In vitro lactose fermentation by human colonic bacteria is modified by Lactobacillus acidophilus supplementation

Prebiotic Strategies to Manage Lactose Intolerance Symptoms

Lactose intolerance, which affects about 65-75% of the world's population, is caused by a genetic post-weaning deficiency of lactase, the enzyme required to digest the milk sugar lactose, called lactase non-persistence. Symptoms of lactose intolerance include abdominal pain, bloating and diarrhea. Genetic variations, namely lactase persistence, allow some individuals to metabolize lactose effectively post-weaning, a trait thought to be an evolutionary adaptation to dairy consumption. Although lactase non-persistence cannot be altered by diet, prebiotic strategies, including the consumption of galactooligosaccharides (GOSs) and possibly low levels of lactose itself, may shift the microbiome and mitigate symptoms of lactose consumption. This review discusses the etiology of lactose intolerance and the efficacy of prebiotic approaches like GOSs and low-dose lactose in symptom management.

Unveiling the dynamics of the breast milk microbiome: impact of lactation stage and gestational age

BACKGROUND

Breast milk (BM) provides complete nutrition for infants for the first six months of life and is essential for the development of the newborn's immature immune and digestive systems. While BM was conventionally believed to be sterile, recent advanced high throughput technologies have unveiled the presence of diverse microbial communities in BM. These insights into the BM microbiota have mainly originated from uncomplicated pregnancies, possibly not reflecting the circumstances of mothers with pregnancy complications like preterm birth (PTB).

METHODS

In this article, we investigated the BM microbial communities in mothers with preterm deliveries (before 37 weeks of gestation). We compared these samples with BM samples from healthy term pregnancies across different lactation stages (colostrum, transitional and mature milk) using 16S rRNA gene sequencing.

RESULTS

Our analysis revealed that the microbial communities became increasingly diverse and compositionally distinct as the BM matured. Specifically, mature BM samples were significantly enriched in Veillonella and lactobacillus (Kruskal Wallis; p < 0.001) compared to colostrum. The comparison of term and preterm BM samples showed that the community structure was significantly different between the two groups (Bray Curtis and unweighted unifrac dissimilarity; p < 0.001). Preterm BM samples exhibited increased species richness with significantly higher abundance of Staphylococcus haemolyticus, Propionibacterium acnes, unclassified Corynebacterium species. Whereas term samples were enriched in Staphylococcus epidermidis, unclassified OD1, and unclassified Veillonella among others.

CONCLUSION

Our study underscores the significant influence of pregnancy-related complications, such as preterm birth (before 37 weeks of gestation), on the composition and diversity of BM microbiota. Given the established significance of the maternal microbiome in shaping child health outcomes, this investigation paves the way for identifying modifiable factors that could optimize the composition of BM microbiota, thereby promoting maternal and infant health.

Macronutrient Digestion and Absorption in the Preterm Infant

The human fetus receives oral nutrition through swallowed amniotic fluid and this makes a significant nutritional contribution to the fetus. Postnatally, macronutrient absorption and digestion appear to function well in the preterm infant. Although pancreatic function is relatively poor, the newborn infant has several mechanisms to overcome this. These include a range of digestive enzymes in human milk, novel digestive enzymes involved in fat and protein digestion that do not appear to be present in the older child or adult, and the presence of a Bifidobacterium-rich colonic microbiome that may "scavenge" unabsorbed macronutrients and make them available to the infant.

Lactose Intolerance, Dairy Avoidance, and Treatment Options

Lactose intolerance refers to symptoms related to the consumption of lactose-containing dairy foods, which are the most common source for this disaccharide. While four causes are described, the most common is the genetically-determined adult onset lactose maldigestion due to loss of intestinal lactase governed by control of the gene by a 14,000 kb promoter region on chromosome 2. Gastrointestinal symptoms from lactose have expanded to include systemic effects and have also been confounded by other food intolerances or functional gastrointestinal disorders. Partly because lactose maldigestion is often interpreted as lactose intolerance (symptoms), focus of therapy for these symptoms starts with lactose restriction. However, withholding of dairy foods completely is not appropriate due to a more favorable impact on health. Industrial efforts to substitute with plant-based products is not completely successful at this time. This narrative article reviews the complexities of the perception of lactose intolerance, its epidemiology, and pathogenesis. Treatments are discussed, including the inappropriateness of dairy avoidance. In conjunction, effects of dairy products on 19 common diseases are reviewed. Different methods of treatment, lactose-reduced products, plant-based dairy substitutes, adaptation, prebiotics, exogenous lactase, probiotics, and some other dietary interventions are further discussed.

