Oleic acid up-regulates myosin heavy chain (MyHC) 1 expression and increases mitochondrial mass and maximum respiration in C2C12 myoblasts

Therapeutic potential of oleic acid supplementation in myotonic dystrophy muscle cell models

BACKGROUND

We recently reported that upregulation of Musashi 2 (MSI2) protein in the rare neuromuscular disease myotonic dystrophy type 1 contributes to the hyperactivation of the muscle catabolic processes autophagy and UPS through a reduction in miR-7 levels. Because oleic acid (OA) is a known allosteric regulator of MSI2 activity in the biogenesis of miR-7, here we sought to evaluate endogenous levels of this fatty acid and its therapeutic potential in rescuing cell differentiation phenotypes in vitro. In this work, four muscle cell lines derived from DM1 patients were treated with OA for 24 h, and autophagy and muscle differentiation parameters were analyzed.

RESULTS

We demonstrate a reduction of OA levels in different cell models of the disease. OA supplementation rescued disease-related phenotypes such as fusion index, myotube diameter, and repressed autophagy. This involved inhibiting MSI2 regulation of direct molecular target miR-7 since OA isoschizomer, elaidic acid (EA) could not cause the same rescues. Reduction of OA levels seems to stem from impaired biogenesis since levels of the enzyme stearoyl-CoA desaturase 1 (SCD1), responsible for converting stearic acid to oleic acid, are decreased in DM1 and correlate with OA amounts.

CONCLUSIONS

For the first time in DM1, we describe a fatty acid metabolism impairment that originated, at least in part, from a decrease in SCD1. Because OA allosterically inhibits MSI2 binding to molecular targets, reduced OA levels synergize with the overexpression of MSI2 and contribute to the MSI2 > miR-7 > autophagy axis that we proposed to explain the muscle atrophy phenotype.

UPLC-QTOF-MS based metabolomics unravels the modulatory effect of ginseng water extracts on rats with Qi-deficiency

Ginseng is commonly used as a nutritional supplement and daily wellness product due to its ability to invigorate qi. As a result, individuals with Qi-deficiency often use ginseng as a health supplement. Ginsenosides and polysaccharides are the primary components of ginseng. However, the therapeutic effects and mechanisms of action of these components in Qi-deficiency remain unclear. This study aimed to determine the modulatory effects and mechanisms of ginseng water extract, ginsenosides, and ginseng polysaccharides in a rat model of Qi-deficiency using metabolomics and network analysis. The rat model of Qi-deficiency was established via swimming fatigue and a restricted diet. Oral administration of different ginseng water extracts for 30 days primarily alleviated oxidative stress and disrupted energy metabolism and immune response dysfunction caused by Qi-deficiency in rats. Ultra-high-performance liquid chromatography combined with quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) was used for untargeted serum metabolomic analysis. Based on the analysis results, the active constituents of ginseng significantly reversed the changes in serum biomarkers related to Qi-deficiency in rats, particularly energy, amino acid, and unsaturated fatty acid metabolism. Furthermore, analysis of the metabolite-gene network suggested that the anti-Qi-deficiency effects of the ginseng components were mainly associated with toll-like receptor (TLR) signaling and inflammatory response. Additional verification revealed that treatment with the ginseng components effectively reduced the inflammatory response and activation of the myocardial TLR4/NF-κB pathway induced by Qi-deficiency, especially the ginseng water extracts. Therefore, ginseng could be an effective preventive measure against the progression of Qi-deficiency by regulating metabolic and inflammatory responses.

Camellia oil exhibits anti-fatigue property by modulating antioxidant capacity, muscle fiber, and gut microbial composition in mice

Camellia seed oil (CO) has high nutritional value and multiple bioactivities. However, the specific anti-fatigue characteristics and the implied mechanism of CO have not yet been fully elucidated. Throughout this investigation, male C57BL/6J mice, aged 8 weeks, underwent exhaustive exercise with or without CO pretreatment (2, 4, and 6 mL/kg BW) for 28 days. CO could extend the rota-rod and running time, reduce blood urea nitrogen levels and serum lactic acid, and increase muscle and hepatic glycogen, adenosine triphosphate, and anti-oxidative indicators. Additionally, CO could upregulate the mRNA and Nrf2 protein expression levels, as well as enhance the levels of its downstream antioxidant enzymes and induce the myofiber-type transformation from fast to slow and attenuate the gut mechanical barrier. Moreover, CO could ameliorate gut dysbiosis by reducing Firmicutes to Bacteroidetes ratio at the phylum level, increasing the percentage of Alistipes, Alloprevotella, Lactobacillus, and Muribaculaceae, and decreasing the proportion of Dubosiella at the genus level. In addition, specific bacterial taxa, which were altered by CO, showed a significant correlation with partial fatigue-related parameters. These findings suggest that CO may alleviate fatigue by regulating antioxidant capacity, muscle fiber transformation, gut mechanical barrier, and gut microbial composition in mice. PRACTICAL APPLICATION: Our study revealed that camellia seed oil (CO) could ameliorate exercise-induced fatigue in mice by modulating antioxidant capacity, muscle fiber, and gut microbial composition in mice. Our results promote the application of CO as an anti-fatigue functional food that targets oxidative stress, myofiber-type transformation, and microbial community.

