# Niacin ameliorates Charcot-Marie-Tooth 4B1 neuropathy without interfering with nerve regeneration

## TL;DR

A new niacin formulation helps reduce nerve damage in a mouse model of CMT4B1 without hindering nerve regeneration.

## Contribution

A novel long-lasting niacin formulation is shown to ameliorate CMT4B1 neuropathy without impairing nerve regeneration.

## Key findings

- Niacin-based treatment improves neurophysiology and reduces fiber degeneration in CMT4B1 mouse models.
- Niacin does not interfere with nerve regeneration despite its effect on Neuregulin type I signaling.
- Mtmr2 knockout mice exhibit impaired nerve regeneration, which is not worsened by niacin treatment.

## Abstract

Charcot-Marie-Tooth (CMT) neuropathies represent a broad and very heterogeneous group of disorders for which no therapies are yet available. Due to the huge genetic heterogeneity, therapeutical approaches that can benefit several forms independently of the unique pathogenetic mechanism have been sought. Niacin, nicotinic acid, is a vitamin used for many decades as anti-dyslipidaemic and anti-cholesterol drug product under the commercial name of Niaspan®, the extended-release formulation of niacin. Of note, niacin can have other effects depending on the dose, formulation and physiology and it has been used to reduce inflammation, to promote angiogenesis and to protect neurons, muscle and axons by boosting nicotinamide adenine dinucleotide (NAD+) levels. Niacin also activates TNF-alpha convertase enzyme (TACE) secretase, which negatively regulates Neuregulin type I-mediated signalling in the peripheral nervous system and myelination. We previously postulated that niacin-mediated TACE activation can be effective in reducing aberrant excessive myelin associated with different CMT forms. Here, we explored efficacy of this strategy by performing a long-term preclinical trial and we provided evidence that a novel niacin-based long-lasting formulation ameliorates neurophysiology and reduces fibre degeneration in a model of Charcot-Marie-Tooth type 4B1 (CMT4B1) neuropathy, characterized by aberrant myelin. We also sought to determine whether this strategy might interfere with nerve regeneration, which is dependent on Neuregulin type I signalling. Surprisingly, we found that the Mtmr2 knockout mice, a model of CMT4B1, have a defect in nerve regeneration and that niacin-based treatment is not detrimental to nerve regeneration.

Cipriani et al. report that a novel long-lasting formulation of niacin (vitamin B3) ameliorates neurophysiology and reduces fibres degeneration in a mouse model of Charcot-Marie-Tooth (CMT) 4B1, a severe demyelinating neuropathy with aberrant myelin. These findings are clinically relevant as fibre degeneration and loss correlate with clinical disability in patients.

graphical abstract