Skeletal muscle atrophy/wasting is associated with impaired protein metabolism in diverse physiological and pathophysiological conditions. Elevated levels of reactive oxygen species (ROS), disturbed redox status, and weakened antioxidant defense system are the major contributing factors toward atrophy. Regulation of protein metabolism by controlling ROS levels and its associated catabolic pathways may help in treating atrophy and related clinical conditions. Although cinnamaldehyde (CNA) enjoys the established status of antioxidant and its role in ROS management is reported, impact of CNA on skeletal muscle atrophy and related pathways is still unexplored. In the current study, the impact of CNA on C2C12 myotubes and the possible protection of cultured cells from H2O2‐induced atrophy is examined. Myotubes were treated with H2O2 in the presence and absence of CNA and the changes in the antioxidative, proteolytic systems, and mitochondrial functions were scored. Morphological analysis showed significant protective effects of CNA on length, diameter, and nuclei fusion index of myotubes. The evaluation of biochemical markers of atrophy; creatine kinase, lactate dehydrogenase, succinate dehydrogenase
along with the study of muscle‐specific structural protein (i.e., myosin heavy chainfast [MHCf] type) showed significant protection of proteins by CNA. CNA pretreatment not only checked the activation of proteolytic systems (ubiquitinproteasome E3‐ligases [MuRF1/Atrogin1]), autophagy [Beclin1/LC3B], cathepsin L, calpain, caspase), but also prevented any alteration in the activities of antioxidative defense enzymes (catalase, glutathione‐S‐transferase, glutathione‐peroxidase, superoxide
dismutase, glutathione reductase). The results suggest that CNA protects
myotubes from H2O2‐induced atrophy by inhibiting/resisting the amendments in proteolytic systems and maintains cellular redox‐balance.
J Cell Physiol. 2019;234:6194–6208. DOI: 10.1002/jcp.27348
Elevated levels of inflammatory molecules are key players in muscle wasting/atrophy leading to human morbidity. TNFα is a well-known pro-inflammatory cytokine implicated in the pathogenesis of muscle wasting under diverse clinical settings. S-allyl cysteine (SAC), an active component of garlic (Allium sativum), has established anti-oxidant and anti-inflammatory effects in various cell types. However, the impact of SAC on skeletal musclepathology remains unexplored. Owing to the known anti-inflammatory properties of SAC, we investigated whether pre-treatment with SAC has a protective role in TNFα-induced atrophy in cultured myotubes.
Methods and results
C2C12 myotubes were treated with TNFα (100 ng/ml) in the presence or absence of SAC (0.01 mM). TNFα treatment induced atrophy in myotubes by up-regulating various proteolyticsystems i.e. cathepsin L, calpain, ubiquitin-proteasome E3-ligases (MuRF1/atrogin1), caspase 3 and autophagy (Beclin1/LC3B). TNFα also induced the activation of NFκB by stimulating the degradation of IκBα (inhibitor of NFκB), in myotubes. The alterations in proteolytic systems likely contribute to the degradation of muscle-specific proteins and reduce the myotube length, diameter and fusion index. The SAC supplementation significantly impedes TNFα-induced protein loss and protects myotube morphology by suppressing protein catabolic systems and endogenous level of inflammatory molecules namely TNFα, IL-6, IL-1β, TNF-like weak inducer of apoptosis (TWEAK), fibroblast growth factor-inducible 14 (Fn14) and Nox.
Conclusion and general significance
Our findings reveal anti-atrophic role for SAC, as it prevents alterations in protein metabolism and protects myotubes by regulating the level of inflammatory molecules and multiple proteolytic systems responsible for muscle atrophy.
Biochim Biophys Acta. 2018 Apr;1862(4):895-906.
Calpain, a proteolytic enzyme plays critical role in the skeletal muscle physiology by maintaining the protein metabolism. Up-regulation in the activity of such enzyme under diverse clinical settings (i.e. diabetes, cancer, AIDS, chronic heart failure, immobilization, aging etc) leads to loss in muscle proteins and causes atrophy/cachexia/sarcopenia. Beyond a reduced survival rate, atrophy is also linked to poor functional status and quality of life. Thus, easy detection of calpain at very early stage is highly desired under such settings so that specific therapy or antagonist could be given in time. Multiple methods are available (zymography, qPCR and immunoblotting) and among these zymography is the only approach which actually detect calpain activity. In the present manuscript, we have improvised two zymography protocols which are able to detect calpain in all muscle cells and tissues. Result shows that modified protocols can detect calpain activity even at low proteins concentration (<10 μg) in muscle cells (C2C12 myoblasts, proliferating state; myotubes, differentiating state) and tissues (cardiac and skeletal) in a single gel in comparatively short time span. Overall, purpose of the present study is to provide relatively simple and well described experimental protocol which can be used for muscle-specific calpain study.
An increasing array of anti-diabetic drugs are available today, yet Type-2 diabetes mellitus (T2DM) − remains a life threatening disease, causing high mortality and morbidity in developing and developed countries. As of now, no effective therapy is available for the complete eradication/cure of diabetes and its associated complications. Therefore, it is time to re-think and revisit molecular pathways and targets of each existing drug in order to identify multiple targets from different signaling pathways that may be manipulated simultaneously to treat or manage T2DM effectively. Bearing this goal in mind, the article reviews the mechanisms of action of available anti-diabetic drugs with in-depth mechanistic analysis of each therapy. The conventional and herbal strategies are analysed and compared for their benefits and the associated possible side effects. This critical information is necessary not only for the development of better, novel and potent anti-diabetic therapy in future but also for best possible combinational therapies and strategies with the available drugs.
Pharmacological Research, 2016, http://dx.doi.org/10.1016/j.phrs.2016.09.029
a b s t r a c t
Over the last two decades, new insights into the etiology of skeletal muscle wasting/atrophy under diverse clinical settings including denervation, AIDS, cancer, diabetes, and chronic heart failure have been reported in the literature. However, the treatment of skeletal muscle wasting remains an unresolved challenge to this day. About nineteen potential drugs that can regulate loss of muscle mass have been reported in the literature. This paper reviews the mechanisms of action of all these drugs by broadly classifying them into six different categories. Mechanistic data of these drugs illustrate that they regulate skeletal muscle loss either by down-regulating myostatin, cyclooxygenase2, pro-inflammatory cytokines mediated catabolic wasting or by up-regulating cyclic AMP, peroxisome proliferator-activated receptor gamma coactivator-1, growth hormone/insulin-like growth factor1, phosphatidylinositide 3-kinases/protein kinase B(Akt) mediated anabolic pathways. So far, five major proteolytic systems that regulate loss of muscle mass have been identified, but the majority of these drugs control only two or three proteolytic systems. In addition to their beneficial effect on restoring the muscle loss, many of these drugs show some level of toxicity and unwanted side effects such as dizziness, hypertension, and constipation. Therefore, further research is needed to understand and develop treatment strategies for muscle wasting. For successful management of skeletal muscle wasting either therapeutic agent which regulates all five known proteolytic systems or new molecular targets/proteolytic systems must be identified.
Pharmacological Research 99 (2015) 86–100