Abstract:
The cheetah is considered the fastest land animal, but studies on their
skeletal muscle properties are scarce. Vastus lateralis biopsies,
obtained from male and female cheetahs as well as humans, were
analysed and compared for fibre type and size, and metabolism.
Overall, cheetah muscle had predominantly type IIX fibres, which was
confirmed by the myosin heavy chain isoform content (mean±s.d. type
I: 17±8%, type IIA: 21±6%, type IIX: 62±12%), whereas humanmuscle
contained predominantly type I and IIA fibres (type I: 49±14%, type IIA:
43±8%, type IIX: 7±7%). Cheetahs had smaller fibres than humans,
with larger fibres in the males compared with their female counterparts.
Citrate synthase (16±6 versus 28±7 μmol min−1 g−1 protein, P<0.05)
and 3-hydroxyacyl co-enzyme A dehydrogenase (30±11 versus 47
±15 μmol min−1 g−1 protein, P<0.05) activities were lower in cheetahs
than in humans, whereas lactate dehydrogenase activity was 6 times
higher in cheetahs (2159±827 versus 382±161 μmolmin−1 g−1 protein,
P<0.001). The activities of creatine kinase (4765±1828 versus 6485
±1298, P<0.05 μmol min−1 g−1 protein) and phosphorylase (111±29
versus 216±92 μmol min−1 g−1 protein) were higher in humans,
irrespective of the higher type IIX fibres in cheetahs. Superoxide
dismutase and catalase,markers of antioxidant capacity, were higher in
humans, but overall antioxidant capacity was higher in cheetahs. To
conclude, fibre type, fibre size andmetabolismdiffer between cheetahs
and humans, with limited differences between the sexes.
