Microbial co-occurrence complicates associations of gut microbiome with US immigration, dietary intake and obesity

Advancing microbiome research in Māori populations: insights from recent literature exploring the gut microbiomes of underrepresented and Indigenous peoples

The gut microbiome plays vital roles in human health, including mediating metabolism, immunity, and the gut-brain axis. Many ethnicities remain underrepresented in gut microbiome research, with significant variation between Indigenous and non-Indigenous peoples due to dietary, socioeconomic, health, and urbanization differences. Although research regarding the microbiomes of Indigenous peoples is increasing, Māori microbiome literature is lacking despite widespread inequities that Māori populations face. These inequities likely contribute to gut microbiome differences that exacerbate negative health outcomes. Characterizing the gut microbiomes of underrepresented populations is necessary to inform efforts to address health inequities. However, for microbiome research to be culturally responsible and meaningful, study design must improve to better protect the rights and interests of Indigenous peoples. Here, we discuss barriers to Indigenous participation in research and the role disparities may play in shaping the gut microbiomes of Indigenous peoples, with a particular focus on implications for Māori and areas for improvement.

Psychosocial and neurobiological aspects of the worldwide refugee crisis: From vulnerability to resilience

Anisman, H., Doubad, D., Asokumar, A. & Matheson, K. Psychosocial and neurobiological aspects of the worldwide refugee crisis: From vulnerability to resilience. NEUROSCI BIOBEHAV REV, XXXX. Immigration occurs between countries either to obtain employment, for family reunification or to escape violence and other life-threatening conditions. Refugees and asylum seekers are often obligated to overcome a uniquely challenging set of circumstances prior to and during migration. Settlement following immigration may pose yet another set of stressors related to acculturation to the host country, as well as financial insecurity, discrimination, language barriers, and social isolation. Here we discuss the multiple consequences of immigration experiences, focusing on the health disturbances that frequently develop in adults and children. Aside from the psychosocial influences, immigration-related challenges may cause hormonal, inflammatory immune, and microbiota changes that favor psychological and physical illnesses. Some biological alterations are subject to modification by epigenetic changes, which have implications for intergenerational trauma transmission, as might disruptions in parenting behaviors and family dysfunction. Despite the hardships experienced, many immigrants and their families exhibit positive psychological adjustment after resettlement. We provide information to diminish the impacts associated with immigration and offer strength-based approaches that may foster resilience.

Natural Foraging Selection and Gut Microecology of Two Subterranean Rodents from the Eurasian Steppe in China

As the most abundant group of mammals, rodents possess a very rich ecotype, which makes them ideal for studying the relationship between diet and host gut microecology. Zokors are specialized herbivorous rodents adapted to living underground. Unlike more generalized herbivorous rodents, they feed on the underground parts of grassland plants. There are two species of the genus Myospalax in the Eurasian steppes in China: one is Myospalax psilurus, which inhabits meadow grasslands and forest edge areas, and the other is M. aspalax, which inhabits typical grassland areas. How are the dietary choices of the two species adapted to long-term subterranean life, and what is the relationship of this diet with gut microbes? Are there unique indicator genera for their gut microbial communities? Relevant factors, such as the ability of both species to degrade cellulose, are not yet clear. In this study, we analyzed the gut bacterial communities and diet compositions of two species of zokors using 16S amplicon technology combined with macro-barcoding technology. We found that the diversity of gut microbial bacterial communities in M. psilurus was significantly higher than that in M. aspalax, and that the two species of zokors possessed different gut bacterial indicator genera. Differences in the feeding habits of the two species of zokors stem from food composition rather than diversity. Based on the results of Mantel analyses, the gut bacterial community of M. aspalax showed a significant positive correlation with the creeping-rooted type food, and there was a complementary relationship between the axis root-type-food- and the rhizome-type-food-dominated (containing bulb types and tuberous root types) food groups. Functional prediction based on KEGG found that M. psilurus possessed a stronger degradation ability in the same cellulose degradation pathway. Neutral modeling results show that the gut flora of the M. psilurus has a wider ecological niche compared to that of the M. aspalax. This provides a new perspective for understanding how rodents living underground in grassland areas respond to changes in food conditions.

