The Link between Mitochondrial Dysfunction and Sarcopenia: An Update Focusing on the Role of Pyruvate Dehydrogenase Kinase 4

FOXK2 in skeletal muscle development: a new pathogenic gene for congenital myopathy with ptosis

Congenital ptosis, a genetic disorder involving levator palpebrae muscle dysfunction, is often associated with congenital myopathy. The genetic causes of this condition remain poorly understood. In this study, we identified FOXK2 mutations in five pedigrees with congenital myopathy and ptosis through whole exome sequencing and Sanger sequencing. Zebrafish with foxk2 deficiency exhibited underdeveloped skeletal muscles and reduced mobility, while mice with Foxk2 deletion in skeletal muscle stem cells (MuSCs) showed generalized skeletal muscle abnormalities. Further analysis revealed that FOXK2 deficiency impaired myogenic differentiation in C2C12 cells and disrupted mitochondrial homeostasis in both mouse MuSCs and C2C12 cells. Rescue experiments confirmed the loss-of-function effects of FOXK2 mutation. Coenzyme Q10 treatment improved mitochondrial function and alleviated skeletal muscle development defects in Foxk2-deficient mice. Preliminary omics analysis suggested FOXK2 directly regulates the expression of mitochondrial function-related genes by modulating chromatin accessibility at its binding sites. Our study identifies FOXK2 as a novel pathogenic gene for congenital myopathy with ptosis and highlights its essential role in skeletal muscle development and mitochondrial homeostasis, offering insights for potential diagnostics and therapies.

Unraveling the Metabolic Pathways Between Metabolic-Associated Fatty Liver Disease (MAFLD) and Sarcopenia

Metabolic-Associated Fatty Liver Disease (MAFLD) is a public health concern that is constantly expanding, with a fast-growing prevalence, and it affects about a quarter of the world's population. This condition is a significant risk factor for cardiovascular, hepatic, and oncologic diseases, such as hypertension, hepatoma, and atherosclerosis. Sarcopenia was long considered to be an aging-related syndrome, but today, it is acknowledged to be secondarily related to chronic diseases such as metabolic syndrome, cardiovascular conditions, and liver diseases, among other comorbidities associated with insulin resistance and chronic inflammation, besides inactivity and poor nutrition. The physiopathology involving MAFLD and sarcopenia has still not been solved. Inflammation, oxidative stress, mitochondrial dysfunction, and insulin resistance seem to be some of the keys to this relationship since this hormone target is mainly the skeletal muscle. This review aimed to comprehensively discuss the main metabolic and physiological pathways involved in these conditions. MAFLD and sarcopenia are interconnected by a complex network of pathophysiological mechanisms, such as insulin resistance, skeletal muscle tissue production capacity, chronic inflammatory state, oxidative stress, and mitochondrial dysfunction, which are the main contributors to this relationship. In addition, in a clinical analysis, patients with sarcopenia and MAFLD manifest more severe hepatitis fibrosis when compared to patients with only MAFLD. These patients, with both disorders, also present clinical improvement in their MAFLD when treated for sarcopenia, reinforcing the association between them. Lifestyle changes accompanied by non-pharmacological interventions, such as dietary therapy and increased physical activity, undoubtedly improve this scenario.

Renometabolic disorder in experimental rat model of polycystic ovarian syndrome is reversed by acetate-mediated inhibition of pyruvate dehydrogenase kinase 4

BACKGROUND

Chronic Kidney disorders is a global public health problem, including in women with polycystic ovarian syndrome (PCOS), and is characterized by renal fibrosis, nephrotoxicity and glomerulonephritis, which increases the possibility of renal failure and organ transplant. Pyruvate dehydrogenase kinase 4 (PDK4) has been implicated in mitochondria dysfunction, contributing to metabolic dysregulation in different organs, including kidney. Studies have shown that short chain fatty acids, particularly acetate, alleviates metabolic alterations in experimental models. Hence, the present study investigated the therapeutic potential of acetate on renometabolic disorders associated with experimental PCOS model. The study in addition elucidates the probable involvement of PDK4 in PCOS-associated renometabolic disorders.

METHODS

Eight-week-old nulliparous female Wistar rats were randomly allotted into four groups (n = 5). Letrozole (1 mg/kg bw) was used to induce PCOS for 3 weeks. Thereafter, acetate (200 mg/kg bw) was administered for 6 weeks, uninterruptedly. Biochemical parameters from the plasma and renal tissue, as well as histology of ovaries were performed with appropriate methods.

