Project description:Cachexia is frequently accompanied by severe metabolic derangements, although the mechanisms responsible for this debilitating condition remain unclear. Pyruvate dehydrogenase kinase (PDK)4, a critical regulator of cellular energetic metabolism, was found elevated in experimental models of cancer, starvation, diabetes, and sepsis. Here we aimed to investigate the link between PDK4 and the changes in muscle size in cancer cachexia. High PDK4 and abnormal energetic metabolism were found in the skeletal muscle of colon-26 tumor hosts, as well as in mice fed a diet enriched in Pirinixic acid, previously shown to increase PDK4 levels. Viral-mediated PDK4 overexpression in myotube cultures was sufficient to promote myofiber shrinkage, consistent with enhanced protein catabolism and mitochondrial abnormalities. On the contrary, blockade of PDK4 was sufficient to restore myotube size in C2C12 cultures exposed to tumor media. Our data support, for the first time, a direct role for PDK4 in promoting cancer-associated muscle metabolic alterations and skeletal muscle atrophy.-Pin, F., Novinger, L. J., Huot, J. R., Harris, R. A., Couch, M. E., O'Connell, T. M., Bonetto, A. PDK4 drives metabolic alterations and muscle atrophy in cancer cachexia.
Project description:Cachexia is characterized by inexorable muscle wasting that significantly affects patient prognosis and increases mortality. Therefore, understanding the molecular basis of this muscle wasting is of significant importance. Recent work showed that components of the forkhead box O (FoxO) pathway are increased in skeletal muscle during cachexia. In the current study, we tested the physiological significance of FoxO activation in the progression of muscle atrophy associated with cachexia. FoxO-DNA binding dependent transcription was blocked in the muscles of mice through injection of a dominant negative (DN) FoxO expression plasmid prior to inoculation with Lewis lung carcinoma cells or the induction of sepsis. Expression of DN FoxO inhibited the increased mRNA levels of atrogin-1, MuRF1, cathepsin L, and/or Bnip3 and inhibited muscle fiber atrophy during cancer cachexia and sepsis. Interestingly, during control conditions, expression of DN FoxO decreased myostatin expression, increased MyoD expression and satellite cell proliferation, and induced fiber hypertrophy, which required de novo protein synthesis. Collectively, these data show that FoxO-DNA binding-dependent transcription is necessary for normal muscle fiber atrophy during cancer cachexia and sepsis, and further suggest that basal levels of FoxO play an important role during normal conditions to depress satellite cell activation and limit muscle growth.
Project description:Inflammation-mediated skeletal muscle wasting occurs in patients with sepsis and cancer cachexia. Both conditions severely affect patient morbidity and mortality. Lithium chloride has previously been shown to enhance myogenesis and prevent certain forms of muscular dystrophy. However, to our knowledge, the effect of lithium chloride treatment on sepsis-induced muscle atrophy and cancer cachexia has not yet been investigated. In this study, we aimed to examine the effects of lithium chloride using in vitro and in vivo models of cancer cachexia and sepsis. Lithium chloride prevented wasting in myotubes cultured with cancer cell-conditioned media, maintained the expression of the muscle fiber contractile protein, myosin heavy chain 2, and inhibited the upregulation of the E3 ubiquitin ligase, Atrogin-1. In addition, it inhibited the upregulation of inflammation-associated cytokines in macrophages treated with lipopolysaccharide. In the animal model of sepsis, lithium chloride treatment improved body weight, increased muscle mass, preserved the survival of larger fibers, and decreased the expression of muscle-wasting effector genes. In a model of cancer cachexia, lithium chloride increased muscle mass, enhanced muscle strength, and increased fiber cross-sectional area, with no significant effect on tumor mass. These results indicate that lithium chloride exerts therapeutic effects on inflammation-mediated skeletal muscle wasting, such as sepsis-induced muscle atrophy and cancer cachexia.
