Effect of fructans, prebiotics and fibres on the human gut microbiome assessed by 16S rRNA-based approaches: a review.

The inherent and diverse capacity of dietary fibres, nondigestible oligosaccharides (NDOs) and prebiotics to modify the gut microbiota and markedly influence health status of the host has attracted rising interest. Research and collective initiatives to determine the composition and diversity of the human gut microbiota have increased over the past decade due to great advances in high-throughput technologies, particularly the 16S ribosomal RNA (rRNA) sequencing. Here we reviewed the application of 16S rRNA-based molecular technologies, both community wide (sequencing and phylogenetic microarrays) and targeted methodologies (quantitative PCR, fluorescent in situ hybridisation) to study the effect of chicory inulin-type fructans, NDOs and specific added fibres, such as resistant starches, on the human intestinal microbiota. Overall, such technologies facilitated the monitoring of microbiota shifts due to prebiotic/fibre consumption, though there are limited community-wide sequencing studies so far. Molecular studies confirmed the selective bifidogenic effect of fructans and galactooligosaccharides (GOS) in human intervention studies. Fructans only occasionally decreased relative abundance of Bacteroidetes or stimulated other groups. The sequencing studies for various resistant starches, polydextrose and beta-glucan showed broader effects with more and different types of gut microbial species being enhanced, often including phylotypes of Ruminococcaceae. There was substantial variation in terms of magnitude of response and in individual responses to a specific fibre or NDO which may be due to numerous factors, such as initial presence and relative abundance of a microbial type, diet, genetics of the host, and intervention parameters, such as intervention duration and fibre dose. The field will clearly benefit from a more systematic approach that will support defining the impact of prebiotics and fibres on the gut microbiome, identify biomarkers that link gut microbes to health, and address the personalised response of an individual's microbiota to prebiotics and dietary fibres.

Inflammatory disease processes and interactions with nutrition.

Inflammation is a stereotypical physiological response to infections and tissue injury; it initiates pathogen killing as well as tissue repair processes and helps to restore homeostasis at infected or damaged sites. Acute inflammatory reactions are usually self-limiting and resolve rapidly, due to the involvement of negative feedback mechanisms. Thus, regulated inflammatory responses are essential to remain healthy and maintain homeostasis. However, inflammatory responses that fail to regulate themselves can become chronic and contribute to the perpetuation and progression of disease. Characteristics typical of chronic inflammatory responses underlying the pathophysiology of several disorders include loss of barrier function, responsiveness to a normally benign stimulus, infiltration of inflammatory cells into compartments where they are not normally found in such high numbers, and overproduction of oxidants, cytokines, chemokines, eicosanoids and matrix metalloproteinases. The levels of these mediators amplify the inflammatory response, are destructive and contribute to the clinical symptoms. Various dietary components including long chain omega-3 fatty acids, antioxidant vitamins, plant flavonoids, prebiotics and probiotics have the potential to modulate predisposition to chronic inflammatory conditions and may have a role in their therapy. These components act through a variety of mechanisms including decreasing inflammatory mediator production through effects on cell signaling and gene expression (omega-3 fatty acids, vitamin E, plant flavonoids), reducing the production of damaging oxidants (vitamin E and other antioxidants), and promoting gut barrier function and anti-inflammatory responses (prebiotics and probiotics). However, in general really strong evidence of benefit to human health through anti-inflammatory actions is lacking for most of these dietary components. Thus, further studies addressing efficacy in humans linked to studies providing greater understanding of the mechanisms of action involved are required.

Lipoteichoic acid from Bacillus subtilis subsp. niger WM: isolation and effects on cell wall autolysis and turnover.

