The Importance of the Gut-Liver Axis
The Gut-Liver Axis (GLA) is a critically important factor with regards to liver function and the body’s detoxification pathway. More than 70% of the body’s blood supply to the liver is transported to the liver via the portal vein – the main venous outflow of the gut.
In the event that there is compromised integrity of the gut, such as a permeable gut-blood barrier or imbalance of gut bacteria (dysbiosis), there is a direct impact on liver function via the portal vein.
Ultimately, the main, functional border between the liver and the opening of the intestines is the gut barrier. If the integrity of the gut barrier is lost, liver dysfunction can result!
For example, variations in the bacterial species (microbiota) of the gut can increase the permeability of the mucosal lining of the intestinal tract - the ability of substances to leak through this barrier, into the bloodstream. This permeability allows gut bacteria and endotoxins (toxins in cells released when cells are disrupted), to move to an undesirable location in the body. The microbiota by-products are then metabolized and are capable of triggering a pro-inflammatory response in the body. This pro-inflammatory response occurs via both genetics and inflammatory cytokine cascades[i] - cascades of substances secreted by the Immune System.
In fact, there are several types of Chronic Liver Disease (CLD) in which bacterial lipopolysaccharides (endotoxins) are increased in portal vein circulation.[ii] Some researchers have found that a specific type of dysbiosis, Small Intestinal Bacterial Overgrowth (SIBO), can be present in up to 75% of all CLD.[iii] SIBO is characterized by the primary symptoms of nausea, weight loss, diarrhea and anemia. Therefore, efforts to improve the state of one’s microbiome would be of therapeutic value for individuals with CLD.
A small, placebo-controlled pilot study, conducted in 2005 by Belgian researchers, found that liver function improved in individuals with Non-Alcoholic Steatohepatitis (NASH) following an 8-week trial of prebiotic supplementation with oligofructose[iv], a carbohydrate and source of dietary fiber. Prebiotic bacteria are necessary bacteria that serve as a food source for the beneficial (probiotic) bacteria of the microbiome. NASH is a condition that is common in individuals with Metabolic Syndrome conditions, such as Insulin Resistance (cells have become resistant to the effects of insulin) and Hyperlipidemia (a high level of lipids, or fats, circulating in the blood). As two blood markers were evaluated in this study, aspartate aminotransferase (AST) and alanine aminotransferase (ALT), both markers improved in the NASH patients taking the prebiotic supplementation, as compared to those taking a placebo.
In a similar placebo-controlled study conducted in 2012, a prebiotic was combined with a probiotic strain (Bifidobacterium longum), in measuring the effects of ALT in NASH patients.[v] The results demonstrated a reduction in blood levels of ALT, as well as NASH activity.
As the above-noted research demonstrates, restoring normal gut bacterial balance is a critical factor in restoring normal liver function and its detoxification pathway.
*Photo Credit: Tripathi, A., Debelius, J., Brenner, D. A., Karin, M., Loomba, R., Schnabl, B., & Knight, R. (2018). The gut-liver axis and the intersection with the microbiome. Nature Reviews. Gastroenterology & Hepatology, 15(7), 397-411. doi:10.1038/s41575-018-0011-z
[i] Compare, D., Coccoli, P., Rocco, A., Nardone, O., De Maria, S., Cartenì, M., & Nardone, G. (2012). Review: Gut–liver axis: The impact of gut microbiota on non- alcoholic fatty liver disease. Nutrition, Metabolism And Cardiovascular Diseases, 22471-476. doi:10.1016/j.numecd.2012.02.007
[ii] Tilg, H., Cani, P. D., & Mayer, E. A. (2016). Gut microbiome and liver diseases. Gut, 65(12), 2035-2044. doi:10.1136/gutjnl-2016-312729
[iii] Compare, D., Coccoli, P., Rocco, A., Nardone, O., De Maria, S., Cartenì, M., & Nardone, G. (2012). Review: Gut–liver axis: The impact of gut microbiota on non- alcoholic fatty liver disease. Nutrition, Metabolism And Cardiovascular Diseases, 22471-476. doi:10.1016/j.numecd.2012.02.007
[iv] Daubioul, C. A., Horsmans, Y., Lambert, P., Danse, E., & Delzenne, N. M. (2005). Effects of oligofructose on glucose and lipid metabolism in patients with nonalcoholic steatohepatitis: results of a pilot study. European Journal Of Clinical Nutrition, 59(5), 723-726.
[v] Malaguarnera, M., Vacante, M., Antic, T., Giordano, M., Chisari, G., Acquaviva, R., & ... Galvano, F. (2012). Bifidobacterium longum with fructo-oligosaccharides in patients with non-alcoholic steatohepatitis. Digestive Diseases And Sciences, 57(2), 545-553. doi:10.1007/s10620-011-1887-4