Smoking may be considered an established risk factor for sporadic ALS

Effects of gender in amyotrophic lateral sclerosis

BACKGROUND

There is evidence that amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND), is more common in men than in women and that gender influences the clinical features of the disease. The causes of this are unknown.

OBJECTIVE

This review examines the gender differences that are found in ALS and postulates reasons for these differences.

METHODS

A literature review of PubMed (with no date limits) was performed to find information about gender differences in the incidence, prevalence, and clinical features of ALS, using the search terms ALS or MND and gender or sex, ALS prevalence, and SOD1 mice and gender. Articles were reviewed for information about gender differences, together with other articles that were already known to the authors.

RESULTS

The incidence and prevalence of ALS are greater in men than in women. This gender difference is seen in large studies that included all ALS patients (sporadic and familial), but is not seen when familial ALS is studied independently. Men predominate in the younger age groups of patients with ALS. Sporadic ALS has different clinical features in men and women, with men having a greater likelihood of onset in the spinal regions, and women tending to have onset in the bulbar region. Gender appears to have no clear effect on survival. In animals with superoxide dismutase 1 (sod1) mutations, sex does affect the clinical course of disease, with earlier onset in males. Possible reasons for the differences in ALS between men and women include different exposures to environmental toxins, different biological responses to exogenous toxins, and possibly underlying differences between the male and female nervous systems and different abilities to repair damage.

CONCLUSIONS

There is a complex interaction between gender and clinical phenotypes in ALS. Understanding the causes of the gender differences could give clues to processes that modify the disease.

Smoking and risk of amyotrophic lateral sclerosis: a pooled analysis of 5 prospective cohorts

BACKGROUND

Cigarette smoking has been proposed as a risk factor for amyotrophic lateral sclerosis (ALS), but epidemiological studies supporting this hypothesis have been small and mostly retrospective.

OBJECTIVE

To prospectively examine the relation between smoking and ALS in 5 well-established large cohorts.

DESIGN

Five prospective cohorts with study-specific follow-up ranging from 7 to 28 years.

SETTING

Academic research.

PATIENTS

Participants in the Nurses' Health Study, the Health Professionals Follow-up Study, the Cancer Prevention Study II Nutrition Cohort, the Multiethnic Cohort, and the National Institutes of Health-AARP (formerly known as the American Association of Retired Persons) Diet and Health Study.

MAIN OUTCOME MEASURES

Amyotrophic lateral sclerosis deaths identified through the National Death Index. In the Nurses' Health Study and the Health Professionals Follow-up Study, confirmed nonfatal incident ALS was also included.

RESULTS

A total of 832 participants with ALS were documented among 562,804 men and 556,276 women. Smokers had a higher risk of ALS than never smokers, with age- and sex-adjusted relative risks of 1.44 (95% confidence interval, 1.23-1.68; P < .001) for former smokers and 1.42 (95% confidence interval, 1.07-1.88; P = .02) for current smokers. Although the risk of ALS was positively associated with pack-years smoked (P < .001), duration of smoking (9% increase for each 10 years of smoking, P = .006), and the number of cigarettes smoked per day (10% increase for each increment of 10 cigarettes smoked per day, P < .001), these associations did not persist when never smokers were excluded. However, among ever smokers, the risk of ALS increased as age at smoking initiation decreased (P = .03).

CONCLUSIONS

Results of this large longitudinal study support the hypothesis that cigarette smoking increases the risk of ALS. The potential importance of age at smoking initiation and the lack of a dose response deserve further investigation.

The cyanobacteria derived toxin Beta-N-methylamino-L-alanine and amyotrophic lateral sclerosis

There is mounting evidence to suggest that environmental factors play a major role in the development of neurodegenerative diseases like ALS (Amyotrophic Lateral Sclerosis). The non-protein amino acid beta-N-methylamino-L-alanine (BMAA) was first associated with the high incidence of Amyotrophic Lateral Sclerosis/Parkinsonism Dementia Complex (ALS/PDC) in Guam, and has been implicated as a potential environmental factor in ALS, Alzheimer’s disease, and other neurodegenerative diseases. BMAA has a number of toxic effects on motor neurons including direct agonist action on NMDA and AMPA receptors, induction of oxidative stress, and depletion of glutathione. As a non-protein amino acid, there is also the strong possibility that BMAA could cause intraneuronal protein misfolding, the hallmark of neurodegeneration. While an animal model for BMAA-induced ALS is lacking, there is substantial evidence to support a link between this toxin and ALS. The ramifications of discovering an environmental trigger for ALS are enormous. In this article, we discuss the history, ecology, pharmacology and clinical ramifications of this ubiquitous, cyanobacteria-derived toxin.

