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The interplay between skeletal muscle and bone is primarily mechanical; however, biochemical crosstalk by secreted mediators has recently gained increased attention. The aim of this study was to investigate metabolic effects of conditioned medium from osteoblasts (OB-CM) on myotubes and vice versa. Human skeletal muscle cells incubated with OB-CM showed increased glucose uptake and oxidation, and mRNA expression of the glucose transporter (GLUT) 1, while fatty acid uptake and oxidation, and mRNA expression of the fatty acid transporter CD36 were decreased. This was supported by proteomic analysis, where expression of proteins involved in glucose uptake, glycolytic pathways, and the TCA cycle were enhanced, and expression of several proteins involved in fatty acid metabolism were reduced. Similar effects on energy metabolism were observed in human bone marrow stromal cells differentiated to osteoblastic cells incubated with conditioned medium from myotubes (SKM-CM), with increased glucose uptake and reduced oleic acid uptake. Proteomic analyses of the two conditioned media revealed many common proteins. Thus, our data may indicate a shift in fuel preference from fatty acid to glucose metabolism in both cell types, induced by conditioned media from the opposite cell type, possibly indicating a more general pattern in communication between these tissues., The interplay between skeletal muscle and bone is primarily mechanical; however, biochemical crosstalk by secreted mediators has recently gained increased attention. The aim of this study was to investigate metabolic effects of conditioned medium from osteoblasts (OB-CM) on myotubes and vice versa. Human skeletal muscle cells incubated with OB-CM showed increased glucose uptake and oxidation, and mRNA expression of the glucose transporter (GLUT) 1, while fatty acid uptake and oxidation, and mRNA expression of the fatty acid transporter CD36 were decreased. This was supported by proteomic analysis, where expression of proteins involved in glucose uptake, glycolytic pathways, and the TCA cycle were enhanced, and expression of several proteins involved in fatty acid metabolism were reduced. Similar effects on energy metabolism were observed in human bone marrow stromal cells differentiated to osteoblastic cells incubated with conditioned medium from myotubes (SKM-CM), with increased glucose uptake and reduced oleic acid uptake. Proteomic analyses of the two conditioned media revealed many common proteins. Thus, our data may indicate a shift in fuel preference from fatty acid to glucose metabolism in both cell types, induced by conditioned media from the opposite cell type, possibly indicating a more general pattern in communication between these tissues.

The antibiotic-tolerant biofilms present in tuberculous granulomas add an additional layer of complexity when treating mycobacterial infections, including tuberculosis (TB). For a more efficient treatment of TB, the biofilm forms of mycobacteria warrant specific attention. Here, we used Mycobacterium marinum (Mmr) as a biofilm-forming model to identify the abundant proteins covering the biofilm surface. We used biotinylation/streptavidin-based proteomics on the proteins exposed at the Mmr biofilm matrices in vitro to identify 448 proteins and ex vivo proteomics to detect 91 Mmr proteins from the mycobacterial granulomas isolated from adult zebrafish. In vitro and ex vivo proteomics data are available via ProteomeXchange with identifiers PXD033425 and PXD039416, respectively. Data comparisons pinpointed the molecular chaperone GroEL2 as the most abundant Mmr protein within the in vitro and ex vivo proteomes, while its paralog, GroEL1, with a known role in biofilm formation, was detected with slightly lower intensity values. To validate the surface exposure of these targets, we created in-house synthetic nanobodies (sybodies) against the two chaperones and identified sybodies that bind the mycobacterial biofilms in vitro and those present in ex vivo granulomas. Taken together, the present study reports a proof-of-concept showing that surface proteomics in vitro and ex vivo proteomics combined is a valuable strategy to identify surface-exposed proteins on the mycobacterial biofilm. Biofilm surface-binding nanobodies could be eventually used as homing agents to deliver biofilm-targeting treatments to the sites of persistent biofilm infection. IMPORTANCE With the currently available antibiotics, the treatment of TB takes months. The slow response to treatment is caused by antibiotic tolerance, which is especially common among bacteria that form biofilms. Such biofilms are composed of bacterial cells surrounded by the extracellular matrix. Both the matrix and the dormant

Regular physical exercise evokes profound physiological responses which are strongly associated with many health benefits. However, the details of cellular networks and mechanisms underlying the adaptive responses to exercise remain to be elucidated. We have previously shown the usefulness of electrical pulse stimulation (EPS) to investigate metabolic effects of exercise in cultured human myotubes. The aim of the present study was 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 were subjected to two different EPS protocols (protocol 1; 2 ms, 10 V, 0.1 Hz for 24 h or protocol 2; 2 ms, 30 V, and 1 Hz for 48 h). Fuel handling was assessed using radiolabeled substrates. The transcriptome, cell proteome, and secreted proteins from EPS-treated and untreated myotubes were analyzed using a combination of high-throughput RNA sequencing, microarray, and high-resolution liquid chromatography mass spectrometry. Independent validation of selected putative myokines were measured using ELISA or multiplex assay. Oxidative metabolism was enhanced in human myotubes exposed to EPS protocol 1. A total of 81 differentially regulated proteins and 952 differentially expressed genes (DEGs) were observed in the cells after EPS protocol 1. Gene ontology (GO) analysis indicated that significantly regulated proteins and genes were enriched in biological processes related to glycolytic pathways, positive regulation of fatty acid oxidation, and oxidative phosphorylation, as well as muscle contraction, autophagy/mitophagy, and oxidative stress. Moreover, proteomic identification of secreted proteins revealed extracellular levels of 137 proteins were changed in myotubes subjected to EPS protocol 1. We also found some degree of overlap between the DEGs found in myotubes submitted to EPS protocol 1 and protocol 2. Among these DEGs was a myokine, leukemia, Regular physical exercise evokes profound physiological responses which are strongly associated with many health benefits. However, the details of cellular networks and mechanisms underlying the adaptive responses to exercise remain to be elucidated. We have previously shown the usefulness of electrical pulse stimulation (EPS) to investigate metabolic effects of exercise in cultured human myotubes. The aim of the present study was 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 were subjected to two different EPS protocols (protocol 1; 2 ms, 10 V, 0.1 Hz for 24 h or protocol 2; 2 ms, 30 V, and 1 Hz for 48 h). Fuel handling was assessed using radiolabeled substrates. The transcriptome, cell proteome, and secreted proteins from EPS-treated and untreated myotubes were analyzed using a combination of high-throughput RNA sequencing, microarray, and high-resolution liquid chromatography mass spectrometry. Independent validation of selected putative myokines were measured using ELISA or multiplex assay. Oxidative metabolism was enhanced in human myotubes exposed to EPS protocol 1. A total of 81 differentially regulated proteins and 952 differentially expressed genes (DEGs) were observed in the cells after EPS protocol 1. Gene ontology (GO) analysis indicated that significantly regulated proteins and genes were enriched in biological processes related to glycolytic pathways, positive regulation of fatty acid oxidation, and oxidative phosphorylation, as well as muscle contraction, autophagy/mitophagy, and oxidative stress. Moreover, proteomic identification of secreted proteins revealed extracellular levels of 137 proteins were changed in myotubes subjected to EPS protocol 1. We also found some degree of overlap between the DEGs found in myotubes submitted to EPS protocol 1 and protocol 2. Among these DEGs was a myokine, leukemia