect endothelium against H₂O₂-induced injury via promoting mitochondrial biogenesis and function, thus preventing the overactivation of oxidative stress-related downstream signaling pathways.

Gluconeogenic signals regulate iron homeostasis via hepcidin in mice

BACKGROUND & AIMS

Hepatic gluconeogenesis provides fuel during starvation, and is abnormally induced in obese individuals or those with diabetes. Common metabolic disorders associated with active gluconeogenesis and insulin resistance (obesity, metabolic syndrome, diabetes, and nonalcoholic fatty liver disease) have been associated with alterations in iron homeostasis that disrupt insulin sensitivity and promote disease progression. We investigated whether gluconeogenic signals directly control Hepcidin, an important regulator of iron homeostasis, in starving mice (a model of persistently activated gluconeogenesis and insulin resistance).

METHODS

We investigated hepatic regulation of Hepcidin expression in C57BL/6Crl, 129S2/SvPas, BALB/c, and Creb3l3-/- null mice. Mice were fed a standard, iron-balanced chow diet or an iron-deficient diet for 9 days before death, or for 7 days before a 24- to 48-hour starvation period; liver and spleen tissues then were collected and analyzed by quantitative reverse-transcription polymerase chain reaction and immunoblot analyses. Serum levels of iron, hemoglobin, Hepcidin, and glucose also were measured. We analyzed human hepatoma (HepG2) cells and mouse primary hepatocytes to study transcriptional control of Hamp (the gene that encodes Hepcidin) in response to gluconeogenic stimuli using small interfering RNA, luciferase promoter, and chromatin immunoprecipitation analyses.

RESULTS

Starvation led to increased transcription of the gene that encodes phosphoenolpyruvate carboxykinase 1 (a protein involved in gluconeogenesis) in livers of mice, increased levels of Hepcidin, and degradation of Ferroportin, compared with nonstarved mice. These changes resulted in hypoferremia and iron retention in liver tissue. Livers of starved mice also had increased levels of Ppargc1a mRNA and Creb3l3 mRNA, which encode a transcriptional co-activator involved in energy metabolism and a liver-specific transcription factor, respectively. Glucagon and a cyclic adenosine monophosphate analog increased promoter activity and transcription of Hamp in cultured liver cells; levels of Hamp were reduced after administration of small interfering RNAs against Ppargc1a and Creb3l3. PPARGC1A and CREB3L3 bound the Hamp promoter to activate its transcription in response to a cyclic adenosine monophosphate analog. Creb3l3-/- mice did not up-regulate Hamp or become hypoferremic during starvation.

CONCLUSIONS

We identified a link between glucose and iron homeostasis, showing that Hepcidin is a gluconeogenic sensor in mice during starvation. This response is involved in hepatic metabolic adaptation to increased energy demands; it preserves tissue iron for vital activities during food withdrawal, but can cause excessive iron retention and hypoferremia in disorders with persistently activated gluconeogenesis and insulin resistance.

Stahlmann C, Slobodskoy Y, Müller UC, Hartmann T, Stein R, Grimm MOW. Upregulation of PGC-1α expression by Alzheimer's disease-associated pathway: presenilin 1/amyloid precursor protein (APP)/intracellular domain of APP

Cleavage of amyloid precursor protein (APP) by β- and γ-secretase generates amyloid-β (Aβ) and APP intracellular domain (AICD) peptides. Presenilin (PS) 1 or 2 is the catalytic component of the γ-secretase complex. Mitochondrial dysfunction is an established phenomenon in Alzheimer’s disease (AD), but the causes and role of PS1, APP, and APP’s cleavage products in this process are largely unknown. We studied the effect of these AD-associated molecules on mitochondrial features. Using cells deficient in PSs expression, expressing human wild-type PS1, or PS1 familial AD (FAD) mutants, we found that PS1 affects mitochondrial energy metabolism (ATP levels and oxygen consumption) and expression of mitochondrial proteins. These effects were associated with enhanced expression of the mitochondrial master transcriptional coactivator PGC-1α and its target genes. Importantly, PS1-FAD mutations decreased PS1’s ability to enhance PGC-1α mRNA levels. Analyzing the effect of APP and its γ-secretase-derived cleavage products Aβ and AICD on PGC-1α expression showed that APP and AICD increase PGC-1α expression. Accordingly, PGC-1α mRNA levels in cells deficient in APP/APLP2 or expressing APP lacking its last 15 amino acids were lower than in control cells, and treatment with AICD, but not with Aβ, enhanced PGC-1α mRNA levels in these and PSs-deficient cells. In addition, knockdown of the AICD-binding partner Fe65 reduced PGC-1α mRNA levels. Importantly, APP/AICD increases PGC-1α expression also in the mice brain. Our results therefore suggest that APP processing regulates mitochondrial function and that impairments in the newly discovered PS1/APP/AICD/PGC-1α pathway may lead to mitochondrial dysfunction and neurodegeneration.

