Evidence for cholesterol-lowering activity by Bifidobacterium bifidum PRL2010 through gut microbiota modulation

Probiotic and functional characterization of bifidobacteria of Indian human origin

AIMS

To identify and characterize the probiotic and functional attributes of bifidobacteria isolated from human sources by in vitro methods.

METHODS AND RESULTS

Twelve isolates of bifidobacteria were obtained from different human sources viz; human milk, infant and adult faeces. The preliminary identification of isolates was done using genus-specific PCR followed by species level identification using 16S rRNA sequencing. All the isolates invariably showed potential probiotic characteristics. Finally, three most promising isolates were subjected to safety evaluation and were found to be safe. These were further evaluated for their potential functional characteristics like, antioxidative, antimutagenic and cholesterol assimilation. The isolates viz; NBIF-5 (73·55 ± 0·03%) and NBIF-7 (64·06 ± 0·03%) assimilated significantly higher cholesterol than NBIF-2. The maximum antioxidative activity was observed in NBIF-2 (56·56 ± 0·28% of radical inhibition). High percentage antimutagenicity scores of 52·41 ± 2·25% and 53·68 ± 1·98% against sodium azide (NaN3) were shown by NBIF-2 and NBIF-7 respectively.

CONCLUSIONS

Three strains (NBIF-2, NBIF-5 and NBIF-7) were found to be endowed with appreciable probiotic and functional activities.

SIGNIFICANCE AND IMPACT OF THE STUDY

With growing demands for probioitcs and bifidobacteria being prominent ones, new strains of diversified origin have the potential to be explored for commercial and functional applications and thus can be added to the existing commercially available strains of this genera.

Mechanisms responsible for the hypocholesterolaemic effect of regular consumption of probiotics

CVD affect a large proportion of the world's population, with dyslipidaemia as the major risk factor. The regular consumption of both probiotic bacteria and yeast has been associated with improvement in the serum lipid profile. Thus, the present review aims to describe and discuss the potential mechanisms responsible for the hypocholesterolaemic effect of regular consumption of probiotic bacteria and yeast. Regarding the hypocholesterolaemic effect of probiotic bacteria, the potential mechanisms responsible include: deconjugation of bile salts; modulation of lipid metabolism; and decreased absorption of intestinal cholesterol through co-precipitation of intestinal cholesterol with the deconjugated bile salts, incorporation and assimilation of cholesterol in the cell membrane of the probiotics, intestinal conversion of cholesterol in coprostanol, and inhibition of the expression of the intestinal cholesterol transporter Niemann-Pick C1 like 1 (NPC1L1) in the enterocytes. The potential mechanisms responsible for the hypocholesterolaemic effect of probiotic yeasts include: deconjugation of bile salts; co-precipitation of intestinal cholesterol with the deconjugated bile salts; incorporation and assimilation of cholesterol in the cell membrane; and inhibition of hepatic cholesterol synthesis. The regular consumption of probiotic bacteria and yeast, as a non-pharmaceutical approach to help manage cardiovascular risk, holds promise, according to the beneficial hypocholesterolaemic effects described herein. However, the hypocholesterolaemic effects vary according to the strains used, the physiological state of the host, and the type of diet to which the probiotics are added. Further studies are necessary to fill the gaps with regard to the knowledge related to this topic.

Isolation, Identification, and Evaluation of New Lactic Acid Bacteria Strains with Both Cellular Antioxidant and Bile Salt Hydrolase Activities In Vitro

In this study, we analyzed Chinese traditional fermented food to isolate and identify new lactic acid bacteria (LAB) strains with novel functional properties and to evaluate their cellular antioxidant and bile salt hydrolase (BSH) activities in vitro. A sequential screening strategy was developed to efficiently isolate and obtain 261 LAB strains tolerant of bile salt, acid, and H₂O₂ from nine Chinese traditional fermented foods. Among these strains, 70 were identified as having 2,2-diphenyl-1-picrylhydrazyl radical scavenging and/or BSH activity. These strains belonged to eight species: Enterococcus faecium (33% of the strains), Lactobacillus plantarum (26%), Leuconostoc mesenteroides (14%), Pediococcus pentosaceus (6%), Enterococcus durans (9%), Lactobacillus brevis (9%), Pediococcus ethanolidurans (3%), and Lactobacillus casei (1%). The pulsed-field gel electrophoresis genome fingerprinting profiles of these strains revealed 38 distinct pulsotypes, indicating a high level of genomic diversity among the tested strains. Twenty strains were further evaluated for hydroxyl radical scavenging activity, reducing power, and ferrous ion chelating activity exerted by both viable intact cells and/or intracellular cell-free extracts. Some strains, such as L. plantarum D28 and E. faecium B28, had high levels of both cellular antioxidant and BSH activities in vitro. These strains are promising probiotic components for health-promoting functional foods.

Bifidobacteria-Insight into clinical outcomes and mechanisms of its probiotic action

The invasion of pathogens causes a disruption of the gut homeostasis. Innate immune responses and those triggered by endogenous microbiota form the first line of defence in our body. Pathogens often successfully overcome the resistances offered, calling for therapeutic intervention. Conventional strategy involving antibiotics might eradicate pathogens, but often leave the gut uncolonised and susceptible to recurrences. Probiotic supplements are useful alternatives. Bifidobacterium is one of widely studied probiotic genus, effective in restoring gut homeostasis. Mechanisms of probiotic action of bifidobacteria are several, often with strain-specificity. Analysis of streamlined literature reports reveal that although most studies report the probiotic aspect of bifidobacteria, sporadic documented contradictory results exist, challenging its therapeutic application and prompting studies to unambiguously establish the strain-associated probiotic activity and negate adverse effects prior to its clinical administration. Multi-strain/combinatorial therapy possibly relies on a combination of underlying operating mechanisms, each contributing towards enhanced probiotic efficacy, understanding which could help in developing customised formulations against targeted pathogens. Bifidogenic activity is also mediated by surface-associated structural components such as exopolysaccharides, lipoteichoic acids along with metabolites and bifidocins. This highlights scope for developing advanced structural therapeutic strategy which might be pivotal in replacing intact cell probiotics therapy.