HoldsUp

George Brooks

George A. Brooks, Ph.D., is a researcher in physiology and metabolism known for developing the lactate shuttle hypothesis. His published research focuses on carbohydrate and lactate kinetics, muscle fuel utilization, and mitochondrial bioenergetics in the context of exercise and aging. He also investigates the potential therapeutic applications of lactate in neurological conditions and metabolic regulation.

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What they said on air - overstated

9 citing their own research

0:48:52overstatedlowtheir own paperGeorge Brooks, Ph.D. on Lactate Shuttle Theory, Relevance fo

When pyruvate is infused intravenously, red blood cells and the lungs convert it to lactate within seconds to a minute in one circulatory passage.

"when you infuse it in one circulatory passage, it's all lactate. So the lungs do that, and red blood cells do that. The red blood cells and the lungs are loaded with enzymes to convert pyruvate to lactate. So even if you want to try to give pyruvate, within seconds or a minute, it's going to be lactate anyway" (said at 0:48:52)

Evidence supports that red blood cells and pulmonary tissue rapidly take up and convert circulating pyruvate to lactate due to high lactate dehydrogenase (LDH) activity and monocarboxylate transporter (MCT) expression. However, claiming that pyruvate is completely converted ("it's all lactate") in a single circulatory passage overstates the magnitude of first-pass pulmonary extraction. In vivo tracer studies in animal models demonstrate a transpulmonary pyruvate fractional extraction of approximately 43% per circulatory transit, rather than complete conversion, though rapid equilibration toward lactate continues across subsequent passages and within erythrocytes.

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