Oral administration of wild plant-derived minerals and red ginseng ameliorates insulin resistance in fish through different pathways.

Many kinds of fish are characterized by a limited efficiency to use carbohydrates. For this reason, raw fish and mixed feed containing a lot of fish meal have been used as feed for fish farming. However, continuing to use high-protein diets not only increases the cost of fish farming, but may also fuel animal protein shortages. Furthermore, carbohydrates are added to improve the texture of the feed and act as a binding agent and are usually contained at 20% in the feed. It makes sense, therefore, to find ways to make good use of carbohydrates rather than wasting them. The physiological mechanisms of glucose intolerance in fish are not yet well understood. Therefore, we investigated the glucose utilization of fish, omnivorous goldfish Carassius auratus and carnivorous rainbow trout Oncorhynchus mykiss. Furthermore, the effects of oral administration of wild plant-derived minerals and red ginseng on the glucose utilization in these fish muscle cells were investigated. As a result, we found the following. (1) An extremely high insulin resistance in fish muscle and the symptom was more pronounced in carnivorous rainbow trout. (2) Administration of wild plant-derived minerals promotes the translocation of the insulin-responsive glucose transporter GLUT4 to the cell surface of white muscle via activation of the PI3 kinase axis, whereas administration of red ginseng not only promotes GLUT4 transfer and translocation to the cell surface of white muscle via AMPK activation as well as promoting glucose uptake into muscle cells via a pathway separate from the insulin signaling system. (3) In fish, at least goldfish and rainbow trout, both PI3K/Akt and AMPK signaling cascades exist to promote glucose uptake into muscle cells, as in mammals.

Carnosic Acid Attenuates the Free Fatty Acid-Induced Insulin Resistance in Muscle Cells and Adipocytes.

Elevated blood free fatty acids (FFAs), as seen in obesity, impair insulin action leading to insulin resistance and Type 2 diabetes mellitus. Several serine/threonine kinases including JNK, mTOR, and p70 S6K cause serine phosphorylation of the insulin receptor substrate (IRS) and have been implicated in insulin resistance. Activation of AMP-activated protein kinase (AMPK) increases glucose uptake, and in recent years, AMPK has been viewed as an important target to counteract insulin resistance. We reported previously that carnosic acid (CA) found in rosemary extract (RE) and RE increased glucose uptake and activated AMPK in muscle cells. In the present study, we examined the effects of CA on palmitate-induced insulin-resistant L6 myotubes and 3T3L1 adipocytes. Exposure of cells to palmitate reduced the insulin-stimulated glucose uptake, GLUT4 transporter levels on the plasma membrane, and Akt activation. Importantly, CA attenuated the deleterious effect of palmitate and restored the insulin-stimulated glucose uptake, the activation of Akt, and GLUT4 levels. Additionally, CA markedly attenuated the palmitate-induced phosphorylation/activation of JNK, mTOR, and p70S6K and activated AMPK. Our data indicate that CA has the potential to counteract the palmitate-induced muscle and fat cell insulin resistance.

Synthesis and Identification of Biologically Active Mono-Labelled FITC-Insulin Conjugate.

Fluorescently labelling proteins such as insulin have wide ranging applications in a pharmaceutical research and drug delivery. Human insulin (Actrapid®) was labelled with fluorescein isothiocyanate (FITC) and the synthesised conjugate identified using reverse phase high performance liquid chromatography (RP-HPLC) on a C18 column and a gradient method with mobile phase A containing 0.1% trifluoroacetic acid (TFA) in Millipore water and mobile phase B containing 90% Acetonitrile, 10% Millipore water and 0.1% TFA. Syntheses were carried out at varying reaction times between 4 and 20 h. Mono-labelled FITC-insulin conjugate was successfully synthesised with labelling at the B1 position on the insulin chain using a molar ratio of 2:1 (FITC:insulin) at a reaction time of 18 h and confirmed by electrospray mass spectroscopy. Reactions were studied across a pH range of 7-9.8 and the quantities switch from mono-labelled to di-labelled FITC-insulin conjugates at a reaction time of 2 h (2:1 molar ratio) at pH > 8. The conjugates isolated from the studies had biological activities in comparison to native insulin of 99.5% monoB1, 78% monoA1, 51% diA1B1 and 0.06% triA1B1B29 in HUVEC cells by examining AKT phosphorylation levels. MonoB1 FITC-insulin conjugate was also compared to native insulin by examining cell surface GLUT4 in C2C12 skeletal muscle cells. No significant difference in the cellular response was observed for monoB1 produced in-house compared to native insulin. Therefore mono-labelled FITC-insulin at the B1 position showed similar biological activity as native insulin and can potentially be used for future biomedical applications.

