Evidence for the mitochondrial lactate oxidation complex in rat neurons: demonstration of an essential component of brain lactate shuttles.
Level 5 - mechanism / opinion, no new human data
Animal tissue and in vitro basic science study
PubMed 18698340 · doi:10.1371/journal.pone.0002915
What was done
Researchers investigated whether monocarboxylate transporters (MCT1, MCT2) and lactate dehydrogenase (LDH) are present in neuronal mitochondria to support an intracellular lactate shuttle. Using rat brain tissue slices (cortical, hippocampal, and thalamic regions) and primary cortical and hippocampal neuronal cultures, they assessed protein colocalization with the mitochondrial inner membrane marker cytochrome oxidase (COX) via immunohistochemistry. They also performed immunoprecipitation and immunoblotting on isolated mitochondrial fractions to evaluate physical association with COX.
What was found
MCT1, MCT2, and LDH colocalized with COX in cortical, hippocampal, and thalamic neurons in brain sections. In primary neuronal cultures, MCT2 and LDH were coexpressed in mitochondria. Immunoprecipitation of COX resulted in coprecipitation of MCT1, MCT2, and LDH from brain homogenate mitochondria and cultured neurons. No quantitative metrics or effect sizes were reported in the abstract.
Why it matters
These findings provide physical evidence that neurons harbor a mitochondrial lactate oxidation complex, supporting the concept that neurons can directly metabolize lactate via intracellular and intercellular lactate shuttles.
Limits
The abstract reports only qualitative structural and biochemical colocalization without functional metabolic flux measurements or kinetic data. The work is entirely preclinical in rodent tissue and cell cultures, and specific sample sizes (number of animals or independent cell preparations) are not stated.
Cited by
- supports Neurons possess all the intact molecular apparatus necessary to take up glucose and produce lactate.