Dual mode action of mangiferin in mouse liver under high fat diet

Chronic over-nutrition is a major contributor to the spread of obesity and its related metabolic disorders. Development of therapeutics has been slow compared to the speedy increase in occurrence of these metabolic disorders. We have identified a natural compound, mangiferin (MGF) (a predominant component of the plants of Anemarrhena asphodeloides and Mangifera indica), that can protect against high fat diet (HFD) induced obesity, hyperglycemia, insulin resistance and hyperlipidemia in mice. However, the molecular mechanisms whereby MGF exerts these beneficial effects are unknown. To understand MGF mechanisms of action, we performed unbiased quantitative proteomic analysis of protein profiles in liver of mice fed with HFD utilizing 15N metabolically labeled liver proteins as internal standards. We found that out of 865 quantified proteins 87 of them were significantly differentially regulated by MGF. Among those 87 proteins, 50% of them are involved in two major processes, energy metabolism and biosynthesis of metabolites. Further classification indicated that MGF increased proteins important for mitochondrial biogenesis and oxidative activity including oxoglutarate dehydrogenase E1 (Dhtkd1) and cytochrome c oxidase subunit 6B1 (Cox6b1). Conversely, MGF reduced proteins critical for lipogenesis such as fatty acid stearoyl-CoA desaturase 1 (Scd1) and acetyl-CoA carboxylase 1 (Acac1). These mass spectrometry data were confirmed and validated by western blot assays. Together, data indicate that MGF upregulates proteins pivotal for mitochondrial bioenergetics and downregulates proteins controlling de novo lipogenesis. This novel mode of dual pharmacodynamic actions enables MGF to enhance energy expenditure and inhibit lipogenesis, and thereby correct HFD induced liver steatosis and prevent adiposity. This provides a molecular basis supporting development of MGF or its metabolites into therapeutics to treat metabolic disorders.

The impact of mitochondrial DNA and nuclear genes related to mitochondrial functioning on the risk of Parkinson's disease

Mitochondrial dysfunction and oxidative stress are the major factors implicated in Parkinson’s disease (PD) pathogenesis. The maintenance of healthy mitochondria is a very complex process coordinated bi-genomically. Here, we review association studies on mitochondrial haplogroups and subhaplogroups, discussing the underlying molecular mechanisms. We also focus on variation in the nuclear genes (NDUFV2, PGC-1alpha, HSPA9, LRPPRC, MTIF3, POLG1, and TFAM encoding NADH dehydrogenase (ubiquinone) flavoprotein 2, peroxisome proliferator-activated receptor gamma coactivator 1-alpha, mortalin, leucine-rich pentatricopeptide repeat containing protein, translation initiation factor 3, mitochondrial DNA polymerase gamma, and mitochondrial transcription factor A, respectively) primarily linked to regulation of mitochondrial functioning that recently have been associated with PD risk. Possible interactions between mitochondrial and nuclear genetic variants and related proteins are discussed.

β-D-glucan inhibits endocrine-resistant breast cancer cell proliferation and alters gene expression

Endocrine therapies have been successfully used for breast cancer patients with estrogen receptor α (ERα) positive tumors, but ∼40% of patients relapse due to endocrine resistance. β-glucans are components of plant cell walls that have immunomodulatory and anticancer activity. The objective of this study was to examine the activity of β-D-glucan, purified from barley, in endocrine-sensitive MCF-7 versus endocrine-resistant LCC9 and LY2 breast cancer cells. β-D-glucan dissolved in DMSO but not water inhibited MCF-7 cell proliferation in a concentration-dependent manner as measured by BrdU incorporation with an IC₅₀ of ∼164±12 μg/ml. β-D-glucan dissolved in DMSO inhibited tamoxifen/endocrine-resistant LCC9 and LY2 cell proliferation with IC₅₀ values of 4.6±0.3 and 24.2±1.4 μg/ml, respectively. MCF-10A normal breast epithelial cells showed a higher IC₅₀ ∼464 μg/ml and the proliferation of MDA-MB-231 triple negative breast cancer cells was not inhibited by β-D-glucan. Concentration-dependent increases in the BAX/BCL2 ratio and cell death with β-D-glucan were observed in MCF-7 and LCC9 cells. PCR array analysis revealed changes in gene expression in response to 24-h treatment with 10 or 50 μg/ml β-D-glucan that were different between MCF-7 and LCC9 cells as well as differences in basal gene expression between the two cell lines. Select results were confirmed by quantitative real-time PCR demonstrating that β-D-glucan increased RASSF1 expression in MCF-7 cells and IGFBP3, CTNNB1 and ERβ transcript expression in LCC9 cells. Our data indicate that β-D-glucan regulates breast cancer-relevant gene expression and may be useful for inhibiting endocrine-resistant breast cancer cell proliferation.

