Chronic activation of AMP kinase results in NRF-1 activation and mitochondrial biogenesis

Ampk-mediated regulation of cardiac energy metabolism: Implications for thermotolerance in Argopecten irradians irradians

AMPK is a key regulator of metabolism in eukaryotes across various pathways related to energy regulation. Although extensive investigations of AMPK have been conducted in mammals and some model organisms, research on AMPK in scallops is comparatively limited. In this study, three AMPK family genes (AiAMPKα, AiAMPKβ and AiAMPKγ) in scallop Argopecten irradians irradians were identified through genome scanning. Structure prediction and phylogenetic analyses of AiAMPKs were performed to determine their structural features and evolutionary relationships. Spatiotemporal expression patterns of AiAMPKs at different developmental stages and in healthy adult tissues were analyzed to elucidate the function of AiAMPKs in bay scallops' growth and development. The spatiotemporally specific expression of AiAMPKs implied their important roles in growth and development of bay scallops. Heat stress experiment was performed to determine the regulations of AiAMPKs in four kinds of thermosensitive tissues. Expression profiles revealed distinct molecular mechanisms of AiAMPKs in different tissues in response to heat stress: significant down-regulations in mobile hemocytes, but dominant up-regulations occurring in stationary gills, mantles and hearts. Functional verification including knock-down of AiAMPKα and inhibition of AiAMPK was separately conducted in the thermotolerant tissue heart at the post-transcription and translation levels. The thermotolerant index Arrhenius break temperature (ABT) showed a significant decrease and the rate-amplitude product (RAP) peaked earlier in the individuals after RNAi targeting AiAMPKα, displaying an earlier transition to anaerobic metabolism under heat stress, indicating an impairing ability of aerobic metabolism. After AiAMPK inhibition, widespread down-regulations of genes in key energy metabolism pathways, RNA polymerase II-mediated transcription, and aminoacyl-tRNA synthesis pathways were obviously observed, revealing the post-translational inhibition of AiAMPK hindered cardiac energy metabolism, basal transcription and translation. Overall, our findings provide evidences for exploring the molecular mechanisms of energy regulation in thermotolerant traits in bay scallops under ongoing global warming.

LncRNAs are involved in regulating ageing and age-related disease through the adenosine monophosphate-activated protein kinase signalling pathway

A long noncoding RNA (lncRNA) is longer than 200 bp. It regulates various biological processes mainly by interacting with DNA, RNA, or protein in multiple kinds of biological processes. Adenosine monophosphate-activated protein kinase (AMPK) is activated during nutrient starvation, especially glucose starvation and oxygen deficiency (hypoxia), and exposure to toxins that inhibit mitochondrial respiratory chain complex function. AMPK is an energy switch in organisms that controls cell growth and multiple cellular processes, including lipid and glucose metabolism, thereby maintaining intracellular energy homeostasis by activating catabolism and inhibiting anabolism. The AMPK signalling pathway consists of AMPK and its upstream and downstream targets. AMPK upstream targets include proteins such as the transforming growth factor β-activated kinase 1 (TAK1), liver kinase B1 (LKB1), and calcium/calmodulin-dependent protein kinase β (CaMKKβ), and its downstream targets include proteins such as the mechanistic/mammalian target of rapamycin (mTOR) complex 1 (mTORC1), hepatocyte nuclear factor 4α (HNF4α), and silencing information regulatory 1 (SIRT1). In general, proteins function relatively independently and cooperate. In this article, a review of the currently known lncRNAs involved in the AMPK signalling pathway is presented and insights into the regulatory mechanisms involved in human ageing and age-related diseases are provided.

MCT1-mediated transport of valeric acid promotes porcine preimplantation embryo development by improving mitochondrial function and inhibiting the autophagic AMPK-ULK1 pathway

Oocytes and embryos are highly sensitive to environmental stress in vivo and in vitro. During in vitro culture, many stressful conditions can affect embryo quality and viability, leading to adverse clinical outcomes such as abortion and congenital abnormalities. In this study, we found that valeric acid (VA) increased the mitochondrial membrane potential and ATP content, decreased the level of reactive oxygen species that the mitochondria generate, and thus improved mitochondrial function during early embryonic development in pigs. VA decreased expression of the autophagy-related factors LC3B and BECLIN1. Interestingly, VA inhibited expression of autophagy-associated phosphorylation-adenosine monophosphate-activated protein kinase (p-AMPK), phosphorylation-UNC-51-like autophagy-activated kinase 1 (p-ULK1, Ser555), and ATG13, which reduced apoptosis. Short-chain fatty acids (SCFAs) can signal through G-protein-coupled receptors on the cell membrane or enter the cell directly through transporters. We further show that the monocarboxylate transporter 1 (MCT1) was necessary for the effects of VA on embryo quality, which provides a new molecular perspective of the pathway by which SCFAs affect embryos. Importantly, VA significantly inhibited the AMPK-ULK1 autophagic signaling pathway through MCT1, decreased apoptosis, increased expression of embryonic pluripotency genes, and improved embryo quality.

KGF-2 ameliorates UVB-triggered skin photodamage in mice by attenuating DNA damage and inflammatory response and mitochondrial dysfunction

BACKGROUND

Long-term exposure to UVB induces DNA damage, inflammatory response, mitochondrial dysfunction, and apoptosis in skin cells, thus causing skin photodamage. Research has demonstrated the noteworthy antioxidant, anti-inflammatory, DNA repair, and mitochondrial protective properties of keratinocyte growth factor-2 (KGF-2).

METHODS

To examine the impact of KGF-2 on UVB-triggered skin photodamage in mice, hair-removed mice were initially exposed under UVB radiation and subsequently treated with KGF-2 hydrogel and repeated for 6 days. On day 7, the assessment of histopathological alterations, inflammation, DNA damage, mitochondrial function, and apoptosis in mouse skin was assessed.

RESULTS

It was found that KGF-2 could effectively relieve cutaneous photodamage symptoms and inhibit epidermal proliferation in mice. Meanwhile, KGF-2 was found to significantly reduce DNA damage, attenuate the inflammatory response, and inhibit the mitochondria-mediated intrinsic apoptotic pathway in the UVB-exposed mouse skin photodamage model.

CONCLUSION

To summarize, our results indicated that KGF-2 reduces the severity of mouse skin photodamage caused by UVB rays by attenuating DNA damage and the inflammatory response, besides inhibiting the mitochondria-mediated intrinsic apoptosis pathway.

Mitochondrial network remodeling of the diabetic heart: implications to ischemia related cardiac dysfunction

Mitochondria play a central role in cellular energy metabolism, and their dysfunction is increasingly recognized as a critical factor in the pathogenesis of diabetes-related cardiac pathophysiology, including vulnerability to ischemic events that culminate in myocardial infarction on the one hand and ventricular arrhythmias on the other. In diabetes, hyperglycemia and altered metabolic substrates lead to excessive production of reactive oxygen species (ROS) by mitochondria, initiating a cascade of oxidative stress that damages mitochondrial DNA, proteins, and lipids. This mitochondrial injury compromises the efficiency of oxidative phosphorylation, leading to impaired ATP production. The resulting energy deficit and oxidative damage contribute to functional abnormalities in cardiac cells, placing the heart at an increased risk of electromechanical dysfunction and irreversible cell death in response to ischemic insults. While cardiac mitochondria are often considered to be relatively autonomous entities in their capacity to produce energy and ROS, their highly dynamic nature within an elaborate network of closely-coupled organelles that occupies 30-40% of the cardiomyocyte volume is fundamental to their ability to exert intricate regulation over global cardiac function. In this article, we review evidence linking the dynamic properties of the mitochondrial network to overall cardiac function and its response to injury. We then highlight select studies linking mitochondrial ultrastructural alterations driven by changes in mitochondrial fission, fusion and mitophagy in promoting cardiac ischemic injury to the diabetic heart.

