Prebiotics attenuate depressive-like behavior, neuroinflammation and synaptic plasticity in Parkinson’s disease by modulating butyrate-producing gut bacteria

Parkinson's disease (PD) remains a challenging disease for treatment, which is usually polypharmacological. In addition to motor symptoms, non-motor symptoms such as depression are present in approximately 40% of patients, contributing to the loss of quality of life. In the last two decades, a growing body of evidence has emerged regarding the involvement of the microbiota-gut-brain axis in both PD and depression. Fructooligosaccharides (FOS) and galactooligosaccharides (GOS) are prebiotic fibers that can be fermented by the gut microbiota, which produce metabolites called short-chain fatty acids (SCFAs), whose effects can contribute to improvement in neurodegenerative and psychiatric conditions. This study analyzed the effects of FOS and GOS administration in a rotenone-induced PD model and demonstrated a relief of motor symptoms and depressive-like behavior, followed by an increase of brain serotonin and its respective receptor (SERT). FOS and GOS treatment also led to an increase in SCFAs-producing gut bacteria with significantly higher levels of serum and brain butyrate. Furthermore, in the intestine, prebiotics reduced the accumulation of α-synuclein, decreased inflammation, and improved the expression of zonula occludens and occludin. FOS and GOS also attenuated the loss of dopaminergic neurons and reduced neuroinflammation by decreasing α-synuclein, IBA-1, GFAP, iNOS, p-NFkB, and IL1-β levels in the substantia nigra and prefrontal cortex. In addition, these prebiotics improved neuroplasticity by promoting the expression of butyrate receptors (GPR43 and GPR109), BDNF, p-CREB, and synaptic protein PSD-95. In conclusion, FOS and GOS administration attenuatted depressive-like behavior, neuroinflammation, and synaptic plasticity in Parkinson's disease by modulating butyrate-producing gut bacteria.