Adverse effect of early-life high-fat/high-carbohydrate ("Western") diet on bacterial community in the distal bowel of mice

Obesity and other lifestyle diseases in modern society can be related to historical dietary changes from diets balanced in omega-6 and omega-3 to the unbalanced "Western-type" diet. It is recognized that diet influences the murine and human gut microbiome, and most research indicates that microbial diversity and composition are altered by high-fat diets (HFDs). However, good knowledge about the effects of early exposure to HFD on the maturation and structure of the bacterial community is limited. Using mice as model, we hypothesized that an HFD alters the early dynamic of the gut bacterial community toward an unstable/unhealthy state. By sequencing the V3 and V4 regions of the 16S ribosomal ribonucleic acid gene, we investigated the bacterial community in fecal samples of mice fed a control diet and an HFD at weaning (sampling time 1) and after 8 weeks of dietary intervention (11weeks of age; sampling time 2). Natural temporal microbiome maturation was evidenced by a general increase in microbial diversity and shifts in microbial community between sampling times 1 and 2 toward a mature community. However, the HFD led to significant structural segregation of the microbiome compared with controls; the HFD diet repressed health-enhancing bacteria (eg, Bifidobacterium and Akkermansia) and promoted health-detracting bacteria (ie, those associated with gut disorders, eg, Dorea). We suggest that early-life consumption of HFD negatively impacts the natural gut bacterial community maturation leading toward a potentially persistent unhealthy stage.

Delivery Mode and the Transition of Pioneering Gut-Microbiota Structure, Composition and Predicted Metabolic Function

Cesarean (C-section) delivery, recently shown to cause excess weight gain in mice, perturbs human neonatal gut microbiota development due to the lack of natural mother-to-newborn transfer of microbes. Neonates excrete first the in-utero intestinal content (referred to as meconium) hours after birth, followed by intestinal contents reflective of extra-uterine exposure (referred to as transition stool) 2 to 3 days after birth. It is not clear when the effect of C-section on the neonatal gut microbiota emerges. We examined bacterial DNA in carefully-collected meconium, and the subsequent transitional stool, from 59 neonates [13 born by scheduled C-section and 46 born by vaginal delivery] in a private hospital in Brazil. Bacterial DNA was extracted, and the V4 region of the 16S rRNA gene was sequenced using the Illumina MiSeq (San Diego, CA, USA) platform. We found evidence of bacterial DNA in the majority of meconium samples in our study. The bacterial DNA structure (i.e., beta diversity) of meconium differed significantly from that of the transitional stool microbiota. There was a significant reduction in bacterial alpha diversity (e.g., number of observed bacterial species) and change in bacterial composition (e.g., reduced Proteobacteria) in the transition from meconium to stool. However, changes in predicted microbiota metabolic function from meconium to transitional stool were only observed in vaginally-delivered neonates. Within sample comparisons showed that delivery mode was significantly associated with bacterial structure, composition and predicted microbiota metabolic function in transitional-stool samples, but not in meconium samples. Specifically, compared to vaginally delivered neonates, the transitional stool of C-section delivered neonates had lower proportions of the genera Bacteroides, Parabacteroides and Clostridium. These differences led to C-section neonates having lower predicted abundance of microbial genes related to metabolism of amino and nucleotide sugars, and higher abundance of genes related to fatty-acid metabolism, amino-acid degradation and xenobiotics biodegradation. In summary, microbiota diversity was reduced in the transition from meconium to stool, and the association of delivery mode with microbiota structure, composition and predicted metabolic function was not observed until the passing of the transitional stool after meconium.

Dairy propionibacteria prevent the proliferative effect of plant lectins on SW480 cells and protect the metabolic activity of the intestinal microbiota in vitro

Plant lectins are specific carbohydrate-binding proteins that are widespread in legumes such as beans and pulses, seeds, cereals, and many plants used as farm feeds. They are highly resistant to cooking and digestion, reaching the intestinal lumen and/or blood circulation with biological activity. Since many legume lectins trigger harmful local and systemic reactions after their binding to the mucosal surface, these molecules are generally considered anti-nutritive and/or toxic substances. In the gut, specific cell receptors and bacteria may interact with these dietary components, leading to changes in intestinal physiology. It has been proposed that probiotic microorganisms with suitable surface glycosidic moieties could bind to dietary lectins, favoring their elimination from the intestinal lumen or inhibiting their interaction with epithelial cells. In this work, we assessed in vitro the effects of two representative plant lectins, concanavalin A (Con A) and jacalin (AIL) on the proliferation of SW480 colonic adenocarcinoma cells and metabolic activity of colonic microbiota in the absence or presence of Propionibacterium acidipropionici CRL 1198. Both lectins induced proliferation of colonic cells in a dose-dependent manner, whereas ConA inhibited fermentative activities of colonic microbiota. Pre-incubation of propionibacteria with lectins prevented these effects, which could be ascribed to the binding of lectins by bacterial cells since P. acidipropionici CRL 1198 was unable to metabolize these proteins, and its adhesion to colonic cells was reduced after reaction with Con A or AIL. The results suggest that consumption of propionibacteria at the same time as lectins could reduce the incidence of lectin-induced alterations in the gut and may be a tool to protect intestinal physiology.