Tetramethylpyrazine ameliorates high glucose-induced endothelial dysfunction by increasing mitochondrial biogenesis

Tetramethylpyrazine (TMP) is an active compound isolated from a Chinese herbal prescription that is widely used in traditional Chinese medicine for the treatment of inflammatory and cardiovascular diseases. We have previously reported that TMP acts as a potent antioxidant protecting endothelial cells against high glucose-induced damages. However, the molecular mechanism responsible for the antioxidant effect of TMP remains to be elucidated. In this study, we show that TMP increases nitric oxide production in endothelial cells and promotes endothelium-dependent relaxation in rate aortic rings. The antioxidant effect of TMP appears attributable to its ability to activate the mitochondrial biogenesis, as reflected in an up-regulation of complex III and amelioration of mitochondrial membrane potential. Furthermore, TMP is able to reverse high glucose-induced suppression of SIRT1 and the biogenesis-related factors, including PGC-1α, NRF1 and TFAM, suggesting a new molecular mechanism underlying the protective effect of TMP on the endothelium.

Prenatal Hypoxia Reduces Mitochondrial Protein Levels and Cytochrome c Oxidase Activity in Offspring Guinea Pig Hearts

Prenatal hypoxia (HPX) reduces mitochondrial cytochrome c oxidase (CCO and COX) activity in fetal guinea pig (GP) hearts. The aim of this study was to quantify the lasting effects of chronic prenatal HPX on cardiac mitochondrial enzyme activity and protein expression in offspring hearts. Pregnant GPs were exposed to either normoxia (NMX) or HPX (10.5%O₂) during the last 14 days of pregnancy. Both NMX and HPX fetuses, delivered vaginally, were housed under NMX conditions until 90 days of age. Total RNA and mitochondrial fractions were isolated from hearts of anesthetized NMX and HPX offspring and showed decreased levels of CCO but not medium-chain acyl dehydrogenase activity, protein levels of nuclear- and mitochondrial-encoded COX4 and COX1, respectively, and messenger RNA expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha, COX5b, and 4.1 compared to NMX controls. Prenatal HPX may alter mitochondrial function in the offspring by disrupting protein expression associated with the respiratory chain.

PGC-1α overexpression exacerbates β-amyloid and tau deposition in a transgenic mouse model of Alzheimer's disease

The peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α) interacts with various transcription factors involved in energy metabolism and in the regulation of mitochondrial biogenesis. PGC-1α mRNA levels are reduced in a number of neurodegenerative diseases and contribute to disease pathogenesis, since increased levels ameliorate behavioral defects and neuropathology of Huntington's disease, Parkinson's disease, and amyotrophic lateral sclerosis. PGC-1α and its downstream targets are reduced both in postmortem brain tissue of patients with Alzheimer's disease (AD) and in transgenic mouse models of AD. Therefore, we investigated whether increased expression of PGC-1α would exert beneficial effects in the Tg19959 transgenic mouse model of AD; Tg19959 mice express the human amyloid precursor gene (APP) with 2 familial AD mutations and develop increased β-amyloid levels, plaque deposition, and memory deficits by 2-3 mo of age. Rather than an improvement, the cross of the Tg19959 mice with mice overexpressing human PGC-1α exacerbated amyloid and tau accumulation. This was accompanied by an impairment of proteasome activity. PGC-1α overexpression induced mitochondrial abnormalities, neuronal cell death, and an exacerbation of behavioral hyperactivity in the Tg19959 mice. These findings show that PGC-1α overexpression exacerbates the neuropathological and behavioral deficits that occur in transgenic mice with mutations in APP that are associated with human AD.

Glycogen synthase kinase-3 (GSK3) controls deoxyglucose-induced mitochondrial biogenesis in human neuroblastoma SH-SY5Y cells

Mitochondrial biogenesis, a mitochondrial growth and division process, is crucial for adaptation to metabolic stress. The present study demonstrated that treatment with a specific inhibitor of GSK3, SB216763, attenuated induction of mitochondrial biogenesis by a glycolysis inhibitor, 2-deoxyglucose (2-DG), without affecting this biogenesis at basal condition. Additionally, overexpression of WT-GSK3β promoted whereas GSK3β-KD attenuated 2-DG-induced mitochondrial protein expression. The mitochondrial biogenesis attenuation by GSK3 inhibitor was not due to inhibition of protein degradation. Furthermore, GSK3 inhibition further reduced transcription of mitochondrial (COXII), but not nuclear (VDAC) gene by 2-DG suggesting its participation in 2-DG-induced mitochondrial transcription. Together, our results show that GSK3 regulates mitochondrial biogenesis induced by glycolysis inhibition.

