Characterization of Mitochondrial Content and Respiratory Capacities of Broiler Chicken Skeletal Muscles with Different Muscle Fiber Compositions

Abstract

Mitochondrial content is regarded a useful feature to distinguish muscle-fiber types in terms of energy metabolism in skeletal muscles. Increasing evidence suggests that specific mitochondrial bioenergetic phenotypes exist in metabolically different muscle fibers. A few studies have examined the energetic properties of skeletal muscle in domestic fowls; however, no information on muscle bioenergetics in broiler chickens selectively bred for faster growth is available. In this study, we aimed to characterize the mitochondrial contents and functions of chicken skeletal muscle consisting entirely of type I (oxidative) (M. pubo-ischio-femoralis pars medialis), type IIA (glycolytic/oxidative) (M. pubo-ischio-femoralis pars lateralis), and type IIB (glycolytic) (M. pectoralis superficialis) muscle fibers. Citrate synthase (CS) activity was the highest in type IIA muscle tissues and isolated mitochondria, among the muscle tissues tested. Although no difference was registered in mitochondrial CS activity between type IIB and type I muscles, tissue CS activity was significantly higher in the latter. Histochemical staining for NADH tetrazolium reductase and the ratio of muscle-tissue to mitochondrial CS activity indicated that type I, type IIA, and type IIB muscle-fiber types showed decreasing mitochondrial content. Mitochondria from type I muscle exhibited a higher coupled respiration rate induced by pyruvate/malate, palmitoyl-CoA/malate, and palmitoyl-carnitine, as respiratory substrates, than type IIB-muscle mitochondria, while the response of mitochondria from type IIA muscle to those substrates was comparable to that of mitochondria from type I muscle. Type IIA-muscle mitochondria exhibited the highest carnitine palmitoyltransferase-2 level among all tissues tested, which may contribute to the higher fatty acid oxidation in these mitochondria. The results suggest that mitochondrial abundance is one of the features differentiating metabolic characteristics of different chicken skeletal muscle types. Moreover, the study demonstrated that type IIA-muscle mitochondria may have distinct metabolic capacities.

Gene expression profiling of the early pathogenesis of wooden breast disease in commercial broiler chickens using RNA-sequencing

“…This observation is in agreement with previous studies which showed mitochondrial damage in affected chickens beginning from the 4 th week of age [7], as well as alterations in energy metabolism in affected chickens at market age [14]. Additionally, the expression of the gene citrate synthase ( CS ) (log2FC -0.56), considered as an important biomarker of mitochondrial content in skeletal muscles [28] was downregulated in affected chickens, indicating decreased mitochondrial content, and hence, reduced muscle bioenergetics capacity in affected chickens. Indeed, in line with the study by Hakamata et al .…”

“…Indeed, in line with the study by Hakamata et al . (2018) who revealed a lower mitochondrial CS activity, and hence, decreased mitochondrial content in pectoral muscles of fast-growing modern broiler chickens [28], it is conceivable that dysregulation of muscle bioenergetics will be exacerbated in Wooden Breast-affected chickens.…”

Differences in Breast Muscle Mitochondrial Respiratory Capacity, Reactive Oxygen Species Generation, and Complex Characteristics between 7-week-old Meat- and Laying-type Chickens

“…Considering that both chicken types were fed the same diet during the study, it is likely that the SC protein abundance in the chicken muscle mitochondria may be metabolically regulated. This study found that meat-type chickens exhibited lower fatty acid oxidation-supported respiration due to decreased CPT2 activity, and similar metabolic features were also found in the mitochondria of broiler skeletal muscles, which consist entirely of oxidative muscle fibers (type I) ( Hakamata et al , 2018 ). This finding allows us to suggest that muscle fiber compositions in the breast muscle might induce different energetic properties between chicken types: However, the muscle of meat-type and laying-type chickens have the same compositions: 100% fast-glycolytic muscle fiber (type IIB) ( Ueda et al , 2005 , Hakamata et al , 2018 ).…”

“…This study found that meat-type chickens exhibited lower fatty acid oxidation-supported respiration due to decreased CPT2 activity, and similar metabolic features were also found in the mitochondria of broiler skeletal muscles, which consist entirely of oxidative muscle fibers (type I) ( Hakamata et al , 2018 ). This finding allows us to suggest that muscle fiber compositions in the breast muscle might induce different energetic properties between chicken types: However, the muscle of meat-type and laying-type chickens have the same compositions: 100% fast-glycolytic muscle fiber (type IIB) ( Ueda et al , 2005 , Hakamata et al , 2018 ). Meanwhile, previous studies have shown that the diameter of muscle fibers with a lower oxidative capacity is smaller than that of fibers with a higher capacity ( van der Laarse et al , 1989 , van Wessel et al , 2010 ).…”

Differential effects of heat stress on oxidative status of skeletal muscle with different muscle fibre compositions in broiler chicken

“…These findings were observed in Musculus pectoralis (Pec) muscle, which consists entirely of glycolytic (type IIB) muscle fibres. Glycolytic muscle fibre has a lower mitochondrial content than oxidative muscle (Hakamata et al, 2018). There have been no comparative studies on oxidative disturbance and resistance in skeletal muscles with different muscle fibre composition of HS-exposed birds.…”