A study of the prebiotic effect of lactulose at low dosages in healthy Japanese women

Effects of a prebiotic formulation on the composition of the faecal microbiota of people with functional constipation

PURPOSE

Prebiotics are defined as substances which selectively promote beneficial gut microbes leading to a health benefit for the host. Limited trials have been carried out investigating their effect on the microbiota composition of individuals afflicted by functional constipation with equivocal outcomes. In a 21-day randomised, controlled clinical trial involving 61 adults with functional constipation, a prebiotic formulation with partially hydrolysed guar gum and acacia gum as its main ingredients, significantly increased complete spontaneous bowel motions in the treatment group. This follow-up exploratory analysis investigated whether the prebiotic was associated with changes to the composition, richness, and diversity of the faecal microbiota.

METHODS

Participants provided a faecal specimen at baseline and on day 21 of the intervention period. Whole genome metagenomic shotgun sequencing comprehensively assessed taxonomic and functional composition of the microbiota.

RESULTS

Linear mixed effects regression models adjusted for potential confounders showed a significant reduction in species richness of 28.15 species (95% CI - 49.86, - 6.43) and Shannon diversity of 0.29 units (95% CI - 0.56, - 0.02) over the trial period in the prebiotic group. These changes were not observed in the control group, and functional composition was unchanged in both groups.

CONCLUSION

In adults with functional constipation, the intake of a prebiotic formulation was associated with a decline of species richness and Shannon diversity. Further research regarding the associations between prebiotics and the composition and function of the gut microbiota is warranted.

Functional constipation and the effect of prebiotics on the gut microbiota: a review

Functional constipation is a significant health issue impacting the lives of an estimated 14 % of the global population. Non-pharmaceutical treatment advice for cases with no underlying medical conditions focuses on exercise, hydration and an increase in dietary fibre intake. An alteration in the composition of the gut microbiota is thought to play a role in constipation. Prebiotics are non-digestible food ingredients that selectively stimulate the growth of a limited number of bacteria in the colon with a benefit for host health. Various types of dietary fibre, though not all, can act as a prebiotic. Short-chain fatty acids produced by these microbes play a critical role as signalling molecules in a range of metabolic and physiological processes including laxation, although details are unclear. Prebiotics have a history of safe use in the food industry spanning several decades and are increasingly used as supplements to alleviate constipation. Most scientific research on the effects of prebiotics and gut microbiota has focussed on inflammatory bowel disease rather than functional constipation. Very few clinical studies evaluated the efficacy of prebiotics in the management of constipation and their effect on the microbiota, with highly variable designs and conflicting results. Despite this, broad health claims are made by manufacturers of prebiotic supplements. This narrative review provides an overview of the literature on the interaction of prebiotics with the gut microbiota and their potential clinical role in the alleviation of functional constipation.

Lactulose Ingestion Induces a Rapid Increase in Genus Bifidobacterium in Healthy Japanese: A Randomised, Double-Blind, Placebo-Controlled Crossover Trial

Oral administration of a low dose of lactulose increases the abundance of genus Bifidobacterium in the large intestine; however, the details of the daily variation in Bifidobacterium have not been researched. To observe how the intestinal microbiota, including Bifidobacterium, change, especially immediately after the initiation of ingestion, we conducted a randomised, placebo-controlled, double-blind crossover study of ingestion of 4 g lactulose/day for 2 weeks in 36 healthy Japanese (including males and females). The primary outcome was the percentage of Bifidobacterium in the faecal bacteria. In the lactulose-treatment group, the percentage of Bifidobacterium was already significantly higher 2 days after starting lactulose ingestion than in the placebo group (20.5 ± 1.2% vs. 17.1 ± 1.2%, p = 0.021). Significant differences were maintained, gradually widening, until the end of the 2-week intervention period. There were significant increases in the percentage and the number of Bifidobacterium with ingestion of 4 g lactulose/day for 2 weeks, but no significant changes in the beta diversity of the intestinal microbiota between lactulose and placebo ingestion. The percentage of Bifidobacterium in the faecal bacteria returned to its original level within a week of the end of intervention with lactulose.

The potential role of lactulose pharmacotherapy in the treatment and prevention of diabetes

The non-absorbable disaccharide lactulose is mostly used in the treatment of various gastrointestinal disorders such as chronic constipation and hepatic encephalopathy. The mechanism of action of lactulose remains unclear, but it elicits more than osmotic laxative effects. As a prebiotic, lactulose may act as a bifidogenic factor with positive effects in preventing and controlling diabetes. In this review, we summarized the current evidence for the effect of lactulose on gut metabolism and type 2 diabetes (T2D) prevention. Similar to acarbose, lactulose can also increase the abundance of the short-chain fatty acid (SCFA)-producing bacteria Lactobacillus and Bifidobacterium as well as suppress the potentially pathogenic bacteria Escherichia coli. These bacterial activities have anti-inflammatory effects, nourishing the gut epithelial cells and providing a protective barrier from microorganism infection. Activation of peptide tyrosine tyrosine (PYY) and glucagon-like peptide 1 (GLP1) can influence secondary bile acids and reduce lipopolysaccharide (LPS) endotoxins. A low dose of lactulose with food delayed gastric emptying and increased the whole gut transit times, attenuating the hyperglycemic response without adverse gastrointestinal events. These findings suggest that lactulose may have a role as a pharmacotherapeutic agent in the management and prevention of type 2 diabetes via actions on the gut microbiota.