Free radical biology for medicine: learning from nonalcoholic fatty liver disease

Reactive oxygen species, when released under controlled conditions and limited amounts, contribute to cellular proliferation, senescence, and survival by acting as signaling intermediates. In past decades there has been an epidemic diffusion of nonalcoholic fatty liver disease (NAFLD) that represents the result of the impairment of lipid metabolism, redox imbalance, and insulin resistance in the liver. To date, most studies and reviews have been focused on the molecular mechanisms by which fatty liver progresses to steatohepatitis, but the processes leading toward the development of hepatic steatosis in NAFLD are not fully understood yet. Several nuclear receptors, such as peroxisome proliferator-activated receptors (PPARs) α/γ/δ, PPARγ coactivators 1α and 1β, sterol-regulatory element-binding proteins, AMP-activated protein kinase, liver-X-receptors, and farnesoid-X-receptor, play key roles in the regulation of lipid homeostasis during the pathogenesis of NAFLD. These nuclear receptors may act as redox sensors and may modulate various metabolic pathways in response to specific molecules that act as ligands. It is conceivable that a redox-dependent modulation of lipid metabolism, nuclear receptor-mediated, could cause the development of hepatic steatosis and insulin resistance. Thus, this network may represent a potential therapeutic target for the treatment and prevention of hepatic steatosis and its progression to steatohepatitis. This review summarizes the redox-dependent factors that contribute to metabolism alterations in fatty liver with a focus on the redox control of nuclear receptors in normal liver as well as in NAFLD.

Mitochondria-Targeted Antioxidant SS31 Prevents Amyloid Beta-Induced Mitochondrial Abnormalities and Synaptic Degeneration in Alzheimer's Disease

In neuronal systems, the health and activity of mitochondria and synapses are tightly coupled. For this reason, it has been postulated that mitochondrial abnormalities may, at least in part, drive neurodegeneration in conditions such as Alzheimer’s disease (AD). Mounting evidence from multiple Alzheimer’s disease cell and mouse models and postmortem brains suggest that loss of mitochondrial integrity may be a key factor that mediates synaptic loss. Therefore, the prevention or rescue of mitochondrial dysfunction may help delay or altogether prevent AD-associated neurodegeneration. Since mitochondrial health is heavily dependent on antioxidant defenses, researchers have begun to explore the use of mitochondria-targeted antioxidants as therapeutic tools to prevent neurodegenerative diseases. This review will highlight advances made using a model mitochondria-targeted antioxidant peptide, SS31, as a potential treatment for AD.

Genomic and non-genomic regulation of PGC1 isoforms by estrogen to increase cerebral vascular mitochondrial biogenesis and reactive oxygen species protection

We previously found that estrogen exerts a novel protective effect on mitochondria in brain vasculature. Here we demonstrate in rat cerebral blood vessels that 17β-estradiol (estrogen), both in vivo and ex vivo, affects key transcriptional coactivators responsible for mitochondrial regulation. Treatment of ovariectomized rats with estrogen in vivo lowered mRNA levels of peroxisome proliferator-activated receptor-γ coactivator-1 alpha (PGC-1α) but increased levels of the other PGC-1 isoforms: PGC-1β and PGC-1 related coactivator (PRC). In vessels ex vivo, estrogen decreased protein levels of PGC-1α via activation of phosphatidylinositol 3-kinase (PI3K). Estrogen treatment also increased phosphorylation of forkhead transcription factor, FoxO1, a known pathway for PGC-1α downregulation. In contrast to the decrease in PGC-1α, estrogen increased protein levels of nuclear respiratory factor 1, a known PGC target and mediator of mitochondrial biogenesis. The latter effect of estrogen was independent of PI3K, suggesting a separate mechanism consistent with increased expression of PGC-1β and PRC. We demonstrated increased mitochondrial biogenesis following estrogen treatment in vivo; cerebrovascular levels of mitochondrial transcription factor A and electron transport chain subunits as well as the mitochondrial/nuclear DNA ratio were increased. We examined a downstream target of PGC-1β, glutamate-cysteine ligase (GCL), the rate-limiting enzyme for glutathione synthesis. In vivo estrogen increased protein levels of both GCL subunits and total glutathione levels. Together these data show estrogen differentially regulates PGC-1 isoforms in brain vasculature, underscoring the importance of these coactivators in adapting mitochondria in specific tissues. By upregulating PGC-1β and/or PRC, estrogen appears to enhance mitochondrial biogenesis, function and reactive oxygen species protection.

