The role of mitochondria in aging of skeletal muscle

Abstract

Aging can be characterized as a time dependent decline of maximal functionality that affects tissues and organs of the whole body. Such is induced by the progressive loss of redundant components and leads to an increased susceptibility to disease and risk of death. Regarding the aging of skeletal muscle, it has been pointed out that mitochondria is a key factor behind the loss of redundancy and functionality, since this organelle has a major role in cellular homeostasis particularly at the level of the bioenergetic status. Decreased activities of the mitochondrial electron transport chain complexes and an increased release of reactive oxygen species from mitochondria are well documented with age; it is suggested that the mitochondrial loss of function results from the increased oxidative damage to proteins, lipids, and DNA of this organelle. However, it is important to be aware that the mitochondrial loss of function could also be a consequence, rather than a cause, of the cellular deterioration with age, which compromises mitochondrial biogenesis, mitochondrial protein turnover and autophagocytosis of damaged mitochondria. In this review several topics will be addressed regarding the age-related loss of skeletal muscle redundancy associated with mitochondrial dysfunction, emphasizing hypotheses for underlying mechanisms. In addition, we discuss some of the cellular mechanisms that can be pointed out as being responsible for the age-related mitochondrial dysfunction.

Mitochondrial respiratory and antioxidative enzyme activities in turkey meat

“…The tendentially reduced MRA in samples with a lower pH 24 h p.m. indicates the impact of pH on these parameters, probably by changing proteins/enzymes within the ETC. As the ETC of the mitochondria is the main source of ROS, a reduced oxidative phosphorylation, because of the lower pH, increases the ROS production accompanied with the activation of the antioxidative enzymes like SOD, GPx and GR (Figueiredo et al, 2008). This assumption might explain the higher activities of the SOD 20 min p.m. in the samples with lower pH 24 h p.m .…”

“…This assumption might explain the higher activities of the SOD 20 min p.m. in the samples with lower pH 24 h p.m . However, increasing concentrations of ROS can damage the proteins of the ETC itself, thereby reducing the MRA (Figueiredo et al, 2008), and Loh et al (2002) presented that peroxides decrease the pH values in the tissue (circulus vitiosus). It is quite difficult to clarify whether the mitochondria in the samples are primarily altered because of the effects of the ROS and pH or secondarily because of the differences in the pH reduction after slaughter of the animals.…”

“…O 2 2 is oxidised to hydrogen peroxide (H 2 O 2 ) catalysed by the antioxidative enzyme superoxide dismutase (SOD). H 2 O 2 is subsequently broken down by the glutathione peroxidase (GPx) or catalase to H 2 O or H 2 O and O 2 (Figueiredo et al, 2008). Taking into account the impact of the mitochondria and the antioxidative enzymes on the proportion of Mb redox forms, an influence on the meat quality could be suggested.…”

“…An important feature is the fibre-type composition of the muscles, with breast muscles only consisting of fast-twitch glycolytic (FTG) fibres containing low Mb and mitochondria concentrations, and leg muscles additionally containing Mb and mitochondria-rich slow-twitch oxidative (STO) fibres (Papinaho et al, 1996;Mancini and Hunt, 2005). Proportions of oxy-, deoxy-and metMb are strongly related to the oxidative status of the tissue influenced by the oxygen consumption and the antioxidative capacity of the tissue (Figueiredo et al, 2008). The electron transport chain (ETC) of mitochondria is not only responsible for the oxygen consumption of the tissue, but is also a significant source of reactive oxygen species (ROS (Figueiredo et al, 2008).…”

“…Proportions of oxy-, deoxy-and metMb are strongly related to the oxidative status of the tissue influenced by the oxygen consumption and the antioxidative capacity of the tissue (Figueiredo et al, 2008). The electron transport chain (ETC) of mitochondria is not only responsible for the oxygen consumption of the tissue, but is also a significant source of reactive oxygen species (ROS (Figueiredo et al, 2008). Taking into account the impact of the mitochondria and the antioxidative enzymes on the proportion of Mb redox forms, an influence on the meat quality could be suggested.…”