Polygonatum sibiricum polysaccharides (PSP) improve the palmitic acid (PA)-induced inhibition of survival, inflammation, and glucose uptake in skeletal muscle cells.

Polygonatum sibiricum polysaccharides (PSP) can decrease the levels of fasting blood glucose, total cholesterol, and triglyceride (TG) in hyperlipidemic and diabetic animals. It can also reduce inflammatory cytokines and promote glucose uptake in adipocytes. However, the underlying molecular mechanisms of PSP in improving insulin resistance (IR) in skeletal muscle remain unclear. In this study, palmitic acid (PA) induced an IR model in L6 myotubes. After treatment, cell proliferation was measured using the CCK8. miR-340-3p, glucose transporter 4 (GLUT-4), and interleukin-1 receptor-associated kinase 3 (IRAK3) expression was measured by qRT-PCR. IRAK3 protein levels were measured by Western blotting. Glucose in the cell supernatant, TG concentration in L6 myotubes, and the levels of IL-1ß, IL-6, and TNF-α were measured by an ELISA. We found that cell survival, glucose uptake, and GLUT-4 expression in L6 myotubes were significantly suppressed, while lipid accumulation and inflammatory factor levels were enhanced by PA stimulation. Furthermore, PSP treatment markedly alleviated these effects. Interestingly, PSP also significantly reduced the upregulated expression of miR-340-3p in the L6 myotube model of IR. Furthermore, overexpression of miR-340-3p reversed the beneficial effects of PSP in the same IR model. miR-340-3p can bind to the 3'-untranslated regions of IRAK3. Additionally, PA treatment inhibited IRAK3 expression, whereas PSP treatment enhanced IRAK3 expression in L6 myotubes. Additionally, miR-340-3p also inhibited IRAK3 expression in L6 myotubes. Taken together, PSP improved inflammation and glucose uptake in PA-treated L6 myotubes by regulating miR-340-3p/IRAK3, suggesting that PSP may be suitable as a novel therapeutic agent for IR.

Decreased miR-497-5p Suppresses IL-6 Induced Atrophy in Muscle Cells.

Interleukin-6 (IL-6) is a pro-inflammatory cytokine associated with skeletal muscle wasting in cancer cachexia. The control of gene expression by microRNAs (miRNAs) in muscle wasting involves the regulation of thousands of target transcripts. However, the miRNA-target networks associated with IL6-induced muscle atrophy remain to be characterized. Here, we show that IL-6 promotes the atrophy of C2C12 myotubes and changes the expression of 20 miRNAs (5 up-regulated and 15 down-regulated). Gene Ontology analysis of predicted miRNAs targets revealed post-transcriptional regulation of genes involved in cell differentiation, apoptosis, migration, and catabolic processes. Next, we performed a meta-analysis of miRNA-published data that identified miR-497-5p, a down-regulated miRNAs induced by IL-6, also down-regulated in other muscle-wasting conditions. We used miR-497-5p mimics and inhibitors to explore the function of miR-497-5p in C2C12 myoblasts and myotubes. We found that miR-497-5p can regulate the expression of the cell cycle genes CcnD2 and CcnE1 without affecting the rate of myoblast cellular proliferation. Notably, miR-497-5p mimics induced myotube atrophy and reduced Insr expression. Treatment with miR-497-5p inhibitors did not change the diameter of the myotubes but increased the expression of its target genes Insr and Igf1r. These genes are known to regulate skeletal muscle regeneration and hypertrophy via insulin-like growth factor pathway and were up-regulated in cachectic muscle samples. Our miRNA-regulated network analysis revealed a potential role for miR-497-5p during IL6-induced muscle cell atrophy and suggests that miR-497-5p is likely involved in a compensatory mechanism of muscle atrophy in response to IL-6.

