Effects of high EPA and high DHA fish oils on changes in signaling associated with protein metabolism induced by hindlimb suspension in rats

Abstract

The effects of either eicosapentaenoic (EPA)‐ or docosahexaenoic (DHA)‐rich fish oils on hindlimb suspension (HS)‐induced muscle disuse atrophy were compared. Daily oral supplementations (0.3 mL/100 g b.w.) with mineral oil (MO) or high EPA or high DHA fish oils were performed in adult rats. After 2 weeks, the animals were subjected to HS for further 2 weeks. The treatments were maintained alongside HS. At the end of 4 weeks, we evaluated: body weight gain, muscle mass and fat depots, composition of fatty acids, cross‐sectional areas (CSA) of the soleus muscle and soleus muscle fibers, activities of cathepsin L and 26S proteasome, and content of carbonylated proteins in the soleus muscle. Signaling pathway activities associated with protein synthesis (Akt, p70S6K, S6, 4EBP1, and GSK3‐beta) and protein degradation (atrogin‐1/MAFbx, and MuRF1) were evaluated. HS decreased muscle mass, CSA of soleus muscle and soleus muscle fibers, and altered signaling associated with protein synthesis (decreased) and protein degradation (increased). The treatment with either fish oil decreased the ratio of omega‐6/omega‐3 fatty acids and changed protein synthesis‐associated signaling. EPA‐rich fish oil attenuated the changes induced by HS on 26S proteasome activity, CSA of soleus muscle fibers, and levels of p‐Akt, total p70S6K, p‐p70S6K/total p70S6K, p‐4EBP1, p‐GSK3‐beta, p‐ERK2, and total ERK 1/2 proteins. DHA‐rich fish oil attenuated the changes induced by HS on p‐4EBP1 and total ERK1 levels. The effects of EPA‐rich fish oil on protein synthesis signaling were more pronounced. Both EPA‐ and DHA‐rich fish oils did not impact skeletal muscle mass loss induced by non‐inflammatory HS.

A Comparative Histological and Immunohistochemical Study of the Effect of Oxandrolone and Whey Protein on Disuse Induced Muscle Atrophy in old aged male rats

“…Hind limb suspension, the most commonly used animal model to experimentally induce muscle atrophy in rats [12] was used in the present study. Rats were put in small cages after unloading to limit their mobility.…”

“…Hind Limb Suspension (HLS) [12] was done to induce atrophy in right gastrocnemius muscle and rats were sacrificed after 2 weeks to confirm atrophy [13] .…”

“…Each animal was suspended in a separate cage to ensure the competence of the procedure and prevent rats from cutting off the tails of each other from the cover of the cage. After reloading rats were put in small cages to limit their mobility [12] .…”

Sarcomere Structure: The Importance of Desmin Protein in Muscle Atrophy

“…In an individual special cage, the animal is maintained with the tail taped to a harness and pulley on the top of the cage. In this position, the animal moves freely using the forelimbs only, while the hind limbs cannot touch the bottom of the cage, removing the mechanical loading and causing disuse atrophy of the hindlimb muscles (Marzuca-Nassr et al, 2016;Marzuca-Nassr et al, 2017b;Marzuca-Nassr et al, 2017a).…”

Pretreatment with fish oil attenuates heart ischaemia consequences in rats

“…The results were expressed as a percentage of the total FFAs. The same procedure was used in our previous studies Marzuca-Nassr et al 2016).…”