Ristow et al. [8] reported that vitamin C and E supplementation
in humans blunted mRNA expression of genes associated with
mitochondrial biogenesis and endogenous antioxidant enzymes
following endurance training. However, the findings from this
study have attracted criticism [14], since mRNA responses of mitochondrial
biogenesis markers to endurance exercise are largely
transient, returning to baseline within 24 h of an acute bout of
exercise [20] and should not be considered markers of a trained
state [14]. Nevertheless, Paulsen et al. [10] recently demonstrated
an attenuation of the abundance of the mitochondrial protein COX
IV and the cytosolic (but not whole-muscle) abundance of PGC-1α
in those supplemented daily with 1 g vitamin C and 235 mg vitamin
E. Therefore, some favourable cellular responses to endurance
training appear to be blunted by daily supplementation
with combined 1 g vitamin C and 235 mg vitamin E [10]. Whether
this extends to commonly used markers of mitochondrial content,
such as citrate synthase (CS) and also to antioxidant enzyme activity
remains unclear.