Neurological deficits in mice with profound biotinidase deficiency are associated with demylination and axonal degeneration

Brain Trauma and the Secondary Cascade in Humans: Review of the Potential Role of Vitamins in Reparative Processes and Functional Outcome

An estimated sixty-nine million people sustain a traumatic brain injury each year. Trauma to the brain causes the primary insult and initiates a secondary biochemical cascade as part of the immune and reparative response to injury. The secondary cascade, although a normal physiological response, may also contribute to ongoing neuroinflammation, oxidative stress and axonal injury, continuing in some cases years after the initial insult. In this review, we explain some of the biochemical mechanisms of the secondary cascade and their potential deleterious effects on healthy neurons including secondary cell death. The second part of the review focuses on the role of micronutrients to neural mechanisms and their potential reparative effects with regards to the secondary cascade after brain injury. The biochemical response to injury, hypermetabolism and excessive renal clearance of nutrients after injury increases the demand for most vitamins. Currently, most research in the area has shown positive outcomes of vitamin supplementation after brain injury, although predominantly in animal (murine) models. There is a pressing need for more research in this area with human participants because vitamin supplementation post-trauma is a potential cost-effective adjunct to other clinical and therapeutic treatments. Importantly, traumatic brain injury should be considered a lifelong process and better evaluated across the lifespan of individuals who experience brain injury.

High Dose Pharmaceutical Grade Biotin (MD1003) Accelerates Differentiation of Murine and Grafted Human Oligodendrocyte Progenitor Cells In Vivo

Accumulating evidences suggest a strong correlation between metabolic changes and neurodegeneration in CNS demyelinating diseases such as multiple sclerosis (MS). Biotin, an essential cofactor for five carboxylases, is expressed by oligodendrocytes and involved in fatty acid synthesis and energy production. The metabolic effect of biotin or high-dose-biotin (MD1003) has been reported on rodent oligodendrocytes in vitro, and in neurodegenerative or demyelinating animal models. However, clinical studies, showed mild or no beneficial effect of MD1003 in amyotrophic lateral sclerosis (ALS) or MS. Here, we took advantage of a mouse model of myelin deficiency to study the effects of MD1003 on the behavior of murine and grafted human oligodendrocytes in vivo. We show that MD1003 increases the number and the differentiation potential of endogenous murine oligodendroglia over time. Moreover, the levels of MD1003 are increased in the plasma and brain of pups born to treated mothers, indicating that MD1003 can pass through the mother's milk. The histological analysis of the grafted animals shows that MD1003 increased proliferation and accelerates differentiation of human oligodendroglia, but without enhancing their myelination potential. These findings provide important insights into the role of MD1003 on murine and human oligodendrocyte maturation/myelination that may explain the mitigated outcome of ALS/MS clinical trials.

Myelin Repair: From Animal Models to Humans

It is widely thought that brain repair does not occur, but myelin regeneration provides clear evidence to the contrary. Spontaneous remyelination may occur after injury or in multiple sclerosis (MS). However, the efficiency of remyelination varies considerably between MS patients and between the lesions of each patient. Myelin repair is essential for optimal functional recovery, so a profound understanding of the cells and mechanisms involved in this process is required for the development of new therapeutic strategies. In this review, we describe how animal models and modern cell tracing and imaging methods have helped to identify the cell types involved in myelin regeneration. In addition to the oligodendrocyte progenitor cells identified in the 1990s as the principal source of remyelinating cells in the central nervous system (CNS), other cell populations, including subventricular zone-derived neural progenitors, Schwann cells, and even spared mature oligodendrocytes, have more recently emerged as potential contributors to CNS remyelination. We will also highlight the conditions known to limit endogenous repair, such as aging, chronic inflammation, and the production of extracellular matrix proteins, and the role of astrocytes and microglia in these processes. Finally, we will present the discrepancies between observations in humans and in rodents, discussing the relationship of findings in experimental models to myelin repair in humans. These considerations are particularly important from a therapeutic standpoint.

Biotin rescues mitochondrial dysfunction and neurotoxicity in a tauopathy model

Mitochondrial and metabolic dysfunction are often implicated in neurological disease, but effective mechanism-based therapies remain elusive. We performed a genome-scale forward genetic screen in a Drosophila model of tauopathy, a class of neurodegenerative disorders characterized by the accumulation of the protein tau, and identified manipulation of the B-vitamin biotin as a potential therapeutic approach in tauopathy. We show that tau transgenic flies have an innate biotin deficiency due to tau-mediated relaxation of chromatin and consequent aberrant expression of multiple biotin-related genes, disrupting both carboxylase and mitochondrial function. Biotin depletion alone causes mitochondrial pathology and neurodegeneration in both flies and human neurons, implicating mitochondrial dysfunction as a mechanism in biotin deficiency. Finally, carboxylase biotin levels are reduced in mammalian tauopathies, including brains of human Alzheimer's disease patients. These results provide insight into pathogenic mechanisms of human biotin deficiency, the resulting effects on neuronal health, and a potential therapeutic pathway in the treatment of tau-mediated neurotoxicity.

High-dose pharmaceutical grade biotin (MD1003) in amyotrophic lateral sclerosis: A pilot study

BACKGROUND

Oligodendrocytes (OGs) provide metabolic support to motor neurons (MNs) and are implicated in the pathophysiology of amyotrophic lateral sclerosis (ALS). MD1003, or high-dose Pharmaceutical grade Biotin (hdPB), may improve disability in progressive multiple sclerosis patients via augmentation of OG or MN energy levels. Here, we assessed the safety and efficacy of MD1003 in ALS patients.

