TAZ links exercise to mitochondrial biogenesis via mitochondrial transcription factor A

Free essential amino acid feeding improves endurance during resistance training via DRP1-dependent mitochondrial remodelling

BACKGROUND

Loss of muscle strength and endurance with aging or in various conditions negatively affects quality of life. Resistance exercise training (RET) is the most powerful means to improve muscle mass and strength, but it does not generally lead to improvements in endurance capacity. Free essential amino acids (EAAs) act as precursors and stimuli for synthesis of both mitochondrial and myofibrillar proteins that could potentially confer endurance and strength gains. Thus, we hypothesized that daily consumption of a dietary supplement of nine free EAAs with RET improves endurance in addition to the strength gains by RET.

METHODS

Male C57BL6J mice (9 weeks old) were assigned to control (CON), EAA, RET (ladder climbing, 3 times a week), or combined treatment of EAA and RET (EAA + RET) groups. Physical functions focusing on strength or endurance were assessed before and after the interventions. Several analyses were performed to gain better insight into the mechanisms by which muscle function was improved. We determined cumulative rates of myofibrillar and mitochondrial protein synthesis using 2H2O labelling and mass spectrometry; assessed ex vivo contractile properties and in vitro mitochondrial function, evaluated neuromuscular junction (NMJ) stability, and assessed implicated molecular singling pathways. Furthermore, whole-body and muscle insulin sensitivity along with glucose metabolism, were evaluated using a hyperinsulinaemic-euglycaemic clamp.

RESULTS

EAA + RET increased muscle mass (10%, P < 0.05) and strength (6%, P < 0.05) more than RET alone, due to an enhanced rate of integrated muscle protein synthesis (19%, P < 0.05) with concomitant activation of Akt1/mTORC1 signalling. Muscle quality (muscle strength normalized to mass) was improved by RET (i.e., RET and EAA + RET) compared with sedentary groups (10%, P < 0.05), which was associated with increased AchR cluster size and MuSK activation (P < 0.05). EAA + RET also increased endurance capacity more than RET alone (26%, P < 0.05) by increasing both mitochondrial protein synthesis (53%, P < 0.05) and DRP1 activation (P < 0.05). Maximal respiratory capacity increased (P < 0.05) through activation of the mTORC1-DRP1 signalling axis. These favourable effects were accompanied by an improvement in basal glucose metabolism (i.e., blood glucose concentrations and endogenous glucose production vs. CON, P < 0.05).

CONCLUSIONS

Combined treatment with balanced free EAAs and RET may effectively promote endurance capacity as well as muscle strength through increased muscle protein synthesis, improved NMJ stability, and enhanced mitochondrial dynamics via mTORC1-DRP1 axis activation, ultimately leading to improved basal glucose metabolism.

TAZ deficiency exacerbates psoriatic pathogenesis by increasing the histamine-releasing factor

BACKGROUND

Transcriptional coactivator with PDZ-biding motif (TAZ) is widely expressed in most tissues and interacts with several transcription factors to regulate cell proliferation, differentiation, and death, thereby influencing organ development and size control. However, very little is known about the function of TAZ in the immune system and its association with inflammatory skin diseases, so we investigated the role of TAZ in the pathogenesis of psoriasis.

RESULTS

Interestingly, TAZ was expressed in mast cells associated, particularly in lysosomes, and co-localized with histamine-releasing factor (HRF). TAZ deficiency promoted mast cell maturation and increased HRF expression and secretion by mast cells. The upregulation of HRF in TAZ deficiency was not due to increased transcription but to protein stabilization, and TAZ restoration into TAZ-deficient cells reduced HRF protein. Interestingly, imiquimod (IMQ)-induced psoriasis, in which HRF serves as a major pro-inflammatory factor, was more severe in TAZ KO mice than in WT control. HRF expression and secretion were increased by IMQ treatment and were more pronounced in TAZ KO mice treated with IMQ.

CONCLUSIONS

Thus, as HRF expression was stabilized in TAZ KO mice, psoriatic pathogenesis progressed more rapidly, indicating that TAZ plays an important role in preventing psoriasis by regulating HRF protein stability.

