Regulation Of Oxidative Metabolism Research Articles

Possible link between familial susceptibility to cancer and the level of oxidative stress in thyroid cancer patients

BackgroundHereditary cancer is estimated to account for up to 10% of the worldwide cancer burden; 5% of all thyroid cancers are thought to be genetic. Inheritance of a deleterious mutation in genes associated with a high lifetime risk of developing cancer. Cancer-predisposing genes can promote the initiation and progression of thyroid cancer by enhancing the activation of major signaling pathways through oxidative stress mechanisms.AimIdentification of the possible link between familial susceptibility to cancer and the level of oxidative stress in thyroid cancer patients.MethodsPatients with thyroid cancer (with and without genetic predisposition) were investigated. Study participants were treated in Limited Liability Company (LLC) “Oncology Scientific Research Center” (Tbilisi, Georgia). The study group was collected between 2020 and 2021. In patients’ blood, the thyroid hormones content (free Triiodothyronine (fFT3), free Thyroxine (fFT4), bound Triiodothyronine (FT3), bound Thyroxine (FT4), Thyroid-stimulating hormone (TSH)), and oxidative stress intensity (total activity of non-enzymatic antioxidant system (TAA) and the lipid peroxidation product, malondialdehyde (MDA), content) were investigated.ResultsThe difference in free and bound forms of T3 and T4 levels in the blood serum between patients with thyroid cancer (Group 2 and Group 3) and the control group (Group 1) was not statistically significant (F1,2=0.5, p1,2=0.8, F1,3=2.31, p1,3=0.16). In patients with thyroid cancer the TSH level significantly increased compared to the control group (Group 1) (TSH (mean ± Std error): Group 1– 1.21 ± 0.12, Group 2–2.45 ± 0.11 (F1,2=107, p1,2<0.001), Group 3–2.47 ± 0.17 (F1,3=150, p1,3<0.001)) and the MDA levels increased by 4–5 fold. In patients with thyroid cancer from families with cancer aggregation(Group 2), the level of TAA statistically significantly decreased (F1 − 2=200; p1 − 2<0.001), in patients without genetic predisposition to cancer(Group 3), the level of TAA did not change compared to the control (F1 − 3= 2.13; p1 − 3=0.15),ConclusionsOxidative stress plays a critical role in tumorigenesis, and antioxidant/oxidant imbalance may contribute to the malignant transformation of normal tissue. In patients with familial susceptibility to cancer mutations of several genes, which are involved in the regulation of oxidative metabolism, may contribute to the disruption of the redox balance, increase the level of oxidative stress, and contribute to the development of thyroid cancer.

Search for biocontrol agents among endophytic lipopeptide-synthesizing bacteria Bacillus spp. to protect wheat plants against Greenbug aphid (Schizaphis graminum).

Beneficial endophytic bacteria can suppress the development of insect pests through direct antagonism, with the help of metabolites, or indirectly by the induction of systemic resistance through the regulation of hormonal signaling pathways. Lipopeptides are bacterial metabolites that exhibit direct antagonistic activity against many organisms, including insects. Also, lipopeptides are able to trigger induced systemic resistance (ISR) in plants against harmful organisms, but the physiological mechanisms of their action are just beginning to be studied. In this work, we studied ten strains of bacteria isolated from the tissues of wheat and potatoes. Sequencing of the 16S rRNA gene showed that all isolates belong to the genus Bacillus and to two species, B. subtilis and B. velezensis. The genes for lipopeptide synthetase - surfactin synthetase (Bs_srf ), iturin synthetase (Bs_ituA, Bs_ituB) and fengycin synthetase (Bs_fenD) - were identified in all bacterial isolates using PCR. All strains had high aphicidal activity against the Greenbug aphid (Schizaphis graminum Rond.) due to the synthesis of lipopeptides, which was proven using lipopeptide-rich fractions (LRFs) isolated from the strains. Endophytic lipopeptide-synthesizing strains of Bacillus spp. indirectly affected the viability of aphids, the endurance of plants against aphids and triggered ISR in plants, which manifested itself in the regulation of oxidative metabolism and the accumulation of transcripts of the Pr1, Pr2, Pr3, Pr6 and Pr9 genes due to the synthesis of lipopeptides, which was proven using LRF isolated from three strains: B. subtilis 26D, B. subtilis 11VM, and B. thuringiensis B-6066. We have for the first time demonstrated the aphicidal effect of fengycin and the ability of the fengycin-synthesizing strains and isolates, B. subtilis Ttl2, Bacillus sp. Stl7 and B. thuringiensis B-6066, to regulate components of the pro-/antioxidant system of aphid-infested plants. In addition, this work is the first to demonstrate an elicitor role of fengycin in triggering a systemic resistance to S. graminum in wheat plants. We have discovered new promising strains and isolates of endophytes of the genus Bacillus, which may be included in the composition of new biocontrol agents against aphids. One of the criteria for searching for new bacteria active against phloem-feeding insects can be the presence of lipopeptide synthetase genes in the bacterial genome.

