The SarcoEndoplasmic Reticulum Calcium ATPase (SERCA) pump: a potential target for intervention in aging and skeletal muscle pathologies

Timing Matters: Time of Day Impacts the Ergogenic Effects of Caffeine-A Narrative Review

Caffeine has attracted significant attention from researchers in the sports field due to its well-documented ergogenic effects across various athletic disciplines. As research on caffeine continues to progress, there has been a growing emphasis on evaluating caffeine dosage and administration methods. However, investigations into the optimal timing of caffeine intake remain limited. Therefore, this narrative review aimed to assess the ergogenic effects of caffeine administration at different times during the morning (06:00 to 10:00) and evening (16:00 to 21:00). The review findings suggest that circadian rhythms play a substantial role in influencing sports performance, potentially contributing to a decline in morning performance. Caffeine administration has demonstrated effectiveness in mitigating this phenomenon, resulting in ergogenic effects and performance enhancement, even comparable to nighttime levels. While the specific mechanisms by which caffeine regulates circadian rhythms and influences sports performance remain unclear, this review also explores the mechanisms underlying caffeine's ergogenic effects, including the adenosine receptor blockade, increased muscle calcium release, and modulation of catecholamines. Additionally, the narrative review underscores caffeine's indirect impact on circadian rhythms by enhancing responsiveness to light-induced phase shifts. Although the precise mechanisms through which caffeine improves morning performance declines via circadian rhythm regulation necessitate further investigations, it is noteworthy that the timing of caffeine administration significantly affects its ergogenic effects during exercise. This emphasizes the importance of considering caffeine intake timing in future research endeavors to optimize its ergogenic potential and elucidate its mechanisms.

Redox organization of living systems

Redox organization governs an underlying simplicity in living systems. Critically, redox reactions enable the essential characteristics of life: extraction of energy from the environment, use of energy to support metabolic and structural organization, use of dynamic redox responses to defend against environmental threats, and use of redox mechanisms to direct differentiation of cells and organ systems essential for reproduction. These processes are sustained through a redox context in which electron donor/acceptor couples are poised at substantially different steady-state redox potentials, some with relatively reducing steady states and others with relatively oxidizing steady states. Redox-sensitive thiols of the redox proteome, as well as low molecular weight redox-active molecules, are maintained individually by the kinetics of oxidation-reduction within this redox system. Recent research has revealed opposing network interactions of the metallome, redox proteome, metabolome and transcriptome, which appear to be an evolved redox response structure to maintain stability of an organism in the presence of variable oxidative environments. Considerable opportunity exists to improve human health through detailed understanding of these redox networks so that targeted interventions can be developed to support new avenues for redox medicine.

The role of calcium in neuronal membrane tension and synaptic plasticity

Calcium is a primary second messenger that plays a role in cellular functions including growth, movement and responses to drugs. The role that calcium plays in mediating communication between neurons by synaptic vesicle release is well established. This review focuses on the dependence of the physical properties of neuronal plasma membranes on calcium levels. After describing the key features of synaptic plasticity, we summarize the general role of calcium in cell function and the signaling pathways responsible for intracellular increase in calcium levels. We then present findings showing that increases in intracellular calcium levels cause neurites to contract and break synaptic connections by changes in membrane tension.

Neuroprotective treatment with the nitrone compound OKN-007 mitigates age-related muscle weakness in aging mice

Despite the universal impact of sarcopenia on compromised health and quality of life in the elderly, promising pharmaceutical approaches that can effectively mitigate loss of muscle and function during aging have been limited. Our group and others have reported impairments in peripheral motor neurons and loss of muscle innervation as initiating factors in sarcopenia, contributing to mitochondrial dysfunction and elevated oxidative stress in muscle. We recently reported a reduction in α motor neuron loss in aging mice in response to the compound OKN-007, a proposed antioxidant and anti-inflammatory agent. In the current study, we asked whether OKN-007 treatment in wildtype male mice for 8-9 months beginning at 16 months of age can also protect muscle mass and function. At 25 months of age, we observed a reduction in the loss of whole-body lean mass, a reduced loss of innervation at the neuromuscular junction and well-preserved neuromuscular junction morphology in OKN-007 treated mice versus age matched wildtype untreated mice. The loss in muscle force generation in aging mice (~ 25%) is significantly improved with OKN-007 treatment. In contrast, OKN-007 treatment provided no protection in loss of muscle mass in aging mice. Mitochondrial function was improved by OKN-007 treatment, consistent with its potential antioxidative properties. Together, these exciting findings are the first to demonstrate that interventions through neuroprotection can be an effective therapy to counter aging-related muscle dysfunction.