Lineage-specific changes in mitochondrial properties during neural stem cell differentiation

Neural stem cells (NSCs) reside in discrete regions of the adult mammalian brain where they can differentiate into neurons, astrocytes, and oligodendrocytes. Several studies suggest that mitochondria have a major role in regulating NSC fate. Here, we evaluated mitochondrial properties throughout NSC differentiation and in lineage-specific cells. For this, we used the neurosphere assay model to isolate, expand, and differentiate mouse subventricular zone postnatal NSCs. We found that the levels of proteins involved in mitochondrial fusion (Mitofusin [Mfn] 1 and Mfn 2) increased, whereas proteins involved in fission (dynamin-related protein 1 [DRP1]) decreased along differentiation. Importantly, changes in mitochondrial dynamics correlated with distinct patterns of mitochondrial morphology in each lineage. Particularly, we found that the number of branched and unbranched mitochondria increased during astroglial and neuronal differentiation, whereas the area occupied by mitochondrial structures significantly reduced with oligodendrocyte maturation. In addition, comparing the three lineages, neurons revealed to be the most energetically flexible, whereas astrocytes presented the highest ATP content. Our work identified putative mitochondrial targets to enhance lineage-directed differentiation of mouse subventricular zone-derived NSCs.

Mitochondrial dysfunction: mechanisms and advances in therapy

Mitochondria, with their intricate networks of functions and information processing, are pivotal in both health regulation and disease progression. Particularly, mitochondrial dysfunctions are identified in many common pathologies, including cardiovascular diseases, neurodegeneration, metabolic syndrome, and cancer. However, the multifaceted nature and elusive phenotypic threshold of mitochondrial dysfunction complicate our understanding of their contributions to diseases. Nonetheless, these complexities do not prevent mitochondria from being among the most important therapeutic targets. In recent years, strategies targeting mitochondrial dysfunction have continuously emerged and transitioned to clinical trials. Advanced intervention such as using healthy mitochondria to replenish or replace damaged mitochondria, has shown promise in preclinical trials of various diseases. Mitochondrial components, including mtDNA, mitochondria-located microRNA, and associated proteins can be potential therapeutic agents to augment mitochondrial function in immunometabolic diseases and tissue injuries. Here, we review current knowledge of mitochondrial pathophysiology in concrete examples of common diseases. We also summarize current strategies to treat mitochondrial dysfunction from the perspective of dietary supplements and targeted therapies, as well as the clinical translational situation of related pharmacology agents. Finally, this review discusses the innovations and potential applications of mitochondrial transplantation as an advanced and promising treatment.

Exercise-Regulated Mitochondrial and Nuclear Signalling Networks in Skeletal Muscle

Exercise perturbs energy homeostasis in skeletal muscle and engages integrated cellular signalling networks to help meet the contraction-induced increases in skeletal muscle energy and oxygen demand. Investigating exercise-associated perturbations in skeletal muscle signalling networks has uncovered novel mechanisms by which exercise stimulates skeletal muscle mitochondrial biogenesis and promotes whole-body health and fitness. While acute exercise regulates a complex network of protein post-translational modifications (e.g. phosphorylation) in skeletal muscle, previous investigations of exercise signalling in human and rodent skeletal muscle have primarily focused on a select group of exercise-regulated protein kinases [i.e. 5' adenosine monophosphate-activated protein kinase (AMPK), protein kinase A (PKA), Ca2+/calmodulin-dependent protein kinase (CaMK) and mitogen-activated protein kinase (MAPK)] and only a small subset of their respective protein substrates. Recently, global mass spectrometry-based phosphoproteomic approaches have helped unravel the extensive complexity and interconnection of exercise signalling pathways and kinases beyond this select group and phosphorylation and/or translocation of exercise-regulated mitochondrial and nuclear protein substrates. This review provides an overview of recent advances in our understanding of the molecular events associated with acute endurance exercise-regulated signalling pathways and kinases in skeletal muscle with a focus on phosphorylation. We critically appraise recent evidence highlighting the involvement of mitochondrial and nuclear protein phosphorylation and/or translocation in skeletal muscle adaptive responses to an acute bout of endurance exercise that ultimately stimulate mitochondrial biogenesis and contribute to exercise's wider health and fitness benefits.

Exercise Improves Heart Function after Myocardial Infarction: The Merits of AMPK

BACKGROUND

AMPK is considered an important protein signaling pathway that has been shown to exert prominent cardioprotective effects on the pathophysiological mechanisms of numerous diseases. Following myocardial infarction, severe impairment of cardiac function occurs, leading to complications such as heart failure and arrhythmia. Therefore, protecting the heart and improving cardiac function are important therapeutic goals after myocardial infarction. Currently, there is substantial ongoing research on exercise-centered rehabilitation training, positioning exercise training as a significant nonpharmacological approach for preventing and treating numerous cardiovascular diseases.

OBJECTIVE

Previous studies have reported that exercise can activate AMPK phosphorylation and upregulate the AMPK signaling pathway to play a cardioprotective role in coronary artery disease, but the specific mechanism involved remains to be elucidated.

CONCLUSION

This review discusses the role and mechanism of the exercise-mediated AMPK pathway in improving postinfarction cardiac function through existing studies and describes the mechanism of exercise-induced myocardial repair of AMPK from multiple perspectives to formulate a reasonable and optimal exercise rehabilitation program for the prevention and treatment of myocardial infarction patients in the clinic.

Impact of fasting on the AMPK and PGC-1α axis in rodent and human skeletal muscle: A systematic review

Based primarily on evidence from rodent models fasting is currently believed to improve metabolic health via activation of the AMPK-PGC-1α axis in skeletal muscle. However, it is unclear whether the skeletal muscle AMPK-PGC-1α axis is activated by fasting in humans. The current systematic review examined the fasting response in skeletal muscle from 34 selected studies (7 human, 21 mouse, and 6 rat). From these studies, we gathered 38 unique data points related to AMPK and 47 related to PGC-1α. In human studies, fasting mediated activation of the AMPK-PGC-1α axis is largely absent. Although evidence does support fasting-induced activation of the AMPK-PGC-1α axis in rodent skeletal muscle, the evidence is less robust than anticipated. Our findings question the ability of fasting to activate the AMPK-PGC-1α axis in human skeletal muscle and suggest that the metabolic benefits of fasting in humans are associated with caloric restriction rather than the induction of mitochondrial biogenesis. Registration: https://doi.org/10.17605/OSF.IO/KWNQY.

BIO101 stimulates myoblast differentiation and improves muscle function in adult and old mice

BACKGROUND

Muscle aging is associated with a consistent decrease in the ability of muscle tissue to regenerate following intrinsic muscle degradation, injury or overuse. Age-related imbalance of protein synthesis and degradation, mainly regulated by AKT/mTOR pathway, leads to progressive loss of muscle mass. Maintenance of anabolic and regenerative capacities of skeletal muscles may be regarded as a therapeutic option for sarcopenia and other muscle wasting diseases. Our previous studies have demonstrated that BIO101, a pharmaceutical grade 20-hydroxyecdysone, increases protein synthesis through the activation of MAS receptor involved in the protective arm of renin-angiotensin-aldosterone system. The purpose of the present study was to assess the anabolic and pro-differentiating properties of BIO101 on C2C12 muscle cells in vitro and to investigate its effects on adult and old mice models in vivo.

METHODS

The effects of BIO101 on C2C12 differentiation were assessed using myogenic transcription factors and protein expression of major kinases of AKT/mTOR pathway by Western blot. The in vivo effects of BIO101 have been investigated in BIO101 orally-treated (50 mg/kg/day) adult mice (3 months) for 28 days. To demonstrate potential beneficial effect of BIO101 treatment in a sarcopenic mouse model, we use orally treated 22-month-old C57Bl6/J mice, for 14 weeks with vehicle or BIO101. Mice body and muscle weight were recorded. Physical performances were assessed using running capacity and muscle contractility tests.