Blood metabolomic shift links diet and gut microbiota to multiple health outcomes among Hispanic/Latino immigrants in the U.S

Immigrants from less industrialized countries who are living in the U.S. often bear an elevated risk of multiple disease due to the adoption of a U.S. lifestyle. Blood metabolome holds valuable information on environmental exposure and the pathogenesis of chronic diseases, offering insights into the link between environmental factors and disease burden. Analyzing 634 serum metabolites from 7,114 Hispanics (1,141 U.S.-born, 5,973 foreign-born) in the Hispanic Community Health Study/Study of Latinos (HCHS/SOL), we identified profound blood metabolic shift during acculturation. Machine learning highlighted the prominent role of non-genetic factors, especially food and gut microbiota, in these changes. Immigration-related metabolites correlated with plant-based foods and beneficial gut bacteria for foreign-born Hispanics, and with meat-based or processed food and unfavorable gut bacteria for U.S.-born Hispanics. Cardiometabolic traits, liver, and kidney function exhibited a link with immigration-related metabolic changes, which were also linked to increased risk of diabetes, severe obesity, chronic kidney disease, and asthma.

Graphical abstract

Highlights

A substantial proportion of identified blood metabolites differ between U.S.-born and foreign-born Hispanics/Latinos in the U.S.Food and gut microbiota are the major modifiable contributors to blood metabolomic difference between U.S.-born and foreign-born Hispanics/Latinos.U.S. nativity related metabolites collectively correlate with a spectrum of clinical traits and chronic diseases.

Dietary Acculturation Is Associated With Altered Gut Microbiome, Circulating Metabolites, and Cardiovascular Disease Risk in US Hispanics and Latinos: Results From HCHS/SOL

BACKGROUND

Dietary acculturation, or adoption of dominant culture diet by migrant groups, influences human health. We aimed to examine dietary acculturation and its relationships with cardiovascular disease (CVD), gut microbiota, and blood metabolites among US Hispanic and Latino adults.

METHODS

In the HCHS/SOL (Hispanic Community Health Study/Study of Latinos), US exposure was defined by years in the United States (50 states and Washington, DC) and US nativity. A dietary acculturation pattern was derived from 14 172 participants with two 24-hour dietary recalls at baseline (2008-2011) using least absolute shrinkage and selection operator regression, with food groups as predictors of US exposure. We evaluated associations of dietary acculturation with incident CVD across ≈7 years of follow-up (n=211/14 172 cases/total) and gut microbiota (n=2349; visit 2, 2014 to 2017). Serum metabolites associated with both dietary acculturation-related gut microbiota (n=694) and incident CVD (n=108/5256 cases/total) were used as proxy measures to assess the association of diet-related gut microbiome with incident CVD.

RESULTS

We identified an empirical US-oriented dietary acculturation score that increased with US exposure. Higher dietary acculturation score was associated with higher risk of incident CVD (hazard ratio per SD, 1.33 [95% CI, 1.13-1.57]), adjusted for sociodemographic, lifestyle, and clinical factors. Sixty-nine microbial species (17 enriched from diverse species, 52 depleted mainly from fiber-utilizing Clostridia and Prevotella species) were associated with dietary acculturation, driven by lower intakes of whole grains, beans, and fruits and higher intakes of refined grains. Twenty-five metabolites, involved predominantly in fatty acid and glycerophospholipid metabolism (eg, branched-chain 14:0 dicarboxylic acid** and glycerophosphoethanolamine), were associated with both diet acculturation-related gut microbiota and incident CVD. Proxy association analysis based on these metabolites suggested a positive relationship between diet acculturation-related microbiome and risk of CVD (r=0.70, P<0.001).

CONCLUSIONS

Among US Hispanic and Latino adults, greater dietary acculturation was associated with elevated CVD risk, possibly through alterations in gut microbiota and related metabolites. Diet and microbiota-targeted interventions may offer opportunities to mitigate CVD burdens of dietary acculturation.

Metagenomic and metabolomic analysis showing the adverse risk-benefit trade-off of the ketogenic diet

BACKGROUND

Ketogenic diets are increasingly popular for addressing obesity, but their impacts on the gut microbiota and metabolome remain unclear. This paper aimed to investigate how a ketogenic diet affects intestinal microorganisms and metabolites in obesity.

METHODS

Male mice were provided with one of the following dietary regimens: normal chow, high-fat diet, ketogenic diet, or high-fat diet converted to ketogenic diet. Body weight and fat mass were measured weekly using high-precision electronic balances and minispec body composition analyzers. Metagenomics and non-targeted metabolomics data were used to analyze differences in intestinal contents.