Therapeutic Effects of Prebiotics on Constipation: A Schematic Review

Constipation is a highly prevalent functional gastrointestinal disorder that may significantly affect the quality of life and health care costs. Treatment for constipation has been broadly reviewed by cognitive therapies, medications, and surgical interventions. Gut microbiota such as Bifidobacterium, Clostridium, Bacteroidetes, and Lactobacilli have been demonstrated in functional gastrointestinal disorders and prebiotics to play a role in augmenting their presence. Prebiotics are ingredients in foods that remain undigested, stimulating the bacteria. There are a variety of prebiotics; however, there exists only a handful of studies that describe their efficacy for chronic constipation. The purpose of this study is to review the available literature on the utility of different commercially available prebiotics in patients with functional and chronic idiopathic constipation. To fulfil the objectives of the study, published articles in the English language on databases such as Pubmed, Ovid Medline, and EMBASE were searched. The terms prebiotics, constipation, chronic constipation, functional constipation were used. We reviewed and included 21 randomized controlled trials exploring the role of prebiotics in constipated adults. Prebiotics are effective treatments for chronic idiopathic constipation and showed improvement in the stool consistency, number of bowel moments and bloating. Although which prebiotic formulary would promote improved symptoms of constipation is still not clear.

Low-Dose Lactulose as a Prebiotic for Improved Gut Health and Enhanced Mineral Absorption

Although medium and high doses of lactulose are used routinely for the treatment of constipation and hepatic encephalopathy, respectively, a wealth of evidence demonstrates that, at low doses, lactulose can also be used as a prebiotic to stimulate the growth of health-promoting bacteria in the gastrointestinal tract. Indeed, multiple preclinical and clinical studies have shown that low doses of lactulose enhance the proliferation of health-promoting gut bacteria (e.g., Bifidobacterium and Lactobacillus spp.) and increase the production of beneficial metabolites [e.g., short-chain fatty acids (SCFAs)], while inhibiting the growth of potentially pathogenic bacteria (e.g., certain clostridia). SCFAs produced upon microbial fermentation of lactulose, the most abundant of which is acetate, are likely to contribute to immune regulation, which is important not only within the gut itself, but also systemically and for bone health. Low-dose lactulose has also been shown to enhance the absorption of minerals such as calcium and magnesium from the gut, an effect which may have important implications for bone health. This review provides an overview of the preclinical and clinical evidence published to date showing that low-dose lactulose stimulates the growth of health-promoting gut bacteria, inhibits the growth of pathogenic bacteria, increases the production of beneficial metabolites, improves mineral absorption, and has good overall tolerability. Implications of these data for the use of lactulose as a prebiotic are also discussed.

Highlighting the Relevance of Gut Microbiota Manipulation in Inflammatory Bowel Disease

Two different conditions are included in inflammatory bowel disease (IBD), Crohn's disease (CD) and ulcerative colitis (UC), being distinguished by chronic recurrence of gut inflammation in persons that are genetically predisposed and subjected to environmental causative factors. The normal structure of the gut microbiome and its alterations in IBD were defined in several microbial studies. An important factor in the prolonged inflammatory process in IBD is the impaired microbiome or "dysbiosis". Thus, gut microbiome management is likely to be an objective in IBD treatment. In this review, we analyzed the existing data regarding the pathophysiological/therapeutic implications of intestinal microflora in the development and evolution of IBD. Furthermore, the main effects generated by the administration of probiotics, prebiotics, fecal transplantation, and phytochemicals supplementation were analyzed regarding their potential roles in improving the clinical and biochemical status of patients suffering from Crohn's disease (CD) and ulcerative colitis (UC), and are depicted in the sections/subsections of the present paper. Data from the literature give evidence in support of probiotic and prebiotic therapy, showing effects such as improving remission rate, improving macroscopic and microscopic aspects of IBD, reducing the pro-inflammatory cytokines and interleukins, and improving the disease activity index. Therefore, the additional benefits of these therapies should not be ignored as adjuvants to medical therapy.

