7β-Hydroxycholesterol and 7-ketocholesterol: New oxidative stress biomarkers of sarcopenia inducing cytotoxic effects on myoblasts and myotubes

Oxysterols, age-related-diseases and nutritherapy: Focus on 7-ketocholesterol and 7β-hydroxycholesterol

Age-related diseases are often associated with a disruption of RedOx balance that can lead to lipid peroxidation with the formation of oxysterols, especially those oxidized on carbon-7: 7-ketocholesterol (also known as 7-oxo-cholesterol) and 7β-hydroxycholesterol. Like cholesterol, these oxysterols have 27 carbons, they are composed of a sterane nucleus and have a hydroxyl function in position 3. The oxysterols 7-ketocholesterol and 7β-hydroxycholesterol are mainly formed by cholesterol autoxidation and are biomarkers of oxidative stress. These two oxysterols are frequently found at increased levels in the biological fluids (plasma, cerebrospinal fluid), tissues and/or organs (arterial wall, retina, brain) of patients with age-related diseases, especially cardiovascular diseases, neurodegenerative diseases (mainly Alzheimer's disease), ocular diseases (cataract, age-related macular degeneration), and sarcopenia. Depending on the cell type considered, 7-ketocholesterol and 7β-hydroxycholesterol induce either caspase- dependent or -independent types of cell death associated with mitochondrial and peroxisomal dysfunctions, autophagy and oxidative stress. The caspase dependent type of cell death associated with oxidative stress and autophagy is defined as oxiapoptophagy. These two oxysterols are also inducers of inflammation. These biological features associated with the toxicity of 7-ketocholesterol, and 7β-hydroxycholesterol are often observed in patients with age-related diseases, suggesting an involvement of these oxysterols in the pathophysiology of these disorders. The cytotoxic effects of 7-ketocholesterol and 7β-hydroxycholesterol are counteracted on different cell models by representative nutrients of the Mediterranean diet: ω3 and ω9 fatty acids, polyphenols, and tocopherols. There are also evidences, mainly in cardiovascular diseases, of the benefits of α-tocopherol and phenolic compounds. These in vitro and in vivo observations on 7-ketocholesterol and 7β-hydroxycholesterol, which are frequently increased in age-related diseases, reinforce the interest of nutritherapeutic treatments to prevent and/or cure age-related diseases currently without effective therapies.

Decoding the Impact of Theabrownin on Skeletal Muscle Function in Gestational Diabetic Offspring: Insights from Integrated Metabolome and Transcriptome Analysis

Gestational diabetes mellitus (GDM) often leads to long-term metabolic issues, including skeletal muscle dysfunction in the offspring, with traditional managements focusing solely on blood glucose regulation and not addressing muscle metabolic and structural changes. Theabrownin (TB), a polyphenol derived from Pu-erh tea, has known antioxidant and metabolic benefits, but its effects on skeletal muscle function in GDM offspring remain unclear. In this study, GDM model was induced in mice, and their offspring were treated by TB. Transcriptomic and metabolomic analyses identified key genes and metabolites involved in lipid metabolism, oxidative stress, and inflammation. TB treatment significantly improved lipid metabolism, reduced oxidative stress, and alleviated inflammation in skeletal muscle of GDM offspring. Key genes (Fabp3, Acot1, and Acot4) and metabolites (Palmitic acid, Oleic acid) were regulated by TB. Pathway analysis revealed that TB mitigates GDM-induced skeletal muscle dysfunction through modulation of the biosynthesis of unsaturated fatty acids. These findings highlight the potential of theabrownin (TB) as a therapeutic agent for improving skeletal muscle function in the offspring of GDM through modulation of lipid metabolism. Further investigation is needed to elucidate its mechanisms and evaluate long-term effects.

The Link Between Oxysterols and Gut Microbiota in the Co-Dysfunction of Cognition and Muscle