RESULTS

Obese mice on the ketogenic diet exhibited notable improvements in weight and body fat. However, these were accompanied by a significant decrease in intestinal microbial diversity, as well as an increase in Firmicutes abundance and a 247% increase in the Firmicutes/Bacteroidetes ratio. The ketogenic diet also altered multiple metabolic pathways in the gut, including glucose, lipid, energy, carbohydrate, amino acid, ketone body, butanoate, and methane pathways, as well as bacterial secretion and colonization pathways. These changes were associated with increased intestinal inflammation and dysbiosis in obese mice. Furthermore, the ketogenic diet enhanced the secretion of bile and the synthesis of aminoglycoside antibiotics in obese mice, which may impair the gut microbiota and be associated with intestinal inflammation and immunity.

CONCLUSIONS

The study suggest that the ketogenic diet had an unfavorable risk-benefit trade-off and may compromise metabolic homeostasis in obese mice.

Gut microbiota, blood metabolites, and left ventricular diastolic dysfunction in US Hispanics/Latinos

BACKGROUND

Left ventricular diastolic dysfunction (LVDD) is an important precursor of heart failure (HF), but little is known about its relationship with gut dysbiosis and microbial-related metabolites. By leveraging the multi-omics data from the Hispanic Community Health Study/Study of Latinos (HCHS/SOL), a study with population at high burden of LVDD, we aimed to characterize gut microbiota associated with LVDD and identify metabolite signatures of gut dysbiosis and incident LVDD.

RESULTS

We included up to 1996 Hispanic/Latino adults (mean age: 59.4 years; 67.1% female) with comprehensive echocardiography assessments, gut microbiome, and blood metabolome data. LVDD was defined through a composite criterion involving tissue Doppler assessment and left atrial volume index measurements. Among 1996 participants, 916 (45.9%) had prevalent LVDD, and 212 out of 594 participants without LVDD at baseline developed incident LVDD over a median 4.3 years of follow-up. Using multivariable-adjusted analysis of compositions of microbiomes (ANCOM-II) method, we identified 7 out of 512 dominant gut bacterial species (prevalence > 20%) associated with prevalent LVDD (FDR-q < 0.1), with inverse associations being found for Intestinimonas_massiliensis, Clostridium_phoceensis, and Bacteroide_coprocola and positive associations for Gardnerella_vaginali, Acidaminococcus_fermentans, Pseudomonas_aeruginosa, and Necropsobacter_massiliensis. Using multivariable adjusted linear regression, 220 out of 669 circulating metabolites with detection rate > 75% were associated with the identified LVDD-related bacterial species (FDR-q < 0.1), with the majority being linked to Intestinimonas_massiliensis, Clostridium_phoceensis, and Acidaminococcus_fermentans. Furthermore, 46 of these bacteria-associated metabolites, mostly glycerophospholipids, secondary bile acids, and amino acids, were associated with prevalent LVDD (FDR-q < 0.1), 21 of which were associated with incident LVDD (relative risk ranging from 0.81 [p = 0.001, for guanidinoacetate] to 1.25 [p = 9 × 10-5, for 1-stearoyl-2-arachidonoyl-GPE (18:0/20:4)]). The inclusion of these 21 bacterial-related metabolites significantly improved the prediction of incident LVDD compared with a traditional risk factor model (the area under the receiver operating characteristic curve [AUC] = 0.73 vs 0.70, p = 0.001). Metabolite-based proxy association analyses revealed the inverse associations of Intestinimonas_massilliensis and Clostridium_phoceensis and the positive association of Acidaminococcus_fermentans with incident LVDD.

CONCLUSION

In this study of US Hispanics/Latinos, we identified multiple gut bacteria and related metabolites linked to LVDD, suggesting their potential roles in this preclinical HF entity. Video Abstract.

Associations of Fecal Microbiota with Ectopic Fat in African Caribbean Men

OBJECTIVE

The gut microbiome has been associated with visceral fat (VAT) in European and Asian populations; however, associations with VAT and with ectopic fats among African-ancestry individuals are not known. Our objective was to investigate cross-sectional associations of fecal microbiota diversity and composition with VAT and ectopic fat, as well as body mass index (BMI), among middle-aged and older African Caribbean men.

