Cytokine stimulation of energy expenditure through p38 MAP kinase activation of PPARgamma coactivator-1

β-Adrenergic Receptors and Adipose Tissue Metabolism: Evolution of an Old Story

The role of β-adrenergic receptors (βARs) in adipose tissue to promote lipolysis and the release of fatty acids and nonshivering thermogenesis in brown fat has been studied for so many decades that one would think there is nothing left to discover. With the rediscovery of brown fat in humans and renewed interest in UCP1 and uncoupled mitochondrial respiration, it seems that a review of adipose tissue as an organ, pivotal observations, and the investigators who made them would be instructive to understanding where the field stands now. The discovery of the β₃-adrenergic receptor was important for accurately defining the pharmacology of the adipocyte, while the clinical targeting of this receptor for obesity and metabolic disease has had its highs and lows. Many questions still remain about how βARs regulate adipocyte metabolism and the signaling molecules through which they do it.

Curcumin Targeting NF-κB/Ubiquitin-Proteasome-System Axis Ameliorates Muscle Atrophy in Triple-Negative Breast Cancer Cachexia Mice

Background

Curcumin is a polyphenol plant-derived compound with anti-inflammatory, antioxidant stress, and anticancer properties that make it have the potential to treat cancer cachexia. However, the role of it in breast cancer cachexia remains unclear.

Methods

The 4T1 cells were subcutaneously injected into BALB/c mice to induce breast cancer cachexia. After tumor formation, the animals were divided into groups and given curcumin or saline interventions. The therapeutic effect of curcumin on breast cancer cachexia was characterized by tumor growth, changes in body mass and gastrocnemius mass, muscle function test, histopathology, and serum nutrition indexes. Mitochondrial function in muscle tissue was observed by transmission electron microscopy and ATP detection, muscle inflammatory factors were detected by ELISA, muscle differential metabolites were detected by ¹HNMR metabolomics, and the muscle tissue ubiquitination levels and NF-KB expression were also analyzed by RT-qPCR and Western blot.

Results

Dynamic in vivo bioluminescence imaging find that curcumin inhibited the growth of tumor in triple-negative breast cancer- (TNBC-) bearing mice, slowed down the loss of body weight and gastrocnemius weight, corrected the mitochondrial dysfunction and malnutrition status, and also significantly improved skeletal muscle function. ELISA analysis found that the level of inflammatory factors in muscle tissue was reduced. ¹HNMR metabolomics analysis suggested that curcumin could regulate energy metabolism pathways. RT-qPCR and Western blot analysis found that the expression of myogenic factor myogenin was increased and the expression of myodegradation factor myostatin was decreased in the gastrocnemius; the level of ubiquitination and activation of the NF-κB pathway were also declined.

Conclusions

Curcumin reduces ubiquitination, inflammation in skeletal muscle by regulating the NF-KB/UPS axis and improves muscle malignant metabolic phenotype and mitochondrial dysfunction, to alleviate muscle atrophy and loss of function in mice with breast cancer cachexia.

Transcription Factor Movement and Exercise-Induced Mitochondrial Biogenesis in Human Skeletal Muscle: Current Knowledge and Future Perspectives

In response to exercise, the oxidative capacity of mitochondria within skeletal muscle increases through the coordinated expression of mitochondrial proteins in a process termed mitochondrial biogenesis. Controlling the expression of mitochondrial proteins are transcription factors-a group of proteins that regulate messenger RNA transcription from DNA in the nucleus and mitochondria. To fulfil other functions or to limit gene expression, transcription factors are often localised away from DNA to different subcellular compartments and undergo rapid movement or accumulation only when required. Although many transcription factors involved in exercise-induced mitochondrial biogenesis have been identified, numerous conflicting findings and gaps exist within our knowledge of their subcellular movement. This review aims to summarise and provide a critical analysis of the published literature regarding the exercise-induced movement of transcription factors involved in mitochondria biogenesis in skeletal muscle.

Gynostemma pentaphyllum extract and its active component gypenoside L improve the exercise performance of treadmill-trained mice

BACKGROUND/OBJECTIVES

The effectiveness of natural compounds in improving athletic ability has attracted attention in both sports and research. Gynostemma pentaphyllum (Thunb.) leaves are used to make traditional herbal medicines in Asia. The active components of G. pentaphyllum, dammarane saponins, or gypenosides, possess a range of biological activities. On the other hand, the anti-fatigue effects from G. pentaphyllum extract (GPE) and its effective compound, gypenoside L (GL), remain to be determined.

MATERIALS/METHODS

This study examined the effects of GPE on fatigue and exercise performance in ICR mice. GPE was administered orally to mice for 6 weeks, with or without treadmill training. The biochemical analysis in serum, glycogen content, mRNA, and protein expressions of the liver and muscle were analyzed.

RESULTS

The ExGPE (exercise with 300 mg/kg body weight/day of GPE) mice decreased the fat mass percentage significantly compared to the ExC mice, while the ExGPE showed the greatest lean mass percentage compared to the ExC group. The administration of GPE improved the exercise endurance and capacity in treadmill-trained mice, increased glucose and triglycerides, and decreased the serum creatine kinase and lactate levels after intensive exercise. The muscle glycogen levels were higher in the ExGPE group than the ExC group. GPE increased the level of mitochondrial biogenesis by enhancing the phosphorylation of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) protein and the mRNA expression of nuclear respiratory factor 1, mitochondrial DNA, peroxisome proliferator-activated receptor-δ, superoxide dismutase 2, and by decreasing the lactate dehydrogenase B level in the soleus muscle (SOL). GPE also improved PGC-1α activation in the SOL significantly through AMPK/p38 phosphorylation.

CONCLUSIONS

These results showed that GPE supplementation enhances exercise performance and has anti-fatigue activity. In addition, the underlying molecular mechanism was elucidated. Therefore, GPE is a promising candidate for developing functional foods and enhancing the exercise capacity and anti-fatigue activity.

Optogenetic stimulation of entorhinal cortex reveals the implication of insulin signaling in adult rat's hippocampal neurogenesis

Adult neurogenesis in the hippocampal dentate gyrus plays a critical role in learning and memory. Projections originating from entorhinal cortex, known as the perforant pathway, provide the main input to the dentate gyrus and promote neurogenesis. However, neuromodulators and molecular changes mediating neurogenic effects of this pathway are not yet fully understood. Here, by means of an optogenetic approach, we investigated neurogenesis and synaptic plasticity in the hippocampus of adult rats induced by stimulation of the perforant pathway. The lentiviruses carrying hChR2 (H134R)-mCherry gene under the control of the CaMKII promoter were injected into the medial entorhinal cortex region of adult rats. After 21 days, the entorhinal cortex region was exposed to the blue laser (473 nm) for five consecutive days (30 min/day). The expression of synaptic plasticity and neurogenesis markers in the hippocampus were evaluated using molecular and histological approaches. In parallel, the changes in the gene expression of insulin and its signaling pathway, trophic factors, and components of mitochondrial biogenesis were assessed. Our results showed that optogenetic stimulation of the entorhinal cortex promotes hippocampal neurogenesis and synaptic plasticity concomitant with the increased levels of insulin mRNA and its signaling markers, neurotrophic factors, and activation of mitochondrial biogenesis. These findings suggest that effects of perforant pathway stimulation on the hippocampus, at least in part, are mediated by insulin increase in the dentate gyrus and subsequently activation of its downstream signaling pathway.

Ferruginol Restores SIRT1-PGC-1α-Mediated Mitochondrial Biogenesis and Fatty Acid Oxidation for the Treatment of DOX-Induced Cardiotoxicity

Background: Doxorubicin (DOX), a broad-spectrum chemotherapy drug, has life-threatening cardiotoxicity. Therefore, searching cardioprotective drugs for DOX-induced cardiotoxicity (DIC) is urgently needed.

Objectives: This study aimed to explore cardioprotective effect and specific mechanism by which Ferruginol (FGL) attenuated DIC in vivo and in vitro.

Methods: We evaluated the cardioprotection of FGL and performed high-throughput RNA-Seq on a DIC mouse. Whereafter, multiple methods, including western blot, RT-qPCR, a transmission electron microscope, CO-IP, immunofluorescence, and other staining methods, and antagonist of SIRT1 and PGC-1α were utilized to confirm the cardioprotection and molecular mechanism of FGL.

