Aberrant enteric neuromuscular system and dysbiosis in amyotrophic lateral sclerosis.

Amyotrophic Lateral Sclerosis is a neuromuscular disease characterized by the progressive death of motor neurons and muscle atrophy. The gastrointestinal symptoms in ALS patients were largely ignored or underestimated. The relationship between the enteric neuromuscular system and microbiome in ALS progression is unknown. We performed longitudinal studies on the enteric neuron system (ENS) and microbiome in the ALS human-SOD1 (Superoxide Dismutase 1) transgenic mice. We treated age-matched wild-type and ALS mice with butyrate or antibiotics to investigate the microbiome and neuromuscular functions. We examined intestinal mobility, microbiome, an ENS marker GFAP (Glial Fibrillary Acidic Protein), a smooth muscle marker (SMMHC, Smooth Muscle Myosin Heavy Chain), and human colonoids. The distribution of human-G93A-SOD1 protein was tested as an indicator of ALS progression. At 2-month-old before ALS onset, SOD1 mice had significantly lower intestinal mobility, decreased grip strength, and reduced time in the rotarod. We observed increased GFAP and decreased SMMHC expression. These changes correlated with consistent increased aggregation of mutated SOD1 in the colon, small intestine, and spinal cord. Butyrate or antibiotics treated SOD1 mice had a significantly longer latency to fall in the rotarod test, reduced SOD1 aggregation, and enhanced enteric neuromuscular function. Feces from 2-month-old SOD1 mice significantly enhanced SOD1 aggregation in human colonoids transfected with a SOD1-GFP plasmid. Longitudinal studies of microbiome data further showed the altered bacterial community related to autoimmunity , inflammation (e.g., ,), and metabolism (e.g., ) at 1- and 2-month-old SOD1 mice, suggesting the early microbial contribution to the pathological changes. We have demonstrated a novel link between the microbiome, hSOD1 aggregation, and intestinal mobility. Dysbiosis occurred at the early stage of the ALS mice before observed mutated-SOD1 aggregation and dysfunction of ENS. Manipulating the microbiome improves the muscle performance of SOD1 mice. We provide insights into the fundamentals of intestinal neuromuscular function and microbiome in ALS.