Thomas Dyrmann Leser

Better living through microbial action: the benefits of the mammalian gastrointestinal microbiota on the host.

Mammals live in a homeostatic symbiosis with their gastrointestinal microbiota. The mammalian host provides the microbiota with nutrients and a stable environment; whereas the microbiota helps shaping the hosts gut mucosa and provides nutritional contributions. Microorganisms start colonizing the gut immediately after birth followed by a succession of populations until a stable, adult microbiota has been established. However, physiological conditions differ substantially among locations in the gut and determine bacterial density and diversity. While Firmicutes and Bacteroidetes dominate the gut microbiota in all mammals, the bacterial genera and species diversity is huge and reflects mammalian phylogeny. The main function of the gastrointestinal epithelium is to absorb nutrients and to retain water and electrolytes, yet at the same time it is an efficient barrier against harmful compounds and microorganisms, and is able to neutralize antagonists coincidentally breaching the barrier. These processes are influenced by the microbiota, which modify epithelial expression of genes involved in nutrient uptake and metabolism, mucosal barrier function, xenobiotic metabolism, enteric nervous system and motility, hormonal and maturational responses, angiogenesis, cytoskeleton and extracellular matrix, signal transduction, and general cellular functions. Whereas such effects are local at the gut epithelium they may eventually have systemic consequences, e.g. on body weight and composition.

Quantitation of Pseudomonas sp. strain B13(FR1) in the marine environment by competitive polymerase chain reaction

A method of competitive polymerase chain reaction (cPCR) was developed for quantitation of Pseudomonas sp. strain B13(FR1) released into the marine environment. Following DNA extraction and purification with CTAB (hexadecyltrimethyl ammonium bromide) from seawater inoculated with Pseudomonas sp. strain B13(FR1), a 712 bp fragment (B13-fragment) was co-amplified with a 588 bp internal standard. The internal standard had the same priming sequences as the B13-fragment and was added to calibration standards and samples at a constant concentration. The yield of the two cPCR products was measured on digitized images of Polaroid or X-ray films. The ratio of the two product yields from cPCR was used to make standard curves based on serially diluted DNA extracted from seawater inoculated with Pseudomonas sp. strain B13(FR1). When cPCR products were detected on ethidium bromide stained gels, the ratio of the two fragments was log-linear from 400 cells per cPCR to 4 × 105 cells per cPCR. The log-linear range was extended to 4 cells per cPCR by hybridizing southern blots with a chemiluminescent probe. With the described method Pseudomonas sp. strain B13(FR1) was quantitated in seawater samples inoculated with 0.1 cells ml−1 to 104 cells ml−1.

Dietary Xylo-oligosaccharide stimulates intestinal bifidobacteria and lactobacilli but has limited effect on intestinal integrity in rats

Consumption of prebiotics may modulate gut microbiota, subsequently affecting the bacterial composition, metabolite profile, and human health. Previous studies indicate that also changes in intestinal integrity may occur. In order to explore this further we have investigated the effect of the putative prebiotic xylo-oligosaccharides (XOS) on the gut microbiota and intestinal integrity in male Wistar rats. As changes in intestinal integrity may be related to the expected bifidogenic effect of XOS, we additionally addressed effects of supplementation with a commensal Bifidobacterium pseudolongum (BIF) isolated from the same breed of laboratory rats. Changes in faecal and caecal bacterial composition determined by 16S rRNA gene sequencing and quantitative PCR for selected bacterial groups revealed that the overall bacterial composition did not differ markedly between the control (CON), XOS, and BIF groups, when correcting for multiple comparisons. However as hypothesised, the relative abundance of Bifidobacterium spp. was increased in XOS-fed rats as compared to CON in faecal samples after the intervention. Also Lactobacillus spp. was increased in both the XOS and BIF groups in caecum content compared to CON. Intestinal permeability determined in vivo by FITC-dextran permeability and in vitro using extracted caecum water in trans-epithelial resistance (TER) assay showed no effect on intestinal integrity in either the XOS or the BIF groups. However, the expression of occludin, which is part of the tight junction complex, was increased in the XOS group compared to the CON group. Supplementation with XOS or a commensal Bifidobacterium pseudolongum had very limited effects on intestinal integrity in rats as only significant change in expression of a single tight junction protein gene was found for the XOS group.BackgroundConsumption of prebiotics may modulate gut microbiota, subsequently affecting the bacterial composition, metabolite profile, and human health. Previous studies indicate that also changes in intestinal integrity may occur. In order to explore this further we have investigated the effect of the putative prebiotic xylo-oligosaccharides (XOS) on the gut microbiota and intestinal integrity in male Wistar rats. As changes in intestinal integrity may be related to the expected bifidogenic effect of XOS, we additionally addressed effects of supplementation with a commensal Bifidobacterium pseudolongum (BIF) isolated from the same breed of laboratory rats.ResultsChanges in faecal and caecal bacterial composition determined by 16S rRNA gene sequencing and quantitative PCR for selected bacterial groups revealed that the overall bacterial composition did not differ markedly between the control (CON), XOS, and BIF groups, when correcting for multiple comparisons. However as hypothesised, the relative abundance of Bifidobacterium spp. was increased in XOS-fed rats as compared to CON in faecal samples after the intervention. Also Lactobacillus spp. was increased in both the XOS and BIF groups in caecum content compared to CON. Intestinal permeability determined in vivo by FITC-dextran permeability and in vitro using extracted caecum water in trans-epithelial resistance (TER) assay showed no effect on intestinal integrity in either the XOS or the BIF groups. However, the expression of occludin, which is part of the tight junction complex, was increased in the XOS group compared to the CON group.ConclusionsSupplementation with XOS or a commensal Bifidobacterium pseudolongum had very limited effects on intestinal integrity in rats as only significant change in expression of a single tight junction protein gene was found for the XOS group.

