Skeletal muscle myotubes in severe obesity exhibit altered ubiquitin‐proteasome and autophagic/lysosomal proteolytic flux

Bollinger, Lance M.; Powell, Jonathan J.; Houmard, Joseph A.; Witczak, Carol A.; Brault, Jeffrey J.

doi:10.1002/oby.21081

Cited by 32 publications

(29 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Previous studies have shown that LPS activates the ubiquitin–proteasome pathway through TLR4 and induces catabolism both in cultured C2C12 muscle cells [19] and in rat muscle in vivo [20]. In agreement with these findings, increased ubiquitin–proteasome activity has been reported in elderly subjects [21] and in patients with metabolic endotoxemia due to diabetes mellitus [22], obesity [23], liver cirrhosis [24], and chronic kidney disease [25,26]. Damaged or degenerated myofibers are repaired or replaced through myogenesis, the process by which myoblasts fuse to form multinucleated myotubes.…”

Section: Introductionsupporting

confidence: 66%

Lipopolysaccharide inhibits myogenic differentiation of C2C12 myoblasts through the Toll-like receptor 4-nuclear factor-κB signaling pathway and myoblast-derived tumor necrosis factor-α

Ono

Sakamoto

2017

PLoS ONE

View full text Add to dashboard Cite

BackgroundCirculating lipopolysaccharide (LPS) concentrations are often elevated in patients with sepsis or with various endogenous diseases that are associated with metabolic endotoxemia. Involuntary loss of skeletal muscle, termed muscle wasting, is commonly observed in these conditions, suggesting that circulating LPS might play an essential role in its development. Although impairment of muscle regeneration is an important determinant of skeletal muscle wasting, it is unclear whether LPS affects this process and, if so, by what mechanism. Here, we used the C2C12 myoblast cell line to investigate the effects of LPS on myogenesis.MethodsC2C12 myoblasts were grown to 80% confluence and induced to differentiate in the absence or presence of LPS (0.1 or 1 μg/mL); TAK-242 (1 μM), a specific inhibitor of Toll-like receptor 4 (TLR4) signaling; and a tumor necrosis factor (TNF)-α neutralizing antibody (5 μg/mL). Expression of a skeletal muscle differentiation marker (myosin heavy chain II), two essential myogenic regulatory factors (myogenin and MyoD), and a muscle negative regulatory factor (myostatin) was analyzed by western blotting. Nuclear factor-κB (NF-κB) DNA-binding activity was measured using an enzyme-linked immunosorbent assay.ResultsLPS dose-dependently and significantly decreased the formation of multinucleated myotubes and the expression of myosin heavy chain II, myogenin, and MyoD, and increased NF-κB DNA-binding activity and myostatin expression. The inhibitory effect of LPS on myogenic differentiation was reversible, suggesting that it was not caused by nonspecific toxicity. Both TAK-242 and anti-TNF-α reduced the LPS-induced increase in NF-κB DNA-binding activity, downregulation of myogenic regulatory factors, and upregulation of myostatin, thereby partially rescuing the impairment of myogenesis.ConclusionsOur data suggest that LPS inhibits myogenic differentiation via a TLR4–NF-κB-dependent pathway and an autocrine/paracrine TNF-α-induced pathway. These pathways may be involved in the development of muscle wasting caused by sepsis or metabolic endotoxemia.

show abstract

Section: Introductionsupporting

confidence: 66%

Lipopolysaccharide inhibits myogenic differentiation of C2C12 myoblasts through the Toll-like receptor 4-nuclear factor-κB signaling pathway and myoblast-derived tumor necrosis factor-α

Ono

Sakamoto

2017

PLoS ONE

View full text Add to dashboard Cite

show abstract

“…Myotube area was quantified by analysing the amount of MHC covering the culture area using the method of Bollinger et al . (). In addition, cell lysates were assayed for markers of differentiation (MyoD (M‐318); Santa Cruz Biotechology) and myosin heavy chain content (MHC (MF20); Developmental Studies Hybridoma Bank, Iowa City, IA, USA).…”

Section: Methodsmentioning

confidence: 99%

Electrical pulse stimulation induces differential responses in insulin action in myotubes from severely obese individuals

