Tracing the lactate shuttle to the mitochondrial reticulum.
Level 5 - mechanism / opinion, no new human data
Narrative review of physiological tracer studies and mechanism-based reasoning without systematic methodology.
PubMed 36075947 · doi:10.1038/s12276-022-00802-3
What was done
This narrative review summarizes physiological evidence from isotope tracer infusion studies (using lactate, glucose, glycerol, and fatty acid tracers), tissue metabolite measurements, and arterial-venous difference and blood flow assessments across tissue beds (skeletal muscle, heart, brain) in resting and exercising men and women across various training and altitude states.
What was found
The abstract reports no numerical data or statistical effect sizes. It describes the continuous operation of organ-organ, cell-cell (e.g., between white and red muscle fibers or astrocytes and neurons), and intracellular (cytosol to mitochondria or peroxisomes) lactate shuttles, driven by concentration gradients established by recipient cell mitochondrial respiration.
Why it matters
It synthesizes the paradigm shift demonstrating that lactate acts as a dynamic, oxidizable fuel substrate distributed between producer and consumer tissues rather than merely a dead-end metabolic waste product.
Limits
The abstract provides no quantitative data, sample sizes, or formal systematic search criteria. As a narrative synthesis, it reflects expert mechanism-based reasoning rather than a primary trial or systematic review.
Cited by
- supports Lactate released by active skeletal muscle during exercise is taken up and used as a fuel substrate by other organs, including the heart, liver, and brain.