Lactobacillus paracasei subsp paracasei L. casei W8 suppresses energy intake acutely.

BACKGROUND Probiotic bacteria have been shown to have various effects on the microbiota; this may also affect appetite and may help promote weight loss and maintenance. OBJECTIVE This study was conducted to investigate the effect of Lactobacillus paracasei subsp paracasei L. casei W8 (L. casei W8) on glucagon-like peptide-1 (GLP-1) responses in an isolated pig intestine, in piglets and postprandially in humans. Additionally, the effect on subjective appetite, ad libitum energy intake, and glucose and insulin responses in humans was investigated. DESIGN Piglets were fed with probiotics for 2 weeks and the effect on glucagon encoding gene (GCG) was investigated. An isolated pig intestine was perfused with L. casei W8 and the GLP-1 response was measured. Twenty-one subjects completed a randomized, controlled, crossover study with three arms. Each participant completed 3 test days testing the effect of low dose (LD) (10(9) CFU), high dose (HD) (10(10) CFU) L. casei W8 or placebo capsule. Subjective appetite was assessed before an ad libitum lunch was served. GLP-1, insulin and glucose concentrations were analyzed. RESULTS Two weeks of treatment of piglets with L. casei W8 resulted in an increase in GCG expression compared to control animals (P<.05). L. casei W8 increased the GLP-1 response in the isolated pig intestine. In humans, L. casei W8 had an overall effect on energy intake (P=0.03), but no effects on subjective appetite sensation, overall glucose and insulin response and on GLP-1 release were observed (P>0.1). CONCLUSION The probiotic bacteria L. casei W8 appears to lower food intake acutely, but the underlying mechanisms are not understood.

Four weeks supplementation with Lactobacillus paracasei subsp. paracasei L. casei W8® shows modest effect on triacylglycerol in young healthy adults.

The microbiota has been shown to have the potential to affect appetite and blood lipids positively in animal studies. We investigated if four weeks supplementation with Lactobacillus paracasei subsp. paracasei L. casei W8® (L. casei W8) had an effect on subjective appetite sensation, ad libitum energy intake, glucagon-like peptide 1 (GLP-1), glucose and insulin response in humans. Secondarily, we explored potential effects on blood lipids, fatty acids and stearoyl-CoA desaturase-1 (SCD1) activity in humans as well as SCD1 expression in piglets given L. casei W8 for two weeks. 64 healthy participants completed the double-blinded, randomised, controlled, parallel four weeks study with supplementation of L. casei W8 (1010 cfu) or placebo capsules. A meal test was conducted before and after the intervention, where subjective appetite, ad libitum energy intake, GLP-1, glucose and insulin response were measured. Additionally fasting blood lipids and fatty acids concentrations were measured. Sixteen piglets were randomised into two groups: L. casei W8 (1010 cfu/day) as top dressing on morning fed or no treatment. After two weeks piglets were sacrificed and tissue from ileum, jejunum and skeletal muscle were sampled for mRNA analyses of SCD1 expression. Compared to placebo, L. casei W8 did not affect appetite, ad libitum energy intake, GLP-1, glucose and insulin response and total, high-density or low-density lipoprotein cholesterol levels after four weeks intervention. Triacylglycerol decreased in the L. casei W8 group compared to placebo at week 4 (P=0.03). The C16:1n-7/C16:0 ratio, reflecting SCD1 activity, tended to decrease when having L. casei W8 (P=0.06) compared to placebo. Muscle SCD1 expression decreased in piglets supplemented with L. casei W8 compared to control. In conclusion, supplementation with L. casei W8 did not affect appetite parameters, glucose or insulin responses; but appear to be able to lower triacylglycerol levels, possibly by reducing its production.