ABSTRACT
BACKGROUND: Amyotrophic lateral sclerosis (ALS) is a universally fatal neurodegenerative disease. ALS is determined by gene-environment interactions and improved understanding of these interactions may lead to effective personalised medicine. The role of physical exercise in the development of ALS is currently controversial. METHODS: First, we dissected the exercise-ALS relationship in a series of two-sample Mendelian randomisation (MR) experiments. Next we tested for enrichment of ALS genetic risk within exercise-associated transcriptome changes. Finally, we applied a validated physical activity questionnaire in a small cohort of genetically selected ALS patients. FINDINGS: We present MR evidence supporting a causal relationship between genetic liability to frequent and strenuous leisure-time exercise and ALS using a liberal instrument (multiplicative random effects IVW, p=0.01). Transcriptomic analysis revealed that genes with altered expression in response to acute exercise are enriched with known ALS risk genes (permutation test, p=0.013) including C9ORF72, and with ALS-associated rare variants of uncertain significance. Questionnaire evidence revealed that age of onset is inversely proportional to historical physical activity for C9ORF72-ALS (Cox proportional hazards model, Wald test p=0.007, likelihood ratio test p=0.01, concordance=74%) but not for non-C9ORF72-ALS. Variability in average physical activity was lower in C9ORF72-ALS compared to both non-C9ORF72-ALS (F-test, p=0.002) and neurologically normal controls (F-test, p=0.049) which is consistent with a homogeneous effect of physical activity in all C9ORF72-ALS patients. INTERPRETATION: Our MR approach suggests a positive causal relationship between ALS and physical exercise. Exercise is likely to cause motor neuron injury only in patients with a risk-genotype. Consistent with this we have shown that ALS risk genes are activated in response to exercise. In particular, we propose that G4C2-repeat expansion of C9ORF72 predisposes to exercise-induced ALS. FUNDING: We acknowledge support from the Wellcome Trust (JCK, 216596/Z/19/Z), NIHR (PJS, NF-SI-0617-10077; IS-BRC-1215-20017) and NIH (MPS, CEGS 5P50HG00773504, 1P50HL083800, 1R01HL101388, 1R01-HL122939, S10OD025212, P30DK116074, and UM1HG009442).
Subject(s)
C9orf72 Protein/genetics , Exercise/adverse effects , Gene Expression Profiling/methods , Mendelian Randomization Analysis/methods , Adult , Age of Onset , Aged , Amyotrophic Lateral Sclerosis/genetics , Female , Gene-Environment Interaction , Genetic Association Studies , Genetic Predisposition to Disease , Genotype , Humans , Male , Middle AgedABSTRACT
Neuropathic pain describes a range of unpleasant sensations caused by a lesion or disease of the somatosensory nervous system. The sensations caused by neuropathic pain are debilitating and improved treatment regimens are sought in order to improve the quality of life of patients. One proposed treatment for neuropathic pain is vitamin B12, which is thought to alleviate pain by a number of mechanisms including promoting myelination, increasing nerve regeneration and decreasing ectopic nerve firing. In this paper, the evidence for B12 as a drug treatment for neuropathic pain is reviewed. Twenty four published articles were eligible for inclusion in this systematic review in which a range of treatment regimens were evaluated including both B12 monotherapy and B12 in combination with other vitamins or conventional treatments, such as gabapentinoids. Overall, this systematic review demonstrates that there is currently some evidence for the therapeutic effect of B12 in the treatment of post-herpetic neuralgia (level II evidence) and the treatment of painful peripheral neuropathy (level III evidence).
Subject(s)
Neuralgia/drug therapy , Peripheral Nervous System Diseases/drug therapy , Vitamin B 12/therapeutic use , Clinical Trials as Topic , Humans , Neuralgia/etiology , Observational Studies as Topic , Peripheral Nervous System Diseases/etiology , Treatment OutcomeABSTRACT
PURPOSE: Autonomic dysfunction is a known consequence of chronic and excessive alcohol consumption. The aim of this systematic review was to characterise this phenomenon, describe the frequency at which it occurs and to explore the best management strategies. METHODS: A systematic, computer-based search was conducted using the PubMed database. All studies identified by the search were evaluated independently by at least three authors. For inclusion, studies had to report human subjects consuming ethanol in excess. Case reports and non-original studies were excluded from this review. RESULTS: A total of 55 studies were included in this review. According to cardiovascular reflex tests, 16-73% of chronic alcohol abusers suffer from autonomic dysfunction. The most commonly occurring symptom is erectile dysfunction, whilst other features such as postural dizziness are rare. The most important risk factor for this condition is total lifetime dose of ethanol, although there is mixed evidence supporting the role of other risk factors. The only management strategy currently explored in the literature is abstinence, which appears to lead to significant improvement in autonomic investigations. CONCLUSION: Current literature includes studies of highly heterogeneous populations, consuming differing volumes of alcohol over variable periods of time and utilising a number of different autonomic test batteries and criteria to diagnose autonomic dysfunction. Therefore, further research using homogeneous methods for measuring autonomic dysfunction in the field is needed. Despite this limitation, our review demonstrated that autonomic dysfunction is very common among alcohol abusers.
Subject(s)
Alcohol Drinking/adverse effects , Alcohol Drinking/epidemiology , Alcoholism/epidemiology , Autonomic Nervous System Diseases/epidemiology , Alcohol Drinking/physiopathology , Alcoholism/diagnosis , Alcoholism/physiopathology , Autonomic Nervous System Diseases/diagnosis , Autonomic Nervous System Diseases/physiopathology , Erectile Dysfunction/diagnosis , Erectile Dysfunction/epidemiology , Erectile Dysfunction/physiopathology , Female , Humans , Male , Primary Dysautonomias/diagnosis , Primary Dysautonomias/epidemiology , Primary Dysautonomias/physiopathologyABSTRACT
The primary aim of this systematic review was to establish the prevalence, character, and risk factors of peripheral neuropathy amongst chronic alcohol abusers and to identify the most appropriate management strategies. In this review, possible pathogenetic mechanisms are also discussed. A systematic, computer-based search was conducted using the PubMed database. Data regarding the above parameters were extracted. 87 articles were included in this review, 29 case-control studies, 52 prospective/retrospective cohort studies and 2 randomised control trials, 1 cross sectional study, and 3 population-based studies. The prevalence of peripheral neuropathy amongst chronic alcohol abusers is 46.3% (CI 35.7- 57.3%) when confirmed via nerve conduction studies. Alcohol-related peripheral neuropathy generally presents as a progressive, predominantly sensory axonal length-dependent neuropathy. The most important risk factor for alcohol-related peripheral neuropathy is the total lifetime dose of ethanol, although other risk factors have been identified including genetic, male gender, and type of alcohol consumed. At present, it is unclear what the pathogenetic mechanisms for the development of neuropathy amongst those who chronically abuse alcohol are, and therefore, it is unknown whether it is attributed to the direct toxic effects of ethanol or another currently unidentified factor. There is presently sparse data to support a particular management strategy in alcohol-related peripheral neuropathy, but the limited data available appears to support the use of vitamin supplementation, particularly of B-vitamin regimens inclusive of thiamine.