Results: FGL-exerted cardioprotection manifested as enhanced cardiac function and reduced structural damage and apoptosis. The transcriptome and other results revealed that FGL facilitated PGC-1α-mediated mitochondrial biogenesis and fatty acid oxidation (MB and FAO) by increasing the expression of PGC-1α and concurrently promoting the expression of SIRT1-enhancing deacetylase SIRT1 deacetylating and activating PGC-1α.

Conclusions: These results documented that FGL exerted cardioprotective effects restoring MB&FAO via the SIRT1–PGC-1α axis.

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

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

NEW & NOTEWORTHY Parvalbumin expressing interneurons are considered to play an important role in regulating cortical activity. We were surprised, therefore, to find that knocking down the transcriptional coactivator, PGC-1α, specifically in this class of interneurons appears to slow ictogenesis. This anti-ictogenic effect is associated with reduced activity in preictal discharges, but with a far longer period of these discharges before the first seizure-like events finally start. Thus, PGC-1α knockdown may promote schizophrenia while reducing epileptic tendencies.

Deletion of PRAK Mitigates the Mitochondria Function and Suppresses Insulin Signaling in C2C12 Myoblasts Exposed to High Glucose

Background: p38 regulated/activated protein kinase (PRAK) plays a crucial role in modulating cell death and survival. However, the role of PRAK in the regulation of metabolic stress remains unclear. We examined the effects of PRAK on cell survival and mitochondrial function in C2C12 myoblasts in response to high glucose stresses.

Methods: PRAK of C2C12 myoblasts was knocked out by using CRISPR/Cas-9 genome editing technology. Both wild type and PRAK^−/− C2C12 cells were exposed to high glucose at the concentration of 30 mmol/L to induce metabolic stress. The effect of irisin, an adipomyokine, on both wild type and PRAK^−/− cells was determined to explore its relationship with RPAK. Cell viability, ATP product, glucose uptake, mitochondrial damage, and insulin signaling were assessed.

Results: PRAK knockout decreased C2C12 viability in response to high glucose stress as evident by MTT assay in association with the reduction of ATP and glucose uptake. PRAK knockout enhanced apoptosis of C2C12 myoblasts in response to high glucose, consistent with an impairment in mitochondrial function, by decreasing mitochondrial membrane potential. PRAK knockout induced impairment of mitochondrial and cell damage were rescued by irisin. PRAK knockout caused decrease in phosphorylated PI3 kinase at Tyr 485, IRS-1 and AMPKα and but did not affect non-phosphorylated PI3 kinase, IRS-1 and AMPKα signaling. High glucose caused the further reduction of phosphorylated PI3 kinase, IRS-1 and AMPKα. Irisin treatment preserved phosphorylated PI3 kinase, IRS-1by rescuing PRAK in high glucose treatment.

Conclusion: Our finding indicates a pivotal role of PRAK in preserving cellular survival, mitochondrial function, and high glucose stress.

Therapeutic potential of PGC-1α in age-related macular degeneration (AMD) - the involvement of mitochondrial quality control, autophagy, and antioxidant response

INTRODUCTION

Age-related macular degeneration (AMD) is the leading, cause of sight loss in the elderly in the Western world. Most patients remain still without any treatment options. The targeting of Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), a transcription co-factor, is a putative therapy against AMD.

AREAS COVERED

The characteristics of AMD and their possible connection with PGC-1α as well as the transcriptional and post-transcriptional control of PGC-1α are discussed. The PGC-1α-driven control of mitochondrial functions, and its involvement in autophagy and antioxidant responses are also examined. Therapeutic possibilities via drugs and epigenetic approaches to enhance PGC-1α expression are discussed. Authors conducted a search of literature mainly from the recent decade from the PubMed database.

EXPERT OPINION

Therapy options in AMD could include PGC-1α activation or stabilization. This could be achieved by a direct elevation of PGC-1α activity, a stabilization or modification of its upstream activators and inhibitors by chemical compounds, like 5-Aminoimidazole-4-carboxamide riboside, metformin, and resveratrol. Furthermore, manipulations with epigenetic modifiers of PGC-1α expression, including miRNAs, e.g. miR-204, are considered. A therapy aimed at PGC-1α up-regulation may be possible in other disorders besides AMD, if they are associated with disturbances in the mitochondria-antioxidant response-autophagy axis.

The Stress Axis in Obesity and Diabetes Mellitus: An Update

The hypothalamic–pituitary–adrenal axis is a tightly regulated system that represents one of the body’s mechanisms for responding to acute and chronic stress. Prolonged stress and/or inadequate regulation of the stress system can lead to a condition of chronic hypercortisolism or, in some cases, a blunted cortisol response to stress, contributing to insulin resistance, increased adiposity and type 2 diabetes mellitus. Moreover, acute and chronic stress can exacerbate or worsen metabolic conditions by supporting an inflammatory state and a tight relationship between stress, inflammation and adipose tissue has been reported and has been a growing subject of interest in recent years. We reviewed and summarized the evidence supporting hypothalamic–pituitary–adrenal axis dysregulation as an important biological link between stress, obesity, inflammation and type 2 diabetes mellitus. Furthermore, we emphasized the possible role of infectious-related stress such as SarsCov2 infection in adrenal axis dysregulation, insulin resistance and diabetes in a bidirectional link. Understanding and better defining the links between stress and obesity or diabetes could contribute to further definition of the pathogenesis and the management of stress-related complications, in which the HPA axis dysregulation has a primary role.

The Essential Role of PRAK in Preserving Cardiac Function and Insulin Resistance in High-Fat Diet-Induced Diabetes

Regulated/activated protein kinase (PRAK) plays a crucial role in modulating biological function. However, the role of PRAK in mediating cardiac dysfunction and metabolic disorders remains unclear. We examined the effects of deletion of PRAK on modulating cardiac function and insulin resistance in mice exposed to a high-fat diet (HFD). Wild-type and PRAK^-/- mice at 8 weeks old were exposed to either chow food or HFD for a consecutive 16 weeks. Glucose tolerance tests and insulin tolerance tests were employed to assess insulin resistance. Echocardiography was employed to assess myocardial function. Western blot was used to determine the molecular signaling involved in phosphorylation of IRS-1, AMPKα, ERK-44/42, and irisin. Real time-PCR was used to assess the hypertrophic genes of the myocardium. Histological analysis was employed to assess the hypertrophic response, interstitial myocardial fibrosis, and apoptosis in the heart. Western blot was employed to determine cellular signaling pathway. HFD-induced metabolic stress is indicated by glucose intolerance and insulin intolerance. PRAK knockout aggravated insulin resistance, as indicated by glucose intolerance and insulin intolerance testing as compared with wild-type littermates. As compared with wild-type mice, hyperglycemia and hypercholesterolemia were manifested in PRAK-knockout mice following high-fat diet intervention. High-fat diet intervention displayed a decline in fractional shortening and ejection fraction. However, deletion of PRAK exacerbated the decline in cardiac function as compared with wild-type mice following HFD treatment. In addition, PRAK knockout mice enhanced the expression of myocardial hypertrophic genes including ANP, BNP, and βMHC in HFD treatment, which was also associated with an increase in cardiomyocyte size and interstitial fibrosis. Western blot indicated that deletion of PRAK induces decreases in phosphorylation of IRS-1, AMPKα, and ERK44/42 as compared with wild-type controls. Our finding indicates that deletion of PRAK promoted myocardial dysfunction, cardiac remodeling, and metabolic disorders in response to HFD.

Post-translational regulation of PGC-1α modulates fibrotic repair

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease associated with mitochondrial oxidative stress. Mitochondrial reactive oxygen species (mtROS) are important for cell homeostasis by regulating mitochondrial dynamics. Here, we show that IPF BAL cells exhibited increased mitochondrial biogenesis that is, in part, due to increased nuclear expression of peroxisome proliferator-activated receptor-ɣ (PPARɣ) coactivator (PGC)-1α. Increased PPARGC1A mRNA expression directly correlated with reduced pulmonary function in IPF subjects. Oxidant-mediated activation of the p38 MAPK via Akt1 regulated PGC-1α activation to increase mitochondrial biogenesis in monocyte-derived macrophages. Demonstrating the importance of PGC-1α in fibrotic repair, mice harboring a conditional deletion of Ppargc1a in monocyte-derived macrophages or mice administered a chemical inhibitor of mitochondrial division had reduced biogenesis and increased apoptosis, and the mice were protected from pulmonary fibrosis. These observations suggest that Akt1-mediated regulation of PGC-1α maintains mitochondrial homeostasis in monocyte-derived macrophages to induce apoptosis resistance, which contributes to the pathogenesis of pulmonary fibrosis.