Lipoteichoic acid (LTA) was extracted by means of hot aqueous phenol from Bacillus subtilis subsp. niger WM cells grown under various conditions in chemostat culture. The extracts were partially purified by nuclease treatment and gel permeation chromatography. Chemical analyses revealed a composition consistent with a polyglycerol phosphate polymer. The influence on autolysis of the LTAs thus obtained was studied with both whole cells and autolysin-containing native walls of B. subtilis subsp. niger WM. Lysis rates of phosphate-limited cells could be reduced to about 40% of the control rate by the addition of LTA, whereas lysis of cells grown under phosphate-sufficient conditions was affected to a much lesser extent. The lysis of native walls prepared from variously grown cells proved to be fairly insensitive to the addition of LTA. The effect of LTA on wall turnover was studied by following the release of radioactively labeled wall material during exponential growth. The most obvious effect of LTA was a lowered first-order rate of release of labeled wall material; calculations according to the model for cell wall turnover in Bacillus spp. formulated by De Boer et al. (W. R. De Boer, F. J. Kruyssen, and J. T. M. Wouters, J. Bacteriol. 145:50-60, 1981) revealed changes in wall geometry and not in turnover rate in the presence of LTA.

N-acetyl-L-tyrosine as a tyrosine source during total parenteral nutrition in adult rats.

The tyrosine content of parenteral solutions is limited by poor tyrosine solubility. N-acetyl-L-tyrosine has excellent solubility and is a potential source of intravenous tyrosine. Infusion of N-acetyl-U-14C-L-tyrosine as part of a total parenteral nutrition regimen in the rat at a level of 0.5 mmol/kg/day resulted in rapid labeling of tissue tyrosine pools, production of 14CO2, incorporation of 14C-labeled tyrosine into protein, and modest urinary losses (8.3%). Plasma tyrosine levels, however, remained at fasting values (73.8 +/- 5.40 microM). Infusion of N-acetyl-L-tyrosine at 2 mmol/kg/day increased plasma tyrosine above fasting levels (141 +/- 16.1 microM), resulted in a rapid labeling of tissue tyrosine pools, production of 14CO2, and incorporation of 14C-labeled tyrosine into protein. However, urinary losses were higher (16.8%). Rapid utilization of N-acetyl-L-tyrosine was noted at both infusion levels. Plasma- and tissue-free tyrosine pools were rapidly labeled, as was tissue protein. Radioactivity incorporated in tissue protein was shown to be tyrosine after acid hydrolysis.

Cell wall turnover in growing and nongrowing cultures of Bacillus subtilis.

Cell wall turnover was studied in cultures of Bacillus subtilis in which growth was inhibited by nutrient starvation or by the addition of antibiotics. Concomitantly, the synthesis of wall, as measured by the incorporation of radioactively labeled N-acetylglucosamine, was followed in some of these cultures. In potassium- or phosphate-starved cultures, growth stopped, but wall turnover continued at a rate slightly lower than that in the control cultures. Lysis of cells did not occur. In glucose-starved cultures, continued wall turnover caused lysis of cells, since wall synthesis apparently was inhibited. The same phenomenon was observed after growth arrest by the addition of wall synthesis inhibitors such as fosfomycin, cycloserine, penicillin G, and vancomycin. Growth arrest by the addition of chloramphenicol allowed the continuation of wall synthesis; therefore, the observed turnover generally did not cause cell lysis.

[Three new cases of pulmonary fibrosis in finishers of tools reinforced with tungsten carbide (author's transl)]. / A propos de trois nouveaux cas de fibrose pulmonaire chez des affûteurs d'outils renforcés au carbure de tungsténe.

On the basis of three new cases of pulmonary fibrosis due to heavy metals, the authors review the various clinical, radiological and respiratory function test criteria which lead to the diagnosis of this type of occupational fibrosis. This is an uncommon disease (21 cases published up to the present in France), insufficiently known, but with significant and sometimes severe risks. On July 19th 1980, the disease was added to the list of occupational diseases with No 70.

The effects of a high-fiber diet on bile acid pool size, bile acid kinetics, and biliary lipid secretory rates in the morbidly obese.

A high-fiber diet has been suggested as one reason for the low incidence of gallstones in some populations. Therefore the authors tested the effects of a high-fiber diet on biliary secretory kinetics and bile salt kinetics in morbidly obese volunteers. Bile salt pool sizes were reduced by 50%, and their half-lives were decreased 70% after the subjects had spent 6 weeks on the high-fiber diet. Bile acid enterohepatic circulation times also were shortened dramatically. However, the lithogenicity of bile did not decrease, and bile remained supersaturated with with cholesterol. Fasting bile samples tended to be even more lithogenic than before the subjects follwed the diet. In these obese subjects, a high-fiber diet failed to reduce the tendency to secrete cholesterol-saturated bile.

