Evidence for autophagy attenuation during post-mortem maturation of hypertrophied muscle in myostatin deficient mice

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Evidence for autophagy attenuation during post-mortem maturation of hypertrophied muscle in myostatin

deficient mice

Rim Nassar, Barbara Vernus, Gilles Fouret, Benedicte Goustard, Francois Casas, Lionel Tintignac, Isabelle Cassar-Malek, Brigitte Picard, Iban Seiliez,

Arnaud Chatonnet, et al.

To cite this version:

Rim Nassar, Barbara Vernus, Gilles Fouret, Benedicte Goustard, Francois Casas, et al.. Evidence for autophagy attenuation during post-mortem maturation of hypertrophied muscle in myostatin deficient mice. 7ème congrès du club français Autophagie CFATG, Nov 2017, Paris, France. 2017. �hal- 02940597�

Dynamique Musculaire et Métabolisme

DMeM

LIT

Laboratoire d’Innovation Thérapeutique

Evidence for autophagy attenuation during post-mortem maturation of hypertrophied muscle in myostatin deficient mice

Rim Nassar^1,2, Barbara Vernus¹, Gilles Fouret¹, Bénédicte Goustard¹, François Casas¹, Lionel Tintignac³, Isabelle Cassar-Malek⁴, Brigitte Picard⁴, Iban Seliez⁵, Arnaud Chatonnet¹, Aline Hamade², Fadia Najjar², Anne Bonnieu¹et Béatrice Chabi¹

1- INRA, UMR 866 Dynamique Musculaire et Métabolisme, Montpellier, France ; 2 - Laboratoire d’Innovation thérapeutique, Université Libanaise, Beyrouth, Liban; 3 - Département de Biomédecine, Université de Bâle, Bâle, Suisse; 4 - INRA, UMR1213 Herbivores, Saint-Genès-Champanelle, France;

5 - INRA, UMR1419 Nutrition, Métabolisme, Aquaculture, Saint Pée sur Nivelle, France.

In conclusion, our data showed that autophagy is preserved during skeletal muscle PM maturation, but to a lower extent in Mstn-deficient mice, suggesting a relationship between myostatin and autophagy. This work will be completed with microscopic analyses of skeletal muscle tissue sections to visualizein situautophagic events.

The conversion of skeletal muscle into meat, i.e. maturation, is a complex process where muscle undergoes different biochemical and physiological changes (Ouali et al, 2006).

In agronomic field, the study of these events is of particular interest, in order to improve the quality of the final product put on the market. If the characterization of the proteolytic mechanisms involved in skeletal muscle maturation is still ongoing, the participation of autophagy in this process is still under debate. The aim of the study was therefore to assess the involvement of autophagy during skeletal muscle maturation and to study the interaction between autophagy and myostatin, a negative regulator of skeletal muscle mass (Mc Pherron et al, 1997), within a 72h postmortem (PM) time frame in mice.

Conclusion

1) Phosphorylation state of proteins involved in autophagic signaling pathway (AMPK, FOXO and ULK) KO

Animal model

Healthy 6 month-old Mstn^+/+(WT) and Mstn^−/−

(Mstn KO; Grobet et al, 2003) male mice (n=72 for each genotype) were used in this study.

Muscle sampling

Mice were sacrificed using cervical dislocation. After decapitation and bleeding, mice were stored at room temperature (22±2°C) during 1h and then at 4°C until the dissection time.

WT KO Mstn

Longissimus dorsi and gastrocnemius muscles were harvested and used for pH and western-blotting analyses respectively.

=> 3) Following PM, autophagy was assessed in skeletal muscle from the two genotypes using signaling pathways and autophagic flux analyses.

n=8 for each time point x genotype, two-way ANOVA, *p<0,05; **** p<0,0001 vs. respective T=0

n=6 for each time point x genotype, two-way ANOVA, **** p<0,0001 vs. KO T=0

Results

Methods and model validation Introduction

2) Autophagy flux measurement

Autophagic flux was monitored using autophagy blockade with four colchicine injections (i.p., 0.1 mg/ml in NaCl 0.9%, every 12h) before sacrifice.