Mitostasis, Calcium and Free Radicals in Health, Aging and Neurodegeneration

Mitochondria play key roles in ATP supply, calcium homeostasis, redox balance control and apoptosis, which in neurons are fundamental for neurotransmission and to allow synaptic plasticity. Their functional integrity is maintained by mitostasis, a process that involves mitochondrial transport, anchoring, fusion and fission processes regulated by different signaling pathways but mainly by the peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α). PGC-1α also favors Ca²⁺ homeostasis, reduces oxidative stress, modulates inflammatory processes and mobilizes mitochondria to where they are needed. To achieve their functions, mitochondria are tightly connected to the endoplasmic reticulum (ER) through specialized structures of the ER termed mitochondria-associated membranes (MAMs), which facilitate the communication between these two organelles mainly to aim Ca²⁺ buffering. Alterations in mitochondrial activity enhance reactive oxygen species (ROS) production, disturbing the physiological metabolism and causing cell damage. Furthermore, cytosolic Ca²⁺ overload results in an increase in mitochondrial Ca²⁺, resulting in mitochondrial dysfunction and the induction of mitochondrial permeability transition pore (mPTP) opening, leading to mitochondrial swelling and cell death through apoptosis as demonstrated in several neuropathologies. In summary, mitochondrial homeostasis is critical to maintain neuronal function; in fact, their regulation aims to improve neuronal viability and to protect against aging and neurodegenerative diseases.

PGC1s and Beyond: Disentangling the Complex Regulation of Mitochondrial and Cellular Metabolism

Metabolism is the central engine of living organisms as it provides energy and building blocks for many essential components of each cell, which are required for specific functions in different tissues. Mitochondria are the main site for energy production in living organisms and they also provide intermediate metabolites required for the synthesis of other biologically relevant molecules. Such cellular processes are finely tuned at different levels, including allosteric regulation, posttranslational modifications, and transcription of genes encoding key proteins in metabolic pathways. Peroxisome proliferator activated receptor γ coactivator 1 (PGC1) proteins are transcriptional coactivators involved in the regulation of many cellular processes, mostly ascribable to metabolic pathways. Here, we will discuss some aspects of the cellular processes regulated by PGC1s, bringing up some examples of their role in mitochondrial and cellular metabolism, and how metabolic regulation in mitochondria by members of the PGC1 family affects the immune system. We will analyze how PGC1 proteins are regulated at the transcriptional and posttranslational level and will also examine other regulators of mitochondrial metabolism and the related cellular functions, considering approaches to identify novel mitochondrial regulators and their role in physiology and disease. Finally, we will analyze possible therapeutical perspectives currently under assessment that are applicable to different disease states.

Pathophysiological Roles of Stress-Activated Protein Kinases in Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is one of the most symptomatic progressive fibrotic lung diseases, in which patients have an extremely poor prognosis. Therefore, understanding the precise molecular mechanisms underlying pulmonary fibrosis is necessary for the development of new therapeutic options. Stress-activated protein kinases (SAPKs), c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase (p38) are ubiquitously expressed in various types of cells and activated in response to cellular environmental stresses, including inflammatory and apoptotic stimuli. Type II alveolar epithelial cells, fibroblasts, and macrophages are known to participate in the progression of pulmonary fibrosis. SAPKs can control fibrogenesis by regulating the cellular processes and molecular functions in various types of lung cells (including cells of the epithelium, interstitial connective tissue, blood vessels, and hematopoietic and lymphoid tissue), all aspects of which remain to be elucidated. We recently reported that the stepwise elevation of intrinsic p38 signaling in the lungs is correlated with a worsening severity of bleomycin-induced fibrosis, indicating an importance of this pathway in the progression of pulmonary fibrosis. In addition, a transcriptome analysis of RNA-sequencing data from this unique model demonstrated that several lines of mechanisms are involved in the pathogenesis of pulmonary fibrosis, which provides a basis for further studies. Here, we review the accumulating evidence for the spatial and temporal roles of SAPKs in pulmonary fibrosis.

The Role of Thyroid Hormone in Neuronal Protection

Thyroid hormone is essential for brain development and brain function in the adult. During development, thyroid hormone acts in a spatial and temporal-specific manner to regulate the expression of genes essential for normal neural cell differentiation, migration, and myelination. In the adult brain, thyroid hormone is important for maintaining normal brain function. Thyroid hormone excess, hyperthyroidism, and thyroid hormone deficiency, hypothyroidism, are associated with disordered brain function, including depression, memory loss, impaired cognitive function, irritability, and anxiety. Adequate thyroid hormone levels are required for normal brain function. Thyroid hormone acts through a cascade of signaling components: activation and inactivation by deiodinase enzymes, thyroid hormone membrane transporters, and nuclear thyroid hormone receptors. Additionally, the hypothalamic-pituitary-thyroid axis, with negative feedback of thyroid hormone on thyrotropin-releasing hormone (TRH) and thyroid-stimulating hormone (TSH) secretion, regulates serum thyroid hormone levels in a narrow range. Animal and human studies have shown both systemic and local reduction in thyroid hormone availability in neurologic disease and after brain trauma. Treatment with thyroid hormone and selective thyroid hormone analogs has resulted in a reduction in injury and improved recovery. This article will describe the thyroid hormone signal transduction pathway in the brain and the role of thyroid hormone in the aging brain, neurologic diseases, and the protective role when administered after traumatic brain injury. © 2021 American Physiological Society. Compr Physiol 11:1-21, 2021.

Cancer-Mediated Muscle Cachexia: Etiology and Clinical Management

Muscle cachexia has a major detrimental impact on cancer patients, being responsible for 30% of all cancer deaths. It is characterized by a debilitating loss in muscle mass and function, which ultimately deteriorates patients' quality of life and dampens therapeutic treatment efficacy. Muscle cachexia stems from widespread alterations in whole-body metabolism as well as immunity and neuroendocrine functions and these global defects often culminate in aberrant signaling within skeletal muscle, causing muscle protein breakdown and attendant muscle atrophy. This review summarizes recent landmark discoveries that significantly enhance our understanding of the molecular etiology of cancer-driven muscle cachexia and further discuss emerging therapeutic approaches seeking to simultaneously target those newly discovered mechanisms to efficiently curb this lethal syndrome.

Insulin Resistance and Diabetes Mellitus in Alzheimer's Disease

Type 2 diabetes mellitus is a progressive disease that is characterized by the appearance of insulin resistance. The term insulin resistance is very wide and could affect different proteins involved in insulin signaling, as well as other mechanisms. In this review, we have analyzed the main molecular mechanisms that could be involved in the connection between type 2 diabetes and neurodegeneration, in general, and more specifically with the appearance of Alzheimer's disease. We have studied, in more detail, the different processes involved, such as inflammation, endoplasmic reticulum stress, autophagy, and mitochondrial dysfunction.

Pharmacological inhibition of PI5P4Kα/β disrupts cell energy metabolism and selectively kills p53-null tumor cells

Most human cancer cells harbor loss-of-function mutations in the p53 tumor suppressor gene. Genetic experiments have shown that phosphatidylinositol 5-phosphate 4-kinase α and β (PI5P4Kα and PI5P4Kβ) are essential for the development of late-onset tumors in mice with germline p53 deletion, but the mechanism underlying this acquired dependence remains unclear. PI5P4K has been previously implicated in metabolic regulation. Here, we show that inhibition of PI5P4Kα/β kinase activity by a potent and selective small-molecule probe disrupts cell energy homeostasis, causing AMPK activation and mTORC1 inhibition in a variety of cell types. Feedback through the S6K/insulin receptor substrate (IRS) loop contributes to insulin hypersensitivity and enhanced PI3K signaling in terminally differentiated myotubes. Most significantly, the energy stress induced by PI5P4Kαβ inhibition is selectively toxic toward p53-null tumor cells. The chemical probe, and the structural basis for its exquisite specificity, provide a promising platform for further development, which may lead to a novel class of diabetes and cancer drugs.