Effects of cholesterol gallstone induction on gallbladder function and bile salt pool size in the prairie dog model.

The prairie dog gallstone model was used to test the following hypotheses: (1) gallbladder stasis occurs in association with gallstone formation, and (2) bile salt pool size decreases as gallstones develop. Bile salt pool sizes and the extent of equilibration of hepatic and gallbladder bile salt over the course of gallstone development were measured. No evidence for bile salt pool reduction was found, but there was significant evidence of progressively inefficient equilibration of hepatic and gallbladder bile salt very early during gallstone formation. These changes, suggestive of gallbladder stasis and observed only in the presence of cholesterol crystals in bile, persisted as cholesterol stones developed and antedated any reduction in bile salt pool size.

[Clinical, functional and hemodynamic course in patients with chronic bronchitis at the stage of chronic cor pulmonale]. / Evolution clinique, fonctionnelle et hémodynamique de bronchiteux chroniques au stade du "coeur pulmonaire chronique"

Twenty seven patients, almost all chronic bronchitic, and with a "chronic cor pulmonale" according to the E. C. G., were followed clinically, radiologically and for E. C. G. and pulmonary functions, and also for the hemodynamics, during a minimum of 3 years, the average length of observation period being about 5 years. Twelve patients died during this observation time. Periods of right heart failure (R. H. F.) were frequent : 3.6 +/- 3.0 in average, slightly more frequent in the deceased patients than in the others. The average delay between the onset R. H. F. and death was of 49.3 +/- 30.8 months ; the survivors on average lived another 54.6 +/- 30.8 months after their first R. H. F. The mean pulmonary arterial pressure (PAP) was quite stable, going from 27.5 +/- 7.0 to 31.2 +/- 9.6 torr (an unsignificicant difference); in only 9 cases did the PAP increase of more than 5 torr during the observation period (acute attacks excepted). The PAP evolution was not significantly different in the deceased and the survivors. PAP worsening by steps after a fit of R. H. F. was observed in only 4 cases. Chronological variations of PAP were well correlated with those of Pao2 during the same period : r = -- 0.68, P less than 0.001. The hemodynamic evolution (PAP), that of the E. C. G. and the volume of the heart were reasonably parallel to the overall clinical evolution ; the E. C. G. evolution had the closest match with the overall clinical evolution (78% of cases). The E. C. G. enables only a late diagnosis of CCP but its evolution is very valuable for prognosis. Hemodynamic tests have a double value initially for diagnosis and later for the evolution.

[Value of pulmonary hemodynamic exploration during muscular exercise in chronic bronchitis?]. / Que peut apporter l'exploration hémodynamique pulmonaire au cours de l'exercice musculaire dans la bronchite chronique

The value of pulmonary haemodynamic tests during physical exercise in chronic bronchitis was shown by the comparison of two groups of patients. In the first group (n=24) the PAP during exercise is lower than 30 torr. In the second it was over 30 torr. The PAP at rest was always lower than 20 torr. The load was 40 to 50 watts, i.e. an average O2 consumption of 500-600 ml.mm-1 m-2. The cardiac output doubled on average in exercise. Both groups varied markedly in their PAP at rest: 13.6 +/- 1.7 torr for the first group and 15.8 +/- 2.4 for the second (p less than 0.001). In fact differences in pressure during exercise (I=25.0 +/- 3.4 torr; II=39.6 +/- 7.4 torr, p less than 0.001) could be explained mainly by the differences of pulmonary vascular resistances (I=0.91 +/- 0.37; II=1.47 +/- 0.61, p less than 0.005): they tended to fall during effort in the first group and increased slightly in the second; and by the much higher increase in the pulmonary "capillary" pressure during exercise in the second group (I=12.5 +/- 4.4 torr; II=19.7 +/- 72 torr, p less than 0.001). The cardiac output during rest and exercise was equal in both groups. The haemo-dynamic "recovery delay" was much higher in the second group. The spirographic shortage was on the whole identical in both groups. PaO2 on average was higher in group I (p less than 0.05) where it improved during exercise (p less than 0.01). The PaO2 of the second group did improve during exercise. The haemodynamic differences were concomitant with the differences in gas exchanges during effort, of well known prognostic significance. As the "foretelling" of PAP in effort from the PAP at rest was quite poor, it appeared that haemodynamic test in effort has a real value in contributing efficiently to the differenciation of the degree in severeness. The threshold of 30 torr for PAP in exercise (and for the load mentioned above) seemed a good discriminating factor.