The interplay between hippo signaling and mitochondrial metabolism: Implications for cellular homeostasis and disease

Mitochondria are the membrane-bound organelles producing energy for cellular metabolic processes. They orchestrate diverse cell signaling cascades regulating cellular homeostasis. This functional versatility may be attributed to their ability to regulate mitochondrial dynamics, biogenesis, and apoptosis. The Hippo pathway, a conserved signaling pathway, regulates various cellular processes, including mitochondrial functions. Through its effectors YAP and TAZ, the Hippo pathway regulates transcription factors and creates a seriatim process that mediates cellular metabolism, mitochondrial dynamics, and survival. Mitochondrial dynamics also potentially regulates Hippo signaling activation, indicating a bidirectional relationship between the two. This review outlines the interplay between the Hippo signaling components and the multifaceted role of mitochondria in cellular homeostasis under physiological and pathological conditions.

TAZ deficiency impairs the autophagy-lysosomal pathway through NRF2 dysregulation and lysosomal dysfunction

Transcriptional coactivator with a PDZ-binding motif (TAZ) plays a key role in normal tissue homeostasis and tumorigenesis through interaction with several transcription factors. In particular, TAZ deficiency causes abnormal alveolarization and emphysema, and persistent TAZ overexpression contributes to lung cancer and pulmonary fibrosis, suggesting the possibility of a complex mechanism of TAZ function. Recent studies suggest that nuclear factor erythroid 2-related factor 2 (NRF2), an antioxidant defense system, induces TAZ expression during tumorigenesis and that TAZ also activates the NRF2-mediated antioxidant pathway. We thus thought to elucidate the cross-regulation of TAZ and NRF2 and the underlying molecular mechanisms and functions. TAZ directly interacted with NRF2 through the N-terminal domain and suppressed the transcriptional activity of NRF2 by preventing NRF2 from binding to DNA. In addition, the return of NRF2 to basal levels after signaling was inhibited in TAZ deficiency, resulting in sustained nuclear NRF2 levels and aberrantly increased expression of NRF2 targets. TAZ deficiency failed to modulate optimal NRF2 signaling and concomitantly impaired lysosomal acidification and lysosomal enzyme function, accumulating the abnormal autophagy vesicles and reactive oxygen species and causing protein oxidation and cellular damage in the lungs. TAZ restoration to TAZ deficiency normalized dysregulated NRF2 signaling and aberrant lysosomal function and triggered the normal autophagy-lysosomal pathway. Therefore, TAZ is indispensable for the optimal regulation of NRF2-mediated autophagy-lysosomal pathways and for preventing pulmonary damage caused by oxidative stress and oxidized proteins.

YAP/TAZ as Molecular Targets in Skeletal Muscle Atrophy and Osteoporosis

Skeletal muscles and bones are closely connected anatomically and functionally. Age-related degeneration in these tissues is associated with physical disability in the elderly and significantly impacts their quality of life. Understanding the mechanisms of age-related musculoskeletal tissue degeneration is crucial for identifying molecular targets for therapeutic interventions for skeletal muscle atrophy and osteoporosis. The Hippo pathway is a recently identified signaling pathway that plays critical roles in development, tissue homeostasis, and regeneration. The Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) are key downstream effectors of the mammalian Hippo signaling pathway. This review highlights the fundamental roles of YAP and TAZ in the homeostatic maintenance and regeneration of skeletal muscles and bones. YAP/TAZ play a significant role in stem cell function by relaying various environmental signals to stem cells. Skeletal muscle atrophy and osteoporosis are related to stem cell dysfunction or senescence triggered by YAP/TAZ dysregulation resulting from reduced mechanosensing and mitochondrial function in stem cells. In contrast, the maintenance of YAP/TAZ activation can suppress stem cell senescence and tissue dysfunction and may be used as a basis for the development of potential therapeutic strategies. Thus, targeting YAP/TAZ holds significant therapeutic potential for alleviating age-related muscle and bone dysfunction and improving the quality of life in the elderly.