RESULTS

Experimental PCOS rats were characterized with elevated circulating testosterone and the presence of multiple ovarian cysts. In addition, rat with PCOS also manifested insulin resistance, increased plasma urea and creatinine levels, increased renal Gamma glutamyl transferase (GGT), malondialdehyde (MDA), Nuclear factor -kappa B (NF-kB), Tumor necrosis factor -alpha (TNF-a), Transforming growth factor -beta 1 (TGF-B1), caspase-6, Histone deacetylase 2 (HDAC2), while a decrease in glucose-6 phosphate dehydrogenase (G6PD), reduced glutathione (GSH), renal nitric oxide (NO) and endothelial nitric oxide synthesis (eNOS), when compared with animals in the control group. These were associated with elevated level of PDK4 in the renal tissue. However, administration of acetate ameliorates these renal/metabolic abnormalities.

CONCLUSION

Altogether, the results from the present study suggests that acetate ameliorates renal dysfunction in PCOS via downregulation of PDK4.

Dipalmitoylphosphatidylcholine Lipid Vesicles for Delivering HMB, NMN, and L-Leucine in Sarcopenia Therapy

Sarcopenia, characterized by the degeneration of skeletal muscle tissue, has emerged as a significant concern in recent years. This increased awareness stems from advances in research focusing on elderly patients, which have revealed correlations between aging mechanisms and muscle degeneration, beyond the mere fact that tissues age and deteriorate over time. Consequently, the present study aims to address sarcopenia by developing and evaluating DPPC lipid vesicles that encapsulate three distinct drugs: HMB, NMN, and L-Leucine. These drugs are specifically selected for their properties, which facilitate effective interaction with the affected muscle tissue, thereby promoting desired therapeutic effects. Preliminary physicochemical analyses indicate the successful formation of spherical lipid vesicles, characterized by nanometric dimensions and stable membrane integrity. The biological investigations aimed to highlight the potential of DPPC lipid vesicles encapsulating HMB, NMN, and L-Leucine to alleviate sarcopenia-induced cytotoxicity and oxidative stress. Through a comparative evaluation of the three drug formulations, we demonstrate that drug-loaded DPPC vesicles effectively mitigate oxidative damage, preserve mitochondrial function, and maintain cytoskeletal integrity in H2O2-induced C2C12 myotubes, with HMB-loaded vesicles showing the strongest protective effects against muscle degeneration. These findings underscore the therapeutic potential of DPPC-based controlled release systems for sarcopenia treatment and highlight the need for further investigations into their mechanistic role in muscle preservation.

Near Infrared-Mediated Intracellular NADH Delivery Strengthens Mitochondrial Function and Stability in Muscle Dysfunction Model

Mitochondrial transfer emerges as a promising therapy for the restoration of mitochondrial function in damaged cells, mainly due to its limited immunogenicity. However, isolated mitochondria rapidly lose function because they produce little energy outside cells. Therefore, this study investigates whether near infrared (NIR)-mediated nicotinamide adenine dinucleotide (NADH) pre-treatment enhances mitochondrial function and stability in mitochondria-donor cells prior to transplantation. Clinical applications of NADH, an essential electron donor in the oxidative phosphorylation process, are restricted due to the limited cellular uptake of NADH. To address this, a photo-mediated method optimizes direct NADH delivery into cells and increases NADH absorption. L6 cells treated with NADH and irradiated with NIR enhanced NADH uptake, significantly improving mitochondrial energy production and function. Importantly, the improved functional characteristics of the mitochondria are maintained even after isolation from cells. Primed mitochondria, i.e., those enhanced by NIR-mediated NADH uptake (P-MT), are encapsulated in fusogenic liposomes and delivered into muscle cells with mitochondrial dysfunction. Compared to conventional mitochondria, P-MT mitochondria promote greater mitochondrial recovery and muscle regeneration. These findings suggest that NIR-mediated NADH delivery is an effective strategy for improving mitochondrial function, and has the potential to lead to novel treatments for mitochondrial disorders and muscle degeneration.