Cancer-associated muscle weakness - From triggers to molecular mechanisms

Skeletal muscle weakness is a debilitating consequence of many malignancies. Muscle weakness has a negative impact on both patient wellbeing and outcome in a range of cancer types and can be the result of loss of muscle mass (i.e. muscle atrophy, cachexia) and occur independently of muscle atrophy or cachexia. There are multiple cancer specific triggers that can initiate the progression of muscle weakness, including the malignancy itself and the tumour environment, as well as chemotherapy, radiotherapy and malnutrition. This can induce weakness via different routes: 1) impaired intrinsic capacity (i.e., contractile dysfunction and intramuscular impairments in excitation-contraction coupling or crossbridge cycling), 2) neuromuscular disconnection and/or 3) muscle atrophy. The mechanisms that underlie these pathways are a complex interplay of inflammation, autophagy, disrupted protein synthesis/degradation, and mitochondrial dysfunction. The current lack of therapies to treat cancer-associated muscle weakness highlight the critical need for novel interventions (both pharmacological and non-pharmacological) and mechanistic insight. Moreover, most research in the field has placed emphasis on directly improving muscle mass to improve muscle strength. However, accumulating evidence suggests that loss of muscle function precedes atrophy. This review primarily focuses on cancer-associated muscle weakness, independent of cachexia, and provides a solid background on the underlying mechanisms, methodology, current interventions, gaps in knowledge, and limitations of research in the field. Moreover, we have performed a mini-systematic review of recent research into the mechanisms behind muscle weakness in specific cancer types, along with the main pathways implicated.

Small peptides: could they have a big role in metabolism and the response to exercise?

Exercise is a powerful non-pharmacological intervention for the treatment and prevention of numerous chronic diseases. Contracting skeletal muscles provoke widespread perturbations in numerous cells, tissues and organs, which stimulate multiple integrated adaptations that ultimately contribute to the many health benefits associated with regular exercise. Despite much research, the molecular mechanisms driving such changes are not completely resolved. Technological advancements beginning in the early 1960s have opened new avenues to explore the mechanisms responsible for the many beneficial adaptations to exercise. This has led to increased research into the role of small peptides (<100 amino acids) and mitochondrially derived peptides in metabolism and disease, including those coded within small open reading frames (sORFs; coding sequences that encode small peptides). Recently, it has been hypothesized that sORF-encoded mitochondrially derived peptides and other small peptides play significant roles as exercise-sensitive peptides in exercise-induced physiological adaptation. In this review, we highlight the discovery of mitochondrially derived peptides and newly discovered small peptides involved in metabolism, with a specific emphasis on their functions in exercise-induced adaptations and the prevention of metabolic diseases. In light of the few studies available, we also present data on how both single exercise sessions and exercise training affect expression of sORF-encoded mitochondrially derived peptides. Finally, we outline numerous research questions that await investigation regarding the roles of mitochondrially derived peptides in metabolism and prevention of various diseases, in addition to their roles in exercise-induced physiological adaptations, for future studies.

Proteomic analysis shows decreased type I fibers and ectopic fat accumulation in skeletal muscle from women with PCOS

Background

Polycystic ovary syndrome's (PCOS) main feature is hyperandrogenism, which is linked to a higher risk of metabolic disorders. Gene expression analyses in adipose tissue and skeletal muscle reveal dysregulated metabolic pathways in women with PCOS, but these differences do not necessarily lead to changes in protein levels and biological function.

Methods

To advance our understanding of the molecular alterations in PCOS, we performed global proteomic and phosphorylation site analysis using tandem mass spectrometry, and analyzed gene expression and methylation. Adipose tissue and skeletal muscle were collected at baseline from 10 women with and without PCOS, and in women with PCOS after 5 weeks of treatment with electrical stimulation.

Results

Perilipin-1, a protein that typically coats the surface of lipid droplets in adipocytes, was increased whereas proteins involved in muscle contraction and type I muscle fiber function were downregulated in PCOS muscle. Proteins in the thick and thin filaments had many altered phosphorylation sites, indicating differences in protein activity and function. A mouse model was used to corroborate that androgen exposure leads to a shift in muscle fiber type in controls but not in skeletal muscle-specific androgen receptor knockout mice. The upregulated proteins in muscle post treatment were enriched in pathways involved in extracellular matrix organization and wound healing, which may reflect a protective adaptation to repeated contractions and tissue damage due to needling. A similar, albeit less pronounced, upregulation in extracellular matrix organization pathways was also seen in adipose tissue.

Conclusions

Our results suggest that hyperandrogenic women with PCOS have higher levels of extra-myocellular lipids and fewer oxidative insulin-sensitive type I muscle fibers. These could be key factors leading to insulin resistance in PCOS muscle while electric stimulation-induced tissue remodeling may be protective.

Funding

Swedish Research Council (2020-02485, 2022-00550, 2020-01463), Novo Nordisk Foundation (NNF22OC0072904), and IngaBritt and Arne Lundberg Foundation. Clinical trial number NTC01457209.

Modulation of sarcopenia phenotypes by glutathione peroxidase 4 overexpression in mice