Dietary protein restriction regulates skeletal muscle fiber metabolic characteristics associated with the FGF21-ERK1/2 pathway

Under conditions of dietary amino acid balance, decreasing the dietary crude protein (CP) level in pigs has a beneficial effect on meat quality. To further elucidate the mechanism, we explored the alteration of muscle fiber characteristics and key regulators related to myogenesis in the skeletal muscle of pigs fed a protein restricted diet. Compared to pigs fed a normal protein diet, dietary protein restriction significantly increased the slow-twitch muscle fiber proportion in skeletal muscle, succinic dehydrogenase (SDH) activity, the concentrations of ascorbate, biotin, palmitoleic acid, and the ratio of s-adenosylhomocysteine (SAM) to s-adenosylhomocysteine (SAH), but the fast-twitch muscle fiber proportion, lactate dehydrogenase (LDH) activity, the concentrations of ATP, glucose-6-phosphate, SAM, and SAH in skeletal muscle, and the ratio of serum triiodothyronine (T3) to tetraiodothyronine (T4) were decreased. In conclusion, we demonstrated that dietary protein restriction induced skeletal muscle fiber remodeling association the regulation of FGF21-ERK1/2-mTORC1 signaling in weaned piglets.

Comparison of the effects of monounsaturated fatty acids and polyunsaturated fatty acids on the lipotoxicity of islets

Background

Monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) have been reported to combat saturated fatty acid (SFA)-induced cellular damage, however, their clinical effects on patients with metabolic diseases such as diabetes and hyperlipidemia are still controversial. Since comparative studies of the effects of these two types of unsaturated fatty acids (UFAs) are still limited. In this study, we aimed to compare the protective effects of various UFAs on pancreatic islets under the stress of SFA-induced metabolic disorder and lipotoxicity.

Methods

Rat insulinoma cell line INS-1E were treated with palmitic acid (PA) with or without UFAs including eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), arachidonic acid (AA), and oleic acid (OA) to determine cell viability, apoptosis, endoplasmic reticulum (ER) stress, and inflammatory. In vivo, male C57BL/6 mice were fed a 60% high-fat diet (HFD) for 12 w. Then the lard in HFD was partially replaced with fish oil (FO) and olive oil (OO) at low or high proportions of energy (5% or 20%) to observe the ameliorative effects of the UFA supplement.

Results

All UFAs significantly improved PA-induced cell viability impairment in INS-1E cells, and their alleviation on PA induced apoptosis, ER stress and inflammation were confirmed. Particularly, OA had better effects than EPA, DHA, and AA on attenuating cellular ER stress. In vivo, the diets with a low proportion of UFAs (5% of energy) had limited effects on HFD induced metabolic disorder, except for a slight improved intraperitoneal glucose tolerance in obese mice. However, when fed diets containing a high proportion of UFAs (20% of energy), both the FO and OO groups exhibited substantially improved glucose and lipid metabolism, such as decrease in total cholesterol (TC), low-density lipoprotein (LDL), fasting blood glucose (FBG), and fasting blood insulin (FBI)) and improvement of insulin sensitivity evidenced by intraperitoneal glucose tolerance test (IPGTT) and intraperitoneal insulin tolerance test (IPITT). Unexpectedly, FO resulted in abnormal elevation of the liver function index aspartate aminotransferase (AST) in serum. Pathologically, OO attenuated HFD-induced compensatory hyperplasia of pancreatic islets, while this effect was not obvious in the FO group.

Conclusions

Both MUFAs and PUFAs can effectively protect islet β cells from SFA-induced cellular lipotoxicity. In particular, both OA in vitro and OO in vivo showed superior activities on protecting islets function and enhance insulin sensitivity, suggesting that MUFAs might have greater potential for nutritional intervention on diabetes.

