자연주의적 탐구조사(Naturalistic Inquiry)

Gut microbial composition depends on different dietary habits just as health depends on microbial metabolism, but the association of microbiota with different diets in human populations has not yet been shown. In this work, we compared the fecal microbiota of European children (EU) and that of children from a rural African village of Burkina Faso (BF), where the diet, high in fiber content, is similar to that of early human settlements at the time of the birth of agriculture. By using high-throughput 16S rDNA sequencing and biochemical analyses, we found significant differences in gut microbiota between the two groups. BF children showed a significant enrichment in Bacteroidetes and depletion in Firmicutes (P < 0.001), with a unique abundance of bacteria from the genus Prevotella and Xylanibacter, known to contain a set of bacterial genes for cellulose and xylan hydrolysis, completely lacking in the EU children. In addition, we found significantly more short-chain fatty acids (P < 0.001) in BF than in EU children. Also, Enterobacteriaceae (Shigella and Escherichia) were significantly underrepresented in BF than in EU children (P < 0.05). We hypothesize that gut microbiota coevolved with the polysaccharide-rich diet of BF individuals, allowing them to maximize energy intake from fibers while also protecting them from inflammations and noninfectious colonic diseases. This study investigates and compares human intestinal microbiota from children characterized by a modern western diet and a rural diet, indicating the importance of preserving this treasure of microbial diversity from ancient rural communities worldwide.

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Impact of diet in shaping gut microbiota revealed by a comparative study in children from Europe and rural Africa

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The impact of diet in shaping gut microbiota revealed by a comparative study in children from Europe and Rural Africa

Interest has been recently rekindled in short chain fatty acids (SCFAs) with the emergence of prebiotics and probiotics aimed at improving colonic and systemic health Dietary carbohydrates, specifically resistant starches and dietary fiber, are substrates for fermentation that produce SCFAs, primarily acetate, propionate, and butyrate, as end products The rate and amount of SCFA production depends on the species and amounts of microflora present in the colon, the substrate source and gut transit time SCFAs are readily absorbed Butyrate is the major energy source for colonocytes Propionate is largely taken up by the liver Acetate enters the peripheral circulation to be metabolized by peripheral tissues Specific SCFA may reduce the risk of developing gastrointestinal disorders, cancer, and cardiovascular disease Acetate is the principal SCFA in the colon, and after absorption it has been shown to increase cholesterol synthesis However, propionate, a gluconeogenerator, has been shown to inhibit cholesterol synthesis Therefore, substrates that can decrease the acetate: propionate ratio may reduce serum lipids and possibly cardiovascular disease risk Butyrate has been studied for its role in nourishing the colonic mucosa and in the prevention of cancer of the colon, by promoting cell differentiation, cell-cycle arrest and apoptosis of transformed colonocytes; inhibiting the enzyme histone deacetylase and decreasing the transformation of primary to secondary bile acids as a result of colonic acidification Therefore, a greater increase in SCFA production and potentially a greater delivery of SCFA, specifically butyrate, to the distal colon may result in a protective effect Butyrate irrigation (enema) has also been suggested in the treatment of colitis More human studies are now needed, especially, given the diverse nature of carbohydrate substrates and the SCFA patterns resulting from their fermentation Short-term and long-term human studies are particularly required on SCFAs in relation to markers of cancer risk These studies will be key to the success of dietary recommendations to maximize colonic disease prevention

Colonic health: fermentation and short chain fatty acids.

Obesity has recently been linked to the composition of human microbiota and the production of short chain fatty acids (SCFAs). However, these findings rely on experimental studies carried out using rather small and defined groups of volunteers or model animals. Our aim was to evaluate differences within the human intestinal microbiota and fecal SCFA concentration of lean and obese subjects. A total of 98 subjects volunteered to take part in this study. The BMI in kg/m(2) of 30 volunteers was within the lean range, 35 were overweight and 33 were obese. The fecal microbiota was characterized by real-time PCR analyses. With the primers used herein we were able to cover 82.3% (interquartile range of 68.3-91.4%) of the total microbiota detectable with a universal primer. In addition, the concentration of SCFA was evaluated. The total amount of SCFA was higher in the obese subject group (P = 0.024) than in the lean subject group. The proportion of individual SCFA changed in favor of propionate in overweight (P = 0.019) and obese subjects (P = 0.028). The most abundant bacterial groups in faeces of lean and obese subjects belonged to the phyla Firmicutes and Bacteroidetes. The ratio of Firmicutes to Bacteroidetes changed in favor of the Bacteroidetes in overweight (P = 0.001) and obese subjects (P = 0.005). Our results are in line with previous reports suggesting that SCFA metabolism might play a considerable role in obesity. However, our results contradict previous reports with regard to the contribution of various bacterial groups to the development of obesity and this issue remains controversial.

https://onlinelibrary.wiley.com/doi/pdf/10.1038/oby.2009.167

Microbiota and SCFA in Lean and Overweight Healthy Subjects

Effect of rectal infusion of short chain fatty acids in human subjects.

