Intramitochondrial inclusions caused by depletion of creatine in rat skeletal muscles.

Abstract

Effect of Creatine depletion by fl-guanidinopropionic acid (/3-GPA) feeding on mitochondrial morphology was studied in rats. Following /3-GPA feeding for 9 weeks, intramitochondrial inclusions running parallel to the long axis of mitochondrion were observed in skeletal muscles. A bundle of inclusions consisted of four parallel arrays containing electron-dense materials. Two outer arrays were continuous with cristal membranes and two inner arrays were chains of fine particles. Mitochondria with such inclusions were elongated probably in only a certain direction even though it was suggested that the layers of cristae were straightened two-dimensionally. Longer mitochondria ran parallel to the muscle fibers. It was also suggested that chronic stimulation of mitochondria) biogenesis by depletion of high energy phosphates may induce such inclusions within mitochondria. inclusions, rat skeletal muscle, j3-It is reported that cold acclimation enlarged the mitochondrial size in rat skeletal muscles (YAHATA and KUROSHIMA, 1977). In these muscles, the mitochondrial cristae and sarcoplasmic reticuli developed better than in the control muscles. Cold acclimation of rats also increased the activity of succinate dehydrogenase in soleus muscle fibers (MATOBA and MURAKAMI, 1981), although the mechanism of morphological and metabolic changes in mitochondria is still unclear. However, our previous study showed that the activity of gastrocnemius oxidative enzymes were elevated when the contents of adenosine triphosphate (ATP) were decreased following the chronic exposure to cold (4°C) In frogs (OHIRA and OHIRA, 1988).

The Effect of the Creatine Analogue Beta-guanidinopropionic Acid on Energy Metabolism: A Systematic Review

“…18.6 (SD 8.9) and 10.2% (SD 10.1) (Figure S1) [23]–[25], [28], [29], [34], [36], [43], [45], [48]–[50], [53], [54], [57], [59], [76], [82]. This apparent shift towards oxidative metabolism was accompanied by a 2-fold increase in mitochondrial DNA [20], and increased mitochondrial density [56], [78], with occasional subsarcolemmal accumulation of enlarged, elongated, or irregular shaped mitochondria, containing paracristalline inclusions [48], [54], [74], [81], [85], [86]. The paracrystalline inclusions, in some studies, were found to be condensed and crystallized mitochondrial CK [54], [86].…”

Metabolic Modulation of Muscle Fiber Properties Unrelated to Mechanical Stimuli

“…However, as noted previously it is clear that these muscle adaptations induced by ␤-GPA feeding were not related to increased muscle activity, since the EMG levels were significantly depressed in these animals. An increase in mitochondrial mass, often associated with intramitochondrial inclusions observed in myopathies has been observed following ␤-GPA feeding [36]. Moerland et al [20] reported that the total oxidative capacity of the EDL in ␤-GPA-fed mice was decreased because of a smaller muscle mass, even though the specific activities (per gram of muscle weight) of mitochondrial enzymes such as cytochrome oxidase and citrate synthase were higher than in controls.…”

Adult rat cardiomyocytes cultured in creatine-deficient medium display large mitochondria with paracrystalline inclusions, enriched for creatine kinase.

“…Intramitochondrial inclusions in skeletal muscle, but not in heart muscle, have been reported in vivo, where rats had been fed with the creatine analogue B-GPA, which is known to cause creatine and phosphocreatine depletion in muscle (31). It was then of interest to test if B-GPA could interfere with the creatine effect in mitochondria of ARC described above, and in some way could restore the standard "creatinefree" culture conditions.…”

“…Although no indication exists as to how directly creatine brings about the effects on the mitochondria, its involvement is clearly demonstrated by experiments, where the creatine analogue/3-GPA reversed the creatine effect by competition in ARC, previously grown in creatine-substituted medium. Ohira et al (31) also had investigated the influence of/3-GPA in vivo on the ultrastructure of mitochondria in skeletal muscle from rabbits previously fed with the drug and observed similar mitochondrial inclusions in skeletal but not in cardiac muscle of animals chronically treated with the drug. Other authors have demonstrated that in vivo feeding of/3-GPA lowers the level of total creatine (creatine plus phosphocreatine) in muscle (26,50), because it inhibits creatine entry into muscle from the blood plasma (14,49).…”

“…Thus, the low intracellular levels of creatine and creatine phosphate would be compensated by the metabolic adaptation via higher total amounts of Mi-CK within the cylindrically shaped large mitochondria, in other words, the cell would respond to its lower phosphocreatine energy status by increasing what we called the "transport function " of the phosphocreatine circuit (60,61) via Mi-CK, representing an "energy chaneling" enzyme (40,41). Since mitochondrial inclusions also occur in/3-GPA-treated animals (31) where phosphocreatine levels in skeletal muscle as low as 10% of normal have been reported (26,49,50), such a metabolic adaptation to increase the energy transport capacity of the phosphocreatine circuit by Mi-CK (60,61) deserves some merit.…”