Indole-3-Propionic Acid, a Functional Metabolite of Clostridium sporogenes, Promotes Muscle Tissue Development and Reduces Muscle Cell Inflammation.

Clostridium sporogenes (C. sporogenes), as a potential probiotic, metabolizes tryptophan and produces an anti-inflammatory metabolite, indole-3-propionic acid (IPA). Herein, we studied the effects of C. sporogenes and its bioactive metabolite, IPA, on skeletal muscle development and chronic inflammation in mice. In the in vivo study, the muscle tissues and serum samples of mice with C. sporogenes supplementation were used to analyze the effects of C. sporogenes on muscle metabolism; the IPA content was determined by metabonomics and ELISA. In an in vitro study, C2C12 cells were exposed to lipopolysaccharide (LPS) alone or LPS + IPA to verify the effect of IPA on muscle cell inflammation by transcriptome, and the involved mechanism was revealed by different functional assays. We observed that C. sporogenes colonization significantly increased the body weight and muscle weight gain, as well as the myogenic regulatory factors' (MRFs) expression. In addition, C. sporogenes significantly improved host IPA content and decreased pro-inflammatory cytokine levels in the muscle tissue of mice. Subsequently, we confirmed that IPA promoted C2C12 cells' proliferation by activating MRF signaling. IPA also effectively protected against LPS-induced C2C12 cells inflammation by activating Pregnane X Receptor and restoring the inhibited miR-26a-2-3p expression. miR-26a-2-3p serves as a novel muscle inflammation regulatory factor that could directly bind to the 3'-UTR of IL-1ß, a key initiator factor in inflammation. The results suggested that C. sporogenes with its functional metabolite IPA not only helps muscle growth development, but also protects against inflammation, partly by the IPA/ miR-26a-2-3p /IL-1ß cascade.

Cardiac aorta-derived extracellular matrix scaffold enhances critical mediators of angiogenesis in isoproterenol-induced myocardial infarction mice.

An incapability to improve lost cardiac muscle caused by acute ischemic injury remains the most important deficiency of current treatments to prevent heart failure. We investigated whether cardiomyocytes culturing on cardiac aorta-derived extracellular matrix scaffold has advantageous effects on cardiomyocytes survival and angiogenesis biomarkers' expression. Ten male NMRI mice were randomly divided into two groups: (1) control (healthy mice) and (2) myocardial infarction (MI)-induced model group (Isoproterenol/subcutaneously injection/single dose of 85 mg/kg). Two days after isoproterenol injection, all animals were sacrificed to isolate cardiomyocytes from myocardium tissues. The fresh thoracic aorta was obtained from male NMRI mice and decellularized using 4% sodium deoxycholate and 2000 kU DNase-I treatments. Control and MI-derived cardiomyocytes were seeded on decellularized cardiac aorta (DCA) considered three-dimensional (3D) cultures. To compare, the isolated cardiomyocytes from control and MI groups were also cultured as a two-dimensional (2D) culture system for 14 days. The cell viability was examined by MTT assay. The expression levels of Hif-1α and VEGF genes and VEGFR1 protein were tested by real-time PCR and western blotting, respectively. Moreover, the amount of VEGF protein was evaluated in the conditional media of the 2D and 3D systems. The oxidative stress was assessed via MDA assay. Hif-1α and VEGF genes were downregulated in MI groups compared to controls. However, the resulting data showed that decellularized cardiac aorta matrices positively affect the expression of Hif-1α and VEGF genes. The expression level of VEGFR1 protein was significantly (p ≤ 0.01) upregulated in both MI and healthy cell groups cultured on decellularized cardiac aorta matrices as a 3D system compared to the MI cell group cultured in the 2D systems. Furthermore, MDA concentration significantly decreased in 3D-cultured cells (MI and healthy cell groups) rather than the 2D-cultured MI group (p ≤ 0.015). The findings suggest that cardiac aorta-derived extracellular scaffold by preserving VEGF, improving the cell viability, and stimulating angiogenesis via upregulating Hif-1α, VEGF, and VEGFR1 in cardiomyocytes could be considered as a potential approach along with another therapeutic method to reduce the complications of myocardial infarction and control the progressive pathological conditions related to MI.

