Association between functional lactase variants and a high abundance of Bifidobacterium in the gut of healthy Japanese people

Sex-Specific Associations of Gut Microbiota Composition with Sarcopenia Defined by the Asian Working Group for Sarcopenia 2019 Consensus in Older Outpatients: Prospective Cross-Sectional Study in Japan

Background/Objectives: Sarcopenia (SA), an age-related impairment in skeletal muscle mass and function, is related to gut microbiota (GM) through inflammation and short-chain fatty acid (SCFA) generation. However, data on this relationship in older Japanese adults remain limited. We investigated the relationship of GM composition with SA, based on the Asian Working Group for Sarcopenia (AWGS) 2019 criteria, among elderly Japanese outpatients. Methods: Between June 2022 and January 2023, this prospective cross-sectional study enrolled 356 community-dwelling outpatients aged ≥ 65 years at the Department of Gastroenterology, Juntendo Tokyo Koto Geriatric Medical Center. SA was determined based on the AWGS 2019 consensus criteria. GM was analyzed using 16S rRNA gene sequencing, and alpha/beta diversity, taxonomic composition, detection rates, and correlations with skeletal muscle mass index (SMI), grip strength, and gait speed were investigated. Results: Among 356 (144 males, 212 females) participants, 50 (35 males, 15 females) had SA. Differences in GM diversity and composition were primarily noted among male participants. Men with SA had lower alpha diversity and distinct beta diversity profiles. Six bacterial genera-Eubacterium I, Fusicatenibacter, Holdemanella, Unclassified Lachnospira, Enterococcus H, and Bariatricus-had lower abundances in the SA group. Several of these genera showed positive correlations with SMI, grip strength, and gait speed. Conversely, no differences in GM characteristics were seen among females. Conclusions: GM composition was associated with SA among older Japanese men. These sex-specific differences emerged consistently, highlighting the potential of microbiota-based strategies for SA prevention in older males.

Dairy Intake and All-Cause, Cancer, and Cardiovascular Disease Mortality Risk in A Large Japanese Population: A 12-Year Follow-Up of the J-MICC Study

AIM

We examined the association between dairy intake and all-cause, cancer, and cardiovascular disease mortality in a cohort of the general population followed up for 12 years across Japan.

METHODS

We conducted a longitudinal cohort study of 79,715 participants from the Japan Multi-Institutional Collaborative Cohort study (57.2% women, mean age 54.7 years old). The amount of dairy (milk and yogurt) intake was determined using a validated short-food frequency questionnaire. The hazard ratio for mortality according to sex-specific tertile of dairy intake was calculated using Cox proportional hazards regression models with adjustment for potential confounding factors and dietary factors by sex.

RESULTS

During the follow-up period (932,738 person-years), 3,723 participants died, including 2,088 cancer and 530 cardiovascular disease deaths. The highest tertile of total dairy intake (versus the lowest tertile) was associated with a 19% lower all-cause mortality risk (hazard ratio=0.81, 95% confidence interval: 0.70-0.92; P for trend=0.001) in women. Similarly, we observed inverse associations between milk intake and all-cause and cancer mortality risk in women, yogurt intake and cardiovascular disease risk in women, and yogurt intake and all-cause mortality risk in both sexes.

CONCLUSION

A higher total dairy and milk intakes in women and yogurt intake in both sexes were associated with a reduced risk of all-cause mortality in the general population across Japan during the 12-year follow-up period.

Genetic diversity of dissolved free extracellular DNA compared to intracellular DNA in wastewater treatment plants

Dissolved free extracellular DNA (free-exDNA) coexists with intracellular DNA (inDNA) in aquatic environments. Free-exDNA can be taken up by bacteria through transformation, and wastewater treatment plants (WWTPs) are positioned as potential hot spots for genetic contamination. However, studies comparing the composition of free-exDNA and inDNA is limited. This study employed colloidal adsorption and foam concentration method to recover free-exDNA from different WWTP stages and compared its diversity with inDNA via metagenomic analysis. Free-exDNA concentrations were observed to increase after chlorination. Genetic analysis revealed a higher abundance of specific genes following chlorination, suggesting that free-exDNA in effluent originated from bacterial death in secondary treated water. This result indicates that free-exDNA, which increases due to chlorination, is subsequently released into the catchment. Additionally, several high-risk antibiotic-resistance genes (ARGs) were detected that colocalized with mobile genetic elements. These ARGs were expected to have a high potential for gene transfer via transformation, and the risk was highlighted. Overall, these findings deepen our understanding of horizontal gene transfer risks in WWTPs.

Changes in the intestinal microbiota of Japanese children during the first 3.5 years of life

Human gut microbiota plays a crucial role in health and disease. Infancy is a critical period for gut microbiota maturation and immune system development and has the potential to affect long-term health. Understanding the development of gut microbiota in Japanese children is essential because of regional differences and the long-term health effects of the early gut microbiota. However, while several longitudinal studies in Japan have explored the development of the gut microbiota after birth, more extended follow-up periods are still needed. In this study, we aimed to analyze the gut microbiota of 106 Japanese mother-child pairs from the Chiba Study of Mother and Child Health, Japan, over 3.5 years. The results showed that the alpha diversity of the gut microbiota in children increased with age, and its composition began to resemble that of adults. We identified four distinct clusters of gut microbiota that reflected different maturation stages. The similarity between the maternal and child gut microbiota appeared to follow a bimodal-like distribution, suggesting that the presence of older siblings may enhance this similarity. This study highlights the dynamic nature of gut microbiota development in Japanese children and deepens our understanding of the similarities between maternal and child gut microbiota.

