Effect of sex on lifespan, disease progression, and the response to methionine sulfoximine in the SOD1 G93A mouse model for ALS.

OBJECTIVE: To investigate the role of sex and the role of ammonia and amino acid metabolism, specifically the activity of glutamine synthetase, in survival and disease progression in amyotrophic lateral sclerosis.

METHODS: We tested treatment with methionine sulfoximine (MSO) on the lifespan and neuromuscular ability of male and female SOD1 mice as measured by their ability to maintain their grip on an inverted wire grid. We also tested the effects of castration and ovariectomization on those measurements.

RESULTS: MSO treatment improves the survival of both male and female mice, but the effects are significantly greater on female mice. Saline-treated (control) female mice have delayed neuromuscular degeneration compared with saline-treated male mice, and MSO further delays disease progression in females, to a greater extent than in males. Ovariectomization or castration completely eliminates the effect of the drug on either survival or neuromuscular deterioration.

CONCLUSIONS: Sex is an important factor in disease progression and the response of SOD1 mice to a drug targeting a central enzyme in nitrogen metabolism, with female sex hormones playing a greater role than male sex hormones. Glutamine synthetase, or its reactants and products, therefore plays a role in this disease, and the sex specificity of treatments aimed at this or other metabolic targets may therefore be an important factor in the development of therapies to treat amyotrophic lateral sclerosis.