RESULTS

Anabolic properties of BIO101 were confirmed by the rapid activation of AKT/mTOR, leading to an increase of C2C12 myotubes diameters (+26%, P < 0.001). Pro-differentiating effects of BIO101 on C2C12 myoblasts were revealed by increased expression of muscle-specific differentiation transcription factors (MyoD, myogenin), resulting in increased fusion index and number of nuclei per myotube (+39% and +53%, respectively, at day 6). These effects of BIO101 were like those of angiotensin (1-7) and were abolished with the use of A779, a MAS receptor specific antagonist. Chronic BIO101 oral treatment induced AKT/mTOR activation and anabolic effects accompanied with improved physical performances in adult and old animals (maximal running distance and maximal running velocity).

CONCLUSIONS

Our data suggest beneficial anabolic and pro-differentiating effects of BIO101 rendering BIO101 a potent drug candidate for treating sarcopenia and possibly other muscle wasting disorders.

Macrophage migration inhibitory factor as a therapeutic target in neuro-oncology: A review

Primary central nervous system (CNS) tumors affect tens of thousands of patients each year, and there is a significant need for new treatments. Macrophage migration inhibitory factor (MIF) is a cytokine implicated in multiple tumorigenic processes such as cell proliferation, vascularization, and immune evasion and is therefore a promising therapeutic target in primary CNS tumors. There are several MIF-directed treatments available, including small-molecule inhibitors, peptide drugs, and monoclonal antibodies. However, only a small number of these drugs have been tested in preclinical models of primary CNS tumors, and even fewer have been studied in patients. Moreover, the brain has unique therapeutic requirements that further make effective targeting challenging. In this review, we summarize the latest functions of MIF in primary CNS tumor initiation and progression. We also discuss advances in MIF therapeutic development and ongoing preclinical studies and clinical trials. Finally, we discuss potential future MIF therapies and the strategies required for successful clinical translation.

Gynostemma Pentaphyllum Increases Exercise Performance and Alters Mitochondrial Respiration and AMPK in Healthy Males

This research aimed to determine the effects of Gynostemma pentaphyllum (G. pentaphyllum) on exercise performance, AMP-activated protein kinase (AMPK), and mitochondrial signaling in human muscle. This randomized double-blind placebo control crossover study provided placebo or 450 mg of G. pentaphyllum dried leaf extract equivalent to 2.25 g of dry leaf per day for four weeks to 16 healthy untrained young males, separated by four weeks wash-out. Following 4-week supplementation with G. pentaphyllum, participants had significantly lower leptin and blood glucose levels and improved time trial performance over 20 km, which corresponded with a higher muscle oxygen flux compared to placebo. Muscle AMPK Thr172 phosphorylation significantly increased after 60 min exercise following G. pentaphyllum supplementation. AMPK Thr172 phosphorylation levels relative to total AMPK increased earlier following exercise with G. pentaphyllum compared to placebo. Total ACC-α was lower following G. pentaphyllum supplementation compared to placebo. While further research is warranted, G. pentaphyllum supplementation improved exercise performance in healthy untrained males, which corresponded with improved mitochondrial respiration, altered AMPK and ACC, and decreased plasma leptin and glucose levels.

Transient changes to metabolic homeostasis initiate mitochondrial adaptation to endurance exercise

Endurance exercise is well established to increase mitochondrial content and function in skeletal muscle, a process termed mitochondrial biogenesis. Current understanding is that exercise initiates skeletal muscle mitochondrial remodeling via modulation of cellular nutrient, energetic and contractile stress pathways. These subtle changes in the cellular milieu are sensed by numerous transduction pathways that serve to initiate and coordinate an increase in mitochondrial gene transcription and translation. The result of these acute signaling events is the promotion of growth and assembly of mitochondria, coupled to a greater capacity for aerobic ATP provision in skeletal muscle. The aim of this review is to highlight the acute metabolic events induced by endurance exercise and the subsequent molecular pathways that sense this transient change in cellular homeostasis to drive mitochondrial adaptation and remodeling.

Microbiome and immuno-metabolic dysregulation in patients with major depressive disorder with atypical clinical presentation

Depression is highly prevalent (6% 1-year prevalence) and is the second leading cause of disability worldwide. Available treatment options for depression are far from optimal, with response rates only around 50%. This is most likely related to a heterogeneous clinical presentation of major depression disorder (MDD), suggesting different manifestations of underlying pathophysiological mechanisms. Poorer treatment outcomes to first-line antidepressants were reported in MDD patients endorsing an "atypical" symptom profile that is characterized by preserved reactivity in mood, increased appetite, hypersomnia, a heavy sensation in the limbs, and interpersonal rejection sensitivity. In recent years, evidence has emerged that immunometabolic biological dysregulation is an important underlying pathophysiological mechanism in depression, which maps more consistently to atypical features. In the last few years human microbial residents have emerged as a key influencing variable associated with immunometabolic dysregulations in depression. The microbiome plays a critical role in the training and development of key components of the host's innate and adaptive immune systems, while the immune system orchestrates the maintenance of key features of the host-microbe symbiosis. Moreover, by being a metabolically active ecosystem commensal microbes may have a huge impact on signaling pathways, involved in underlying mechanisms leading to atypical depressive symptoms. In this review, we discuss the interplay between the microbiome and immunometabolic imbalance in the context of atypical depressive symptoms. Although research in this field is in its infancy, targeting biological determinants in more homogeneous clinical presentations of MDD may offer new avenues for the development of novel therapeutic strategies for treatment-resistant depression.

A Scoping Review Investigating the "Gene-Dosage Theory" of Mitochondrial DNA in the Healthy Skeletal Muscle

This review provides an overview of the evidence regarding mtDNA and valid biomarkers for assessing mitochondrial adaptions. Mitochondria are small organelles that exist in almost all cells throughout the human body. As the only organelle, mitochondria contain their own DNA, mitochondrial DNA (mtDNA). mtDNA-encoded polypeptides are subunits of the enzyme complexes in the electron transport chain (ETC) that are responsible for production of ATP to the cells. mtDNA is frequently used as a biomarker for mitochondrial content, since changes in mitochondrial volume are thought to induce similar changes in mtDNA. However, some exercise studies have challenged this "gene-dosage theory", and have indicated that changes in mitochondrial content can adapt without changes in mtDNA. Thus, the aim of this scoping review was to summarize the studies that used mtDNA as a biomarker for mitochondrial adaptions and address the question as to whether changes in mitochondrial content, induce changes in mtDNA in response to aerobic exercise in the healthy skeletal muscle. The literature was searched in PubMed and Embase. Eligibility criteria included: interventional study design, aerobic exercise, mtDNA measurements reported pre- and postintervention for the healthy skeletal muscle and English language. Overall, 1585 studies were identified. Nine studies were included for analysis. Eight out of the nine studies showed proof of increased oxidative capacity, six found improvements in mitochondrial volume, content and/or improved mitochondrial enzyme activity and seven studies did not find evidence of change in mtDNA copy number. In conclusion, the findings imply that mitochondrial adaptions, as a response to aerobic exercise, can occur without a change in mtDNA copy number.

The Role of PGC-1α-Mediated Mitochondrial Biogenesis in Neurons

Neurons are highly dependent on mitochondrial ATP production and Ca²⁺ buffering. Neurons have unique compartmentalized anatomy and energy requirements, and each compartment requires continuously renewed mitochondria to maintain neuronal survival and activity. Peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α) is a key factor in the regulation of mitochondrial biogenesis. It is widely accepted that mitochondria are synthesized in the cell body and transported via axons to the distal end. However, axonal mitochondrial biogenesis is necessary to maintain axonal bioenergy supply and mitochondrial density due to limitations in mitochondrial axonal transport rate and mitochondrial protein lifespan. In addition, impaired mitochondrial biogenesis leading to inadequate energy supply and neuronal damage has been observed in neurological disorders. In this review, we focus on the sites where mitochondrial biogenesis occurs in neurons and the mechanisms by which it maintains axonal mitochondrial density. Finally, we summarize several neurological disorders in which mitochondrial biogenesis is affected.