Mitochondrial Disruption Is Involved in the Effect of Nuclear Factor of Activated T cells, Cytoplasmic 4 on Aggravating Cardiomyocyte Hypertrophy

ABSTRACT

Nuclear factor of activated T cells, cytoplasmic 4 (NFATc4), a nuclear transcription factor, has been implicated in cardiac hypertrophy through the enhancement of hypertrophic gene expression. However, the role of NFATc4 in mitochondrial modulation is mostly unknown. The current study aimed to investigate the role of NFATc4 in regulating mitochondrial function during phenylephrine (PE)-induced cardiac hypertrophy. Our results showed that overexpression of NFATc4 aggravated the PE-induced decrease in mitochondrial genesis, membrane potential, and mitochondrial gene expression as well as impaired mitochondrial respiration. However, knockdown of NFATc4 relieved PE-induced perturbations in mitochondria and cardiomyocyte hypertrophy. Mechanistically, by activating phosphoinositide-dependent kinase 1 and promoting a combination of AKT and phosphoinositide-dependent kinase 1, phosphorylation and sequential acetylation of PGC-1α were aggravated by NFATc4 and suppressed the activity of PGC-1α. In conclusion, NFATc4-regulated factors were shown to be associated with mitochondrial function and exacerbated PE-induced mitochondrial dysfunction. These findings revealed new roles of NFATc4 in cardiac hypertrophy.

Folliculin: A Regulator of Transcription Through AMPK and mTOR Signaling Pathways

Folliculin (FLCN) is a tumor suppressor gene responsible for the inherited Birt-Hogg-Dubé (BHD) syndrome, which affects kidneys, skin and lungs. FLCN is a highly conserved protein that forms a complex with folliculin interacting proteins 1 and 2 (FNIP1/2). Although its sequence does not show homology to known functional domains, structural studies have determined a role of FLCN as a GTPase activating protein (GAP) for small GTPases such as Rag GTPases. FLCN GAP activity on the Rags is required for the recruitment of mTORC1 and the transcriptional factors TFEB and TFE3 on the lysosome, where mTORC1 phosphorylates and inactivates these factors. TFEB/TFE3 are master regulators of lysosomal biogenesis and function, and autophagy. By this mechanism, FLCN/FNIP complex participates in the control of metabolic processes. AMPK, a key regulator of catabolism, interacts with FLCN/FNIP complex. FLCN loss results in constitutive activation of AMPK, which suggests an additional mechanism by which FLCN/FNIP may control metabolism. AMPK regulates the expression and activity of the transcriptional cofactors PGC1α/β, implicated in the control of mitochondrial biogenesis and oxidative metabolism. In this review, we summarize our current knowledge of the interplay between mTORC1, FLCN/FNIP, and AMPK and their implications in the control of cellular homeostasis through the transcriptional activity of TFEB/TFE3 and PGC1α/β. Other pathways and cellular processes regulated by FLCN will be briefly discussed.

Pellino1 deficiency reprograms cardiomyocytes energy metabolism in lipopolysaccharide-induced myocardial dysfunction

Pellino1 has been shown to regulate proinflammatory genes by activating the nuclear factor kappa B (NF-κB) and Toll-like receptor (TLR) signaling pathways, which are important in the pathological development of lipopolysaccharide (LPS)-induced myocarditis. However, it is still unknown whether silencing Pellino1 (si-Pellino1) has a therapeutic effect on this disease. Here, we showed that silencing Pellino1 can be a potential protective strategy for abnormal myocardial energy metabolism in LPS-induced myocarditis. We used liquid chromatography electrospray–ionization tandem mass spectrometry (LC–MS/MS) to analyze samples from si-Pellino1 neonatal rat cardiac myocytes (NRCMs) treated with LPS or left untreated. After normalization of the data, metabolite interaction analysis of matched KEGG pathway associations following si-Pellino1 treatment was applied, accompanied by interaction analysis of gene and metabolite associations after this treatment. Moreover, we used western blot (WB) and polymerase chain reaction (PCR) analyses to determine the expression of genes involved in regulating cardiac energy and energy metabolism in different groups. LC–MS-based metabolic profiling analysis demonstrated that si-Pellino1 treatment could alleviate or even reverse LPS-induced cellular damage by altering cardiomyocytes energy metabolism accompanied by changes in key genes (Cs, Cpt2, and Acadm) and metabolites (3-oxoocotanoyl-CoA, hydroxypyruvic acid, lauroyl-CoA, and NADPH) in NRCMs. Overall, our study unveiled the promising cardioprotective effect of silencing Pellino1 in LPS-induced myocarditis through fuel and energy metabolic regulation, which can also serve as biomarkers for this disease.

Re-Evaluating the Oxidative Phenotype: Can Endurance Exercise Save the Western World?

Mitochondria are popularly called the "powerhouses" of the cell. They promote energy metabolism through the tricarboxylic acid (TCA) cycle and oxidative phosphorylation, which in contrast to cytosolic glycolysis are oxygen-dependent and significantly more substrate efficient. That is, mitochondrial metabolism provides substantially more cellular energy currency (ATP) per macronutrient metabolised. Enhancement of mitochondrial density and metabolism are associated with endurance training, which allows for the attainment of high relative VO2 max values. However, the sedentary lifestyle and diet currently predominant in the Western world lead to mitochondrial dysfunction. Underdeveloped mitochondrial metabolism leads to nutrient-induced reducing pressure caused by energy surplus, as reduced nicotinamide adenine dinucleotide (NADH)-mediated high electron flow at rest leads to "electron leak" and a chronic generation of superoxide radicals (O2-). Chronic overload of these reactive oxygen species (ROS) damages cell components such as DNA, cell membranes, and proteins. Counterintuitively, transiently generated ROS during exercise contributes to adaptive reduction-oxidation (REDOX) signalling through the process of cellular hormesis or "oxidative eustress" defined by Helmut Sies. However, the unaccustomed, chronic oxidative stress is central to the leading causes of mortality in the 21st century-metabolic syndrome and the associated cardiovascular comorbidities. The endurance exercise training that improves mitochondrial capacity and the protective antioxidant cellular system emerges as a universal intervention for mitochondrial dysfunction and resultant comorbidities. Furthermore, exercise might also be a solution to prevent ageing-related degenerative diseases, which are caused by impaired mitochondrial recycling. This review aims to break down the metabolic components of exercise and how they translate to athletic versus metabolically diseased phenotypes. We outline a reciprocal relationship between oxidative metabolism and inflammation, as well as hypoxia. We highlight the importance of oxidative stress for metabolic and antioxidant adaptation. We discuss the relevance of lactate as an indicator of critical exercise intensity, and inferring from its relationship with hypoxia, we suggest the most appropriate mode of exercise for the case of a lost oxidative identity in metabolically inflexible patients. Finally, we propose a reciprocal signalling model that establishes a healthy balance between the glycolytic/proliferative and oxidative/prolonged-ageing phenotypes. This model is malleable to adaptation with oxidative stress in exercise but is also susceptible to maladaptation associated with chronic oxidative stress in disease. Furthermore, mutations of components involved in the transcriptional regulatory mechanisms of mitochondrial metabolism may lead to the development of a cancerous phenotype, which progressively presents as one of the main causes of death, alongside the metabolic syndrome.

miR-384-5p regulates inflammation in Candida albicans-induced acute lung injury by downregulating PGC1β and enhancing the activation of Candida albicans-triggered signaling pathways

Acute lung injury (ALI) is one of the most prevalent respiratory syndromes of excessive inflammatory reaction during lung infection. Candida albicans (C. albicans) infection is among the leading causes of ALI. MicroRNAs (miRNAs) regulate the expression of target mRNAs, including those involved in inflammatory processes, by binding to the 3'UTR. To date, the roles of miRNAs in C. albicans-induced ALI remain unclear. In this study, we investigated the role of miR-384-5p in C. albicans-induced ALI and its underlying molecular mechanism. RT-PCR, Western blot, ELISA, Myeloperoxidase (MPO) assay, microRNA target analysis, transient transfection, and luciferase reporter assay were utilized. In vivo study was conducted on mouse model. The expression of miR-384-5p was upregulated and positively correlated with inflammatory cytokine production in lung tissues and RAW264.7 and J774A.1 macrophages infected with C. albicans. The miR-384-5p inhibitor alleviated the inflammatory reaction induced by C. albicans. Target prediction analysis revealed that PGC1β was a target of miR-384-5p, which was further validated by the PGC1β 3'-UTR luciferase assay and the inverse correlation between the expression of miR-384-5p and PGC1β in C. albicans-infected ALI tissues and macrophages. Moreover, macrophages transfected with miR-384-5p mimic exhibited reduced levels of PGC1β. The suppression of the expression of PGC1β by C. albicans infection in the macrophages was abrogated by miR-384-5p inhibitor. Then, we demonstrated that PGC1β played an inhibitory role in C. albicans-induced production of inflammatory cytokines. Furthermore, suppression of miR-384-5p in macrophages inhibited the activation of the NF-κB, MAPK, and Akt signaling pathways triggered by C. albicans, but not the STAT3 pathway. These results demonstrate that miR-384-5p contributes to C. albicans-induced ALI at least in part by targeting PGC1β and enhancing the activation of the NF-κB, MAPK, and Akt inflammatory signaling pathways. Thus, targeting miR-384-5p might exert a protective effect on C. albicans-induced ALI.