Effect of Ashwagandha Withanolides on Muscle Cell Differentiation.

Withania somnifera (Ashwagandha) is used in Indian traditional medicine, Ayurveda, and is believed to have a variety of health-promoting effects. The molecular mechanisms and pathways underlying these effects have not yet been sufficiently explored. In this study, we investigated the effect of Ashwagandha extracts and their major withanolides (withaferin A and withanone) on muscle cell differentiation using C2C12 myoblasts. We found that withaferin A and withanone and Ashwagandha extracts possessing different ratios of these active ingredients have different effects on the differentiation of C2C12. Withanone and withanone-rich extracts caused stronger differentiation of myoblasts to myotubes, deaggregation of heat- and metal-stress-induced aggregated proteins, and activation of hypoxia and autophagy pathways. Of note, the Parkinson's disease model of Drosophila that possess a neuromuscular disorder showed improvement in their flight and climbing activity, suggesting the potential of Ashwagandha withanolides for the management of muscle repair and activity.

Metformin and sodium dichloroacetate effects on proliferation, apoptosis, and metabolic activity tested alone and in combination in a canine prostate and a bladder cancer cell line.

An important approach in tumor therapy is combining substances with different action mechanisms aiming to enhance the antineoplastic effect, decrease the therapeutic dosage, and avoid resistance mechanisms. Moreover, evaluating compounds already approved for the treatment of non-neoplastic diseases is promising for new antineoplastic therapies. Sodium dichloroacetate (DCA) reactivates oxidative phosphorylation in the cancer cell mitochondria, reducing apoptosis resistance in cancer cells. Furthermore, metformin inhibits the proliferation of tumor cells and CD133+ cancer -stem-like cells. In the present study, we evaluated the independent and synergistic effect of metformin and DCA on the metabolic activity, cell proliferation, and apoptosis of a canine prostate adenocarcinoma (Adcarc1258) and a transitional cell carcinoma cell line (TCC1506) in comparison to a primary canine fibroblast culture. Determining metformin uptake in tumor cells was performed by quantitative HPLC. Depending on the dosage, metformin as a single agent inhibited the metabolic activity and cell proliferation of the tumor cells, showing only minor effects on the fibroblasts. Furthermore, 1 mM metformin increased apoptosis over 96 h in the tumor cell lines but not in fibroblasts. Additionally, metformin uptake into the tumor cells in vitro was measurable by quantitative HPLC. Synergistic effects for the combination therapy were observed in both neoplastic cell lines as well as in the fibroblasts. Based on these results, metformin might be a promising therapeutic agent for canine urogenital tumors. Further studies on kinetics, toxicology, bioavailability, and application of metformin in dogs are necessary.

Activation of SIRT1 by Resveratrol Alleviates Pressure Overload-Induced Cardiac Hypertrophy via Suppression of TGF-ß1 Signaling.