METHODS

We included in our analysis n = 193 men (mean age = 62.2 ± 7.6 years; mean BMI = 28.3 ± 4.9 kg/m2) from the Tobago Health Study. We assessed fecal microbiota using V4 16s rRNA gene sequencing. We evaluated multivariable-adjusted associations of microbiota features (alpha diversity, beta diversity, microbiota differential abundance) with BMI and with computed tomography-measured VAT and ectopic fats (pericardial and intermuscular fat; muscle and liver attenuation).

RESULTS

Lower alpha diversity was associated with higher VAT and BMI, and somewhat with higher pericardial and liver fat. VAT, BMI, and pericardial fat each explained similar levels of variance in beta diversity. Gram-negative Prevotellaceae and Negativicutes microbiota showed positive associations, while gram-positive Ruminococcaceae microbiota showed inverse associations, with ectopic fats.

CONCLUSIONS

Fecal microbiota features associated with measures of general adiposity also extend to metabolically pernicious VAT and ectopic fat accumulation in older African-ancestry men.

Gut Microbiota and Blood Metabolites Related to Fiber Intake and Type 2 Diabetes

BACKGROUND

Consistent evidence suggests diabetes-protective effects of dietary fiber intake. However, the underlying mechanisms, particularly the role of gut microbiota and host circulating metabolites, are not fully understood. We aimed to investigate gut microbiota and circulating metabolites associated with dietary fiber intake and their relationships with type 2 diabetes (T2D).

METHODS

This study included up to 11 394 participants from the HCHS/SOL (Hispanic Community Health Study/Study of Latinos). Diet was assessed with two 24-hour dietary recalls at baseline. We examined associations of dietary fiber intake with gut microbiome measured by shotgun metagenomics (350 species/85 genera and 1958 enzymes; n=2992 at visit 2), serum metabolome measured by untargeted metabolomics (624 metabolites; n=6198 at baseline), and associations between fiber-related gut bacteria and metabolites (n=804 at visit 2). We examined prospective associations of serum microbial-associated metabolites (n=3579 at baseline) with incident T2D over 6 years.

RESULTS

We identified multiple bacterial genera, species, and related enzymes associated with fiber intake. Several bacteria (eg, Butyrivibrio, Faecalibacterium) and enzymes involved in fiber degradation (eg, xylanase EC3.2.1.156) were positively associated with fiber intake, inversely associated with prevalent T2D, and favorably associated with T2D-related metabolic traits. We identified 159 metabolites associated with fiber intake, 47 of which were associated with incident T2D. We identified 18 of these 47 metabolites associated with the identified fiber-related bacteria, including several microbial metabolites (eg, indolepropionate and 3-phenylpropionate) inversely associated with the risk of T2D. Both Butyrivibrio and Faecalibacterium were associated with these favorable metabolites. The associations of fiber-related bacteria, especially Faecalibacterium and Butyrivibrio, with T2D were attenuated after further adjustment for these microbial metabolites.

CONCLUSIONS

Among United States Hispanics/Latinos, dietary fiber intake was associated with favorable profiles of gut microbiota and circulating metabolites for T2D. These findings advance our understanding of the role of gut microbiota and microbial metabolites in the relationship between diet and T2D.

The role of gut microbiota in the occurrence and progression of non-alcoholic fatty liver disease

Background

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent cause of chronic liver disease worldwide, and gut microbes are associated with the development and progression of NAFLD. Despite numerous studies exploring the changes in gut microbes associated with NAFLD, there was no consistent pattern of changes.

Method

We retrieved studies on the human fecal microbiota sequenced by 16S rRNA gene amplification associated with NAFLD from the NCBI database up to April 2023, and re-analyzed them using bioinformatic methods.

Results

We finally screened 12 relevant studies related to NAFLD, which included a total of 1,189 study subjects (NAFLD, n = 654; healthy control, n = 398; obesity, n = 137). Our results revealed a significant decrease in gut microbial diversity with the occurrence and progression of NAFLD (SMD = -0.32; 95% CI -0.42 to -0.21; p < 0.001). Alpha diversity and the increased abundance of several crucial genera, including Desulfovibrio, Negativibacillus, and Prevotella, can serve as an indication of their predictive risk ability for the occurrence and progression of NAFLD (all AUC > 0.7). The occurrence and progression of NAFLD are significantly associated with higher levels of LPS biosynthesis, tryptophan metabolism, glutathione metabolism, and lipid metabolism.

