The effects of inulin-type fructans on cardiovascular disease risk factors: systematic review and meta-analysis of randomized controlled trials

Identification of novel fructo-oligosaccharide bacterial consumers by pulse metatranscriptomics in a human stool sample

Dietary fibers influence the composition of the human gut microbiota and directly contribute to its downstream effects on host health. As more research supports the use of glycans as prebiotics for therapeutic applications, the need to identify the gut bacteria that metabolize glycans of interest increases. Fructo-oligosaccharide (FOS) is a common diet-derived glycan that is fermented by the gut microbiota and has been used as a prebiotic. Despite being well studied, we do not yet have a complete picture of all FOS-consuming gut bacterial taxa. To identify new bacterial consumers, we used a short exposure of microbial communities in a stool sample to FOS or galactomannan as the sole carbon source to induce glycan metabolism genes. We then performed metatranscriptomics, paired with whole metagenomic sequencing, and 16S amplicon sequencing. The short incubation was sufficient to cause induction of genes involved in carbohydrate metabolism, like carbohydrate-active enzymes (CAZymes), including glycoside hydrolase family 32 genes, which hydrolyze fructan polysaccharides like FOS and inulin. Interestingly, FOS metabolism transcripts were notably overexpressed in Blautia species not previously reported to be fructan consumers. We therefore validated the ability of different Blautia species to ferment fructans by monitoring their growth and fermentation in defined media. This pulse metatranscriptomics approach is a useful method to find novel consumers of prebiotics and increase our understanding of prebiotic metabolism by CAZymes in the gut microbiota.

IMPORTANCE

Complex carbohydrates are key contributors to the composition of the human gut microbiota and play an essential role in the microbiota's effects on host health. Understanding which bacteria consume complex carbohydrates, or glycans, provides a mechanistic link between dietary prebiotics and their beneficial health effects, an essential step for their therapeutic application. Here, we used a pulse metatranscriptomics pipeline to identify bacterial consumers based on glycan metabolism induction in a human stool sample. We identified novel consumers of fructo-oligosaccharide among Blautia species, expanding our understanding of this well-known glycan. Our approach can be applied to identify consumers of understudied glycans and expand our prebiotic repertoire. It can also be used to study prebiotic glycans directly in stool samples in distinct patient populations to help delineate the prebiotic mechanism.

The Effect of Osmotic Dehydration Conditions on the Potassium Content in Beetroot (Beta vulgaris L.)

Osmotic dehydration as a process of removing water from food by immersing the raw material in a hypertonic solution is used primarily to extend the shelf life of products and as a pretreatment before further processing steps, such as drying and freezing. However, due to the bi-directional mass transfer that occurs during osmotic dehydration, the process can also be used to shape sensory properties and enrich the plant matrix with nutrients. The purpose of this study was to evaluate the effect of osmotic dehydration on the absorption of potassium by beet pulp immersed in various hypertonic solutions (sucrose, inulin, erythritol, xylitol solutions) with the addition of three chemical forms of potassium (gluconate, citrate, chloride) using variable process conditions. The study proved that osmotic dehydration is an effective way to enrich food. The highest potassium content (5779.03 mg/100 g) was found in a sample osmotically dehydrated in a 50% erythritol solution with 5.0% potassium chloride addition with a process that lasted 180 min and took place at 30 °C. The results obtained indicate the high potential of osmotic dehydration in improving the health values of food products. In addition, the antioxidant activity and proximate composition of osmotically dehydrated samples were also characterized in this study.

Chronic constipation: focus on microbiome-targeted therapies with prebiotics, probiotics, and synbiotics

Chronic constipation is a global medical, social, and economic problem due to its negative impact on patients’ quality of life and increased risk of colorectal cancer, cardiovascular and cerebrovascular disorders. The gut microbiota plays an important role in the pathophysiology of constipation through its interplay with the immune system, enteral and central nervous system, representing a promising therapeutic target. Gut dysbiosis in patients with constipation is characterized by reduced relative numbers of bacteria producing lactate (Lactobacillaceae, Bifidobacteriaceae) and butyrate (Lachnospiraceae, Oscillospiraceae), as well as with increased numbers of those producing hydrogen sulfide (Desulfovibrionaceae) and methanogenic archaea (Methanobacteriaceae). The leading pathogenetic mechanism related to intestinal dysbiosis in chronic constipation, can be microbial metabolic abnormalities (metabolic dysbiosis) characterized by altered production of short-chain fatty acid, methane, hydrogen sulfide, tryptophan metabolites and by abnormal bile acid biotransformation. It has been proven that dysbiotic abnormalities of the intestinal microbiome play a role in the pathophysiology of constipation, which allows for the use of prebiotics, probiotics, and synbiotics for effective microbiome-modulating therapy in patients with chronic constipation. The proven role of dysbiotic abnormalities of the intestinal microbiome in the pathophysiology of chronic constipation determines the effectiveness of microbiome-modulating therapy (prebiotics, probiotics, synbiotics) in patients with this syndrome. Inulin is the most studied preboitic; it is a soluble food fiber that markedly contributes to the regulation of intestinal microbiota, stimulates the growth of beneficial bacteria, and production of anti-inflammatory metabolites. Inulin normalized the intestinal function in patients with chronic constipation increasing the stool frequency, softening the stool, and reducing the intestinal transit time. In addition, inulin modulates the immune response and impacts the absorption of minerals, appetite, and satiety. Treatment with probiotics is also associated with reduced intestinal transit time, compared to controls. According to a systematic review and meta-analysis of 30 randomized controlled trials, only Bifidobacterium lactis strains (but not other probiotics) significantly increase stool frequencies in chronic constipation in adults. Clinical studies have shown that the targeted probiotic Bifidobacterium lactis HN019 can significantly increase the stool frequencies in patients with low (≤ 3 per week) stool frequency up to 4.7–5.0 per week, reduce the intestinal transit time and the rate of functional gastroenterological symptoms in adults with constipation. Beyond its clinical effects, Bifidobacterium lactis HN019 leads to beneficial changes in intestinal microbiota, significantly increasing the bifidobacteria and decreasing the enterobacteria numbers. The results of trials confirm the importance of synbiotic correction of dysbiotic microbiota in all patients with constipation to increase stool frequencies and improve fecal consistency, as well as to prevent the chronic disorders associated with constipation. Synbiotics, such as a combination of Bifidobacterium lactis HN019 and inulin, with the properties of both complementary and synergic synbiotic, may have the greatest microbiome-modulating and functional potential to significantly improve clinical outcomes in patients with chronic constipation compared to probiotics or prebiotics used alone.

Low-Molecular-Weight Compounds Produced by the Intestinal Microbiota and Cardiovascular Disease

Cardiovascular disease is the main cause of mortality in industrialized countries, with over 500 million people affected worldwide. In this work, the roles of low-molecular-weight metabolites originating from the gut microbiome, such as short-chain fatty acids, hydrogen sulfide, trimethylamine, phenylacetic acid, secondary bile acids, indoles, different gases, neurotransmitters, vitamins, and complex lipids, are discussed in relation to their CVD-promoting or preventing activities. Molecules of mixed microbial and human hepatic origin, such as trimethylamine N-oxide and phenylacetylglutamine, are also presented. Finally, dietary agents with cardioprotective effects, such as probiotics, prebiotics, mono- and poly-unsaturated fatty acids, carotenoids, and polyphenols, are also discussed. A special emphasis is given to their gut microbiota-modulating properties.