Induction of lysosomal and mitochondrial biogenesis by AMPK phosphorylation of FNIP1

Cells respond to mitochondrial poisons with rapid activation of the adenosine monophosphate-activated protein kinase (AMPK), causing acute metabolic changes through phosphorylation and prolonged adaptation of metabolism through transcriptional effects. Transcription factor EB (TFEB) is a major effector of AMPK that increases expression of lysosome genes in response to energetic stress, but how AMPK activates TFEB remains unresolved. We demonstrate that AMPK directly phosphorylates five conserved serine residues in folliculin-interacting protein 1 (FNIP1), suppressing the function of the folliculin (FLCN)-FNIP1 complex. FNIP1 phosphorylation is required for AMPK to induce nuclear translocation of TFEB and TFEB-dependent increases of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) and estrogen-related receptor alpha (ERRα) messenger RNAs. Thus, mitochondrial damage triggers AMPK-FNIP1-dependent nuclear translocation of TFEB, inducing sequential waves of lysosomal and mitochondrial biogenesis.

Time-restricted feeding promotes muscle function through purine cycle and AMPK signaling in Drosophila obesity models

Obesity caused by genetic and environmental factors can lead to compromised skeletal muscle function. Time-restricted feeding (TRF) has been shown to prevent muscle function decline from obesogenic challenges; however, its mechanism remains unclear. Here we demonstrate that TRF upregulates genes involved in glycine production (Sardh and CG5955) and utilization (Gnmt), while Dgat2, involved in triglyceride synthesis is downregulated in Drosophila models of diet- and genetic-induced obesity. Muscle-specific knockdown of Gnmt, Sardh, and CG5955 lead to muscle dysfunction, ectopic lipid accumulation, and loss of TRF-mediated benefits, while knockdown of Dgat2 retains muscle function during aging and reduces ectopic lipid accumulation. Further analyses demonstrate that TRF upregulates the purine cycle in a diet-induced obesity model and AMPK signaling-associated pathways in a genetic-induced obesity model. Overall, our data suggest that TRF improves muscle function through modulations of common and distinct pathways under different obesogenic challenges and provides potential targets for obesity treatments.

Nitric oxide regulation of cellular metabolism: Adaptive tuning of cellular energy

Nitric oxide can interact with a wide range of proteins including many that are involved in metabolism. In this review we have summarized the effects of NO on glycolysis, fatty acid metabolism, the TCA cycle, and oxidative phosphorylation with reference to skeletal muscle. Low to moderate NO concentrations upregulate glucose and fatty acid oxidation, while higher NO concentrations shift cellular reliance toward a fully glycolytic phenotype. Moderate NO production directly inhibits pyruvate dehydrogenase activity, reducing glucose-derived carbon entry into the TCA cycle and subsequently increasing anaploretic reactions. NO directly inhibits aconitase activity, increasing reliance on glutamine for continued energy production. At higher or prolonged NO exposure, citrate accumulation can inhibit multiple ATP-producing pathways. Reduced TCA flux slows NADH/FADH entry into the ETC. NO can also inhibit the ETC directly, further limiting oxidative phosphorylation. Moderate NO production improves mitochondrial efficiency while improving O2 utilization increasing whole-body energy production. Long-term bioenergetic capacity may be increased because of NO-derived ROS, which participate in adaptive cellular redox signaling through AMPK, PCG1-α, HIF-1, and NF-κB. However, prolonged exposure or high concentrations of NO can result in membrane depolarization and opening of the MPT. In this way NO may serve as a biochemical rheostat matching energy supply with demand for optimal respiratory function.

Nutrient-sensing mTORC1 and AMPK pathways in chronic kidney diseases

Nutrients such as glucose, amino acids and lipids are fundamental sources for the maintenance of essential cellular processes and homeostasis in all organisms. The nutrient-sensing kinases mechanistic target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK) are expressed in many cell types and have key roles in the control of cell growth, proliferation, differentiation, metabolism and survival, ultimately contributing to the physiological development and functions of various organs, including the kidney. Dysregulation of these kinases leads to many human health problems, including cancer, neurodegenerative diseases, metabolic disorders and kidney diseases. In the kidney, physiological levels of mTOR and AMPK activity are required to support kidney cell growth and differentiation and to maintain kidney cell integrity and normal nephron function, including transport of electrolytes, water and glucose. mTOR forms two functional multi-protein kinase complexes, mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2). Hyperactivation of mTORC1 leads to podocyte and tubular cell dysfunction and vulnerability to injury, thereby contributing to the development of chronic kidney diseases, including diabetic kidney disease, obesity-related kidney disease and polycystic kidney disease. Emerging evidence suggests that targeting mTOR and/or AMPK could be an effective therapeutic approach to controlling or preventing these diseases.

The Crosstalk between Microbiome and Mitochondrial Homeostasis in Neurodegeneration

Mitochondria are highly dynamic organelles that serve as the primary cellular energy-generating system. Apart from ATP production, they are essential for many biological processes, including calcium homeostasis, lipid biogenesis, ROS regulation and programmed cell death, which collectively render them invaluable for neuronal integrity and function. Emerging evidence indicates that mitochondrial dysfunction and altered mitochondrial dynamics are crucial hallmarks of a wide variety of neurodevelopmental and neurodegenerative conditions. At the same time, the gut microbiome has been implicated in the pathogenesis of several neurodegenerative disorders due to the bidirectional communication between the gut and the central nervous system, known as the gut-brain axis. Here we summarize new insights into the complex interplay between mitochondria, gut microbiota and neurodegeneration, and we refer to animal models that could elucidate the underlying mechanisms, as well as novel interventions to tackle age-related neurodegenerative conditions, based on this intricate network.

Alpha-SNAP (M105I) mutation promotes neuronal differentiation of neural stem/progenitor cells through overactivation of AMPK

Background: The M105I point mutation in α-SNAP (Soluble N-ethylmaleimide-sensitive factor attachment protein-alpha) leads in mice to a complex phenotype known as hyh (hydrocephalus with hop gait), characterized by cortical malformation and hydrocephalus, among other neuropathological features. Studies performed by our laboratory and others support that the hyh phenotype is triggered by a primary alteration in embryonic neural stem/progenitor cells (NSPCs) that leads to a disruption of the ventricular and subventricular zones (VZ/SVZ) during the neurogenic period. Besides the canonical role of α-SNAP in SNARE-mediated intracellular membrane fusion dynamics, it also negatively modulates AMP-activated protein kinase (AMPK) activity. AMPK is a conserved metabolic sensor associated with the proliferation/differentiation balance in NSPCs. Methods: Brain samples from hyh mutant mice (hydrocephalus with hop gait) (B6C3Fe-a/a-Napahyh/J) were analyzed by light microscopy, immunofluorescence, and Western blot at different developmental stages. In addition, NSPCs derived from WT and hyh mutant mice were cultured as neurospheres for in vitro characterization and pharmacological assays. BrdU labeling was used to assess proliferative activity in situ and in vitro. Pharmacological modulation of AMPK was performed using Compound C (AMPK inhibitor) and AICAR (AMPK activator). Results: α-SNAP was preferentially expressed in the brain, showing variations in the levels of α-SNAP protein in different brain regions and developmental stages. NSPCs from hyh mice (hyh-NSPCs) displayed reduced levels of α-SNAP and increased levels of phosphorylated AMPKα (pAMPKα^Thr172), which were associated with a reduction in their proliferative activity and a preferential commitment with the neuronal lineage. Interestingly, pharmacological inhibition of AMPK in hyh-NSPCs increased proliferative activity and completely abolished the increased generation of neurons. Conversely, AICAR-mediated activation of AMPK in WT-NSPCs reduced proliferation and boosted neuronal differentiation. Discussion: Our findings support that α-SNAP regulates AMPK signaling in NSPCs, further modulating their neurogenic capacity. The naturally occurring M105I mutation of α-SNAP provokes an AMPK overactivation in NSPCs, thus connecting the α-SNAP/AMPK axis with the etiopathogenesis and neuropathology of the hyh phenotype.