Autophagic flux is calculated as LC3BIIcolchicine– LC3BIINaCl 0.9%

(Jeong-Sun Jun et al, 2010)

Activation of AMPK is greater in WT mice compared to Mstn KO mice Energetic stress or/and Autophagy ?

LC3B I LC3B II

Colchicine administration resulted in LC3BII accumulation (NaCl 0.9% vs. colchicine)

0 4 8 24 0 4 8 24 WT

0 4 8 24 0 4 8 24 KO

NaCl 0.9% Colchicine NaCl 0.9% Colchicine 1) pH evolution in the Longissimus muscle

Postmortemmuscle pH decreased faster in Mstn KO mice compared to WT mice.

Time (h)

0 0.5 1 2 3 4 8 24 48 72

4.6 4.8 5.0 5.2 5.4 5.6 5.8 6.0 6.2

WT

pH

n=8 for each time point x genotype, two-way ANOVA, main effect * p<0,05 WT vs. KO

*

n=6 for each time point x genotype, two-way ANOVA, *p<0,05 vs. respective T=0

Inhibition of Foxo1 is relieved in the late PM interval (8h PM) in both genotypes => Activation of autophagy and Ub proteasome system

Foxo1 Phos (Thr 24)/Total

Time (h)

0 0.5 1 2 3 4 8 24 48

0.00 0.25 0.50 0.75 1.00 1.25 1.50

* Foxo1 p

Foxo1

0 0,5 1 2 3 4 8 24 48 WT

0 0,5 1 2 3 4 8 24 48 KO

KO WT

Foxo1 inhibition (foldover WT T=0) AMPK phos^Thr172/Total

6 ****

0 0.5 1 2 3 4 8 24

0 1 2 3 4 5

*

Time (h) 0 0,5 1 2 3 4 8 24

WT

0 0,5 1 2 3 4 8 24 KO

AMPK p AMPK

KO WT

AMPK activation (foldover WT T=0)

2) Myofibrillar protein degradation

0 0,5 1 2 3 4 8 24 48 WT

0 0,5 1 2 3 4 8 24 48 KO

Myofibrillar proteins (e.g. Troponin T) showed a significant and progressive degradation over the 48h PM period and is more pronounced in gastrocnemius muscle of Mstn KO mice compared to WT mice.

Troponin T

n=8 for each time point x genotype, two-way ANOVA, *p<0,05; ** p<0,01; *** p<0,001 vs. respective T=0

Time (h)

0 0.5 1 2 3 4 8 24 48

0.0 0.2 0.4 0.6 0.8 1.0 1.2

*****

*

KO WT

Proteinexpression (foldover WT T=0)

n=4 for each time point x genotype, two-way ANOVA, main effect ***p<0,001 WT vs. KO

Basal andpostmortemautophagic fluxes are greater in WT versus Mstn KO mice.

Time (h) Autophagic flux

0 4 8 24

0.0 0.5 1.0 1.5 2.0

****

KO WT

LC3B II Flux (foldover WT T=0)

The decrease in ULK1 (Ser757) phosphorylation in Mstn KO mice suggests an early activation (1h PM) of autophagy

Ulk p

Ulk phos (Ser757)/Total

Time (h)

0 0.5 1 2 3 4 8 24 48

0 1 2 3 4 5

****

Ulk

0 0,5 1 2 3 4 8 24 48 WT

0 0,5 1 2 3 4 8 24 48 KO

KO WT

Ulk1 inhibition (foldover WT T=0)

DMEM, UMR 866 2 Place Pierre Viala 34060 MONTPELLIER Cedex

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27-29 Novembre 2017 - Université Paris Descartes