Recent insight in α-glucan metabolism in probiotic bacteria

Effect of a Multi-Ingredient Coriolus-versicolor-Based Vaginal Gel in Women with HPV-Dependent Cervical Lesions: The Papilobs Real-Life Prospective Study

Human papillomavirus (HPV) is responsible for virtually all cervical cancers in women. HPV infection and persistency may lead to different-grade squamous intraepithelial lesions that can result in high-grade lesions and cancer. The objective was to prospectively evaluate the results of using a Coriolus-versicolor-based vaginal gel (Papilocare®) on HPV-dependent low-grade cervical lesion repair in a real-life scenario. HPV-positive women ≥ 25 years with ASCUS/LSIL cervical cytology results and concordant colposcopy images were included, receiving the vaginal gel one cannula/day for 21 days (first month) + one cannula/alternate days (five months). A 6-month second treatment cycle was prescribed when needed. Repair of the cervical low-grade lesions through cytology and colposcopy, HPV clearance, and level of satisfaction, and tolerability were evaluated. In total, 192 and 201 patients accounted for the total and safety analyses, respectively, and 77.1% repaired cervical lesions at 6 or 12 months (76.0% for high-risk HPV). Additionally, 71.6% achieved HPV clearance throughout the study's duration (70.6% for high-risk HPV). Satisfaction level was rated 7.9 and 7.5 out of 10 at 6 and 12 months, respectively. Only three mild-moderate product-related adverse events were reported, and all of them were resolved by the end of the study. In our study, we observed higher regression rates of low-grade cervical lesions in women treated with Papilocare® vaginal gel than spontaneous regression rates reported in the literature.

Enterosignatures define common bacterial guilds in the human gut microbiome

The human gut microbiome composition is generally in a stable dynamic equilibrium, but it can deteriorate into dysbiotic states detrimental to host health. To disentangle the inherent complexity and capture the ecological spectrum of microbiome variability, we used 5,230 gut metagenomes to characterize signatures of bacteria commonly co-occurring, termed enterosignatures (ESs). We find five generalizable ESs dominated by either Bacteroides, Firmicutes, Prevotella, Bifidobacterium, or Escherichia. This model confirms key ecological characteristics known from previous enterotype concepts, while enabling the detection of gradual shifts in community structures. Temporal analysis implies that the Bacteroides-associated ES is "core" in the resilience of westernized gut microbiomes, while combinations with other ESs often complement the functional spectrum. The model reliably detects atypical gut microbiomes correlated with adverse host health conditions and/or the presence of pathobionts. ESs provide an interpretable and generic model that enables an intuitive characterization of gut microbiome composition in health and disease.

Response of murine gut microbiota to a prebiotic based on oligosaccharides derived via hydrolysis of fungal α-(1→3)-d-glucan: Preclinical trial study on mice

We investigated the modulating effect of α-(1→3)-glucooligosaccharides (GOS), i.e. a product of fungal α-(1→3)-d-glucan hydrolysis, on the gut microbiota composition. Mice were fed with a GOS-supplemented diet and two control diets for 21 days, and fecal samples were collected at 0, 1, and 3-week time points. The bacterial community composition was determined by 16S rRNA gene Illumina sequencing. The gut microbiota of the GOS-supplemented mice showed profound time-dependent changes in the taxonomic composition; however, we did not observe significant changes in α-diversity indices. The biggest number of genus abundance shifts after 1 week of the treatment was noticed between the group of the GOS-supplemented mice and the controls; however, the differences were still relevant after the 3-week treatment. The GOS-supplemented mice displayed higher abundance of Prevotella spp., with a concomitant decrease in the abundance of Escherichia-Shigella. Hence, GOS seems to be a promising candidate for a new prebiotic.

Efficacy of a Coriolus versicolor-Based Vaginal Gel in Women With Human Papillomavirus-Dependent Cervical Lesions: The PALOMA Study

OBJECTIVE

The aim of the study was to evaluate the efficacy of Papilocare, a Coriolus versicolor-based vaginal gel, in repairing human papillomavirus (HPV)-related low-grade cervical lesions.

METHODS

The study is a multicenter, open-label, randomized, parallel-group, watchful waiting approach-controlled trial involving 91 HPV-positive women with low-grade Pap smear alterations and consistent colposcopy.

RESULTS

The percentage of patients with normal Pap smear and concordant colposcopy 3 and 6 months after receiving treatment (78.0% and 84.9%) was significantly higher than without treatment (54.8% and 64.5%), especially in high-risk HPV patients (79.5% and 87.8% vs 52.0% and 56.0%). At 6-month visit, overall HPV clearance was achieved by a greater number of patients receiving treatment (59.6%) compared with those without treatment (41.9%), especially high-risk HPV ones (62.5% vs 40.0%). The cervical re-epithelization score was significantly higher with treatment (mean = 4.5) than without (mean = 4.1). Compared with baseline, perceived stress decreased in the treatment group (from 21.1 to 19.0) and increased in the control group (from 17.7 to 20.7). A total of 7 possible or probable treatment-related adverse events were reported, most of them (n = 6) being mild or moderate in severity.

CONCLUSIONS

Treatment with Papilocare has demonstrated a better clinical benefit than the conventional watchful waiting approach in clinical practice for total and high-risk HPV patients in terms of its efficacy to treat HPV-related cervical lesions and to clear all HPV strains after a single 6-month period. It has demonstrated an adequate safety and tolerability and confers additional benefits such as higher re-epithelization, stress reduction, and high treatment adherence.

