The review concludes that EGCG inhibits the growth of pathogenic bacteria like Clostridium perfringens, the relative abundance of which has been linked to behavioural disorders and psychological distress.
Moreover, it increases the abundance of ‘healthy’ metabolites Bifidobacterium spp. and Akkermansia spp, which can metabolise essential neurotransmitters which are essential for the proper functioning of the nervous system, directly affecting neural processes.
The authors from Valencia, Spain, conclude: “EGCG demonstrates efficacy in increasing the production of metabolites involved in maintaining epithelial integrity and improving brain function.
"This identifies EGCG as highly promising for complementary treatment in ASD.”
Autism Spectrum Disorder
ASD is a diverse condition characterised by differences in social communication and interaction, as well as restricted and repetitive patterns of behaviour, affecting approximately 1 in 160 children globally.
Many individuals with ASD also experience gastrointestinal symptoms like abdominal pain, diarrhoea, or constipation, which could be linked to alterations in the intestinal microbiota and its metabolism.
Past studies have found that both the composition of the intestinal microbiota and metabolic activities may be altered in individuals with ASD.
Several authors have concluded that disruptions in the microbiota and intestinal microbiome could trigger many of the gastrointestinal issues experienced by children with ASD, as well as exacerbate some of the core symptoms of the disorder.
It has been shown that the intestinal microbiota affects the function and development of the immune, metabolic, and nervous systems via the regulation of intestinal lymphocytes that provide resistance against potential pathogens.
Additionally, the gut-brain axis has been shown to be affected by the intestinal microbiota and its metabolites.
Neurotransmitters produced by certain bacterial genera can impact the nervous system, and pro-inflammatory cytokines can affect the brain's function by altering the blood-brain barrier's permeability.
The disturbance of the gut-brain-microbiota axis is suggested to be involved in the development of ASD symptoms.
The authors of the current review therefore argue that exploring the gut-brain axis is essential, and that polyphenols, as bioactive dietary compounds, show great promise in this regard.
They note: “The development of symptoms related to ASD may be influenced by the disturbance of the gut–brain–microbiota axis caused by changes in the intestinal microbiota…
“Understanding molecular pathogenic mechanisms is crucial for proposing alternative therapies to current medications used therapeutically for autism-related symptoms.”
Prior research reveals polyphenols act in the intestine, reducing inflammation and modulating the microbiota and its metabolites. They also have neuroprotective effects on the brain, exerted after crossing the blood–brain barrier (BBB).
It has also been suggested polyphenols demonstrate sufficient antioxidant and anti-inflammatory capacity to counteract some ASD symptoms.
Their role in dysbiosis has also been described, revealing their ability to regulate and improve the percentages of beneficial microbial species.
Studies have shown the polyphenol EGCG is particularly effective in improving microbial species and increasing the production of metabolites involved in maintaining epithelial integrity.
It has also demonstrated effectiveness in reducing inflammation directly linked to ASD, by influencing specific pro-inflammatory cytokine levels and reducing oxidative stress.
Furthermore, studies have shown that EGCG can modulate the altered metabolic production in ASD by decreasing toxic metabolites such as p-cresol, a uremic toxin produced by certain strains of Clostridium spp., which has negative biological effects and appears to adversely affect the homeostasis of colonic epithelial cells in children with ASD.
The authors conclude: “These factors have an impact on brain function, which could provide significant benefits for children with ASD.”
They do however note that EGCG has limitations in terms of intestinal assimilation and bioavailability but suggest the use of nanotechnology may be effective in overcoming these limitations, as the administration of EGCG in liposomal form could potentially be more effective.
The conclude: “Therefore, a future line of research could be to determine if the efficacy of liposomal ECGC is improved when administered as a complementary treatment for ASD.”
“Liposomal Epigallocatechin-3-Gallate for the Treatment of Intestinal Dysbiosis in Children with Autism Spectrum Disorder: A Comprehensive Review”
Authors: Jose Enrique de la Rubia Ortí, Costanza Moneti, Pilar Serrano-Ballesteros, Gloria Castellano, Raquel Bayona-Babiloni, Ana Belén Carriquí-Suárez, María Motos-Muñoz, Belén Proaño, and María Benlloch.