Endogenous conversion of n-6 to n-3 polyunsaturated fatty acids facilitates the repair of cardiotoxin-induced skeletal muscle injury in fat-1 mice

Abstract

In this study, we investigated the beneficial effects of high endogenous levels of n-3 polyunsaturated fatty acids (PUFAs) on skeletal muscle repair and regeneration using a mouse cardiotoxin (CTX, 20 μM/200 μL) -induced gastrocnemius muscle injury model. Transgenic fat-1 mice expressing the Caenorhabditis elegans fat-1 gene, encoding n-3 fatty acid desaturase, showed higher n-3 PUFA levels and lower n-6/n-3 PUFA ratios in gastrocnemius muscle tissues. Hematoxylin and eosin and Masson’s trichrome staining of gastrocnemius sections revealed increased muscle fiber size and reduced fibrosis in fat-1 mice on days 7 and 14 after CTX injections. Gastrocnemius muscle tissues from fat-1 mice showed reduced inflammatory responses and increased muscle fiber regeneration reflecting enhanced activation of satellite cells on day 3 after cardiotoxin injections. Gastrocnemius muscle tissues from cardiotoxin-treated fat-1 mice showed reduced levels of pro-apoptotic proteins (Caspase 3 and Bax) and increased levels of anti-apoptotic proteins (Bcl-2 and Survivin). Moreover, eicosapentaenoic acid (EPA) reduced the incidence of apoptosis among cardiotoxin-treated C2C12 mouse myoblasts. These findings demonstrate that higher endogenous n-3 PUFA levels in fat-1 mice enhances skeletal muscle repair and regeneration following cardiotoxin-induced injury.

The Role of Omega-3 Polyunsaturated Fatty Acids and Their Lipid Mediators on Skeletal Muscle Regeneration: A Narrative Review

“…In parallel, this treatment increased M1-to-M2 macrophage phenotype transition [ 86 , 87 ], decreased inflammation via changes in serum levels of proinflammatory (IFN-γ) and anti-inflammatory (IL-10) cytokines [ 86 ], and diminished muscle oxidative stress through downregulation of inducible nitric oxide synthase protein [ 86 ] and 4-HNE-protein adducts [ 84 ]. Not surprisingly, similar findings have also been observed in other rodent models of muscle damage such as high-fat diet [ 88 ] and cardiotoxin-induced gastrocnemius muscle injury [ 89 ]. Nevertheless, to our knowledge, no study has identified whether the positive changes in myogenesis observed after n-3 PUFA administration are mediated by their derived metabolites, the oxylipins and endocannabinoids; however, recent evidence has shown a promising role of the oxylipin derived from n-3 PUFA, the RVs, as a potential molecule to enhance muscle regeneration.…”

DDAH1 Protects against Cardiotoxin-Induced Muscle Injury and Regeneration

“…It has been reported that muscle regeneration can be delayed by excess superoxide generation [ 28 ] and that the severity of muscle injury is associated with cell apoptosis [ 29 ]. To determine the effect of DDAH1 on CTX-induced oxidative stress and apoptosis, cryosections from control and CTX-treated mice were stained with DHE and TUNEL, respectively.…”

Skeletal Muscle Regeneration in Cardiotoxin-Induced Muscle Injury Models

“…It is reported that the lack of interleukin (IL-1) [ 77 ], CC chemokine receptor 2 (CCR2) [ 81 ], toll-like receptor 2 (TLR2) [ 79 ], and heat shock protein (Hsp70) [ 78 ] and the inactivation of IL-6/signal transducer and activator of transcription 3 (STAT3) signaling [ 82 ] and complement C3a-C3a receptor (C3aR)/CCL5 signaling [ 86 ] lead to reduced/delayed monocyte/macrophage infiltration, which then reduces the clearance of necrotic fiber debris and impairs myoblast proliferation, attenuating/delaying muscle regeneration. The endogenous conversion of n-6 to n-3 polyunsaturated fatty acids [ 76 ] and pretreatment with thymol [ 75 ] reduce macrophage infiltration and cell apoptosis, leading to increased SC migration and proliferation and improved muscle regeneration. Loss of Kruppel-like factor 2 (KLF2) [ 65 ], and the lack of plasminogen activator inhibitor (PAI-1) [ 2 , 23 ] and signal transducer and activator of transcription 1 (STAT1) in bone marrow-derived cells [ 66 ] and the inhibition of activin A [ 69 ] stimulate monocyte/macrophage recruitment, accelerate damaged muscle degradation, and promote myoblast proliferation, thereby improving muscle regeneration.…”