Autophagy gene expression in skeletal muscle of older individuals is associated with physical performance, muscle volume and mitochondrial function in the study of muscle, mobility and aging (SOMMA).

Autophagy is essential for proteostasis, energetic balance, and cell defense and is a key pathway in aging. Identifying associations between autophagy gene expression patterns in skeletal muscle and physical performance outcomes would further our knowledge of mechanisms related with proteostasis and healthy aging. Muscle biopsies were obtained from participants in the Study of Muscle, Mobility, and Aging (SOMMA). For 575 participants, RNA was sequenced and expression of 281 genes related to autophagy regulation, mitophagy, and mTOR/upstream pathways was determined. Associations between gene expression and outcomes including mitochondrial respiration in muscle fiber bundles (MAX OXPHOS), physical performance (VO2 peak, 400 m walking speed, and leg power), and thigh muscle volume, were determined using negative binomial regression models. For autophagy, key transcriptional regulators including TFE3 and NFKB-related genes (RELA, RELB, and NFKB1) were negatively associated with outcomes. On the contrary, regulators of oxidative metabolism that also promote overall autophagy, mitophagy, and pexophagy (PPARGC1A, PPARA, and EPAS1) were positively associated with multiple outcomes. In line with this, several mitophagy, fusion, and fission-related genes (NIPSNAP2, DNM1L, and OPA1) were also positively associated with outcomes. For mTOR pathway and related genes, expression of WDR59 and WDR24, both subunits of GATOR2 complex (an indirect inhibitor of mTORC1), and PRKAG3, which is a regulatory subunit of AMPK, were negatively correlated with multiple outcomes. Our study identifies autophagy and selective autophagy such as mitophagy gene expression patterns in human skeletal muscle related to physical performance, muscle volume, and mitochondrial function in older persons which may lead to target identification to preserve mobility and independence.

The Mitochondrial Calcium Uniporter (MCU): Molecular Identity and Role in Human Diseases.

Calcium (Ca2+) ions act as a second messenger, regulating several cell functions. Mitochondria are critical organelles for the regulation of intracellular Ca2+. Mitochondrial calcium (mtCa2+) uptake is ensured by the presence in the inner mitochondrial membrane (IMM) of the mitochondrial calcium uniporter (MCU) complex, a macromolecular structure composed of pore-forming and regulatory subunits. MtCa2+ uptake plays a crucial role in the regulation of oxidative metabolism and cell death. A lot of evidence demonstrates that the dysregulation of mtCa2+ homeostasis can have serious pathological outcomes. In this review, we briefly discuss the molecular structure and the function of the MCU complex and then we focus our attention on human diseases in which a dysfunction in mtCa2+ has been shown.

Cyclin D3 deficiency promotes a slower, more oxidative skeletal muscle phenotype and ameliorates pathophysiology in the mdx mouse model of Duchenne muscular dystrophy.

We previously reported that cyclin D3-null mice display a shift toward the slow, oxidative phenotype in skeletal muscle, improved exercise endurance, and increased energy expenditure. Here, we explored the role of cyclin D3 in the physiologic response of skeletal muscle to external stimuli and in a model of muscle degenerative disease. We show that cyclin D3-null mice exhibit a further transition from glycolytic to oxidative muscle fiber type in response to voluntary exercise and an improved response to fasting. Since fast glycolytic fibers are known to be more susceptible to degeneration in Duchenne muscular dystrophy (DMD), we examined the effects of cyclin D3 inactivation on skeletal muscle phenotype in the mdx mouse model of DMD. Compared with control mdx mice, cyclin D3-deficient mdx mice display a higher proportion of slower and more oxidative myofibers, reduced muscle degenerative/regenerative processes, and reduced myofiber size variability, indicating an attenuation of dystrophic histopathology. Furthermore, mdx muscles lacking cyclin D3 exhibit reduced fatigability during repeated electrical stimulations. Notably, cyclin D3-null mdx mice show enhanced performance during recurrent trials of endurance treadmill exercise, and post-exercise muscle damage results decreased while the regenerative capacity is boosted. In addition, muscles from exercised cyclin D3-deficient mdx mice display increased oxidative capacity and increased mRNA expression of genes involved in the regulation of oxidative metabolism and the response to oxidative stress. Altogether, our findings indicate that depletion of cyclin D3 confers benefits to dystrophic muscle, suggesting that cyclin D3 inhibition may represent a promising therapeutic strategy against DMD.