Type 3 diabetes and metabolic reprogramming of brain neurons: causes and therapeutic strategies

Abnormal glucose metabolism inevitably disrupts normal neuronal function, a phenomenon widely observed in Alzheimer's disease (AD). Investigating the mechanisms of metabolic adaptation during disease progression has become a central focus of research. Considering that impaired glucose metabolism is closely related to decreased insulin signaling and insulin resistance, a new concept "type 3 diabetes mellitus (T3DM)" has been coined. T3DM specifically refers to the brain's neurons becoming unresponsive to insulin, underscoring the strong link between diabetes and AD. Recent studies reveal that during brain insulin resistance, neurons exhibit mitochondrial dysfunction, reduced glucose metabolism, and elevated lactate levels. These findings suggest that impaired insulin signaling caused by T3DM may lead to a compensatory metabolic shift in neurons toward glycolysis. Consequently, this review aims to explore the underlying causes of T3DM and elucidate how insulin resistance drives metabolic reprogramming in neurons during AD progression. Additionally, it highlights therapeutic strategies targeting insulin sensitivity and mitochondrial function as promising avenues for the successful development of AD treatments.

The Association Between Low Muscle Mass and the Risk of Depressive Symptoms: A Cross-Sectional Study Based on the Chinese Longitudinal Health Longevity Survey (CLHLS)

BACKGROUND

Many studies have shown a strong link between sarcopenia and depression, and low muscle mass (LMM) is an important component in the diagnosis of sarcopenia; however, there have been no studies on the relationship between LMM and depressive symptoms in the Chinese elderly population. To estimate the potential relationship between LMM and depressive symptoms among older adults, a cross-sectional analysis was conducted utilizing data from the Chinese Longitudinal Health Longevity Survey (CLHLS).

METHOD

The study sample comprised 11,711 individuals aged 65 years or older (mean age 83.0 ± 10.9) from the CLHLS database in 2018. We used the corrected appendicular skeletal muscle mass (ASM) prediction formula to assess muscle mass and the 10-item Center for Epidemiological Studies-Depression Scale (CES-D-10) to assess depressive symptoms. A multivariate logistic regression model and restricted cubic spline (RCS) curves were employed to investigate the association between LMM and depressive symptoms.

RESULTS

The study findings revealed a 1.16-fold higher risk of depressive symptoms in the LMM group compared to the control group (adjusted odds ratio [aOR]: 1.16, 95% confidence intervals [95% CI]: 1.05-1.29, p < 0.001). Furthermore, for every one-point decrease in LMM score below 7.87, the risk of depressive symptoms increased by 8%, with statistical significance. However, when the LMM score was greater than or equal to 7.87, the decrease in the LMM score did not significantly increase the risk of depressive symptoms.

CONCLUSION

Our study suggests LMM is a risk factor for depressive symptoms in the elderly Chinese population, and within a certain range, the risk of depressive symptoms increases as the LMM score decreases. Physical exercise may be an effective strategy to maintain optimal muscle mass and help the mental health of the elderly.

The association of body roundness index and body mass index with frailty and all-cause mortality: a study from the population aged 40 and above in the United States

BACKGROUND

The relationship between body roundness index (BRI), a new obesity index, and frailty has not been established. This study aims to compare the associations of traditional obesity index body mass index (BMI) and BRI with frailty and the risk of all-cause mortality.

METHODS

The clinical data of 15,157 participants over 40 years old from the National Health and Nutrition Examination Survey (NHANES) from 2003 to 2018 were analyzed. Based on weighted logistic regression, COX regression and restricted cubic spline, the associations of BRI and BMI with the odds of frailty and the risk of all-cause mortality were estimated. The receiver operating characteristic curve (ROC) and concordance index were used to evaluate the ability of BRI and BMI to predict frailty and survival.

RESULTS

Weighted logistic regression showed that the odds of frailty showed a trend of increasing with the increase of BRI and BMI (P for trend < 0.0001, respectively). After adjusting for all confounding factors, the association between BRI and frailty was stronger (OR: 1.20, 95% CI: 1.13-1.27, P < 0.0001), and the association between BMI and frailty was slightly weaker (OR: 1.14, 95% CI: 1.08-1.21, P < 0.0001). ROC showed that the area under the curve (AUC) of BRI for predicting frailty was 0.628, while the AUC of BMI was 0.603, and the difference between the two was significant (PDeLong < 0.001). In addition, in survival analysis, BRI and BMI showed a significant U-shaped association with the risk of all-cause mortality. Piecewise regression based on the inflection point shows that when BRI < 7.33, an increase in BRI reduces the risk of all-cause mortality (HR: 0.85, 95% CI: 0.78-0.92, P < 0.0001), while when BRI ≥ 7.33, an increase in BRI increases the risk of all-cause mortality (HR: 1.19, 95% CI: 1.03-1.38, P = 0.02); when BMI < 33.57, an increase in BMI reduces the risk of all-cause mortality (HR: 0.84, 95% CI: 0.78-0.91, P < 0.0001), and when BMI ≥ 33.57, an increase in BRI increases the risk of all-cause mortality (HR: 1.18, 95% CI: 1.04-1.34, P = 0.01). Moreover, the time-dependent c-index curve showed that the ability of BRI to predict the risk of all-cause mortality in frail people was comparable to that of BMI.

