Contractile function recovery in severely injured gastrocnemius muscle of rats treated with either oleic or linoleic acid

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.

Excessive linoleic acid induces muscle oxidative stress through 5-lipoxygenase-dependent peroxidation

Oxidative stress in muscles is closely related to the occurrence of insulin resistance, muscle weakness and atrophy, age-related sarcopenia, and cancer. Aldehydes, a primary oxidation intermediate of polyunsaturated fatty acids, have been proven to be an important trigger for oxidative stress. However, the potential role of linoleic acid (LA) as a donor for volatile aldehydes to trigger oxidative stress has not been reported. Here, we reported that excessive dietary LA caused muscle redox imbalance and volatile aldehydes containing hexanal, 2-hexenal, and nonanal were the main metabolites leading to oxidative stress. Importantly, we identified 5-lipoxygenase (5-LOX) as a key enzyme mediating LA peroxidation in crustaceans for the first time. The inhibition of 5-LOX significantly suppressed the content of aldehydes produced by excessive LA. Mechanistically, the activation of the cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) pathway facilitated the translocation of 5-LOX from the nucleus to the cytoplasm, where 5-LOX oxidized LA, leading to oxidative stress through the generation of aldehydes. This study suggests that 5-LOX is a potential target to prevent the production of harmful aldehydes.

Endoplasmic Reticulum Stress and Autophagy Markers in Soleus Muscle Disuse-Induced Atrophy of Rats Treated with Fish Oil

Endoplasmic reticulum stress (ERS) and autophagy pathways are implicated in disuse muscle atrophy. The effects of high eicosapentaenoic (EPA) or high docosahexaenoic (DHA) fish oils on soleus muscle ERS and autophagy markers were investigated in a rat hindlimb suspension (HS) atrophy model. Adult Wistar male rats received daily by gavage supplementation (0.3 mL per 100 g b.w.) of mineral oil or high EPA or high DHA fish oils (FOs) for two weeks. Afterward, the rats were subjected to HS and the respective treatments concomitantly for an additional two-week period. After four weeks, we evaluated ERS and autophagy markers in the soleus muscle. Results were analyzed using two-way analysis of variance (ANOVA) and Bonferroni post hoc test. Gastrocnemius muscle ω-6/ω-3 fatty acids (FAs) ratio was decreased by both FOs indicating the tissue incorporation of omega-3 fatty acids. HS altered (p < 0.05) the protein content (decreasing total p38 and BiP and increasing p-JNK2/total JNK2 ratio, and caspase 3) and gene expressions (decreasing BiP and increasing IRE1 and PERK) of ERS and autophagy (decreasing Beclin and increasing LC3 and ATG14) markers in soleus. Both FOs attenuated (p < 0.05) the increase in PERK and ATG14 expressions induced by HS. Thus, both FOs could potentially attenuate ERS and autophagy in skeletal muscles undergoing atrophy.

Cryptotympana pustulata Extract and Its Main Active Component, Oleic Acid, Inhibit Ovalbumin-Induced Allergic Airway Inflammation through Inhibition of Th2/GATA-3 and Interleukin-17/RORγt Signaling Pathways in Asthmatic Mice

Cicadae Periostracum (CP), derived from the slough of Cryptotympana pustulata, has been used as traditional medicine in Korea and China because of its diaphoretic, antipyretic, anti-inflammatory, antioxidant, and antianaphylactic activities. The major bioactive compounds include oleic acid (OA), palmitic acid, and linoleic acid. However, the precise therapeutic mechanisms underlying its action in asthma remain unclear. The objective of this study was to determine the antiasthmatic effects of CP in an ovalbumin (OVA)-induced asthmatic mouse model. CP and OA inhibited the inflammatory cell infiltration, airway hyperresponsiveness (AHR), and production of interleukin (IL)7 and Th2 cytokines (IL-5) in the bronchoalveolar lavage fluid and OVA-specific imunoglobin E (IgE) in the serum. The gene expression of IL-5, IL-13, CCR3, MUC5AC, and COX-2 was attenuated in lung tissues. CP and OA might inhibit the nuclear translocation of GATA-binding protein 3 (GATA-3) and retinoic acid receptor-related orphan receptor γt (RORγt) via the upregulation of forkhead box p3 (Foxp3), thereby preventing the activation of GATA-3 and RORγt. In the in vitro experiment, a similar result was observed for Th2 and GATA-3. These results suggest that CP has the potential for the treatment of asthma via the inhibition of the GATA-3/Th2 and IL-17/RORγt signaling pathways.

