The ankle–brachial index, gastrocnemius mitochondrial respirometry, and walking performance in people with and without peripheral artery disease

Background: Mitochondrial abnormalities exist in lower-extremity
peripheral artery disease (PAD), yet the association of the ankle–brachial
index (ABI) with mitochondrial respiration in gastrocnemius muscle is
unknown. The association of gastrocnemius mitochondrial respiration with
6-minute walk distance in PAD is unknown. This objective of this study was
to describe associations of the ABI with mitochondrial respiratory
function in gastrocnemius muscle biopsies and associations of
gastrocnemius mitochondrial respirometry with 6-minute walk distance in
people with and without PAD. Methods: People with (ABI ⩽ 0.90) and without
(ABI 1.00–1.40) PAD were enrolled. ABI and 6-minute walk distance were
measured. Mitochondrial function of permeabilized myofibers from
gastrocnemius biopsies was measured with high-resolution respirometry.
Results: A total of 30 people with PAD (71.7 years, mean ABI: 0.64) and 68
without PAD (71.8 years, ABI: 1.17) participated. In non-PAD participants,
higher ABI values were associated significantly with better mitochondrial
respiration (Pearson correlation for maximal oxidative phosphorylation
PCI+II: +0.29, p = 0.016). In PAD, the ABI correlated negatively and not
significantly with mitochondrial respiration (Pearson correlation for
PCI+II: –0.17, p = 0.38). In people without PAD, better mitochondrial
respiration was associated with better 6-minute walk distance (Pearson
correlation: +0.51, p < 0.001), but this association was not
present in PAD (Pearson correlation: +0.10, p = 0.59). Conclusions: Major
differences exist between people with and without PAD in the association
of gastrocnemius mitochondrial respiration with ABI and 6-minute walk
distance. Among people without PAD, ABI and walking performance were
positively associated with mitochondrial respiratory function. These
associations were not observed in PAD.