Gut-kidney axis: Dysbiosis and renal disease

According United States renal data system the morbidity rate for chronic kidney disease (CKD) is 2.5 times than patients not affected by CKD and the mortality rate is 144.9 per 1000 persons-years. The gut microbiota is involved in uremic toxins (UTs) production. This fact was demonstrated by experiments in rats, which revealed better survival in CKD rats that were deprived of the gut microbiota. In men, UT levels are low in CKD patients without a colon. Diet may affect the gut microbiota through food additives such as prebiotics, probiotics and post biotics. Conservation processes and food processing may also affect the gut microbiota. Other factors are food quantity and composition. The gut microbiota may be the cause of UTs production and accumulation in the blood. Additionally, there is interplay among different organs such as liver, kidney and gut. Several theories have been formulated to justify the interplay between the metabolic dysfunctions. In particular, the increase of species such as <i>Eggerthelia lenta</i>, <i>Fusobacterium nucleatum</i> and <i>Alistipes shahii</i> leads to an increase of the aromatic amino acids degradation, and secondary bile acids and trimethyamine oxide biosynthesis in the intestine. This fact determines an increase of the levels of UT precursors such as indole, p-cresol, phenol, phenylacetaleyde, benzoic acid and trimethylamine. Recent studies document the following. The human microbiome project revealed that the gut microbiota may play an important role in both human health and diseases, including kidney disease. Recently, several studies have shown a strict correlation between the gut microbiota and CKD. Probiotics, prebiotics and synbiotics are possible therapies. Probiotics are living microorganisms that, consumed in adequate quantities, are beneficial for the patient, and act on the intestinal microbiome equilibrium. <i>Lactobacilli</i> and <i>Bifidobacteria</i> are common examples of probiotics. Prebiotics are generally fibers not absorbed by the gut, representing a selective nutrient for the microbiome already present in the gut, which favors their growth and activity. Inulin, fructo-oligosaccharides and other fibers are examples of prebiotics. The association and synergism between probiotics and prebiotics is symbiotic.