Our laboratory previously showed lipid hydroperoxides and oxylipin levels are elevated in response to loss of skeletal muscle innervation and are associated with muscle pathologies. To elucidate the pathological impact of lipid hydroperoxides, we overexpressed glutathione peroxidase 4 (GPx4), an enzyme that targets reduction of lipid hydroperoxides in membranes, in adult CuZn superoxide dismutase knockout (Sod1KO) mice that show accelerated muscle atrophy associated with loss of innervation. The gastrocnemius muscle from Sod1KO mice shows reduced mitochondrial respiration and elevated oxidative stress (F2 -isoprostanes and hydroperoxides) compared to wild-type (WT) mice. Overexpression of GPx4 improved mitochondrial respiration and reduced hydroperoxide generation in Sod1KO mice, but did not attenuate the muscle loss that occurs in Sod1KO mice. In contrast, contractile force generation is reduced in EDL muscle in Sod1KO mice relative to WT mice, and overexpression of GPx4 restored force generation to WT levels in Sod1KO mice. GPx4 overexpression also prevented loss of muscle contractility at the single fibre level in fast-twitch fibres from Sod1KO mice. Muscle fibres from Sod1KO mice were less sensitive to both depolarization and calcium at the single fibre level and exhibited a reduced activation by S-glutathionylation. GPx4 overexpression in Sod1KO mice rescued the deficits in both membrane excitability and calcium sensitivity of fast-twitch muscle fibres. Overexpression of GPx4 also restored the sarco/endoplasmic reticulum Ca2+ -ATPase activity in Sod1KO gastrocnemius muscles. These data suggest that GPx4 plays an important role in preserving excitation-contraction coupling function and Ca2+ homeostasis, and in maintaining muscle and mitochondrial function in oxidative stress-induced sarcopenia. KEY POINTS: Knockout of CuZn superoxide dismutase (Sod1KO) induces elevated oxidative stress with accelerated muscle atrophy and weakness. Glutathione peroxidase 4 (GPx4) plays a fundamental role in the reduction of lipid hydroperoxides in membranes, and overexpression of GPx4 improves mitochondrial respiration and reduces hydroperoxide generation in Sod1KO mice. Muscle contractile function deficits in Sod1KO mice are alleviated by the overexpression of GPx4. GPx4 overexpression in Sod1KO mice rescues the impaired muscle membrane excitability of fast-twitch muscle fibres and improves their calcium sensitivity. Sarco/endoplasmic reticulum Ca2+ -ATPase activity in Sod1KO muscles is decreased, and it is restored by the overexpression of GPx4. Our results confirm that GPx4 plays an important role in preserving excitation-contraction coupling function and Ca2+ homeostasis, and maintaining muscle and mitochondrial function in oxidative stress-induced sarcopenia.

Case report: Revealing the rare-a Brody Disease patient from Turkey expanding the phenotype

Brody Disease is an exceptionally rare, autosomal recessive myopathy attributed to the pathogenic variants in the ATP2A1, which encodes the sarcoplasmic/endoplasmic reticulum Ca (2+) ATPase type 1 protein SERCA1. It was first described by Brody IA in 1969. To date, only thirty-three Brody families with forty-seven patients have been reported in the literature, and the disease prevalence is considered as 1 in 10 million, demonstrating the peculiarity of the disease. Clinical characteristics of Brody Disease include muscle stiffness after exercise, myalgia, and muscle cramps. Brody Disease patients generally have disease onset in the first decade, and genetic diagnosis is delayed as a consequence of both the rareness and the mild course of the disease. Here, we report a Turkish Brody Disease patient with a homozygous c.428G>A p.Arg143Gln (NM_004320.4) missense mutation in the ATP2A1. The male patient, whose symptoms started at the age of 14-15, is now 36 years old. His clinical manifestations are athletic appearance, exotropia, slightly elevated creatine kinase (CK), mild progressive proximal muscle weakness in the lower extremities, muscle cramps, pain and stiffness. The patient described here has a very mild progression with an onset in the second decade, expanding the Brody Disease phenotype. The study also implies that in the era of emerging genetic therapies, the routine testing of patients with myopathies is a prerequisite since not only future therapies will be designed on molecular findings, but also currently available symptomatic and palliative treatment options will be more precisely applied.

The physiological basis with uterine myometrium contractions from electro-mechanical/hormonal myofibril function to the term and preterm labor

Background

Most labor-related problems can be attributed to the uterine myometrium muscle, as this irritable tissue must suppress its irritability potential during pregnancy. Unfortunately, fewer studies have investigated the causes of this lack of suppression in preterm labor.

Methods

We conducted a scoping narrative review using three online databases (PubMed, Scopus, and Science Direct).

Results

The review focused on ion channel functions in the myometrium, including sodium channels [Na K-ATPase, Na-activated K channels (Slo2), voltage-gated (SCN) Na+, Na+ leaky channels, nonselective (NALCN) channels], potassium channels [KATP (Kir6) channels, voltage-dependent K channels (Kv4, Kv7, and Kv11), twin-pore domain K channels (TASK, TREK), inward rectifier Kir7.1, Ca2+-activated K+ channels with large (KCNMA1, Slo1), small (KCNN1-3), intermediate (KCNN4) conductance], and calcium channels [L-Type and T-type Ca2+ channels, calcium-activated chloride channels (CaCC)], as well as hyperpolarization-activated cation channels. These channels' functions are associated with hormonal effects such as oxytocin, estrogen/progesterone, and local prostaglandins.

Conclusion

Electromechanical/hormonal activity and environmental autocrine factors can serve as the primary practical basis for premature uterine contractions in term/preterm labor. Our findings highlight the significance of.1.the amplitude rate of hyperpolarization and the frequency of contractions,2.changes in the estrogen/progesterone ratio,3.Prostaglandins E/F involvement in initiating potential spikes and the increase of intracytoplasmic Ca2+.This narrative study highlights the range of hyperpolarization and the frequency of myometrium contractions as crucial factors. The synchronized complex progress of estrogen to progesterone ratio and prostaglandins plays a significant role in initiating potential spikes and increasing intracytoplasmic Ca2+, which further influences the contraction process during labor. Insights into myometrium physiology gained from this study may pave the way for much-needed new treatments to reduce problems associated with normal and preterm labor.