Metabolic fingerprinting of cell types in mouse skeletal muscle by combining TOF-SIMS with immunofluorescence staining

Skeletal muscle tissue is composed of various muscle cell types which differ in physiological functions. Changes in cell type composition of skeletal muscle are associated with the development of metabolic diseases. Skeletal muscle cell types are currently distinguished by immunofluorescence (IF) staining based on myosin heavy chain (MHC) isoform difference. However, it remains a challenge to provide metabolic fingerprints of different muscle cell types by IF staining. Therefore, in this study, we proposed a method to examine metabolite distribution within different cell types by time-of-flight secondary ion mass spectrometry (TOF-SIMS) with high spatial resolution. Skeletal muscle samples from C57/BL6 mice were obtained by slicing. Cell types in TOF-SIMS images were labelled corresponding to IF images from the same region of serially cut sections. Mass spectra corresponding to individual muscle cells were extracted to compare metabolic fingerprints among cell types. Skeletal muscle cells were classified into two clusters based on the mass spectra of individual cells. Unsaturated diacylglycerol (DG) and fatty acid (FA) species were found to be distributed in a cell-type dependent manner. Moreover, relative quantification showed that the content of unsaturated DGs, oleic acid and linoleic acid was higher in type I and type IIA cells than in type IIB cells. TOF-SIMS in combination with IF enables us to directly visualize metabolite distribution in different cell types, to find potential biomarkers for cell type classification. TOF-SIMS imaging coupled with IF staining has been proved to be a promising tool for metabolic fingerprinting of different skeletal muscle cell types.

Fatty Acid Profile and Antioxidant Status Fingerprint in Sarcopenic Elderly Patients: Role of Diet and Exercise

Plasma fatty acids (FAs) and oxidant status contribute to the etiology of sarcopenia in the elderly concurring to age-related muscle loss and elderly frailty through several mechanisms including changes in FA composition within the sarcolemma, promotion of chronic low-grade inflammation, and insulin resistance. The aim of this study was to determine the FA profile and pro-antioxidant status in sarcopenic frail elderly patients enrolled in a nutritional and physical activity program and to evaluate their correlation with clinical markers. Moreover, the possible changes, produced after a short-term clinical protocol, were evaluated. Plasma and erythrocyte FA composition and pro-antioxidant status were analyzed in sarcopenic elderly subjects recruited for the randomized clinical study and treated with a placebo or dietary supplement, a personalized diet, and standardized physical activity. Subjects were tested before and after 30 days of treatment. Pearson correlations between biochemical parameters and patients’ characteristics at recruitment indicate interesting features of sarcopenic status such as negative correlation among the plasma FA profile, age, and physical characteristics. Physical activity and dietetic program alone for 30 days induced a decrease of saturated FA concentration with a significant increase of dihomo-gamma-linolenic acid. Supplementation plus physical activity induced a significant decrease of linoleic acid, omega-6 polyunsaturated FAs, and an increase of stearic and oleic acid concentration. Moreover, glutathione reductase activity, which is an indicator of antioxidant status, significantly increased in erythrocytes. Changes over time between groups indicate significant differences for saturated FAs, which suggest that the amino acid supplementation restores FA levels that are consumed during physical activity. A relationship between FA and clinical/metabolic status revealed unique correlations and a specific metabolic and lipidomic fingerprint in sarcopenic elderly. The results indicate the positive beneficial role of supplementation and physical activity on plasma FA status and the antioxidant system as a co-adjuvant approach in sarcopenic, frail, elderly patients.

Experimental Model of Skeletal Muscle Laceration in Rats

This is a modified experimental model previously developed in mouse to study skeletal muscle laceration in rats. All experimental procedures are performed during the light period, including anesthesia and surgery. The animals are randomly distributed into control and injured groups prior to the procedure. This experimental model can be used to investigate skeletal muscle laceration repair.