The purpose of this study was to investigate in healthy humans the effect of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) intake, alone or in combination with dL-alpha-tocopherol acetate (vitamin E) supplements on lipid peroxidation. Eighty men were randomly assigned in a double-blind fashion to take daily for 6 wk either menhaden oil (6.26 g, n-3 fatty acids) or olive oil supplements with either vitamin E (900 IU) or its placebo. Antioxidant vitamins, phospholipid composition, malondialdehyde (MDA), and lipid peroxides were measured in the plasma at baseline and week 6. At the same time, breath alkane output was measured. Plasma alpha-tocopherol concentration increased in those receiving vitamin E (P < 0.0001). In those supplemented with n-3 fatty acids, EPA and DHA increased in plasma phospholipids (P < 0.0001) and plasma MDA and lipid peroxides increased (P < 0.001 and P < 0.05, respectively). Breath alkane output did not change significantly and vitamin E intake did not prevent the increase in lipid peroxidation during menhaden oil supplementation. The results demonstrate that supplementing the diet with n-3 fatty acids resulted in an increase in lipid peroxidation, as measured by plasma MDA release and lipid peroxide products, which was not suppressed by vitamin E supplementation.

Lipid peroxidation during n-3 fatty acid and vitamin E supplementation in humans

Background To compare the quality of life, nutritional status, and gastrointestinal profiles of post-Whipple patients and postcholecystectomy patients. Methods A cross-sectional survey of post-Whipple procedure patients and age- and sexmatched postcholecystectomy patients was performed. Quality of life was assessed using six instruments: Time Trade-off Technique, Direct Questioning of Objectives, Gastrointestinal Quality of Life Index, Sickness Impact Profile, Physician Global Assessment, and Visick Scale. A gastrointestinal symptomatology questionnaire was completed. Nutritional status was assessed by weight, the Subjective Global Assessment instrument, and skin anthropometry. Fasting and postprandial serum gastrin, somatostatin, insulin, pancreatic glucagon, enteroglucagon, and pancreatic polypeptide were measured. Results The quality of life and gastrointestinal function of the Whipple patients was excellent and was not significantly different from that of the control subjects. There were no significant differences in gastrointestinal symptomatology although 5 Whipple patients complained of greasy bowel movements, and 1 patient reported difficulty maintaining weight. Despite this, nutritional status was within normal limits in all subjects. Six patients in the Whipple group followed a diabetic diet, 1 required insulin, and 3 required an oral hypoglycemic agent, whereas none of the control subjects were diabetic. There were no significant differences in the mean basal, peak, or integrated postprandial responses of the gut hormones with the exception of pancreatic polypeptide and gastrin (in patients having a standard Whipple procedure only). Conclusion Quality of life and nutritional status are excellent in patients following a Whipple procedure.

Quality of life, nutritional status, and gastrointestinal hormone profile following the Whipple procedure.

Clinical significance of colonic fermentation.

Elemental diets are considered an effective primary treatment for active Crohn's disease. This study examined the hypothesis that improvement occurs because of the presence of amino acids or the low fat content, or both. A randomised, controlled trial was undertaken in 40 patients with active Crohn's disease to evaluate clinical and nutritional outcomes after an amino acid based diet containing 3% fat was given by a feeding tube compared with a peptide based diet containing 33% fat. After three weeks' treatment, clinical remission occurred in 84% of patients who were given the amino acid diet and 75% of patients who received the peptide diet (p = 0.38). Plasma linoleic acid concentration was reduced after the amino acid but not the peptide diet. An increase in total body nitrogen was associated with the magnitude of nutritional depletion before treatment and at six months' follow up, only patients who showed gains in total body nitrogen after enteral nutrition had a sustained clinical remission. This study shows that peptide based high fat diets are as effective as amino acid low fat diets for achieving clinical remission in active Crohn's disease. Improved total body protein stores but not essential fatty acid depletion may be an important indicator of a sustained remission.

https://gut.bmj.com/content/gutjnl/35/6/783.full.pdf

Dawna Royall

Papers

Effect of rectal infusion of short chain fatty acids in human subjects.

Lipid peroxidation during n-3 fatty acid and vitamin E supplementation in humans

Quality of life, nutritional status, and gastrointestinal hormone profile following the Whipple procedure.

Clinical significance of colonic fermentation.

Comparison of amino acid v peptide based enteral diets in active Crohn's disease: clinical and nutritional outcome.