Dietary oleic acid intake increases the proportion of type 1 and 2X muscle fibers in mice

Skeletal muscle is one of the largest metabolic tissues in mammals and is composed of four different types of muscle fibers (types 1, 2A, 2X, and 2B); however, type 2B is absent in humans. Given that slow-twitch fibers are superior to fast-twitch fibers in terms of oxidative metabolism and are rich in mitochondria, shift of muscle fiber types in direction towards slower fiber types improves metabolic disorders and endurance capacity. We previously had reported that oleic acid supplementation increases type 1 fiber formation in C2C12 myotubes; however, its function still remains unclear. This study aimed to determine the effect of oleic acid on the muscle fiber types and endurance capacity. An in vivo mouse model was used, and mice were fed a 10% oleic acid diet for 4 weeks. Two different skeletal muscles, slow soleus muscle with the predominance of slow-twitch fibers and fast extensor digitorum longus (EDL) muscle with the predominance of fast-twitch fibers, were used. We found that dietary oleic acid intake improved running endurance and altered fiber type composition of muscles, the proportion of type 1 and 2X fibers increased in the soleus muscle and type 2X increased in the EDL muscle. The fiber type shift in the EDL muscle was accompanied by an increased muscle TAG content. In addition, blood triacylglycerol (TAG) and non-esterified fatty acid levels decreased during exercise. These changes suggested that lipid utilization as an energy substrate was enhanced by oleic acid. Increased proliferator-activated receptor γ coactivator-1β protein levels were observed in the EDL muscle, which potentially enhanced the fiber type transitions towards type 2X and muscle TAG content. In conclusion, dietary oleic acid intake improved running endurance with the changes of muscle fiber type shares in mice. This study elucidated a novel functionality of oleic acid in skeletal muscle fiber types. Further studies are required to elucidate the underlying mechanisms. Our findings have the potential to contribute to the field of health and sports science through nutritional approaches, such as the development of supplements aimed at improving muscle function.

GC-MS Analysis of Bioactive Compounds Extracted from Plant Rhazya stricta Using Various Solvents

Worldwide, human beings have traditionally employed many folkloric herbal resources as complementary and alternative remedies, and these remedies have played a pivotal role in modern medicines for many decades, as scientists have used them to develop drugs. We studied the effects of employing solvents with varying polarity on the yields of phytochemical components extracted from the plant Rhazya stricta. We used chloroform-methanol (1:1), methanol, ethanol, diethyl ether, and ethyl acetate as extraction solvents. The results showed that the efficiencies of the solvents at extracting phytochemical compounds were in this order: chloroform-methanol < ethanol < methanol < diethyl ether < ethyl acetate extract. The chloroform-methanol extract produced the highest concentration of phenolic and flavonoid contents among the five solvents tested (13.3 mg GAE/g DM and 5.43 CE/g DM). The yields of the extracted phytochemical compounds ranged from 47.55 to 6.05%. The results revealed that the properties of the extraction solvents considerably impacted the extraction yield and the phytochemical components of the R. stricta extract. Furthermore, compared with the other solvents, the chloroform-methanol extraction led to the highest yield (47.55%) and to more phytochemical substances being extracted. The aim of this study is to investigate the phytochemical compounds extracted from R. stricta with different solvents that have different polarities.

Faeces tea of cherry caterpillar (larvae of Phalera flavescens) promotes differentiation into myotubes, activates mitochondria, and suppresses the protein expression of ubiquitin ligase in C2C12

Sarcopenia is a syndrome characterised by progressive and systemic loss of skeletal muscle mass and strength. In order to prevent sarcopenia and lead a healthy life, it is necessary to maintain muscle mass and prevent loss of muscle mass. Insect faeces have long been consumed as tea in China, both as a medicine and as a functional food. In the present work, we investigated the efficacy of cherry caterpillar faeces tea (PT) for treating sarcopenia, particularly concerning muscle building and atrophy suppression using C2C12 cells. PT treatment (0.2 mg/mL) increased myotube widths by approximately 40%, and increased the expression levels of Myod, Myog, and MYHC. Additionally, PGC1α, TFAM, SDHA, BCAT, and BCKDH were upregulated in a PT concentration-dependent manner. For PGC1α, which is the transcription coactivator, the protein expression level also increased in a concentration-dependent manner. The findings demonstrated that PT could stimulate PGC1α and activate mitochondria via branched-chain amino acid metabolism and the electron transport chain in C2C12 myoblasts. Furthermore, PT suppressed LPS-induce expression of IL6 and TNFα, and reduced the protein expression levels of the ubiquitin ligases Atrogin-1 and MuRF, which are major cause of muscle atrophy. These results indicated that PT could be effective for muscle building and suppression of atrophy.

Integrated analysis of plasma and urine reveals unique metabolomic profiles in idiopathic inflammatory myopathies subtypes

OBJECTIVES

Idiopathic inflammatory myopathies (IIM) are a class of autoimmune diseases with high heterogeneity that can be divided into different subtypes based on clinical manifestations and myositis-specific autoantibodies (MSAs). However, even in each IIM subtype, the clinical symptoms and prognoses of patients are very different. Thus, the identification of more potential biomarkers associated with IIM classification, clinical symptoms, and prognosis is urgently needed.