Genetic aspects of lactase deficiency in indigenous populations of Siberia

The ability to metabolize lactose in adulthood is associated with the persistence of lactase enzyme activity. In European populations, lactase persistence is determined mainly by the presence of the rs4988235-T variant in the MCM6 gene, which increases the expression of the LCT gene, encoding lactase. The highest rates of lactase persistence are characteristic of Europeans, and the lowest rates are found in East Asian populations. Analysis of published data on the distribution of the hypolactasia-associated variant rs4988235-C in the populations of Central Asia and Siberia showed that the frequency of this variant increases in the northeastern direction. The frequency of this allele is 87 % in Central Asia, 90.6 % in Southern Siberia, and 92.9 % in Northeastern Siberia. Consequently, the ability of the population to metabolize lactose decreases in the same geographical direction. The analysis of paleogenomic data has shown that the higher frequency of the rs4988235-T allele in populations of Central Asia and Southern Siberia is associated with the eastward spread of ancient populations of the Eastern European steppes, starting from the Bronze Age. The results of polymorphism analysis of exons and adjacent introns of the MCM6 and LCT genes in indigenous populations of Siberia indicate the possibility that polymorphic variants may potentially be related to lactose metabolism exist in East Asian populations. In East Asian populations, including Siberian ethnic groups, a ~26.5 thousand nucleotide pairs long region of the MCM6 gene, including a combination of the rs4988285-A, rs2070069-G, rs3087353-T, and rs2070068-A alleles, was found. The rs4988285 and rs2070069 loci are located in the enhancer region that regulates the activity of the LCT gene. Analysis of paleogenomic sequences showed that the genomes of Denisovans and Neanderthals are characterized by the above combination of alleles of the MCM6 gene. Thus, the haplotype discovered appears to be archaic. It could have been inherited from a common ancestor of modern humans, Neanderthals, and Denisovans, or it could have been acquired by hybridization with Denisovans or Neanderthals. The data obtained indicate a possible functional significance of archaic variants of the MCM6 gene.

Association of gut microbiota with lactose intolerance and coeliac disease: a two-sample Mendelian randomization study

Background and objectives

Lactose intolerance and coeliac disease are common clinical nutrient malabsorption disorders, with an unclear pathogenesis and limited therapeutic options. It is widely believed that the gut microbiota plays an important role in many digestive disorders, but its role in lactose intolerance and coeliac disease is not yet clear. This study aimed to investigate the correlation between gut microbiota and lactose intolerance and coeliac disease.

Materials and methods

This study utilized the genome-wide association study database to investigate the association between gut microbiota and lactose intolerance and coeliac disease using Mendelian randomization (MR). The robustness of our findings was confirmed through subsequent analyses including Cochrane's Q statistic, MR-Egger Intercept Regression, MR-PRESSO Global Test and Leave-one-out methods.

Results

By employing the inverse variance weighted method, we identified that family Veillonellaceae, genus Oxalobacter and Senegalimassilia were protective against lactose intolerance, whereas genus Anaerotruncus, Eubacterium rectale group and Ruminococcus2 were found to be risk factors for lactose intolerance. Regarding coeliac disease, class Bacilli and Gammaproteobacteria, family FamilyXIII and Veillonellaceae, genus Eisenbergiella, Lachnoclostridium, RuminococcaceaeUCG014 and Ruminococcus2 were identified as protective factors, while class Betaproteobacteria, genus Eubacterium xylanophilum group and Blautia were risk factors. Furthermore, reverse the MR analysis did not reveal any evidence of a causal relationship between lactose intolerance or coeliac disease and the bacteria identified in our study.

Conclusion

This study provides novel insights into exploring the role of gut microbiota in lactose intolerance and coeliac disease; however, further experiments investigations are required to elucidate the specific underlying mechanisms.

Genetic architecture and correlations between the gut microbiome and gut gene transcription in Chinook salmon (Oncorhynchus tshawytscha)

Population divergence through selection can drive local adaptation in natural populations which has implications for the effective restoration of declining and extirpated populations. However, adaptation to local environmental conditions is complicated when both the host and its associated microbiomes must respond via co-evolutionary change. Nevertheless, for adaptation to occur through selection, variation in both host and microbiome traits should include additive genetic effects. Here we focus on host immune function and quantify factors affecting variation in gut immune gene transcription and gut bacterial community composition in early life-stage Chinook salmon (Oncorhynchus tshawytscha). Specifically, we utilized a replicated factorial breeding design to determine the genetic architecture (sire, dam and sire-by-dam interaction) of gut immune gene transcription and microbiome composition. Furthermore, we explored correlations between host gut gene transcription and microbiota composition. Gene transcription was quantified using nanofluidic qPCR arrays (22 target genes) and microbiota composition using 16 S rRNA gene (V5-V6) amplicon sequencing. We discovered limited but significant genetic architecture in gut microbiota composition and transcriptional profiles. We also identified significant correlations between gut gene transcription and microbiota composition, highlighting potential mechanisms for functional interactions between the two. Overall, this study provides support for the co-evolution of host immune function and their gut microbiota in Chinook salmon, a species recognized as locally adapted. Thus, the inclusion of immune gene transcription profile and gut microbiome composition as factors in the development of conservation and commercial rearing practices may provide new and more effective approaches to captive rearing.

Gut microbiome composition reveals the distinctiveness between the Bengali people and the Indigenous ethnicities in Bangladesh

Ethnicity has a significant role in shaping the composition of the gut microbiome, which has implications in human physiology. This study intends to investigate the gut microbiome of Bengali people as well as several indigenous ethnicities (Chakma, Marma, Khyang, and Tripura) residing in the Chittagong Hill Tracts areas of Bangladesh. Following fecal sample collection from each population, part of the bacterial 16 s rRNA gene was amplified and sequenced using Illumina NovaSeq platform. Our findings indicated that Bangladeshi gut microbiota have a distinct diversity profile when compared to other countries. We also found out that Bangladeshi indigenous communities had a higher Firmicutes to Bacteroidetes ratio than the Bengali population. The investigation revealed an unclassified bacterium that was differentially abundant in Bengali samples while the genus Alistipes was found to be prevalent in Chakma samples. Further research on these bacteria might help understand diseases associated with these populations. Also, the current small sample-sized pilot study hindered the comprehensive understanding of the gut microbial diversity of the Bangladeshi population and its potential health implications. However, our study will help establish a basic understanding of the gut microbiome of the Bangladeshi population.

Intestinal Bacteria Fluctuating in Early-Stage Colorectal Cancer Carcinogenesis are Associated with Diet in Healthy Adults

This hospital-based, cross-sectional study aimed to explore the association between diet and fluctuating intestinal bacteria in early-stage colorectal cancer (CRC) (Atopobium parvulum, Actinomyces odontolyticus, Solobacterium moorei, and Bifidobacterium longum). Healthy participants (n = 212) who underwent total colonoscopy at National Cancer Center Hospital (Tokyo, Japan) were divided into two groups according to the relative abundance of bacteria in their feces: those in the top 25% of relative bacterial abundance as cases and the bottom 25% as controls. The participants were divided into three groups (low, medium, and high) according to their intake of food groups associated with CRC. Multivariable logistic regression analysis was conducted to estimate the association between dietary intake and higher relative abundance of bacteria. Dairy products were inversely associated with a higher relative abundance of A. parvulum, A. odontolyticus, and S. moorei, with odds ratios (high vs. low) and 95% confidence interval as follows: 0.16 (0.06-0.44), 0.25 (0.08-0.82), and 0.29 (0.11-0.78), respectively. Additionally, dietary fiber was inversely associated with a higher relative abundance of S.moorei (0.29 [0.11-0.78]). No association was observed between diet and B.longum. In conclusion, healthy adults with a higher intake of dairy products and fiber had lower odds of having a higher relative abundance of CRC-associated microbiota.