In Vivo Electrical Stimulation for the Assessment of Skeletal Muscle Contractile Function in Murine Models

Skeletal muscle electrical stimulation is commonly used for clinical purposes, assisting recovery, preservation, or even improvement of muscle mass and function in healthy and pathological conditions. Additionally, it is a useful research tool for evaluation of skeletal muscle contractile function. It may be applied in vitro, using cell culture or isolated fibers/muscles, and in vivo, using human subjects or animal models (neuromuscular electrical stimulation - NMES). This chapter focuses on the electrical stimulation of the sciatic nerve as a research method for evaluation of the contractile properties of murine hind limb muscles. Variations of this protocol allow for the assessment of muscle force, fatigue resistance, contraction and relaxation times, and can be used as a model of contraction-induced muscle injury, reactive oxygen species production, and muscle adaptation to contractile activity.

Balanced Diet-Fed Fat-1 Transgenic Mice Exhibit Lower Hindlimb Suspension-Induced Soleus Muscle Atrophy

The consequences of two-week hindlimb suspension (HS) on skeletal muscle atrophy were investigated in balanced diet-fed Fat-1 transgenic and C57BL/6 wild-type mice. Body composition and gastrocnemius fatty acid composition were measured. Skeletal muscle force, cross-sectional area (CSA), and signaling pathways associated with protein synthesis (protein kinase B, Akt; ribosomal protein S6, S6, eukaryotic translation initiation factor 4E-binding protein 1, 4EBP1; glycogen synthase kinase3-beta, GSK3-beta; and extracellular-signal-regulated kinases 1/2, ERK 1/2) and protein degradation (atrophy gene-1/muscle atrophy F-box, atrogin-1/MAFbx and muscle RING finger 1, MuRF1) were evaluated in the soleus muscle. HS decreased soleus muscle wet and dry weights (by 43% and 26%, respectively), muscle isotonic and tetanic force (by 29% and 18%, respectively), CSA of the soleus muscle (by 36%), and soleus muscle fibers (by 45%). Fat-1 transgenic mice had a decrease in the ω-6/ω-3 polyunsaturated fatty acids (PUFAs) ratio as compared with C57BL/6 wild-type mice (56%, p < 0.001). Fat-1 mice had lower soleus muscle dry mass loss (by 10%) and preserved absolute isotonic force (by 17%) and CSA of the soleus muscle (by 28%) after HS as compared with C57BL/6 wild-type mice. p-GSK3B/GSK3B ratio was increased (by 70%) and MuRF-1 content decreased (by 50%) in the soleus muscle of Fat-1 mice after HS. Balanced diet-fed Fat-1 mice are able to preserve in part the soleus muscle mass, absolute isotonic force and CSA of the soleus muscle in a disuse condition.

Pretreatment with fish oil attenuates heart ischaemia consequences in rats

NEW FINDINGS

What is the central question of this study? We investigated whether pretreatment with fish oil could prevent the major consequences of ischaemic injury to the heart. What is the main finding and its importance? Fish oil pretreatment attenuated the consequences of ischaemic injury as indicated by the small infarction area and the preservation of systolic function and coronary blood flow. These findings support the use of fish oil in order to reduce the impact of heart ischaemia. ω-3 Polyunsaturated fatty acid (ω-3 PUFA)-rich fish oil supplementation has protective effects on heart ischaemic injury. Left ventricular (LV) ischaemia was induced in rats by permanent ligation of the left descending coronary artery. Saline, fish oil or soybean oil was administered daily by gavage [3 g (kg body weight)^-1 ] for 20 days before inducing ischaemia. Outcomes were assessed 24 h after left descending coronary artery ligation. Pretreatment with fish oil decreased the ω-6/ω-3 fatty acid ratio in the LV. A reduction in infarct size and in the intensity of ventricular systolic dysfunction was found in the fish oil group compared with the saline or soybean oil groups through echocardiographic evaluation. Before infarction, LV glycogen concentrations were decreased in the fish oil group compared with the saline group. Soybean oil pretreatment led to a further increase in the LV levels of CINC-2/αβ, IL-1β and TNF-α induced by the heart infarction. In heart-infarcted rats, fish oil pretreatment decreased creatine kinase and caspase-3 activities; prevented the decrease in the coronary blood flow; increased LV contents of ATP and lactate; increased the mRNA levels of iNOS, eNOS, HIF1α, GLUT1, VEGF-α and p53 in the LV as measured by RT-PCR; and did not change LV pro-inflammatory cytokine concentrations compared with the control group. Fish oil protected the heart from ischaemia, as indicated by the decrease in the heart infarction area and systolic dysfunction associated with increased LV ATP concentrations and maintenance of the coronary blood flow with no change in pro-inflammatory cytokine levels.