Carnosol and its analogues attenuate muscle atrophy and fat lipolysis induced by cancer cachexia

Abstract

Background Cancer cachexia is a multifactorial debilitating syndrome that directly accounts for more than 20% of cancer deaths while there is no effective therapeutic approach for treatment of cancer cachexia. Carnosol (CS) is a bioactive diterpene compound present in Lamiaceae spp., which has been demonstrated to have antioxidant, anti‐inflammatory, and anticancer properties. But its effects on cancer cachexia and the possible mechanism remain a mystery. Methods The in vitro cell models of C2C12 myotube atrophy and 3T3‐L1 mature adipocyte lipolysis were used to check the activities of CS and its synthesized analogues. C26 tumour‐bearing BALB/c mice were applied as the animal model to examine their therapeutic effects on cancer cachexia in vivo. Levels of related signal proteins in both in vitro and in vivo experiments were examined using western blotting to study the possible mechanisms. Results Carnosol and its analogues [dimethyl‐carnosol (DCS) and dimethyl‐carnosol‐D6 (DCSD)] alleviated myotube atrophy of C2C12 myotubes and lipolysis of 3T3‐L1 adipocytes in vitro. Interestingly, CS and its analogues exhibited stronger inhibitive effects on muscle atrophy induced by tumour necrosis factor‐α (TNF‐α) (CS, P < 0.001; DCS, P < 0.001; DCSD, P < 0.001) in C2C12 myoblasts than on muscle atrophy induced by IL‐6 (CS, P < 0.05; DCS, P = 0.08; DCSD, P < 0.05). In a C26 tumour‐bearing mice model, administration of CS or its analogue DCSD significantly prevented body weight loss without affecting tumour size. At the end of the experiment, the body weight of mice treated with CS and DCSD was significantly increased by 11.09% (P < 0.01) and 11.38% (P < 0.01) compared with that of the C26 model group. CS and DCSD also improved the weight loss of epididymal adipose tissue in C26 model mice by 176.6% (P < 0.01) and 48.2% (P < 0.05) increase, respectively. CS and DCSD treatment partly preserved gastrocnemius myofibres cross‐sectional area. CS treatment decreased the serum level of TNF‐α (−95.02%, P < 0.01) but not IL‐6 in C26 tumour‐bearing mice. Inhibition on NF‐κB and activation of Akt signalling pathway were involved in the ameliorating effects of CS and its analogues on muscle wasting both in vitro and in vivo. CS and its analogues also alleviated adipose tissue loss by inhibiting NF‐κB and AMPK signalling pathways both in vitro and in vivo. Conclusions CS and its analogues exhibited anticachexia effects mainly by inhibiting TNF‐α/NF‐κB pathway and decreasing muscle and adipose tissue loss. CS and its analogues might be promising drug candidates for the treatment of cancer cachexia.

A Bioassay-Guided Fractionation of Rosemary Leaf Extract Identifies Carnosol as a Major Hypertrophy Inducer in Human Skeletal Muscle Cells

“…Our data clearly indicated that carnosol did not affect Akt or mTOR phosphorylation/activation levels, in agreement with the study by Vlavcheski et al showing that in L6 rat skeletal muscle cells, carnosol regulates glucose homeostasis, but does not affect the PI3K-Akt pathway [30]. Conversely, in C2C12 myoblasts incubated with conditioned medium from C26 colon carcinoma cells or pro-inflammatory cytokines, and in C26 tumor cell-bearing mice, carnosol activates the Akt signaling pathway and ameliorates cachexia-induced muscle atrophy [29]. These data suggest that carnosol activates the Akt signaling cascade in cells exposed to pro-inflammatory factors, such as in cachexia, but not in normal muscle cells.…”

“…Here, we found that RLE was sufficient to induce hypertrophy of human muscle cells and that carnosol, a phenolic diterpene, was the active component mediating this effect in young and aged skeletal muscle cells. Recently, it has been reported that carnosol has anti-cachectic effects mainly by decreasing muscle and adipose tissue loss, in vitro in C2C12 mouse myoblasts incubated with conditioned medium from C26 colon carcinoma cells or with pro-inflammatory cytokines, and in vivo in C26 tumor cell-bearing mice [29]. Moreover, carnosol can regulate glucose homeostasis in skeletal muscle via AMPK-dependent GLUT4 glucose transporter translocation [30], and could be potentially used against insulin resistance and type 2 diabetes mellitus.…”

Pharmacological Inhibition of HMGB1 Prevents Muscle Wasting

“…Pro-inflammatory cytokines such as IL-6, TNF α, and IL-1β promote the transcriptional activation of atrophy-related genes Atrogin1 and MuRF1, which play a major role in the occurrence and development of muscle wasting. Activation of inflammatory pathways such as NF-κB signaling pathway could cause muscle wasting both in cachexia mouse models and muscles of cancer cachexia patients ( Guttridge et al, 2000 ; Zhou et al, 2003 ; Rhoads et al, 2010 ; Lu et al, 2021 ). Inflammatory factors can activate the NF-κB signaling pathway, and the activation of the NF-κB signaling pathway can reversely enhance inflammation by promoting the transcription of inflammatory factors ( Camargo et al, 2015 ; Lu et al, 2021 ).…”

“…Activation of inflammatory pathways such as NF-κB signaling pathway could cause muscle wasting both in cachexia mouse models and muscles of cancer cachexia patients ( Guttridge et al, 2000 ; Zhou et al, 2003 ; Rhoads et al, 2010 ; Lu et al, 2021 ). Inflammatory factors can activate the NF-κB signaling pathway, and the activation of the NF-κB signaling pathway can reversely enhance inflammation by promoting the transcription of inflammatory factors ( Camargo et al, 2015 ; Lu et al, 2021 ). This is a vicious circle.…”

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“…Pro-inflammatory cytokines such as IL-6, TNF α, and IL-1β promote the transcriptional activation of atrophyrelated genes Atrogin1 and MuRF1, which play a major role in the occurrence and development of muscle wasting. Activation of inflammatory pathways such as NF-κB signaling pathway could cause muscle wasting both in cachexia mouse models and muscles of cancer cachexia patients (Guttridge et al, 2000;Zhou et al, 2003;Rhoads et al, 2010;Lu et al, 2021). Inflammatory factors can activate the NF-κB signaling pathway, and the activation of the NF-κB signaling pathway can reversely enhance inflammation by promoting the transcription of inflammatory factors (Camargo et al, 2015;Lu et al, 2021).…”