Sarcopenia is attenuated by TRB3 knockout in aging mice via the alleviation of atrophy and fibrosis of skeletal muscles

Abstract

Background Sarcopenia causes several adverse events in elderly people. Muscle fibre atrophy and interstitial fibrosis are the main histopathological changes in sarcopenia and account for decreased muscle function. Tribbles homologue 3 (TRB3) was previously reported to exhibit age‐related expression and play a vital role in cell proliferation, differentiation, and fibrosis. We aimed to investigate how TRB3 affects sarcopenia. Methods Wild‐type and TRB3 knockout C57/BL6J mice were randomly divided into young and old groups. Exercise capacity was evaluated, and single‐muscle function was detected by electrophysiological techniques, after which the mice were sacrificed to collect their gastrocnemius muscles for assessment of atrophy and fibrosis by histopathological and molecular biological methods. TRB3 expression, autophagy level, and MAPK signalling pathway activity were evaluated through western blotting. The interaction of TRB3 with P62 and the association between TRB3 and the MAPK signalling pathway were detected by co‐immunoprecipitation. Results In aged mice, exercise capacity and cross‐sectional area of skeletal muscle fibres were decreased significantly, whereas TRB3, atrophy‐related markers atrogin 1 and MuRF 1, and interstitial fibrosis, including collagen volume fraction, contents of collagens I and III, and ratio of collagens I to III, were increased significantly ( P < 0.05 for all). Following TRB3 knockout, the cross‐sectional area of muscle fibres, mainly fast fibres, was elevated ( P < 0.05 for both), the atrogin 1 expression was decreased ( P = 0.0163), and the corresponding tetanic force of fast muscles was increased ( P = 0.0398). Conversely, interstitial fibrosis was substantially decreased and exercise capacity was significantly increased in the knockout mice. In terms of the underlying mechanisms, the autophagy receptor p62 was markedly increased and the MAPK signalling pathway was activated in aged skeletal muscles, which might be attributed to the interaction of TRB3 with p62 and MAPKKs, including MEK1/MEK2, MEK3/MEK6, and MEK4/MKK4. Notably, TRB3 knockout reduced the accumulation of p62 and LC3 ( P < 0.05 for both), decreased the phosphorylation of JNK ( P = 0.0015), and increased p38 phosphorylation ( P = 0.0021). Conclusions TRB3 knockout in mice attenuated muscle fibre atrophy and reduced skeletal muscle fibrosis by increasing autophagy and inhibiting the MAPK signalling pathway. Correspondingly, in aged knockout mice, exercise capacity was improved. Interfering with TRB3 expression in aged skeletal muscles may serve as a target for the prevention and treatment of age‐related sarcopenia.

All-trans retinoic acid induces GADD34 gene expression via transcriptional regulation by Six1-TLE3 and post-transcriptional regulation by p38-TTP in skeletal muscle

“…Since the plasma levels of vitamin A (retinol or ATRA) increase with aging (Gueguen et al , 2005), the increase of ATRA that occurs with aging may accelerate cellular senescence in the muscle via the induction of GADD34, resulting in muscle atrophy in elderly patients. It has been reported that aged mice exhibit an increase of slow muscle fibers but a decrease of fast muscle fibers (Shang et al , 2020). These results are in line with the effects of GADD34 on myotubes that were observed in our study.…”

Animal models of sarcopenia

“…It has been demonstrated that TRB3 caused muscle fiber atrophy and a decrease in muscle function by negatively modulating protein turnover in the condition of food deprivation (Choi et al, 2017(Choi et al, , 2019 and could inhibit the myogenic differentiation of C2C12 (mouse myoblast) cells (Kato & Du, 2007). Shang et al acquired TRB3 knockout mice and found that sarcopenia was attenuated in these mice compared with aged controls via the alleviation of atrophy and fibrosis of skeletal muscles (Shang et al, 2020 As noted below, in C. elegans (Depuydt et al, 2013;Duhon & Johnson, 1995;Herndon et al, 2002) and in Drosophila (Demontis & Perrimon, 2010;Owusu-Ansah, Song, & Perrimon, 2013), genetic reduction in the insulin/IGF1 signaling pathway, which causes increased nuclear translocation of DAF-16 (FOXO in mammals), results in lifespan extension and reduced sarcopenia in these organisms. Although similar experiments have not yet been conducted on rodent muscle, a mouse in which FOXO 1, 3, and 4 genes were knocked out in neurons resulted in age-associated axonal tract degeneration and motor dysfunction (Hwang et al, 2018).…”

“…It has been demonstrated that TRB3 caused muscle fiber atrophy and a decrease in muscle function by negatively modulating protein turnover in the condition of food deprivation (Choi et al, 2017, 2019) and could inhibit the myogenic differentiation of C2C12 (mouse myoblast) cells (Kato & Du, 2007). Shang et al acquired TRB3 knockout mice and found that sarcopenia was attenuated in these mice compared with aged controls via the alleviation of atrophy and fibrosis of skeletal muscles (Shang et al, 2020). The TRB3 knockout mice had reduced atrophy and a greater exercise capacity compared with the wild‐type mice at the same age.…”

Prdx6 Plays a Main Role in the Crosstalk between Aging and Metabolic Sarcopenia

“…Slides were analyzed under a light microscope (Eclipse E600, Nikon, Tokyo, Japan) and images captured (magnification 20X) by a digital camera (DXM1200F, Nikon) connected to the ACT-1 software (Nikon). Then, the cross-sectional area (CSA) was measured using the ImageJ software 2018 (NIH, Bethesda, Maryland, USA), as reported [21].…”