CONCLUSION

In the American population over 40 years old, both BRI and BMI are independently and positively associated with frailty. Moreover, BRI has a stronger ability to predict frailty than BMI. In addition, both BRI and BMI have a U-shaped association with the risk of all-cause mortality in frail individuals, and the two have comparable abilities to predict the risk of all-cause mortality.

Could Sarcopenia Be Related to Chemotherapy in Gastrointestinal Cancer? A Cross-Sectional Study Including Comprehensive Geriatric Assessment

Background: Sarcopenia, which is characterized by the progressive loss of skeletal muscle mass, strength, and functionality, adversely affects cancer outcomes. This study aims to evaluate the development and progression of sarcopenia in patients with gastrointestinal cancer undergoing chemotherapy and its impact on comprehensive geriatric assessment outcomes in older participants. Methods: This cross-sectional study included 351 gastrointestinal cancer patients from October 2018 to December 2019. Pre- and post-chemotherapy measurements were taken for 243 participants. Sarcopenia was assessed using EWGSOP-2 criteria, including muscle mass, strength, and performance evaluations. A comprehensive geriatric assessment was conducted for patients aged 65 years and older. Results: The median age of participants was 57.84 years, with 31.7% being female and 29.2% being aged 65 years or older. A significant increase in the prevalence of sarcopenia post-chemotherapy was observed. The factors significantly associated with sarcopenia included low hand grip strength (-0.264; p < 0.001) and slow gait speed (0.222; p = 0.007). The muscle mass and albumin levels of older patients declined significantly post-treatment. Conclusions: This study highlights a strong association between chemotherapy and sarcopenia in gastrointestinal cancer patients, emphasizing the need for early detection and tailored interventions. Comprehensive geriatric assessments can provide critical insights that improve patient outcomes during chemotherapy.

Repairing muscle with broccoli-derived sulforaphane: A preclinical evaluation for the treatment of mitochondrial myopathies

Skeletal muscle health relies on the production of adenosine triphosphate (ATP) in the mitochondria. ATP production is accompanied by oxidative phosphorylation, which generates reactive oxygen species (ROS). When there is an imbalance in ROS levels, oxidative stress and subsequent mitochondrial dysfunction, mitochondrial myopathies including sarcopenia, chronic progressive external ophthalmoplegia, and proximal myopathy can result. Such incurable myopathies are characterised by aberrant metabolism, limited ATP production, and muscle atrophy. Broccoli-derived sulforaphane has emerged as a novel treatment for mitochondrial myopathies because of its antioxidant and anti-inflammatory properties. This review discusses preclinical studies that reveal sulforaphane's potential therapeutic benefits and limitations in treating mitochondrial myopathies.

Sodium Phenylbutyrate Attenuates Cisplatin-Induced Acute Kidney Injury Through Inhibition of Pyruvate Dehydrogenase Kinase 4

Background/Objectives: Cisplatin nephrotoxicity is a significant clinical issue, and currently, no approved drug exists to prevent cisplatin-induced acute kidney injury (AKI). This study investigated whether sodium phenylbutyrate (4-PBA), a chemical chaperone, can prevent cisplatin-induced AKI. Methods: Six consecutive days of intraperitoneal injections of 4-PBA were administered in a murine model before and after the cisplatin challenge. This study evaluated tubular injury, serum blood urea nitrogen (BUN) and creatinine levels, and inflammatory markers such as tumor necrosis factor-alpha (TNF-α) and intercellular adhesion molecule 1 (ICAM-1). Additionally, apoptosis, mitochondrial membrane potential, oxygen consumption ratio, and reactive oxygen species (ROS) were assessed in renal tubular cells. The expression levels of pyruvate dehydrogenase kinase 4 (Pdk4) were also analyzed. Results: 4-PBA prevented tubular injury and normalized serum BUN and creatinine levels. Inflammatory markers TNF-α and ICAM-1 were suppressed. In renal tubular cells, 4-PBA reduced apoptosis, restored mitochondrial membrane potential and oxygen consumption ratio, and reduced ROS production. Mechanistically, 4-PBA suppressed the expression of Pdk4, which is known to be induced during cisplatin-induced renal injury. The protective effect of 4-PBA was abolished in Pdk4-overexpressing renal tubular cells, indicating that the efficacy of 4-PBA partially depends on the suppression of Pdk4 expression. In cancer cells, 4-PBA did not interfere with the anti-cancer efficacy of cisplatin. Conclusions: These findings suggest that 4-PBA effectively prevents cisplatin-induced acute kidney injury by suppressing Pdk4.