Conclusion

This study elucidated gut microbes relevance to disease development and identified potential risk-associated microbes and functional pathways associated with NAFLD occurrence and progression.

The intersection of social determinants of health, the microbiome, and health outcomes in immigrants: A scoping review

In the present scoping review, we explore whether existing evidence supports the premise that social determinants of health (SDoH) affect immigrant health outcomes through their effects on the microbiome. We adapt the National Institute on Minority Health and Health Disparities' research framework to propose a conceptual model that considers the intersection of SDoH, the microbiome, and health outcomes in immigrants. We use this conceptual model as a lens through which to explore recent research about SDoH, biological factors associated with changes to immigrants' microbiomes, and long-term health outcomes. In the 17 articles reviewed, dietary acculturation, physical activity, ethnicity, birthplace, age at migration and length of time in the host country, socioeconomic status, and social/linguistic acculturation were important determinants of postmigration microbiome-related transformations. These factors are associated with progressive shifts in microbiome profile with time in host country, increasing the risks for cardiometabolic, mental, immune, and inflammatory disorders and antibiotic resistance. The evidence thus supports the premise that SDoH influence immigrants' health postmigration, at least in part, through their effects on the microbiome. Omission of important postmigration social-ecological variables (e.g., stress, racism, social/family relationships, and environment), limited research among minoritized subgroups of immigrants, complexity and inter- and intra-individual differences in the microbiome, and limited interdisciplinary and biosocial collaboration restrict our understanding of this area of study. To identify potential microbiome-based interventions and promote immigrants' well-being, more research is necessary to understand the intersections of immigrant health with factors from the biological, behavioral/psychosocial, physical/built environment, and sociocultural environment domains at all social-ecological levels.

Variant of the lactase LCT gene explains association between milk intake and incident type 2 diabetes

Cow's milk is frequently included in the human diet, but the relationship between milk intake and type 2 diabetes (T2D) remains controversial. Here, using data from the Hispanic Community Health Study/Study of Latinos, we show that in both sexes, higher milk intake is associated with lower risk of T2D in lactase non-persistent (LNP) individuals (determined by a variant of the lactase LCT gene, single nucleotide polymorphism rs4988235 ) but not in lactase persistent individuals. We validate this finding in the UK Biobank. Further analyses reveal that among LNP individuals, higher milk intake is associated with alterations in gut microbiota (for example, enriched Bifidobacterium and reduced Prevotella) and circulating metabolites (for example, increased indolepropionate and reduced branched-chain amino acid metabolites). Many of these metabolites are related to the identified milk-associated bacteria and partially mediate the association between milk intake and T2D in LNP individuals. Our study demonstrates a protective association between milk intake and T2D among LNP individuals and a potential involvement of gut microbiota and blood metabolites in this association.

Migration Spurs Changes in the Human Microbiome: a Review

International migration often results in major changes in living environments and lifestyles, and these changes may lead to the observed increases in obesity and diabetes among foreign-born people after resettling in higher-income countries. A possible mechanism linking changes in living environments to the onset of health conditions may be changes in the microbiome. Previous research has shown that unfavorable changes in the composition of the microbiome can increase disposition to diseases such as diabetes, obesity, kidney disease, and inflammatory bowel disease. We investigated the relationship between human migration and microbiome composition through a review using microbiome- and migration-related search terms in PubMed and Web of Science. We included articles examining the gut, oral, or oropharyngeal microbiome in people who migrated internationally. Nine articles met eligibility criteria. All but one examined migration from a non-Western to a Western country. Four of these found a difference in the microbiome of migrants compared with non-migrating residents of their country of birth, seven found differences in the microbiome of migrants compared with the native-born population in the country of resettlement, and five found microbiome differences associated with duration of stay in the country of resettlement. Microbiome composition varies with country of birth, age at migration, time since immigration, and country of resettlement. The results suggest that migration may lead to changes in the microbiome; thus, microbiome characteristics are a plausible pathway to examine changes in health after resettlement in a new country.

The global human gut microbiome: genes, lifestyles, and diet

A growing number of human gut microbiome studies consistently describe differences between human populations. Here, we review how factors related to host genetics, ethnicity, lifestyle, and geographic location help explain this variation. Studies from contrasting environmental scenarios point to diet and lifestyle as the most influential. The effect of human migration and displacement demonstrates how the microbiome adapts to newly adopted lifestyles and contributes to the profound biological and health consequences attributed to migration. This information strongly suggests against a universal scale for healthy or dysbiotic gut microbiomes, and prompts for additional microbiome population surveys, particularly from less industrialized nations. Considering these important differences will be critical for designing strategies to diagnose and restore dysbiosis in various human populations.