Resting membrane state as an interplay of electrogenic transporters with various pumps

In this study, a new idea that electrogenic transporters determine cell resting state is presented. The previous assumption was that pumps, especially the sodium one, determine it. The latter meets difficulties, because it violates the law of conservation of energy; also a significant deficit of pump activity is reported. The amount of energy carried by a single ATP molecule reflects the potential of the inner mitochondrial membrane, which is about -200 mV. If pumps enforce a resting membrane potential that is more than twice smaller, then the majority of energy stored in ATP would be dissipated by each pump turning. However, this problem could be solved if control is transferred from pumps to something else, e.g., electrogenic transporters. Then pumps would transfer the energy to the ionic gradient without losses, while the cell surface membrane potential would be associated with the reversal potential of some electrogenic transporters. A minimal scheme of this type would include a sodium-calcium exchanger as well as sodium and calcium pumps. However, note that calcium channels and pumps are positioned along both intracellular organelles and the surface membrane. Therefore, the above-mentioned scheme would involve them as well as possible intercellular communications. Such schemes where various kinds of pumps are assumed to work in parallel may explain, to a great extent, the slow turning rate of the individual members. Interaction of pumps and transporters positioned at distant biological membranes with various forms of energy transfer between them may thus result in hypoxic/reperfusion injury, different kinds of muscle fatigue, and nerve-glia interactions.

FiNuTyper: Design and validation of an automated deep learning-based platform for simultaneous fiber and nucleus type analysis in human skeletal muscle

AIM

While manual quantification is still considered the gold standard for skeletal muscle histological analysis, it is time-consuming and prone to investigator bias. To address this challenge, we assembled an automated image analysis pipeline, FiNuTyper (Fiber and Nucleus Typer).

METHODS

We integrated recently developed deep learning-based image segmentation methods, optimized for unbiased evaluation of fresh and postmortem human skeletal muscle, and utilized SERCA1 and SERCA2 as type-specific myonucleus and myofiber markers after validating them against the traditional use of MyHC isoforms.

RESULTS

Parameters including cross-sectional area, myonuclei per fiber, myonuclear domain, central myonuclei per fiber, and grouped myofiber ratio were determined in a fiber-type-specific manner, revealing that a large degree of sex- and muscle-related heterogeneity could be detected using the pipeline. Our platform was also tested on pathological muscle tissue (ALS and IBM) and adapted for the detection of other resident cell types (leucocytes, satellite cells, capillary endothelium).

CONCLUSION

In summary, we present an automated image analysis tool for the simultaneous quantification of myofiber and myonuclear types, to characterize the composition and structure of healthy and diseased human skeletal muscle.

Influence of age on force and re-lengthening dynamics after tetanic stimulation withdrawal in the tibialis anterior muscle

PURPOSE

During alternate movements across a joint, the changeover from one direction of rotation to the opposite may be influenced by the delay and rate of tension reduction and the compliance to re-lengthening of the previously active muscle group. Given the aging process may affect the above-mentioned factors, this work aimed to compare the dynamics of both the ankle torque decline and muscle re-lengthening, mirrored by mechanomyogram (MMG), in the tibialis anterior because of its important role in gait.

METHODS

During the relaxation phase, after a supramaximal 35 Hz stimulation applied at the superficial motor point, in 20 young (Y) and 20 old (O) subjects, the torque (T) and MMG dynamics characteristics were measured.

RESULTS

The T and MMG analysis provided: (I) the beginning of the decay after cessation of stimulation (T: 22.51 ± 5.92 ms [Y] and 51.35 ± 15.21 ms [O]; MMG: 27.38 ± 6.93 ms [Y] and 61.41 ± 18.42 ms [O]); (II) the maximum rate of reduction (T: - 110.4 ± 45.56 Nm/s [Y] and - 52.72 ± 32.12 Nm/s [O]; MMG: - 24.47 ± 10.95 mm/s [Y] and - 13.76 ± 6.54 mm/s [O]); (III) the muscle compliance, measuring the MMG reduction of every 10% reduction of torque (bin 20-10%: 15.69 ± 7.5[Y] and 10.8 ± 3.3 [O]; bin 10-0%: 22.12 ± 10.3 [Y] and 17.58 ± 5.6 [O]).

CONCLUSION

Muscle relaxation results are different in Y and O and can be monitored by a non-invasive method measuring physiological variables of torque and re-lengthening dynamics at the end of the electromechanical coupling previously induced by the neuromuscular stimulation.

Calcium channelopathies in neurodegenerative disorder: an untold story of RyR and SERCA

INTRODUCTION

Recent neuroscience breakthroughs have shed light on the sophisticated relationship between calcium channelopathies and movement disorders, exposing a previously undiscovered tale focusing on the Ryanodine Receptor (RyR) and the Sarco/Endoplasmic Reticulum Calcium ATPase (SERCA). Calcium signaling mainly orchestrates neural communication, which regulates synaptic transmission and total network activity. It has been determined that RyR play a significant role in managing neuronal functions, most notably in releasing intracellular calcium from the endoplasmic reticulum.

