Abstract/Summary

Background Muscle wasting, anorexia, and metabolic dysregulation are common side-effects of cytotoxic chemotherapy, which have a dose-limiting effect on treatment efficacy, and compromise quality of life and mortality. Extracts of Cannabis sativa, and analogues of the major phytocannabinoid Δ9-tetrahydrocannabinol, have been used to ameliorate chemotherapy-induced appetite loss and nausea for decades. However, psychoactive side-effects limit their clinical utility, and they have demonstrated little efficacy against weight loss. We have recently shown that the non-psychoactive phytocannabinoid cannabigerol (CBG) stimulates appetite in healthy rats, without neuromotor side-effects. The present study was thus designed to test whether CBG could attenuate anorexia and/or any other cachectic effects induced by the broad-spectrum chemotherapy agent cisplatin. Methods An acute cachectic phenotype was induced in adult male Lister-hooded rats by administration of 6 mg/kg (i.p.) cisplatin. A total of 66 rats were randomly allocated to groups receiving vehicle only, cisplatin only, or cisplatin and either 60 or 120 mg/kg CBG (po, b.i.d.). Feeding behavior, bodyweight and locomotor activity were recorded for 72 hours, at which point rats were sacrificed for post-mortem analyses. Myofibre atrophy, protein synthesis and autophagy dysregulation were assessed in skeletal muscle, plasma metabolic profiles were obtained by untargeted 1H-NMR metabonomics, and plasma and hypothalamic levels of endocannabinoid-like lipoamines were quantified by targeted HPLC-MS/MS lipidomics. Results CBG (120 mg/kg) modestly increased food intake, predominantly at 36-60hrs (p<0.05), and robustly attenuated cisplatin-induced weight loss from 6.3% to 2.6% at 72hrs (p<0.01). Cisplatin-induced skeletal muscle atrophy was associated with elevated plasma corticosterone and observed selectively in MHC type IIx and IIb fibres, which was reversed by pharmacological rescue of dysregulated Akt/S6-mediated protein synthesis and autophagy processes. Plasma metabonomic analysis revealed cisplatin-induced cachexia was associated with a wide-ranging aberrant metabolic phenotype, involving alterations to glucose, amino acid, choline and lipid metabolism, citrate cycle, gut microbiome function, and nephrotoxicity, which were partially normalized by CBG treatment. Lipidomic analysis of hypothalami and plasma revealed extensive cisplatin-induced dysregulation of central and peripheral lipoamines, including reversible elevations in systemic N-acyl glycine concentrations which were negatively associated with the anti-cachectic effects of CBG treatment. Conclusions Endocannabinoid-like lipoamines may have hitherto unrecognized roles in the metabolic side-effects associated with chemotherapy, with the N-acyl glycine subfamily in particular identified as a potential therapeutic target and/or biomarker of anabolic interventions. CBG-based treatments may represent a novel therapeutic option for chemotherapy-induced cachexia, warranting investigation in tumour-bearing cachexia models.