Treating the Metabolic Syndrome by Fecal Transplantation—Current Status

SIMPLE SUMMARY: The term “gut microbiome” refers to the microbial inhabitants whuch populate the intestine, including their number and diversity. In this review, we elaborate on how the microbiome affects the balance of pro- and anti-inflammatory responses in the gut. This ecosystem also influences systemic immunity. An imbalance of the microbiome is implicated in a number of inflammatory conditions, ranging from diabetes and metabolic disorders to non-alcoholic liver disease, cirrhosis, and liver cancer. A high dietary intake of animal-based processed foods and sugar is linked to a gut microbiome containing a higher volume of ‘opportunistic’ bacterial species, including the Firmicutes sp. and Ruminococcus sp., which are involved in pro-inflammatory activity. A diet rich in plant- and fish-based foods is linked to gut microbes that have the opposite effect by enhancing species such as the Faecalibacterium sp., which produce short-chain fatty acids that help control inflammation and protect the cells lining the gut. We also discuss fecal microbiome transplant as a modality to modify intestinal inflammatory processes via the changes in the gut microbiome. ABSTRACT: The intestinal microbiome (IM) is important for normal gastrointestinal (GI) and other organ systems’ functioning. An alteration in the normal IM, dysbiosis, and changes in intestinal motility result in microorganisms’ overgrowth and an alteration in intestinal permeability. The gut–brain axis is also of importance in the irritable bowel syndrome (IBS) and associated bowel overgrowth. Secondary to the epidemic of obesity, the metabolic syndrome has become a major health problem. Disturbances in the fecal microbiome are associated with the metabolic syndrome. Metabolic-associated fatty liver disease (MAFLD) is now the current terminology for non-alcoholic fatty liver disease. IM alteration by fecal transplantation is an approved treatment method for recurrent Clostridioides difficile infection. Initially performed by either duodenal infusion or colonoscopy, it is now easily performed by the administration of capsules containing stools. We discuss the intestinal microbiome—its composition, as well as the qualitative changes of microbiome composition leading to inflammation. In addition, we discuss the evidence of the effect of fecal transplantation on the metabolic syndrome and MAFLD, as well as its clinical indications.