AREAS COVERED

It highlights the involvement of calcium channels such as RyR and SERCA in physiological and pathophysiological conditions.

EXPERT OPINION

Links between RyR and SERCA activity dysregulation, aberrant calcium levels, motor and cognitive dysfunction have brought attention to the importance of RyR and SERCA modulation in neurodegenerative disorders. Understanding the obscure function of these proteins will open up new therapeutic possibilities to address the underlying causes of neurodegenerative diseases. The unreported RyR and SERCA narrative broadens the understanding of calcium channelopathies in movement disorders and calls for more research into cutting-edge therapeutic approaches.

Phosphate toxicity and SERCA2a dysfunction in sudden cardiac arrest

Almost half of the people who die from sudden cardiac arrest have no detectable heart disease. Among children and young adults, the cause of approximately one-third of deaths from sudden cardiac arrest remains unexplained after thorough examination. Sudden cardiac arrest and related sudden cardiac death are attributed to dysfunctional cardiac ion-channels. The present perspective paper proposes a pathophysiological mechanism by which phosphate toxicity from cellular accumulation of dysregulated inorganic phosphate interferes with normal calcium handling in the heart, leading to sudden cardiac arrest. During cardiac muscle relaxation following contraction, SERCA2a pumps actively transport calcium ions into the sarcoplasmic reticulum, powered by ATP hydrolysis that produces ADP and inorganic phosphate end products. Reviewed evidence supports the proposal that end-product inhibition of SERCA2a occurs as increasing levels of inorganic phosphate drive up phosphate toxicity and bring cardiac function to a sudden and unexpected halt. The paper concludes that end-product inhibition from ATP hydrolysis is the mediating factor in the association of sudden cardiac arrest with phosphate toxicity. However, current technology lacks the ability to directly measure this pathophysiological mechanism in active myocardium, and further research is needed to confirm phosphate toxicity as a risk factor in individuals with sudden cardiac arrest. Moreover, phosphate toxicity may be reduced through modification of dietary phosphate intake, with potential for employing low-phosphate dietary interventions to reduce the risk of sudden cardiac arrest.

Biochemical and proteomic insights into sarcoplasmic reticulum Ca2+-ATPase complexes in skeletal muscles

INTRODUCTION

Skeletal muscles contain large numbers of high-molecular-mass protein complexes in elaborate membrane systems. Integral membrane proteins are involved in diverse cellular functions including the regulation of ion handling, membrane homeostasis, energy metabolism and force transmission.

AREAS COVERED

The proteomic profiling of membrane proteins and large protein assemblies in skeletal muscles are outlined in this article. This includes a critical overview of the main biochemical separation techniques and the mass spectrometric approaches taken to study membrane proteins. As an illustrative example of an analytically challenging large protein complex, the proteomic detection and characterization of the Ca2+-ATPase of the sarcoplasmic reticulum is discussed. The biological role of this large protein complex during normal muscle functioning, in the context of fiber type diversity and in relation to mechanisms of physiological adaptations and pathophysiological abnormalities is evaluated from a proteomics perspective.

EXPERT OPINION

Mass spectrometry-based muscle proteomics has decisively advanced the field of basic and applied myology. Although it is technically challenging to study membrane proteins, innovations in protein separation methodology in combination with sensitive mass spectrometry and improved systems bioinformatics has allowed the detailed proteomic detection and characterization of skeletal muscle membrane protein complexes, such as Ca2+-pump proteins of the sarcoplasmic reticulum.

SERCA inhibition improves lifespan and healthspan in a chemical model of Parkinson disease in Caenorhabditis elegans

Introduction: The high prevalence of neurodegenerative diseases in our population and the lack of effective treatments encourage the search for new therapeutic targets for these pathologies. We have recently described that submaximal inhibition of the Sarco-Endoplasmic Reticulum Ca²⁺ ATPase (SERCA), the main responsible for ER calcium storage, is able to increase lifespan in Caenorhabditis elegans worms by mechanisms involving mitochondrial metabolism and nutrient-sensitive pathways. Methods: We have studied here the effects of submaximal SERCA inhibition in a chemical model of Parkinson's disease (PD) induced in C. elegans worms by treatment with the mitochondrial complex I inhibitor rotenone. For specific SERCA inhibition, we treated worms with RNAi against sca-1, the sole orthologue of SERCA in C. elegans. Results and Discussion: Our results show that rotenone produces alterations in worms that include decreased lifespan, smaller size, reduced fertility, decreased motility, defecation and pumping rate, increased mitochondrial ROS production, reduced mitochondrial membrane potential and oxygen consumption rate, altered mitochondrial structure, and altered ethanol preference in behavioral studies. Most of these alterations were either fully or partially reversed in worms treated with sca-1 RNAi, suggesting that SERCA inhibition could be a novel pharmacological target in the prevention or treatment of neurodegeneration.