Decoding a signature-based model of transcription cofactor recruitment dictated by cardinal cis-regulatory elements in proximal promoter regions

Genome-wide maps of DNase I hypersensitive sites (DHSs) reveal that most human promoters contain perpetually active cis-regulatory elements between −150 bp and +50 bp (−150/+50 bp) relative to the transcription start site (TSS). Transcription factors (TFs) recruit cofactors (chromatin remodelers, histone/protein-modifying enzymes, and scaffold proteins) to these elements in order to organize the local chromatin structure and coordinate the balance of post-translational modifications nearby, contributing to the overall regulation of transcription. However, the rules of TF-mediated cofactor recruitment to the −150/+50 bp promoter regions remain poorly understood. Here, we provide evidence for a general model in which a series of cis-regulatory elements (here termed ‘cardinal’ motifs) prefer acting individually, rather than in fixed combinations, within the −150/+50 bp regions to recruit TFs that dictate cofactor signatures distinctive of specific promoter subsets. Subsequently, human promoters can be subclassified based on the presence of cardinal elements and their associated cofactor signatures. In this study, furthermore, we have focused on promoters containing the nuclear respiratory factor 1 (NRF1) motif as the cardinal cis-regulatory element and have identified the pervasive association of NRF1 with the cofactor lysine-specific demethylase 1 (LSD1/KDM1A). This signature might be distinctive of promoters regulating nuclear-encoded mitochondrial and other particular genes in at least some cells. Together, we propose that decoding a signature-based, expanded model of control at proximal promoter regions should lead to a better understanding of coordinated regulation of gene transcription.

Human cells exploit different mechanisms to coordinate the expression of both protein-coding and non-coding RNAs. Elucidating these mechanisms is essential to understanding normal physiology and disease. In our attempt to identify new regulatory layers acting particularly at proximal promoters, we have computationally analyzed the genomic sequences located from −150 bp to +50 bp relative to the transcriptional start site (TSS), which are often at the center of ‘open’ chromatin regions in human promoters. We have confirmed the presence of a series of cis-regulatory elements (here referred to as ‘cardinal’ motifs) that show a strong preference for these short regions. Interestingly, these elements tend to act independently rather than in fixed combinations. Therefore, we propose that they confer unique regulatory features to the human promoter subsets that contain each of these particular elements. In agreement with this model, we have identified a large repertoire of preferential partnerships between transcription factors recognizing cardinal motifs and their associated proteins (cofactors), thus decoding a signature-based model that distinguishes distinctive regulatory types of promoters based on cardinal motifs. These signatures may underlie a new layer of transcriptional regulation to orchestrate coordinated gene expression in human promoters.

Drosophila Erect wing (Ewg) controls mitochondrial fusion during muscle growth and maintenance by regulation of the Opa1-like gene

Mitochondrial biogenesis and morphological changes are associated with tissue-specific functional demand, but the factors and pathways that regulate these processes have not been completely identified. A lack of mitochondrial fusion has been implicated in various developmental and pathological defects. The spatiotemporal regulation of mitochondrial fusion in a tissue such as muscle is not well understood. Here, we show in Drosophila indirect flight muscles (IFMs) that the nuclear-encoded mitochondrial inner membrane fusion gene, Opa1-like, is regulated in a spatiotemporal fashion by the transcription factor/co-activator Erect wing (Ewg). In IFMs null for Ewg, mitochondria undergo mitophagy and/or autophagy accompanied by reduced mitochondrial functioning and muscle degeneration. By following the dynamics of mitochondrial growth and shape in IFMs, we found that mitochondria grow extensively and fuse during late pupal development to form the large tubular mitochondria. Our evidence shows that Ewg expression during early IFM development is sufficient to upregulate Opa1-like, which itself is a requisite for both late pupal mitochondrial fusion and muscle maintenance. Concomitantly, by knocking down Opa1-like during early muscle development, we show that it is important for mitochondrial fusion, muscle differentiation and muscle organization. However, knocking down Opa1-like, after the expression window of Ewg did not cause mitochondrial or muscle defects. This study identifies a mechanism by which mitochondrial fusion is regulated spatiotemporally by Ewg through Opa1-like during IFM differentiation and growth.

Estradiol and tamoxifen regulate NRF-1 and mitochondrial function in mouse mammary gland and uterus

Nuclear respiratory factor-1 (NRF-1) stimulates the transcription of nuclear-encoded genes that regulate mitochondrial (mt) genome transcription and biogenesis. We reported that estradiol (E2) and 4-hydroxytamoxifen (4-OHT) stimulate NRF-1 transcription in an estrogen receptor α (ERα)- and ERβ-dependent manner in human breast cancer cells. The aim of this study was to determine whether E2 and 4-OHT increase NRF-1 in vivo. Here, we report that E2 and 4-OHT increase NRF-1 expression in mammary gland (MG) and uterus of ovariectomized C57BL/6 mice in a time-dependent manner. E2 increased NRF-1 protein in the uterus and MG; however, in MG, 4-OHT increased Nrf1 mRNA but not protein. Chromatin immunoprecipitation assays revealed increased in vivo recruitment of ERα to the Nrf1 promoter and intron 3 in MG and uterus 6 h after E2 and 4-OHT treatment, commensurate with increased NRF-1 expression. E2- and 4-OHT-induced increases in NRF-1 and its target genes Tfam, Tfb1m, and Tfb2m were coordinated in MG but not in uterus due to uterine-selective inhibition of the expression of the NRF-1 coactivators Ppargc1a and Ppargc1b by E2 and 4-OHT. E2 transiently increased NRF-1 and PGC-1α nuclear staining while reducing PGC-1α in uterus. E2, not 4-OHT, activates mt biogenesis in MG and uterus in a time-dependent manner. E2 increased mt outer membrane Tomm40 protein levels in MG and uterus whereas 4-OHT increased Tomm40 only in uterus. These data support the hypothesis of tissue-selective regulation of NRF-1 and its downstream targets by E2 and 4-OHT in vivo.