[Value of specific IgE levels in the etiological diagnosis of asthma]. / Intérêt du dosage des IgE spécifiques dans le diagnostic etiologique de l'asthme

The authors report a study of skin and inhalation tests and of specific IgE in 76 control subjects and 180 patients with allergic asthma. There is a remarkable correlation between the skin tests and the R.A.S.T. in pollinosis (96% of correlation) and in the respiratory allergy to Dermatrophagoides pteronyssinus (120 patients and 87.5% of correlation). It is good in the allergy to animal dander (82% of correlation) but poorer in the respiratory allergy to house dust (62% of correlation). The comparative study of inhalation tests and R.A.S.T. confirms that the degree of correlation depends on the quality of the allergens and on the patients selection. With the extract of house dust (101 cases) the correlation is only of 61.9%, whereas it reaches 95% with a purified extract of Dermatophagoides pteronyssinus (38 cases). The comparison between the treshold of allergenic sensitivity and the group of R.A.S.T. shows that to one group of high R.A.S.T. usually corresponds a low treshold of bronchial sensitivity (D.L.A.L. less than 100 gamma of extract of D. pt. in 22 patients having a R.A.S.T.D. pt. of group 3 or 4). Besides being valuable in characterizing allergens, the R.A.S.T. when confronted to the case history, to skin and inhalation tests, provides supplementary information leading to a more precise allergological diagnosis. In respiratory allergies caused by well known allergens (pollen, Dermatophagoides pteronyssinus), the R.A.S.T. could be substituted to skin and inhalation tests, when in agreement with clinical data. In doubtful cases, the inhalation tests would still keep their value and the confrontation of different techniques is necessary.

Metabolic effects of amino acid vs dextrose infusion in surgical patients.

We tested the hypothesis that during infusion of amino acids without dextrose, there is less insulin stimulation, which, in turn, permits lipolysis. The results suggest that dextrose infusion stimulates insulin and inhibits lipolysis. During administration of crystalline amino acids without dextrose, nitrogen balance improved substantially from control values obtained during dextrose infusion, while the level of serum-free fatty acids and ketone bodies rose and that of serum immunoreactive insulin fell. Infusion of amino acids at 1.7 gm/kg appeared slightly more efficient than infusion at 1.0 gm/kg and did not stimulate insulin or inhibit lipolysis. Protein sparing may be useful in certain specific clinical situations. However, the results must be interpreted cautiously, primarily because it is difficult to establish the relationship between improvement in nitrogen balance and the derived clinical benefit. Absolute proof of the efficacy of this technique awaits further studies using indexes that more accurately measure protein synthesis.

Analysis of gallbladder bile in morbid obesity.

Thirty-seven per cent of our grossly obese patients selected for gastric bypass had cholesterol gallstones. To document the composition of the biliary lipids prior to weight loss, the bile taken from eleven obese patients at the time of gastric bypass was analyzed and the results compared with those in eleven nonobese patients undergoing elective surgery. There was extreme supersaturation of both gallbladder and hepatic bile in all obese patients. The gallbladder bile of all obese patients fell well outside the micellar zone whereas the bile from all but one of the controls fell within the micellar zone. These data provide biochemical support for the clinical association of obesity and cholesterol gallstone formation and are evidence against the possibility that gastric bypass is a lithogenic operation.