Z-ajoene from Crushed Garlic Alleviates Cancer-Induced Skeletal Muscle Atrophy

Skeletal muscle atrophy after sciatic nerve damage: Mechanistic insights

Sciatic nerve injury leads to molecular events that cause muscular dysfunction advancement in atrophic conditions. Nerve damage renders muscles permanently relaxed which elevates intracellular resting Ca2+ levels. Increased Ca2+ levels are associated with several cellular signaling pathways including AMPK, cGMP, PLC-β, CERB, and calcineurin. Also, multiple enzymes involved in the tricarboxylic acid cycle and oxidative phosphorylation are activated by Ca2+ influx into mitochondria during muscle contraction, to meet increased ATP demand. Nerve damage induces mitophagy and skeletal muscle atrophy through increased sensitivity to Ca2+-induced opening of the permeability transition pore (PTP) in mitochondria attributed to Ca2+, ROS, and AMPK overload in muscle. Activated AMPK interacts negatively with Akt/mTOR is a highly prevalent and well-described central pathway for anabolic processes. Over the decade several reports indicate abnormal behavior of signaling machinery involved in denervation-induced muscle loss but end up with some controversial outcomes. Therefore, understanding how the synthesis and inhibitory stimuli interact with cellular signaling to control muscle mass and morphology may lead to new pharmacological insights toward understanding the underlying mechanism of muscle loss after sciatic nerve damage. Hence, the present review summarizes the existing literature on denervation-induced muscle atrophy to evaluate the regulation and expression of differential regulators during sciatic damage.

Garlic-derived compounds: Epigenetic modulators and their antitumor effects

Cancer is a highly heterogeneous disease that poses a serious threat to human health worldwide. Despite significant advances in the diagnosis and treatment of cancer, the prognosis and survival rate of cancer remain poor due to late diagnosis, drug resistance, and adverse reactions. Therefore, it is very necessary to study the development mechanism of cancer and formulate effective therapeutic interventions. As widely available bioactive substances, natural products have shown obvious anticancer potential, especially by targeting abnormal epigenetic changes. The main active part of garlic is organic sulfur compounds, of which diallyl trisulfide (DATS) content is the highest, accounting for more than 40% of the total composition. The garlic-derived compounds have been recognized as an antioxidant for cancer prevention and treatment. However, the molecular mechanism of the antitumor effect of garlic-derived compounds remains unclear. Recent studies have identified garlic-derived compound DATS that plays critical roles in enhancing CpG demethylation or promoting histone acetylation as an epigenetic inhibitor. Here, we review the therapeutic progress of garlic-derived compounds against cancer through epigenetic pathways.

Aged black garlic (Allium sativum L.) and aged black elephant garlic (Allium ampeloprasum L.) alleviate obesity and attenuate obesity-induced muscle atrophy in diet-induced obese C57BL/6 mice

Garlic (Allium sativum L.) is a primary dietary component worldwide because of its health benefits and use as a traditional medicine. Elephant garlic (Allium ampeloprasum L.), a related species in the same genus, is less intense and sweeter than A. sativum. The object of this study was to investigate the alleviative effects of aged black garlic (ABG) and aged black elephant garlic (ABEG) on obesity and muscle atrophy induced by obesity in high fat diet-induced obese mice. We demonstrated that ABG and ABEG alleviated obesity and muscle atrophy and enhanced myogenic differentiation and myotube hypertrophy, and this effect was mediated by the upregulation of Akt/mTOR/p70^S6K signaling. Furthermore, a candidate bioactive compound of ABG and ABEG was suggested in this study through analysis using gas chromatography-mass spectroscopy and ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectroscopy. In conclusion, ABG and ABEG may alleviate obesity and treat obesity-induced muscle atrophy.

