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@alicefrolov.bsky.social Sep 30, 2026, 5:00 PM

"Electron Transport Chain Capacity Erodes Complex-by-Complex with Age"

Subtitle: Simulated OXPHOS complex activity (% of young) across four age groups in skeletal muscle.

#OXPHOS #MitochondrialBioenergetics #Respirometry #MtDNA #SkeletalMuscleMetabolism #ElectronTransportChain #Bioenergetics

"Electron Transport Chain Capacity Erodes Complex-by-Complex with Age"

Subtitle: Simulated OXPHOS complex activity (% of young) across four age groups in skeletal muscle.

I am sharing a radial polar bar representation designed to communicate the differential, non-uniform decline of individual respiratory chain complexes with advancing age. Each angular segment of the "electron transport chain wheel" corresponds to one of the five OXPHOS complexes (CI: NADH:ubiquinone oxidoreductase; CII: succinate dehydrogenase; CIII: cytochrome bc1; CIV: cytochrome c oxidase; CV: F1Fo-ATP synthase), while radial extent encodes activity normalized to a young reference cohort (100%). Four concentric bands stratify the age groups, permitting rapid visual comparison of complex-specific trajectories.

I want to emphasize that the underlying data are simulated. They are not derived from a primary cohort but are parameterized to reproduce trends repeatedly documented in the literature: the disproportionate vulnerability of Complexes I and IV, both of which incorporate mtDNA-encoded subunits and are therefore sensitive to the accumulation of somatic mtDNA deletions and point mutations, clonal expansion of mutant genomes, and impaired mitochondrial proteostasis. Complex II, being entirely nuclear-encoded, is rendered comparatively preserved, consistent with its frequent use as a normalization reference in respirometric and histochemical assays.

The polar geometry was chosen deliberately to foreground the coupled, sequential architecture of the respiratory chain rather than to imply independence between complexes. Declining CI and CIII capacity constrains ubiquinone and cytochrome c redox cycling, with downstream consequences for proton-motive force generation and CV throughput.

I welcome methodological critique, particularly regarding whether polar encoding introduces perceptual distortion of the radial magnitudes relative to a conventional Cartesian layout.

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