Neuron-specific specificity protein 4 bigenomically regulates the transcription of all mitochondria- and nucleus-encoded cytochrome c oxidase subunit genes in neurons

Neurons are highly dependent on oxidative metabolism for their energy supply, and cytochrome c oxidase (COX) is a key energy-generating enzyme in the mitochondria. A unique feature of COX is that it is one of only four proteins in mammalian cells that are bigenomically regulated. Of its thirteen subunits, three are encoded in the mitochondrial genome and ten are nuclear-encoded on nine different chromosomes. The mechanism of regulating this multisubunit, bigenomic enzyme poses a distinct challenge. In recent years, we found that nuclear respiratory factors 1 and 2 (NRF-1 and NRF-2) mediate such bigenomic coordination. The latest candidate is the specificity factor (Sp) family of proteins. In N2a cells, we found that Sp1 regulates all 13 COX subunits. However, we discovered recently that in primary neurons, it is Sp4 and not Sp1 that regulates some of the key glutamatergic receptor subunit genes. The question naturally arises as to the role of Sp4 in regulating COX in primary neurons. The present study utilized multiple approaches, including chromatin immunoprecipitation, promoter mutational analysis, knockdown and over-expression of Sp4, as well as functional assays to document that Sp4 indeed functionally regulate all 13 subunits of COX as well as mitochondrial transcription factors A and B. The present study discovered that among the specificity family of transcription factors, it is the less known neuron-specific Sp4 that regulates the expression of all 13 subunits of mitochondrial cytochrome c oxidase (COX) enzyme in primary neurons. Sp4 also regulates the three mitochondrial transcription factors (TFAM, TFB1M, and TFB2M) and a COX assembly protein SURF-1 in primary neurons.

Aluminium induced oxidative stress results in decreased mitochondrial biogenesis via modulation of PGC-1α expression

The present investigation was carried out to elucidate a possible molecular mechanism related to the effects of aluminium-induced oxidative stress on various mitochondrial respiratory complex subunits with special emphasis on the role of Peroxisome proliferator activated receptor gamma co-activator 1α (PGC-1α) and its downstream targets i.e. Nuclear respiratory factor-1(NRF-1), Nuclear respiratory factor-2(NRF-2) and Mitochondrial transcription factor A (Tfam) in mitochondrial biogenesis. Aluminium lactate (10mg/kgb.wt./day) was administered intragastrically to rats for 12 weeks. After 12 weeks of exposure, we found an increase in ROS levels, mitochondrial DNA oxidation and decrease in citrate synthase activity in the Hippocampus (HC) and Corpus striatum (CS) regions of rat brain. On the other hand, there was a decrease in the mRNA levels of the mitochondrial encoded subunits-NADH dehydrogenase (ND) subunits i.e. ND1, ND2, ND3, Cytochrome b (Cytb), Cytochrome oxidase (COX) subunits i.e. COX1, COX3, ATP synthase (ATPase) subunit 6 along with reduced expression of nuclear encoded subunits COX4, COX5A, COX5B of Electron transport chain (ETC). Besides, a decrease in mitochondrial DNA copy number and mitochondrial content in both regions of rat brain was observed. The PGC-1α was down-regulated in aluminium treated rats along with NRF-1, NRF-2 and Tfam, which act downstream from PGC-1α in aluminium treated rats. Electron microscopy results revealed a significant increase in the mitochondrial swelling, loss of cristae, chromatin condensation and decreases in mitochondrial number in case of aluminium treated rats as compared to control. So, PGC-1α seems to be a potent target for aluminium neurotoxicity, which makes it an almost ideal target to control or limit the damage that has been associated with the defective mitochondrial function seen in neurodegenerative diseases.

Pioglitazone leads to an inactivation and disassembly of complex I of the mitochondrial respiratory chain

BACKGROUND

Thiazolidinediones are antidiabetic agents that increase insulin sensitivity but reduce glucose oxidation, state 3 respiration, and activity of complex I of the mitochondrial respiratory chain (MRC). The mechanisms of the latter effects are unclear. The aim of this study was to determine the mechanisms by which pioglitazone (PGZ), a member of the thiazolidinedione class of antidiabetic agents, decreases the activity of the MRC. In isolated mitochondria from mouse liver, we measured the effects of PGZ treatment on MRC complex activities, fully-assembled complex I and its subunits, gene expression of complex I and III subunits, and [3H]PGZ binding to mitochondrial complexes.