Cardiac Na/K-ATPase alpha1 isoform-specific role in hypertrophic response: role of metabolic and oxidative signaling

Cardiac Na/K-ATPase (NKA) inhibition by cardiotonic steroids (CTS) modulates intracellular Na + and Ca 2+ , leading to increased force of contraction. In contrast, hypertrophy of cardiomyocytes (CM) is triggered by CTS through stimulation of reactive oxygen species (ROS) and fetal gene re-expression independently of changes in intracellular Na + or Ca 2+ . Based on recent evidence that NKAα1 serves an isoform-specific function in the regulation of oxidative metabolism and ROS generation, we used a genetic approach in the mouse and in human cardiac cells (AC16) to test the hypothesis that NKAα1 is required for cardiac hypertrophy. Cardio α1 -/- mice, a conditional KO of NKAα1 in the heart, were viable without overt abnormality of cardiac structure or function. NKAα1 was undetectable in heart lysates or isolated CM of adult cardio α1 -/- mice. Despite a compensatory upregulation of NKAα2, Na/K-ATPase activity in crude heart homogenates and NKA currents in CM were reduced by about 60%. Decreased ROS (assessed by total protein carbonylation) and reduced fatty acid oxidation (FAO) and oxidative phosphorylation pathways (revealed by RNA-seq analysis) were noted at baseline. RT-qPCR revealed downregulated genes involved with FAO and the electron transport chain (such as, Acadl and Ndufa9, about 20% decrease, n=6) in cardio α1 -/- hearts. The activity of the electron transport chain complex I was decreased in cardio α1 -/- hearts (0.3354 vs 0.2732 mOD/min/mg of protein, p&lt;0.05). When 3-month-old male mice were challenged with angiotensin II (1.5 mg.kg -1 .day -1 for 1 week, n=6-15), cardio α1 -/- mice did not develop cardiac hypertrophy, as assessed by heart weight to tibia length ratio, but displayed exacerbated cardiac fibrosis, revealed by Trichrome staining, consistent with the postulated role of CM NKAα1 isoform-specific function in cardiac hypertrophy in vivo. In vitro, CRISPR-Cas9-mediated KO of NKAα1 in AC16 cells led to a drastic downregulation of NKAα1 compared to WT AC16 cells. In contrast to WT AC16 cells, NKAα1 KO cells did not respond to the α-adrenergic agonist phenylephrine (50 μM for 24h) with the expected increase in cell area (2243 vs 3520 μm 2 for WT, p&lt;0.05; 2454 vs 2563 μm 2 for KO, p&gt;0.05). These data suggest that NKAα1 isoform-specific function is required for cardiac hypertrophy. Mechanistically, our data support an isoform-specific regulatory function of NKAα1 in normal FAO, electron transport chain activity, and ROS generation, which are critical for CM hypertrophy. Supported by NIH Grant R15 HL145666 and American Heart Association Grant 22POST917776 (Marco T. Pessoa) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

RHODIOLA ROSEA AND FERULIC ACID ACTIVATE EXPRESSION OF GENES RELATED TO AUTOPHAGY AND RESISTANCE TO HEAT SHOCK IN MICE OF DIFFERENT AGE

