Factors Affecting Metabolic Activity of the Intestinal Microflora

Abstract

1. The metabolic activity of the gastrointestinal microflora can be modified by numerous factors derived from the host, the host's environment, and the flora itself. 2. Marked differences exist in microbial composition and metabolism of the gut floras of different species of animal, and in the degree of colonization of the various regions of the gut. 3. The microbial flora changes with age, particularly in early infancy, and developmental changes in in vivo metabolism attributable to the gut flora have been noted for methylmercury. 4. Gastrointestinal disease can have a profound effect on microbial colonization and metabolism in the upper regions of the human gut. In particular, hypochlorhydria can lead to elevation in bacterial numbers, and nitrite and nitrosamine concentrations in gastric juice. 5. Environmental factors such as drugs (particularly antibiotics), diet, and xenobiotics can modify microbial metabolism and toxicity of foreign compounds. In some cases exposure to xenobiotics (e.g., cyclamate, rutin) results in metabolic adaptation and increased biotransformation of the foreign compound. 6. By their fermentation of dietary residues and endogenous carbohydrates, the gut bacteria produce acids which can lower lumenal pH and, in turn, modify bacterial enzyme activities. However, the changes in activity appear to be enzyme specific, some increasing with pH and others being inversely related to pH of incubation.

Effects of breast feeding on neuropsychological development in a community with methylmercury exposure from seafood

“…In addition, the persistence of methylmercury and the continuing maternal exposure through intake of contaminated food make both pre-and postnatal exposures of babies likely in breastfed children. Infants may not have the capacity to eliminate methylmercury because of the lack of demethylating bacteria in the gut (Rowland, 1988;Rowland et al, 1984). The exact timing of this colonization is unknown, and considerable interindividual variation may exist.…”

Investigations of Hydrazine Cleavage of Eltrombopag in Humans

“…Humans tend to have the highest gut bacterial concentrations (Rowland, 1988), which may explain the higher amounts of eltrombopag cleavage products observed in man (20% of dose) than in rodents (Ͻ10%) after oral administration (CHMP assessment report for Revolade, European Public Assessment Report, 2010, http://www.ema.europa.eu/docs/en_GB/ document_library/EPAR_-_Product_Information/human/001110/ WC500089964.pdf). A single human gut could contain more than 400 bacterial species, the majority of which are anaerobic (Goldin, 1990).…”

Human Milk as a Source of Methylmercury Exposure in Infants.

“…Without taking into account possible differences in susceptibility to methylmercury exposure, the PTWI would then correspond to a milk Weaning-sampling interval (months) Figure 2. Mercury concentration in hair of 12-month-old infants who had been nursed no more than 5 (10,11). Exactly when such bacteria colonize the gut is unknown, and interindividual variation could be considerable.…”

“…According to experimental studies, methylmercury elimination depends on the presence of demethylating bacteria in the gut (10,11). These bacteria tend to become established after weaning and then metabolize methylmercury from the bile into mercuric ions that are eliminated with the feces; unconverted methylmercury is reabsorbed from the gut.…”