Role of F-actin-mediated endocytosis and exercise in mitochondrial transplantation in an experimental Parkinson's disease mouse model

Dopaminergic neurons gradually deteriorate in Parkinson's Disease (PD), which is characterized by the intracellular accumulation of Lewy bodies that are enriched with α-synuclein protein. Mitochondrial dysfunction is one of the primary contributors to this and is considered as the central player in the pathogenesis of PD. Recently, improving mitochondrial function has been extensively explored as a therapeutic strategy in various preclinical PD models. Mitochondrial transplantation is one such naïve yet highly efficient technique that has been well explored in diseases like diabetes, NAFLD, and cardiac ischemia but not in PD. Here, we compared the effects of transplanting normal allogenic mitochondria to those of transplanting exercise-induced allogenic mitochondria isolated from the liver into the PD mouse model. It is already known that normal Mitochondrial Transplant (MT) reduces the PD pathology, but our research found out that exercise-induced mitochondria were more effective in treating the PD pathology because they had higher respiratory capacities. Additionally, compared to a standard transplant, this therapy significantly boosted the rate of mitochondrial biogenesis and the quantity of mitochondrial subunits in PD mice. Further, we also explored the mechanism of mitochondrial uptake into the cells and found that F-actin plays a key role in the internalization of mitochondria. This study is the first to demonstrate the relevance of exercise-induced allogenic MT and the function of F-actin in the internalization of mitochondria in PD mice.

Exercise mitigates age-related metabolic diseases by improving mitochondrial dysfunction

The benefits of regular physical activity are related to delaying and reversing the onset of ageing and age-related disorders, including cardiomyopathy, neurodegenerative diseases, cancer, obesity, diabetes, and fatty liver diseases. However, the molecular mechanisms of the benefits of exercise or physical activity on ageing and age-related disorders remain poorly understood. Mitochondrial dysfunction is implicated in the pathogenesis of ageing and age-related metabolic diseases. Mitochondrial health is an important mediator of cellular function. Therefore, exercise alleviates metabolic diseases in individuals with advancing ageing and age-related diseases by the remarkable promotion of mitochondrial biogenesis and function. Exerkines are identified as signaling moieties released in response to exercise. Exerkines released by exercise have potential roles in improving mitochondrial dysfunction in response to age-related disorders. This review comprehensive summarizes the benefits of exercise in metabolic diseases, linking mitochondrial dysfunction to the onset of age-related diseases. Using relevant examples utilizing this approach, the possibility of designing therapeutic interventions based on these molecular mechanisms is addressed.

Mitochondrial citrate accumulation triggers senescence of alveolar epithelial cells contributing to pulmonary fibrosis in mice

Alveolar epithelial cell (AEC) senescence is implicated in the pathogenesis of pulmonary fibrosis (PF). However, the exact mechanism underlying AEC senescence during PF remains poorly understood. Here, we reported an unrecognized mechanism for AEC senescence during PF. We found that, in bleomycin (BLM)-induced PF mice, the expressions of isocitrate dehydrogenase 3α (Idh3α) and citrate carrier (CIC) were significantly down-regulated in the lungs, which could result in mitochondria citrate (citrate^mt) accumulation in our previous study. Notably, the down-regulation of Idh3α and CIC was related to senescence. The mice with AECs-specific Idh3α and CIC deficiency by adenoviral vector exhibited spontaneous PF and senescence in the lungs. In vitro, co-inhibition of Idh3α and CIC with shRNA or inhibitors triggered the senescence of AECs, indicating that accumulated citrate^mt triggers AEC senescence. Mechanistically, citrate^mt accumulation impaired the mitochondrial biogenesis of AECs. In addition, the senescence-associated secretory phenotype from senescent AECs induced by citrate^mt accumulation activated the proliferation and transdifferentiation of NIH3T3 fibroblasts into myofibroblasts. In conclusion, we show that citrate^mt accumulation would be a novel target for protection against PF that involves senescence.

