The Val66Met BDNF Polymorphism and Peripheral Nerve Injury: Enhanced Regeneration in Mouse Met-Carriers Is Not Further Improved With Activity-Dependent Treatment.
Claire E McGregor, Allison M Irwin, Arthur W English
PMID 31068076WHAT IT FOUND
In mice with sciatic nerve injury, Met carriers showed enhanced motor reinnervation without treatment.
Treadmill training helped only non-carriers, and light stimulation in cultured neurons did not help Met carriers. This is animal work and does not change human therapy.
Key findings
01Without treatment, heterozygous Met mice had an injured-to-intact motoneuron ratio of 0.81±0.068, almost twice the 0.45±0.077 ratio in wild-type mice.
02Treadmill training increased motoneuron regeneration 1.72-fold in wild-type mice but showed a 0.62-fold change in heterozygous Met mice.
03Light stimulation increased longest neurite length 1.2-fold in wild-type sensory neurons but not in Met-carrier sensory neurons.
STILL TO COME
How it was doneWhat they found
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What it does not show
The study was done in mice, not in people with peripheral nerve injury, so it cannot show what treatment would do in a clinic. The paper gives sample sizes for some analyses, such as n=5-8 for untreated MUNE, but does not report a total number of mice analysed. Exercise experiments used only female mice, so the treadmill result may not apply equally to males. MUNE power analysis used preliminary data because the method had not previously been performed in mice. The outcomes were axon regeneration, motor unit estimates, and neurite length, not walking, strength, or patient-reported function. The mechanism for better regeneration in untreated Met carriers is unknown, and the Discussion offers possible explanations rather than tested findings.
Declared interests
The article declares no conflicts of interest. The supplied publication types list NIH extramural and non-U.S. government research support, but the text does not state that a sponsor designed, analysed, or wrote the study.
The easy way to misread this
Do not conclude that treadmill training should be withheld from people with peripheral nerve injury because they may carry the Met allele. The study was in mice, and the 0.62-fold change in heterozygous Met mice was not a clinical outcome in humans.