Mutant human β4 subunit identified in amyotrophic lateral sclerosis patients impairs nicotinic receptor function

Recently identified mutations in the genes encoding the neuronal nicotinic ACh receptor (nAChR) subunits in patients affected by sporadic amyotrophic lateral sclerosis (sALS) may represent a factor which enhances disease susceptibility, in particular in association with ambient causes such as cigarette smoking. In this work, we characterize the functional properties of nAChRs containing the β4R349C subunit, the mutation most frequently encountered in sALS patients. The mutation was coexpressed with wild-type α3 or α4 subunits or with mutant α4R487Q subunit, which has been detected in one patient together with β4R349C mutation. None of the functional parameters examined showed differences between α4β4 and α4R487Qβ4 nAChRs. By contrast, β4R349C mutation, independent of the companion α subunit, caused the reduction in potency of both ACh and nicotine, decreased the density of whole-cell current evoked by maximal transmitter concentrations, and altered the kinetics of ACh-evoked whole-cell currents. These data confirm that sALS-associated mutations in nicotinic subunits may markedly perturb cholinergic transmission in individuals bearing the mutations.

Moving toward a predictive and personalized clinical approach in amyotrophic lateral sclerosis: novel developments and future directions in diagnosis, genetics, pathogenesis and therapies

Amyotrophic lateral sclerosis (ALS) is a rare neurodegenerative disease that affects upper and lower motor neurons in the brain and spinal cord, with progressive weakness and atrophy of most muscles in the body and is almost always fatal within 3–5 years. A small proportion of cases are familial, and remarkable achievements have been made during the last years in understanding the genetics of the disease. In spite of this, the basic pathogenic mechanisms underlying the sporadic disease are still poorly understood. There is urgent need for better understanding of the pathogenic processes in order to be able to develop effective treatments. The present review will focus on recent knowledge gained in diagnosis, genetics, pathogenesis and therapies in ALS. Future development of diagnostic technologies integrating genetic, environmental and individual information will enable us to predict a population at risk for ALS. New treatments actually in development will help improve the medical management of ALS patients, taking into consideration individual traits, as genetic background, and pave a way for a more effective personalized diagnostic and treatment approach.

[Research in amyotrophic lateral sclerosis: what is new in 2009?]

This paper, written by French amyotrophic lateral sclerosis (ALS) center experts, presents an update of recent advances in fundamental, epidemiological and clinical research in ALS based on a review of the literature between September 2008 and November 2009. Among other pathophysiological mechanisms, the role of stress of the endoplasmic reticulum and the importance of energetic metabolic disturbances have been underscored. In the field of genetics, research has been advanced through the identification of mutations of the gene FUsed in Sarcoma/Translated in LipoSarcoma (FUS/TLS) in individuals with familial and sporadic ALS. This gene is involved in the regulation of transcription, splicing and RNA transport, and has functional homology to another ALS gene, TARDBP, which suggests that a common mechanism may underlie motor neuron degeneration. A report showed that mice expressing a mutant form of human TDP-43 develop a progressive and fatal neurodegenerative disease reminiscent of both ALS and frontotemporal lobar degeneration with ubiquitin aggregates (FTLD-U), providing a new animal model that may help to better understand the pathophysiology and test new therapeutics. Beside genetic studies, several epidemiologic studies have investigated the role of environmental factors. A recent study suggests that smoking is a risk factor for developing ALS and it is hypothesized that this could occur through lipid peroxidation via formaldehyde exposure. From a neuroprotective perspective, trials with IGF-1, sodium valproate, coenzyme Q or glatiramer acetate have failed to demonstrate any beneficial effect. A study published in 2008 argued that lithium may have a neuroprotective effect in ALS mice and also in patients. However, two preclinical studies failed to replicate the neuroprotective effect of lithium in ALS mice. Therapeutic trials have been performed or are currently ongoing in Europe and North America. Their results have not yet been published.