Mitochondria in skeletal system-related diseases

Skeletal system-related diseases, such as osteoporosis, arthritis, osteosarcoma and sarcopenia, are becoming major public health concerns. These diseases are characterized by insidious progression, which seriously threatens patients' health and quality of life. Early diagnosis and prevention in high-risk populations can effectively prevent the deterioration of these patients. Mitochondria are essential organelles for maintaining the physiological activity of the skeletal system. Mitochondrial functions include contributing to the energy supply, modulating the Ca2+ concentration, maintaining redox balance and resisting the inflammatory response. They participate in the regulation of cellular behaviors and the responses of osteoblasts, osteoclasts, chondrocytes and myocytes to external stimuli. In this review, we describe the pathogenesis of skeletal system diseases, focusing on mitochondrial function. In addition to osteosarcoma, a characteristic of which is active mitochondrial metabolism, mitochondrial damage occurs during the development of other diseases. Impairment of mitochondria leads to an imbalance in osteogenesis and osteoclastogenesis in osteoporosis, cartilage degeneration and inflammatory infiltration in arthritis, and muscle atrophy and excitationcontraction coupling blockade in sarcopenia. Overactive mitochondrial metabolism promotes the proliferation and migration of osteosarcoma cells. The copy number of mitochondrial DNA and mitochondria-derived peptides can be potential biomarkers for the diagnosis of these disorders. High-risk factor detection combined with mitochondrial component detection contributes to the early detection of these diseases. Targeted mitochondrial intervention is an effective method for treating these patients. We analyzed skeletal system-related diseases from the perspective of mitochondria and provided new insights for their diagnosis, prevention and treatment by demonstrating the relationship between mitochondria and the skeletal system.

Incretin-Based Therapies: A Promising Approach for Modulating Oxidative Stress and Insulin Resistance in Sarcopenia

BACKGROUND

Recent studies have linked sarcopenia development to the hallmarks of diabetes, oxidative stress, and insulin resistance. The anti-oxidant and insulin sensitivityenhancing effects of incretin-based therapies may provide a promising option for the treatment of sarcopenia. This review aimed to unveil the role of oxidative stress and insulin resistance in the pathogenesis of sarcopenia and explore the potential benefits of incretin-based therapies in individuals with sarcopenia.

METHODS

PubMed, the Cochrane Library, and Google Scholar databases were searched by applying keywords relevant to the main topic, to identify articles that met our selection criteria.

RESULTS

Incretin-based therapies manifested anti-oxidant effects by increasing the anti-oxidant defense system and decreasing free radical generation or by indirectly minimizing glucotoxicity, which was mainly achieved by improving insulin signaling and glucose homeostasis. Likewise, these drugs exhibit insulin-sensitizing activities by increasing insulin secretion, transduction, and β-cell function or by reducing inflammation and lipotoxicity.

CONCLUSIONS

Incretin-based therapies, as modulators of oxidation and insulin resistance, may target the main pathophysiological factors of sarcopenia, thus providing a promising strategy for the treatment of this disease.

The MyoGravity project to study real microgravity effects on human muscle precursor cells and tissue

