Skeletal muscle function during the progression of cancer cachexia in the male Apc^Min/+ mouse

Abstract

While cancer-induced skeletal muscle wasting has been widely investigated, the drivers of cancer-induced muscle functional decrements are only beginning to be understood. Decreased muscle function impacts cancer patient quality of life and health status, and several potential therapeutics have failed in clinical trials due to a lack of functional improvement. Furthermore, systemic inflammation and intrinsic inflammatory signaling's role in the cachectic disruption of muscle function requires further investigation. We examined skeletal muscle functional properties during cancer cachexia and determined their relationship to systemic and intrinsic cachexia indices. Male Apc (MIN) mice were stratified by percent body weight loss into weight stable (WS; <5% loss) or cachectic (CX; >5% loss). Age-matched C57BL/6 littermates served as controls. Tibialis anterior (TA) twitch properties, tetanic force, and fatigability were examined in situ. TA protein and mRNA expression were examined in the nonstimulated leg. CX decreased muscle mass, tetanic force (P), and specific tetanic force (P). Whole body and muscle fatigability were increased in WS and CX. CX had slower contraction rates, +dP/d t and -dP/d t, which were inversely associated with muscle signal transducer and activator of transcription 3 ( STAT3) and p65 activation. STAT3 and p65 activation were also inversely associated with P. However, STAT3 was not related to P or fatigue. Muscle suppressor of cytokine signaling 3 mRNA expression was negatively associated with TA weight, P, and P but not fatigue. Our study demonstrates that multiple functional deficits that occur with cancer cachexia are associated with increased muscle inflammatory signaling. Notably, muscle fatigability is increased in the MIN mouse before cachexia development. NEW & NOTEWORTHY Recent studies have identified decrements in skeletal muscle function during cachexia. We have extended these studies by directly relating decrements in muscle function to established cachexia indices. Our results demonstrate that a slow-fatigable contractile phenotype is developed during the progression of cachexia that coincides with increased muscle inflammatory signaling. Furthermore, regression analysis identified predictors of cancer-induced muscle dysfunction. Last, we report the novel finding that whole body and muscle fatigability were increased before cachexia development.

The regulation of skeletal muscle fatigability and mitochondrial function by chronically elevated interleukin‐6

“…Ageing and several chronic inflammatory diseases have been associated with preferential atrophy of type II muscle fibres in both humans and animal models (Carson et al., ; Lexell, ; Wang & Pessin, ). Researchers in our laboratory previously showed that the TA, which has primarily type IIb muscle fibres (Bloemberg & Quadrilatero, ), had reduced force and increased muscle fatigability in tumour‐bearing mice associated with increased STAT3 and SOCS3 activation (Murphy, Chee, Trieu, Naim, & Lynch, ; VanderVeen et al., ). Although more work is needed to understand the fibre‐type specificity of IL‐6, the COXIV and cytochrome c protein expression in the murine quadriceps muscle was susceptible to IL‐6 (Puppa et al., ), but was unchanged in the gastrocnemius (White et al., ).…”

“…The mouse was place on the apparatus maintained at 37°C throughout the entirety of the procedure (Bonetto, Andersson, & Waning, ). Functional analysis of the TA muscle in situ , which maintains the host nerve and blood supply, has been described previously (VanderVeen et al., ). The sciatic nerve was exposed proximal to the knee and maintained using warmed mineral oil.…”

“…Owing to tissue availability, the EDL muscle, a highly glycolytic muscle, was used. The whole EDL was homogenized in extraction buffer (0.1 m KH 2 PO 4 /Na 2 HPO 4 , 2 m m EDTA, pH 7.2), and COX activity was determined by measuring the rate of oxidation of fully reduced cytochrome c at 550 nm using a Sigma Aldrich kit (#CYTOCOX1) and spectrophotometer (Eppendorf) as previously described (VanderVeen et al., ).…”

“…Although type I muscle fibres are susceptible to disuse atrophy (Coyle, Martin, Bloomfield, Lowry, & Holloszy, ; Iqbal, Ostojic, Singh, Joseph, & Hood, ; Thomason & Booth, ), chronic inflammatory diseases, such as cancer‐induced muscle wasting, have been associated with preferential atrophy of type II muscle fibres (Carson, Hardee, & VanderVeen, ; Wang & Pessin, ). The tibialis anterior (TA), which has primarily type II muscle fibres, has been shown to have increased muscle fatigability and reduced muscle force in tumour‐bearing mice (VanderVeen et al., ). We have previously shown that the TA is susceptible to inflammation‐induced muscle wasting (Hardee, Counts et al., ); whether elevated inflammatory cytokines alone can disrupt the TA skeletal muscle function has not been determined.…”

“…Furthermore, we have previously shown that gp130 expression is greater in the TA compared with the soleus and gastrocnemius, suggesting greater IL‐6 sensitivity in faster muscles (Puppa et al., ). Interestingly, skeletal muscle weakness in tumour‐bearing mice was associated with increased skeletal muscle signal transducer and activator of transcription 3 (STAT3) and suppressor of cytokine signaling 3 (SOCS3), two primary downstream targets of IL‐6 (VanderVeen et al., ). The purpose of the present study was to determine whether chronic elevation of systemic IL‐6 for 2 weeks was sufficient to disrupt skeletal muscle force, fatigue and mitochondrial function in the TA.…”