Unconventional myosin VI in the heart: Involvement in cardiac dysfunction progressing with age

Hypertrophic cardiomyopathy is the most common cardiovascular disease, which is characterized by structural and functional myocardial abnormalities. It is caused predominantly by autosomal dominant mutations, mainly in genes encoding cardiac sarcomeric proteins, resulting in diverse phenotypical patterns and a heterogenic clinical course. Unconventional myosin VI (MVI) is one of the proteins important for heart function, as it was shown that a point mutation within MYO6 is associated with left ventricular hypertrophy. Previously, we showed that MVI is expressed in the cardiac muscle, where it localizes to the sarcoplasmic reticulum and intercalated discs. Here, we addressed the mechanisms of its involvement in cardiac dysfunction in Snell's waltzer mice (natural MVI knockouts) during heart development. We showed that heart enlargement was already seen in the E14.5 embryos and newborn animals (P0), and was maintained throughout the examined lifespan (up to 12 months). The higher levels of MVI were observed in the hearts of E14.5 embryos and P0 of control heterozygous mice. A search for the mechanisms behind the observed phenotype revealed several changes, accumulation of which resulted in age-progressing heart dysfunction. The main changes that mostly contribute to this functional impairment are the increase in cardiomyocyte proliferation in newborns, disorganization of intercalated discs, and overexpression of SERCA2 in hearts isolated from 12-month-old mice, indicative of functional alterations of sarcoplasmic reticulum. Also, possible aberrations in the heart vascularization, observed in 12-month-old animals could be additional factors responsible for MVI-associated heart dysfunction.

Pomiferin targets SERCA, mTOR, and P-gp to induce autophagic cell death in apoptosis-resistant cancer cells, and reverses the MDR phenotype in cisplatin-resistant tumors in vivo

Drug resistance in cancer has been classified as innate resistance or acquired resistance, which were characterized by apoptotic defects and ABC transporters overexpression respectively. Therefore, to preclude or reverse these resistance mechanisms could be a promising strategy to improve chemotherapeutic outcomes. In this study, a natural product from Osage Orange, pomiferin, was identified as a novel autophagy activator that circumvents innate resistance by triggering autophagic cell death via SERCA inhibition and activation of the CaMKKβ-AMPK-mTOR signaling cascade. In addition, pomiferin also directly inhibited the P-gp (MDR1/ABCB1) efflux and reversed acquired resistance by potentiating the accumulation and efficacy of the chemotherapeutic agent, cisplatin. In vivo study demonstrated that pomiferin triggered calcium-mediated tumor suppression and exhibited an anti-metastatic effect in the LLC-1 lung cancer-bearing mouse model. Moreover, as an adjuvant, pomiferin potentiated the anti-tumor effect of the chemotherapeutic agent, cisplatin, in RM-1 drug-resistant prostate cancer-bearing mouse model by specially attenuating ABCB1-mediated drug efflux, but not ABCC5, thereby promoting the accumulation of cisplatin in tumors. Collectively, pomiferin may serve as a novel effective agent for circumventing drug resistance in clinical applications.

Whole Transcriptome Analysis of Differentially Expressed Genes in Cultured Nile Tilapia (O. niloticus) Subjected to Chronic Stress Reveals Signaling Pathways Associated with Depressed Growth

Chronic stress is a serious threat to aquaculture as it lowers fish growth performance and compromises fish welfare. The exact mechanism by which growth is retarded is, however, not clearly understood. This study sought to elucidate the gene expression profiles associated with chronic stress in cultured Nile tilapia (Oreochromis niloticus) reared for 70 days at different ammonia concentrations and stocking densities. Fish in the treatment groups showed negative growth, while the controls showed positive allometric growth. The specific condition factor (Kn) ranged from 1.17 for the controls to 0.93 for the ammonia and 0.91 for the stocking density treatments. RNA was extracted from muscle tissue using TRIzol followed by library construction and Illumina sequencing. Comparative transcriptome analysis revealed 209 differentially expressed genes (DEGs) (156 up- and 53 down-regulated) in the ammonia and 252 DEGs (175 up- and 77 down-regulated) in the stocking density treatment. In both treatments, 24 and 17 common DEGs were up- and down-regulated, respectively. DEGs were significantly enriched in six pathways associated with muscle activity, energy mobilization and immunity. The heightened muscular activity consumes energy which would otherwise have been utilized for growth. These results bring to fore the molecular mechanisms underlying chronic stress’ suppression of growth in cultured Nile tilapia.

Dwarf Open Reading Frame (DWORF) Gene Therapy Ameliorated Duchenne Muscular Dystrophy Cardiomyopathy in Aged mdx Mice

