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TNF-α- and tumor-induced skeletal muscle atrophy involves sphingolipid metabolism.

De Larichaudy J, Zufferli A, Serra F, Isidori AM, Naro F, Dessalle K, Desgeorges M, Piraud M, Cheillan D, Vidal H, Lefai E, Némoz G - Skelet Muscle (2012)

Bottom Line: In the presence of TNF-α, ceramide-synthesis inhibitors significantly increased protein synthesis and decreased proteolysis.Furthermore, these inhibitors increased the expression and/or phosphorylation levels of key factors regulating protein metabolism, including phospholipase D, an activator of mammalian target of rapamycin (mTOR), and the mTOR substrates S6K1 and Akt.Treatment of the animals with myriocin reduced the expression of the atrogenes Foxo3 and Atrogin-1, and partially protected muscle tissue from atrophy.

View Article: PubMed Central - HTML - PubMed

Affiliation: Lyon University, INSERM U1060, CarMeN Laboratory, University Lyon-1, Institut National de la Recherche Agronomique UMR1235, INSA-Lyon, F-69600 Oullins, France. georges.nemoz@insa-lyon.fr.

ABSTRACT

Background: Muscle atrophy associated with various pathophysiological conditions represents a major health problem, because of its contribution to the deterioration of patient status and its effect on mortality. Although the involvement of pro-inflammatory cytokines in this process is well recognized, the role of sphingolipid metabolism alterations induced by the cytokines has received little attention.

Results: We addressed this question both in vitro using differentiated myotubes treated with TNF-α, and in vivo in a murine model of tumor-induced cachexia. Myotube atrophy induced by TNF-α was accompanied by a substantial increase in cell ceramide levels, and could be mimicked by the addition of exogenous ceramides. It could be prevented by the addition of ceramide-synthesis inhibitors that targeted either the de novo pathway (myriocin), or the sphingomyelinases (GW4869 and 3-O-methylsphingomyelin). In the presence of TNF-α, ceramide-synthesis inhibitors significantly increased protein synthesis and decreased proteolysis. In parallel, they lowered the expression of both the Atrogin-1 and LC3b genes, involved in muscle protein degradation by proteasome and in autophagic proteolysis, respectively, and increased the proportion of inactive, phosphorylated Foxo3 transcription factor. Furthermore, these inhibitors increased the expression and/or phosphorylation levels of key factors regulating protein metabolism, including phospholipase D, an activator of mammalian target of rapamycin (mTOR), and the mTOR substrates S6K1 and Akt. In vivo, C26 carcinoma implantation induced a substantial increase in muscle ceramide, together with drastic muscle atrophy. Treatment of the animals with myriocin reduced the expression of the atrogenes Foxo3 and Atrogin-1, and partially protected muscle tissue from atrophy.

Conclusions: Ceramide accumulation induced by TNF-α or tumor development participates in the mechanism of muscle-cell atrophy, and sphingolipid metabolism is a logical target for pharmacological or nutritional interventions aiming at preserving muscle mass in pathological situations.

No MeSH data available.