Redox Signaling in Chronic Kidney Disease-Associated Cachexia

Redox signaling alterations contribute to chronic kidney disease (CKD)-associated cachexia. This review aims to summarize studies about redox pathophysiology in CKD-associated cachexia and muscle wasting and to discuss potential therapeutic approaches based on antioxidant and anti-inflammatory molecules to restore redox homeostasis. Enzymatic and non-enzymatic systems of antioxidant molecules have been studied in experimental models of kidney diseases and patients with CKD. Oxidative stress is increased by several factors present in CKD, including uremic toxins, inflammation, and metabolic and hormone alterations, leading to muscle wasting. Rehabilitative nutritional and physical exercises have shown beneficial effects for CKD-associated cachexia. Anti-inflammatory molecules have also been tested in experimental models of CKD. The importance of oxidative stress has been shown by experimental studies in which antioxidant therapies ameliorated CKD and its associated complications in the 5/6 nephrectomy model. Treatment of CKD-associated cachexia is a challenge and further studies are necessary to investigate potential therapies involving antioxidant therapy.

Phytochemicals: A potential therapeutic intervention for the prevention and treatment of cachexia

Cachexia, a multifactorial and often irreversible wasting syndrome, is often associated with the final phase of several chronic disorders. Although cachexia is characterized by skeletal muscle wasting and adipose tissue loss, it is a syndrome affecting different organs, which ultimately results in systemic complications and impaired quality of life. The pathogenesis and underlying molecular mechanisms of cachexia are not fully understood, and currently there are no effective standard treatments or approved drug therapies to completely reverse cachexia. Moreover, adequate nutritional interventions alone cannot significantly improve cachexia. Other approaches to ameliorate cachexia are urgently needed, and thus, the role of medicinal plants has received considerable importance in this respect due to their beneficial health properties. Increasing evidence indicates great potential of medicinal plants and their phytochemicals as an alternative and promising treatment strategy to reduce the symptoms of many diseases including cachexia. This article reviews the current status of cachexia, the molecular mechanisms of primary events driving cachexia, and state-of-the-art knowledge that reports the preventive and therapeutic activities of multiple families of phytochemical compounds and their pharmacological mode of action, which may hold promise as an alternative treatment modality for the management of cachexia. Based on our review of various in vitro and in vivo models of cachexia, we would conclude that phytochemicals may have therapeutic potential to attenuate cachexia, although clinical trials are required to unequivocally confirm this premise.

Inflammation: Roles in Skeletal Muscle Atrophy

Various diseases can cause skeletal muscle atrophy, usually accompanied by inflammation, mitochondrial dysfunction, apoptosis, decreased protein synthesis, and enhanced proteolysis. The underlying mechanism of inflammation in skeletal muscle atrophy is extremely complex and has not been fully elucidated, thus hindering the development of effective therapeutic drugs and preventive measures for skeletal muscle atrophy. In this review, we elaborate on protein degradation pathways, including the ubiquitin-proteasome system (UPS), the autophagy-lysosome pathway (ALP), the calpain and caspase pathways, the insulin growth factor 1/Akt protein synthesis pathway, myostatin, and muscle satellite cells, in the process of muscle atrophy. Under an inflammatory environment, various pro-inflammatory cytokines directly act on nuclear factor-κB, p38MAPK, and JAK/STAT pathways through the corresponding receptors, and then are involved in muscle atrophy. Inflammation can also indirectly trigger skeletal muscle atrophy by changing the metabolic state of other tissues or cells. This paper explores the changes in the hypothalamic-pituitary-adrenal axis and fat metabolism under inflammatory conditions as well as their effects on skeletal muscle. Moreover, this paper also reviews various signaling pathways related to muscle atrophy under inflammatory conditions, such as cachexia, sepsis, type 2 diabetes mellitus, obesity, chronic obstructive pulmonary disease, chronic kidney disease, and nerve injury. Finally, this paper summarizes anti-amyotrophic drugs and their therapeutic targets for inflammation in recent years. Overall, inflammation is a key factor causing skeletal muscle atrophy, and anti-inflammation might be an effective strategy for the treatment of skeletal muscle atrophy. Various inflammatory factors and their downstream pathways are considered promising targets for the treatment and prevention of skeletal muscle atrophy.