Caffeine protects against stress-induced murine depression through activation of PPARγC1α-mediated restoration of the kynurenine pathway in the skeletal muscle

Exercise prevents depression through peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α)-mediated activation of a particular branch of the kynurenine pathway. From kynurenine (KYN), two independent metabolic pathways produce neurofunctionally different metabolites, mainly in somatic organs: neurotoxic intermediate metabolites via main pathway and neuroprotective end product, kynurenic acid (KYNA) via the branch. Elevated levels of KYN have been found in patients with depression. Herein, we investigated whether and how caffeine prevents depression, focusing on the kynurenine pathway. Mice exposed to chronic mild stress (CMS) exhibited depressive-like behaviours with an increase and decrease in plasma levels of pro-neurotoxic KYN and neuroprotective KYNA, respectively. However, caffeine rescued CMS-exposed mice from depressive-like behaviours and restored the plasma levels of KYN and KYNA. Concomitantly, caffeine induced a key enzyme converting KYN into KYNA, namely kynurenine aminotransferase-1 (KAT1), in murine skeletal muscle. Upon caffeine stimulation murine myotubes exhibited KAT1 induction and its upstream PGC-1α sustainment. Furthermore, a proteasome inhibitor, but not translational inhibitor, impeded caffeine sustainment of PGC-1α, suggesting that caffeine induced KAT1 by inhibiting proteasomal degradation of PGC-1α. Thus, caffeine protection against CMS-induced depression may be associated with sustainment of PGC-1α levels and the resultant KAT1 induction in skeletal muscle, and thereby consumption of pro-neurotoxic KYN.

PGC-1s in the Spotlight with Parkinson's Disease

Parkinson's disease is one of the most common neurodegenerative disorders worldwide, characterized by a progressive loss of dopaminergic neurons mainly localized in the substantia nigra pars compacta. In recent years, the detailed analyses of both genetic and idiopathic forms of the disease have led to a better understanding of the molecular and cellular pathways involved in PD, pointing to the centrality of mitochondrial dysfunctions in the pathogenic process. Failure of mitochondrial quality control is now considered a hallmark of the disease. The peroxisome proliferator-activated receptor gamma coactivator 1 (PGC-1) family acts as a master regulator of mitochondrial biogenesis. Therefore, keeping PGC-1 level in a proper range is fundamental to guarantee functional neurons. Here we review the major findings that tightly bond PD and PGC-1s, raising important points that might lead to future investigations.

Time-restricted feeding attenuates gluconeogenic activity through inhibition of PGC-1α expression and activity

BACKGROUND

Time-restricted feeding (TRF), a key component of intermittent fasting regimens, has gained considerable attention in recent years due to reversing obesity and insulin resistance. To the best of our knowledge, here, we reported for the first time the underlying mechanistic therapeutic efficacy of TRF against hepatic gluconeogenic activity in obese mice.

METHODS

The obese mice were subjected to either ad lib or TRF of a high fat diet for 8 h per day for 4 weeks. Western blotting, qRT-PCR, and plasma biochemical analyses were applied.

RESULTS

The present findings showed that TRF regimen reduced food intake, and reversed high fat diet-induced glucose intolerance, hyperglycemia and insulin resistance in mice of high fat diet-induced obesity. Mechanistically, we confirmed that TRF regimen protected against hyperglycemia and ameliorated hepatic gluconeogenic activity through inhibition of p38 MAPK/SIRT1/PGC-1α signal pathway.

CONCLUSION

Our findings suggest that TRF regimen might be a potential novel nonpharmacological strategy against obesity/diabetes-induced hyperglycemia and insulin resistance.

Hypoxic training upregulates mitochondrial turnover and angiogenesis of skeletal muscle in mice

AIMS

Hypoxic training promotes human cardiopulmonary function and exercise performance efficiently, but the myocellular mechanism has been less studied. We aimed to examine the effects of hypoxic trainings on mitochondrial turnover and vascular remodeling of skeletal muscle.

MAIN METHODS

C57BL/6 J mice were divided into control, hypoxic exposure, exercise training, "live high-train low" (LHTL), and "live low-train high" (LLTH) groups (n = 8/group). Western blot and immunohistochemistry were used to evaluate mitochondrial turnover of gastrocnemius and angiogenesis of quadriceps after six weeks interventions.

KEY FINDINGS

Compared with control group, both LHTL and LLTH increased phosphorylation levels of p38 MAPK markedly (p < 0.05). LLTH also elevated PGC-1α protein expression significantly (p < 0.05). All interventions did not influence Bnip3 and Drp-1 proteins levels (p > 0.05), while LLTH enhanced Parkin and Mff protein contents significantly (p < 0.05). Immunohistochemical analysis showed both LHTL and LLTH promoted CD31 and VEGF expressions (p < 0.05). ATP content, citrate synthase activities of gastrocnemius were robustly elevated in LHTL and LLTH groups (p < 0.01). The exercise training increased Mff protein and ATP content in gastrocnemius as well as VEGF expression in quadriceps (p < 0.05). The hypoxic exposure also increased ATP content, citrate synthase, and ATP synthase activities in gastrocnemius as well as VEGF expression in quadriceps (p < 0.01).

SIGNIFICANCE

Our results suggested that hypoxic trainings, especially LLTH, promoted mitochondrial turnover and angiogenesis of skeletal muscle, which may be an underlying mechanism of hypoxic training-induced exercise capacity.

Human skeletal muscle fiber type-specific responses to sprint interval and moderate-intensity continuous exercise: acute and training-induced changes

There are limited and equivocal data regarding potential fiber type-specific differences in the human skeletal muscle response to sprint interval training (SIT), including how this compares with moderate-intensity continuous training (MICT). We examined mixed-muscle and fiber type-specific responses to a single session (study 1) and to 12 wk (study 2) of MICT and SIT using Western blot analysis. MICT consisted of 45 min of cycling at ∼70% of maximal heart rate, and SIT involved 3 × 20-s "all-out" sprints interspersed with 2 min of recovery. Changes in signaling proteins involved in mitochondrial biogenesis in mixed-muscle and pooled fiber samples were similar after acute MICT and SIT. This included increases in the ratios of phosphorylated to total acetyl-CoA carboxylase and p38 mitogen-activated protein kinase protein content (main effects, P < 0.05). Following training, mitochondrial content markers including the protein content of cytochrome c oxidase subunit IV and NADH:ubiquinone oxidoreductase subunit A9 were increased similarly in mixed-muscle and type IIa fibers (main effects, P < 0.05). In contrast, only MICT increased these markers of mitochondrial content in type I fibers (interactions, P < 0.05). MICT and SIT also similarly increased the content of mitochondrial fusion proteins optic atrophy 1 (OPA1) and mitofusin 2 in mixed-muscle, and OPA1 in pooled fiber samples (main effects, P < 0.02). In summary, acute MICT and SIT elicited similar fiber type-specific responses of signaling proteins involved in mitochondrial biogenesis, whereas 12 wk of training revealed differential responses of mitochondrial content markers in type I but not type IIa fibers.NEW & NOTEWORTHY We examined mixed-muscle and fiber type-specific responses to a single session and to 12 wk of moderate-intensity continuous training (MICT) and sprint interval training (SIT) in humans. Both interventions elicited generally similar responses, although the training-induced increases in type I fiber-specific markers of mitochondrial content were greater in MICT than in SIT. These findings advance our understanding of the potential role of fiber type-specific changes in determining the human skeletal muscle response to intermittent and continuous exercise.

