Colon 26 adenocarcinoma (C26)-induced cancer cachexia impairs skeletal muscle mitochondrial function and content

Abstract

The present study aimed to determine the impact of colon 26 adenocarcinoma (C26)-induced cancer cachexia on skeletal muscle mitochondrial respiration and content. Twelve male CD2F1 mice were injected with C26-cells (tumor bearing (TB) group), whereas 12 age-matched mice received PBS vehicle injection (non-tumor bearing (N-TB) group). Mitochondrial respiration was studied in saponin-permeabilized soleus myofibers. TB mice showed lower body weight (~ 20%) as well as lower soleus, gastrocnemius-plantaris complex and tibialis anterior masses versus N-TB mice (p < 0.05). Soleus maximal state III mitochondrial respiration was 20% lower (10 mM glutamate, 5 mM malate, 5 mM adenosine diphosphate; p < 0.05) and acceptor control ratio (state III/state II) was 15% lower in the TB vs. N-TB (p < 0.05), with the latter suggesting uncoupling. Lower VDAC protein content suggested reduced mitochondrial content in TB versus N-TB (p < 0.05). Skeletal muscle in C26-induced cancer cachexia exhibits reductions in: maximal mitochondrial respiration capacity, mitochondrial coupling and mitochondrial content.

Keywords: Mitochondrial content; Mitochondrial coupling; Mitochondrial homeostasis; Mitochondrial respiration; Muscle wasting; Oxidative phosphorylation.

Figure 1.. C26-tumor cell inoculation induces (A) body, (B) soleus, (C) gastrocnemius-plantaris (GasPL) and (D) tibialis anterior (TA) weight losses.

N-TB = non-tumor bearing mice, TB = tumor bearing mice. Data are mean ± SD. The effects of C26-tumor cell inoculation was evaluated by performing unpaired t-tests. N = 12 per group except for N-TB GasPL where N = 11 and TB and N-TB TA where N = 8.

Figure 2.. C26-induced cancer cachexia is associated with (A&B) similar basal (in presence of 10 mM of glutamate (G), 5 mM of malate (M)) but reduced maximal respiration rates measured (in presence of 10 mM of G, 5 mM of M, 5 mM of adenosine diphosphate (ADP) as well as in addition of 20 mM of succinate (S)), (C) smaller state 2 to state 3 respiration increases and (D) lower acceptor control ratio (ACR) in tumor-bearing mice (TB, filled bars) compared to nontumor bearing mice (N-TB, clear bars).

+ GM → ADP = relative respiration change induced by ADP addition in presence of GM (indicated on the representative trace in panel A by ‘(1)’) and + GM + ADP → + S = relative respiration change induced by S addition in presence of GM + ADP (indicated on the representative trace in panel A by ‘(2)’). Data are mean ± SD. The effects of C26-tumor cell inoculation were evaluated by performing unpaired t-tests. N = 12 for N-TB and N = 11 for TB.

Figure 3.. C26-cancer cachexia alters the content of (A) several mitochondrial complex representative subunits and of (B) the voltage-dependent anion channel (VDAC).

N-TB = non-tumor bearing mice (clear bars), TB = tumor bearing mice (filled bars), CI = representative subunit of mitochondrial complex I, CII = representative subunit of mitochondrial complex II, CIII = representative subunit of mitochondrial complex III, CIV = representative subunit of mitochondrial complex IV and CV = representative subunit of mitochondrial complex V. Data are mean ± SD. The effects of C26-tumor cell inoculation was evaluated by performing unpaired t-tests. For GasPL, N = 12 per group except for TB CV where N = 11. For soleus N = 8 per group.