RESULTS

In vitro, PGZ decreased activity of complexes I and III of the MRC, but in vivo only complex I activity was decreased in mice treated for 12 weeks with 10 mg/kg/day of PGZ. In vitro treatment of isolated liver mitochondria with PGZ disassembled complex I, resulting in the formation of several subcomplexes. In mice treated with PGZ, fully assembled complex I was increased and two additional subcomplexes were found. Formation of supercomplexes CI+CIII2+CIVn and CI+CIII2 decreased in mouse liver mitochondria exposed to PGZ, while formation of these supercomplexes was increased in mice treated with PGZ. Two-dimensional analysis of complex I using blue native/sodium dodecyl sulfate polyacrylamide gel electrophoresis (BN/SDS-PAGE) showed that in vitro PGZ induced the formation of four subcomplexes of 600 (B), 400 (C), 350 (D), and 250 (E) kDa, respectively. Subcomplexes B and C had NADH:dehydrogenase activity, while subcomplexes C and D contained subunits of complex I membrane arm. Autoradiography and coimmunoprecipitation assays showed [3H]PGZ binding to subunits NDUFA9, NDUFB6, and NDUFA6. Treatment with PGZ increased mitochondrial gene transcription in mice liver and HepG2 cells. In these cells, PGZ decreased intracellular ATP content and enhanced gene expression of specific protein 1 and peroxisome-proliferator activated receptor (PPAR)γ coactivator 1α (PGC-1α).

CONCLUSIONS

PGZ binds complex I subunits, which induces disassembly of this complex, reduces its activity, depletes cellular ATP, and, in mice and HepG2 cells, upregulates nuclear DNA-encoded gene expression of complex I and III subunits.

Many faces of mitochondrial uncoupling during age: damage or defense?

An increased mitochondrial proton leak occurs in aging, but the origin of such modification remains unclear. This study defined the cause of mitochondrial uncoupling in mitotic (liver) and postmitotic (heart) rat tissues during aging and its effects on energy homeostasis and free radical production. Proton leak in old heart mitochondria was dependent on uncoupling proteins' upregulation, whereas it was caused by alterations in the mitochondrial membrane composition in old liver. ATP homeostasis was impaired in both tissues from old animals and was associated to disrupted F0F1-ATPase activity. H2O2 production rate and 4-hydroxy-2-nonenalprotein adducts were higher in old liver mitochondria compared with young liver mitochondria, but they were similar in heart mitochondria from both groups. Moreover, key mitochondrial biogenesis regulators were upregulated in old liver but downregulated in old heart. In conclusion, uncoupling proteins mediate proton leak and avoid oxidative damage in heart, acting as a protective mechanism. This does not occur in liver, where ATP depletion and oxidative stress may stimulate mitochondrial biogenesis and eliminate damaged cells.

Enhancement of mitochondrial biogenesis with polyphenols: combined effects of resveratrol and equol in human endothelial cells

Emerging evidence suggests that combinatorial action of numerous biologically active compounds may be a valuable source in a variety of therapeutic applications. Several nutraceuticals have demonstrated to augment the efficacy of pharmacological approaches or provide physiological benefit to improve age-related decline. Recently, the possibilities of anti-ageing interventions have multiplied also to ameliorate the mitochondrial alterations in ageing-associated diseases. In this report, we approached a novel treatment strategy by combining two bioactive dietary constituents (resveratrol and equol) to determine their effect on mitochondrial function. Taking into account that the biological activities of resveratrol and equol has been observed in a wide range of biological processes, they were selected to examine whether combining them would be more effective to modulate mitochondrial function. In HUVEC cells our results demonstrate that the co-administration of these natural products increased mitochondrial mass and mitochondrial DNA content. Additionally, combined use of both compounds increased SIRT1 enzymatic activity and induced mitochondrial biogenesis factors such as PGC1-α, TFAM and NRF-1. Therefore, identification of this novel synergism may provide a new perspective for future treatments aiming to modulate the mitochondrial activity with implications in maintaining endothelial function which is crucial in the regulation of immune response. Further studies to discover the molecular details of this crosstalk and to identify new combinations of active compounds affecting the mitochondrial function will be extremely beneficial to prevent mitochondrial decline.