INTRODUCTION: Silent information regulator 1 (SIRT1) has been extensively investigated in the cardiovascular system and has been shown to play a pivotal role in mediating cell death/survival, energy production, and oxidative stress. However, the functional role of SIRT1 in pressure overload-induced cardiac hypertrophy and dysfunction remains unclear. Resveratrol (Rsv), a widely used activator of SIRT1, has been reported to protect against cardiovascular disease. We here examine whether activation of SIRT1 by Rsv attenuate pressure overload-induced cardiac hypertrophy and to identify the underlying molecular mechanisms. METHODS: In vivo, rat model of pressure overload-induced myocardial hypertrophy was established by abdominal aorta constriction (AAC) procedure. In vitro, Angiotensin II (Ang II) was applied to induce hypertrophy in cultured neonatal rat cardiomyocytes (NCMs). Hemodynamics and histological analyses of the heart were evaluated. The expression of SIRT1, transforming growth factor-ß1 (TGF-ß1)/phosphorylated (p)-small mother against decapentaplegic (Smad)3 and hypertrophic markers were determined by immunofluorescence, real-time PCR, and Western blotting techniques. RESULTS: In the current study, Rsv treatment improved left ventricular function and reduced left ventricular hypertrophy and cardiac fibrosis significantly in the pressure overload rats. The expression of SIRT1 was significantly reduced, while the expression of TGF-ß1/p-Smad3 was significantly enhanced in AAC afflicted rat heart. Strikingly, treatment with Rsv restored the expressions of SIRT1 and TGF-ß1/p-Smad3 under AAC influence. However, SIRT1 inhibitor Sirtinol (Snl) markedly prevented the effects of Rsv, which suggest that SIRT1 signaling pathway was involved in the cardiac protective effect of Rsv. In vitro studies performed in Ang II-induced hypertrophy in NCMs confirmed the cardiac protective effect of Rsv. Furthermore, the study presented that SIRT1 negatively correlated with the cardiac hypertrophy, cardiac fibrosis, and the TGF-ß1/p-Smad3 expression. CONCLUSIONS: Taken together, these results indicated that activation of SIRT1 by Rsv attenuates cardiac hypertrophy, cardiac fibrosis, and improves cardiac function possibly via regulation of the TGF-ß1/p-Smad3 signaling pathway. Our study may provide a potential therapeutic strategy for cardiac hypertrophy.

Metformin Increases Protein Phosphatase 2A Activity in Primary Human Skeletal Muscle Cells Derived from Lean Healthy Participants.

OBJECTIVE: To investigate if PP2A plays a role in metformin-induced insulin sensitivity improvement in human skeletal muscle cells. Participants. Eight lean insulin-sensitive nondiabetic participants (4 females and 4 males; age: 21.0 ± 1.0 years; BMI: 22.0 ± 0.7 kg/m2; 2-hour OGTT: 97.0 ± 6.0 mg/dl; HbA1c: 5.3 ± 0.1%; fasting plasma glucose: 87.0 ± 2.0 mg/dl; M value; 11.0 ± 1.0 mg/kgBW/min). DESIGN: A hyperinsulinemic-euglycemic clamp was performed to assess insulin sensitivity in human subjects, and skeletal muscle biopsy samples were obtained. Primary human skeletal muscle cells (shown to retain metabolic characteristics of donors) were cultured from these muscle biopsies that included 8 lean insulin-sensitive participants. Cultured cells were expanded, differentiated into myotubes, and treated with 50 µM metformin for 24 hours before harvesting. PP2Ac activity was measured by a phosphatase activity assay kit (Millipore) according to the manufacturer's protocol. RESULTS: The results indicated that metformin significantly increased the activity of PP2A in the myotubes for all 8 lean insulin-sensitive nondiabetic participants, and the average fold increase is 1.54 ± 0.11 (P < 0.001). CONCLUSIONS: These results provided the first evidence that metformin can activate PP2A in human skeletal muscle cells derived from lean healthy insulin-sensitive participants and may help to understand metformin's action in skeletal muscle in humans.

Coronary hypercontractility to acidosis owes to the greater activity of TMEM16A/ANO1 in the arterial smooth muscle cells.