Background/Objectives: Alterations of oxysterols and gut microbiota have been recognized as indicators affecting mild cognitive impairment (MCI) and sarcopenia, respectively, whereas their association with co-dysfunction has not been investigated. Methods: In this study, a total of 1035 individuals were divided into Control (n = 264), MCI (n = 435), and MCI with possible sarcopenia (MPS, n = 336) groups. Cognition and muscle indexes, serum oxysterols, and gut microbiota were measured. Spearman's rank coefficients were calculated to determine their correlations. Results: Performances of global and multidimensional cognitive tests was successively worse in the Control, MCI, and MPS groups. Longer duration of five-time chair stand test, lower 6-meter walk speed, and handgrip strength were observed in the MPS group, along with increased 27-hydroxycholesterol (27-OHC) and 5α,6α-epoxycholesterol and decreased 5α-Cholest-8(14)-ene-3β,15α-diol (15-HC). Higher concentrations of amyloid precursor protein (APP), neurofilament, and C-terminal agrin fragment (CAF) were discovered in the MCI and MPS groups. The α-diversity of gut microbiota in the MCI and MPS group was remarkably decreased, followed by a shifted abundance of microbial taxa, such as Alistipes and Rikenellaceae. Multiple significant correlations were found between cognition and muscle indexes and with oxysterols. Conclusions: Our study indicates that oxysterols and gut microbiota are prominently involved in the co-dysfunction of cognition and muscle.

Impact of myosteatosis on prognosis in multiple myeloma patients: A subgroup analysis of 182 cases and development of a nomogram

Background

This study aims to explore the prognostic value of myosteatosis in multiple myeloma (MM) and to analyze the factors influencing myosteatosis.

Methods

A retrospective analysis was conducted on 182 patients treated for MM at our institution from 2009 to 2020 who underwent MRI examinations. The fatty infiltration rate (FIR) of the erector spinae and multifidus muscles at the L3 level was measured to assess the degree of myosteatosis. Patients were grouped based on fracture presence and median FIR, and group differences were compared, with P < 0.05 considered statistically significant. Survival and fractures were used as prognostic indicators, and regression analysis was performed to determine the impact of FIR on these outcomes in MM patients. The factors influencing FIR were analyzed, and the relationship between myosteatosis and MM prognosis was further analyzed within its sensitive subgroups. Finally, a nomogram based on FIR was established and validated.

Results

Significant differences were observed between the fracture and non-fracture groups in lactate dehydrogenase, serum phosphorus, visual analogue scale, oswestry disability index and FIR (P < 0.05). When patients were grouped based on the median FIR (28.89 %), there were significant differences in age, sex, body mass index (BMI), red blood cell (RBC) count, hemoglobin, hematocrit, albumin, visual analogue scale, oswestry disability index, and fracture incidence (P < 0.05). Univariate COX regression analysis indicated that myosteatosis had no significant impact on survival prognosis in MM patients (HR = 0.999, P = 0.852), with a log-rank test P value of 0.11 when grouped by the cut-off FIR value of 33.67 %. Multivariate logistic regression indicated that FIR is an independent predictor of fractures (OR = 1.054, P = 0.000). Multivariate linear regression revealed that age, sex, RBC count, and BMI are independent factors influencing FIR (P < 0.05). When not grouped, FIR's prediction of fractures showed no significant interaction with age, sex, RBC count, or BMI (P for interaction > 0.05). In subgroups with BMI ≥ 25 kg/m2 or RBC count > 3.68 × 10^12/L, FIR lost its predictive significance for fractures. The FIR nomogram model had a C-index of 0.777, and the calibration curve, decision curve analysis, and clinical impact curve all validated its effectiveness.

Conclusions

Myosteatosis characterized by FIR is not a reliable predictor of survival in MM patients but is effective in predicting fractures and is closely related to back pain and functional impairment. FIR is significantly associated with age, sex, RBC count, and BMI.

Lipid peroxidation and sarcopenia: molecular mechanisms and potential therapeutic approaches

Sarcopenia is an age-related condition characterized by the progressive loss of skeletal muscle mass and strength. With the global aging population, its incidence is rapidly increasing. Lipid peroxidation is a critical biochemical process that generates reactive oxygen species (ROS), leading to the destruction of muscle cell structure and function. It plays a pivotal role in the onset and progression of sarcopenia. This review summarizes the mechanisms by which lipid peroxidation contributes to sarcopenia, with a focus on its regulatory effects on cell membrane damage, mitochondrial dysfunction, and cell death. In addition, we discuss the protective role of antioxidant factors such as GPX4 (glutathione peroxidase 4) and antioxidant peptides like SS peptides in mitigating lipid peroxidation and delaying the progression of sarcopenia. Finally, the potential of various strategies, including natural compounds, supplements, natural extracts, and lifestyle interventions, in inhibiting lipid peroxidation and promoting muscle health is explored.

