Distinct microRNA and protein profiles of extracellular vesicles secreted from myotubes from morbidly obese donors with type 2 diabetes in response to electrical pulse stimulation.

Lifestyle disorders like obesity, type 2 diabetes (T2D), and cardiovascular diseases can be prevented and treated by regular physical activity. During exercise, skeletal muscles release signaling factors that communicate with other organs and mediate beneficial effects of exercise. These factors include myokines, metabolites, and extracellular vesicles (EVs).

Insight Into the Metabolic Adaptations of Electrically Pulse-Stimulated Human Myotubes Using Global Analysis of the Transcriptome and Proteome.

Electrical pulse stimulation (EPS) has proven to be a useful tool to interrogate cell-specific responses to muscle contraction. In the present study, we aimed to uncover networks of signaling pathways and regulatory molecules responsible for the metabolic effects of exercise in human skeletal muscle cells exposed to chronic EPS. Differentiated myotubes from young male subjects were exposed to EPS protocol 1 (i.

The effect of toll-like receptor ligands on energy metabolism and myokine expression and secretion in cultured human skeletal muscle cells.

Skeletal muscle plays an important role in glycaemic control and metabolic homeostasis, making it a tissue of interest with respect to type 2 diabetes mellitus. The aim of the present study was to determine if ligands of Toll-like receptors (TLRs) could have an impact on energy metabolism and myokine expression and secretion in cultured human skeletal muscle cells. The myotubes expressed mRNA for TLRs 1-6.

Substrate oxidation in primary human skeletal muscle cells is influenced by donor age.

Primary human myotubes represent an alternative system to intact skeletal muscle for the study of human diseases related to changes in muscle energy metabolism. This work aimed to study if fatty acid and glucose metabolism in human myotubes in vitro were related to muscle of origin, donor gender, age, or body mass index (BMI). Myotubes from a total of 82 donors were established from three different skeletal muscles, i.

Increased Glycolysis and Higher Lactate Production in Hyperglycemic Myotubes.

Previous studies have shown that chronic hyperglycemia impairs glucose and fatty acid oxidation in cultured human myotubes. To further study the hyperglycemia-induced suppression of oxidation, lactate oxidation, mitochondrial function and glycolytic rate were evaluated. Further, we examined the intracellular content of reactive oxygen species (ROS), production of lactate and conducted pathway-ANOVA analysis on microarray data.

Electrical Pulse Stimulation of Primary Human Skeletal Muscle Cells.

Electrical pulse stimulation (EPS) is an in vitro method of inducing contractions in cultured skeletal muscle cells of human and animal origin. Motor neuron activation of muscle fibers can be replaced by applying EPS on differentiated skeletal muscle cells (myotubes) in culture (Thelen et al. Biochemical J 321:845-848, 1997, Fujita et al.

Utilization of lactic acid in human myotubes and interplay with glucose and fatty acid metabolism.

Once assumed only to be a waste product of anaerobe glycolytic activity, lactate is now recognized as an energy source in skeletal muscles. While lactate metabolism has been extensively studied in vivo, underlying cellular processes are poorly described. This study aimed to examine lactate metabolism in cultured human myotubes and to investigate effects of lactate exposure on metabolism of oleic acid and glucose.

Myotubes from severely obese type 2 diabetic subjects accumulate less lipids and show higher lipolytic rate than myotubes from severely obese non-diabetic subjects.

About 80% of patients with type 2 diabetes are classified as overweight. However, only about 1/3 of severely obese subjects have type 2 diabetes. This indicates that several severely obese individuals may possess certain characteristics that protect them against type 2 diabetes.

Myotubes from lean and severely obese subjects with and without type 2 diabetes respond differently to an in vitro model of exercise.

Exercise improves insulin sensitivity and oxidative capacity in skeletal muscles. However, the effect of exercise on substrate oxidation is less clear in obese and type 2 diabetic subjects than in lean subjects. We investigated glucose and lipid metabolism and gene expression after 48 h with low-frequency electrical pulse stimulation (EPS), as an in vitro model of exercise, in cultured myotubes established from lean nondiabetic subjects and severely obese subjects (BMI ≥ 40 kg/m(2)) with and without type 2 diabetes.

Are cultured human myotubes far from home?

Satellite cells can be isolated from skeletal muscle biopsies, activated to proliferating myoblasts and differentiated into multinuclear myotubes in culture. These cell cultures represent a model system for intact human skeletal muscle and can be modulated ex vivo. The advantages of this system are that the most relevant genetic background is available for the investigation of human disease (as opposed to rodent cell cultures), the extracellular environment can be precisely controlled and the cells are not immortalized, thereby offering the possibility of studying innate characteristics of the donor.