Prebiotic Food Intake May Improve Bone Resorption in Japanese Female Athletes: A Pilot Study

The aim of the present study was to clarify the influence of inulin and lactulose-fortified prebiotic food intakes on bone metabolism turnover among Japanese female athletes. The participants included 29 female athletes aged 18–25 years. They were requested to consume their habitual foods or drinks with one pack of prebiotic food every day for 12 weeks. Dietary intake, training time, body composition, blood sample, and fecal microbiota were assessed during this intervention period. Body composition, total energy intake, and training time of the participants revealed no significant changes during the intervention period. The occupation ratio of Bifidobacterium spp. was significantly increased at 3 and 4 weeks (18.0 ± 8.3% and 17.6 ± 8.5%, respectively) compared to that of pre-intervention (11.7 ± 7.3%) (p = 0.019 and p = 0.035, respectively). The serum TRACP-5b level was significantly decreased at 12 weeks (363 ± 112 mU/dL) compared to that at baseline (430 ± 154 mU/dL) (p = 0.018). These results suggest that the prebiotic food used in this study might have beneficial effects on bone health and gut microbial environment among female athletes. Further studies are warranted to identify the mechanism of the prebiotics–gut–bone axis.

Bifidobacterium response to lactulose ingestion in the gut relies on a solute-binding protein-dependent ABC transporter

This study aims to understand the mechanistic basis underlying the response of Bifidobacterium to lactulose ingestion in guts of healthy Japanese subjects, with specific focus on a lactulose transporter. An in vitro assay using mutant strains of Bifidobacterium longum subsp. longum 105-A shows that a solute-binding protein with locus tag number BL105A_0502 (termed LT-SBP) is primarily involved in lactulose uptake. By quantifying faecal abundance of LT-SBP orthologues, which is defined by phylogenetic analysis, we find that subjects with 10⁷ to 10⁹ copies of the genes per gram of faeces before lactulose ingestion show a marked increase in Bifidobacterium after ingestion, suggesting the presence of thresholds between responders and non-responders to lactulose. These results help predict the prebiotics-responder and non-responder status and provide an insight into clinical interventions that test the efficacy of prebiotics.

Lactulose ingestion causes an increase in the abundance of gut-resident bifidobacteria in Japanese women: a randomised, double-blind, placebo-controlled crossover trial

The genus Bifidobacterium comprises various bacterial species, and the complement of species within the human intestinal tract differs from individual to individual. The balance of these bifidobacterial species remains poorly understood, although it is known that the abundance of bifidobacteria increases following the ingestion of prebiotics. We previously conducted a randomised, placebo-controlled, double-blind, crossover study of 2 g/day lactulose ingestion for 2 weeks in 60 Japanese women. To study the effect of lactulose ingestion on each bifidobacterial species, here, we measured the abundance of each of the principal bifidobacterial species. After lactulose ingestion, the log cell counts of the Bifidobacterium adolescentis group (8.97±0.08 vs 9.39±0.08, P=0.0019), Bifidobacterium catenulatum group (9.45±0.10 vs 9.65±0.10, P=0.0032) and Bifidobacterium longum group (9.01±0.07 vs 9.29±0.07, P=0.0012) were significantly higher than in the placebo ingestion control group. However, the log cell counts were similar for Bifidobacterium breve (8.12±0.12 vs 8.33±0.12, P=0.20), Bifidobacterium bifidum (9.08±0.12 vs 9.42±0.14, P=0.095) and Bifidobacterium animalis subspecies lactis (8.65±0.53 vs 8.46±0.46, P=0.77). Cluster analysis of the log cell count data at the bifidobacterial species level revealed three distinct clusters, but the combinations and ratios of the constituent bifidobacteria were not affected by lactulose ingestion. Furthermore, principal coordinate analysis of the intestinal microbiota in the lactulose and placebo ingestion groups using Illumina MiSeq showed no significant differences in the intestinal microbiota as a whole. These results suggest that 2 g/day lactulose ingestion for 2 weeks significantly increases the abundance of intestinal bifidobacteria, but does not affect the intestinal microbiota as a whole.

Mechanisms of Action of Prebiotics and Their Effects on Gastro-Intestinal Disorders in Adults

In recent years, research has focused on the use of dietary fibers and prebiotics, since many of these polysaccharides can be metabolized by intestinal microbiota, leading to the production of short-chain fatty acids. The metabolites of prebiotic fermentation also show anti-inflammatory and immunomodulatory capabilities, suggesting an interesting role in the treatment of several pathological conditions. Galacto-oligosaccharide and short- and long-chain fructans (Fructo-oligosaccharides and inulin) are the most studied prebiotics, even if other dietary compounds seem to show the same features. There is an increasing interest in dietary strategies to modulate microbiota. The aim of this review is to explore the mechanisms of action of prebiotics and their effects on the principal gastro-intestinal disorders in adults, with a special focus on Galacto-oligosaccharides, Fructo-oligosaccharides, lactulose and new emerging substances which currently have evidence of prebiotics effects, such as xilooligosaccharides, soybean oligosaccharides, isomaltooligosaccharides, lactobionic acid, resistant starch and polyphenols.