Alpha-Lipoic Acid and Glucose Metabolism: A Comprehensive Update on Biochemical and Therapeutic Features

Alpha-lipoic acid (ALA) is a natural compound with antioxidant and pro-oxidant properties which has effects on the regulation of insulin sensitivity and insulin secretion. ALA is widely prescribed in patients with diabetic polyneuropathy due to its positive effects on nerve conduction and alleviation of symptoms. It is, moreover, also prescribed in other insulin resistance conditions such as metabolic syndrome (SM), polycystic ovary syndrome (PCOS) and obesity. However, several cases of Insulin Autoimmune Syndrome (IAS) have been reported in subjects taking ALA. The aim of the present review is to describe the main chemical and biological functions of ALA in glucose metabolism, focusing on its antioxidant activity, its role in modulating insulin sensitivity and secretion and in symptomatic peripheral diabetic polyneuropathy. We also provide a potential explanation for increased risk for the development of IAS.

Cryptotanshinone protects skin cells from ultraviolet radiation-induced photoaging via its antioxidant effect and by reducing mitochondrial dysfunction and inhibiting apoptosis

The integrity of skin tissue structure and function plays an important role in maintaining skin rejuvenation. Ultraviolet (UV) radiation is the main environmental factor that causes skin aging through photodamage of the skin tissue. Cryptotanshinone (CTS), an active ingredient mianly derived from the Salvia plants of Lamiaceae, has many pharmacological effects, such as anti-inflammatory, antioxidant, and anti-tumor effects. In this study, we showed that CTS could ameliorate the photodamage induced by UV radiation in epidermal keratinocytes (HaCaT) and dermal fibroblasts (HFF-1) when applied to the cells before exposure to the radiation, effectively delaying the aging of the cells. CTS exerted its antiaging effect by reducing the level of reactive oxygen species (ROS) in the cells, attenuating DNA damage, activating the nuclear factor E2-related factor 2 (Nrf2) signaling pathway, and reduced mitochondrial dysfunction as well as inhibiting apoptosis. Further, CTS could promote mitochondrial biosynthesis in skin cells by activating the AMP-activated protein kinase (AMPK)/sirtuin-1 (SIRT1)/peroxisome proliferator-activated receptor-γ co-activator-1α (PGC-1α) signaling pathway. These findings demonstrated the protective effects of CTS against UV radiation-induced skin photoaging and provided a theoretical and experimental basis for the application of CTS as an anti-photodamage and anti-aging agent for the skin.

Role of AMPK/mTOR, mitochondria, and ROS in the pathogenesis of endometriosis

Endometriosis is the presence of endometrial tissue outside the uterine cavity usually in the ovaries, fallopian tube, and pelvic cavity. It's a chronic enigmatic gynecological condition associated with dysmenorrhea, dyspareunia, pelvic pain, and infertility. Endometriosis lesions exist in a unique microenvironment characterized by increased concentrations of hormones, inflammation, and oxidative stress. This environment promotes cell survival through the binding of membrane receptors and subsequent cascading activation of intracellular kinases that stimulate a cellular response. In endometriosis, well-established signaling pathways, mTOR and AMPK, are altered via steroid hormones and other factors to promote cell growth, migration, and proliferation. This is accompanied by dysfunction in the mitochondria that increase energy production to sustain proliferation demands consequently leading to reactive oxygen species overproduction. This review aims to summarize the role of altered mTOR/AMPK signaling pathway, mitochondrial dysfunction, and reactive oxygen species overproduction along with providing therapeutic and diagnostic approaches. Highlighting these factors would provide a better understanding to reach a coherent theory for the pathogenesis of endometriosis.

Impact of Roux-en-Y Gastric Bypass on Mitochondrial Biogenesis and Dynamics in Leukocytes of Obese Women

The chronic low-grade inflammation widely associated with obesity can lead to a prooxidant status that triggers mitochondrial dysfunction. To date, Roux-en-Y gastric bypass (RYGB) is considered the most effective strategy for obese patients. However, little is known about its molecular mechanisms. This interventional study aimed to investigate whether RYGB modulates oxidative stress, inflammation and mitochondrial dynamics in the leukocytes of 47 obese women at one year follow-up. We evaluated biochemical parameters and serum inflammatory cytokines -TNFα, IL6 and IL1β- to assess systemic status. Total superoxide production -dHe-, mitochondrial membrane potential -TMRM-, leucocyte protein expression of inflammation mediators -MCP1 and NF-kB-, antioxidant defence -GPX1-, mitochondrial regulation—PGC1α, TFAM, OXPHOS and MIEAP- and dynamics -MFN2, MNF1, OPA1, FIS1 and p-DRP1- were also determined. After RYGB, a significant reduction in superoxide and mitochondrial membrane potential was evident, while GPX1 content was significantly increased. Likewise, a marked upregulation of the transcription factors PGC1α and TFAM, complexes of the oxidative phosphorylation chain (I–V) and MIEAP and MFN1 was observed. We conclude that women undergoing RYGB benefit from an amelioration of their prooxidant and inflammatory status and an improvement in mitochondrial dynamics of their leukocytes, which is likely to have a positive effect on clinical outcome.

NRF1-mediated microglial activation triggers high-altitude cerebral edema

High-altitude cerebral edema (HACE) is a potentially fatal encephalopathy associated with a time-dependent exposure to the hypobaric hypoxia of altitude. The formation of HACE is affected by both vasogenic and cytotoxic edema. The over-activated microglia potentiate the damage of blood-brain barrier (BBB) and exacerbate cytotoxic edema. In light with the activation of microglia in HACE, we aimed to investigate whether the over-activated microglia were the key turning point of acute mountain sickness to HACE. In in vivo experiments, by exposing mice to hypobaric hypoxia (7000 m above sea level) to induce HACE model, we found that microglia were activated and migrated to blood vessels. Microglia depletion by PLX5622 obviously relieved brain edema. In in vitro experiments, we found that hypoxia induced cultured microglial activation, leading to the destruction of endothelial tight junction and astrocyte swelling. Up-regulated nuclear respiratory factor 1 (NRF1) accelerated pro-inflammatory factors through transcriptional regulation on nuclear factor kappa B p65 (NF-κB p65) and mitochondrial transcription factor A (TFAM) in activated microglia under hypoxia. NRF1 also up-regulated phagocytosis by transcriptional regulation on caveolin-1 (CAV-1) and adaptor-related protein complex 2 subunit beta (AP2B1). The present study reveals a new mechanism in HACE: hypoxia over-activates microglia through up-regulation of NRF1, which both induces inflammatory response through transcriptionally activating NF-κB p65 and TFAM, and enhances phagocytic function through up-regulation of CAV-1 and AP2B1; hypoxia-activated microglia destroy the integrity of BBB and release pro-inflammatory factors that eventually induce HACE.

Roles of mTOR in the Regulation of Pancreatic β-Cell Mass and Insulin Secretion

Pancreatic β-cells are the only type of cells that can control glycemic levels via insulin secretion. Thus, to explore the mechanisms underlying pancreatic β-cell failure, many reports have clarified the roles of important molecules, such as the mechanistic target of rapamycin (mTOR), which is a central regulator of metabolic and nutrient cues. Studies have uncovered the roles of mTOR in the function of β-cells and the progression of diabetes, and they suggest that mTOR has both positive and negative effects on pancreatic β-cells in the development of diabetes.