Background Cardiomyopathy is a leading health threat in Duchenne muscular dystrophy (DMD). Cytosolic calcium upregulation is implicated in DMD cardiomyopathy. Calcium is primarily removed from the cytosol by the sarcoendoplasmic reticulum calcium ATPase (SERCA). SERCA activity is reduced in DMD. Improving SERCA function may treat DMD cardiomyopathy. Dwarf open reading frame (DWORF) is a recently discovered positive regulator for SERCA, hence, a potential therapeutic target. Methods and Results To study DWORF's involvement in DMD cardiomyopathy, we quantified DWORF expression in the heart of wild-type mice and the mdx model of DMD. To test DWORF gene therapy, we engineered and characterized an adeno-associated virus serotype 9-DWORF vector. To determine if this vector can mitigate DMD cardiomyopathy, we delivered it to 6-week-old mdx mice (6×1012 vector genome particles/mouse) via the tail vein. Exercise capacity, heart histology, and cardiac function were examined at 18 months of age. We found DWORF expression was significantly reduced at the transcript and protein levels in mdx mice. Adeno-associated virus serotype 9-DWORF vector significantly enhanced SERCA activity. Systemic adeno-associated virus serotype 9-DWORF therapy reduced myocardial fibrosis and improved treadmill running, electrocardiography, and heart hemodynamics. Conclusions Our data suggest that DWORF deficiency contributes to SERCA dysfunction in mdx mice and that DWORF gene therapy holds promise to treat DMD cardiomyopathy.

IgE-dependent human basophil responses are inversely associated with the sarcoplasmic reticulum Ca2+-ATPase (SERCA)

Basophils crucially contribute to allergies and other Th2-driven diseases by rapidly releasing inflammatory and immunomodulatory mediators following high-affinity IgE-receptor crosslinking. Although these basophil-mediated responses depend on sensitization with antigen-specific IgE, this does not necessarily predict clinical symptom severity. It is thought that the balance of early stimulatory (e.g. SYK) and inhibitory (e.g. SHIP-1) intracellular signals are associated with basophil responsiveness, which is also critically dependent on calcium mobilization. Previous studies suggest that the sarcoplasmic reticulum Ca²⁺-ATPase (SERCA2), which regulates cytosolic calcium levels, may be inversely associated with airway smooth muscle reactivity in asthma. Since basophils are implicated in asthma severity, our aims were to address whether SERCA2 is implicated in human basophil responses, especially following IgE-mediated activation. Human basophils were obtained from buffy coats, following research ethics approval, and further purified by immunomagnetic cell sorting. Expressions of SERCA2, and other isoforms, were determined by Western blotting in parallel to measuring IgE-dependent histamine releases from the same donors. The effects of a SERCA-activator and inhibitor were also assessed on their abilities to modulate basophil histamine release. We observed an inverse correlation between basophil responsiveness to IgE-dependent stimulation and SERCA2 expression. Thapsigargin, a highly-specific SERCA inhibitor, stimulated basophil histamine release and potentiated IgE-dependent secretion of the amine. Conversely, disulfiram, a SERCA activator, inhibited IgE-dependent basophil activation. The results obtained from this exploratory study indicate that SERCA2 may be an additional regulator of basophil reactivity alongside early excitatory or inhibitory signal transduction pathways.

A comprehensive review of the novel therapeutic targets for the treatment of diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM) is characterized by structural and functional abnormalities in the myocardium affecting people with diabetes. Treatment of DCM focuses on glucose control, blood pressure management, lipid-lowering, and lifestyle changes. Due to limited therapeutic options, DCM remains a significant cause of morbidity and mortality in patients with diabetes, thus emphasizing the need to develop new therapeutic strategies. Ongoing research is aimed at understanding the underlying molecular mechanism(s) involved in the development and progression of DCM, including oxidative stress, inflammation, and metabolic dysregulation. The goal is to develope innovative pharmaceutical therapeutics, offering significant improvements in the clinical management of DCM. Some of these approaches include the effective targeting of impaired insulin signaling, cardiac stiffness, glucotoxicity, lipotoxicity, inflammation, oxidative stress, cardiac hypertrophy, and fibrosis. This review focuses on the latest developments in understanding the underlying causes of DCM and the therapeutic landscape of DCM treatment.

Proteomic profiling of impaired excitation-contraction coupling and abnormal calcium handling in muscular dystrophy

The X-linked inherited neuromuscular disorder Duchenne muscular dystrophy is characterised by primary abnormalities in the membrane cytoskeletal component dystrophin. The almost complete absence of the Dp427-M isoform of dystrophin in skeletal muscles renders contractile fibres more susceptible to progressive degeneration and a leaky sarcolemma membrane. This in turn results in abnormal calcium homeostasis, enhanced proteolysis and impaired excitation-contraction coupling. Biochemical and mass spectrometry-based proteomic studies of both patient biopsy specimens and genetic animal models of dystrophinopathy have demonstrated significant changes in the concentration and/or physiological function of essential calcium-regulatory proteins in dystrophin-lacking voluntary muscles. Abnormalities include dystrophinopathy-associated changes in voltage sensing receptors, calcium release channels, calcium pumps and calcium binding proteins. This review article provides an overview of the importance of the sarcolemmal dystrophin-glycoprotein complex and the wider dystrophin complexome in skeletal muscle and its linkage to depolarisation-induced calcium-release mechanisms and the excitation-contraction-relaxation cycle. Besides chronic inflammation, fat substitution and reactive myofibrosis, a major pathobiochemical hallmark of X-linked muscular dystrophy is represented by the chronic influx of calcium ions through the damaged plasmalemma in conjunction with abnormal intracellular calcium fluxes and buffering. Impaired calcium handling proteins should therefore be included in an improved biomarker signature of Duchenne muscular dystrophy.