Pexophagy and Oxidative Stress: Focus on Peroxisomal Proteins and Reactive Oxygen Species (ROS) Signaling Pathways

Peroxisomes generate reactive oxygen species (ROS) and also play a role in protecting cells from the damaging effects of such radicals. Dysfunctional peroxisomes are recognized by receptors and degraded by a selective type of macroautophagy called pexophagy. Oxidative stress is one of the signals that activates pexophagy through multiple signaling pathways. Conversely, impaired pexophagy results in the accumulation of damaged peroxisomes, which in turn leads to elevated ROS levels and oxidative stress, resulting as cellular dysfunction and the progression of diseases such as neurodegeneration, cancer, and metabolic disorders. This review explores the molecular mechanisms driving pexophagy and its regulation by oxidative stress with a particular focus on ROS. This highlights the role of peroxisomal proteins and ROS-mediated signaling pathways in regulating pexophagy. In addition, emerging evidence suggests that the dysregulation of pexophagy is closely linked to neurological disorders, underscoring its potential as a therapeutic target. Understanding the intricate crosstalk between pexophagy and oxidative stress provides new insights into the maintenance of cellular homeostasis and offers promising directions for addressing neurological disorders that are tightly associated with pexophagy and oxidative stress.

Relationship of irisin and apelin levels with sarcopenia and body composition in community-dwelling older adults: a paired case-control study

Irisin and apelin levels continue to decrease with age, and although many previous studies have explored their association with sarcopenia and body composition, there is still a paucity of evidence relating to them in community-dwelling elderly populations. The aim of this study was to provide new evidence for the association of irisin and apelin with sarcopenia in older adults. This case-control study included 80 individuals with sarcopenia and 80 individuals without sarcopenia. The definition of sarcopenia was based on the Asian Working Group for Sarcopenia 2019 criteria. Plasma levels of irisin and apelin were measured using an enzyme-linked immunosorbent assay. Conditional logistic regression analysis was performed to estimate odds ratios (ORs) and 95% CIs. The sarcopenia group exhibited significantly lower levels of irisin (73.75 ± 30.97 ng/mL vs. 131.15 ± 88.38 ng/mL, p < 0.001) and apelin (21.51 ± 14.89 ng/mL vs. 27.87 ± 14.41 ng/mL, p = 0.007) compared to the control group. Increased levels of irisin (OR, 0.98, 95% CI, 0.97-0.99) and apelin (OR, 0.97, 95% CI, 0.95-0.99) were associated with a decreased risk of sarcopenia. In women, irisin was positively associated with body mass index, intracellular water (ICW), extracellular water (ECW), total water (TW), protein, mineral, fat, fat-free mass, skeletal muscle mass (SMM), percentage body fat, waist circumference, visceral fat area, and basal metabolic rate. Apelin was positively associated with ICW, ECW, TW, protein, and SMM (all p < 0.05). In men, positive correlations were found between irisin, apelin, and handgrip strength (all p < 0.05). Receiver operating characteristic analysis showed that irisin and apelin had moderate predictive power in identifying sarcopenia. Plasma irisin and apelin were lower than in controls in elderly patients with sarcopenia, and elevated levels of irisin and apelin were associated with a reduced risk of sarcopenia. In addition, irisin and apelin levels are associated with body composition and irisin showed a stronger ability to predict sarcopenia in women.

The association between non‑high‑density lipoprotein cholesterol to high‑density lipoprotein cholesterol ratio (NHHR) and low muscle mass in adults aged 20-59: a population-based study in the United States

BACKGROUND

The ratio between non-high-density lipoprotein cholesterol and high-density lipoprotein cholesterol (NHHR) is a reliable marker for assessing the risk linked to lipid metabolism disorders. Sarcopenia, characterized by age-related loss of muscle mass and strength/function, includes the assessment of muscle mass, muscle strength, and muscle-specific strength. However, research into NHHR's relationship with low muscle mass risk remains unexplored.

METHODS

Our study utilized a cross-sectional approach, examining data derived from the National Health and Nutrition Examination Survey (NHANES) from 2011 to 2018. Through multivariable linear and logistic regression, we investigated the relationships of the NHHR with muscle mass and low muscle mass. We visualized the results using smoothing curves and assessed threshold effects. We also performed various subgroup and sensitivity analyses.

RESULTS

This research encompassed 9,012 participants and demonstrated significant nonlinear associations between NHHR and ALMBMI or low muscle mass risk in a generalized additive model (GAM), pinpointing critical NHHR values (3.328 and 3.367) where changes in NHHR significantly impacted ALMBMI and low muscle mass risk.