Sex differences in the gut microbiome-brain axis across the lifespan

In recent years, the bidirectional communication between the gut microbiome and the brain has emerged as a factor that influences immunity, metabolism, neurodevelopment and behaviour. Cross-talk between the gut and brain begins early in life immediately following the transition from a sterile in utero environment to one that is exposed to a changing and complex microbial milieu over a lifetime. Once established, communication between the gut and brain integrates information from the autonomic and enteric nervous systems, neuroendocrine and neuroimmune signals, and peripheral immune and metabolic signals. Importantly, the composition and functional potential of the gut microbiome undergoes many transitions that parallel dynamic periods of brain development and maturation for which distinct sex differences have been identified. Here, we discuss the sexually dimorphic development, maturation and maintenance of the gut microbiome-brain axis, and the sex differences therein important in disease risk and resilience throughout the lifespan.

Adaptation to Lactose in Lactase Non Persistent People: Effects on Intolerance and the Relationship between Dairy Food Consumption and Evalution of Diseases

Dairy foods contain complex nutrients which interact with the host. Yet, evolution of lactase persistence has divided the human species into those that can or cannot digest lactose in adulthood. Such a ubiquitous trait has differential effects on humanity. The literature is reviewed to explore how the divide affects lactose handling by lactase non persistent persons. There are two basic differences in digesters. Firstly, maldigesters consume less dairy foods, and secondly, excess lactose is digested by colonic microflora. Lactose intolerance in maldigesters may occur with random lactose ingestion. However, lactose intolerance without maldigestion tends to detract from gaining a clear understanding of the mechanisms of symptoms formation and leads to confusion with regards to dairy food consumption. The main consequence of intolerance is withholding dairy foods. However, regular dairy food consumption by lactase non persistent people could lead to colonic adaptation by the microbiome. This process may mimic a prebiotic effect and allows lactase non persistent people to consume more dairy foods enhancing a favorable microbiome. This process then could lead to alterations in outcome of diseases in response to dairy foods in lactose maldigesters. The evidence that lactose is a selective human prebiotic is reviewed and current links between dairy foods and some diseases are discussed within this context. Colonic adaptation has not been adequately studied, especially with modern microbiological techniques.

Adult lactose digestion status and effects on disease

BACKGROUND

Adult assimilation of lactose divides humans into dominant lactase-persistent and recessive nonpersistent phenotypes.

OBJECTIVES

To review three medical parameters of lactose digestion, namely: the changing concept of lactose intolerance; the possible impact on diseases of microbial adaptation in lactase-nonpersistent populations; and the possibility that the evolution of lactase has influenced some disease pattern distributions.

METHODS

A PubMed, Google Scholar and manual review of articles were used to provide a narrative review of the topic.

RESULTS

The concept of lactose intolerance is changing and merging with food intolerances. Microbial adaptation to regular lactose consumption in lactase-nonpersistent individuals is supported by limited evidence. There is evidence suggestive of a relationship among geographical distributions of latitude, sunhine exposure and lactase proportional distributions worldwide.

DISCUSSION

The definition of lactose intolerance has shifted away from association with lactose maldigestion. Lactose sensitivity is described equally in lactose digesters and maldigesters. The important medical consequence of withholding dairy foods could have a detrimental impact on several diseases; in addition, microbial adaptation in lactase-nonpersistent populations may alter risk for some diseases. There is suggestive evidence that the emergence of lactase persistence, together with human migrations before and after the emergence of lactase persistence, have impacted modern-day diseases.

CONCLUSIONS

Lactose maldigestion and lactose intolerance are not synonymous. Withholding dairy foods is a poor method to treat lactose intolerance. Further epidemiological work could shed light on the possible effects of microbial adaptation in lactose maldigesters. The evolutionary impact of lactase may be still ongoing.

Development of microencapsulation delivery system for long-term preservation of probiotics as biotherapeutics agent

The administration of probiotic bacteria for health benefit has rapidly expanded in recent years, with a global market worth $32.6 billion predicted by 2014. The oral administration of most of the probiotics results in the lack of ability to survive in a high proportion of the harsh conditions of acidity and bile concentration commonly encountered in the gastrointestinal tract of humans. Providing probiotic living cells with a physical barrier against adverse environmental conditions is therefore an approach currently receiving considerable interest. Probiotic encapsulation technology has the potential to protect microorganisms and to deliver them into the gut. However, there are still many challenges to overcome with respect to the microencapsulation process and the conditions prevailing in the gut. This review focuses mainly on the methodological approach of probiotic encapsulation including biomaterials selection and choice of appropriate technology in detailed manner.