AMPK Activation Is Indispensable for the Protective Effects of Caloric Restriction on Left Ventricular Function in Postinfarct Myocardium

Background: Caloric restriction (CR) extends lifespan in many species, including mammals. CR is cardioprotective in senescent myocardium by correcting pre-existing mitochondrial dysfunction and apoptotic activation. Furthermore, it confers cardioprotection against acute ischemia-reperfusion injury. Here, we investigated the role of AMP-activated protein kinase (AMPK) in mediating the cardioprotective CR effects in failing, postinfarct myocardium. Methods: Ligation of the left coronary artery or sham operation was performed in rats and mice. Four weeks after surgery, left ventricular (LV) function was analyzed by echocardiography, and animals were assigned to different feeding groups (control diet or 40% CR, 8 weeks) as matched pairs. The role of AMPK was investigated with an AMPK inhibitor in rats or the use of alpha 2 AMPK knock-out mice. Results: CR resulted in a significant improvement in LV function, compared to postinfarct animals receiving control diet in both species. The improvement in LV function was accompanied by a reduction in serum BNP, decrease in LV proapoptotic activation, and increase in mitochondrial biogenesis in the LV. Inhibition or loss of AMPK prevented most of these changes. Conclusions: The failing, postischemic heart is protected from progressive loss of LV systolic function by CR. AMPK activation is indispensable for these protective effects.

Nuclear-Mitochondrial Interactions

Mitochondria, the cell’s major energy producers, also act as signaling hubs, interacting with other organelles both directly and indirectly. Despite having its own circular genome, the majority of mitochondrial proteins are encoded by nuclear DNA. To respond to changes in cell physiology, the mitochondria must send signals to the nucleus, which can, in turn, upregulate gene expression to alter metabolism or initiate a stress response. This is known as retrograde signaling. A variety of stimuli and pathways fall under the retrograde signaling umbrella. Mitochondrial dysfunction has already been shown to have severe implications for human health. Disruption of retrograde signaling, whether directly associated with mitochondrial dysfunction or cellular environmental changes, may also contribute to pathological deficits. In this review, we discuss known signaling pathways between the mitochondria and the nucleus, examine the possibility of direct contacts, and identify pathological consequences of an altered relationship.

Intertwined Relationship of Mitochondrial Metabolism, Gut Microbiome and Exercise Potential

The microbiome has emerged as a key player contributing significantly to the human physiology over the past decades. The potential microbial niche is largely unexplored in the context of exercise enhancing capacity and the related mitochondrial functions. Physical exercise can influence the gut microbiota composition and diversity, whereas a sedentary lifestyle in association with dysbiosis can lead to reduced well-being and diseases. Here, we have elucidated the importance of diverse microbiota, which is associated with an individual's fitness, and moreover, its connection with the organelle, the mitochondria, which is the hub of energy production, signaling, and cellular homeostasis. Microbial by-products, such as short-chain fatty acids, are produced during regular exercise that can enhance the mitochondrial capacity. Therefore, exercise can be employed as a therapeutic intervention to circumvent or subside various metabolic and mitochondria-related diseases. Alternatively, the microbiome-mitochondria axis can be targeted to enhance exercise performance. This review furthers our understanding about the influence of microbiome on the functional capacity of the mitochondria and exercise performance, and the interplay between them.

Mitochondrial Quality Control in Sarcopenia: Updated Overview of Mechanisms and Interventions

Sarcopenia is a common geriatric disorder characterized by decreased muscle strength, low muscle mass and poor physical performance. This aging-related skeletal muscle deterioration leads to adverse outcomes and severely impairs the quality of life of patients. The accumulation of dysfunctional mitochondria with aging is an important factor in the occurrence and progression of sarcopenia. Mitochondrial quality control (MQC) fundamentally ensures the normal mitochondrial functions and is comprised of four main parts: proteostasis, biogenesis, dynamics and autophagy. Therefore, any pathophysiologic factors compromising the quality control of homeostasis in the skeletal muscle may lead to sarcopenia. However, the specific theoretical aspects of these processes have not been fully elucidated. Current therapeutic interventions using nutritional and pharmaceutical treatments show a modest therapeutic efficacy; however, only physical exercise is recommended as the first-line therapy for sarcopenia, which can ameliorate skeletal muscle deficiency by maintaining the homeostatic MQC. In this review, we summarized the known mechanisms that contribute to the pathogenesis of sarcopenia by impairing normal mitochondrial functions and described potential interventions that mitigate sarcopenia through improving MQC.

Mitochondrial Biogenesis in Neurons: How and Where

Neurons rely mostly on mitochondria for the production of ATP and Ca²⁺ homeostasis. As sub-compartmentalized cells, they have different pools of mitochondria in each compartment that are maintained by a constant mitochondrial turnover. It is assumed that most mitochondria are generated in the cell body and then travel to the synapse to exert their functions. Once damaged, mitochondria have to travel back to the cell body for degradation. However, in long cells, like motor neurons, this constant travel back and forth is not an energetically favourable process, thus mitochondrial biogenesis must also occur at the periphery. Ca²⁺ and ATP levels are the main triggers for mitochondrial biogenesis in the cell body, in a mechanism dependent on the Peroxisome-proliferator-activated γ co-activator-1α-nuclear respiration factors 1 and 2-mitochondrial transcription factor A (PGC-1α-NRF-1/2-TFAM) pathway. However, even though of extreme importance, very little is known about the mechanisms promoting mitochondrial biogenesis away from the cell body. In this review, we bring forward the evoked mechanisms that are at play for mitochondrial biogenesis in the cell body and periphery. Moreover, we postulate that mitochondrial biogenesis may vary locally within the same neuron, and we build upon the hypotheses that, in the periphery, local protein synthesis is responsible for giving all the machinery required for mitochondria to replicate themselves.

Chronic Activation of AMPK Induces Mitochondrial Biogenesis through Differential Phosphorylation and Abundance of Mitochondrial Proteins in Dictyostelium discoideum

Mitochondrial biogenesis is a highly controlled process that depends on diverse signalling pathways responding to cellular and environmental signals. AMP-activated protein kinase (AMPK) is a critical metabolic enzyme that acts at a central control point in cellular energy homeostasis. Numerous studies have revealed the crucial roles of AMPK in the regulation of mitochondrial biogenesis; however, molecular mechanisms underlying this process are still largely unknown. Previously, we have shown that, in cellular slime mould Dictyostelium discoideum, the overexpression of the catalytic α subunit of AMPK led to enhanced mitochondrial biogenesis, which was accompanied by reduced cell growth and aberrant development. Here, we applied mass spectrometry-based proteomics of Dictyostelium mitochondria to determine the impact of chronically active AMPKα on the phosphorylation state and abundance of mitochondrial proteins and to identify potential protein targets leading to the biogenesis of mitochondria. Our results demonstrate that enhanced mitochondrial biogenesis is associated with variations in the phosphorylation levels and abundance of proteins related to energy metabolism, protein synthesis, transport, inner membrane biogenesis, and cellular signalling. The observed changes are accompanied by elevated mitochondrial respiratory activity in the AMPK overexpression strain. Our work is the first study reporting on the global phosphoproteome profiling of D. discoideum mitochondria and its changes as a response to constitutively active AMPK. We also propose an interplay between the AMPK and mTORC1 signalling pathways in controlling the cellular growth and biogenesis of mitochondria in Dictyostelium as a model organism.

AMPK: restoring metabolic homeostasis over space and time

The evolution of AMPK and its homologs enabled exquisite responsivity and control of cellular energetic homeostasis. Recent work has been critical in establishing the mechanisms that determine AMPK activity, novel targets of AMPK action, and the distribution of AMPK-mediated control networks across the cellular landscape. The role of AMPK as a hub of metabolic control has led to intense interest in pharmacologic activation as a therapeutic avenue for a number of disease states, including obesity, diabetes, and cancer. As such, critical work on the compartmentalization of AMPK, its downstream targets, and the systems it influences has progressed in recent years. The variegated distribution of AMPK-mediated control of metabolic homeostasis has revealed key insights into AMPK in normal biology and future directions for AMPK-based therapeutic strategies.

