parkinsonsnewstoday.com/201...
Nicotinamide a form of B3 and precursor of NAD+ that is essential for energy production in cells mitochondria, failed to produce neuroprotection in a study with PD induced rats that we're treated with Nicotinamide.
"Contrary to the neuroprotection effect in a former study of a fly model of PD parkinsonsnewstoday.com/201... , Nicotinamide treatment in rats enhanced the death of brain cells and structural brain changes. Also, animals treated with a nicotinamide showed increased rate of motor decline and development of behavioral deficits compared to untreated animals."
Even though nicotinamide treatment increased the expression of several neuroprotective genes, it failed to increase neuroprotection; rather, it exacerbated neurodegeneration.
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Other studies have suggested that Nicotinamide may play both a protective and detrimental role in PD ncbi.nlm.nih.gov/pmc/articl... and this differentiation may be dosage related.
"Cultured stem cell–derived neurons respond positively to supplementation with nicotinamide within a dose range of 5 to 10 mM in vitro, but that a 20-mM dose is highly toxic to all neurons" ncbi.nlm.nih.gov/pubmed/242...
Other studies suggest that excess levels of nicotinamide may cause or exacerbate the symptoms of the Parkinson's disease due to the impaired function of NNMT (Nicotinamide N-Methyltransferase), a protein coding gene.
Levels of nicotinamide- NNMT have been shown to be increased in the cerebrospinal fluid ncbi.nlm.nih.gov/pubmed/111... and within specific neuron populations ncbi.nlm.nih.gov/pubmed/127... of patients with PD, suggesting a role in pathogenesis.
Higher NNMT levels have been proposed to cause an increase in conversion of nicotinamide to N-methyl nicotinamide, structurally related to the toxin MPP+, that selectively destroys dopamine neurons. ncbi.nlm.nih.gov/pubmed/156...
In addition, increased NNMT activity leads to lowered mitochondrial complex 1 activity and impaired mitochondrial function, resulting in neurodegeneration. ncbi.nlm.nih.gov/pubmed/225...
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A double-blinded randomized controlled trial is underway, that studies nicotinamide supplementation in early Parkinson's disease. The study involves 200 patients clinicaltrials.gov/ct2/show....
"During this trial the investigators will determine if nicotinamide riboside delays PD disease progression measured by clinical monitoring tools (MDS-UPDRS).
Patients receiving nicotinamide riboside supplementation will receive a daily dose of 1000mg for the duration of the trial. This trial will also collect biological material from participants to see if nicotinamide riboside supplementation rectifies NAD deficiency and metabolism deficiencies."
Possibly there is a fine line, a dose-depended effect of Nicotinamide, able to induce neuroprotection or neurodegeneration in PD. This trial and future human studies may provide further such evidence.