Peptide derived from SLAMF1 prevents TLR4-mediated inflammation in vitro and in vivo.

Inflammation plays a crucial role in the development and progression of many diseases, and is often caused by dysregulation of signalling from pattern recognition receptors, such as TLRs. Inhibition of key protein-protein interactions is an attractive target for treating inflammation. Recently, we demonstrated that the signalling lymphocyte activation molecule family 1 (SLAMF1) positively regulates signalling downstream of TLR4 and identified the interaction interface between SLAMF1 and the TLR4 adaptor protein TRIF-related adapter molecule (TRAM).

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.

Alpha-cyclodextrin inhibits cholesterol crystal-induced complement-mediated inflammation: A potential new compound for treatment of atherosclerosis.

Background And Aims: Cholesterol crystal (CC)-induced inflammation is a critical step in the development of atherosclerosis. CCs activate the complement system and induce an inflammatory response resulting in phagocytosis of the CCs, production of reactive oxygen species (ROS) and release of cytokines. The cyclodextrin 2-hydroxypropyl-β-cyclodextrin has been found to reduce CC-induced complement activation and induce regression of established atherosclerotic plaques in a mouse model of atherosclerosis, thus inhibition of complement with cyclodextrins is a potential new strategy for treatment of inflammation during atherosclerosis.

Serum Omega-6 Fatty Acids and Immunology-Related Gene Expression in Peripheral Blood Mononuclear Cells: A Cross-Sectional Analysis in Healthy Children.

Scope: Some studies suggest that a high dietary intake of omega-6 fatty acids is pro-inflammatory. However, whether omega-6 fatty acids actually cause pathogenic inflammation in humans is debated. Therefore, the associations between expression of immunology-related genes in peripheral blood mononuclear cells (PBMCs) and serum total omega-6 PUFA status are investigated.

Increased triacylglycerol - Fatty acid substrate cycling in human skeletal muscle cells exposed to eicosapentaenoic acid.

It has previously been shown that pretreatment of differentiated human skeletal muscle cells (myotubes) with eicosapentaenoic acid (EPA) promoted increased uptake of fatty acids and increased triacylglycerol accumulation, compared to pretreatment with oleic acid (OA) and palmitic acid (PA). The aim of the present study was to examine whether EPA could affect substrate cycling in human skeletal muscle cells by altering lipolysis rate of intracellular TAG and re-esterification of fatty acids. Fatty acid metabolism was studied in human myotubes using a mixture of fatty acids, consisting of radiolabelled oleic acid as tracer (14C-OA) together with EPA or PA.

Cyclodextrin Reduces Cholesterol Crystal-Induced Inflammation by Modulating Complement Activation.

Cholesterol crystals (CC) are abundant in atherosclerotic plaques and promote inflammatory responses via the complement system and inflammasome activation. Cyclic oligosaccharide 2-hydroxypropyl-β-cyclodextrin (BCD) is a compound that solubilizes lipophilic substances. Recently we have shown that BCD has an anti-inflammatory effect on CC via suppression of the inflammasome and liver X receptor activation.

Loss of perilipin 2 in cultured myotubes enhances lipolysis and redirects the metabolic energy balance from glucose oxidation towards fatty acid oxidation.

Lipid droplet (LD) coating proteins are essential for the formation and stability of intracellular LDs. Plin2 is an abundant LD coating protein in skeletal muscle, but its importance for muscle function is unclear. We show that myotubes established from mice contain reduced content of LDs and accumulate less oleic acid (OA) in triacylglycerol (TAG) due to elevated LD hydrolysis in comparison with myotubes.

Cholesterol Crystals Activate the Lectin Complement Pathway via Ficolin-2 and Mannose-Binding Lectin: Implications for the Progression of Atherosclerosis.

Cholesterol crystals (CC) play an essential role in the formation of atherosclerotic plaques. CC activate the classical and the alternative complement pathways, but the role of the lectin pathway is unknown. We hypothesized that the pattern recognition molecules (PRMs) from the lectin pathway bind CC and function as an upstream innate inflammatory signal in the pathophysiology of atherosclerosis.

Cyclodextrin promotes atherosclerosis regression via macrophage reprogramming.