Immunomodulatory effects of black solo garlic (Allium sativum L.) on streptozotocin-induced diabetes in Wistar rats

Diabetes mellitus is a chronic disease that leads to different complications. Therefore, this study aims to investigate the immunomodulatory effects of the black solo garlic on streptozotocin (STZ)-induced diabetic rats. The Wistar rats were grouped into six groups of: normal control, negative control, treatment dose of 6.5 g/kg, 13.5 g/kg, and 26 g/kg body weight, and positive control glibenclamide. In addition to normal control, rats were induced with STZ on day 8–11. Also, steeping black solo garlic or glibenclamide was administered on the day 12–19. The experimental animals were sacrificed on day 20 and tumor necrosis factor (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β) and interferon gamma (IFN-γ) were measured using ELISA. The results showed that the administration of steeping black solo garlic significantly decreased levels of IL-1β, IL-6 and TNF-α as well as increased IFN-γ with the immunity of STZ-induced rats.

Egg components reverse the atrophy induced by injury in skeletal muscles

Skeletal muscle atrophy is the loss of muscle tissue caused by factors such as inactivity, malnutrition, aging, and injury. In this study, we aimed to investigate whether egg components exert inhibitory effects on muscle atrophy. An egg mix solution was orally administered for 10 consecutive days to male C57BL/6J mice injected with cardiotoxin in the tibialis anterior (TA) muscle. The administration of egg mixture significantly decreased the atrogin-1 and MuRF-1 protein levels, key factors in muscle atrophy, as observed by western blotting. Furthermore, we investigated the effects of egg components such as avidin, lecithin, biotin, 3-sn-phosphatidylcholine, and L-α-phosphatidylcholine on dexamethasone (DEX)-treated C2C12 myotubes. Lecithin, biotin, 3-sn-phosphatidylcholine, and L-α-phosphatidylcholine in egg yolk significantly recovered the diameters of C2C12 myotubes decreased upon DEX application. Avidin did not show such reversal. Biotin, 3-sn-phosphatidylcholine, and L-α-phosphatidylcholine also attenuated atrogin-1 protein expression enhanced by DEX. Our findings reveal that egg yolk components could contribute to the reversal of skeletal muscle atrophy induced by muscle injury.

Skeletal Muscle Deconditioning in Breast Cancer Patients Undergoing Chemotherapy: Current Knowledge and Insights From Other Cancers

Breast cancer represents the most commonly diagnosed cancer while neoadjuvant and adjuvant chemotherapies are extensively used in order to reduce tumor development and improve disease-free survival. However, chemotherapy also leads to severe off-target side-effects resulting, together with the tumor itself, in major skeletal muscle deconditioning. This review first focuses on recent advances in both macroscopic changes and cellular mechanisms implicated in skeletal muscle deconditioning of breast cancer patients, particularly as a consequence of the chemotherapy treatment. To date, only six clinical studies used muscle biopsies in breast cancer patients and highlighted several important aspects of muscle deconditioning such as a decrease in muscle fibers cross-sectional area, a dysregulation of protein turnover balance and mitochondrial alterations. However, in comparison with the knowledge accumulated through decades of intensive research with many different animal and human models of muscle atrophy, more studies are necessary to obtain a comprehensive understanding of the cellular processes implicated in breast cancer-mediated muscle deconditioning. This understanding is indeed essential to ultimately lead to the implementation of efficient preventive strategies such as exercise, nutrition or pharmacological treatments. We therefore also discuss potential mechanisms implicated in muscle deconditioning by drawing a parallel with other cancer cachexia models of muscle wasting, both at the pre-clinical and clinical levels.

Ganoderic acid alleviates chemotherapy-induced fatigue in mice bearing colon tumor