Microgravity (µG) experienced during space flights promotes adaptation in several astronauts' organs and tissues, with skeletal muscles being the most affected. In response to reduced gravitational loading, muscles (especially, lower limb and antigravity muscles) undergo progressive mass loss and alteration in metabolism, myofiber size, and composition. Skeletal muscle precursor cells (MPCs), also known as satellite cells, are responsible for the growth and maintenance of muscle mass in adult life as well as for muscle regeneration following damage and may have a major role in µG-induced muscle wasting. Despite the great relevance for astronaut health, very few data are available about the effects of real µG on human muscles. Based on the MyoGravity project, this study aimed to analyze: (i) the cellular and transcriptional alterations induced by real µG in human MPCs (huMPCs) and (ii) the response of human skeletal muscle to normal gravitational loading after prolonged exposure to µG. We evaluated the transcriptomic changes induced by µG on board the International Space Station (ISS) in differentiating huMPCs isolated from Vastus lateralis muscle biopsies of a pre-flight astronaut and an age- and sex-matched volunteer, in comparison with the same cells cultured on the ground in standard gravity (1×g) conditions. We found that huMPCs differentiated under real µG conditions showed: (i) upregulation of genes related to cell adhesion, plasma membrane components, and ion transport; (ii) strong downregulation of genes related to the muscle contraction machinery and sarcomere organization; and (iii) downregulation of muscle-specific microRNAs (myomiRs). Moreover, we had the unique opportunity to analyze huMPCs and skeletal muscle tissue of the same astronaut before and 30 h after a long-duration space flight on board the ISS. Prolonged exposure to real µG strongly affected the biology and functionality of the astronaut's satellite cells, which showed a dramatic reduction of responsiveness to activating stimuli and proliferation rate, morphological changes, and almost inability to fuse into myotubes. RNA-Seq analysis of post- vs. pre-flight muscle tissue showed that genes involved in muscle structure and remodeling are promptly activated after landing following a long-duration space mission. Conversely, genes involved in the myelination process or synapse and neuromuscular junction organization appeared downregulated. Although we have investigated only one astronaut, these results point to a prompt readaptation of the skeletal muscle mechanical components to the normal gravitational loading, but the inability to rapidly recover the physiological muscle myelination/innervation pattern after landing from a long-duration space flight. Together with the persistent functional deficit observed in the astronaut's satellite cells after prolonged exposure to real µG, these results lead us to hypothesize that a condition of inefficient regeneration is likely to occur in the muscles of post-flight astronauts following damage.

Dichloroacetate Prevents Sepsis Associated Encephalopathy by Inhibiting Microglia Pyroptosis through PDK4/NLRP3

Dichloroacetate (DCA), a pyruvate dehydrogenase kinase inhibitor, is often used to treat lactic acidosis and malignant tumors. Increasing studies have shown that DCA has neuroprotective effects. Here, we explored the role and mechanism of DCA in Sepsis associated encephalopathy (SAE). Single-cell analysis was used to determine the important role of PDK4 in SAE and identify the cell type. GO and GSEA analysis were used to determine the correlation between DCA and pyroptosis. Through LPS + ATP stimulation, a microglia pyroptosis model was established to observe the expression level of intracellular pyroptosis-related proteins under DCA intervention, and further detect the changes in intracellular ROS and JC-1. Additionally, a co-culture environment of microglia and neuron was simply constructed to evaluate the effect of DCA on activated microglia-mediated neuronal apoptosis. Finally, Novel object recognition test and the Morris water maze were used to explore the effect of DCA on cognitive function in mice from different groups after intervention. Based on the above experiments, this study concludes that DCA can improve the ratio of peripheral and central M1 macrophages, inhibit NLRP3-mediated pyroptosis through ROS and mitochondrial membrane potential (MMP). DCA can reduce neuron death caused by SAE and improve cognitive function in LPS mice. In SAE, DCA may be a potential candidate drug for the treatment of microglia-mediated neuroinflammation.

Inhibition of Pyruvate Dehydrogenase Kinase 4 Protects Cardiomyocytes from lipopolysaccharide-Induced Mitochondrial Damage by Reducing Lactate Accumulation

Mitochondrial dysfunction is considered one of the major pathogenic mechanisms of sepsis-induced cardiomyopathy (SIC). Pyruvate dehydrogenase kinase 4 (PDK4), a key regulator of mitochondrial metabolism, is essential for maintaining mitochondrial function. However, its specific role in SIC remains unclear. To investigate this, we established an in vitro model of septic cardiomyopathy using lipopolysaccharide (LPS)-induced H9C2 cardiomyocytes. Our study revealed a significant increase in PDK4 expression in LPS-treated H9C2 cardiomyocytes. Inhibiting PDK4 with dichloroacetic acid (DCA) improved cell survival, reduced intracellular lipid accumulation and calcium overload, and restored mitochondrial structure and respiratory capacity while decreasing lactate accumulation. Similarly, Oxamate, a lactate dehydrogenase inhibitor, exhibited similar effects to DCA in LPS-treated H9C2 cardiomyocytes. To further validate whether PDK4 causes cardiomyocyte and mitochondrial damage in SIC by promoting lactate production, we upregulated PDK4 expression using PDK4-overexpressing lentivirus in H9C2 cardiomyocytes. This resulted in elevated lactate levels, impaired mitochondrial structure, and reduced mitochondrial respiratory capacity. However, inhibiting lactate production reversed the mitochondrial dysfunction caused by PDK4 upregulation. In conclusion, our study highlights the pathogenic role of PDK4 in LPS-induced cardiomyocyte and mitochondrial damage by promoting lactate production. Therefore, targeting PDK4 and its downstream product lactate may serve as promising therapeutic approaches for treating SIC.