Biphasic assembly of the murine intestinal microbiota during early development

The birth canal provides mammals with a primary maternal inoculum, which develops into distinctive body site-specific microbial communities post-natally. We characterized the distal gut microbiota from birth to weaning in mice. One-day-old mice had colonic microbiota that resembled maternal vaginal communities, but at days 3 and 9 of age there was a substantial loss of intestinal bacterial diversity and dominance of Lactobacillus. By weaning (21 days), diverse intestinal bacteria had established, including strict anaerobes. Our results are consistent with vertical transmission of maternal microbiota and demonstrate a nonlinear ecological succession involving an early drop in bacterial diversity and shift in dominance from Streptococcus to Lactobacillus, followed by an increase in diversity of anaerobes, after the introduction of solid food. Mammalian newborns are born highly susceptible to colonization, and lactation may control microbiome assembly during early development.

Lactose in human breast milk an inducer of innate immunity with implications for a role in intestinal homeostasis

Postpartum, infants have not yet established a fully functional adaptive immune system and are at risk of acquiring infections. Hence, newborns are dependent on the innate immune system with its antimicrobial peptides (AMPs) and proteins expressed at epithelial surfaces. Several factors in breast milk are known to confer immune protection, but which the decisive factors are and through which manner they work is unknown. Here, we isolated an AMP-inducing factor from human milk and identified it by electrospray mass spectrometry and NMR to be lactose. It induces the gene (CAMP) that encodes the only human cathelicidin LL-37 in colonic epithelial cells in a dose- and time-dependent manner. The induction was suppressed by two different p38 antagonists, indicating an effect via the p38-dependent pathway. Lactose also induced CAMP in the colonic epithelial cell line T84 and in THP-1 monocytes and macrophages. It further exhibited a synergistic effect with butyrate and phenylbutyrate on CAMP induction. Together, these results suggest an additional function of lactose in innate immunity by upregulating gastrointestinal AMPs that may lead to protection of the neonatal gut against pathogens and regulation of the microbiota of the infant.

Synergistic impact of Lactobacillus fermentum, Lactobacillus plantarum and vincristine on 1,2-dimethylhydrazine-induced colorectal carcinogenesis in mice

Lactobacillus sp. is the most dominant probiotic strain of bacteria. Evidence indicates that the consumption of Lactobacillus sp. reduces the risk of colorectal cancer in animal models. The present study was carried out to determine whether administration of Lactobacillus fermentum/ Lactobacillus plantarum alone or in combination with vincristine have a synergistic impact on the control of colorectal cancer in an animal model. Mice with 1,2 dimethylhydrazine (DMH) hydrochloride-induced colon cancer were fed with L. fermentum and L. plantarum isolated along with vincristine. An increase in body weight, a decrease in ammonia concentration, a decrease in β glucosidase and β glucuronidase enzyme activity and a reduction in the number of crypts in the mice in the pre-carcinogen-induced group was noted when compared to these variables in the post-carcinogen-induced group. The body weight of the mice fed L. fermentum along with vincristine was increased (6.5 g), and was found to be 3.5 times higher compared to that of the control. A marked decrease in the ammonia concentration (240 mg), and β glucosidase (0.0023 IU) and β glucopyranose enzyme activity (0.0027 IU) was observed; 22.59% less ammonia concentration, 73.26% less β glucosidase activity and 56.46% less β glucuronidase enzyme activity was noted when compared to the control. A significant reduction in the number of aberrant crypt foci (ACF) (90%) was observed when compared to the control. Maximum protection was observed in the mice fed the probiotics and vincristine prior to cancer induction. Among the different dietary combinations tested in the present study, L. fermentum and vincristine showed a more extensive reduction in ammonia concentration, β glucosidase, β glucuronidase activity and the number of ACF.

Carbohydrate Elimination or Adaptation Diet for Symptoms of Intestinal Discomfort in IBD: Rationales for "Gibsons' Conundrum"

Therapeutic use of carbohydrates in inflammatory bowel diseases (IBDs) is discussed from two theoretical, apparent diametrically opposite perspectives: regular ingestion of prebiotics or withdrawal of virtually all carbohydrate components. Pathogenesis of IBD is discussed connecting microbial flora, host immunity, and genetic interactions. The best studied genetic example, NOD2 in Crohn's disease, is highlighted as a model which encompasses these interactions and has been shown to depend on butyrate for normal function. The role of these opposing concepts in management of irritable bowel syndrome (IBS) is contrasted with what is known in IBD. The conclusion reached is that, while both approaches may alleviate symptoms in both IBS and IBD, there is insufficient data yet to determine whether both approaches lead to equivalent bacterial effects in mollifying the immune system. This is particularly relevant in IBD. As such, caution is urged to use long-term carbohydrate withdrawal in IBD in remission to control IBS-like symptoms.