Human microbiome variation associated with race and ethnicity emerges as early as 3 months of age

Human microbiome variation is linked to the incidence, prevalence, and mortality of many diseases and associates with race and ethnicity in the United States. However, the age at which microbiome variability emerges between these groups remains a central gap in knowledge. Here, we identify that gut microbiome variation associated with race and ethnicity arises after 3 months of age and persists through childhood. One-third of the bacterial taxa that vary across caregiver-identified racial categories in children are taxa reported to also vary between adults. Machine learning modeling of childhood microbiomes from 8 cohort studies (2,756 samples from 729 children) distinguishes racial and ethnic categories with 87% accuracy. Importantly, predictive genera are also among the top 30 most important taxa when childhood microbiomes are used to predict adult self-identified race and ethnicity. Our results highlight a critical developmental window at or shortly after 3 months of age when social and environmental factors drive race and ethnicity-associated microbiome variation and may contribute to adult health and health disparities.

Diet Quality and the Fecal Microbiota in Adults in the American Gut Project

BACKGROUND

The Dietary Guidelines for Americans advises on dietary intake to meet nutritional needs, promote health, and prevent diseases. Diet affects the intestinal microbiota and is increasingly linked to health. It is vital to investigate the relationships between diet quality and the microbiota to better understand the impact of nutrition on human health.

OBJECTIVES

This study aimed to investigate the differences in fecal microbiota composition in adults from the American Gut Project based on their adherence to the Dietary Guidelines for Americans.

METHODS

This study was a cross-sectional analysis of the 16S sequencing and food frequency data of a subset of adults (n = 432; age = 18-60 y; 65% female, 89% white) participating in the crowdsourced American Gut Project. The Healthy Eating Index-2015 assessed the compliance with Dietary Guideline recommendations. The cohort was divided into tertiles based on Healthy Eating Index-2015 scores, and differences in taxonomic abundances and diversity were compared between high and low scorers.

RESULTS

The mean Total Score for low-scoring adults (58.1 ± 5.4) was comparable with the reported score of the average American adult (56.7). High scorers for the Total Score and components related to vegetables, grains, and dairy had greater alpha diversity than low scorers. High scorers in the fatty acid component had a lower alpha diversity than low scorers (95% CI: 0.35, 1.85). A positive log-fold difference in abundance of plant carbohydrate-metabolizing taxa in the families Lachnospiraceae and Ruminococcaceae was observed in high-scoring tertiles for Total Score, vegetable, fruit, and grain components (Benjamini-Hochberg; q < 0.05).

CONCLUSIONS

Adults with greater compliance to the Dietary Guidelines demonstrated higher diversity in their fecal microbiota and greater abundance of bacteria capable of metabolizing complex carbohydrates, providing evidence on how Dietary Guidelines support the gut microbiota.

Comparative Analysis of Fecal Microbiota in Vegetarians and Omnivores

Diet has a significant impact on fecal microbiota, which in turn plays an important role in human health. To evaluate the impact of dietary habits on fecal microbiota, we investigated the fecal microbial composition in vegetarians and omnivores using 16S rRNA gene sequencing, and estimated the correlation between fecal microbiota, body mass and diet. The dietary data showed that vegetarians consumed more plant-based foods rich in dietary fiber, omnivores consumed more animal-based foods rich in fat and overweight and obese people consumed more high-energy foods. Compared to omnivores, vegetarians had greater richness and diversity in their fecal microbiota. The Firmicutes/Bacteroidetes ratio was lower and the Prevotella/Bacteroides ratio was higher in vegetarians. The meat intake correlated positively with the proportion of Bacteroides and negatively with the proportion of Prevotella. The composition and diversity in fecal microbiota in the normal weight group, overweight group and obesity group were similar to that of vegetarians and omnivores, respectively. This paper revealed the distinctive characteristics of fecal microbiota in vegetarians and omnivores. The omnivorous diet contained more fat, which reduced the fecal microbial diversity, and was more likely to lead to being overweight or obese.

