Relationship between Sarcopenia and mTOR Pathway in Patients with Colorectal Cancer: Preliminary Report

Abstract

Sarcopenia is a syndrome characterized by loss of muscle mass and strength that impacts clinical outcomes and mortality in cancer patients. Although the molecular pathways involved in sarcopenia are not fully elucidated, the decrease in protein synthesis rate appears to be one of the most important events. The objective of this study was to investigate the relationship between sarcopenia and mTOR signaling pathway in patients undergoing colorectal resection surgery. Three groups of patients were assessed: 1) the control group (no cancer, no sarcopenia), 2) the cancer non-sarcopenic group and 3) the cancer sarcopenic group. All individuals were evaluated in relation to presence of sarcopenia and mTOR signaling pathway. Sarcopenia was evaluated by the combination of low muscle mass and low muscle strength, measured using computerized tomography images, and hand grip strength, respectively. Rectus abdominis muscle biopsy was performed at the time of surgery. mTOR pathway was analyzed by MILLIPLEX Map Kit Phospho/total mTOR 2-Plex Magnetic Bead Panel. Results were presented by phosphor/total mTOR ratio. Independent T test, Kruskal-Wallis test, and Dunn-Bonferroni post hoc were performed for statistical analysis and P < 0.05 was considered. Thirty-six patients and five controls were evaluated. A total of 13 cancer patients (36.1%) had sarcopenia. The phospho/total mTOR ratio was different between the control group (0.167 MFI) and the cancer non-sarcopenic group (0.055 MFI) (P = 0.026) as well as between the control group (0.167 MFI) and the cancer sarcopenic group (0.0049 MFI) (P = 0.041). No difference was observed on the median phospho/total mTOR ratio between the cancer groups (P > 0.05). More research is needed to extrapolate these results.