Lack of effect of lactose digestion status on baseline fecal micoflora

BACKGROUND

The genetics of intestinal lactase divide the world's population into two phenotypes: the ability (a dominant trait) or inability (a recessive trait) to digest lactose. A prebiotic effect of lactose may impact the colonic flora of these phenotypes differently.

OBJECTIVE

To detect and evaluate the effects of lactose on subjects divided according to their ability to digest lactose.

METHODS

A total of 57 healthy maldigesters (n=30) and digesters (n=27) completed diet questionnaires, genetic and breath hydrogen testing, and quantitative stool analysis for species of bacteria. Log10 transformation of bacterial counts was compared with lactose intake in both groups using multiple regression analysis.

RESULTS

There was a significant relationship between genetic and breath hydrogen tests. Daily lactose intake was marginally lower in lactose maldigesters (median [interquartile range] 12.2 g [31 g] versus 15 g [29.6 g], respectively). There was no relationship between lactose intake and breath hydrogen tests in either group. There were no differences in bacterial counts between the two groups, nor was there a relationship between bacterial counts and lactose intake in either group.

CONCLUSION

The differential bacterial effects of lactose were not quantitatively detected in stool samples taken in the present study.

Gut microbiota is not modified by Randomized, Double-blind, Placebo-controlled Trial of VSL#3 in Diarrhea-predominant Irritable Bowel Syndrome

Irritable Bowel Syndrome (IBS) is a common condition that negatively impacts the quality of life for many individuals. The exact etiology of this disorder is largely unknown; however, emerging studies suggest that the gut microbiota is a contributing factor. Several clinical trials show that probiotics, such as VSL#3, can have a favorable effect on IBS. This double-blind, randomized placebo-controlled study has been conducted in diarrhea-predominant IBS subjects in order to investigate the effect of VSL#3 on the fecal microbiota. The bacterial composition of the fecal microbiota was investigated using high-throughput microarray technology to detect 16S RNA. Twenty four subjects were randomized to receive VSL#3 or placebo for 8 weeks. IBS symptoms were monitored using GSRS and quality of life questionnaires. A favorable change in Satiety subscale was noted in the VSL #3 groups. However, the consumption of the probiotic did not change the gut microbiota. There were no adverse events or any safety concerns encountered during this study. To summarize, the use of VSL#3 in this pilot study was safe and showed improvement in specific GSRS-IBS scores in diarrhea-predominant IBS subjects. The gut microbiota was not affected by VSL#3 consumption suggesting that the mechanism of action is not directly linked to the microbiota.

Differential impact of lactose/lactase phenotype on colonic microflora

BACKGROUND

The ability to digest lactose divides the world's population into two phenotypes that may be risk variability markers for several diseases. Prebiotic effects likely favour lactose maldigesters who experience lactose spilling into their colon.

OBJECTIVE

To evaluate the effects of fixed-dose lactose solutions on fecal bifidobacteria and lactobacilli in digesters and maldigesters, and to determine whether the concept of a difference in ability to digest lactose is supported.

METHODS

A four-week study was performed in 23 lactose maldigesters and 18 digesters. Following two weeks of dairy food withdrawal, subjects ingested 25 g of lactose twice a day for two weeks. Stool bifidobacteria and lactobacilli counts pre- and postintervention were measured as the primary outcome. For secondary outcomes, total anaerobes, Enterobacteriaceae, beta-galactosidase and N-acetyl-beta-D-glucosaminidase activity in stool, as well as breath hydrogen and symptoms following lactose challenge tests, were measured.

RESULTS

Lactose maldigesters had a mean change difference (0.72 log10 colony forming unitsg stool; P=0.04) in bifidobacteria counts compared with lactose digesters. Lactobacilli counts were increased, but not significantly. Nevertheless, reduced breath hydrogen after lactose ingestion correlated with lactobacilli (r=-0.5; P<0.001). Reduced total breath hydrogen and symptom scorestogether, with a rise in fecal enzymes after intervention, were appropriate, but not significant.

CONCLUSIONS

Despite failure to achieve full colonic adaptation, the present study provided evidence for a differential impact of lactose on microflora depending on genetic lactase status. A prebiotic effect was evident in lactose maldigesters but not in lactose digesters. This may play a role in modifying the mechanisms of certain disease risks related to dairy food consumption between the two phenotypes.