GCN5 acetyltransferase in cellular energetic and metabolic processes

General Control Non-repressed 5 protein (GCN5), encoded by the mammalian gene Kat2a, is the first histone acetyltransferase discovered to link histone acetylation to transcriptional activation [1]. The enzymatic activity of GCN5 is linked to cellular metabolic and energetic states regulating gene expression programs. GCN5 has a major impact on energy metabolism by i) sensing acetyl-CoA, a central metabolite and substrate of the GCN5 catalytic reaction, and ii) acetylating proteins such as PGC-1α, a transcriptional coactivator that controls genes linked to energy metabolism and mitochondrial biogenesis. PGC-1α is biochemically associated with the GCN5 protein complex during active metabolic reprogramming. In the first part of the review, we examine how metabolism can change GCN5-dependent histone acetylation to regulate gene expression to adapt cells. In the second part, we summarize the GCN5 function as a nutrient sensor, focusing on non-histone protein acetylation, mainly the metabolic role of PGC-1α acetylation across different tissues.

Diversity and versatility of p38 kinase signalling in health and disease

The ability of cells to deal with different types of stressful situations in a precise and coordinated manner is key for survival and involves various signalling networks. Over the past 25 years, p38 kinases — in particular, p38α — have been implicated in the cellular response to stress at many levels. These span from environmental and intracellular stresses, such as hyperosmolarity, oxidative stress or DNA damage, to physiological situations that involve important cellular changes such as differentiation. Given that p38α controls a plethora of functions, dysregulation of this pathway has been linked to diseases such as inflammation, immune disorders or cancer, suggesting the possibility that targeting p38α could be of therapeutic interest. In this Review, we discuss the organization of this signalling pathway focusing on the diversity of p38α substrates, their mechanisms and their links to particular cellular functions. We then address how the different cellular responses can be generated depending on the signal received and the cell type, and highlight the roles of this kinase in human physiology and in pathological contexts.

p38α — the best-characterized member of the p38 kinase family — is a key mediator of cellular stress responses. p38α is activated by a plethora of signals and functions through a multitude of substrates to regulate different cellular behaviours. Understanding context-dependent p38α signalling provides important insights into p38α roles in physiology and pathology.

NT-PGC-1α deficiency attenuates high-fat diet-induced obesity by modulating food intake, fecal fat excretion and intestinal fat absorption

Transcriptional coactivator PGC-1α and its splice variant NT-PGC-1α regulate metabolic adaptation by modulating many gene programs. Selective ablation of PGC-1α attenuates diet-induced obesity through enhancing fatty acid oxidation and thermogenesis by upregulation of NT-PGC-1α in brown adipose tissue (BAT). Recently, we have shown that selective ablation of NT-PGC-1α reduces fatty acid oxidation in BAT. Thus, the objective of this study was to test our hypothesis that NT-PGC-1α^−/− mice would be more prone to diet-induced obesity. Male and female NT-PGC-1α^+/+ (WT) and NT-PGC-1α^−/− mice were fed a regular chow or 60% high-fat (HF) diet for 16 weeks. Contrary to our expectations, both male and female NT-PGC-1α^−/− mice fed HFD were protected from diet-induced obesity, with more pronounced effects in females. This lean phenotype was primarily driven by reduced dietary fat intake. Intriguingly, HFD-fed female, but not male, NT-PGC-1α^−/− mice further exhibited decreased feed efficiency, which was closely associated with increased fecal fat excretion and decreased uptake of fatty acids by the intestinal enterocytes and adipocytes with a concomitant decrease in fatty acid transporter gene expression. Collectively, our results highlight the role for NT-PGC-1α in regulating whole body lipid homeostasis under HFD conditions.

Molecular Basis for the Therapeutic Effects of Exercise on Mitochondrial Defects

Mitochondrial dysfunction is common to many organ system disorders, including skeletal muscle. Aging muscle and diseases of muscle are often accompanied by defective mitochondrial ATP production. This manuscript will focus on the pre-clinical evidence supporting the use of regular exercise to improve defective mitochondrial metabolism and function in skeletal muscle, through the stimulation of mitochondrial turnover. Examples from aging muscle, muscle-specific mutations and cancer cachexia will be discussed. We will also examine the effects of exercise on the important mitochondrial regulators PGC-1α, and Parkin, and summarize the effects of exercise to reverse mitochondrial dysfunction (e.g., ROS production, apoptotic susceptibility, cardiolipin synthesis) in muscle pathology. This paper will illustrate the breadth and benefits of exercise to serve as "mitochondrial medicine" with age and disease.

Baoyuan Jiedu Decoction Alleviates Cancer-Induced Myotube Atrophy by Regulating Mitochondrial Dynamics Through p38 MAPK/PGC-1α Signaling Pathway

Cancer cachexia is a multifactorial syndrome characterized by continuous body wasting and loss of skeletal muscle. Impaired mitochondria function is closely associated with muscle atrophy in cancer cachexia. Our previous study confirmed the effectiveness of Baoyuan Jiedu decoction (BJD) in inhibiting cancer-induced muscle atrophy in an in vivo model. However, little is known about its mechanisms in regulating mitochondria dysfunction. In this study, we evaluated the therapeutic effect and action mechanisms of BJD against atrophy both in the Lewis-conditioned medium induced C2C12 myotube atrophy model and in a BALB/c mice xenograft model using mouse colon cancer C26 cells. The mitochondrial content was tested by 10-Non-ylacridine orange staining. Expressions of related proteins and mRNAs were detected by western blotting (WB) and qPCR, respectively. As a result, 18 major components were identified in BJD by ultra-high performance liquid chromatography-quadrupole (UHPLC-Q) Exactive analysis. As shown in the in vitro results, BJD treatment prevented prominent myotube atrophy and increased the myotube diameter of C2C12 cells. Besides, BJD treatment increased mitochondrial content and ATPase activity. Furthermore, the protein and mRNA expressions that were related to mitochondrial functions and generation such as cytochrome-c oxidase IV, Cytochrome C, nuclear respiratory factor 1, and mitochondrial transcription factor A were significantly increased in BJD treatment compared to the control group. The in vivo results showed that BJD treatment prevented body weight loss and improved the gastrocnemius index in cachexia mice. Moreover, the expressions of Atrogin-1 and muscle RING-finger protein-1 were decreased by BJD treatment. Mechanically, BJD increased the expression of peroxisome proliferator-activated receptor-gamma coactivator 1, and consistently, inhibited the expression of p38 MAPK and its phosphorylation both in vivo and in vitro. Taken together, this study identified that BJD effectively relieved cancer-induced myotube atrophy and provided a potential mechanism for BJD in regulating mitochondrial dynamics through p38 MAPK/PGC-1α signaling pathway.

Biochemical adaptations in white adipose tissue following aerobic exercise: from mitochondrial biogenesis to browning

Our understanding of white adipose tissue (WAT) biochemistry has evolved over the last few decades and it is now clear that WAT is not simply a site of energy storage, but rather a pliable endocrine organ demonstrating dynamic responsiveness to the effects of aerobic exercise. Similar to its established effects in skeletal muscle, aerobic exercise induces many biochemical adaptations in WAT including mitochondrial biogenesis and browning. While past research has focused on the regulation of these biochemical processes, there has been renewed interest as of late given the potential of harnessing WAT mitochondrial biogenesis and browning to treat obesity and type II diabetes. Unfortunately, despite increasing evidence that innumerable factors, both exercise induced and pharmacological, can elicit these biochemical adaptations in WAT, the underlying mechanisms remain poorly defined. Here, we begin with a historical account of our understanding of WAT exercise biochemistry before presenting detailed evidence in favour of an up-to-date model by which aerobic exercise induces mitochondrial biogenesis and browning in WAT. Specifically, we discuss how aerobic exercise induces increases in WAT lipolysis and re-esterification and how this could be a trigger that activates the cellular energy sensor 5' AMP-activated protein kinase to mediate the induction of mitochondrial biogenesis and browning via the transcriptional co-activator peroxisome proliferator-activated receptor gamma co-activator-1 alpha. While this review primarily focuses on mechanistic results from rodent studies special attention is given to the translation of these results, or lack thereof, to human physiology.

