Daily treatment with a 1:1 THC:CBD combination (mimicking Sativex) reduced dystonia and partially reversed metabolic brain changes in R6/2 mice, a genetic model of Huntington's disease, though motor coordination did not improve.
Readers following cannabinoid research for neurodegenerative diseases.
Dystonia markedly reduced and some metabolic brain markers completely reversed by daily THC+CBD treatment
What the researchers found
R6/2 mice (a transgenic model of Huntington's disease) were treated daily with a Sativex-like phytocannabinoid combination (3 mg/kg each of CBD and THC) starting at 4 weeks of age, when motor symptoms typically begin.
The treatment did not improve rotarod performance (a measure of motor coordination that deteriorates from week 6 to 10 in these mice). However, it markedly attenuated clasping behavior, a measure of dystonia (involuntary muscle contractions).
PET imaging at 10 weeks showed reduced metabolic activity in the basal ganglia of R6/2 mice, which was partially attenuated by the cannabinoid treatment. MRS analysis at 12 weeks revealed multiple metabolic abnormalities reflecting energy failure, mitochondrial dysfunction, and excitotoxicity. Some of these changes (taurine/creatine, taurine/NAA, and NAA/choline ratios) were completely reversed by the cannabinoid treatment.
Why it matters
Huntington's disease has no disease-modifying treatment. While this cannabinoid combination did not reverse the motor deficits, the improvement in dystonia and reversal of metabolic brain changes suggest partial neuroprotective effects that warrant further investigation.
The numbers in context
Dose: 3 mg/kg each CBD + THC daily. Treatment started at 4 weeks. Clasping behavior: markedly attenuated. Rotarod: no improvement. Basal ganglia metabolism: partially preserved on PET. Taurine/creatine, taurine/NAA, NAA/choline ratios: completely reversed.
How the study worked
R6/2 transgenic mice (Huntington's disease model) and wild-type controls received daily treatment with Sativex-like phytocannabinoid combination or vehicle from week 4. Assessment included behavioral testing, in vivo PET imaging, and ex vivo proton MRS spectroscopy of the striatum.
What this study cannot tell us
Mouse model: R6/2 mice develop severe disease very rapidly (weeks), unlike human Huntington's which progresses over decades. Only one dose and ratio were tested. The motor coordination deficits (rotarod) did not improve, which is the most clinically relevant motor outcome. The metabolic improvements may not translate to functional clinical benefit.
How to read the evidence
Preliminary evidence from a single animal study in a genetic disease model.
When this study was published
Published in 2017. Preclinical Huntington's disease research.
The bigger picture
Previous studies showed promising neuroprotective effects of cannabinoids in neurotoxin-based models of Huntington's, but those are simpler models. Testing in the R6/2 genetic model, which better represents the human disease, yielded more modest but still encouraging results. The selective improvement in dystonia without motor coordination improvement suggests cannabinoids may target specific aspects of Huntington's pathology.
Questions still open
- Would higher doses or different CBD:THC ratios produce better motor outcomes? Does the metabolic protection seen on MRS translate to slower disease progression? Could Sativex be tested in human Huntington's patients for dystonia?
Common questions
Can cannabis help with Huntington's disease?
What is Sativex and how was it used in this study?
Read the original research
Effects of a Sativex-Like Combination of Phytocannabinoids on Disease Progression in R6/2 Mice, an Experimental Model of Huntington's Disease.
International journal of molecular sciences, 18(4)
Citation
Valdeolivas, Sara; Sagredo, Onintza; Delgado, Mercedes; Pozo, Miguel A; Fernández-Ruiz, Javier. (2017). Effects of a Sativex-Like Combination of Phytocannabinoids on Disease Progression in R6/2 Mice, an Experimental Model of Huntington's Disease.. International journal of molecular sciences, 18(4). https://doi.org/10.3390/ijms18040684
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