Gut microflora composition

Ingested plant metabolites, drugs and other compounds are processed both by the animal and by the microbial flora of the gut. The composition and activities of the gut microflora vary greatly from one animal species to another and have been very extensively reviewed." In true ruminants (sheep, cattle and deer) and in functional ruminants, such as camels and llamas, a mixed population of bacteria,... 

Hydrolyzable tannins are comparatively restricted in the human diet and there are no human metabolic data. Studies in rats have indicated that some 63% of a dose of 1 g/kg commercial tannic acid is excreted unchanged in the feces accompanied by small amounts of gallic acid, pyrogallol, and resorcinol. Plasma after enzymic hydrolysis was found to contain 4-O-methylgallic acid, pyrogallol, and resorcinol. Urine also contained a small amount of gallic acid after enzymic hydrolysis. The most notable observation from this study is the failure of the gut microflora to metabolize the galloylglucoses efficiently, at least at this substantial dose. The viability or composition of the gut microflora was not reported. ... 

Hoey, L., Rowland, I.R., Lloyd, A.S., Clarke, D.B., and Wiseman, H., Influence of soya-based infant formula consumption on isoflavone and gut microflora metabolite concentrations in urine and on faecal microflora composition and metabolic activity in infants and children, Br. J. Nutr, 91, 607, 2004. 

The importance of gut microfloral populations on urine composition has been highlighted by a study in which axenic (germ free) rats were allowed to acclimatize in normal laboratory conditions and their urine biochemical makeup was monitored for 21 days [34]. The combined influence of gut microflora and parasitic infections on urinary metabolite profiles has also been elucidated [35]. 

Unfortunately, the knowledge about the effects of mycotoxin exposure on the human microbiome is still limited and reported studies mainly refer to the role played by intestinal microflora in mycotoxin detoxification in animals. Nonetheless, mycotoxins may actually affect the gut microflora, as some of them exhibit antimicrobial activities in animals. In addition, it has been proven that chronic exposure to low doses of DON may induce a shift towards intestinal aerobic bacteria in pigs. Since the number and composition of intestinal microflora are significantly modified in inflammatory bowel diseases in humans, with an increase in the number of aerobic bacteria and a parallel decrease in the number of anaerobic bacteria, mycotoxin exposure might represent a potential risk factor for chronic intestinal inflammatory diseases. Since data supporting or contrasting these hypothesis are still poor, further studies should be addressed to better understand the role played by mycotoxins in the imbalance of intestinal microflora in humans. 

Wikoff WR, Anfora AT, Liu J et al (2009) Metabolomics analysis reveals large effect of gut microflora on mammalian blood metabolites. Proc Natl Acad Sd USA 106 3698-3703 Yih A, Aisa HA, Maksimov VV et al (2009) Chemical composition and antimicrobial activity of essential oQ from seeds of Anethum graveolens growing in Uzbekistan. Chem Nat Comp 45 280-281... 

Recent molecular studies on the composition of the human gut microflora have largely confirmed the picture of the gut microflora as generated through traditional... 

Such diversity at the species level has also been illustrated in studies using traditional microbiological culture. Focusing on Lactobacillus spp. and Bifidobacterium spp., McCartney et al. (1996) showed that different individuals carry a unique collection of strains and that species and strain diversity differed between individuals. Similarly, Reuter (2001) reviewed the existing evidence on the composition of the Lactobacillus and Bifidobacterium moieties of the gut microflora. Agreeing with other workers, Reuter (2001) described distinct populations of lactobacilli and bifidobacteria within individuals and identified species truly autochthonous to the gut, for example Lactobacillus gasseri, L. reuteri and a non-motile variant of I. ruminis (formally Catenabacterium catenaforme), while different combinations of bifidobacterial strains predominated in different age groups, notably, infants, compared with adult volunteers. 

The development of the intestinal microbiota needs to be characterized to define the composition that helps us to remain healthy. Specific aberrations in the intestinal microflora may predispose to disease. Such aberrations have been identified in allergic disease, including decreased numbers of bifidobacteria and an atypical composition of bifidobacterial microflora. Also, aberrations in Clostridium content and composition have been reported to be important. Similar predisposing factors may also exist in the case of microflora and both inflammatory gut diseases and rotavirus diarrhea. Microflora aberrations have also been reported in rheumatoid arthritis, juvenile chronic arthritis, ankylosing spondylitis, and irritable bowel syndrome patients. A thorough knowledge of the intestinal microflora composition will offer a basis for future probiotic development and the search for new strains for human use. Many diseases and their prevention can be linked to the microflora in the gut. 

Regarding the formation of these isoflavone derivatives, it is extremely interesting that some people are unable to produce equol or that they produce it in very low amounts. In fact, studies report that a third part of the general population cannot form equol. This demonstrates that the breakdown of isoflavones by the microflora in the gut determines the recovery of the compounds, and that the excretion to the urine of equol and other isoflavones derivatives, such as O-DMA, is dependent on the different composition of intestinal microflora. To confuse the issue even more, some researchers report that the production of isoflavone derivatives, such as equol, also depends on diet and gender a high fat/meat content diet increases equol production in women but not in men, which is explained by promotion of the growth or the activity of the bacterial populations responsible for equol production. On the other hand, no age-related differences for isoflavone metabolism have been reported [12, 13],... 

---