BACKGROUND: Severe acidosis deteriorates cardiac injury. Rat coronary arteries (RCAs) are unusually hypercontractive to extracellular (o) acidosis (EA). TMEM16A-encoded anoctamin 1 (ANO1), a Ca2+-activated chloride channel (CaCC), plays an important role in regulating coronary arterial tension. PURPOSE: We tested the possibility that the activation of CaCCs in the arterial smooth muscle cell (ASMC) contributes to EA-induced RCA constriction. METHODS: ANO1 expression was detected with immunofluorescence staining and Western blot. TMEM16A mRNA was assessed with quantitative Real-Time PCR. Cl- currents and membrane potentials were quantified with a patch clamp. The vascular tension was recorded with a myograph. Intracellular (i) level of Cl- and Ca2+ was measured with fluorescent molecular probes. RESULTS: ANO1 was expressed in all tested arterial myocytes, but was much more abundant in RCA ASMCs as compared with ASMCs isolated from rat cerebral basilar, intrarenal and mesenteric arteries. EA reduced [Cl-]i levels, augmented CaCC currents exclusively in RCA ASMCs and depolarized RCA ASMCs to a greater extent. Cl- deprivation, which depleted [Cl-]i by incubating the arteries or their ASMCs in Cl--free bath solution, decreased EA-induced [Cl-]i reduction, diminished EA-induced CaCC augmentation and time-dependently depressed EA-induced RCA constriction. Inhibitor studies showed that these EA-induced effects including RCA constriction, CaCC current augmentation, [Cl-]i reduction and/or [Ca2+]i elevation were depressed by various Cl- channel blockers, [Ca2+]i release inhibitors and L-type voltage-gated Ca2+ channel inhibitor nifedipine. ANO1 antibody attenuated all observed changes induced by EA in RCA ASMCs. CONCLUSION: The greater activity of RCA ASMC CaCCs complicated with an enhanced Ca2+ mobilization from both [Ca2+]i release and [Ca2+]o influx plays a pivotal role in the distinctive hypercontractility of RCAs to acidosis. Translation of these findings to human beings may lead to a new conception in our understanding and treating cardiac complications in severe acidosis.

Acetate Does Not Affect Palmitate Oxidation and AMPK Phosphorylation in Human Primary Skeletal Muscle Cells.

Our recent in vivo human studies showed that colonic administration of sodium acetate (SA) resulted in increased circulating acetate levels, which was accompanied by increments in whole-body fat oxidation in overweight-obese men. Since skeletal muscle has a major role in whole-body fat oxidation, we aimed to investigate effects of SA on fat oxidation and underlying mechanisms in human primary skeletal muscle cells (HSkMC). We investigated the dose (0-5 mmol/L) and time (1, 4, 20, and 24 h) effect of SA on complete and incomplete endogenous and exogenous oxidation of 14C-labeled palmitate in HSkMC derived from a lean insulin sensitive male donor. Both physiological (0.1 and 0.25 mmol/L) and supraphysiological (0.5, 1 and 5 mmol/L) concentrations of SA neither increased endogenous nor exogenous fat oxidation over time in HSkMC. In addition, no effect of SA was observed on Thr172-AMPKα phosphorylation. In conclusion, our previously observed in vivo effects of SA on whole-body fat oxidation in men may not be explained via direct effects on HSkMC fat oxidation. Nevertheless, SA-mediated effects on whole-body fat oxidation may be triggered by other mechanisms including gut-derived hormones or may occur in other metabolically active tissues.

Sex-related differences in response to masseteric injections of glutamate and nerve growth factor in healthy human participants.

The neurophysiological mechanisms underlying NGF-induced masseter muscle sensitization and sex-related differences in its effect are not well understood in humans. Therefore, this longitudinal cohort study aimed to investigate the effect of NGF injection on the density and expression of substance P, NMDA-receptors and NGF by the nerve fibers in the human masseter muscle, to correlate expression with pain characteristics, and to determine any possible sex-related differences in these effects of NGF. The magnitude of NGF-induced mechanical sensitization and pain during oral function was significantly greater in women than in men (P < 0.050). Significant positive correlations were found between nerve fiber expression of NMDA-receptors and peak pain intensity (rs = 0.620, P = 0.048), and expression of NMDA-receptors by putative nociceptors and change in temporal summation pain after glutamate injection (rs = 0.561, P = 0.003). In women, there was a significant inverse relationship between the degree of NGF-induced mechanical sensitization and the change in nerve fiber expression of NMDA-receptors alone (rs = - 0.659, P = 0.013), and in combination with NGF (rs = - 0.764, P = 0.001). In conclusion, women displayed a greater magnitude of NGF-induced mechanical sensitization that also was associated with nerve fibers expression of NMDA-receptors, when compared to men. The present findings suggest that, in women, increased peripheral NMDA-receptor expression could be associated with masseter muscle pain sensitivity.