Periplaneta americana extract ameliorates lipopolysaccharide-induced liver injury by improving mitochondrial dysfunction via the AMPK/PGC-1α signaling pathway

Periplaneta americana (PA) extract acts clinically as a therapeutic treatment in various diseases; it enhances liver function in mouse models and mitigates the pathological condition of liver fibrosis. The present study aimed to investigate the role and potential mechanisms underlying the action of the PA extract, xinmailong (XML), in lipopolysaccharide (LPS)-induced liver injury. Following the treatment of AML12 cells with LPS, the content of cytochrome c in the cytoplasm and mitochondria, and the level of ATP synthesis were detected using corresponding kits. The relative mRNA expression levels of nuclear respiratory factor 1 and transcription factor A, mitochondrial were investigated using reverse transcription-quantitative (RT-q)PCR analysis. The MTT assay was performed to detect the viability of AML12 cells following treatment with XML, in the absence or presence of LPS. Western blot analysis was performed to determine the expression levels of proteins in the AMP-activated protein kinase (AMPK)/proliferator-activated receptor γ coactivator-1α (PGC-1α) pathway. Following treatment with compound C, an inhibitor of AMPK, the expression levels of inflammatory cytokines were determined using ELISA and RT-qPCR analysis. The levels of oxidative stress-related markers were detected using corresponding kits following treatment with compound C. In addition, TUNEL staining was performed to detect the apoptosis of AML12 cells, and western blot analysis was performed to investigate the expression levels of apoptosis-related proteins. Mitochondrial dysfunction was induced by LPS in AML12 cells. LPS stimulation significantly downregulated the expression of proteins in the AMPK/PGC-1α pathway, which was reversed following treatment with XML. In addition, inflammation, oxidative stress and mitochondrial dysfunction induced by LPS were alleviated by XML in AML12 cells. However, the addition of compound C and XML to LPS-induced AML12 cells resulted in the aggravation of cell injury. Collectively, the results of the present study indicated that XML suppressed mitochondrial dysfunction induced by LPS by activating AMPK/PGC-1α signaling. Thus, the results of the present study may contribute to further understanding of the underlying mechanism via which XML alleviates liver injury.

Valproate activates the Snf1 kinase in Saccharomyces cerevisiae by decreasing the cytosolic pH

Valproate (VPA) is a widely used mood stabilizer, but its therapeutic mechanism of action is not understood. This knowledge gap hinders the development of more effective drugs with fewer side effects. Using the yeast model to elucidate the effects of VPA on cellular metabolism, we determined that the drug upregulated expression of genes normally repressed during logarithmic growth on glucose medium and increased levels of activated (phosphorylated) Snf1 kinase, the major metabolic regulator of these genes. VPA also decreased the cytosolic pH (pH_c) and reduced glycolytic production of 2/3-phosphoglycerate. ATP levels and mitochondrial membrane potential were increased, and glucose-mediated extracellular acidification decreased in the presence of the drug, as indicated by a smaller glucose-induced shift in pH, suggesting that the major P-type proton pump Pma1 was inhibited. Interestingly, decreasing the pH_c by omeprazole-mediated inhibition of Pma1 led to Snf1 activation. We propose a model whereby VPA lowers the pH_c causing a decrease in glycolytic flux. In response, Pma1 is inhibited and Snf1 is activated, resulting in increased expression of normally repressed metabolic genes. These findings suggest a central role for pH_c in regulating the metabolic program of yeast cells.

Hypoglycemic activity of puerarin through modulation of oxidative stress and mitochondrial function via AMPK

Hyperglycemia is the dominant phenotype of diabetes and the main contributor of diabetic complications. Puerarin is widely used in cardiovascular diseases and diabetic vascular complications. However, little is known about its direct effects on diabetes. The aim of our study is to investigate its antidiabetic effect in vivo and in vitro, and explore the underlying mechanism. We used type I diabetic mice induced by streptozotocin to observe the effects of puerarin on glucose metabolism. In addition, oxidative stress and hepatic mitochondrial respiratory activity were evaluated in type I diabetic mice. In vitro, glucose consumption in HepG2 cells was assayed along with the qPCR detection of glucogenesis genes expression. Moreover, ATP production was examined and phosphorylation of AMPK was determined using Western blot. Finally, the molecular docking was performed to predict the potential interaction of puerarin with AMPK utilizing program LibDock of Discovery Studio 2018 software. The results showed that puerarin improved HepG2 glucose consumption and upregulated the glucogenesis related genes expression. Also, puerarin lowered fasting and fed blood glucose with improvement of glucose tolerance in type I diabetic mice. Further mechanism investigation showed that puerarin suppressed oxidative stress and improved hepatic mitochondrial respiratory function with enhancing ATP production and activating phosphorylation of AMPK. Docking study showed that puerarin interacted with AMPK activate site and enhancing phosphorylation. Taken together, these findings indicated that puerarin exhibited the hypoglycemic effect through attenuating oxidative stress and improving mitochondrial function via AMPK regulation, which may serve as a potential therapeutic option for diabetes treatment.

The effect of SiNPs on DNA methylation of genome in mouse spermatocytes

Silica nanoparticles (SiNPs), which are the main inorganic components of atmospheric particulate matter, have been proved to have certain male reproductive toxicity in previous studies. Spermatogenesis involves complex epigenetic regulation, but it is still unclear if SiNPs exposure will interfere with the DNA methylation patterns in mouse spermatocytes. The present study was designed to investigate the effects of SiNPs on DNA methylation in the mouse spermatocyte GC-2spd(ts). GC-2 cells were treated with 0 and 20 μg/mL SiNPs for 24 h. MeDIP-seq assay was then performed to analyze the differentially methylated genes related to spermatogenesis. The results showed that SiNPs induced extensive methylation changes in the genome of GC-2 cells, and 24a total of 428 hyper-methylated genes and 398 hypo-methylated genes were identified. Gene Ontology and pathway analysis showed that differential DNA methylation induced by SiNPs was probably involved with abnormal transcription and translation, mitochondrial damage, and cell apoptosis. Results from qRT-PCR verification showed that the expression of spermatogenesis-related genes Akap1, Crem, Spz1, and Tex11 were dysregulated by SiNPs exposure, which was consistent with the MeDIP-seq assay. In general, this study suggested that SiNPs caused genome-wide DNA methylation changes in GC-2 cells, providing valuable reference for the future epigenetic studies in SiNPs-induced male reproductive toxicity.

Deletion of the diabetes candidate gene Slc16a13 in mice attenuates diet-induced ectopic lipid accumulation and insulin resistance

Genome-wide association studies have identified SLC16A13 as a novel susceptibility gene for type 2 diabetes. The SLC16A13 gene encodes SLC16A13/MCT13, a member of the solute carrier 16 family of monocarboxylate transporters. Despite its potential importance to diabetes development, the physiological function of SLC16A13 is unknown. Here, we validate Slc16a13 as a lactate transporter expressed at the plasma membrane and report on the effect of Slc16a13 deletion in a mouse model. We show that Slc16a13 increases mitochondrial respiration in the liver, leading to reduced hepatic lipid accumulation and increased hepatic insulin sensitivity in high-fat diet fed Slc16a13 knockout mice. We propose a mechanism for improved hepatic insulin sensitivity in the context of Slc16a13 deficiency in which reduced intrahepatocellular lactate availability drives increased AMPK activation and increased mitochondrial respiration, while reducing hepatic lipid content. Slc16a13 deficiency thereby attenuates hepatic diacylglycerol-PKCε mediated insulin resistance in obese mice. Together, these data suggest that SLC16A13 is a potential target for the treatment of type 2 diabetes and non-alcoholic fatty liver disease.

AMPK and Pulmonary Hypertension: Crossroads Between Vasoconstriction and Vascular Remodeling

Pulmonary hypertension (PH) is a debilitating and life-threatening disease characterized by increased blood pressure within the pulmonary arteries. Adenosine monophosphate-activated protein kinase (AMPK) is a heterotrimeric serine-threonine kinase that contributes to the regulation of metabolic and redox signaling pathways. It has key roles in the regulation of cell survival and proliferation. The role of AMPK in PH is controversial because both inhibition and activation of AMPK are preventive against PH development. Some clinical studies found that metformin, the first-line antidiabetic drug and the canonical AMPK activator, has therapeutic efficacy during treatment of early-stage PH. Other study findings suggest the use of metformin is preferentially beneficial for treatment of PH associated with heart failure with preserved ejection fraction (PH-HFpEF). In this review, we discuss the "AMPK paradox" and highlight the differential effects of AMPK on pulmonary vasoconstriction and pulmonary vascular remodeling. We also review the effects of AMPK activators and inhibitors on rescue of preexisting PH in animals and include a discussion of gender differences in the response to metformin in PH.