Changes in bacterial communities from swine feces during continuous culture with starch

Bacteria from swine feces were grown in continuous culture with starch as the sole carbohydrate in order to monitor changes during fermentation and to determine how similar fermenter communities were to each other. DNA extracted from fermenter samples was analyzed by denaturing gradient gel electrophoresis (DGGE). A significant decrease in diversity was observed, the Shannon-Weaver index dropped from 1.92 to 1.13 after 14 days of fermentation. Likewise, similarity of fermenter communities to those in the fecal inoculum also decreased over time. Both diversity and similarity to the inoculum decreased most rapidly in the first few days of fermentation, reflecting a period of adaptation. Sequencing of DGGE bands indicated that the same species were present in replicate fermenters. Most of these bacteria were placed in the Clostridium coccoides/Eubacterium rectale group (likely saccharolytic butyrate producers), a dominant bacterial group in the intestinal tract of pigs. DGGE proved useful to monitor swine fecal communities in vitro and indicated the selection and maintenance of native swine intestinal bacteria during continuous culture.

Functional identification of a putative beta-galactosidase gene in the special lac gene cluster of Lactobacillus acidophilus

The putative beta-galactosidase gene (lacZ) of Lactobacillus acidophilus has a very low degree of homology to the Escherichia coli beta-galactosidase gene (lacZ) and locates in a special lac gene cluster which contains two beta-galactosidase genes. No functional characteristic of the putative beta-galactosidase has been described so far. In this study, the lacZ gene of L. acidophilus was hetero-expressed in E. coli and the recombinant protein was purified by a three-step procedure. The product of the lacZ gene was also extracted from L. acidophilus ATCC 4356 and active staining was carried out. The enzymatic properties of the purified recombinant LacZ were assayed. The results of hetero-expression showed the recombinant LacZ without tag had beta-galactosidase activity. The purified recombinant LacZ had a specific activity of 43.2 U/mg protein. The result of active staining showed that the functional product of the lacZ gene did exist in L. acidophilus. The L. acidophilus beta-galactosidase (LacZ) had an optimal pH of 6, an optimal temperature of 37 degrees C and could hydrolyze 73% of lactose in milk in 30 h at 10 degrees C. The L. acidophilus beta-galactosidase (LacZ) was identified as cold-adapted beta-galactosidase in this study for the first time, and may be useful for lactose removal from dairy products at low temperatures.

Fructose malabsorption may be gender dependent and fails to show compensation by colonic adaptation

Fructose malabsorption is linked to gastrointestinal and other unusual symptoms. Polymers of fructose are also recognized prebiotics. While some prebiotics can self-adapt when consumed regularly (resulting in decreased breath hydrogen and symptoms), we wondered whether self-adaptation occurs with basic fructose. We evaluated 90 subjects (61 females). Each completed a diet questionnaire and underwent a fructose challenge. Breath hydrogen and quantified symptom scores were recorded. Group comparisons for sum of breath hydrogen and total symptom scores were evaluated with the Mann-Whitney U test. Spearman's correlation coefficient and chi(2) or Fisher's exact test were used as appropriate. Malabsorption occurred in 29 patients (32.2%) and low-grade symptoms without malabsorption in 30 (33%). Women complained of symptoms more frequently (p = 0.04) and exhibited more fructose malabsorption (p = 0.0527). Breath hydrogen correlated with symptoms (r = 0.516, p = 0.0037). Adaptation with increasing pretest fructose intake was absent. We conclude that gender may influence fructose malabsorption and there is no adaptation to regular consumption.

Effects of yogurt and bifidobacteria supplementation on the colonic microbiota in lactose-intolerant subjects

AIMS

Colonic metabolism of lactose may play a role in lactose intolerance. We investigated whether a 2-week supplementation of Bifidobacterium longum (in capsules) and a yogurt enriched with Bifidobacterium animalis could modify the composition and metabolic activities of the colonic microbiota in 11 Chinese lactose-intolerant subjects.

METHODS AND RESULTS

The numbers of total cells, total bacteria and the Eubacterium rectale/Clostridium coccoides group in faeces as measured with fluorescent in situ hybridization and the faecal beta-galactosidase activity increased significantly during supplementation. The number of Bifidobacterium showed a tendency to increase during and after supplementation. With PCR-denaturing gradient gel electrophoresis, in subjects in which B. animalis and B. longum were not detected before supplementation, both strains were present in faeces during supplementation, but disappeared after supplementation. The degree of lactose digestion in the small intestine and the oro-caecal transit time were not different before and after supplementation, whereas symptom scores after lactose challenge decreased after supplementation.

