The essentiality of gastrointestinal (GI) butyrate, and the butyrate producing bacterial guild, is unequivocal with respect to systemic health. Non-physiological strategies to increase GI butyrate may be considered, but their impacts are limited holistically. The benefits and limitations of the natural and non-physiological approaches will be discussed.
Butyrate is the most abundantly produced short chain fatty acid (SCFA). It is the primary fuel for colonocytes, but much less so for enterocytes in the small bowel. Butyrate is pivotal in the regulation of the integrity of the mucosal barrier systems, GI inflammation, antineoplastic activity, and the abundance and diversity of the GI microbiota. Systemically, GI butyrate indirectly impacts Cardiometabolic syndrome (CMS) via regulation of satiety, adipocytokine metabolism, insulin release, fatty acid oxidation, oxidative stress, metabolic endotoxemia (LPS), and lipid and lipoprotein metabolism. Greater than 95% of butyrate is rapidly taken by means of carrier mediated transport (MCT1, SMCT1), and the availability of luminal butyrate in distinct segments of the GI tract is highly dependent on its source of origin.
Naturally, butyrate is produced via saccharolytic fermentation of soluble fiber by select commensal bacteria. The most abundant butyrate producers include Faecalibacterium prausnitzii, Roseburia species, and Eubacterium halli and E. rectale. Less abundant species belonging to the Lachnospiraceae family and Firmicutes phyla provide functional redundancy within the butyrate producing guild. Common plant-derived soluble fibers available for microbial fermentation include inulin and inulin-type fructans, fructooligosaccharides, galactooligosaccharides, arabinogalactans, pectin, and partially hydrolyzed guar gum. Highly polymerized fibers are associated with potential for greater butyrate production, and prolonged fermentation towards the distal colon. The soluble fiber “feeding” approach supports greater abundance and diversity within the microbial community, and higher steady state endogenous butyrate production. What about direct provision of exogenous butyrate?
Encapsulated butyrate is entirely absorbed in the stomach and proximal duodenum. That delivery system may provide beneficial effects to the upper GI tract, but would not likely be effective for colonic inflammation or CMS. Some clinical studies suggest that enteric coating may facilitate butyrate delivery to the distal ilium and proximal colon, and symptomatic relief for patients with IBD and IBS-D. However, the reported variable efficacy may be associated with intra-individual differences in transit time and colonic pH.
Some, but not all, studies regarding butyrate enemas have shown short term improvements in clinical and pathological status for patients with IBD, and acutely increased the anti-oxidant capacity of the colonic mucosa for healthy volunteers. Butyrate enemas transiently increase colonic butyrate, but inconvenience and discontinuous delivery of butyrate to the colon raises questions as to long-term efficacy, especially with respect to CMS. Butyrate suppositories may be a better option.
Consider oral tributyrin, because after hydrolysis by gastric and pancreatic lipases, butyrate is available to the small bowel and proximal colon. Porcine research indicates impressive effects of dietary tributyrin on nutrient absorption, insulin release, GI mucosal function and antimicrobial protection. With alcohol abuse, tributyrin has proven therapeutic potential to ameliorate excessive paracellular transport, and hepatic inflammation, damage, and steatosis. The small amount of GI-derived butyrate that appears in portal blood is efficiently cleared by the liver.
The fiber feeding approach is most comprehensive with respect to supporting a healthy GI environment, microbial community, and sustained provision of butyrate and other SCFA. It also has proven beneficial effects towards prevention and amelioration of CMS. The non-physiological strategies provide only butyrate, in a discontinuous manner to restricted segments of the GI tract. As such the latter may be best utilized for short-term, or adjunctive applications for special circumstances.