CONCLUSIONS

The NHHR demonstrates a significant association with an increased risk of low muscle mass among middle-aged Americans. This ratio has potential as a predictive marker for low muscle mass. Further exploration of NHHR is expected to aid in advancing preventive and therapeutic measures for this condition.

Muscle-specific PGC-1α modulates mitochondrial oxidative stress in aged sarcopenia through regulating Nrf2

BACKGROUND

Aged sarcopenia is characterized by loss of skeletal muscle mass and strength, and mitochondrial dysregulation in skeletal myocyte is considered as a major factor. Here, we aimed to analyze the effects of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) on mitochondrial reactive oxygen species (ROS) and nuclear factor erythroid 2-related factor 2 (Nrf2) in aged skeletal muscles.

METHODS

C2C12 cells were stimulated by 50 μM 7β-hydroxycholesterol (7β-OHC) to observe the changes of cellular ROS, mitochondrial ROS, and expression of PGC-1α and Nrf2. Different PGC-1α expression in cells was established by transfection with small interfering RNA (siRNA) or plasmids overexpressing PGC-1α (pEX-3-PGC-1α). The effects of different PGC-1α expression on cellular ROS, mitochondrial ROS and Nrf2 expression were measured in cells. Wild type (WT) mice and PGC-1α conditional knockout (CKO) mice were used to analyze the effects of PGC-1α on aged sarcopenia and expression of Nrf2 and CD38 in gastrocnemius muscles. Diethylmaleate, a Nrf2 activator, was used to analyze the connection between PGC-1α and Nrf2 in cells and in mice.

RESULTS

In C2C12 cells, the expressions of PGC-1α and Nrf2 were declined by the 7β-OHC treatment or PGC-1α silence. Moreover, PGC-1α silence increased the harmful ROS and decreased the Nrf2 protein expression in the 7β-OHC-treated cells. PGC-1α overexpression decreased the harmful ROS and increased the Nrf2 protein expression in the 7β-OHC-treated cells. Diethylmaleate treatment decreased the harmful ROS in the 7β-OHC-treated or PGC-1α siRNA-transfected cells. At the same age, muscle-specific PGC-1α deficiency aggravated aged sarcopenia, decreased Nrf2 expression and increased CD38 expression in gastrocnemius muscles compared with the WT mice. Diethylmaleate treatment improved the muscle function and decreased the CD38 expression in the old two genotypes.

CONCLUSIONS

Our study demonstrated that PGC-1α modulated mitochondrial oxidative stress in aged sarcopenia through regulating Nrf2.

PGC-1α participates in regulating mitochondrial function in aged sarcopenia through effects on the Sestrin2-mediated mTORC1 pathway

BACKGROUND

Mitochondrial dysregulation in skeletal myocytes is considered a major factor in aged sarcopenia. In this study, we aimed to study the effects of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) on Sestrin2-mediated mechanistic target of rapamycin complex 1 (mTORC1) in aged skeletal muscles.

METHODS

C2C12 myoblasts were stimulated by 50 μM 7β-hydroxycholesterol (7β-OHC) to observe the changes of DNA damage, mitochondrial membrane potential (Δψm), mitochondrial ROS and PGC-1α protein. The PGC-1α silence in the C2C12 cells was established by siRNA transfection. The levels of DNA damage, Δψm, mitochondrial ROS, Sestrin2 and p-S6K1/S6K1 proteins were observed after the PGC-1α silence in the C2C12 cells. Recombinant Sestrin2 treatment was used to observe the changes of DNA damage, Δψm, mitochondrial ROS and p-S6K1/S6K1 protein in the 7β-OHC-treated or PGC-1α siRNA-transfected C2C12 cells. Wild-type (WT) mice and muscle-specific PGC-1α conditional knockout (MKO) mice, including young and old, were used to analyse the effects of PGC-1α on muscle function and the levels of Sestrin2 and p-S6K1 in the white gastrocnemius muscles. Recombinant Sestrin2 was administrated to analyse its effects on muscle function in the old WT mice and old MKO mice.

RESULTS

7β-OHC treatment induced DNA damage, mitochondrial dysfunction and decrease of PGC-1α protein in the C2C12 cells. PGC-1α silence also induced DNA damage and mitochondrial dysfunction in the C2C12 cells. Additionally, PGC-1α silence or 7β-OHC treatment decreased the levels of Sestrin2 and p-S6K1/S6K1 protein in the C2C12 cells. Recombinant Sestrin2 treatment significantly improved the DNA damage and mitochondrial dysfunction in the 7β-OHC-treated or PGC-1α siRNA-transfected C2C12 cells. At the same age, muscle-specific PGC-1α deficiency aggravated aged sarcopenia and decreased the levels of Sestrin2 and p-S6K1 in the white gastrocnemius muscles when compared to the WT mice. Recombinant Sestrin2 treatment improved muscle function and increased p-S6K1 levels in the old two genotypes.