Resveratrol and Vitamin D: Eclectic Molecules Promoting Mitochondrial Health in Sarcopenia

Sarcopenia refers to the progressive loss and atrophy of skeletal muscle function, often associated with aging or secondary to conditions involving systemic inflammation, oxidative stress, and mitochondrial dysfunction. Recent evidence indicates that skeletal muscle function is not only influenced by physical, environmental, and genetic factors but is also significantly impacted by nutritional deficiencies. Natural compounds with antioxidant properties, such as resveratrol and vitamin D, have shown promise in preventing mitochondrial dysfunction in skeletal muscle cells. These antioxidants can slow down muscle atrophy by regulating mitochondrial functions and neuromuscular junctions. This review provides an overview of the molecular mechanisms leading to skeletal muscle atrophy and summarizes recent advances in using resveratrol and vitamin D supplementation for its prevention and treatment. Understanding these molecular mechanisms and implementing combined interventions can optimize treatment outcomes, ensure muscle function recovery, and improve the quality of life for patients.

Comparison between single-muscle evaluation and cross-sectional area muscle evaluation for predicting the prognosis in patients with oral squamous cell carcinoma: a retrospective cohort study

Introduction

The most effective method of assessing sarcopenia has yet to be determined, whether by single muscle or by whole muscle segmentation. The purpose of this study was to compare the prognostic value of these two methods using computed tomography (CT) images in patients with oral squamous cell carcinoma (OSCC).

Materials and methods

Sex- and age-adjusted Cox proportional hazards models were employed for each parameter of sarcopenia related to overall survival, disease-free survival, and disease-specific survival. Harrell's concordance index was calculated for each model to assess discriminatory power.

Results

In this study including 165 patients, a significant correlation was found between the CT-based assessment of individual muscles and their cross-sectional area. Single muscle assessments showed slightly higher discriminatory power in survival outcomes compared to whole muscle assessments, but the difference was not statistically significant, as indicated by overlapping confidence intervals for the C-index between assessments. To further validate our measurements, we classified patients into two groups based on intramuscular adipose tissue content (P-IMAC) of the spinous process muscle. Analysis showed that the higher the P-IMAC value, the poorer the survival outcome.

Conclusion

Our findings indicate a slight advantage of single-muscle over whole-muscle assessment in prognostic evaluation, but the difference between the two methods is not conclusive. Both assessment methods provide valuable prognostic information for patients with OSCC, and further studies involving larger, independent cohorts are needed to clarify the potential advantage of one method over the other in the prognostic assessment of sarcopenia in OSCC.

Effect of resistance training plus enriched probiotic supplement on sestrin2, oxidative stress, and mitophagy markers in elderly male Wistar rats

This study aimed to determine the effects of resistance training combined with a probiotic supplement enriched with vitamin D and leucine on sestrin2, oxidative stress, antioxidant defense, and mitophagy markers in aged Wistar rats. Thirty-five male rats were randomly assigned to two age groups (old with 18-24 months of age and young with 8-12 weeks of age) and then divided into five groups, including (1) old control (OC: n = 5 + 2 for reserve in all groups), (2) young control (YC: n = 5), (3) old resistance training (OR: n = 5), (4) old resistance training plus supplement (ORS: n = 5), and old supplement group (OS: n = 5). Training groups performed ladder climbing resistance training 3 times per week for 8 weeks. Training intensity was inserted progressively, with values equal to 65, 75, and 85, determining rats' maximal carrying load capacity. Each animal made 5 to 8 climbs in each training session, and the time of each climb was between 12 and 15 s, although the time was not the subject of the evaluation, and the climbing pattern was different in the animals. Old resistance plus supplement and old supplement groups received 1 ml of supplement 5 times per week by oral gavage in addition to standard feeding, 1 to 2 h post training sessions. Forty-eight hours after the end of the training program, 3 ml of blood samples were taken, and all rats were then sacrificed to achieve muscle samples. After 8 weeks of training, total antioxidant capacity and superoxide dismutase activity levels increased in both interventions. A synergistic effect of supplement with resistance training was observed for total antioxidant capacity, superoxide dismutase, and PTEN-induced kinase 1. Sestrin 2 decreased in intervention groups. These results suggest that resistance training plus supplement can boost antioxidant defense and mitophagy while potentially decreasing muscle strength loss.