CONCLUSIONS

The results suggest that supplementation modifies the amount and metabolic activities of the colonic microbiota and alleviates symptoms in lactose-intolerant subjects. The changes in the colonic microbiota might be among the factors modified by the supplementation which lead to the alleviation of lactose intolerance.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides evidence for the possibility of managing lactose intolerance with dietary lactose (yogurt) and probiotics via modulating the colonic microbiota.

In vitro effects on polydextrose by colonic bacteria and caco-2 cell cyclooxygenase gene expression

A 4-stage colon simulator and a cell culture-based human intestinal epithelial function model were combined to study the effects of a soluble fiber, polydextrose (PDX), on intestinal microbes and mucosal functions relevant to the risk of colon cancer. We observed sustained degradation of PDX throughout the different stages of the model. The fermentation was characterized by gradual degradation of PDX, production of short-chain fatty acids, and no increasing in putrefactive markers. We observed less marked effects in the microbial densities. When we applied colon fermentation metabolites obtained from the simulators with PDX to Caco-2 colon cancer cell line, a significant dose-dependent decreasing effect on cyclooxygenase-2 (COX-2) and an increasing effect on COX-3 expression levels were observed. PDX concentration appeared not to have effect on the expression levels of COX-1. Overexpression of COX-2 and decreased expression of COX-1 have been suggested to be characteristics of colon cancer. The exact physiological role of COX-3, an intron-retaining splice variant of COX-1, is not known, but it is suspected to play a role in transcriptional regulation of COX-1 and COX-2. In vitro modulation of COX expression by colon microbial fermentation products of polydextrose offers an interesting starting point for further studies on possible risk-decreasing effect of PDX on the development of colon cancer.

Inverse dose effect of pretest dietary lactose intake on breath hydrogen results and symptoms in lactase nonpersistent subjects

The aim of this study was to determine a relationship between pretest intake of lactose and outcome of lactose breath hydrogen test. Patients presented at a testing laboratory participated in the study. A 3-hour breath hydrogen, 50-g lactose challenge was carried out. Results were tabulated and patients completed a 3-day recall diet questionnaire. Daily lactose intake was independently calculated and was associated with breath hydrogen and total symptom score. Statistical analysis used Spearman's correlation, Mann-Whitney U-test and chi2 or Fisher exact test. Of 118 patients, 50% were lactose maldigesters. In these patients, measured breath hydrogen and symptom scores were significantly higher in the lowest intake group (< 5 g/d) than in the highest intake group (> 20 g/d) (P < .05). In the presumed lactose digesters, 59% experienced some symptoms during testing for unclear reasons. Pretest dietary intake of lactose inversely affects results of breath hydrogen.

Probiotics: what are they? What are their effects on gut physiology?

Probiotics can be defined as microbial cells that have a beneficial effect on the health and well-being of the host. Since the gastrointestinal mucosa is the surface of contact with probiotics, it seems evident that the first effects of probiotics relate to digestive function. A brief review of the literature indicates that probiotics have very few effects on the main physiological functions of the gastrointestinal tract, which are digestion, absorption and propulsion. The main action of probiotics can be summarised as a reinforcement of the intestinal mucosal barrier against deleterious agents. Experimental data indicate that some probiotics reduce pathological alterations in paracellular permeability to large molecules or bacteria, stimulate mucosal immunity, display a trophic action on the mucosa, reduce mucus degradation and interact with mediators of inflammation. Yoghurt may help lactose digestion, and some data needing confirmation indicate a stimulation of water absorption and an acceleration of intestinal transit by some bacteria.

Review article: lactose--a potential prebiotic

Lactose maldigestion, which affects a large majority of the world's population, has been mostly linked with uncomfortable symptoms. In addition, dairy consumption is variably blamed or recommended for a number of ill effects. There is, however, emerging evidence that certain lactic acid-producing bacteria, which selectively consume prebiotics, may be beneficial against some lower intestinal diseases. Lactose maldigestion and lactose should perhaps be re-evaluated as a potential provider of such a prebiotic. This historical and observational review discusses lactose and argues the opinion that it has prebiotic potential. Moreover, in maldigesters, natural ingestion or lack thereof may be relevant in the pathogenesis of diseases such as colorectal cancer and inflammatory bowel diseases.

Chronic consumption of fresh but not heated yogurt improves breath-hydrogen status and short-chain fatty acid profiles: a controlled study in healthy men with or without lactose maldigestion

BACKGROUND

Ingestion of fermented dairy products induces changes in the equilibrium and metabolism of the intestinal microflora and may thus have beneficial effects on the host.

