Attenuation of skeletal muscle atrophy in cancer cachexia by d-myo-inositol 1,2,6-triphosphate

To determine the effectiveness of the polyanionic, metal binding agent d-myo-inositol-1,2,6-triphosphate (alpha trinositol, AT), and its hexanoyl ester (HAT), in tissue wasting in cancer cachexia. The anti-cachexic effect was evaluated in the MAC16 tumour model. Both AT and HAT attenuated the loss of body weight through an increase in the nonfat carcass mass due to an increase in protein synthesis and a decrease in protein degradation in skeletal muscle. The decrease in protein degradation was associated with a decrease in activity of the ubiquitin-proteasome proteolytic pathway and caspase-3 and -8. Protein synthesis was increased due to attenuation of the elevated autophosphorylation of double-stranded RNA-dependent protein kinase, and of eukaryotic initiation factor 2 alpha together with hyperphosphorylation of eIF4E-binding protein 1 and decreased phosphorylation of eukaryotic elongation factor 2. In vitro, AT completely attenuated the protein degradation in murine myotubes induced by both proteolysis-inducing factor and angiotensin II. These results show that AT is a novel therapeutic agent with the potential to alleviate muscle wasting in cancer patients.