The aim of our study was testing whether R. rosea extract and ferulic acid activate expression of targets of FoxO, regulators of energy metabolism and autophagy in livers of young and old mice, and to what extent the effects of R. rosea extract and ferulic acid on the genes studied coincide. Methods. . C57BL/6J mice were reared at 22 ± 2 °С, 50-60% humidity, and 12/12 hour light/dark cycle. All groups were reared on a standard chow (4,8% fats, 21,8% protein, and 3,9% fibre). Experimental groups consumed water, supplemented with either sodium ferulate or R. rosea during 12 weeks prior sacrificing. The amounts of ferulate and R. rosea were adjusted to provide 4 mg of phenol-containing substances per 100 g weight, for a mouse, for 24 hours. We tested three-month-old (“young”) and twelve-month-old males (“old”). The levels of messenger ribonucleic acid (mRNA) were assessed using AriaMx real-time polymerase chain reaction (RT-PCR) instrument (Agilent). Ribonucleic acid was purified using the Monarch Miniprep kit (New England BioLabs (NEB), T2010), complementary deoxyribonucleic acid synthesis was performed using the ProtoScript II kit (NEB, E6560), and quantitative RT-PCR (qRT-PCR) was performed using the Luna Universal kit (NEB, E3003). The expression of genes ATG5 (an autophagy marker), HSPB8 (a small heat shock protein, an FoxO target), UCP2 (uncoupling protein 2, a senescence marker), CDKN2 (cell cycle regulator, a senescence marker), PDK2 and PDK4 (pyruvate dehydrogenase kinases 2 and 4, regulators of oxidative metabolism), and TFEB (transcription factor EB, a transcriptional regulator of autophagy) was evaluated. Results. Livers of young mice that consumed food supplemented with either sodium ferulate or R. rosea extract had 3.2-fold and 3.6-fold higher levels of mRNA of the small heat shock protein HspB8 than control mice, respectively. In old mice, the levels of mRNA for this protein were 3.3-fold higher in mice reared on the diet containing R. rosea extract as compared with the control. However, there was no significant difference between control mice and those that consumed ferulate-supplemented food. In young mice, ferulate and R. rosea extract induced synthesis of mRNA of PDK4 by 4.3 and 6.6 times from the control level, respectively. Ferulate and R. rosea extract also affected the levels of mRNA of ATG5 and PDK2 in the livers of old mice. The levels of PDK2 were 1.5-fold higher in the livers of mice that consumed ferulate-supplemented food than in control mice. Conclusions. Both, R. rosea extract and one of its active components – ferulic acid – promote increasing in the levels of mRNA for genes HSPB8 and PDK4, coding for small heat shock protein and pyruvate dehydrogenase kinase 4, respectively. In old mice, R. rosea promote expression of HSPB8, ATG5, PDK2, and PDK4. Thus, ferulic acid and R. rosea exert similar effects on gene expression by supposed activation of heat shock response and autophagy, and concomitant inhibition of mitochondrial metabolism via boosting expression of PDK2 and PDK4.

The relationship between cytochrome c oxidase, CBF and CMRO2 in mouse cortex: A NIRS-MRI study

Quantifying relationships between cerebral blood flow (CBF), mitochondrial function (cytochrome c oxidase oxidation state), and metabolic rate of oxygen (CMRO2) could provide useful insight into normal neurovascular coupling, as well as regulation of oxidative metabolism in neurological disorders. This paper uses a multimodal NIRS-MRI method to quantify these parameters in rodent brain and, in so doing, provides novel information on the regulation of oxygen metabolism by stimulating with hypercapnia or variations in oxygenation. Under hypercapnia, although oxygenation, oxidation state, and CBF increased, there was no increase in CMRO2. Also, there was no correlation between CBF and CCO oxidation state. Conversely, changing oxygenation resulted in a strong correlation between the oxidation of CCO and CBF. This proves that the association between CBF and the redox state of CCO is not fixed and depends on the type of perturbation. Having a means to measure CBF and CCO oxidation state simultaneously will help understanding their contribution to intact neurovascular coupling and detecting abnormal cellular oxygen metabolism in many neurological disorders.

Loss of skeletal muscle estrogen-related receptors leads to severe exercise intolerance

ObjectiveSkeletal muscle oxidative capacity is central to physical activity, exercise capacity and whole-body metabolism. The three estrogen-related receptors (ERRs) are regulators of oxidative metabolism in many cell types, yet their roles in skeletal muscle remain unclear. The main aim of this study was to compare the relative contributions of ERRs to oxidative capacity in glycolytic and oxidative muscle, and to determine defects associated with loss of skeletal muscle ERR function. MethodsWe assessed ERR expression, generated mice lacking one or two ERRs specifically in skeletal muscle and compared the effects of ERR loss on the transcriptomes of EDL (predominantly glycolytic) and soleus (oxidative) muscles. We also determined the consequences of the loss of ERRs for exercise capacity and energy metabolism in mice with the most severe loss of ERR activity. ResultsERRs were induced in human skeletal muscle in response to an exercise bout. Mice lacking both ERRα and ERRγ (ERRα/γ dmKO) had the broadest and most dramatic disruption in skeletal muscle gene expression. The most affected pathway was “mitochondrial function”, in particular Oxphos and TCA cycle genes, and transcriptional defects were more pronounced in the glycolytic EDL than the oxidative soleus. Mice lacking ERRβ and ERRγ, the two isoforms expressed highly in oxidative muscles, also exhibited defects in lipid and branch chain amino acid metabolism genes, specifically in the soleus. The pronounced disruption of oxidative metabolism in ERRα/γ dmKO mice led to pale muscles, decreased oxidative capacity, histochemical patterns reminiscent of minicore myopathies, and severe exercise intolerance, with the dmKO mice unable to switch to lipid utilization upon running. ERRα/γ dmKO mice showed no defects in whole-body glucose and energy homeostasis. ConclusionsOur findings define gene expression programs in skeletal muscle that depend on different combinations of ERRs, and establish a central role for ERRs in skeletal muscle oxidative metabolism and exercise capacity. Our data reveal a high degree of functional redundancy among muscle ERR isoforms for the protection of oxidative capacity, and show that ERR isoform-specific phenotypes are driven in part, but not exclusively, by their relative levels in different muscles.