Photodegradation of Microplastics by ZnO Nanoparticles with Resulting Cellular and Subcellular Responses

Both zinc oxide nanoparticles (ZnO NPs) and microplastics (MPs) were extracted from one commercial sunscreen, while other ingredients were removed based on the "like dissolves like" principle. MPs were further extracted by acidic digestion of ZnO NPs using HCl and characterized as spherical particles of approximately 5 μm with layered sheets in an irregular shape on the surface. Although MPs were stable in the presence of simulated sunlight and water after 12 h of exposure, ZnO NPs promoted the photooxidation by producing hydroxyl radicals, with a 2.5-fold increase in the carbonyl index of the degree of surface oxidation. As a result of surface oxidation, spherical MPs were more soluble in water and fragmented to irregular shapes with sharp edges. We then compared the cytotoxicity of primary MPs and secondary MPs (25-200 mg/L) to the HaCaT cell line based on viability loss and subcellular damages. The cellular uptake of MPs transformed by ZnO NPs was enhanced by over 20%, and MPs caused higher cytotoxicity compared with the pristine ones, as evidenced by a 46% lower cell viability, 220% higher lysosomal accumulation, 69% higher cellular reactive oxygen species, 27% more mitochondrial loss, and 72% higher mitochondrial superoxide at 200 mg/L. Our study for the first time explored the activation of MPs by ZnO NPs derived from commercial products and revealed the high cytotoxicity caused by secondary MPs, providing new evidence on the effects of secondary MPs on human health.

The impact of metabolic stressors on mitochondrial homeostasis in a renal epithelial cell model of methylmalonic aciduria

Methylmalonic aciduria (MMA-uria) is caused by deficiency of the mitochondrial enzyme methylmalonyl-CoA mutase (MUT). MUT deficiency hampers energy generation from specific amino acids, odd-chain fatty acids and cholesterol. Chronic kidney disease (CKD) is a well-known long-term complication. We exposed human renal epithelial cells from healthy controls and MMA-uria patients to different culture conditions (normal treatment (NT), high protein (HP) and isoleucine/valine (I/V)) to test the effect of metabolic stressors on renal mitochondrial energy metabolism. Creatinine levels were increased and antioxidant stress defense was severely comprised in MMA-uria cells. Alterations in mitochondrial homeostasis were observed. Changes in tricarboxylic acid cycle metabolites and impaired energy generation from fatty acid oxidation were detected. Methylcitrate as potentially toxic, disease-specific metabolite was increased by HP and I/V load. Mitophagy was disabled in MMA-uria cells, while autophagy was highly active particularly under HP and I/V conditions. Mitochondrial dynamics were shifted towards fission. Sirtuin1, a stress-resistance protein, was down-regulated by HP and I/V exposure in MMA-uria cells. Taken together, both interventions aggravated metabolic fingerprints observed in MMA-uria cells at baseline. The results point to protein toxicity in MMA-uria and lead to a better understanding, how the accumulating, potentially toxic organic acids might trigger CKD.

The Complex Interplay between Imbalanced Mitochondrial Dynamics and Metabolic Disorders in Type 2 Diabetes

Type 2 diabetes mellitus (T2DM) is a global burden, with an increasing number of people affected and increasing treatment costs. The advances in research and guidelines improve the management of blood glucose and related diseases, but T2DM and its complications are still a big challenge in clinical practice. T2DM is a metabolic disorder in which insulin signaling is impaired from reaching its effectors. Mitochondria are the "powerhouses" that not only generate the energy as adenosine triphosphate (ATP) using pyruvate supplied from glucose, free fatty acid (FFA), and amino acids (AA) but also regulate multiple cellular processes such as calcium homeostasis, redox balance, and apoptosis. Mitochondrial dysfunction leads to various diseases, including cardiovascular diseases, metabolic disorders, and cancer. The mitochondria are highly dynamic in adjusting their functions according to cellular conditions. The shape, morphology, distribution, and number of mitochondria reflect their function through various processes, collectively known as mitochondrial dynamics, including mitochondrial fusion, fission, biogenesis, transport, and mitophagy. These processes determine the overall mitochondrial health and vitality. More evidence supports the idea that dysregulated mitochondrial dynamics play essential roles in the pathophysiology of insulin resistance, obesity, and T2DM, as well as imbalanced mitochondrial dynamics found in T2DM. This review updates and discusses mitochondrial dynamics and the complex interactions between it and metabolic disorders.

