This study investigated the effects of high-fat (HF) diet on parameters of oxidative
stress among muscles with distinct fiber type composition and oxidative capacities.
To accomplish that, male Wistar rats were fed either a low-fat standard chow (SC)
or a HF diet for 8 weeks. Soleus, extensor digitorum longus (EDL), and epitrochlearis
muscles were collected and mitochondrial H2O2 (mtH2O2) emission, palmitate oxidation,
and gene expression and antioxidant system were measured. Chronic HF feeding enhanced
fat oxidation in oxidative and glycolytic muscles. It also caused a significant reduction
in mtH2O2 emission in the EDL muscle, although a tendency towards a reduction was
also found in the soleus and epitrochlearis muscles. In the epitrochlearis, HF diet
increased mRNA expression of the NADPH oxidase complex; however, this muscle also
showed an increase in the expression of antioxidant proteins, suggesting a higher
capacity to generate and buffer ROS. The soleus muscle, despite being highly oxidative,
elicited H2O2 emission rates equivalent to only 20% and 35% of the values obtained
for EDL and epitrochlearis muscles, respectively. Furthermore, the Epi muscle with
the lowest oxidative capacity was the second highest in H2O2 emission. In conclusion,
it appears that intrinsic differences related to the distribution of type I and type
II fibers, rather than oxidative capacity, drove the activity of the anti- and pro-oxidant
systems and determine ROS production in different skeletal muscles. This also suggests
that the impact of potentially deleterious effects of ROS production on skeletal muscle
metabolism/function under lipotoxic conditions is fiber type-specific.