Inhibition of mitoNEET induces Pink1-Parkin-mediated mitophagy

MitoNEET, a mitochondrial outer membrane protein containing the Asn-Glu-Glu-Thr (NEET) sequence, controls the formation of intermitochondrial junctions and confers autophagy resistance. Moreover, mitoNEET as a mitochondrial substrate undergoes ubiquitination by activated Parkin during the initiation of mitophagy. Therefore, mitoNEET is linked to the regulation of autophagy and mitophagy. Mitophagy is the selective removal of the damaged or unnecessary mitochondria, which is crucial to sustaining mitochondrial quality control. In numerous human diseases, the accumulation of damaged mitochondria by impaired mitophagy has been observed. However, the therapeutic strategy targeting of mitoNEET as a mitophagy-enhancing mediator requires further research. Herein, we confirmed that mitophagy is indeed activated by mitoNEET inhibition. CCCP (carbonyl cyanide m-chlorophenyl hydrazone), which leads to mitochondrial depolarization, induces mitochondrial dysfunction and superoxide production. This, in turn, contributes to the induction of mitophagy; mitoNEET protein levels were initially increased before an increase in LC3-Ⅱ protein following CCCP treatment. Pharmacological inhibition of mitoNEET using mitoNEET Ligand-1 (NL-1) promoted accumulation of Pink1 and Parkin, which are mitophagy-associated proteins, and activation of mitochondria–lysosome crosstalk, in comparison to CCCP alone. Inhibition of mitoNEET using NL-1, or mitoNEET shRNA transfected into RAW264.7 cells, abrogated CCCP-induced ROS and mitochondrial cell death; additionally, it activated the expression of PGC-1α and SOD2, regulators of oxidative metabolism. In particular, the increase in PGC-1α, which is a major regulator of mitochondrial biogenesis, promotes mitochondrial quality control. These results indicated that mitoNEET is a potential therapeutic target in numerous human diseases to enhance mitophagy and protect cells by maintaining a network of healthy mitochondria.

The discovery of a novel series of potential ERRα inverse agonists based on p-nitrobenzenesulfonamide template for triple-negative breast cancer in vivo

Oestrogen related receptor α participated in the regulation of oxidative metabolism and mitochondrial biogenesis, and was overexpressed in many cancers including triple-negative breast cancer. A set of new ERRα inverse agonists based on p-nitrobenzenesulfonamide template were discovered and compound 11 with high potent activity (IC50 = 0.80 μM) could significantly inhibit the transcription of ERRα-regulated target genes. By regulating the downstream signalling pathway, compound 11 could suppress the migration and invasion of the ER-negative MDA-MB-231 cell line. Furthermore, compound 11 demonstrated a significant growth suppression of breast cancer xenograft tumours in vivo (inhibition rate 23.58%). The docking results showed that compound 11 could form hydrogen bonds with Glu331 and Arg372 in addition to its hydrophobic interaction with ligand-binding domain. Our data implied that compound 11 represented a novel and effective ERRα inverse agonist, which had broad application prospects in the treatment of triple-negative breast cancer.