BaoShenTongLuo formula protects against podocyte injury by regulating AMPK-mediated mitochondrial biogenesis in diabetic kidney disease

BACKGROUND

Mitochondrial dysfunction is considered to be an important contributor in podocyte injury under diabetic conditions. The BaoShenTongLuo (BSTL) formula has been shown to reduce podocyte damage and postpone the progression of diabetic kidney disease (DKD). The potential mechanisms underlying the effects of BSTL, however, have yet to be elucidated. In this study, we aimed to investigate whether the effects of BSTL are related to the regulation of mitochondrial biogenesis via the adenosine monophosphate-activated protein kinase (AMPK) pathway.

METHODS

High-Performance Liquid Chromatography Electrospray Ionization Mass Spectrometer (HPLC-ESI-MS) analysis was performed to investigate the characteristics of pure compounds in BSTL. db/db mice and mouse podocyte clone-5 (MPC5) cells were exposed to high glucose (HG) to induce DKD and podocyte damage. Body weight, random blood glucose, urinary albumin/creatinine ratio (UACR), indicators of renal function and renal histological lesions were measured. Markers of podocyte injury, mitochondrial morphology, mitochondrial deoxyribonucleic acid (mtDNA) content, mitochondrial respiratory chain complexes activities, reactive oxygen species (ROS) production, and mitochondrial membrane potential (MMP) levels were assessed. Protein expressions of AMPK, peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α), transcription factor A (TFAM), mitochondrial fusion protein 2 (MFN2) and dynamin-related protein 1 (DRP1) were also detected. MPC5 cells were transfected with AMPKα small interfering RNA (AMPKα siRNA) to determine the underlying mechanisms of BSTL improvement of mitochondrial function under diabetic conditions.

RESULTS

In vivo, treatment with BSTL reduced the UACR levels, reversed the histopathological changes in renal tissues, and alleviated the podocyte injury observed in db/db mice. After BSTL treatment, the decreased mtDNA content and mitochondrial respiratory chain complex I, III, and IV activities were significantly improved, and these effects were accompanied by maintenance of the protein expression of p-AMPKαT172, PGC-1α, TFAM and MFN2. The in vitro experiments also showed that BSTL reduced podocyte apoptosis, suppressed excessive cellular ROS production, and reversed the decreased in MMP that were observed under HG conditions. More importantly, the effects of BSTL in enhancing mitochondrial biogenesis and reducing podocyte apoptosis were inhibited in AMPKα siRNA-treated podocytes.

CONCLUSION

BSTL plays a crucial role in protecting against podocyte injury by regulating the AMPK-mediated mitochondrial biogenesis in DKD.

Endurance Training Increases the Running Performance of Untrained Men without Changing the Mitochondrial Volume Density in the Gastrocnemius Muscle

The activity and quantity of mitochondrial proteins and the mitochondrial volume density (Mito_VD) are higher in trained muscles; however, the underlying mechanisms remain unclear. Our goal was to determine if 20 weeks’ endurance training simultaneously increases running performance, the amount and activity of mitochondrial proteins, and Mito_VD in the gastrocnemius muscle in humans. Eight healthy, untrained young men completed a 20-week moderate-intensity running training program. The training increased the mean speed of a 1500 m run by 14.0% (p = 0.008) and the running speed at 85% of maximal heart rate by 9.6% (p = 0.008). In the gastrocnemius muscle, training significantly increased mitochondrial dynamics markers, i.e., peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) by 23%, mitochondrial transcription factor A (TFAM) by 29%, optic artrophy-1 (OPA1) by 31% and mitochondrial fission factor (MFF) by 44%, and voltage-dependent anion channel 1 (VDAC1) by 30%. Furthermore, training increased the amount and maximal activity of citrate synthase (CS) by 10% and 65%, respectively, and the amount and maximal activity of cytochrome c oxidase (COX) by 57% and 42%, respectively, but had no effect on the total Mito_VD in the gastrocnemius muscle. We concluded that not Mito_VD per se, but mitochondrial COX activity (reflecting oxidative phosphorylation activity), should be regarded as a biomarker of muscle adaptation to endurance training in beginner runners.