Characterization of gut microbiota associated with metabolic syndrome and type-2 diabetes mellitus in Mexican pediatric subjects

BACKGROUND

Childhood obesity is a serious public health concern that confers a greater risk of developing important comorbidities such as MetS and T2DM. Recent studies evidence that gut microbiota may be a contributing factor; however, only few studies exist in school-age children. Understanding the potential role of gut microbiota in MetS and T2DM pathophysiology from early stages of life might contribute to innovative gut microbiome-based interventions that may improve public health. The main objective of the present study was to characterize and compare gut bacteria of T2DM and MetS children against control subjects and determine which microorganisms might be potentially related with cardiometabolic risk factors to propose gut microbial biomarkers that characterize these conditions for future development of pre-diagnostic tools.

RESULTS

Stool samples from 21 children with T2DM, 25 with MetS, and 20 controls (n = 66) were collected and processed to conduct 16S rDNA gene sequencing. α- and β-diversity were studied to detect microbial differences among studied groups. Spearman correlation was used to analyze possible associations between gut microbiota and cardiometabolic risk factors, and linear discriminant analyses (LDA) were conducted to determine potential gut bacterial biomarkers. T2DM and MetS showed significant changes in their gut microbiota at genus and family level. Read relative abundance of Faecalibacterium and Oscillospora was significantly higher in MetS and an increasing trend of Prevotella and Dorea was observed from the control group towards T2DM. Positive correlations were found between Prevotella, Dorea, Faecalibacterium, and Lactobacillus with hypertension, abdominal obesity, high glucose levels, and high triglyceride levels. LDA demonstrated the relevance of studying least abundant microbial communities to find specific microbial communities that were characteristic of each studied health condition.

CONCLUSIONS

Gut microbiota was different at family and genus taxonomic levels among controls, MetS, and T2DM study groups within children from 7 to 17 years old, and some communities seemed to be correlated with relevant subjects' metadata. LDA helped to find potential microbial biomarkers, providing new insights regarding pediatric gut microbiota and its possible use in the future development of gut microbiome-based predictive algorithms.

Human microbiome variance is underestimated

Most of the variance in the human microbiome remains unexplained. Although an extensive list of individual lifestyles shaping the microbiome has been identified, important gaps in knowledge persist. Most human microbiome data are from individuals living in socioeconomically developed countries. This may have skewed the interpretation of microbiome variance and its relationship to health and disease. Moreover, striking under-representation of minority groups in microbiome studies is a missed opportunity to assess context, history and the changing nature of the microbiome in relation to the risk of disease. Therefore, we focus here on areas of recent progress - ageing and ethnicity - both of which contribute to microbiome variance with particular lessons for the promise of microbiome-based diagnostics and therapeutics.

Urbanisation and its Associated Factors Affecting Human Gut Microbiota: Where are we Heading to?

ContextThe continuous rise in urbanisation and its associated factors have been reflected in the structure of the human gut ecosystem.ObjectiveThe main focus of the review is to discuss and summarise the major risk factors associated with urbanisation that affects human gut microbiota thus affecting human health.MethodsMultiple medical literature databases, namely PubMed, Google, Google Scholar, and Web of Science were used to find relevant materials for urbanization and its major factors affecting human gut microbiota/microbiome. Both layman and Medical Subject Headings (MeSH) terms were used in the search. Due to the scarcity of the data, no limitation was set on the publication date. Relevant material in the English language which includes case reports, chapters of books, journal articles, online news reports and medical records was included in this review.ResultsBased on the data discussed in the review, it is quite clear that urbanisation and its associated factors have long-standing effects on the human gut microbiota that result in alterations of gut microbial diversity and composition. This is a matter of serious concern as chronic inflammatory diseases are on the rise in urbanised societies.ConclusionA better understanding of the factors associated with urbanisation will help us to identify and implement new biological and social approaches to prevent and treat diseases and improve health globally by deepening our understanding of these relationships and increasing studies across urbanisation gradients.HIGHLIGHTSHuman gut microbiota has been linked to almost every important function, including metabolism, intestinal homeostasis, immune system, biosynthesis of vitamins, brain processes, and its behaviour.However, dysbiosis i.e., alteration in the composition and diversity of gut microbiota is associated with the pathogenesis of many chronic conditions.In the 21st century, urbanisation represents a major demographic shift in developed and developing countries.During this period of urbanisation, humans have been exposed to many environmental exposures, all of which have led to the dysbiosis of human gut microbiota.The main focus of the review is to discuss and summarize the major risk factors associated with urbanisation and how it affects the diversity and composition of gut microbiota which ultimately affects human health.

