Finding. The chronic metabolic scar of closed-head injury in an Alzheimer mouse is not a dead tricarboxylic acid cycle. It is a late reroute at pyruvate. Moallem, Sullivan, Bachstetter and colleagues feed [U-13C]glucose to APP/PS1 knock-in mice after closed-head injury and read first-turn carbon in cortex and hippocampus. They split age at injury from time after injury: one month post-hit at 7 or 12 months of age, versus eight months post-hit at 12 months of age. The loud result is the eight-month arm. Cortex labels more pyruvate and lactate. Hippocampus labels more glycolysis and loses precursor-product coupling. First-turn TCA-linked labeling is not broadly down. The authors had hypothesized early TCA deficits and a chronic pyruvate-lactate lesion. The chronic half of that hypothesis is what the carbons show.
Why this paper matters
TBI-plus-amyloid papers love "mitochondrial dysfunction" as a fog. This one has a map. If you are writing a PDH, MCT, or lactate-shuttle intervention for late TBI in an AD background, the 13C pattern says start at the pyruvate branch, not at a first-turn TCA blackout. The design also refuses the usual confound: a 12-month-old mouse hit yesterday is not the same object as a mouse hit at 4 months and read at 12.
Their previous CHI paper in this line already had time-dependent mitochondrial dysfunction. Carbon fate did not simply copy that clock. That mismatch is data.
What they actually measured
Oral uniform 13C-glucose, GC-MS isotopologues, two regions, three timing arms. First-turn fate only. The abstract does not print a wild-type chronic comparison as the headline result.
How to read the score
Mid 80s. Region-specific, time-controlled, pyruvate-centered. Confidence is high for the 8-month KI pattern.
Caveats
Isotopologues are not a full flux model. Prior mitochondrial assays are a different paper. Do not drop TCA-targeted ideas forever; first-turn labeling can miss later turns.
What to do with it
If you trace glucose after TBI, add an 8-month arm and report pyruvate/lactate separately from TCA. Pull hippocampal coupling. Do not cite this as proof that chronic TBI mitochondria are fine.