OBJECTIVE

We compared the effects of chronic consumption of yogurt with (fresh) or without (heated) live bacterial cultures (Lactobacillus bulgaricus and Streptococcus thermophilus) on plasma glucose, insulin, triacylglycerols, cholesterol, fatty acids, and short-chain fatty acids.

DESIGN

Two groups of 12 healthy men with or without lactose malabsorption were selected with use of a breath-hydrogen test after a 30-g lactose load. Subjects were randomly assigned in a crossover design to 500 g/d of either fresh or heated yogurt for 2 periods of 15 d each, separated by a 15-d washout interval.

RESULTS

Chronic consumption of fresh or heated yogurt had no detrimental effects on plasma glucose, insulin, or fatty acid areas under the curve in response to acute ingestion of 500 g yogurt in healthy men with or without lactose malabsorption. There were also no detectable changes in fasting plasma glucose, insulin, fatty acid, triacylglycerol, or cholesterol concentrations. In contrast, plasma butyrate was higher (P: < 0.03) and plasma propionate tended to be higher (P: = 0.059) in subjects without lactose malabsorption after fresh yogurt consumption than after heated yogurt consumption. There were no significant changes in plasma acetate. In subjects with lactose malabsorption, 15 d of fresh yogurt consumption also increased propionate production compared with values at baseline (P: < 0.04). In the same group, the production of breath hydrogen was lower after fresh yogurt consumption than after heated yogurt consumption (P: < 0.01).

CONCLUSIONS

In men with lactose malabsorption, chronic consumption of yogurt containing live bacterial cultures ameliorated the malabsorption, as evidenced by lower breath-hydrogen excretion, but increased propionate concentrations. In subjects without lactose malabsorption, such yogurt tended to increase propionate and increased butyrate.

Lactose intolerance

Lactose maldigestion has been under intensive research since its discovery in the 1960's. We know the prevalence of lactose maldigestion in a great number of countries and ethnic groups. However, there is often no provision made for the secondary type of maldigestion, and the study populations have sometimes been selected rather than picked at random. New methods for the measurement of lactose digestion have been developed, and its genetic mechanisms have received a great deal of attention during the last few years. However, in many studies the measurement and/or reporting of symptoms has quite often been overlooked. In this review, various topics related to lactose intolerance are discussed with a special emphasis on its symptoms.

The application of ecological principles and fermentable fibers to manage the gastrointestinal tract ecosystem

Because diet can influence the structure and functions of the gastrointestinal tract, there are opportunities for using diet as a "management tool" to affect the resident microbiota. Fermentable fibers increase the densities of beneficial bacteria and stimulate growth and functions of the healthy intestine. Recent findings show that after acute diarrhea, the use of an oral electrolyte solution with the fermentable fiber oligofructose accelerates recovery of beneficial bacteria, reduces the relative abundance of detrimental bacteria, stimulates mucosal growth and enhances digestive and immune functions. This review will focus on how the principles of stream ecology can be applied to better understand the distribution of bacteria along the length of the gastrointestinal tract, the effect of diarrhea on the gastrointestinal ecosystem and how fermentable fibers can be used as a "management tool" to promote gastrointestinal health in normal states and during recovery from diarrhea.

In well-fed young rats, lactose-induced chronic diarrhea reduces the apparent absorption of vitamins A and E and affects preferentially vitamin E status

To establish the effect of lactose-induced diarrhea on the apparent absorption and status of vitamins-A and E in well-fed young rats, we fed Sprague Dawley rats a balanced diet or a lactose diet (350 g/kg). A group of rats fed the control diet equal to the level measured in the lactose-fed rats (pair-fed) was also included. The experiment lasted 23 d and feces were collected on days 4-6, 10-12, 14-16 and 20-22. Samples of serum and tissues were taken on days 10 and 23. Lactose caused a significant reduction in food intake, had no effect on body weight and produced a diarrhea that persisted during the whole experiment. The severity of diarrhea decreased with time, indicating that the rats partially adapted to lactose feeding. At the onset of diarrhea, the apparent absorption of vitamins A and E in the rats with diarrhea was significantly lower than in the control or pair-fed rats, but the rats with diarrhea recovered gradually, and in the case of vitamin E was normalized by day 15. At day 10 the rats with lactose-induced diarrhea had serum and liver concentrations of vitamins A and E that did not differ from the control or pair-fed rats. However, at day 23 the lactose-fed rats with diarrhea had significantly lower serum and liver concentrations of vitamin E than the control or pair-fed rats. Measured at that time, diarrhea had no effect on liver vitamin A, but lower serum concentrations of this vitamin were detected in both the lactose-fed rats and in the pair-fed rats. In general, in well-nourished rats, the chronic diarrhea associated with excessive dietary lactose reduced the apparent absorption of vitamin A and E and particularly compromised the nutritional status of vitamin E.