CONCLUSION

This research demonstrates that PGC-1α participates in regulating mitochondrial function in aged sarcopenia through effects on the Sestrin2-mediated mTORC1 pathway.

Transient hydroxycholesterol treatment restrains TCR signaling to promote long-term immunity

T cell receptor (TCR) plays a fundamental role in adaptive immunity, and TCR-T cell therapy holds great promise for treating solid tumors and other diseases. However, there is a noticeable absence of chemical tools tuning TCR activity. In our study, we screened natural sterols for their regulatory effects on T cell function and identified 7-alpha-hydroxycholesterol (7a-HC) as a potent inhibitor of TCR signaling. Mechanistically, 7a-HC promoted membrane binding of CD3ε cytoplasmic domain, a crucial signaling component of the TCR-CD3 complex, through alterations in membrane physicochemical properties. Enhanced CD3ε membrane binding impeded the condensation between CD3ε and the key kinase Lck, thereby inhibiting Lck-mediated TCR phosphorylation. Transient treatments of TCR-T cells with 7a-HC resulted in reduced signaling strength, increased memory cell populations, and superior long-term antitumor functions. This study unveils a chemical regulation of TCR signaling, which can be exploited to enhance the long-term efficacy of TCR-T cell therapy.

Aging-Related Sarcopenia: Metabolic Characteristics and Therapeutic Strategies

The proportion of the elderly population is gradually increasing as a result of medical care advances, leading to a subsequent surge in geriatric diseases that significantly impact quality of life and pose a substantial healthcare burden. Sarcopenia, characterized by age-related decline in skeletal muscle mass and quality, affects a considerable portion of older adults, particularly the elderly, and can result in adverse outcomes such as frailty, fractures, bedridden, hospitalization, and even mortality. Skeletal muscle aging is accompanied by underlying metabolic changes. Therefore, elucidating these metabolic profiles and specific mechanisms holds promise for informing prevention and treatment strategies for sarcopenia. This review provides a comprehensive overview of the key metabolites identified in current clinical studies on sarcopenia and their potential pathophysiological alterations in metabolic activity. Besides, we examine potential therapeutic strategies for sarcopenia from a perspective focused on metabolic regulation.

Cytoprotective effects of α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, oleic acid and α-tocopherol on 7-ketocholesterol - Induced oxiapoptophagy: Major roles of PI3-K / PDK-1 / Akt signaling pathway and glutathione peroxidase activity in cell rescue

On murine N2a cells, 7-ketocholesterol induced an oxiapotophagic mode of cell death characterized by oxidative stress (reactive oxygen species overproduction on whole cells and at the mitochondrial level; lipid peroxidation), apoptosis induction (caspase-9, -3 and -7 cleavage, PARP degradation) and autophagy (increased ratio LC3-II / LC3-I). Oxidative stress was strongly attenuated by diphenyleneiodonium chloride which inhibits NAD(P)H oxidase. Mitochondrial and peroxisomal morphological and functional changes were also observed. Down regulation of PDK1 / Akt signaling pathways as well as of GSK3 / Mcl-1 and Nrf2 pathways were simultaneously observed in 7-ketocholesterol-induced oxiapoptophagy. These events were prevented by α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, oleic acid and α-tocopherol. The inhibition of the cytoprotection by LY-294002, a PI3-K inhibitor, demonstrated an essential role of PI3-K in cell rescue. The rupture of oxidative stress in 7-ketocholesterol-induced oxiapoptophagy was also associated with important modifications of glutathione peroxidase, superoxide dismutase and catalase activities as well as of glutathione peroxidase-1, superoxide dismutase-1 and catalase level and expression. These events were also counteracted by α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, oleic acid and α-tocopherol. The inhibition of the cytoprotection by mercaptosuccinic acid, a glutathione peroxidase inhibitor, showed an essential role of this enzyme in cell rescue. Altogether, our data support that the reactivation of PI3-K and glutathione peroxidase activities by α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, oleic acid and α-tocopherol are essential to prevent 7KC-induced oxiapoptophagy.