Atherosclerosis is an inflammatory disease linked to elevated blood cholesterol concentrations. Despite ongoing advances in the prevention and treatment of atherosclerosis, cardiovascular disease remains the leading cause of death worldwide. Continuous retention of apolipoprotein B-containing lipoproteins in the subendothelial space causes a local overabundance of free cholesterol.

Reconstituted High-Density Lipoprotein Attenuates Cholesterol Crystal-Induced Inflammatory Responses by Reducing Complement Activation.

Chronic inflammation of the arterial wall is a key element in the development of atherosclerosis, and cholesterol crystals (CC) that accumulate in plaques are associated with initiation and progression of the disease. We recently revealed a link between the complement system and CC-induced inflammasome caspase-1 activation, showing that the complement system is a key trigger in CC-induced inflammation. HDL exhibits cardioprotective and anti-inflammatory properties thought to explain its inverse correlation to cardiovascular risk.

Primary defects in lipolysis and insulin action in skeletal muscle cells from type 2 diabetic individuals.

A decrease in skeletal muscle lipolysis and hormone sensitive-lipase (HSL) expression has been linked to insulin resistance in obesity. The purpose of this study was to identify potential intrinsic defects in lipid turnover and lipolysis in myotubes established from obese and type 2 diabetic subjects. Lipid trafficking and lipolysis were measured by pulse-chase assay with radiolabeled substrates in myotubes from non-obese/non-diabetic (lean), obese/non-diabetic (obese) and obese/diabetic (T2D) subjects.

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.

Cholesterol crystals induce complement-dependent inflammasome activation and cytokine release.

Inflammation is associated with development of atherosclerosis, and cholesterol crystals (CC) have long been recognized as a hallmark of atherosclerotic lesions. CC appear early in the atheroma development and trigger inflammation by NLRP3 inflammasome activation. In this study we hypothesized whether CC employ the complement system to activate inflammasome/caspase-1, leading to release of mature IL-1β, and whether complement activation regulates CC-induced cytokine production.

PPARδ activation in human myotubes increases mitochondrial fatty acid oxidative capacity and reduces glucose utilization by a switch in substrate preference.

The role of peroxisome proliferator-activated receptor δ (PPARδ) activation on global gene expression and mitochondrial fuel utilization were investigated in human myotubes. Only 21 genes were up-regulated and 3 genes were down-regulated after activation by the PPARδ agonist GW501516. Pathway analysis showed up-regulated mitochondrial fatty acid oxidation, TCA cycle and cholesterol biosynthesis.

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.

Palmitic acid follows a different metabolic pathway than oleic acid in human skeletal muscle cells; lower lipolysis rate despite an increased level of adipose triglyceride lipase.

Development of insulin resistance is positively associated with dietary saturated fatty acids and negatively associated with monounsaturated fatty acids. To clarify aspects of this difference we have compared the metabolism of oleic (OA, monounsaturated) and palmitic acids (PA, saturated) in human myotubes. Human myotubes were treated with 100μM OA or PA and the metabolism of [(14)C]-labeled fatty acid was studied.

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.

The liver X receptor modulator 22(S)-hydroxycholesterol exerts cell-type specific effects on lipid and glucose metabolism.

The aim of this study was to explore the effects of 22(S)-hydroxycholesterol (22(S)-HC) on lipid and glucose metabolism in human-derived cells from metabolic active tissues. Docking of T0901317 and 22(S)-HC showed that both substances fitted into the ligand binding domain of liver X receptors (LXR). Results show that while several lipogenic genes were induced by T0901317 in myotubes, HepG2 cells and SGBS cells, effect of 22(S)-HC varied more between cell types.

Oxidation of intramyocellular lipids is dependent on mitochondrial function and the availability of extracellular fatty acids.

Obesity and insulin resistance are related to both enlarged intramyocellular triacylglycerol stores and accumulation of lipid intermediates. We investigated how lipid overflow can change the oxidation of intramyocellular lipids (ICL(OX)) and intramyocellular lipid storage (ICL). These experiments were extended by comparing these processes in primary cultured myotubes established from healthy lean and obese type 2 diabetic (T2D) individuals, two extremes in a range of metabolic phenotypes.