Mitochondrial DNA deletion mutations colocalize with segmental electron transport system abnormalities, muscle fiber atrophy, fiber splitting, and oxidative damage in sarcopenia

Abstract

The in vivo cellular impact of age-associated mitochondrial DNA mutations is unknown. We hypothesized that mitochondrial DNA deletion mutations contribute to the fiber atrophy and loss that cause sarcopenia, the age-related decline of muscle mass and function. We examined 82,713 rectus femoris muscle fibers from Fischer 344 x Brown Norway F1 hybrid rats of ages 5, 18, and 38 months through 1000 microns by serial cryosectioning and histochemical staining for cytochrome c oxidase and succinate dehydrogenase. Between 5 and 38 months of age, the rectus femoris muscle in the hybrid rat demonstrated a 33% decrease in mass concomitant with a 30% decrease in total fibers at the muscle mid-belly. We observed significant increases in the number of mitochondrial abnormalities with age from 289 +/- 8 ETS abnormal fibers in the entire 5-month-old rectus femoris to 1094 +/- 126 in the 38-month-old as calculated from the volume density of these abnormalities. Segmental mitochondrial abnormalities contained mitochondrial DNA deletion mutations as revealed by laser capture microdissection and whole mitochondrial genome amplification. Muscle fibers harboring mitochondrial deletions often displayed atrophy, splitting and increased steady-state levels of oxidative nucleic damage. These data suggest a causal role for age-associated mitochondrial DNA deletion mutations in sarcopenia.

Apoptosis and necrosis mediate skeletal muscle fiber loss in age‐induced mitochondrial enzymatic abnormalities

“…The muscle mass decline observed in sarcopenia is due to fiber atrophy and loss (Lexell et al ., 1986). There are several proposed mechanisms for the decline of muscle mass including altered satellite cell function (Gallegly et al ., 2004), decrease in motor unit number (Roos et al ., 1997), changes in hormone levels (Visser et al ., 2003), accumulation of mitochondrial DNA deletions (Wanagat et al ., 2001), and loss of myocytes via apoptosis (Dupont‐Versteegden, 2005). …”

“…Skeletal muscle from aged rats (Wanagat et al ., 2001), monkeys (Lee et al ., 1993, 1994), and humans (Bua et al ., 2006) displays an increase in the number of fibers exhibiting aberrations in the electron transport chain (ETC). These ETC abnormalities are visualized as loss of COX activity (COX−) as well as succinate dehydrogenase hyperactivity (SDH++) and are both focal (occur in individual cells) and segmental (occur within small regions of an individual cell) (Wanagat et al ., 2001). Electron transport chain‐abnormal regions vary in length with the longer abnormal regions being more prone to fiber atrophy and breakage (Bua et al ., 2004).…”

“…Electron transport chain‐abnormal regions vary in length with the longer abnormal regions being more prone to fiber atrophy and breakage (Bua et al ., 2004). Mitochondrial DNA deletion mutations are concomitant with ETC abnormalities (Lee et al ., 1993, 1994; Müller‐Höcker et al ., 1993; Johnston et al ., 1995; Cao et al ., 2001; Wanagat et al ., 2001). Studies combining microdissection of individual fiber sections with quantitative PCR demonstrate that ETC‐abnormal fibers always have deletion mutation accumulations accompanying them (Cao et al ., 2001; Wanagat et al ., 2001; Gokey et al ., 2004).…”

“…Mitochondrial DNA deletion mutations are concomitant with ETC abnormalities (Lee et al ., 1993, 1994; Müller‐Höcker et al ., 1993; Johnston et al ., 1995; Cao et al ., 2001; Wanagat et al ., 2001). Studies combining microdissection of individual fiber sections with quantitative PCR demonstrate that ETC‐abnormal fibers always have deletion mutation accumulations accompanying them (Cao et al ., 2001; Wanagat et al ., 2001; Gokey et al ., 2004). Further studies showed a high abundance of mtDNA deletion mutations past a threshold value of > 90% resulting in the disruption of the ETC activity (Bua et al ., 2006; Herbst et al ., 2007).…”

Evidence that a mitochondrial death spiral underlies antagonistic pleiotropy

“…Mitochondrial DNA damage increases in aging rodents (Hamilton et al ., 2001; Genova et al ., 2004; Hagen et al ., 2004) and humans (Taylor et al ., 2003), and these increases in mutation can lead to reduced flow through the electron transport chain during aging (Wanagat et al ., 2001; Hagen et al ., 2004; Short et al ., 2005; reviewed in Golden & Melov, 2001; Ikeda et al ., 2014). …”