Genetically Determined Circulating Lactase/Phlorizin Hydrolase Concentrations and Risk of Colorectal Cancer: A Two-Sample Mendelian Randomization Study

Previous research has found that milk is associated with a decreased risk of colorectal cancer (CRC). However, it is unclear whether the milk digestion by the enzyme lactase-phlorizin hydrolase (LPH) plays a role in CRC susceptibility. Our study aims to investigate the direct causal relationship of CRC risk with LPH levels by applying a two-sample Mendelian Randomization (MR) strategy. Genetic instruments for LPH were derived from the Fenland Study, and CRC-associated summary statistics for these instruments were extracted from the FinnGen Study, PLCO Atlas Project, and Pan-UK Biobank. Primary MR analyses focused on a cis-variant (rs4988235) for LPH levels, with results integrated via meta-analysis. MR analyses using all variants were also undertaken. This analytical approach was further extended to assess CRC subtypes (colon and rectal). Meta-analysis across the three datasets illustrated an inverse association between genetically predicted LPH levels and CRC risk (OR: 0.92 [95% CI, 0.89-0.95]). Subtype analyses revealed associations of elevated LPH levels with reduced risks for both colon (OR: 0.92 [95% CI, 0.89-0.96]) and rectal cancer (OR: 0.92 [95% CI, 0.87, 0.98]). Consistency was observed across varied analytical methods and datasets. Further exploration is warranted to unveil the underlying mechanisms and validate LPH's potential role in CRC prevention.

Metagenomic gut microbiome analysis of Japanese patients with multiple chemical sensitivity/idiopathic environmental intolerance

BACKGROUND

Although the pathology of multiple chemical sensitivity (MCS) is unknown, the central nervous system is reportedly involved. The gut microbiota is important in modifying central nervous system diseases. However, the relationship　between the gut microbiota and MCS remains unclear. This study aimed to identify gut microbiota variations associated with MCS using shotgun metagenomic sequencing of fecal samples.

METHODS

We prospectively recruited 30 consecutive Japanese female patients with MCS and analyzed their gut microbiomes using shotgun metagenomic sequencing. The data were compared with metagenomic data obtained from 24 age- and sex-matched Japanese healthy controls (HC).

RESULTS

We observed no significant difference in alpha and beta diversity of the gut microbiota between the MCS patients and HC. Focusing on the important changes in the literatures, at the genus level, Streptococcus, Veillonella, and Akkermansia were significantly more abundant in MCS patients than in HC (p < 0.01, p < 0.01, p = 0.01, respectively, fold change = 4.03, 1.53, 2.86, respectively). At the species level, Akkermansia muciniphila was significantly more abundant (p = 0.02, fold change = 3.3) and Faecalibacterium prausnitzii significantly less abundant in MCS patients than in HC (p = 0.03, fold change = 0.53). Functional analysis revealed that xylene and dioxin degradation pathways were significantly enriched (p < 0.01, p = 0.01, respectively, fold change = 1.54, 1.46, respectively), whereas pathways involved in amino acid metabolism and synthesis were significantly depleted in MCS (p < 0.01, fold change = 0.96). Pathways related to antimicrobial resistance, including the two-component system and cationic antimicrobial peptide resistance, were also significantly enriched in MCS (p < 0.01, p < 0.01, respectively, fold change = 1.1, 1.2, respectively).

CONCLUSIONS

The gut microbiota of patients with MCS shows dysbiosis and alterations in bacterial functions related to exogenous chemicals and amino acid metabolism and synthesis. These findings may contribute to the further development of treatment for MCS.

TRIAL REGISTRATION

This study was registered with the University Hospital Medical Information Clinical Trials Registry as UMIN000031031. The date of first trial registration: 28/01/2018.

Milk and dairy product intakes, intestinal bacteria, and respiratory infections in children of elementary school age and older in Japan

OBJECTIVES

The aim of this study was to examine the associations between milk and dairy product intakes, intestinal bacteria, and respiratory infections in children of elementary school age and older in Japan.

METHODS

We conducted cross-sectional surveys each year from 2013 to 2015 for grades 2, 5, and 8 students of an elementary and junior high school (n = 1020). Exclusion owing to ineligibility regarding data on dietary intake, respiratory infections, and intestinal bacteria led to 922 participants for the analyses. Dietary intake was assessed with a self-administered food frequency questionnaire. Respiratory infections occurring ≥ 4 episodes over the past year were determined based on the caregivers' reports. Intestinal bacteria (species and counts) were analyzed with real-time polymerase chain reaction. Logistic regression models were used to estimate the odds ratios (ORs) and 95% CIs.

RESULTS

The odds of ≥ 4 respiratory infection episodes decreased with higher milk intake after adjusting for potential confounders, and the ORs (95% CIs) for the second and third tertile categories, compared with the first tertile category, were 0.91 (0.58-1.42) and 0.48 (0.29-0.77), respectively (P for trend = 0.001). A decreasing trend in the ORs for lactic acid drink intake was observed only in those with a low count of intestinal Faecalibacterium prausnitzii.

CONCLUSIONS

We found that higher milk intake was inversely associated with respiratory infections in children older than preschool age. Higher lactic acid drink intake could be inversely associated only in children with a low F. prausnitzii count in the intestine.

Revealing Joseon period People's single nucleotide polymorphism associated with lactase gene by ancient DNA analysis of human remains from archaeological sites in Korea

Lactase non-persistence (LNP), one of the causes of lactose intolerance, is related to lactase gene associated single nucleotide polymorphisms (SNPs). Since the frequency of LNP varies by ethnic group and country, the research to reveal the presence or absence of LNP for specific people has been conducted worldwide. However, in East Asia, the study of lactase gene associated SNPs have not been sufficiently examined so far using ancient human specimens from archaeological sites. In our study of Joseon period human remains (n=14), we successfully revealed genetic information of lactase gene associated SNPs (rs1679771596, rs41525747, rs4988236, rs4988235, rs41380347, rs869051967, rs145946881 and rs182549), further confirming that as for eight SNPs, the pre-modern Korean people had a lactase non-persistent genotype. Our report contributes to the establishment of LNP associated SNP analysis technique that can be useful in forthcoming studies on human bones and mummy samples from East Asian archaeological sites.