The Effects of Marine Algal Polyphenols, Phlorotannins, on Skeletal Muscle Growth in C2C12 Muscle Cells via Smad and IGF-1 Signaling Pathways.

Skeletal muscle is an important tissue in energy metabolism and athletic performance. The use of effective synthetic supplements and drugs to promote muscle growth is limited by various side effects. Moreover, their use is prohibited by anti-doping agencies; hence, natural alternatives are needed. Therefore, we evaluated the muscle growth effect of substances that can act like synthetic supplements from edible marine algae. First, we isolated six marine algal polyphenols belonging to the phlorotannin class, namely dieckol (DK), 2,7″-phloroglucinol-6,6'-bieckol (PHB), phlorofucofuroeckol A (PFFA), 6,6'-bieckol (6,6-BK), pyrogallol-phloroglucinol-6,6'-bieckol (PPB), and phloroglucinol (PG) from an edible brown alga, Ecklonia cava and evaluated their effects on C2C12 myoblasts proliferation and differentiation. Of the six phlorotannin isolates evaluated, DK and PHB induced the highest degree of C2C12 myoblast proliferation. In addition, DK and PHB regulates myogenesis by down-regulating the Smad signaling, a negative regulator, and up-regulating the insulin-like growth factor-1 (IGF-1) signaling, a positive regulator. Interestingly, DK and PHB bind strongly to myostatin, which is an inhibitor of myoblast proliferation, while also binding to IGF-1 receptors. Moreover, they bind to IGF-1 receptor. These results suggest that DK and PHB are potential natural muscle building supplements and could be a safer alternative to synthetic drugs.

The involvement of Sestrin2 in the effect of IGF-I and leucine on mTROC1 activity in C2C12 and L6 myocytes.

OBJECTIVE: IGF-I and branched-chain amino acids have been reported to promote muscle hypertrophy via the stimulation of protein synthesis. Sestrin2, the function of which is regulated by leucine, has been reported to attenuate the activity of the mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) that stimulates protein synthesis. The objective of this study was to examine whether IGF-I modulates Sestrin2 abundance and to clarify the involvement of Sestrin2 in the effect of IGF-I and leucine on mTROC1. DESIGN: C2C12 and L6 myocytes were stimulated by leucine (1 mM) with or without pretreatment with IGF-I (100 ng/mL). Phosphorylation of p70 S6 kinase (S6K) and 4E-binding protein 1 (4E-BP1), both of which are targets of the mTORC1, was examined by western blotting. Effects of Sestrin2 small interfering RNA (siRNA) on the actions of leucine and IGF-I were examined. Sestrin2 mRNA and protein levels were also determined after Sestrin2 siRNA. RESULTS: Leucine increased the phosphorylation of S6K and 4E-BP1 in a dose-dependent manner. Pretreatment with IGF-I for 5 h further increased the stimulatory effect of leucine on the phosphorylation of S6K and 4E-BP1 in C2C12 cells. IGF-I increased Sestrin2 protein and messenger RNA levels. Sestrin2 siRNA increased or tended to increase basal phosphorylation of 4E-BP1 and decreased the leucine-induced phosphorylation in C2C12 and L6 cells, in particular after IGF-I treatment, suggesting the involvement of Sestrin2 in the action of leucine and IGF-I. The net increase in leucine-induced 4E-BP1 phosphorylation appeared to be attenuated by Sestrin2 siRNA. Likewise, Sestrin2 siRNA attenuated leucine-induced S6K phosphorylation in L6 cells. However, Sestrin2 siRNA did not influence leucine-induced S6K phosphorylation in C2C12 cells. CONCLUSIONS: IGF-I and leucine cooperatively increased mTORC1 activity in C2C12 cells. IGF-I increased Sestrin2. Sestrin2 siRNA experiments showed that Sestrin2 was involved in the effect of leucine and IGF-I on mTORC1 activity in C2C12 and L6 cells, and suggested that increased Sestrin2 by IGF-I pretreatment might play a role in enhancing the effect of leucine on mTORC1.

Effect of Muscle Cell Preservation on Viability and Differentiation of Hamstring Tendon Graft In Vitro.