Zc3h10 Acts as a Transcription Factor and Is Phosphorylated to Activate the Thermogenic Program

Brown adipose tissue harbors UCP1 to dissipate chemical energy as heat. However, the transcriptional network that governs the thermogenic gene program is incompletely understood. Zc3h10, a CCCH-type zinc finger protein, has recently been reported to bind RNA. However, we report here that Zc3h10 functions as a transcription factor to activate UCP1 not through the enhancer region, but by binding to a far upstream region of the UCP1 promoter. Upon sympathetic stimulation, Zc3h10 is phosphorylated at S126 by p38 mitogen-activated protein kinase (MAPK) to increase binding to the distal region of the UCP1 promoter. Zc3h10, as well as mutant Zc3h10, which cannot bind RNA, enhances thermogenic capacity and energy expenditure, protecting mice from diet-induced obesity. Conversely, Zc3h10 ablation in UCP1⁺ cells in mice impairs thermogenic capacity and lowers oxygen consumption, leading to weight gain. Hence, Zc3h10 plays a critical role in the thermogenic gene program and may present future targets for obesity therapeutics.

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

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

p38 MAPK in Glucose Metabolism of Skeletal Muscle: Beneficial or Harmful?

Skeletal muscles respond to environmental and physiological changes by varying their size, fiber type, and metabolic properties. P38 mitogen-activated protein kinase (MAPK) is one of several signaling pathways that drive the metabolic adaptation of skeletal muscle to exercise. p38 MAPK also participates in the development of pathological traits resulting from excessive caloric intake and obesity that cause metabolic syndrome and type 2 diabetes (T2D). Whereas p38 MAPK increases insulin-independent glucose uptake and oxidative metabolism in muscles during exercise, it contrastingly mediates insulin resistance and glucose intolerance during metabolic syndrome development. This article provides an overview of the apparent contradicting roles of p38 MAPK in the adaptation of skeletal muscles to exercise and to pathological conditions leading to glucose intolerance and T2D. Here, we focus on the involvement of p38 MAPK in glucose metabolism of skeletal muscle, and discuss the possibility of targeting this pathway to prevent the development of T2D.

Impact of Conventional and Atypical MAPKs on the Development of Metabolic Diseases

The family of mitogen-activated protein kinases (MAPKs) consists of fourteen members and has been implicated in regulation of virtually all cellular processes. MAPKs are divided into two groups, conventional and atypical MAPKs. Conventional MAPKs are further classified into four sub-families: extracellular signal-regulated kinases 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK1, 2 and 3), p38 (α, β, γ, δ), and extracellular signal-regulated kinase 5 (ERK5). Four kinases, extracellular signal-regulated kinase 3, 4, and 7 (ERK3, 4 and 7) as well as Nemo-like kinase (NLK) build a group of atypical MAPKs, which are activated by different upstream mechanisms than conventional MAPKs. Early studies identified JNK1/2 and ERK1/2 as well as p38α as a central mediators of inflammation-evoked insulin resistance. These kinases have been also implicated in the development of obesity and diabetes. Recently, other members of conventional MAPKs emerged as important mediators of liver, skeletal muscle, adipose tissue, and pancreatic β-cell metabolism. Moreover, latest studies indicate that atypical members of MAPK family play a central role in the regulation of adipose tissue function. In this review, we summarize early studies on conventional MAPKs as well as recent findings implicating previously ignored members of the MAPK family. Finally, we discuss the therapeutic potential of drugs targeting specific members of the MAPK family.

Nuclear P38: Roles in Physiological and Pathological Processes and Regulation of Nuclear Translocation

The p38 mitogen-activated protein kinase (p38MAPK, termed here p38) cascade is a central signaling pathway that transmits stress and other signals to various intracellular targets in the cytoplasm and nucleus. More than 150 substrates of p38α/β have been identified, and this number is likely to increase. The phosphorylation of these substrates initiates or regulates a large number of cellular processes including transcription, translation, RNA processing and cell cycle progression, as well as degradation and the nuclear translocation of various proteins. Being such a central signaling cascade, its dysregulation is associated with many pathologies, particularly inflammation and cancer. One of the hallmarks of p38α/β signaling is its stimulated nuclear translocation, which occurs shortly after extracellular stimulation. Although p38α/β do not contain nuclear localization or nuclear export signals, they rapidly and robustly translocate to the nucleus, and they are exported back to the cytoplasm within minutes to hours. Here, we describe the physiological and pathological roles of p38α/β phosphorylation, concentrating mainly on the ill-reviewed regulation of p38α/β substrate degradation and nuclear translocation. In addition, we provide information on the p38α/β ’s substrates, concentrating mainly on the nuclear targets and their role in p38α/β functions. Finally, we also provide information on the mechanisms of nuclear p38α/β translocation and its use as a therapeutic target for p38α/β-dependent diseases.

PI3Kα Pathway Inhibition With Doxorubicin Treatment Results in Distinct Biventricular Atrophy and Remodeling With Right Ventricular Dysfunction

Background

Cancer therapies inhibiting PI3Kα (phosphoinositide 3‐kinase‐α)–dependent growth factor signaling, including trastuzumab inhibition of HER2 (Human Epidermal Growth Factor Receptor 2), can cause adverse effects on the heart. Direct inhibition of PI3Kα is now in clinical trials, but the effects of PI3Kα pathway inhibition on heart atrophy, remodeling, and function in the context of cancer therapy are not well understood.

Method and Results

Pharmacological PI3Kα inhibition and heart‐specific genetic deletion of p110α, the catalytic subunit of PI3Kα, was characterized in conjunction with anthracycline (doxorubicin) treatment in female murine models. Biventricular changes in heart morphological characteristics and function were analyzed, with molecular characterization of signaling pathways. Both PI3Kα inhibition and anthracycline therapy promoted heart atrophy and a combined effect of distinct right ventricular dilation, dysfunction, and cardiomyocyte remodeling in the absence of pulmonary arterial hypertension. Congruent findings of right ventricular dilation and dysfunction were seen with pharmacological and genetic suppression of PI3Kα signaling when combined with doxorubicin treatment. Increased p38 mitogen‐activated protein kinase activation was mechanistically linked to heart atrophy and correlated with right ventricular dysfunction in explanted failing human hearts.

Conclusions

The PI3Kα pathway promotes heart atrophy in mice. The right ventricle is specifically at risk for dilation and dysfunction in the setting of PI3K inhibition in conjunction with chemotherapy. Inhibition of p38 mitogen‐activated protein kinase is a proposed therapeutic target to minimize this mode of cardiotoxicity.

Indoprofen prevents muscle wasting in aged mice through activation of PDK1/AKT pathway

BACKGROUND

Muscle wasting, resulting from aging or pathological conditions, leads to reduced quality of life, increased morbidity, and increased mortality. Much research effort has been focused on the development of exercise mimetics to prevent muscle atrophy and weakness. In this study, we identified indoprofen from a screen for peroxisome proliferator-activated receptor γ coactivator α (PGC-1α) inducers and report its potential as a drug for muscle wasting.

METHODS

The effects of indoprofen treatment on dexamethasone-induced atrophy in mice and in 3-phosphoinositide-dependent protein kinase-1 (PDK1)-deleted C2C12 myotubes were evaluated by immunoblotting to determine the expression levels of myosin heavy chain and anabolic-related and oxidative metabolism-related proteins. Young, old, and disuse-induced muscle atrophic mice were administered indoprofen (2 mg/kg body weight) by gavage. Body weight, muscle weight, grip strength, isometric force, and muscle histology were assessed. The expression levels of muscle mass-related and function-related proteins were analysed by immunoblotting or immunostaining.

RESULTS

In young (3-month-old) and aged (22-month-old) mice, indoprofen treatment activated oxidative metabolism-related enzymes and led to increased muscle mass. Mechanistic analysis using animal models and muscle cells revealed that indoprofen treatment induced the sequential activation of AKT/p70S6 kinase (S6K) and AMP-activated protein kinase (AMPK), which in turn can augment protein synthesis and PGC-1α induction, respectively. Structural prediction analysis identified PDK1 as a target of indoprofen and, indeed, short-term treatment with indoprofen activated the PDK1/AKT/S6K pathway in muscle cells. Consistent with this finding, PDK1 inhibition abrogated indoprofen-induced AKT/S6K activation and hypertrophic response.

CONCLUSIONS

Our findings demonstrate the effects of indoprofen in boosting skeletal muscle mass through the sequential activation of PDK1/AKT/S6K and AMPK/PGC-1α. Taken together, our results suggest that indoprofen represents a potential drug to prevent muscle wasting and weakness related to aging or muscle diseases.