Dysbiosis of the Fecal and Biliary Microbiota in Biliary Tract Cancer

Characteristic bile duct and gut microbiota have been identified in patients with chronic biliary tract disease. This study aimed to characterize the fecal and bile microbiota in biliary tract cancer (BTC) patients and their relationship. Patients with BTC (n = 30) and benign biliary disease (BBD) without cholangitis (n = 11) were included. Ten healthy, age-matched subjects were also recruited for fecal microbiota comparison. The fecal and bile duct microbiotas were analyzed by sequencing the 16S rRNA gene V3-V4 region. Live bacteria were obtained in the bile from three BTC patients by culture, and metagenomics-based identification was performed. Linear discriminant analysis effect size showed a higher Enterobacteriaceae abundance and a lower Clostridia abundance, including that of Faecalibacterium and Coprococcus, in the BTC patients than in the other subjects. Ten of 17 operational taxonomic units (OTUs) assigned to Enterobacteriaceae in the bile were matched with the OTUs found in the BTC subject fecal samples. Furthermore, a bile-isolated strain possessed the carcinogenic bacterial colipolyketide synthase-encoding gene. Enterobacteriaceae was enriched in the BTC feces, and more than half of Enterobacteriaceae in the bile matched that in the feces at the OTU level. Our data suggests that fecal microbiota dysbiosis may contribute to BTC onset.

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.

Effect of Various Preterm Infant Milk Formulas on NEC-Like Gut Injury in Mice

Formula feeding is an important risk factor for the development of necrotizing enterocolitis in preterm infants. The potential harmful effects of different preterm formulas on the developing intestinal tract remain incompletely understood. Here we demonstrate that feeding newborn mouse pups with various preterm formulas resulted in differing effects on intestinal inflammation, apoptosis, and activation of the pro-inflammatory transcription factor NFκB. 16S rRNA sequencing revealed that each preterm formula resulted in significant gut microbial alterations that were different from dam-fed controls. Formula feeding with EleCare and Similac Special Care caused greater intestinal injury compared to NeoSure. Pre-treatment with Lactobacillus rhamnosus GG ameliorated severity of intestinal injury from EleCare and Similac Special Care. Our findings indicate that not all preterm formulas are the same, and different formulations can have varying effects on intestinal inflammation, apoptosis, and microbiome composition.

Seven-year incidence of new-onset hypertension by frequency of dairy intake among survivors of the Great East Japan Earthquake

Survivors of natural disasters are at a high risk of cardiovascular disease. Behavioral risk factors, including modifiable diet, need to be identified. Thus far, the association between dairy intake and new-onset hypertension among these survivors is unknown. Therefore, we investigated this relationship. We conducted a longitudinal cohort study of 4475 survivors of the Great East Japan Earthquake in 2011 who participated in a 7-year follow-up survey. New-onset hypertension was assessed using annual health checkup data. Information on the frequency of dairy intake was obtained using a self-report questionnaire. The hazard ratio for developing hypertension according to the frequency of dairy intake was calculated using Cox proportional hazards regression models. The total number of person-years observed was 20,042, with a median follow-up of 5.4 years. During the observation period, 1554 individuals developed hypertension. The multivariable-adjusted hazard ratios of new-onset hypertension were significantly lower in those who consumed dairy products once per day (0.82, 95% confidence interval 0.71-0.94) and twice or more times per day (0.84, 95% confidence interval 0.71-0.99) than in nonconsumers; the inverse linear trend was marginally significant (P = 0.083). This association was not affected by lipid metabolism and was consistent across subgroups by sex, age, behavioral factors, cardiometabolic factors, and housing type due to the disaster. A higher frequency of dairy intake was associated with a lower risk of new-onset hypertension in community-dwelling survivors of earthquakes and tsunamis. Dietary guidance involving dairy intake could reduce the risk of developing hypertension among these survivors.

Gut microbiota in various childhood disorders: Implication and indications

Gut microbiota has a significant role in gut development, maturation, and immune system differentiation. It exerts considerable effects on the child's physical and mental development. The gut microbiota composition and structure depend on many host and microbial factors. The host factors include age, genetic pool, general health, dietary factors, medication use, the intestine's pH, peristalsis, and transit time, mucus secretions, mucous immunoglobulin, and tissue oxidation-reduction potentials. The microbial factors include nutrient availability, bacterial cooperation or antagonism, and bacterial adhesion. Each part of the gut has its microbiota due to its specific characteristics. The gut microbiota interacts with different body parts, affecting the pathogenesis of many local and systemic diseases. Dysbiosis is a common finding in many childhood disorders such as autism, failure to thrive, nutritional disorders, coeliac disease, Necrotizing Enterocolitis, helicobacter pylori infection, functional gastrointestinal disorders of childhood, inflammatory bowel diseases, and many other gastrointestinal disorders. Dysbiosis is also observed in allergic conditions like atopic dermatitis, allergic rhinitis, and asthma. Dysbiosis can also impact the development and the progression of immune disorders and cardiac disorders, including heart failure. Probiotic supplements could provide some help in managing these disorders. However, we are still in need of more studies. In this narrative review, we will shed some light on the role of microbiota in the development and management of common childhood disorders.

Effects of 4G-beta-D-Galactosylsucrose in patients with depression: A randomized, double-blinded, placebo-controlled, parallel-group comparative study

Advances in genetic research on microbiome have led to several trials on the effectiveness of synbiotics or probiotics in patients with depression; however, none have evaluated the efficacy of prebiotics. 4G-beta-D-Galactosylsucrose (Lactosucrose, LS) is selectively assimilated by Bifidobacterium as a prebiotic and improves microbiome diversity. However, as it is not clear if LS consumption can improve symptoms of depression, we investigated whether LS intake can improve depressive symptoms, quality of life (QOL), and self-efficacy by conducting a single cite, double-blinded, randomized controlled trial in 20 outpatients with depressive episodes (F32, ICD-10) for 24 weeks. Participants (age range, 36-72 years) were randomized to the LS (n = 9) or placebo groups (n = 11). Primary outcome was improvement in total Montgomery Asberg Depression Rating Scale (MADRS) score, and the secondary outcomes were MADRS subscores, global self-efficacy scale (GSES) score, World Health Organization QOL (WHO/QOL-26) score, and 16S rRNA analysis of the fecal microbiome. LS consumption did not significantly improve total MADRS scores (-2 (-16 to 16) vs 0 (-6 to 10), p = 0.552), but GSES tended to improve in the LS group (2.00 ± 4.24 vs -1.36 ± 4.15, p = 0.091) with a large effect size (Cohen's d = 0.802). Sequencing of 16S rRNA revealed individual-level differences in microbiome diversity changes due to the intervention. Thus, we show that LS intake can improve self-efficacy, but not depressive symptoms, even in a small sample. Additional studies that also regulate diet and ensure adherence may help determine a correlation between depression and the gut microbiome.

