The role of short-chain fatty acids in spinal cord injury: A systematic review of human and animal evidence

CONTEXT: Spinal cord injury (SCI) disrupts gut microbiota composition, resulting in dysbiosis that can worsen neuroinflammation and impede post-injury recovery. Short-chain fatty acids (SCFA), metabolites produced by the gut microbiome with anti-inflammatory properties, offer a promising avenue for improving recovery and rehabilitation outcomes. OBJECTIVE: We aimed to compile a summary of the human and animal evidence on the potential benefits of SCFA or SCFA - producing bacteria in individuals with SCI. METHODS: Three databases (EMBASE, Medline (Ovid) and Web of Science) were searched from inception until 19 October 2023. No language restrictions were applied. Title and abstract screening, data extraction and risk of bias assessments were done independently by two reviewers. RESULTS: A total of 2492 studies were retrieved, 69 full-text studies were reviewed, and 13 studies were included (11 animal and 2 human). Human studies, which involved participants with chronic SCI, linked gut dysbiosis (a proxy for low SCFA production) and human metabolic profiles, suggesting a potential role for microbiome-targeted interventions even in later stages of injury. Evidence from animal studies, predominantly in acute and sub-acute models of SCI, consistently associated SCFA interventions with improved motor function, reduced tissue damage and favorable changes in inflammatory and oxidative stress markers. Fecal microbiota transplantation and probiotics improved motor function and reduced lesion size in animal models. Gut microbiome modulations through treatments such as melatonin, moxibustion, and intermittent fasting was correlated with improved motor outcomes and increased abundance of SCFA-producing bacteria. CONCLUSIONS: This review highlights the potential of targeting the gut microbiota and SCFAs as therapeutic strategies for SCI recovery. However, despite promising results in animal models, human evidence remains limited.