Project description:BACKGROUND:Cancer cachexia as a metabolic syndrome can lead to at least 25% of cancer deaths. The inhibition of muscle atrophy is a main strategy to treat cancer cachexia. In this process, myostatin (MSTN) can exert a dual effect on protein metabolism, including inhibition of protein biosynthesis and enhancement of protein degradation. In this study, we will test the effect on muscle atrophy induced by cancer cachexia of IMB0901, a MSTN inhibitor. METHODS:Two high-throughput screening models against MSTN were developed. By screening, IMB0901, 2-((1-(3,4-dichlorophenyl)-1H-pyrazolo [3,4-d] pyrimidin-4-yl) amino) butan-1-ol, was picked out from the compound library. The in vitro cell model and the C26 animal model of muscle atrophy induced by cancer cachexia were used to determine the pharmacological activity of IMB0901. Whether IMB0901 could inhibit the aggravating effect of doxorubicin on muscle wasting was examined in vitro and in vivo. RESULTS:IMB0901 inhibited the MSTN promoter activity, the MSTN signaling pathway, and the MSTN positive feedback regulation. In atrophied C2C12 myotubes, IMB0901 had a potent efficiency of decreasing MSTN expression and modulating MSTN signaling pathway which was activated by C26-conditioned medium (CM). In C2C12 myotubes, the expressions of three common myotube markers, myosin heavy chain (MyHC), myogenic differentiation 1 (MyoD), and myogenin (MyoG), were downregulated by CM, which could be efficiently reversed by IMB0901 via reduction of ubiquitin-mediated proteolysis and enhancement of AKT/mTOR-mediated protein synthesis. In the C26 animal model, IMB0901 mitigated the weight loss of body, quadricep and liver, and protected the quadriceps cell morphology. Furthermore, IMB0901 decreased the expression of two E3 ligases Atrogin-1 and MuRF-1 in the quadriceps in vivo. At the cellular level, IMB0901 had no influence on anti-tumor effect of three chemotherapeutic agents (cisplatin, doxorubicin, and gemcitabine) and lowered doxorubicin-induced upregulation of MSTN in C2C12 myotubes. IMB0901 did not affect the inhibitory effect of doxorubicin on C26 tumor and delayed the weight loss of muscle and adipose tissue caused by C26 tumor and doxorubicin. CONCLUSIONS:IMB0901 inhibits muscle atrophy induced by cancer cachexia by suppressing ubiquitin-mediated proteolysis and promoting protein synthesis. These findings collectively suggest that IMB0901 is a promising leading compound for the management of muscle atrophy induced by cancer cachexia.
Project description:Cancer is commonly associated with cachexia, a paraneoplastic syndrome characterized by body weight loss, muscle wasting, adipose tissue atrophy and inflammation. Chronic alcohol consumption increases the risk of multiple types of cancer, and enhances cancer-associated cachexia (CAC), but the underlying mechanisms remain poorly defined. To test, C57BL/6 mice were fed with 0% or 20% (w/v) alcohol for 3 months, then inoculated with B16BL6 melanoma cells subcutaneously in the right side of the hip and continued to feed with/without alcohol for 3 or 4 weeks. Alcohol intake upregulated ALDH1A1 expression and elevated retinoic acid (RA) content in inguinal white adipose tissue (iWAT), which led to enhanced iWAT browning and brown adipose tissue (BAT) activation, accelerating fat loss. Moreover, alcohol increased muscle loss through augmenting muscle protein degradation, cell apoptosis and inflammation. In addition, alcohol reduced satellite cell density and impaired myogenesis in skeletal muscle. Taken together, alcohol aggravates cancer-associated cachexia at least partially through elevating adipose browning and muscle atrophy.
Project description:In the present study, the BCAAs (branched-chain amino acids) leucine and valine caused a significant suppression in the loss of body weight in mice bearing a cachexia-inducing tumour (MAC16), producing a significant increase in skeletal muscle wet weight, through an increase in protein synthesis and a decrease in degradation. Leucine attenuated the increased phosphorylation of PKR (double-stranded-RNA-dependent protein kinase) and eIF2alpha (eukaryotic initiation factor 2alpha) in skeletal muscle of mice bearing the MAC16 tumour, due to an increased expression of PP1 (protein phosphatase 1). Weight loss in mice bearing the MAC16 tumour was associated with an increased amount of eIF4E bound to its binding protein 4E-BP1 (eIF4E-binding protein 1), and a progressive decrease in the active eIF4G-eIF4E complex due to hypophosphorylation of 4E-BP1. This may be due to a reduction in the phosphorylation of mTOR (mammalian target of rapamycin), which may also be responsible for the decreased phosphorylation of p70(S6k) (70 kDa ribosomal S6 kinase). There was also a 5-fold increase in the phosphorylation of eEF2 (eukaryotic elongation factor 2), which would also decrease protein synthesis through a decrease in translation elongation. Treatment with leucine increased phosphorylation of mTOR and p70(S6k), caused hyperphosphorylation of 4E-BP1, reduced the amount of 4E-BP1 associated with eIF4E and caused an increase in the eIF4G-eIF4E complex, together with a reduction in phosphorylation of eEF2. These changes would be expected to increase protein synthesis, whereas a reduction in the activation of PKR would be expected to attenuate the increased protein degradation.