Effects Of Intestinal Microflora Research Articles

Escherichia coli Activate Extraintestinal Antibody Response and Provide Anti-Infective Immunity

The effects of intestinal microflora on extraintestinal immune response by intestinal cytokines and metabolites have been documented, but whether intestinal microbes stimulate serum antibody generation is unknown. Here, serum antibodies against 69 outer membrane proteins of Escherichia coli, a dominant bacterium in the human intestine, are detected in 141 healthy individuals of varying ages. Antibodies against E. coli outer membrane proteins are determined in all serum samples tested, and frequencies of antibodies to five outer membrane proteins (OmpA, OmpX, TsX, HlpA, and FepA) are close to 100%. Serum antibodies against E. coli outer membrane proteins are further validated by Western blot and bacterial pull-down. Moreover, the present study shows that OstA, HlpA, Tsx, NlpB, OmpC, YfcU, and OmpA provide specific immune protection against pathogenic E. coli, while HlpA and OmpA also exhibit cross-protection against Staphylococcus aureus infection. These finding indicate that intestinal E. coli activate extraintestinal antibody responses and provide anti-infective immunity.

Escherichia coli Activate Extraintestinal Antibody Response and Provide Anti-Infective Immunity.

The effects of intestinal microflora on extraintestinal immune response by intestinal cytokines and metabolites have been documented, but whether intestinal microbes stimulate serum antibody generation is unknown. Here, serum antibodies against 69 outer membrane proteins of Escherichia coli, a dominant bacterium in the human intestine, are detected in 141 healthy individuals of varying ages. Antibodies against E. coli outer membrane proteins are determined in all serum samples tested, and frequencies of antibodies to five outer membrane proteins (OmpA, OmpX, TsX, HlpA, and FepA) are close to 100%. Serum antibodies against E. coli outer membrane proteins are further validated by Western blot and bacterial pull-down. Moreover, the present study shows that OstA, HlpA, Tsx, NlpB, OmpC, YfcU, and OmpA provide specific immune protection against pathogenic E. coli, while HlpA and OmpA also exhibit cross-protection against Staphylococcus aureus infection. These finding indicate that intestinal E. coli activate extraintestinal antibody responses and provide anti-infective immunity.

Yeast Surface Display of Escherichia coli Enterotoxin and Its Effects of Intestinal Microflora and Mucosal Immunity.

Enterotoxigenic Escherichia coli (ETEC) is a significant cause of infectious diarrhea in animals. In this study, yeast surface display technology was employed to investigate the effects of ETEC enterotoxin fusion protein on the intestinal flora and mucosal immunity of rats. ETEC estA, estB, and eltAB (heat-labile and heat-stable toxins) were expressed on the surface of yeast. Rats were divided into normal saline, yeast and display yeast groups. Fecal and jejunal content samples were collected on the 7th, 14th, and 21st days. Rats were then fed ETEC for 3days before again collecting these samples. Levels of SIgA, IL-2, IL-4, IFN-γ, and microbial population density and diversity were documented by ELISA, T-RFLP and real-time PCR. The results demonstrated that estA, estB, and eltAB fusion proteins were expressed on the surface of yeast. Following ETEC challenge, levels of SIgA, IL-2, IL-4, IFN-γ, and, the numbers and variety of intestinal microbes were significantly increased in rats receiving display yeast and yeast. These factors were significantly decreased in rats given normal saline and yeast. Our results indicate that display yeast and yeast can increase the number and diversity of intestinal microbes in rats and improve intestinal immune function. After ETEC challenge, the display yeast can better maintain the balance of intestinal bacteria and mucosal immunity.

Effects of Gut Microflora on Pharmacokinetics of Hesperidin: A Study on Non-Antibiotic and Pseudo-Germ-Free Rats

Hesperidin is a biologically active flavanone glycoside occurring abundantly in citrus fruits. In the present study, effects of intestinal microflora on pharmacokinetics of hesperidin were investigated using a pseudo-germ-free rat model treated with antibiotics. After administration of hesperidin to rats, hesperetin, hesperetin glucuronides, and metabolites postulated to be eriodictyol, hemoeriodictyol, and their glucuronides were detected in urine while hesperetin glucuronide was predominantly found in plasma. The plasma concentration–time profile of hesperetin was compared between non-antibiotic-exposed and pseudo-germ-free rats administered this compound. The maximal concentration (C max) values of hesperetin in non-antibiotic-exposed and pseudo-germ-free rats were 0.58 and 0.20 μg/ml, respectively, and area under the curve (AUC) values were 6.3 and 2.8 μg-h/ml, respectively. Thus, systemic exposure as evidenced by AUC and C max was significantly higher in normal compared to pseudo-germ-free rats. Fecal β-glucosidase activities of non-antibiotic-exposed and pseudo-germ-free rats were 0.21 and 0.11 nmol/min/mg, while fecal α-rhamnosidase activities were 0.37 and 0.12 nmol/min/mg, respectively. The rate of hesperidin transformation to hesperetin was 6.9 and 2.9 nmol/min/g in fecal samples in non-antibiotic-exposed and pseudo-germ-free rats, respectively. Taken together, these results showed that pharmacokinetic differences between non-antibiotic-exposed and pseudo-germ-free rats may be attributed to differing hesperidin uptake, as well as alterations in metabolic activities of intestinal flora.