Muscle tissue is often removed during hamstring tendon graft preparation for anterior cruciate ligament (ACL) reconstruction. The purpose of the study was to test whether preservation of muscle remnants on a tendon graft is beneficial to the graft healing process following ACL reconstruction. Co-culturing of tendon-derived cells (TDCs) and muscle-derived cells (MDCs) was performed at various ratios, and their potential for cell viability and multilineage differentiation was compared to a single TDC cell group. Ligamentous and chondrogenic differentiation was most enhanced when a small population of MDCs was co-cultured with TDCs (6:2 co-culture group). Cell viability and osteogenic differentiation were proportionally enhanced with increasing MDC population size. MDCs co-cultured with TDCs possess both the ability to enhance cell viability and differentiate into other cell lineages.

Ursolic Acid Lactone Obtained from Eucalyptus tereticornis Increases Glucose Uptake and Reduces Inflammatory Activity and Intracellular Neutral Fat: An In Vitro Study.

Obesity has a strong relationship to insulin resistance and diabetes mellitus, a chronic metabolic disease that alters many physiological functions. Naturally derived drugs have aroused great interest in treating obesity, and triterpenoids are natural compounds with multiple biological activities and antidiabetic mechanisms. Here, we evaluated the bioactivity of ursolic acid lactone (UAL), a lesser-known triterpenoid, obtained from Eucalyptus tereticornis. We used different cell lines to show for the first time that this molecule exhibits anti-inflammatory properties in a macrophage model, increases glucose uptake in insulin-resistant muscle cells, and reduces triglyceride content in hepatocytes and adipocytes. In 3T3-L1 adipocytes, UAL inhibited the expression of genes involved in adipogenesis and lipogenesis, enhanced the expression of genes involved in fat oxidation, and increased AMP-activated protein kinase phosphorylation. The range of biological activities demonstrated in vitro indicates that UAL is a promising molecule for fighting diabetes.

Enhanced growth and myogenic differentiation of spheroid-derived C2C12 cells.

Among many factors of controlling stem cell differentiation, the key transcription factor upregulation via physical force is a good strategy on the lineage-specific differentiation of stem cells. The study aimed to compare growth and myogenic potentials between the parental cells (PCs) and the 1-day-old C2C12 spheroid-derived cells (SDCs) in two-dimensional (2D) and three-dimensional (3D) culture conditions through examination of the cell proliferation and the expression of myogenic genes. The data showed that 1-day-old spheroids had more intense expression of MyoD gene with respect to the PCs. The proliferation of the SDCs is significantly higher than the PCs in a time-dependent manner. The SDCs had also significantly higher myogenic potential than the PCs in 2D and 3D culture conditions. The results suggest that MyoD gene upregulation through cell-cell contacts is the good approach for preparation of seed cells in muscle tissue engineering.

PUFA Treatment Affects C2C12 Myocyte Differentiation, Myogenesis Related Genes and Energy Metabolism.

Polyunsaturated fatty acids (PUFAs) are the main components of cell membrane affecting its fluidity, signaling processes and play a vital role in muscle cell development. The effects of docosahexaenoic acid (DHA) on myogenesis are well known, while the effects of arachidonic acid (AA) are largely unclear. The purpose of this study is to evaluate the effect of two PUFAs (DHA and AA) on cell fate during myogenic processes, Wnt signaling and energy metabolism by using the C2C12 cells. The cells were treated with different concentrations of AA or DHA for 48 h during the differentiation period. PUFA treatment increased mRNA level of myogenic factor 5 (Myf5), which is involved in early stage of myoblast proliferation. Additionally, PUFA treatment prevented myoblast differentiation, indicated by decreased myotube fusion index and differentiation index in parallel with reduced mRNA levels of myogenin (MyoG). After PUFA withdrawal, some changes in cell morphology and myosin heavy chain mRNA levels were still observed. Expression of genes associated with Wnt signaling pathway, and energy metabolism changed in PUFA treatment in a dose and time dependent manner. Our data suggests that PUFAs affect the transition of C2C12 cells from proliferation to differentiation phase by prolonging proliferation and preventing differentiation.