Nutritional status modulates plasma leptin, AMPK and TOR activation, and mitochondrial biogenesis: Implications for cell metabolism and growth in skeletal muscle of the fine flounder

Insight of how growth and metabolism in skeletal muscle are related is still lacking in early vertebrates. In this context, molecules involved in these processes, such as leptin, AMP-activated protein kinase (AMPK), target of rapamicyn (TOR), peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α, and oxidative phosphorylation complexes (OXPHOS), were assessed in the skeletal muscle of a fish species. Periods of fasting followed by a period of refeeding were implemented, using the fine flounder as a model (Paralichthys adspersus). This species exhibits remarkably slow growth and food intake, which is linked to an inherent growth hormone (GH) resistance and high circulating levels of leptin. Leptin increased during fasting concomitantly with AMPK activation, which was inversely correlated with TOR activation. On the other hand, AMPK was directly correlated with an increase in PGC-1α and OXPHOS complexes contents. Dramatic changes in the activation and content of these molecules were observed during short-term refeeding. Leptin, AMPK activation, and PGC-1α/OXPHOS complexes contents decreased radically; whereas, TOR activation increased significantly. During long-term refeeding these molecules returned to basal levels. These results suggest that there is a relation among these components; thus, during fasting periods ATP-consuming biosynthetic pathways are repressed and alternative sources of ATP/energy are promoted, a phenomenon that is reversed during anabolic periods. These results provide novel insight on the control of metabolism and growth in the skeletal muscle of a non-mammalian species, suggesting that both processes in fish muscle are closely related and coordinated by a subset of common molecules.

The mitochondrial nucleoid: integrating mitochondrial DNA into cellular homeostasis

The packaging of mitochondrial DNA (mtDNA) into DNA-protein assemblies called nucleoids provides an efficient segregating unit of mtDNA, coordinating mtDNA's involvement in cellular metabolism. From the early discovery of mtDNA as "extranuclear" genetic material, its organization into nucleoids and integration into both the mitochondrial organellar network and the cell at large via a variety of signal transduction pathways, mtDNA is a crucial component of the cell's homeostatic network. The mitochondrial nucleoid is composed of a set of DNA-binding core proteins involved in mtDNA maintenance and transcription, and a range of peripheral factors, which are components of signaling pathways controlling mitochondrial biogenesis, metabolism, apoptosis, and retrograde mitochondria-to-nucleus signaling. The molecular interactions of nucleoid components with the organellar network and cellular signaling pathways provide exciting clues to the dynamic integration of mtDNA into cellular metabolic homeostasis.

Molecular events underlying Parkinson's disease - an interwoven tapestry

Although a subject of intense research, the mechanisms underlying dopaminergic neurodegeneration in Parkinson’s disease (PD) remains poorly understood. However, a broad range of studies conducted over the past few decades, including epidemiological, genetic, and post-mortem analysis, as well as in vitro and in vivo modeling, have contributed significantly to our understanding of the pathogenesis of the disease. In particular, the recent identification and functional characterization of several genes, including α-synuclein, parkin, DJ-1, PINK1, and LRRK2, whose mutations are causative of rare familial forms of PD have provided tremendous insights into the molecular pathways underlying dopaminergic neurodegeneration. Collectively, these studies implicate aberrant mitochondrial and protein homeostasis as key contributors to the development of PD, with oxidative stress likely acting as an important nexus between the two pathogenic events. Aberrations in homeostatic processes leading to protein aggregation and mitochondrial dysfunction may arise intrinsically in substantia nigra pars compacta dopaminergic neurons as a result of impairments in the ubiquitin-proteasome system, failure in autophagy-mediated clearance, alterations of mitochondrial dynamics, redox imbalance, iron mishandling, dopamine dysregulation, or simply from the chronic pace-making activity of nigra-localized L-type calcium channels, or extrinsically from non-autonomous sources of stress. Given the myriad of culprits implicated, the pathogenesis of PD necessarily involves an intricate network of interwoven pathways rather than a linear sequence of events. Obviously, understanding how the various disease-associated pathways interact with and influence each other is of mechanistic and therapeutic importance. Here, we shall discuss some key PD-related pathways and how they are interwoven together into a tapestry of events.

Bigenomic transcriptional regulation of all thirteen cytochrome c oxidase subunit genes by specificity protein 1

Cytochrome c oxidase (COX) is one of only four known bigenomic proteins, with three mitochondria-encoded subunits and 10 nucleus-encoded ones derived from nine different chromosomes. The mechanism of regulating this multi-subunit, bigenomic enzyme is not fully understood. We hypothesize that specificity protein 1 (Sp1) functionally regulates the 10 nucleus-encoded COX subunit genes directly and the three mitochondrial COX subunit genes indirectly by regulating mitochondrial transcription factors A and B (TFAM, TFB1M and TFB2M) in neurons. By means of in silico analysis, electrophoretic mobility shift and supershift assays, chromatin immunoprecipitation, RNA interference and over-expression experiments, the present study documents that Sp1 is a critical regulator of all 13 COX subunit genes in neurons. This regulation is intimately associated with neuronal activity. Silencing of Sp1 prevented the upregulation of all COX subunits by KCl, and over-expressing Sp1 rescued all COX subunits from being downregulated by tetrodotoxin. Thus, Sp1 and our previously described nuclear respiratory factors 1 and 2 are the three key regulators of all 13 COX subunit genes in neurons. The binding sites for Sp1 on all 10 nucleus-encoded COX subunits, TFAM, TFB1M and TFB2M are highly conserved among mice, rats and humans.