FODMAPs, inflammatory bowel disease and gut microbiota: updated overview on the current evidence

PURPOSE

Based on the fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) hypothesis, the low-FODMAP diet has been suggested as a potential therapeutic approach for inflammatory bowel disease (IBD) with promising results on disease management. However, this diet implies a specific broad food restriction, which potentially increases the risk of nutritional deficiencies and may aggravate gut microbiota dysbiosis of IBD patients. The aim of the present study is to review the effect of individual FODMAPs on the human gut microbiota. In addition, this narrative review provides an updated overview of the use of the low-FODMAP diet in IBD, namely the implementation, advantages, limitations, and the impact on the gut microbiota.

METHODS

The literature search strategy was applied to PubMed and Web of Science using relevant keywords, IBD, FODMAPs, Fructose, Lactose, Polyols, FOS, GOS, low-FODMAP diet and gut microbiota.

RESULTS

Current data suggest that the low-FODMAP diet may effectively improve clinical outcomes in the management of IBD and ensure better quality of life for IBD patients. However, there is evidence highlighting some issues of concern, particularly the adequacy of the diet and the impact on the gut microbiota. The various FODMAP types differently modulate the gut microbiota.

CONCLUSION

IBD management should be achieved with the least possible dietary restriction to avoid detrimental consequences, particularly on nutritional adequacy and gut microbiota. Thus, it is important to individualize and monitor the nutrition intervention. Further studies are required to better characterize the relationship between diet, the gut microbiota, and IBD to support the generalization of this approach for clinical practice in IBD therapy and management.

Probiotic Bifidobacterium breve Prevents Memory Impairment Through the Reduction of Both Amyloid-β Production and Microglia Activation in APP Knock-In Mouse

BACKGROUND

Probiotic supplementation reestablishes microbiome diversity and improves brain function in Alzheimer's disease (AD); their molecular mechanisms, however, have not yet been fully illustrated.

OBJECTIVE

We investigated the effects of orally supplemented Bifidobacterium breve MCC1274 on cognitive function and AD-like pathologies in AppNL-G-F mice.

METHODS

Three-month-old AppNL-G-F mice were orally supplemented with B. breve MCC1274 for four months. The short-term memory function was evaluated using a novel object recognition test. Amyloid plaques, amyloid-β (Aβ) levels, Aβ fibril, amyloid-β protein precursor and its processing enzymes, its metabolic products, glial activity, and cell proliferation in the subgranular zone of the dentate gyrus were evaluated by immunohistochemistry, Aβ ELISA, western blotting, and immunofluorescence staining. The mRNA expression levels of pro- and anti-inflammatory cytokines were determined by qRT-PCR analysis.

RESULTS

We found that the oral B. breve MCC1 274 supplementation prevented memory impairment in AppNL-G-F mice and decreased hippocampal Aβ levels through the enhancement of the a-disintegrin and metalloproteinase 10 (ADAM10) level. Moreover, administration of the probiotic activated the ERK/HIF-1α signaling pathway responsible for increasing the ADAM10 level and also attenuated microglial activation, which in turn led to reduction in the mRNA expression levels of pro-inflammatory cytokines in the brain. In addition, B. breve MCC1274 supplementation increased the level of synaptic proteins in the hippocampus.

CONCLUSION

Our findings support the possibility that oral B. breve MCC1274 supplementation might be used as a potential preventive therapy for AD progression.

Subjective, but not documented, lactose intolerance accompanies irritable bowel syndrome

Introduction

Lactose intolerance, due to lactase deficiency, may overlap with the symptoms of irritable bowel syndrome (IBS) or lead to an incorrect diagnosis of IBS. Identification of lactose intolerance and lactase deficiency enables targeted treatment to be implemented.

The aim of the study was to search for a frequency of a lactose intolerance symptoms in patients with IBS, depending on the results of hydrogen breath test (HBT).

Materials and Methods

The study involved 56 patients with IBS and 23 healthy people. Both, IBS patients and healthy controls, were asked to complete a survey about IBS symptoms and tolerance of lactose-containing products. A HBT was performed on all subjects.

Results

Lactase deficiency was diagnosed in 60.7% of patients with IBS and 43.5% of control group. The differences between the study groups were not statistically significant. No statistically significant differences were observed between the incidence of lactase deficiency depending on the type of IBS.

In the group of patients with IBS and normal HBT results, as well as in patients with IBS and lactase deficiency, there were no statistically significant differences in the frequency of lactose intolerance symptoms. However, among people with normal HBT results, patients with IBS reported symptoms of intolerance after consuming lactose-containing foods significantly more often compared to the control group (p<0.05).

Conclusions

Frequency of lactase deficiency does not differ between IBS patients and healthy individuals. Patients with IBS are more likely to report symptoms of lactose intolerance, regardless of the HBT result, compared to healthy individuals.

Does Direct-to-Consumer Personal Genetic Testing Improve Gynecological Cancer Screening Uptake among Never-Screened Attendees? A Randomized Controlled Study

The clinical impact of direct-to-consumer genetic testing (DTC-GT) on health behavior change has remained controversial. The aim of this study is to clarify the short-term effects of DTC-GT on gynecological cancer screening uptake among middle-aged never-screened Japanese women in a randomized controlled trial (RCT). A total of 144 women aged 45-50 who had never undergone gynecological cancer screening were randomly selected to receive health education (control group), or health education and DTC-GT (intervention group), at a 1:1 ratio. We compared the gynecological screening uptake during the follow-up period. Furthermore, to estimate the impact of learning of an elevated genetic cancer risk in the intervention group, we conducted an analysis dichotomized by genetic risk category. A total of 139 women completed the one-year follow-up survey (69 in the control group and 70 in the intervention group). The follow-up period did not differ between control and intervention groups (the median follow-up period was 276 days and 279 days, respectively, p = 0.746). There were 7 (9.7%) women in the control group and 10 (13.9%) in the intervention group who attended breast cancer screening (p = 0.606), and 9 (12.5%) women from both groups attended cervical cancer screening (p = 1.000). Likewise, there were no significant differences in cancer screening uptake in the analysis stratified by risk category within the intervention group. In conclusion, there was no significant effect of DTC-GT on gynecological cancer screening uptake in this RCT setting. Increasing cancer screening attendance may require a combination of well-established intervention strategies and DTC-GT. Clinical Trial Registration: UMIN-CTR Identifier, UMIN000031709.