Distinct skeletal muscle molecular responses to pulmonary rehabilitation in chronic obstructive pulmonary disease: a cluster analysis

BackgroundPulmonary rehabilitation (PR) is a cornerstone in the management of chronic obstructive pulmonary disease (COPD), targeting skeletal muscle to improve functional performance. However, there is substantial inter‐individual variability in the effect of PR on functional performance, which cannot be fully accounted for by generic phenotypic factors. We performed an unbiased integrative analysis of the skeletal muscle molecular responses to PR in COPD patients and comprehensively characterized their baseline pulmonary and physical function, body composition, blood profile, comorbidities, and medication use.Methods Musculus vastus lateralis biopsies were obtained from 51 COPD patients (age 64 ± 1 years, sex 73% men, FEV1, 34 (26–41) %pred.) before and after 4 weeks high‐intensity supervised in‐patient PR. Muscle molecular markers were grouped by network‐constrained clustering, and their relative changes in expression values—assessed by qPCR and western blot—were reduced to process scores by principal component analysis. Patients were subsequently clustered based on these process scores. Pre‐PR and post‐PR functional performance was assessed by incremental cycle ergometry and 6 min walking test (6MWT).ResultsEight molecular processes were discerned by network‐constrained hierarchical clustering of the skeletal muscle molecular rehabilitation responses. Based on the resulting process scores, four clusters of patients were identified by hierarchical cluster analysis. Two major patient clusters differed in PR‐induced autophagy (P < 0.001), myogenesis (P = 0.014), glucocorticoid signalling (P < 0.001), and oxidative metabolism regulation (P < 0.001), with Cluster 1 (C1; n = 29) overall displaying a more pronounced change in marker expression than Cluster 2 (C2; n = 16). General baseline characteristics did not differ between clusters. Following PR, both 6 min walking distance (+26.5 ± 8.3 m, P = 0.003) and peak load on the cycle ergometer test (+9.7 ± 1.9 W, P < 0.001) were improved. However, the functional improvement was more pronounced in C1, as a higher percentage of patients exceeded the minimal clinically important difference in peak workload (61 vs. 21%, P = 0.022) and both peak workload and 6 min walking test (52 vs. 8%, P = 0.008) upon PR.ConclusionsWe identified patient groups with distinct skeletal muscle molecular responses to rehabilitation, associated with differences in functional improvements upon PR.

223 - The regulation of oxidative metabolism by nitric oxide protects β-cells from DNA damage-induced cell death

Nitric oxide, generated in β-cells in response to cytokines, induces DNA damage that activates DNA damage response (DDR) and eventually leads to apoptosis if damage is too extensive. We have shown that nitric oxide, while inducing double-strand DNA breaks (DSBs), also inhibits DDR signaling and protects β-cells from DNA damage-induced apoptosis.The ability of nitric oxide to inhibit the DDR signaling is selective to β-cells and correlates with a loss in ATP levels, while non-β-cells are able to maintain both ATP levels and DDR signaling when treated with nitric oxide. However, the mechanism that regulates this cell type selectiveness is not known. β-cell metabolism is characterized by the coupling of glycolysis to mitochondrial oxidative metabolism, where 90% of the carbons of glucose are oxidized to CO2 in a concentration-dependent manner. Nitric oxide is known to inhibit mitochondrial oxidative metabolism (e.g. aconitase in the TCA cycle and complex IV of electron transport chain (ETC)). In response to nitric oxide, β-cells are not able to compensate the inhibition of mitochondrial oxidation by increasing glycolytic metabolism. In contrast, non-β-cells compensate for the mitochondrial inhibition by increasing glycolytic metabolism to maintain their ATP pool. Consistent with the action of nitric oxide, we showed that rotenone, an inhibitor of complex I of ETC, also inhibit DDR signaling and decrease ATP levels in β-cells but not in non-β-cells. Importantly, when non-β-cells are forced to generate ATP via mitochondrial oxidation, nitric oxide inhibits DDR signaling, decrease ATP levels, and protects cells from DNA damage-induced apoptosis. These findings suggest that the coupling of glycolysis to mitochondrial oxidative metabolism in β-cells allows nitric oxide to decrease ATP levels and subsequently inhibit DDR signaling and protect β-cells from DNA damage-induced apoptosis.

The FLCN-TFE3 axis regulates macrophage activation through cellular metabolism

Cellular metabolism has been suggested to play a deterministic role in many biological processes including the regulation of stem cell properties and functions. A tumor suppressor gene, folliculin (FLCN) is responsible for Birt-Hogg-Dubé (BHD) syndrome characterized by benign skin tumors, lung and kidney cysts, and kidney cancer, and has been suggested to be involved in regulation of oxidative metabolism. We previously reported that conditional depletion of Flcn in hematopoietic stem cell compartment using the Mx1-Cre system led to macrophage activation and bone marrow failure (Baba et al, 2016).

Pro- and Antioxidant Functions of the Peroxisome-Mitochondria Connection and Its Impact on Aging and Disease.