The different trends in the burden of neurological and mental disorders following dietary transition in China, the USA, and the world: An extension analysis for the Global Burden of Disease Study 2019

Introduction

The highly processed western diet is substituting the low-processed traditional diet in the last decades globally. Increasing research found that a diet with poor quality such as western diet disrupts gut microbiota and increases the susceptibility to various neurological and mental disorders, while a balanced diet regulates gut microbiota and prevents and alleviates the neurological and mental disorders. Yet, there is limited research on the association between the disease burden expanding of neurological and mental disorders with a dietary transition.

Methods

We compared the disability-adjusted life-years (DALYs) trend by age for neurological and mental disorders in China, in the United States of America (USA), and across the world from 1990 to 2019, evaluated the dietary transition in the past 60 years, and analyzed the association between the burden trend of the two disorders with the changes in diet composition and food production.

Results

We identified an age-related upward pattern in disease burden in China. Compared with the USA and the world, the Chinese neurological and mental disorders DALY percent was least in the generation over 75 but rapidly increased in younger generations and surpassed the USA and/or the world in the last decades. The age-related upward pattern in Chinese disease burdens had not only shown in the presence of cardiovascular diseases, neoplasms, and diabetes mellitus but also appeared in the presence of depressive disorders, Parkinson's disease, Alzheimer's disease and other dementias, schizophrenia, headache disorders, anxiety disorders, conduct disorders, autism spectrum disorders, and eating disorders, successively. Additionally, the upward trend was associated with the dramatic dietary transition including a reduction in dietary quality and food production sustainability, during which the younger generation is more affected than the older. Following the increase in total calorie intake, alcohol intake, ratios of animal to vegetal foods, and poultry meat to pulses, the burdens of the above diseases continuously rose. Then, following the rise of the ratios of meat to pulses, eggs to pulses, and pork to pulses, the usage of fertilizers, the farming density of pigs, and the burdens of the above disease except diabetes mellitus were also ever-increasing. Even the usage of pesticides was positively correlated with the burdens of Parkinson's disease, schizophrenia, cardiovascular diseases, and neoplasms. Contrary to China, the corresponding burdens of the USA trended to reduce with the improvements in diet quality and food production sustainability.

Discussion

Our results suggest that improving diet quality and food production sustainability might be a promising way to stop the expanding burdens of neurological and mental disorders.

Slowly Digestible Carbohydrate Diet Ameliorates Hyperglycemia and Hyperlipidemia in High-Fat Diet/Streptozocin-Induced Diabetic Mice

Objective

Given that the prevalence rate of type 2 diabetes mellitus (T2DM) continues to increase, it is important to find an effective method to prevent or treat this disease. Previous studies have shown that dietary intervention with a slowly digestible carbohydrate (SDC) diet can improve T2DM with almost no side effects. However, the underlying mechanisms of SDC protect against T2DM remains to be elucidated.

Methods

The T2DM mice model was established with a high-fat diet and streptozocin injection. Then, SDC was administered for 6 weeks. Bodyweight, food intake, organ indices, fasting blood glucose (FBG), oral glucose tolerance test (OGTT), homeostasis model assessment for insulin resistance (HOMA-IR), and other biochemical parameters were measured. Histopathological and lipid accumulation analyses were performed, and the glucose metabolism-related gene expressions in the liver and skeletal muscle were determined. Lastly, colonic microbiota was also analyzed.

Results

SDC intervention alleviated the weight loss in the pancreas, lowered blood glucose and glycosylated hemoglobin levels, and improved glucose tolerance and HOMA-IR. SDC intervention improved serum lipid profile, adipocytokines levels, and lowered the lipid accumulation in the liver, subcutaneous adipose tissue, and epididymal visceral adipose tissue. In addition, SDC intervention increased the expression levels of IRS-2 and GLUT-2 in liver tissues and elevated GLUT-4 expression levels in skeletal muscle tissues. Notably, SDC intervention decreased the Bacteroidetes/Firmicutes ratio, increased Desulfovibrio and Lachnospiraceae genus levels, and inhibited the relative abundance of potentially pathogenic bacteria.

Conclusions

SDC intervention can improve hyperglycemia and hyperlipidemia status in diabetic mice, suggesting that this intervention might be beneficial for T2DM.