Dietary butyrate treatment enhances healthy metabolites by longitudinal untargeted metabolomic analysis in amyotrophic lateral sclerosis mice

Abstract Microbial metabolites affect the neuron system and muscle cell functions. Amyotrophic Lateral Sclerosis (ALS) is a multifactorial neuromuscular disease. Our previous study has demonstrated elevated intestinal inflammation and dysfunctional microbiome in ALS patients and an ALS mouse model (human-SOD1 G93A transgenic mice). However, the metabolites in ALS progression are unknown. Using an unbiased global metabolomic measurement and targeted measurement, we investigated the longitudinal changes of fecal metabolites in the SOD1 G93A mice over the course of 13 weeks. We compared the changes of metabolites and inflammatory response in age-matched WT and SOD1 G93A mice treated with bacterial product butyrate. We found changes in carbohydrate levels, amino acid metabolism, and formation of gamma-glutamyl amino acids. Shifts in several microbially-contributed catabolites of aromatic amino acids agree with butyrate-induced changes in composition of gut microbiome. Declines in gamma-glutamyl amino acids in feces may stem from differential expression of GGT in response to butyrate administration. Due to signaling nature of amino acid-derived metabolites, these changes indicate changes in inflammation (e.g. histamine) and contribute to differences in systemic levels of neurotransmitters (e.g. GABA, glutamate). Butyrate treatment was able to restore some of the healthy metabolites in ALS mice. Moreover, microglia in the spinal cord were measured by the IBA1 staining. Butyrate treatment significantly suppressed the IBA1 level in the SOD1 G93A mice. The serum IL-17 and LPS were significantly reduced in the butyrate treated SOD1 G93A mice. We have demonstrated an inter-organ communications link among metabolites, inflammation, and ALS progression, suggesting the potential to use metabolites as ALS hallmarks and for treatment. Graphic Abstract We compared the changes of metabolites and inflammatory response in age-matched WT and SOD1 G93A mice treated with bacterial product butyrate. Butyrate treatment was able to restore some of the healthy metabolites in ALS mice. Due to signaling nature of amino acid-derived metabolites, these changes indicate changes in inflammation and contribute to differences in systemic levels of neurotransmitters (e.g. GABA, glutamate). Moreover, butyrate treatment significantly suppressed the microglia IBA1 level and aggregated SOD1 G93A in the SOD1 G93A mice. The inflammatory cytokine, e.g serum IL-17, was significantly reduced in the butyrate treated SOD1 G93A mice. We have demonstrated an inter-organ communications link among metabolites, inflammation, and ALS progression, suggesting the potential to use metabolites as ALS hallmarks and for treatment.