Effects of intestinal microflora on host immune mechanism

Effects of intestinal microflora on host immune mechanism

Effects of Intestinal Microflora and Dietary Phytate on Intestinal Phytase Activity in Germfree and Conventionalized Rats

Germfree and conventionalized rats were fed a basal or 2% phytate diet. On mucosal phytase activity, the intestinal microflora has no marked effect. Dietary phytate decreased phytase activity in mucosal homogenates, but this effect was not clear in the course of purification. In the germfree intestinal mucosa, the electrophoretic pattern showed two peaks of phytase activity which were different in divalent metal ion requirements. One of these purified phytases did not have any alkaline phosphatase activity.

Effects of intestinal microflora and the environment on the development of asthma and allergy.

The aim of previous research into the causes of allergic diseases, including asthma was mostly to identify potential risk factors in the environment. No major risk factors have been identified, however. Over the past 10 years, focus has, therefore, more been directed towards protective factors that could enhance the development of tolerance to allergens which were previously encountered early in life, but are now lost in modern affluent societies. In particular, the role of childhood infections has been discussed, but so far these studies have not been conclusive. Recent epidemiological studies and experimental research suggest that the microbial environment and exposure to microbial products in infancy modifies immune responses and enhances the development of tolerance to ubiquitous allergens. The intestinal microflora may play a particular role in this respect, as it is the major external driving force in the maturation of the immune system after birth, and animal experiments have shown it to be a prerequisite for normal development of oral tolerance. Recent studies have shown differences in the composition of the microflora between healthy and allergic infants in countries with a high and low prevalence of allergies and between healthy and allergic infants within such countries. These differences are apparent within the first week of life and thus precede clinical symptoms. The use of live microorganisms that might be beneficial to health has a long tradition and the safety is well documented. Very recently, several prospective intervention studies, modifying the gut flora from birth have yielded encouraging results and may suggest a new mode of primary prevention of allergy in the future.

Effects of Intestinal Microflora on the Bioavailability of Dietary Quercetin in Adult Mice.

The effects of intestinal microflora on the bioavailability of dietary quercetin in adult mice were studied. The control group was given a casein diet and water ad libitum. The antibiotics-treated group was given a casein diet and water that contained penicillin and streptomycin ad libitum. Fecal beta-glucuronidase activity was significantly greater in the control mice than in the antibiotics-treated mice. The concentrations of quercetin and isorhamnetin, after deconjugation of plasma quercetin metabolites, were significantly greater in the antibiotics-treated mice. The cecal pools of quercetin in the antibiotics-treated mice were significantly greater than those in the control mice. In untreated mice, it may be necessary to reduce the scission of quercetin and quercetin metabolites and greater beta-glucuronidase activity of the microflora might be needed to maintain a higher concentration of plasma quercetin metabolites.

Effects of intestinal bacteria on the development of colonic neoplasm: an experimental study.

Effects of intestinal microflora on the development of colonic neoplasm induced by 1,2-dimethylhydrazine (DMH) were observed using conventionalized and gnotobiotic mouse models. The incidence of colonic adenoma in germ-free mice (IQI/jic) (GF), mice conventionalized after DMH injection (Cvz-post-DMH) and conventionalized mice (Cvz, conventionalized before DMH injection) was 74%, 69% and 58%, respectively. The mean number of adenomas per mouse in the three groups was 2.6, 2.0 and 1.4, respectively. However, the adenoma in Cvz was larger than in GF. The incidence of adenoma in mice mono-associated with Mitsuokella multiacida, Clostridium butyricum, Bifidobacterium longum, Clostridium paraputrificum, Escherichia coli and Lactobacillus acidophilus was 68%, 68%, 63%, 50%, 50% and 30%, respectively. However, the adenoma in the Cl. paraputrificum group and the Cl. butyricum group was larger than in GF. Faecal pH in Cvz and the L. acidophilus group was significantly lower than in GF. The deconjugation rate of faecal bile acids in Cvz, the Cl. paraputrificum group and the Cl. butyricum group was significantly higher than in GF. These findings suggested two different effects of microflora on the development of DMH-induced adenoma: either an inhibition of the incidence of adenoma or a promotion of tumour growth. Effects of L. acidophilus may be mediated by faecal pH and effects of Cl. paraputrificum and Cl. butyricum by deconjugated bile acids.

Pancreatic Enzymes in Germfree and Conventional Rats Fed Chemically Defined, Water-soluble Diet Free from Natural Substrates

The effects of intestinal microflora and chemically defined, liquid diet free from natural substrates (for pancreatic enzymes), on pancreatic function and on fate of pancreatic enzymes, were studied using germfree and conventional rats fed liquid and semipurified solid diets. Histopathological examination of pancreatic sections of rats fed either diet showed that pancreatic acinar cells in all sections were normal. Serum lipase and amylase levels were normal in germfree and conventional rats fed either diet. Lipase and amylase levels in the pancreas were not affected either by germfree status or by diets. Germfree status had no effect on trypsinogen and chymotrypsinogen in the pancreas, whereas feeding of liquid diet resulted in lower activities of these enzymes in both germfree and conventional rats as compared with those fed a semipurified diet. Feeding of liquid diet and presence of microflora were associated with a lower activity of lipase in the contents of cecum and large intestine, and with a decrease in activities of amylase, trypsin and chymotrypsin in small intestine, large intestine and cecum. These results indicate that the pancreatic enzymes undergo a progressive inactivation on entering the small intestine, and subsequently, passing through the entire intestinal tract. Diets without natural substrates and microflora played an important role in inactivation of these enzymes in the intestinal tract. It is concluded that the chemically defined, liquid diet used in this study was nutritionally adequate for germfree and conventional rats as far as normalcy and function of pancreas were concerned.