Ageing Changes in Mammalian Skeletal Muscle

Abstract

In the course of ageing, biochemical characteristics of mammalian skeletal muscle are shown to become altered mainly within the system of energy metabolism. The enzymatic behaviour of myofibrillar proteins remains virtually unchanged throughout life, but a gradual loss of fibres causes a decrease in muscular strength. Working capacity, however, in terms of prolonged muscular work is considerably reduced with age, because of a less efficient energy metabolism. Enzymes, particularly of the Krebs cycle, show diminished specific activities, and consequently, ATP and phosphocreatine concentrations are lowered. Possible primary and secondary factors responsible for these changes are discussed.

Selective degradation of mitochondria by mitophagy

“…mtDNA mutations lead to synthesis of abnormal mitochondrial proteins or block synthesis altogether, which further exacerbates mitochondrial dysfunction. Thus in postmitotic cells of aged organisms, morphological abnormalities of mitochondria are often observed, including swelling, loss of cristae, and destruction of inner membranes [67][68][69]. Moreover, ATP production and respiration in mitochondria from aged animals are lower than in mitochondria from young animals.…”

Autophagy and Aging: The Importance of Maintaining "Clean" Cells

“…90,91 Excessively enlarged mitochondria are usually called 'giant'. 90 Senescent mitochondria are defective in ATP production 92 and are reported to produce increased amounts of reactive oxygen species (ROS), 93 which are harmful for cells and nevertheless cannot be eliminated. The mechanisms underlying age-related mitochondrial changes are still debated.…”

Autophagy, organelles and ageing

“…Senescent mitochondria show structural deterioration, such as swelling, loss of cristae and, sometimes, complete destruction of the inner membranes, resulting in the formation of amorphous electron-dense material [54][55][56]. They are often enlarged, sometimes excessively, and thus are called 'giant' mitochondria [54,55].…”

“…Mutations of mtDNA and protein alterations steadily increase with age [57,58]. The proportion of normal mitochondria progressively declines, resulting in diminished respiration and lowered ATP production [54,56].…”