Related in: MedlinePlus

Inhibitors of ceramide synthesis modulate tumor necrosis factor (TNF)-α effects on myotube sphingolipid content. (A) Total ceramide levels were determined in myotubes treated for 3 days with TNF-α, without or with 100 nmol/l myriocin, 10 μmol/l GW4869, or 1 μmol/l OMS. Results are expressed as a percentage of control value, and are the mean ± SE of 3 to 5 determinations. ++Different from control: P = 0.02; *different from TNF-α alone: P = 0.05, **:P = 0.02, ***P < 0.001. Mean ± SE control value is 14.7 ± 3.4 pmol ceramide/μg proteins. (B) Total sphingomyelin levels were determined in myotubes treated for 3 days with TNF-α, without or with 100 nmol/l myriocin, 10 μmol/l GW4869, or 1 μmol/l OMS. Results are expressed as a percentage of control value, and are the mean ± SE of 3 to 5 determinations. ++Different from control: P = 0.002, +++P < 0.001; *different from TNF-α alone: P = 0.05, **P = 0.02. Mean ± SE control value is 118.8 ± 17.2 pmol sphingomyelin/μg proteins.
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Figure 3: Inhibitors of ceramide synthesis modulate tumor necrosis factor (TNF)-α effects on myotube sphingolipid content. (A) Total ceramide levels were determined in myotubes treated for 3 days with TNF-α, without or with 100 nmol/l myriocin, 10 μmol/l GW4869, or 1 μmol/l OMS. Results are expressed as a percentage of control value, and are the mean ± SE of 3 to 5 determinations. ++Different from control: P = 0.02; *different from TNF-α alone: P = 0.05, **:P = 0.02, ***P < 0.001. Mean ± SE control value is 14.7 ± 3.4 pmol ceramide/μg proteins. (B) Total sphingomyelin levels were determined in myotubes treated for 3 days with TNF-α, without or with 100 nmol/l myriocin, 10 μmol/l GW4869, or 1 μmol/l OMS. Results are expressed as a percentage of control value, and are the mean ± SE of 3 to 5 determinations. ++Different from control: P = 0.002, +++P < 0.001; *different from TNF-α alone: P = 0.05, **P = 0.02. Mean ± SE control value is 118.8 ± 17.2 pmol sphingomyelin/μg proteins.

Mentions: The effects of ceramide-synthesis inhibitors on the changes in cellular levels of sphingolipids induced by TNF-α were assessed in L6 myotubes. Both the de novo synthesis inhibitor myriocin and the sphingomyelinase inhibitors GW4869 and OMS significantly inhibited the TNF-α-induced increase in ceramide levels (Figure 3a), confirming that the drugs were active at the concentrations used, and suggesting that ceramide accumulation results from the activation of both pathways under the action of TNF-α. As expected, treatment with GW4869 and OMS alleviated the TNF-α-induced loss of sphingomyelin (Figure 3b). By contrast, myriocin by itself decreased sphingomyelin levels and amplified the sphingomyelin-lowering effect of TNF-α, in agreement with its reported ability to induce a general depletion of sphingolipids, including sphingomyelin [19].


TNF-α- and tumor-induced skeletal muscle atrophy involves sphingolipid metabolism.

De Larichaudy J, Zufferli A, Serra F, Isidori AM, Naro F, Dessalle K, Desgeorges M, Piraud M, Cheillan D, Vidal H, Lefai E, Némoz G - Skelet Muscle (2012)

Inhibitors of ceramide synthesis modulate tumor necrosis factor (TNF)-α effects on myotube sphingolipid content. (A) Total ceramide levels were determined in myotubes treated for 3 days with TNF-α, without or with 100 nmol/l myriocin, 10 μmol/l GW4869, or 1 μmol/l OMS. Results are expressed as a percentage of control value, and are the mean ± SE of 3 to 5 determinations. ++Different from control: P = 0.02; *different from TNF-α alone: P = 0.05, **:P = 0.02, ***P < 0.001. Mean ± SE control value is 14.7 ± 3.4 pmol ceramide/μg proteins. (B) Total sphingomyelin levels were determined in myotubes treated for 3 days with TNF-α, without or with 100 nmol/l myriocin, 10 μmol/l GW4869, or 1 μmol/l OMS. Results are expressed as a percentage of control value, and are the mean ± SE of 3 to 5 determinations. ++Different from control: P = 0.002, +++P < 0.001; *different from TNF-α alone: P = 0.05, **P = 0.02. Mean ± SE control value is 118.8 ± 17.2 pmol sphingomyelin/μg proteins.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 3: Inhibitors of ceramide synthesis modulate tumor necrosis factor (TNF)-α effects on myotube sphingolipid content. (A) Total ceramide levels were determined in myotubes treated for 3 days with TNF-α, without or with 100 nmol/l myriocin, 10 μmol/l GW4869, or 1 μmol/l OMS. Results are expressed as a percentage of control value, and are the mean ± SE of 3 to 5 determinations. ++Different from control: P = 0.02; *different from TNF-α alone: P = 0.05, **:P = 0.02, ***P < 0.001. Mean ± SE control value is 14.7 ± 3.4 pmol ceramide/μg proteins. (B) Total sphingomyelin levels were determined in myotubes treated for 3 days with TNF-α, without or with 100 nmol/l myriocin, 10 μmol/l GW4869, or 1 μmol/l OMS. Results are expressed as a percentage of control value, and are the mean ± SE of 3 to 5 determinations. ++Different from control: P = 0.002, +++P < 0.001; *different from TNF-α alone: P = 0.05, **P = 0.02. Mean ± SE control value is 118.8 ± 17.2 pmol sphingomyelin/μg proteins.
Mentions: The effects of ceramide-synthesis inhibitors on the changes in cellular levels of sphingolipids induced by TNF-α were assessed in L6 myotubes. Both the de novo synthesis inhibitor myriocin and the sphingomyelinase inhibitors GW4869 and OMS significantly inhibited the TNF-α-induced increase in ceramide levels (Figure 3a), confirming that the drugs were active at the concentrations used, and suggesting that ceramide accumulation results from the activation of both pathways under the action of TNF-α. As expected, treatment with GW4869 and OMS alleviated the TNF-α-induced loss of sphingomyelin (Figure 3b). By contrast, myriocin by itself decreased sphingomyelin levels and amplified the sphingomyelin-lowering effect of TNF-α, in agreement with its reported ability to induce a general depletion of sphingolipids, including sphingomyelin [19].