Park

Turner

Zheng

et al. 2018

The Journal of Physiology

Self Cite

View full text Add to dashboard Cite

Key points Exercise/exercise training can enhance insulin sensitivity through adaptations in skeletal muscle, the primary site of insulin‐mediated glucose disposal; however, in humans the range of improvement can vary substantially. The purpose of this study was to determine if obesity influences the magnitude of the exercise response in relation to improving insulin sensitivity in human skeletal muscle. Electrical pulse stimulation (EPS; 24 h) of primary human skeletal muscle myotubes improved insulin action in tissue from both lean and severely obese individuals, but responses to EPS were blunted with obesity. EPS improved insulin signal transduction in myotubes from lean but not severely obese subjects and increased AMP accumulation and AMPK Thr172 phosphorylation, but to a lesser degree in myotubes from the severely obese. These data reveal that myotubes of severely obese individuals enhance insulin action and stimulate exercise‐responsive molecules with contraction, but in a manner and magnitude that differs from lean subjects. Abstract Exercise/muscle contraction can enhance whole‐body insulin sensitivity; however, in humans the range of improvements can vary substantially. In order, to determine if obesity influences the magnitude of the exercise response, this study compared the effects of electrical pulse stimulation (EPS)‐induced contractile activity upon primary myotubes derived from lean and severely obese (BMI ≥ 40 kg/m2) women. Prior to muscle contraction, insulin action was compromised in myotubes from the severely obese as was evident from reduced insulin‐stimulated glycogen synthesis, glucose oxidation, glucose uptake, insulin signal transduction (IRS1, Akt, TBC1D4), and insulin‐stimulated GLUT4 translocation. EPS (24 h) increased AMP, IMP, AMPK Thr172 phosphorylation, PGC1α content, and insulin action in myotubes of both the lean and severely obese subjects. However, despite normalizing indices of insulin action to levels seen in the lean control (non‐EPS) condition, responses to EPS were blunted with obesity. EPS improved insulin signal transduction in myotubes from lean but not severely obese subjects and EPS increased AMP accumulation and AMPK Thr172 phosphorylation, but to a lesser degree in myotubes from the severely obese. These data reveal that myotubes of severely obese individuals enhance insulin action and stimulate exercise‐responsive molecules with contraction, but in a manner and magnitude that differs from lean subjects.

show abstract

“…High-fat feeding was shown to induce autophagic flux in skeletal muscles-marked by an increase in LC3-II, BECLIN1 and ULK1 and a decrease in p62 level-in a mouse model of diet induced obesity and insulin resistance (22). However, under chronic lipid overload, such as in severely obese, hyperinsulnemic human subjects, autophagic flux was blunted in primary skeletal muscle myotubes, which could contribute to the insulin resistant phenotype (79). This increase in high-fat diet-induced autophagy was absent in adiponectin-deficient mice and was restored upon adiponectin reexpression.…”

Section: Regulation Of Autophagic Activity By Lipidsmentioning

confidence: 99%

Lipids, lysosomes, and autophagy

Jaishy

Abel

2016

Journal of Lipid Research

178

139

View full text Add to dashboard Cite

Lipids are essential components of a cell providing energy substrates for cellular processes, signaling intermediates, and building blocks for biological membranes. Lipids are constantly recycled and redistributed within a cell. Lysosomes play an important role in this recycling process that involves the recruitment of lipids to lysosomes via autophagy or endocytosis for their degradation by lysosomal hydrolases. The catabolites produced are redistributed to various cellular compartments to support basic cellular function. Several studies demonstrated a bidirectional relationship between lipids and lysosomes that regulate autophagy. While lysosomal degradation pathways regulate cellular lipid metabolism, lipids also regulate lysosome function and autophagy. In this review, we focus on this bidirectional relationship in the context of dietary lipids and provide an overview of recent evidence of how lipid-overload lipotoxicity, as observed in obesity and metabolic syndrome, impairs lysosomal function and autophagy that may eventually lead to cellular dysfunction or cell death.

show abstract

Skeletal muscle myotubes in severe obesity exhibit altered ubiquitin‐proteasome and autophagic/lysosomal proteolytic flux

Cited by 32 publications

References 40 publications

Lipopolysaccharide inhibits myogenic differentiation of C2C12 myoblasts through the Toll-like receptor 4-nuclear factor-κB signaling pathway and myoblast-derived tumor necrosis factor-α

Lipopolysaccharide inhibits myogenic differentiation of C2C12 myoblasts through the Toll-like receptor 4-nuclear factor-κB signaling pathway and myoblast-derived tumor necrosis factor-α

Electrical pulse stimulation induces differential responses in insulin action in myotubes from severely obese individuals

Lipids, lysosomes, and autophagy

Contact Info

Product

Resources

About