Genomic Comparison of Lactobacillus helveticus Strains Highlights Probiotic Potential

Lactobacillus helveticus belongs to the large group of lactic acid bacteria (LAB), which are the major players in the fermentation of a wide range of foods. LAB are also present in the human gut, which has often been exploited as a reservoir of potential novel probiotic strains, but several parameters need to be assessed before establishing their safety and potential use for human consumption. In the present study, six L. helveticus strains isolated from natural whey cultures were analyzed for their phenotype and genotype in exopolysaccharide (EPS) production, low pH and bile salt tolerance, bile salt hydrolase (BSH) activity, and antibiotic resistance profile. In addition, a comparative genomic investigation was performed between the six newly sequenced strains and the 51 publicly available genomes of L. helveticus to define the pangenome structure. The results indicate that the newly sequenced strain UC1267 and the deposited strain DSM 20075 can be considered good candidates for gut-adapted strains due to their ability to survive in the presence of 0.2% glycocholic acid (GCA) and 1% taurocholic and taurodeoxycholic acid (TDCA). Moreover, these strains had the highest bile salt deconjugation activity among the tested L. helveticus strains. Considering the safety profile, none of these strains presented antibiotic resistance phenotypically and/or at the genome level. The pangenome analysis revealed genes specific to the new isolates, such as enzymes related to folate biosynthesis in strains UC1266 and UC1267 and an integrated phage in strain UC1035. Finally, the presence of maltose-degrading enzymes and multiple copies of 6-phospho-β-glucosidase genes in our strains indicates the capability to metabolize sugars other than lactose, which is related solely to dairy niches.

An Extracellular Cell-Attached Pullulanase Confers Branched α-Glucan Utilization in Human Gut Lactobacillus acidophilus

Of the few predicted extracellular glycan-active enzymes, glycoside hydrolase family 13 subfamily 14 (GH13_14) pullulanases are the most common in human gut lactobacilli. These enzymes share a unique modular organization, not observed in other bacteria, featuring a catalytic module, two starch binding modules, a domain of unknown function, and a C-terminal surface layer association protein (SLAP) domain. Here, we explore the specificity of a representative of this group of pullulanases, Lactobacillus acidophilus Pul13_14 (LaPul13_14), and its role in branched α-glucan metabolism in the well-characterized Lactobacillus acidophilus NCFM, which is widely used as a probiotic. Growth experiments with L. acidophilus NCFM on starch-derived branched substrates revealed a preference for α-glucans with short branches of about two to three glucosyl moieties over amylopectin with longer branches. Cell-attached debranching activity was measurable in the presence of α-glucans but was repressed by glucose. The debranching activity is conferred exclusively by LaPul13_14 and is abolished in a mutant strain lacking a functional LaPul13_14 gene. Hydrolysis kinetics of recombinant LaPul13_14 confirmed the preference for short-branched α-glucan oligomers consistent with the growth data. Curiously, this enzyme displayed the highest catalytic efficiency and the lowest K_m reported for a pullulanase. Inhibition kinetics revealed mixed inhibition by β-cyclodextrin, suggesting the presence of additional glucan binding sites besides the active site of the enzyme, which may contribute to the unprecedented substrate affinity. The enzyme also displays high thermostability and higher activity in the acidic pH range, reflecting adaptation to the physiologically challenging conditions in the human gut.IMPORTANCE Starch is one of the most abundant glycans in the human diet. Branched α-1,6-glucans in dietary starch and glycogen are nondegradable by human enzymes and constitute a metabolic resource for the gut microbiota. The role of health-beneficial lactobacilli prevalent in the human small intestine in starch metabolism remains unexplored in contrast to colonic bacterial residents. This study highlights the pivotal role of debranching enzymes in the breakdown of starchy branched α-glucan oligomers (α-limit dextrins) by human gut lactobacilli exemplified by Lactobacillus acidophilus NCFM, which is one of the best-characterized strains used as probiotics. Our data bring novel insight into the metabolic preference of L. acidophilus for α-glucans with short α-1,6-branches. The unprecedented affinity of the debranching enzyme that confers growth on these substrates reflects its adaptation to the nutrient-competitive gut ecological niche and constitutes a potential advantage in cross-feeding from human and bacterial dietary starch metabolism.

Lactobacillus reuteri Strains Convert Starch and Maltodextrins into Homoexopolysaccharides Using an Extracellular and Cell-Associated 4,6-α-Glucanotransferase

Exopolysaccharides (EPS) of lactic acid bacteria (LAB) are of interest for food applications. LAB are well-known to produce α-glucan from sucrose by extracellular glucansucrases. Various Lactobacillus reuteri strains also possess 4,6-α-glucanotransferase (4,6-α-GTase) enzymes. Purified 4,6-α-GTases (e.g., GtfB) were shown to act on starches (hydrolysates), cleaving α1→4 linkages and synthesizing α1→6 linkages, yielding isomalto-/maltopolysaccharides (IMMP). Here we report that also L. reuteri cells with these extracellular, cell-associated 4,6-α-GTases synthesize EPS (α-glucan) from starches (hydrolysates). NMR, SEC, and enzymatic hydrolysis of EPS synthesized by L. reuteri 121 cells showed that these have similar linkage specificities but generally are much bigger in size than IMMP produced by the GtfB enzyme. Various IMMP-like EPS are efficiently used as growth substrates by probiotic Bifidobacterium strains that possess amylopullulanase activity. IMMP-like EPS thus have potential prebiotic activity and may contribute to the application of probiotic L. reuteri strains grown on maltodextrins or starches as synbiotics.