METHODS

Plasma and urine samples from 79 newly diagnosed IIM patients (mean disease duration 4 months) and 52 normal control (NC) samples were analysed by high-performance liquid chromatography of quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF-MS)/MS-based untargeted metabolomics. Orthogonal partial least-squares discriminate analysis (OPLS-DA) were performed to measure the significance of metabolites. Pathway enrichment analysis was conducted based on the KEGG human metabolic pathways. Ten machine learning (ML) algorithms [linear support vector machine (SVM), radial basis function SVM, random forest, nearest neighbour, Gaussian processes, decision trees, neural networks, adaptive boosting (AdaBoost), Gaussian naive Bayes and quadratic discriminant analysis] were used to classify each IIM subtype and select the most important metabolites as potential biomarkers.

RESULTS

OPLS-DA showed a clear separation between NC and IIM subtypes in plasma and urine metabolic profiles. KEGG pathway enrichment analysis revealed multiple unique and shared disturbed metabolic pathways in IIM main [dermatomyositis (DM), anti-synthetase syndrome (ASS), and immune-mediated necrotizing myopathy (IMNM)] and MSA-defined subtypes (anti-Mi2+, anti-MDA5+, anti-TIF1γ+, anti-Jo1+, anti-PL7+, anti-PL12+, anti-EJ+, and anti-SRP+), such that fatty acid biosynthesis was significantly altered in both plasma and urine in all main IIM subtypes (enrichment ratio > 1). Random forest and AdaBoost performed best in classifying each IIM subtype among the 10 ML models. Using the feature selection methods in ML models, we identified 9 plasma and 10 urine metabolites that contributed most to separate IIM main subtypes and MSA-defined subtypes, such as plasma creatine (fold change = 3.344, P = 0.024) in IMNM subtype and urine tiglylcarnitine (fold change = 0.351, P = 0.037) in anti-EJ+ ASS subtype. Sixteen common metabolites were found in both the plasma and urine samples of IIM subtypes. Among them, some were correlated with clinical features, such as plasma hypogeic acid (r = -0.416, P = 0.005) and urine malonyl carnitine (r = -0.374, P = 0.042), which were negatively correlated with the prevalence of interstitial lung disease.

CONCLUSIONS

In both plasma and urine samples, IIM main and MSA-defined subtypes have specific metabolic signatures and pathways. This study provides useful clues for understanding the molecular mechanisms, searching potential diagnosis biomarkers and therapeutic targets for IIM.

Dietary Olive Oil Intake Improves Running Endurance with Intramuscular Triacylglycerol Accumulation in Mice

Olive oil is a functional food shown to have a variety of bioactive effects. Therefore, we expect it to be a novel functional food with an exercise-mimetic effect on skeletal muscles. This study aimed to investigate the effect of olive oil on the endurance capacity and muscle metabolism in mice. Mice fed a 7% (w/w) olive oil diet for eight weeks showed improved treadmill running endurance and increased intramuscular triacylglycerol (IMTG) accumulation in the gastrocnemius muscle compared to soybean oil diet-fed controls. The increase in running endurance with olive oil intake was independent of the muscle fiber type. To elucidate underlying the mechanism of elevated IMTG levels, we examined the expression levels of the genes related to lipid metabolism. We found that the expression of diacylglycerol O-acyltransferase1 (DGAT1) was significantly upregulated in the muscle of olive oil diet-fed mice. In addition, the olive oil diet-fed mice showed no metabolic impairment or differences in growth profiles compared to the controls. These results suggest that dietary olive oil intake affects muscle metabolism and muscle endurance by increasing energy accumulation.

Tissue-Engineered Skeletal Muscle Models to Study Muscle Function, Plasticity, and Disease

Skeletal muscle possesses remarkable plasticity that permits functional adaptations to a wide range of signals such as motor input, exercise, and disease. Small animal models have been pivotal in elucidating the molecular mechanisms regulating skeletal muscle adaptation and plasticity. However, these small animal models fail to accurately model human muscle disease resulting in poor clinical success of therapies. Here, we review the potential of in vitro three-dimensional tissue-engineered skeletal muscle models to study muscle function, plasticity, and disease. First, we discuss the generation and function of in vitro skeletal muscle models. We then discuss the genetic, neural, and hormonal factors regulating skeletal muscle fiber-type in vivo and the ability of current in vitro models to study muscle fiber-type regulation. We also evaluate the potential of these systems to be utilized in a patient-specific manner to accurately model and gain novel insights into diseases such as Duchenne muscular dystrophy (DMD) and volumetric muscle loss. We conclude with a discussion on future developments required for tissue-engineered skeletal muscle models to become more mature, biomimetic, and widely utilized for studying muscle physiology, disease, and clinical use.