METHODS

This single centre, randomised, double-blind, placebo-controlled trial included patients aged 25-80 years with probable or definite ALS. Patients were assigned (2:1), using a computer-generated randomisation list, to receive oral MD1003 (300 mg/day) or placebo treatment for 24 weeks. The primary outcome, safety, was analysed in all patients who received at least one dose of study drug. This study, registered with ClinicalTrials.gov, NCT03114215, has been completed.

FINDINGS

Between June and December 2016, 30 patients were enrolled (MD1003, n = 20; placebo, n = 10). Baseline characteristics were representative of the ALS population. MD1003 and placebo groups were not well balanced at screening, with the MD1003-treated group having a higher rate of ALSFRS-R decline prior to screening versus placebo (-6·0 IQR [-8·5, -5·0] vs. -5·0 IQR [-5·0, -3·0]) and a predominance of ALS with upper limb onset compared to placebo (35% vs. 10%). MD1003 had a favourable safety profile and was well tolerated. The occurrence of adverse events was similar in both groups (60%). Two deaths occurred in the MD1003 group versus 1 in the placebo group. ALSFRS-R median change from baseline to month 6 was not significantly different between the two groups (p = 0·49); the mean difference between groups was -1·6 (SEM=3·3).

INTERPRETATION

MD1003 treatment was safe and well tolerated. It was not possible to establish MD1003 efficacy in this relatively small study. Given the favourable safety profile of MD1003 and an imbalance between treatment groups favouring placebo, additional, larger studies in ALS are warranted.

FUNDING

MedDay Pharmaceuticals.

Metabolic etiologies in West syndrome

West syndrome (WS) is an early life epileptic encephalopathy associated with infantile spasms, interictal electroencephalography (EEG) abnormalities including high amplitude, disorganized background with multifocal epileptic spikes (hypsarrhythmia), and often neurodevelopmental impairments. Approximately 64% of the patients have structural, metabolic, genetic, or infectious etiologies and, in the rest, the etiology is unknown. Here we review the contribution of etiologies due to various metabolic disorders in the pathology of WS. These may include metabolic errors in organic molecules involved in amino acid and glucose metabolism, fatty acid oxidation, metal metabolism, pyridoxine deficiency or dependency, or acidurias in organelles such as mitochondria and lysosomes. We discuss the biochemical, clinical, and EEG features of these disorders as well as the evidence of how they may be implicated in the pathogenesis and treatment of WS. The early recognition of these etiologies in some cases may permit early interventions that may improve the course of the disease.

Differential gene expression during early development in brains of wildtype and biotinidase-deficient mice

Biotinidase deficiency is an autosomal recessively inherited disorder characterized by neurological and cutaneous abnormalities. Untreated individuals with biotinidase deficiency cannot recycle biotin from biocytin (N-biotinyl-ϵ-lysine), the proteolytic digestion product of protein-bound biotin. Biotin therapy can markedly resolve symptoms, or can prevent the development of symptoms if initiated early. To understand better the pathogenesis of the neurological problems in the disorder in humans, we have compared gene transcription changes during the first week post-birth in the brains of biotinidase-deficient, transgenic, knock-out mice at days 1 and 8 and compared to changes in wildtype mice at the same times. The knockout pups that were not supplemented with unconjugated biotin became symptomatic by day 8 and exhibiting failure to thrive. Wildtype pups remained asymptomatic under the same experimental conditions. We compared all four possible combinations and noted the most significant up- and down-regulated genes in the knockout animals at Day 8 compared to those at Day 1, reflecting the changes in gene expression over the first week of development. These alterations involved neurological development and immunological function pathways and provide some clues to avenues for further research. At this time, these preliminary analyses provide us with limited, but new information. However, with the development of new algorithms and programs examining various mechanisms and pathways in the central nervous system, these analyses may help us to understand better the role of biotinidase and the pathogenesis of biotinidase deficiency.

Detection of biotinidase gene mutations in Turkish patients ascertained by newborn and family screening

The incidence of biotinidase deficiency in Turkey is currently one of the highest in the world. To expand upon the information about the biotinidase gene (BTD) variations in Turkish patients, we conducted a mutation screening in a large series (n = 210) of probands with biotinidase deficiency, using denaturing high-performance liquid chromatography and direct DNA sequencing. The putative effects of novel mutations were predicted by computational program. Twenty-six mutations, including six novels (p.C143F, p.T244I, c.1212-1222del11, c.1320delG, p.V457L, p.G480R) were identified. Nine of the patients were symptomatic at the initial clinical assessment with presentations of seizures, encephalopathy, and lactic acidemia. The most common mutation in this group of symptomatic patients was c.98-104 del7ins3. Among the screened patients, 72 have partial and 134 have profound biotinidase deficiency (BD) of which 106 are homozygous for BTD mutations. The common mutations (p.R157H, p.D444H, c.98-104del7ins3, p.T532M) cumulatively accounted for 72.3% of all the mutant alleles in the Turkish population.

CONCLUSION

The identification of common mutations and hot spot regions of the BTD gene in Turkish patients is important for mutation screening in the Turkish population and helps to ascertain carriers, may have impact on genetic counseling and implementing prevention programs.