Peroxisomes and mitochondria are the main intracellular sources for reactive oxygen species. At the same time, both organelles are critical for the maintenance of a healthy redox balance in the cell. Consequently, failure in the function of both organelles is causally linked to oxidative stress and accelerated aging. However, it has become clear that peroxisomes and mitochondria are much more intimately connected both physiologically and structurally. Both organelles share common fission components to dynamically respond to environmental cues, and the autophagic turnover of both peroxisomes and mitochondria is decisive for cellular homeostasis. Moreover, peroxisomes can physically associate with mitochondria via specific protein complexes. Therefore, the structural and functional connection of both organelles is a critical and dynamic feature in the regulation of oxidative metabolism, whose dynamic nature will be revealed in the future. In this review, we will focus on fundamental aspects of the peroxisome-mitochondria interplay derived from simple models such as yeast and move onto discussing the impact of an impaired peroxisomal and mitochondrial homeostasis on ROS production, aging, and disease in humans.

Reduced ATGL-mediated lipolysis attenuates β-adrenergic-induced AMPK signaling, but not the induction of PKA-targeted genes, in adipocytes and adipose tissue.

5'-AMP-activated protein kinase (AMPK) is activated as a consequence of lipolysis and has been shown to play a role in regulation of adipose tissue mitochondrial content. Conversely, the inhibition of lipolysis has been reported to potentiate the induction of protein kinase A (PKA)-targeted genes involved in the regulation of oxidative metabolism. The purpose of the current study was to address these apparent discrepancies and to more fully examine the relationship between lipolysis, AMPK, and the β-adrenergic-mediated regulation of gene expression. In 3T3-L1 adipocytes, the adipose tissue triglyceride lipase (ATGL) inhibitor ATGListatin attenuated the Thr(172) phosphorylation of AMPK by a β3-adrenergic agonist (CL 316,243) independent of changes in PKA signaling. Similarly, CL 316,243-induced increases in the Thr(172) phosphorylation of AMPK were reduced in adipose tissue from whole body ATGL-deficient mice. Despite reductions in the activation of AMPK, the induction of PKA-targeted genes was intact or, in some cases, increased. Similarly, markers of mitochondrial content and respiration were increased in adipose tissue from ATGL knockout mice independent of changes in the Thr(172) phosphorylation of AMPK. Taken together, our data provide evidence that AMPK is not required for the regulation of adipose tissue oxidative capacity in conditions of reduced fatty acid release.

Energizing Genetics and Epi-genetics: Role in the Regulation of Mitochondrial Function.

Energy metabolism and mitochondrial function hold a core position in cellular homeostasis. Oxidative metabolism is regulated at multiple levels, ranging from gene transcription to allosteric modulation. To accomplish the fine tuning of these multiple regulatory circuits, the nuclear and mitochondrial compartments are tightly and reciprocally controlled. The fact that nuclear encoded factors, PPARγ coactivator 1α and mitochondrial transcription factor A, play pivotal roles in the regulation of oxidative metabolism and mitochondrial biogenesis is paradigmatic of this crosstalk. Here we provide an updated survey of the genetic and epigenetic mechanisms involved in the control of energy metabolism and mitochondrial function. Chromatin dynamics highly depends on post-translational modifications occurring at specific amino acids in histone proteins and other factors associated to nuclear DNA. In addition to the well characterized enzymes responsible for histone methylation/demethylation and acetylation/deacetylation, other factors have gone on the “metabolic stage”. This is the case of the new class of α-ketoglutarate-regulated demethylases (Jumonji C domain containing demethylases) and of the NAD+-dependent deacetylases, also known as sirtuins. Moreover, unexpected features of the machineries involved in mitochondrial DNA (mtDNA) replication and transcription, mitochondrial RNA processing and maturation have recently emerged. Mutations or defects of any component of these machineries profoundly affect mitochondrial activity and oxidative metabolism. Finally, recent evidences support the importance of mtDNA packaging in replication and transcription. These observations, along with the discovery that non-classical CpG islands present in mtDNA undergo methylation, indicate that epigenetics also plays a role in the regulation of the mitochondrial genome function.