Dimeric translationally controlled tumor protein-binding peptide 2 attenuates imiquimod-induced psoriatic inflammation through induction of regulatory T cells

Psoriasis is a chronic skin inflammation caused by a dysfunctional immune system, which causes systemic inflammation in various organs and tissues. Due to the risk of systemic inflammation and recurrence of psoriasis, it is important to identify the critical targets in the pathogenesis of psoriasis and develop targeted therapeutics. Dimerized translationally controlled tumor protein (dTCTP) promotes immune cell activation as a pro-inflammatory cytokine and plays a role in developing allergic diseases such as asthma and rhinitis. Here, we sought to explore whether dTCTP and its inhibition contributed to the development and control of imiquimod (IMQ)-induced psoriasis. Topical application of IMQ inflamed the skin of the back and ear, increased inflammatory cytokines, and decreased regulatory T cell markers. Interestingly, TCTP was significantly increased in inflamed skin and immune cells such as T cells, B cells, and macrophages after IMQ treatment and was secreted into the serum to undergo dimerization. Extracellular dTCTP treatment selectively suppressed regulatory T (Treg) cells, not other effector T helper (Th) cells, and increased M1 macrophages. Moreover, dTCTP-binding peptide 2 (dTBP2), a dTCTP inhibitor peptide, effectively attenuated the systemic inflammatory responses, including Th17 cell response, and alleviated psoriatic skin inflammation. dTBP2 blocked dTCTP-mediated Treg suppression and stimulated the expression of Treg cell markers in the spleen and inflammatory skin lesions. These results suggest that dTCTP dysregulated immune balance through Treg suppression in psoriatic inflammation and that functional inhibition of dTCTP by dTBP2 maintained immune homeostasis and attenuated inflammatory skin diseases by expanding Treg cells.

Decapeptide from Potato Hydrolysate Induces Myogenic Differentiation and Ameliorates High Glucose-Associated Modulations in Protein Synthesis and Mitochondrial Biogenesis in C2C12 Cells

Sarcopenia is characterized as an age-related loss of muscle mass that results in negative health consequences such as decreased strength, insulin resistance, slowed metabolism, increased body fat mass, and a substantially diminished quality of life. Additionally, conditions such as high blood sugar are known to further exacerbate muscle degeneration. Skeletal muscle development and regeneration following injury or disease are based on myoblast differentiation. Bioactive peptides are biologically active peptides found in foods that could have pharmacological functions. The aim of this paper was to investigate the effect of decapeptide DI-10 from the potato alcalase hydrolysate on myoblast differentiation, muscle protein synthesis, and mitochondrial biogenesis in vitro. The treatment of C2C12 myoblasts with DI-10 (10 µg/mL) did not induce cell death. DI-10 treatment in C2C12 myoblast cells accelerates the phosphorylation of promyogenic kinases such as ERK, Akt and mTOR proteins in a dose-dependent manner. DI-10 improves myotubes differentiation and upregulates the expression of myosin heavy chain (MyHC) protein in myoblast cells under differentiation medium with high glucose. DI-10 effectively increased the phosphorylation of promyogenic kinases Akt, mTOR, and mitochondrial-related transcription factors AMPK and PGC1α expression under hyperglycemic conditions. Further, decapeptide DI-10 decreased the expression of Murf1 and MAFbx proteins, which are involved in protein degradation and muscle atrophy. Our reports support that decapeptide DI-10 could be potentially used as a therapeutic candidate for preventing muscle degeneration in sarcopenia.