The Spanish gut microbiome reveals links between microorganisms and Mediterranean diet

Despite the increasing evidence of links between human gut and health, the number of gut microbiomes that have been studied to date at a country level are surprisingly low. Mediterranean countries, including some of the most long-lived and healthy countries in the world, have not been considered so far in those studies at a large scale. The main objective of this work is to characterize the gut microbiome of a healthy adult population of a Mediterranean, paradigmatically healthy country: Spain. Stool samples from 530 healthy volunteers were collected, total metagenomic DNA extracted, and the microbial profiles determined through 16S rRNA metataxonomic sequencing. Our results confirm the associations between several microbial markers and different variables, including sex, age, BMI and diet choices, and bring new insights into the relationship between microbiome and diet in the Spanish population. Remarkably, some of the associations found, such as the decrease of Faecalibacterium with age or the link of Flavonifractor with less healthy dietary habits, have been barely noticed in other large-scale cohorts. On the other hand, a range of links between microorganisms, diet, and lifestyle coincide with those reported in other populations, thus increasing the robustness of such associations and confirming the importance of these microbial markers across different countries. Overall, this study describes the Spanish "normal" microbiome, providing a solid baseline for future studies investigating the effects of gut microbiome composition and deviations in the adherence to the Mediterranean diet.

Xylan utilisation promotes adaptation of Bifidobacterium pseudocatenulatum to the human gastrointestinal tract

Dietary carbohydrates impact the composition of the human gut microbiota. However, the relationship between carbohydrate availability for individual bacteria and their growth in the intestinal environment remains unclear. Here, we show that the availability of long-chain xylans (LCX), one of the most abundant dietary fibres in the human diet, promotes the growth of Bifidobacterium pseudocatenulatum in the adult human gut. Genomic and phenotypic analyses revealed that the availability of LCX-derived oligosaccharides is a fundamental feature of B. pseudocatenulatum, and that some but not all strains possessing the endo-1,4-β-xylanase (BpXyn10A) gene grow on LCX by cleaving the xylose backbone. The BpXyn10A gene, likely acquired by horizontal transfer, was incorporated into the gene cluster for LCX-derived oligosaccharide utilisation. Co-culturing with xylanolytic Bacteroides spp. demonstrated that LCX-utilising strains are more competitive than LCX non-utilising strains even when LCX-derived oligosaccharides were supplied. In LCX-rich dietary interventions in adult humans, levels of endogenous B. pseudocatenulatum increased only when BpXyn10A was detected, indicating that LCX availability is a fitness determinant in the human gut. Our findings highlight the enhanced intestinal adaptability of bifidobacteria via polysaccharide utilisation, and provide a cornerstone for systematic manipulation of the intestinal microbiota through dietary intervention using key enzymes that degrade polysaccharide as biomarkers.

Lipid and Energy Metabolism of the Gut Microbiota Is Associated with the Response to Probiotic Bifidobacterium breve Strain for Anxiety and Depressive Symptoms in Schizophrenia

A recent meta-analysis found that probiotics have moderate-to-large beneficial effects on depressive symptoms in patients with psychiatric disorders. However, it remains unclear how the baseline gut microbiota before probiotic administration influences the host’s response to probiotics. Therefore, we aimed to determine whether the predicted functional profile of the gut microbiota influences the effectiveness of probiotic treatment in patients with schizophrenia. A total of 29 patients with schizophrenia consumed Bifidobacterium breve A-1 (synonym B. breve MCC1274) for 4 weeks. We considered patients who showed a 25% or more reduction in the Hospital Anxiety and Depression Scale total score at 4 weeks from baseline to be “responders” and those who did not to be “non-responders”. We predicted the gut microbial functional genes based on 16S rRNA gene sequences and applied the linear discriminant analysis effect size method to determine the gut microbial functional genes most likely to explain the differences between responders and non-responders at baseline. The results showed that lipid and energy metabolism was elevated at baseline in responders (n = 12) compared to non-responders (n = 17). These findings highlight the importance of assessing the gut microbial functional genes at baseline before probiotic therapy initiation in patients with psychiatric disorders.

Comprehensive analysis of gut microbiota of a healthy population and covariates affecting microbial variation in two large Japanese cohorts

Background

Inter-individual variations in gut microbiota composition are observed even among healthy populations. The gut microbiota may exhibit a unique composition depending on the country of origin and race of individuals. To comprehensively understand the link between healthy gut microbiota and host state, it is beneficial to conduct large-scale cohort studies. The aim of the present study was to elucidate the integrated and non-redundant factors associated with gut microbiota composition within the Japanese population by 16S rRNA sequencing of fecal samples and questionnaire-based covariate analysis.

Results

A total of 1596 healthy Japanese individuals participated in this study via two independent cohorts, NIBIOHN cohort (n=954) and MORINAGA cohort (n=642). Gut microbiota composition was described and the interaction of these microorganisms with metadata parameters such as anthropometric measurements, bowel habits, medical history, and lifestyle were obtained. Thirteen genera, including Alistipes, Anaerostipes, Bacteroides, Bifidobacterium, Blautia, Eubacterium halli group, Faecalibacterium, Fusicatenibacter, Lachnoclostridium, Parabacteroides, Prevotella_9, Roseburia, and Subdoligranulum were predominant among the two cohorts. On the basis of univariate analysis for overall microbiome variation, 18 matching variables exhibited significant association in both cohorts. A stepwise redundancy analysis revealed that there were four common covariates, Bristol Stool Scale (BSS) scores, gender, age, and defecation frequency, displaying non-redundant association with gut microbial variance.

Conclusions

We conducted a comprehensive analysis of gut microbiota in healthy Japanese individuals, based on two independent cohorts, and obtained reliable evidence that questionnaire-based covariates such as frequency of bowel movement and specific dietary habit affects the microbial composition of the gut. To our knowledge, this was the first study to investigate integrated and non-redundant factors associated with gut microbiota among Japanese populations.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02215-0.