Physical Exercise: A Novel Tool to Protect Mitochondrial Health

Mitochondrial dysfunction is a crucial contributor to heart diseases. Alterations in energetic metabolism affect crucial homeostatic processes, such asATP production, the generation of reactive oxygen species, and the release of pro-apoptotic factors, associated with metabolic abnormalities. In response to energetic deficiency, the cardiomyocytes activate the Mitochondrial Quality Control (MQC), a critical process in maintaining mitochondrial health. This process is compromised in cardiovascular diseases depending on the pathology's severity and represents, therefore, a potential therapeutic target. Several potential targeting molecules within this process have been identified in the last years, and therapeutic strategies have been proposed to ameliorate mitochondria monitoring and function. In this context, physical exercise is considered a non-pharmacological strategy to protect mitochondrial health. Physical exercise regulates MQC allowing the repair/elimination of damaged mitochondria and synthesizing new ones, thus recovering the metabolic state. In this review, we will deal with the effect of physical exercise on cardiac mitochondrial function tracing its ability to modulate specific steps in MQC both in physiologic and pathologic conditions.

Molecular regulation of skeletal muscle mitochondrial biogenesis following blood flow-restricted aerobic exercise: a call to action

Blood flow-restricted (BFR) exercise can induce training adaptations comparable to those observed following training in free flow conditions. However, little is known about the acute responses within skeletal muscle following BFR aerobic exercise (AE). Moreover, although preliminary evidence suggests chronic BFR AE may augment certain training adaptations in skeletal muscle mitochondria more than non-BFR AE, the underlying mechanisms are poorly understood. In this review, we summarise the acute BFR AE literature examining mitochondrial biogenic signalling pathways and provide insight into mechanisms linked to skeletal muscle remodelling following BFR AE. Specifically, we focus on signalling pathways potentially contributing to augmented peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) mRNA following work-rate-matched BFR AE compared with non-BFR AE. We present evidence suggesting reductions in muscle oxygenation during acute BFR AE lead to increased intracellular energetic stress, AMP-activated protein kinase (AMPK) activation and PGC-1α mRNA. In addition, we briefly discuss mitochondrial adaptations to BFR aerobic training, and we assess the risk of bias using the Cochrane Collaboration risk of bias assessment tool. We ultimately call for several straightforward modifications to help minimise bias in future BFR AE studies.

AKT2 regulates development and metabolic homeostasis via AMPK-depedent pathway in skeletal muscle

Skeletal muscle is responsible for the majority of glucose disposal in the body. Insulin resistance in the skeletal muscle accounts for 85-90% of the impairment of total glucose disposal in patients with type 2 diabetes (T2D). However, the mechanism remains controversial. The present study aims to investigate whether AKT2 deficiency causes deficits in skeletal muscle development and metabolism, we analyzed the expression of molecules related to skeletal muscle development, glucose uptake and metabolism in mice of 3- and 8-months old. We found that AMP-activated protein kinase (AMPK) phosphorylation and myocyte enhancer factor 2 (MEF2) A (MEF2A) expression were down-regulated in AKT2 knockout (KO) mice, which can be inverted by AMPK activation. We also observed reduced mitochondrial DNA (mtDNA) abundance and reduced expression of genes involved in mitochondrial biogenesis in the skeletal muscle of AKT2 KO mice, which was prevented by AMPK activation. Moreover, AKT2 KO mice exhibited impaired AMPK signaling in response to insulin stimulation compared with WT mice. Our study establishes a new and important function of AKT2 in regulating skeletal muscle development and glucose metabolism via AMPK-dependent signaling.

Activation of AMPK Promotes Maturation of Cardiomyocytes Derived From Human Induced Pluripotent Stem Cells

Human induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CMs) (hiPSC-CMs) are a promising cell source for disease modeling, myocardial regeneration, and drug assessment. However, hiPSC-CMs have certain immature fetal CM-like properties that are different from the characteristics of adult CMs in several aspects, including cellular structure, mitochondrial function, and metabolism, thus limiting their applications. Adenosine 5‘-monophosphate (AMP)-activated protein kinase (AMPK) is an energy-sensing protein kinase involved in the regulation of fatty acid oxidation and mitochondrial biogenesis in cardiomyocytes. This study investigated the effects of AMPK on the maturation of hiPSC-CMs. Activation of AMPK in hiPSC-CMs significantly increased the expression of CM-specific markers and resulted in a more mature myocardial structure compared to that in the control cells. We found that activation of AMPK improved mitochondrial oxidative phosphorylation (OxPhos) and the oxygen consumption rate (OCR). Additionally, our data demonstrated that activation of AMPK increased mitochondrial fusion to promote the maturation of mitochondrial structure and function. Overall, activation of AMPK is an effective approach to promote hiPSC-CMs maturation, which may enhance the utility of hiPSC-CMs in clinical applications.

[The effect of L-carnitine depletion induced by long-term therapy of mice with meldonium on brain mitochondrial balance]

Meldonium is a metabolic drug used for treatment of coronary heart disease. The effect of the drug lies in its ability to inhibit synthesis and transport of L-carnitine. At the same time, a long-term deficiency of L-carnitine can theoretically negatively affect the activity of the transcription factor Nrf2, which is extremely important for maintaining mitochondrial balance in cells. We have shown that meldonium therapy for 3 months at a dose of 100 mg/kg in mice causes a decrease in the expression of the Nrf2 gene in the brain. A decrease in the Nrf2 level causes suppression of mitochondrial biogenesis, which is manifested in a decrease in the level of mtDNA and the level of Cox1 expression. However, no negative effect of meldonium on the bioenergetics parameters of mitochondria was found, as evidenced by the maintenance of a stable mitochondrial potential and the level of production of reactive oxygen species. Jne mohth after the end of the meldonium therapy, expression of the genes responsible for mitochondrial biogenesis and mitophagy (p62, Pink1, Tfam) was observed and the expression level of genes responsible for mitochondrial fusion returned to control values. These changes may be associated with the normalization of the level of L-carnitine in brain cells.

Ammonium chloride administration prior to exercise has muscle-specific effects on mitochondrial and myofibrillar protein synthesis in rats

AIM

Exercise is able to increase both muscle protein synthesis and mitochondrial biogenesis. However, acidosis, which can occur in pathological states as well as during high-intensity exercise, can decrease mitochondrial function, whilst its impact on muscle protein synthesis is disputed. Thus, the aim of this study was to determine the effect of a mild physiological decrease in pH, by administration of ammonium chloride, on myofibrillar and mitochondrial protein synthesis, as well as associated molecular signaling events.

METHODS

Male Wistar rats were given either a placebo or ammonium chloride prior to a short interval training session. Rats were killed before exercise, immediately after exercise, or 3 h after exercise.

RESULTS

Myofibrillar (p = 0.036) fractional protein synthesis rates was increased immediately after exercise in the soleus muscle of the placebo group, but this effect was absent in the ammonium chloride group. However, in the gastrocnemius muscle NH4 Cl increased myofibrillar (p = 0.044) and mitochondrial protein synthesis (0 h after exercise p = 0.01; 3 h after exercise p = 0.003). This was accompanied by some small differences in protein phosphorylation and mRNA expression.

CONCLUSION

This study found ammonium chloride administration immediately prior to a single session of exercise in rats had differing effects on mitochondrial and myofibrillar protein synthesis rates in soleus (type I) and gastrocnemius (type II) muscle in rats.