The ties that bind: functional clusters in limb-girdle muscular dystrophy

The limb-girdle muscular dystrophies (LGMDs) are a genetically pleiomorphic class of inherited muscle diseases that are known to share phenotypic features. Selected LGMD genetic subtypes have been studied extensively in affected humans and various animal models. In some cases, these investigations have led to human clinical trials of potential disease-modifying therapies, including gene replacement strategies for individual subtypes using adeno-associated virus (AAV) vectors. The cellular localizations of most proteins associated with LGMD have been determined. However, the functions of these proteins are less uniformly characterized, thus limiting our knowledge of potential common disease mechanisms across subtype boundaries. Correspondingly, broad therapeutic strategies that could each target multiple LGMD subtypes remain less developed. We believe that three major "functional clusters" of subcellular activities relevant to LGMD merit further investigation. The best known of these is the glycosylation modifications associated with the dystroglycan complex. The other two, mechanical signaling and mitochondrial dysfunction, have been studied less systematically but are just as promising with respect to the identification of significant mechanistic subgroups of LGMD. A deeper understanding of these disease pathways could yield a new generation of precision therapies that would each be expected to treat a broader range of LGMD patients than a single subtype, thus expanding the scope of the molecular medicines that may be developed for this complex array of muscular dystrophies.

An overview of mammalian p38 mitogen-activated protein kinases, central regulators of cell stress and receptor signaling

The p38 family is a highly evolutionarily conserved group of mitogen-activated protein kinases (MAPKs) that is involved in and helps co-ordinate cellular responses to nearly all stressful stimuli. This review provides a succinct summary of multiple aspects of the biology, role, and substrates of the mammalian family of p38 kinases. Since p38 activity is implicated in inflammatory and other diseases, we also discuss the clinical implications and pharmaceutical approaches to inhibit p38.

Perm1 regulates cardiac energetics as a downstream target of the histone methyltransferase Smyd1

The transcriptional regulatory machinery in mitochondrial bioenergetics is complex and is still not completely understood. We previously demonstrated that the histone methyltransferase Smyd1 regulates mitochondrial energetics. Here, we identified Perm1 (PPARGC-1 and ESRR-induced regulator, muscle specific 1) as a downstream target of Smyd1 through RNA-seq. Chromatin immunoprecipitation assay showed that Smyd1 directly interacts with the promoter of Perm1 in the mouse heart, and this interaction was significantly reduced in mouse hearts failing due to pressure overload for 4 weeks, where Perm1 was downregulated (24.4 ± 5.9% of sham, p<0.05). Similarly, the Perm1 protein level was significantly decreased in patients with advanced heart failure (55.2 ± 13.1% of donors, p<0.05). Phenylephrine (PE)-induced hypertrophic stress in cardiomyocytes also led to downregulation of Perm1 (55.7 ± 5.7% of control, p<0.05), and adenovirus-mediated overexpression of Perm1 rescued PE-induced downregulation of estrogen-related receptor alpha (ERRα), a key transcriptional regulator of mitochondrial energetics, and its target gene, Ndufv1 (Complex I). Pathway enrichment analysis of cardiomyocytes in which Perm1 was knocked-down by siRNA (siPerm1), revealed that the most downregulated pathway was metabolism. Cell stress tests using the Seahorse XF analyzer showed that basal respiration and ATP production were significantly reduced in siPerm1 cardiomyocytes (40.7% and 23.6% of scrambled-siRNA, respectively, both p<0.05). Luciferase reporter gene assay further revealed that Perm1 dose-dependently increased the promoter activity of the ERRα gene and known target of ERRα, Ndufv1 (Complex I). Overall, our study demonstrates that Perm1 is an essential regulator of cardiac energetics through ERRα, as part of the Smyd1 regulatory network.

PGC-1α-mediated regulation of mitochondrial function and physiological implications

The majority of human energy metabolism occurs in skeletal muscle mitochondria emphasizing the importance of understanding the regulation of myocellular mitochondrial function. The transcriptional co-activator peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) has been characterized as a major factor in the transcriptional control of several mitochondrial components. Thus, PGC-1α is often described as a master regulator of mitochondrial biogenesis as well as a central player in regulating the antioxidant defense. However, accumulating evidence suggests that PGC-1α is also involved in the complex regulation of mitochondrial quality beyond biogenesis, which includes mitochondrial network dynamics and autophagic removal of damaged mitochondria. In addition, mitochondrial reactive oxygen species production has been suggested to regulate skeletal muscle insulin sensitivity, which may also be influenced by PGC-1α. This review aims to highlight the current evidence for PGC-1α-mediated regulation of skeletal muscle mitochondrial function beyond the effects on mitochondrial biogenesis as well as the potential PGC-1α-related impact on insulin-stimulated glucose uptake in skeletal muscle. Novelty PGC-1α regulates mitochondrial biogenesis but also has effects on mitochondrial functions beyond biogenesis. Mitochondrial quality control mechanisms, including fission, fusion, and mitophagy, are regulated by PGC-1α. PGC-1α-mediated regulation of mitochondrial quality may affect age-related mitochondrial dysfunction and insulin sensitivity.

Regulation of PGC-1α mediated by acetylation and phosphorylation in MPP+ induced cell model of Parkinson's disease

Background: Parkinson’s disease (PD) is one of the most common neurodegenerative diseases with complex etiology in sporadic cases. Accumulating evidence suggests that oxidative stress and defects in mitochondrial dynamics are associated with the pathogenesis of PD. The oxidative stress and mitochondrial dynamics are regulated strictly by peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α). We investigated whether acetylation and phosphorylation of PGC-1α contribute to protecting neuronal cell against oxidative stress.

Results: We found that acetylation and phosphorylation mediated the nuclear translocation of PGC-1α protects against oxidative damage. In contrast to the increased nuclear PGC-1α, the cytosolic PGC-1α was decreased upon inhibition of GCN5 acetyltransferase. Similarly to the inhibition of GCN5 acetyltransferase, the increased nuclear PGC-1α and the decreased cytosolic PGC-1α were observed upon p38MAPK and AMPK activation. Briefly, the significantly increased nuclear PGC-1α is regulated either by inhibiting the acetylation of PGC-1α or by the phosphorylating PGC-1α, which results in a reduction in ROS.

Conclusion: PGC-1α protects neuronal cells against MPP⁺-induced toxicity partially through the acetylation of PGC-1α mediated by GCN5, and mostly through the phosphorylation PGC-1α mediated by p38MAPK or AMPK. Therapeutic reagents activating PGC-1α may be valuable for preventing mitochondrial dysfunction in PD by against oxidative damage.

Methods: With established the 1-methyl-4-phenylpyridinium (MPP⁺)-induced cell model of PD, the effects of MPP⁺ and experimental reagents on the cell viability was investigated. The expression of PGC-1α, general control of nucleotide synthesis 5 (GCN5), p38 mitogen-activated protein kinase (p38MAPK) and adenosine monophosphate activated protein kinase (AMPK) were detected by Western blotting and quantitative real-time PCR. The level of reactive oxygen species (ROS) was measured by flow cytometry. All statistical analyses were carried out using one-way ANOVA.

Integrated molecular signaling involving mitochondrial dysfunction and alteration of cell metabolism induced by tyrosine kinase inhibitors in cancer

Cancer cells have unlimited replicative potential, insensitivity to growth-inhibitory signals, evasion of apoptosis, cellular stress, and sustained angiogenesis, invasiveness and metastatic potential. Cancer cells adequately adapt cell metabolism and integrate several intracellular and redox signaling to promote cell survival in an inflammatory and hypoxic microenvironment in order to maintain/expand tumor phenotype. The administration of tyrosine kinase inhibitor (TKI) constitutes the recommended therapeutic strategy in different malignancies at advanced stages.

There are important interrelationships between cell stress, redox status, mitochondrial function, metabolism and cellular signaling pathways leading to cell survival/death. The induction of apoptosis and cell cycle arrest widely related to the antitumoral properties of TKIs result from tightly controlled events involving different cellular compartments and signaling pathways. The aim of the present review is to update the most relevant studies dealing with the impact of TKI treatment on cell function. The induction of endoplasmic reticulum (ER) stress and Ca²⁺ disturbances, leading to alteration of mitochondrial function, redox status and phosphatidylinositol 3-kinase (PI3K)-protein kinase B (Akt)-mammalian target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK) signaling pathways that involve cell metabolism reprogramming in cancer cells will be covered. Emphasis will be given to studies that identify key components of the integrated molecular pattern including receptor tyrosine kinase (RTK) downstream signaling, cell death and mitochondria-related events that appear to be involved in the resistance of cancer cells to TKI treatments.

Targeting Mitochondrial Network Architecture in Down Syndrome and Aging

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