Bottom Line: In the presence of TNF-α, ceramide-synthesis inhibitors significantly increased protein synthesis and decreased proteolysis.Furthermore, these inhibitors increased the expression and/or phosphorylation levels of key factors regulating protein metabolism, including phospholipase D, an activator of mammalian target of rapamycin (mTOR), and the mTOR substrates S6K1 and Akt.Treatment of the animals with myriocin reduced the expression of the atrogenes Foxo3 and Atrogin-1, and partially protected muscle tissue from atrophy.

View Article: PubMed Central - HTML - PubMed

Affiliation: Lyon University, INSERM U1060, CarMeN Laboratory, University Lyon-1, Institut National de la Recherche Agronomique UMR1235, INSA-Lyon, F-69600 Oullins, France. georges.nemoz@insa-lyon.fr.

ABSTRACT

Background: Muscle atrophy associated with various pathophysiological conditions represents a major health problem, because of its contribution to the deterioration of patient status and its effect on mortality. Although the involvement of pro-inflammatory cytokines in this process is well recognized, the role of sphingolipid metabolism alterations induced by the cytokines has received little attention.

Results: We addressed this question both in vitro using differentiated myotubes treated with TNF-α, and in vivo in a murine model of tumor-induced cachexia. Myotube atrophy induced by TNF-α was accompanied by a substantial increase in cell ceramide levels, and could be mimicked by the addition of exogenous ceramides. It could be prevented by the addition of ceramide-synthesis inhibitors that targeted either the de novo pathway (myriocin), or the sphingomyelinases (GW4869 and 3-O-methylsphingomyelin). In the presence of TNF-α, ceramide-synthesis inhibitors significantly increased protein synthesis and decreased proteolysis. In parallel, they lowered the expression of both the Atrogin-1 and LC3b genes, involved in muscle protein degradation by proteasome and in autophagic proteolysis, respectively, and increased the proportion of inactive, phosphorylated Foxo3 transcription factor. Furthermore, these inhibitors increased the expression and/or phosphorylation levels of key factors regulating protein metabolism, including phospholipase D, an activator of mammalian target of rapamycin (mTOR), and the mTOR substrates S6K1 and Akt. In vivo, C26 carcinoma implantation induced a substantial increase in muscle ceramide, together with drastic muscle atrophy. Treatment of the animals with myriocin reduced the expression of the atrogenes Foxo3 and Atrogin-1, and partially protected muscle tissue from atrophy.

Conclusions: Ceramide accumulation induced by TNF-α or tumor development participates in the mechanism of muscle-cell atrophy, and sphingolipid metabolism is a logical target for pharmacological or nutritional interventions aiming at preserving muscle mass in pathological situations.

No MeSH data available.


Related in: MedlinePlus