The Role of Gut Barrier Dysfunction and Microbiome Dysbiosis in Colorectal Cancer Development

Accumulating evidence indicates that breakdown of the+ protective mucosal barrier of the gut plays a role in colorectal cancer (CRC) development. Inflammation and oxidative stress in the colonic epithelium are thought to be involved in colorectal carcinogenesis and the breakdown of the integrity of the colonic barrier may increase the exposure of colonocytes to toxins from the colonic milieu, enhancing inflammatory processes and release of Reactive Oxygen Species (ROS). The aetiological importance of the gut microbiome and its composition - influenced by consumption of processed meats, red meats and alcoholic drinks, smoking, physical inactivity, obesity - in CRC development is also increasingly being recognized. The gut microbiome has diverse roles, such as in nutrient metabolism and immune modulation. However, microbial encroachment towards the colonic epithelium may promote inflammation and oxidative stress and even translocation of species across the colonic lumen. Recent research suggests that factors that modify the above mechanisms, e.g., obesity and Western diet, also alter gut microbiota, degrade the integrity of the gut protective barrier, and expose colonocytes to toxins. However, it remains unclear how obesity, lifestyle and metabolic factors contribute to gut-barrier integrity, leading to metabolic disturbance, colonocyte damage, and potentially to CRC development. This review will discuss the interactive roles of gut-barrier dysfunction, microbiome dysbiosis, and exposure to endogenous toxins as another mechanism in CRC development, and how biomarkers of colonic mucosal barrier function may provide avenues for disease, prevention and detection.

Association between the prevalence of hypertension and dairy consumption by housing type among survivors of the Great East Japan Earthquake

Survivors of the Great East Japan Earthquake in 2011 had higher risks of cardiovascular diseases and hypertension, particularly residents of heavy flooding areas and evacuees. Thus far, the association between the prevalence of hypertension and dairy consumption remains unknown among these evacuees. We investigated this association by housing type after the Great East Japan Earthquake. In this cross-sectional study, we conducted a baseline survey among 9569 survivors of the earthquake, aged ≥18 years, between September 2011 and February 2012. Hypertension was defined as a systolic/diastolic blood pressure ≥140/90 mmHg or as persons undergoing treatment for high blood pressure. The frequency of dairy consumption was determined using a questionnaire. Participants living in prefabricated housing and emergency shelters were regarded as residents of temporary housing. Hypertension was prevalent among 43.8% and 44.7% of the participants in temporary and non-temporary housing, respectively. A logistic regression analysis of the prevalence of hypertension by daily dairy consumption showed that the magnitude of multivariable-adjusted odds ratios differed according to housing type (odds ratio, 0.64; 95% confidence interval, 0.51-0.80 in temporary housing; odds ratio, 0.85; 95% confidence interval, 0.73-0.995 in non-temporary housing; P for interaction = 0.0501). These associations were consistent across subgroups according to sex, age, behavioral factors, obesity, disorders of lipid metabolism, and economic status. A higher frequency of dairy consumption was associated with a lower prevalence of hypertension among community-dwelling survivors of earthquakes and tsunamis, particularly those living in temporary housing. Therefore, dietary therapy involving dairy consumption could help prevent hypertension among evacuees.

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.

Genome-wide association studies and heritability analysis reveal the involvement of host genetics in the Japanese gut microbiota

Numerous host extrinsic and intrinsic factors affect the gut microbiota composition, but their cumulative effects do not sufficiently explain the variation in the microbiota, suggesting contributions of missing factors. The Japanese population possesses homogeneous genetic features suitable for genome-wide association study (GWAS). Here, we performed GWASs for human gut microbiota using 1068 healthy Japanese adults. To precisely evaluate genetic effects, we corrected for the impacts of numerous host extrinsic and demographic factors by introducing them as covariates, enabling us to discover five loci significantly associated with microbiome diversity measures: HS3ST4, C2CD2, 2p16.1, 10p15.1, and 18q12.2. Nevertheless, these five variants explain only a small fraction of the variation in the gut microbiota. We subsequently investigated the heritability of each of the 21 core genera and found that the abundances of six genera are heritable. We propose that the gut microbiota composition is affected by a highly polygenic architecture rather than several strongly associated variants in the Japanese population.

Lactose intolerance in patients with inflammatory bowel diseases and dietary management in prevention of osteoporosis

Lactose intolerance affects 33% to 75% of the world population and may be associated with various genetic factors. Lactose in the diet can be found in milk and dairy products, which simultaneously constitute the primary sources of calcium. Gut microbiota also influences lactose tolerance. Patients with lactose intolerance often stop consuming milk and dairy products, which may lead to calcium and vitamin deficiency and osteoporosis. Insufficient production of lactase also occurs in patients with diseases of the gastrointestinal tract, such as inflammatory bowel diseases. Moreover, Crohn's disease and ulcerative colitis are risk factors for osteoporosis, and the intake of the proper amount of calcium is an essential element in preventing the decrease of bone mineral density. Diet may prevent the development of osteoporosis, thus, educating patients regarding proper diet should constitute a part of the treatment and prevention process. Patients should consume low-lactose, or lactose-free milk and bacterially fermented dairy products. Additionally, plant milk supplemented by calcium and vitamin D, mineral water with calcium, and certain vegetables also may be good sources of calcium.

Impact of host genetics on gut microbiome: Take-home lessons from human and mouse studies

The intestinal microbiome has emerged as an important component involved in various diseases. Therefore, the interest in understanding the factors shaping its composition is growing. The gut microbiome, often defined as a complex trait, contains diverse components and its properties are determined by a combination of external and internal effects. Although much effort has been invested so far, it is still difficult to evaluate the extent to which human genetics shape the composition of the gut microbiota. However, in mouse studies, where the environmental factors are better controlled, the effect of the genetic background was significant. The purpose of this paper is to provide a current assessment of the role of human host genetics in shaping the gut microbiome composition. Despite the inconsistency of the reported results, it can be estimated that the genetic factor affects a portion of the microbiome. However, this effect is currently lower than the initial estimates, and it is difficult to separate the genetic influence from the environmental effect. Additionally, despite the differences between the microbial composition of humans and mice, results from mouse models can strengthen our knowledge of host genetics underlying the human gut microbial variation.