Metabolic clues to aging: exploring the role of circulating metabolites in frailty, sarcopenia and vascular aging related traits and diseases

Background: Physical weakness and cardiovascular risk increase significantly with age, but the underlying biological mechanisms remain largely unknown. This study aims to reveal the causal effect of circulating metabolites on frailty, sarcopenia and vascular aging related traits and diseases through a two-sample Mendelian Randomization (MR) analysis. Methods: Exposures were 486 metabolites analyzed in a genome-wide association study (GWAS), while outcomes included frailty, sarcopenia, arterial stiffness, atherosclerosis, peripheral vascular disease (PAD) and aortic aneurysm. Primary causal estimates were calculated using the inverse-variance weighted (IVW) method. Methods including MR Egger, weighted median, Q-test, and leave-one-out analysis were used for the sensitive analysis. Results: A total of 125 suggestive causative associations between metabolites and outcomes were identified. Seven strong causal links were ultimately identified between six metabolites (kynurenine, pentadecanoate (15:0), 1-arachidonoylglycerophosphocholine, androsterone sulfate, glycine and mannose) and three diseases (sarcopenia, PAD and atherosclerosis). Besides, metabolic pathway analysis identified 13 significant metabolic pathways in 6 age-related diseases. Furthermore, the metabolite-gene interaction networks were constructed. Conclusion: Our research suggested new evidence of the relationship between identified metabolites and 6 age-related diseases, which may hold promise as valuable biomarkers.

Unraveling the causes of sarcopenia: Roles of neuromuscular junction impairment and mitochondrial dysfunction

Sarcopenia is a systemic skeletal muscle disease characterized by a decline in skeletal muscle mass and function. Originally defined as an age-associated condition, sarcopenia presently also encompasses muscular atrophy due to various pathological factors, such as intensive care unit-acquired weakness, inactivity, and malnutrition. The exact pathogenesis of sarcopenia is still unknown; herein, we review the pathological roles of the neuromuscular junction and mitochondria in this condition. Sarcopenia is caused by complex and interdependent pathophysiological mechanisms, including aging, neuromuscular junction impairment, mitochondrial dysfunction, insulin resistance, lipotoxicity, endocrine factors, oxidative stress, and inflammation. Among these, neuromuscular junction instability and mitochondrial dysfunction are particularly significant. Dysfunction in neuromuscular junction can lead to muscle weakness or paralysis. Mitochondria, which are plentiful in neurons and muscle fibers, play an important role in neuromuscular junction transmission. Therefore, impairments in both mitochondria and neuromuscular junction may be one of the key pathophysiological mechanisms leading to sarcopenia. Moreover, this article explores the structural and functional alterations in the neuromuscular junction and mitochondria in sarcopenia, suggesting that a deeper understanding of these changes could provide valuable insights for the prevention or treatment of sarcopenia.

Neuroprotective Effects and Therapeutic Potential of Dichloroacetate: Targeting Metabolic Disorders in Nervous System Diseases

Dichloroacetate (DCA) is an investigational drug used to treat lactic acidosis and malignant tumours. It works by inhibiting pyruvate dehydrogenase kinase and increasing the rate of glucose oxidation. Some studies have documented the neuroprotective benefits of DCA. By reviewing these studies, this paper shows that DCA has multiple pharmacological activities, including regulating metabolism, ameliorating oxidative stress, attenuating neuroinflammation, inhibiting apoptosis, decreasing autophagy, protecting the blood‒brain barrier, improving the function of endothelial progenitor cells, improving mitochondrial dynamics, and decreasing amyloid β-protein. In addition, DCA inhibits the enzyme that metabolizes it, which leads to peripheral neurotoxicity due to drug accumulation that may be solved by individualized drug delivery and nanovesicle delivery. In summary, in this review, we analyse the mechanisms of neuroprotection by DCA in different diseases and discuss the causes of and solutions to its adverse effects.