Remodeling of oxidative energy metabolism by galactose improves glucose handling and metabolic switching in human skeletal muscle cells.

Cultured human myotubes have a low mitochondrial oxidative potential. This study aims to remodel energy metabolism in myotubes by replacing glucose with galactose during growth and differentiation to ultimately examine the consequences for fatty acid and glucose metabolism. Exposure to galactose showed an increased [(14)C]oleic acid oxidation, whereas cellular uptake of oleic acid uptake was unchanged.

Correction: Electrical Pulse Stimulation of Cultured Human Skeletal Muscle Cells as an In Vitro Model of Exercise.

[This corrects the article DOI: 10.1371/journal.pone.

Electrical pulse stimulation of cultured human skeletal muscle cells as an in vitro model of exercise.

Background And Aims: Physical exercise leads to substantial adaptive responses in skeletal muscles and plays a central role in a healthy life style. Since exercise induces major systemic responses, underlying cellular mechanisms are difficult to study in vivo. It was therefore desirable to develop an in vitro model that would resemble training in cultured human myotubes.

Chronic hyperglycemia reduces substrate oxidation and impairs metabolic switching of human myotubes.

Skeletal muscle of insulin resistant individuals is characterized by lower fasting lipid oxidation and reduced ability to switch between lipid and glucose oxidation. The purpose of the present study was to examine if chronic hyperglycemia would impair metabolic switching of myotubes. Human myotubes were treated with or without chronic hyperglycemia (20mmol/l glucose for 4 days), and metabolism of [(14)C]oleic acid (OA) and [(14)C]glucose was studied.

Eicosapentaenoic acid (20:5 n-3) increases fatty acid and glucose uptake in cultured human skeletal muscle cells.

This study was conducted to evaluate the chronic effects of eicosapentaenoic acid (EPA) on fatty acid and glucose metabolism in human skeletal muscle cells. Uptake of [14C]oleate was increased >2-fold after preincubation of myotubes with 0.6 mM EPA for 24 h, and incorporation into various lipid classes showed that cellular triacylgycerol (TAG) and phospholipids were increased 2- to 3-fold compared with control cells.

Leptin expression in human primary skeletal muscle cells is reduced during differentiation.

We found leptin to be strongly expressed in undifferentiated human myoblasts derived from biopsies of the thigh (Musculus vastus lateralis). Both mRNA expression and secretion of leptin were reduced during in vitro differentiation into primary myotubes. However, the expression of the leptin receptor (OB-Rb) mRNA, was unchanged during differentiation of the muscle cells.

Skeletal muscle lipid accumulation in type 2 diabetes may involve the liver X receptor pathway.

Liver X receptors (LXRs) are important regulators of cholesterol and lipid metabolism and are also involved in glucose metabolism. However, the functional role of LXRs in human skeletal muscle is at present unknown. This study demonstrates that chronic ligand activation of LXRs by a synthetic LXR agonist increases the uptake, distribution into complex cellular lipids, and oxidation of palmitate as well as the uptake and oxidation of glucose in cultured human skeletal muscle cells.

Leukemia inhibitory factor reduces contractile function and induces alterations in energy metabolism in isolated cardiomyocytes.

Interleukin (IL)-6 related cytokines may be involved in the pathophysiology of heart failure. Leukemia inhibitory factor (LIF) is an IL-6 related cytokine, and elevated levels of LIF have been found in failing hearts. The aim of our study was to investigate how LIF may influence isolated cardiomyocytes.

Reduced lipid oxidation in skeletal muscle from type 2 diabetic subjects may be of genetic origin: evidence from cultured myotubes.

Insulin resistance in skeletal muscle in vivo is associated with reduced lipid oxidation and lipid accumulation. It is still uncertain whether changes in lipid metabolism represent an adaptive compensation at the cellular level or a direct expression of a genetic trait. Studies of palmitate metabolism in human myotubes established from control and type 2 diabetic subjects may solve this problem, as genetic defects are preserved and expressed in vitro.

Electrical stimulation improves insulin responses in a human skeletal muscle cell model of hyperglycemia.

Myoblasts from human skeletal muscle were isolated from needle biopsy samples of the vastus lateralis of young and healthy volunteers. Contaminating fibroblasts were removed, and myoblasts were fused into differentiated multinucleated myotubes. These myotubes manifested both basal and insulin-stimulated (1-100 nM) glucose transport and glycogen synthesis.