Cytokine Pathways in Cardiac Dysfunction following Burn Injury and Changes in Genome Expression

In 2016, an estimated 486,000 individuals sustained burn injuries requiring medical attention. Severe burn injuries lead to a persistent, hyperinflammatory response that may last up to 2 years. The persistent release of inflammatory mediators contributes to end-organ dysfunction and changes in genome expression. Burn-induced cardiac dysfunction may lead to heart failure and changes in cardiac remodeling. Cytokines promote the inflammatory cascade and promulgate mechanisms resulting in cardiac dysfunction. Here, we review the mechanisms by which TNFα, IL-1 beta, IL-6, and IL-10 cause cardiac dysfunction in post-burn injuries. We additionally review changes in the cytokine transcriptome caused by inflammation and burn injuries.

Impact of aging and oxidative stress on specific components of excitation contraction coupling in regulating force generation

Muscle weakness associated with sarcopenia is a major contributor to reduced health span and quality of life in the elderly. However, the underlying mechanisms of muscle weakness in aging are not fully defined. We investigated the effect of oxidative stress and aging on specific molecular mechanisms involved in muscle force production in mice and skinned permeabilized single fibers in mice lacking the antioxidant enzyme CuZnSod (Sod1KO) and in aging (24-month-old) wild-type mice. Loss of muscle strength occurs in both models, potentially because of reduced membrane excitability with altered NKA signaling and RyR stability, decreased fiber Ca²⁺ sensitivity and suppressed SERCA activity via modification of the Cys⁶⁷⁴ residue, dysregulated SR and cytosolic Ca²⁺ homeostasis, and impaired mitochondrial Ca²⁺ buffering and respiration. Our results provide a better understanding of the specific impacts of aging and oxidative stress on mechanisms related to muscle weakness that may point to future interventions for countering muscle weakness.

Variations in cost of transport and their ecological consequences: a review

Movement is essential in the ecology of most animals, and it typically consumes a large proportion of individual energy budgets. Environmental conditions modulate the energetic cost of movement (cost of transport, COT), and there are pronounced differences in COT between individuals within species and across species. Differences in morphology affect COT, but the physiological mechanisms underlying variation in COT remain unresolved. Candidates include mitochondrial efficiency and the efficiency of muscle contraction-relaxation dynamics. Animals can offset increased COT behaviourally by adjusting movement rate and habitat selection. Here, we review the theory underlying COT and the impact of environmental changes on COT. Increasing temperatures, in particular, increase COT and its variability between individuals. Thermal acclimation and exercise can affect COT, but this is not consistent across taxa. Anthropogenic pollutants can increase COT, although few chemical pollutants have been investigated. Ecologically, COT may modify the allocation of energy to different fitness-related functions, and thereby influence fitness of individuals, and the dynamics of animal groups and communities. Future research should consider the effects of multiple stressors on COT, including a broader range of pollutants, the underlying mechanisms of COT and experimental quantifications of potential COT-induced allocation trade-offs.

Identification of Potential Muscle Biomarkers in McArdle Disease: Insights from Muscle Proteome Analysis

Glycogen storage disease type V (GSDV, McArdle disease) is a rare genetic myopathy caused by deficiency of the muscle isoform of glycogen phosphorylase (PYGM). This results in a block in the use of muscle glycogen as an energetic substrate, with subsequent exercise intolerance. The pathobiology of GSDV is still not fully understood, especially with regard to some features such as persistent muscle damage (i.e., even without prior exercise). We aimed at identifying potential muscle protein biomarkers of GSDV by analyzing the muscle proteome and the molecular networks associated with muscle dysfunction in these patients. Muscle biopsies from eight patients and eight healthy controls showing none of the features of McArdle disease, such as frequent contractures and persistent muscle damage, were studied by quantitative protein expression using isobaric tags for relative and absolute quantitation (iTRAQ) followed by artificial neuronal networks (ANNs) and topology analysis. Protein candidate validation was performed by Western blot. Several proteins predominantly involved in the process of muscle contraction and/or calcium homeostasis, such as myosin, sarcoplasmic/endoplasmic reticulum calcium ATPase 1, tropomyosin alpha-1 chain, troponin isoforms, and alpha-actinin-3, showed significantly lower expression levels in the muscle of GSDV patients. These proteins could be potential biomarkers of the persistent muscle damage in the absence of prior exertion reported in GSDV patients. Further studies are needed to elucidate the molecular mechanisms by which PYGM controls the expression of these proteins.

Patient-Specific iPSCs-Based Models of Neurodegenerative Diseases: Focus on Aberrant Calcium Signaling

The development of cell reprogramming technologies became a breakthrough in the creation of new models of human diseases, including neurodegenerative pathologies. The iPSCs-based models allow for the studying of both hereditary and sporadic cases of pathologies and produce deep insight into the molecular mechanisms underlying neurodegeneration. The use of the cells most vulnerable to a particular pathology makes it possible to identify specific pathological mechanisms and greatly facilitates the task of selecting the most effective drugs. To date, a large number of studies on patient-specific models of neurodegenerative diseases has been accumulated. In this review, we focused on the alterations of such a ubiquitous and important intracellular regulatory pathway as calcium signaling. Here, we reviewed and analyzed the data obtained from iPSCs-based models of different neurodegenerative disorders that demonstrated aberrant calcium signaling.