Symposium 3: Inflammation: a key driving force in disease progression S3-1 - Control of endothelial function and angiogenesis by PGC-1α relies on ROS control of vascular stability

Peroxisome proliferator activated receptor g co-activator 1alpha (PGC-1α) is a regulator of oxidative metabolism and reactive oxygen species (ROS) homeostasis that has been show to play a relevant role in angiogenesis. PGC-1α KO mice show reduced vascular density in the retinas and KO primary vascular endothelial cells (ECs) migrate faster than the wild type, an effect that can be rescued by antioxidants, suggesting that excessive ROS levels might be relevant in PGC-1 α role in angiogenesis. This study aims to investigate the role of ROS homeostasis on the regulation by PGC-1 α of angiogenesis. We found that endothelial cells (ECs) from mice deleted for PGC-1 α display attenuated adhesion to the extracellular matrix, together with slower spreading, reduced formation of cellular junctions, a disorganized cytoskeleton and random motility, and a enhanced tip phenotype. Aditionally, PGC-1 α -deleted ECs exhibit an altered response to vascular endothelial growth factor-A (VEGF-A). In vivo, deletion of PGC-1 α results in addition to reduced retinal vascular density, sparse pericyte coverage. Exposure of PGC-1 α deleted mice to hyperoxia during retinal vascular development exacerbates these vascular abnormalities and mice show extensive retinal hemorrhaging, with highly unstructured areas and very poor perfusion, compared with wild-type mice. Structural analysis demonstrates a reduction of endothelial VE-cadherin, suggesting defective inter-cellular junctions. Interestingly, this hyperoxia-induced phenotype is partially reversed by antioxidant administration, indicating that elevated production of mitochondrial reactive oxygen species (ROS) in the absence of PGC-1 α is functionally important. Finally, in vitro studies show that antioxidant treatment improves VEGF-A signaling, suggesting that toxic effect of ROS may be caused by the alteration of the VEGF-A signaling pathway. In summary, our findings indicate that PGC-1 α control of ROS homeostasis plays an important role in the control of de novo angiogenesis, and is required for vascular stability.

The coactivator PGC-1α regulates skeletal muscle oxidative metabolism independently of the nuclear receptor PPARβ/δ in sedentary mice fed a regular chow diet.

Physical activity improves oxidative capacity and exerts therapeutic beneficial effects, particularly in the context of metabolic diseases. The peroxisome proliferator-activated receptor (PPAR) γ coactivator-1α (PGC-1α) and the nuclear receptor PPARβ/δ have both been independently discovered to play a pivotal role in the regulation of oxidative metabolism in skeletal muscle, though their interdependence remains unclear. Hence, our aim was to determine the functional interaction between these two factors in mouse skeletal muscle in vivo. Adult male control mice, PGC-1α muscle-specific transgenic (mTg) mice, PPARβ/δ muscle-specific knockout (mKO) mice and the combination PPARβ/δ mKO + PGC-1α mTg mice were studied under basal conditions and following PPARβ/δ agonist administration and acute exercise. Whole-body metabolism was assessed by indirect calorimetry and blood analysis, while magnetic resonance was used to measure body composition. Quantitative PCR and western blot were used to determine gene expression and intracellular signalling. The proportion of oxidative muscle fibre was determined by NADH staining. Agonist-induced PPARβ/δ activation was only disrupted by PPARβ/δ knockout. We also found that the disruption of the PGC-1α-PPARβ/δ axis did not affect whole-body metabolism under basal conditions. As expected, PGC-1α mTg mice exhibited higher exercise performance, peak oxygen consumption and lower blood lactate levels following exercise, though PPARβ/δ mKO + PGC-1α mTg mice showed a similar phenotype. Similarly, we found that PPARβ/δ was dispensable for PGC-1α-mediated enhancement of an oxidative phenotype in skeletal muscle. Collectively, these results indicate that PPARβ/δ is not an essential partner of PGC-1α in the control of skeletal muscle energy metabolism.

Circadian Clock NAD + Cycle Drives Mitochondrial Oxidative Metabolism in Mice

Circadian clocks are self-sustained cellular oscillators that synchronize oxidative and reductive cycles in anticipation of the solar cycle. We found that the clock transcription feedback loop produces cycles of nicotinamide adenine dinucleotide (NAD(+)) biosynthesis, adenosine triphosphate production, and mitochondrial respiration through modulation of mitochondrial protein acetylation to synchronize oxidative metabolic pathways with the 24-hour fasting and feeding cycle. Circadian control of the activity of the NAD(+)-dependent deacetylase sirtuin 3 (SIRT3) generated rhythms in the acetylation and activity of oxidative enzymes and respiration in isolated mitochondria, and NAD(+) supplementation restored protein deacetylation and enhanced oxygen consumption in circadian mutant mice. Thus, circadian control of NAD(+) bioavailability modulates mitochondrial oxidative function and organismal metabolism across the daily cycles of fasting and feeding.