Chemotherapy-related fatigue (CRF) is increasingly being recognized as one of the severe symptoms in patients undergoing chemotherapy, which not only largely reduces the quality of life in patients, but also diminishes their physical and social function. At present, there is no effective drug for preventing and treating CRF. Ganoderic acid (GA), isolated from traditional Chinese medicine Ganoderma lucidum, has shown a variety of pharmacological activities such as anti-tumor, anti-inflammation, immunoregulation, etc. In this study, we investigated whether GA possessed anti-fatigue activity against CRF. CT26 tumor-bearing mice were treated with 5-fluorouracil (5-FU, 30 mg/kg) and GA (50 mg/kg) alone or in combination for 18 days. Peripheral and central fatigue-related behaviors, energy metabolism and inflammatory factors were assessed. We demonstrated that co-administration of GA ameliorated 5-FU-induced peripheral muscle fatigue-like behavior via improving muscle quality and mitochondria function, increasing glycogen content and ATP production, reducing lactic acid content and LDH activity, and inhibiting p-AMPK, IL-6 and TNF-α expression in skeletal muscle. Co-administration of GA also retarded the 5-FU-induced central fatigue-like behavior accompanied by down-regulating the expression of IL-6, iNOS and COX2 in the hippocampus through inhibiting TLR4/Myd88/NF-κB pathway. These results suggest that GA could attenuate 5-FU-induced peripheral and central fatigue in tumor-bearing mice, which provides evidence for GA as a potential drug for treatment of CRF in clinic.

Inflammation and Skeletal Muscle Wasting During Cachexia

Cachexia is the involuntary loss of muscle and adipose tissue that strongly affects mortality and treatment efficacy in patients with cancer or chronic inflammatory disease. Currently, no specific treatments or interventions are available for patients developing this disorder. Given the well-documented involvement of pro-inflammatory cytokines in muscle and fat metabolism in physiological responses and in the pathophysiology of chronic inflammatory disease and cancer, considerable interest has revolved around their role in mediating cachexia. This has been supported by association studies that report increased levels of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) in some, but not all, cancers and in chronic inflammatory diseases such as chronic obstructive pulmonary disease (COPD) and rheumatoid arthritis (RA). In addition, preclinical studies including animal disease models have provided a substantial body of evidence implicating a causal contribution of systemic inflammation to cachexia. The presence of inflammatory cytokines can affect skeletal muscle through several direct mechanisms, relying on activation of the corresponding receptor expressed by muscle, and resulting in inhibition of muscle protein synthesis (MPS), elevation of catabolic activity through the ubiquitin-proteasomal system (UPS) and autophagy, and impairment of myogenesis. Additionally, systemic inflammatory mediators indirectly contribute to muscle wasting through dysregulation of tissue and organ systems, including GCs via the hypothalamus-pituitary-adrenal (HPA) axis, the digestive system leading to anorexia-cachexia, and alterations in liver and adipocyte behavior, which subsequently impact on muscle. Finally, myokines secreted by skeletal muscle itself in response to inflammation have been implicated as autocrine and endocrine mediators of cachexia, as well as potential modulators of this debilitating condition. While inflammation has been shown to play a pivotal role in cachexia development, further understanding how these cytokines contribute to disease progression is required to reveal biomarkers or diagnostic tools to help identify at risk patients, or enable the design of targeted therapies to prevent or delay the progression of cachexia.

Corylifol A from Psoralea corylifolia L. Enhances Myogenesis and Alleviates Muscle Atrophy

Inflammatory conditions caused by cancer, chronic diseases or aging can lead to skeletal muscle atrophy. We identified myogenic compounds from Psoralea corylifolia (PC), a medicinal plant that has been used for the treatment of inflammatory and skin diseases. C2C12 mouse skeletal myoblasts were differentiated in the presence of eight compounds isolated from PC to evaluate their myogenic potential. Among them, corylifol A showed the strongest transactivation of MyoD and increased expression of myogenic markers, such as MyoD, myogenin and myosin heavy chain (MHC). Corylifol A increased the number of multinucleated and MHC-expressing myotubes. We also found that the p38 MAPK signaling pathway is essential for the myogenic action of corylifol A. Atrophic condition was induced by treatment with dexamethasone. Corylifol A protected against dexamethasone-induced myotube loss by increasing the proportion of multinucleated MHC-expressing myotubes compared with dexamethasone-damaged myotubes. Corylifol A reduced the expression of muscle-specific ubiquitin-E3 ligases (MAFbx and MuRF1) and myostatin, while activating Akt. These dual effects of corylifol A, inhibition of catabolic and activation of anabolic pathways, protect myotubes against dexamethasone damage. In summary, corylifol A isolated from P. corylifolia alleviates muscle atrophic condition through activating myoblast differentiation and suppressing muscle degradation in atrophic conditions.