Mini-Review on the Possible Interconnections between the Gut-Brain Axis and the Infertility-Related Neuropsychiatric Comorbidities

Both the gut-brain axis (GBA) and the hypothalamic–pituitary–adrenal (HPA) axis remain an intriguing yet obscure network with a strong influence over other systems of organs. Recent reports have sought to describe the multitude of harmful stressors that may impact the HPA axis along with the interconnections between these. This has improved our knowledge of how the underlying mechanisms working to establish homeostasis are affected. A disruption to the HPA axis can amplify the chances of gastrointestinal deficiencies, whilst also increasing the risk of a wide spectrum of neuropsychiatric disorders. Thus, the influence of microorganisms found throughout the digestive tract possess the ability to affect both physiology and behaviour by triggering responses, which may be unfavourable. This is sometimes the case in of infertility. Numerous supplements have been formulated with the intention of rebalancing the gut microflora. Accordingly, the gut flora may alter the pharmacokinetics of drugs used as part of fertility treatments, potentially exacerbating the predisposition for various neurological disorders, regardless of the age and gender.

Enzymatic Adaptation of Bifidobacterium bifidum to Host Glycans, Viewed from Glycoside Hydrolyases and Carbohydrate-Binding Modules

Certain species of the genus Bifidobacterium represent human symbionts. Many studies have shown that the establishment of symbiosis with such bifidobacterial species confers various beneficial effects on human health. Among the more than ten (sub)species of human gut-associated Bifidobacterium that have significantly varied genetic characteristics at the species level, Bifidobacterium bifidum is unique in that it is found in the intestines of a wide age group, ranging from infants to adults. This species is likely to have adapted to efficiently degrade host-derived carbohydrate chains, such as human milk oligosaccharides (HMOs) and mucin O-glycans, which enabled the longitudinal colonization of intestines. The ability of this species to assimilate various host glycans can be attributed to the possession of an adequate set of extracellular glycoside hydrolases (GHs). Importantly, the polypeptides of those glycosidases frequently contain carbohydrate-binding modules (CBMs) with deduced affinities to the target glycans, which is also a distinct characteristic of this species among members of human gut-associated bifidobacteria. This review firstly describes the prevalence and distribution of B. bifidum in the human gut and then explains the enzymatic machinery that B. bifidum has developed for host glycan degradation by referring to the functions of GHs and CBMs. Finally, we show the data of co-culture experiments using host-derived glycans as carbon sources, which underpin the interesting altruistic behavior of this species as a cross-feeder.

The Importance of Lactose in the Human Diet: Outcomes of a Mexican Consensus Meeting

Lactose is a unique component of breast milk, many infant formulas and dairy products, and is widely used in pharmaceutical products. In spite of that, its role in human nutrition or lactose intolerance is generally not well-understood. For that reason, a 2-day-long lactose consensus meeting with health care professionals was organized in Mexico to come to a set of statements for which consensus could be gathered. Topics ranging from lactase expression to potential health benefits of lactose were introduced by experts, and that was followed by a discussion on concept statements. Interestingly, lactose does not seem to induce a neurological reward response when consumed. Although lactose digestion is optimal, it supplies galactose for liver glycogen synthesis. In infants, it cannot be ignored that lactose-derived galactose is needed for the synthesis of glycosylated macromolecules. At least beyond infancy, the low glycemic index of lactose might be metabolically beneficial. When lactase expression decreases, lactose maldigestion may lead to lactose intolerance symptoms. In infancy, the temporary replacing of lactose by other carbohydrates is only justified in case of severe intolerance symptoms. In those who show an (epi)genetic decrease or absence of lactase expression, a certain amount (for adults mostly up to 12 g per portion) of lactose can still be consumed. In these cases, lactose shows beneficial intestinal-microbiota-shaping effects. Avoiding lactose-containing products may imply a lower intake of other important nutrients, such as calcium and vitamin B12 from dairy products, as well as an increased intake of less beneficial carbohydrates.

Update on lactose malabsorption and intolerance: pathogenesis, diagnosis and clinical management

Lactose is the main source of calories in milk, an essential nutriedigestion, patients with visceral hypersensitivity nt in infancy and a key part of the diet in populations that maintain the ability to digest this disaccharide in adulthood. Lactase deficiency (LD) is the failure to express the enzyme that hydrolyses lactose into galactose and glucose in the small intestine. The genetic mechanism of lactase persistence in adult Caucasians is mediated by a single C→T nucleotide polymorphism at the LCTbo -13'910 locus on chromosome-2. Lactose malabsorption (LM) refers to any cause of failure to digest and/or absorb lactose in the small intestine. This includes primary genetic and also secondary LD due to infection or other conditions that affect the mucosal integrity of the small bowel. Lactose intolerance (LI) is defined as the onset of abdominal symptoms such as abdominal pain, bloating and diarrhoea after lactose ingestion by an individual with LM. The likelihood of LI depends on the lactose dose, lactase expression and the intestinal microbiome. Independent of lactose digestion, patients with visceral hypersensitivity associated with anxiety or the Irritable Bowel Syndrome (IBS) are at increased risk of the condition. Diagnostic investigations available to diagnose LM and LI include genetic, endoscopic and physiological tests. The association between self-reported LI, objective findings and clinical outcome of dietary intervention is variable. Treatment of LI can include low-lactose diet, lactase supplementation and, potentially, colonic adaptation by prebiotics. The clinical outcome of these treatments is modest, because lactose is just one of a number of poorly absorbed carbohydrates which can cause symptoms by similar mechanisms.

Associations of gut microbiota, dietary intake, and serum short-chain fatty acids with fecal short-chain fatty acids

In recent years, short-chain fatty acids (SCFAs) have been reported to play an important role in maintaining human health. Fecal SCFA concentrations correlate well with colonic SCFA status and gut microbiota composition. However, the associations with the gut microbiota functional pathway, dietary intake, blood SCFAs, and fecal SCFAs remain uncertain. To clarify these relationships, we collected fecal samples, blood samples, and dietary habit data from 12 healthy adults aged 22–51 years. The relative abundance of several SCFA-producing bacteria, gut microbiota diversity, and functional pathways related to SCFA biosynthesis were positively associated with fecal SCFAs even after adjusting for age and sex. Furthermore, fecal acetate was likely to be positively associated with serum acetate. By contrast, dietary intake was not associated with fecal SCFAs. Overall, the present study highlights the potential usefulness of fecal SCFAs as an indicator of the gut microbiota ecosystem and dynamics of SCFAs in the human body.