A dysregulated bile acids pool is associated with metabolic syndrome and gut microbial dysbiosis in early adolescence

OBJECTIVE

The increased prevalence of childhood metabolic syndrome (MetS) is a public health issue. It has been shown that a dysregulated bile acid (BA) profile could be involved in the development of MetS, in which the gut microbiota could have a significant role in BA levels. This study aimed to evaluate differences in serum BA levels in children with and without MetS and whether these levels were associated with gut microbial composition.

METHODS

A total of 100 children aged 10 to 12 years were enrolled in this study, 42 children with MetS (cases) and 58 control participants. Serum BAs were measured by liquid chromatography-tandem mass spectrometry and gut microbiota was determined by 16S ribosomal RNA gene sequencing.

RESULTS

Children with MetS showed higher levels of total, secondary, and 12α-hydroxylated BAs, as well as deoxycholic acid, and these were associated with dyslipidemia and insulin resistance markers. Interestingly, total BAs were negatively correlated with gut bacterial diversity (Shannon index: rho = -0.218, p = 0.035), whereas total, 12α-hydroxylated, and secondary BAs, as well as deoxycholic acid, showed negative correlations with genera known for their potential health effects, including Bifidobacterium, Akkermansia, and Faecalibacterium.

CONCLUSIONS

This study suggests that childhood MetS is associated with a dysregulated BA pool and that these alterations could influence the abundance of potentially beneficial bacteria, thus contributing to gut microbial dysbiosis.

A higher bacterial inward BCAA transport driven by Faecalibacterium prausnitzii is associated with lower serum levels of BCAA in early adolescents

Background

Elevations of circulating branched-chain amino acids (BCAA) are observed in humans with obesity and metabolic comorbidities, such as insulin resistance. Although it has been described that microbial metabolism contributes to the circulating pool of these amino acids, studies are still scarce, particularly in pediatric populations. Thus, we aimed to explore whether in early adolescents, gut microbiome was associated to circulating BCAA and in this way to insulin resistance.

Methods

Shotgun sequencing was performed in DNA from fecal samples of 23 early adolescents (10–12 years old) and amino acid targeted metabolomics analysis was performed by LC–MS/MS in serum samples. By using the HUMAnN2 algorithm we explored microbiome functional profiles to identify whether bacterial metabolism contributed to serum BCAA levels and insulin resistance markers.

Results

We identified that abundance of genes encoding bacterial BCAA inward transporters were negatively correlated with circulating BCAA and HOMA-IR (P < 0.01). Interestingly, Faecalibacterium prausnitzii contributed to approximately ~ 70% of bacterial BCAA transporters gene count. Moreover, Faecalibacterium prausnitzii abundance was also negatively correlated with circulating BCAA (P = 0.001) and with HOMA-IR (P = 0.018), after adjusting for age, sex and body adiposity. Finally, the association between Faecalibacterium genus and BCAA levels was replicated over an extended data set (N = 124).

Conclusions

We provide evidence that gut bacterial BCAA transport genes, mainly encoded by Faecalibacterium prausnitzii, are associated with lower circulating BCAA and lower insulin resistance. Based on the later, we propose that the relationship between Faecalibacterium prausnitzii and insulin resistance, could be through modulation of BCAA.

Environmental and intrinsic factors shaping gut microbiota composition and diversity and its relation to metabolic health in children and early adolescents: A population-based study

BACKGROUND

Gut microbiota, by influencing multiple metabolic processes in the host, is an important determinant of human health and disease. However, gut dysbiosis associated with metabolic complications shows inconsistent patterns. This is likely driven by factors shaping gut microbial composition that have largely been under-evaluated, at a population level, in school-age children, especially from developing countries.

RESULTS

Through characterization, by 16S sequencing, of the largest gut microbial population-based school-aged children cohort in Latin America (ORSMEC, N = 926, aged 6-12 y), we identified associations of 14 clinical and environmental covariates (P_FDR<0.1), collectively explaining 15.7% of the inter-individual gut microbial variation. Extrinsic factors such as markers of socioeconomic status showed a major influence in the most abundant taxa and in the enterotypes' distribution. Age was positively correlated with higher diversity, but only in normal-weight children (rho = 0.138, P =2 × 10^-3). In contrast, this correlation although not significant, was negative in overweight and obese children (rho = -0.125, P = 0.104 and rho = -0.058, P = 0.409, respectively). Finally, co-abundance groups (CAGs) were associated with the presence of metabolic complications.

CONCLUSIONS

Our study offers evidence that the presence of overweight and obesity could impair the microbial diversity maturation associated with age. Furthermore, it provides novel results toward a better understanding of gut microbiota in the pediatric population that will ultimately help to develop therapeutic approaches to improve metabolic status.

Gut Microbiota in Obesity and Metabolic Abnormalities: A Matter of Composition or Functionality?

The obesity pandemic and the metabolic complications derived from it represent a major public health challenge worldwide. Although obesity is a multifactorial disease, research from the past decade suggests that the gut microbiota interacts with host genetics and diet, as well as with other environmental factors, and thus contributes to the development of obesity and related complications. Despite abundant research on animal models, substantial evidence from humans has only started to accumulate over the past few years. Thus, the aim of the present review is to discuss structural and functional characteristics of the gut microbiome in human obesity, challenges associated with multi-omic technologies, and advances in identifying microbial metabolites with a direct link to obesity and metabolic complications. To date, studies suggests that obesity is related to low microbial diversity and taxon depletion sometimes resulting from an interaction with host dietary habits and genotype. These findings support the idea that the depletion or absence of certain taxa leaves an empty niche, likely leading to compromised functionality and thus promoting dysbiosis. Although the role of altered gut microbiota as cause or consequence of obesity remains controversial, research on microbial genomes and metabolites points towards an increased extraction of energy from the diet in obesity and suggests that metabolites, such as trimethylamine-N-oxide or branched-chain amino acids, participate in metabolic complications. Future research should be focused on structural and functional levels to unravel the mechanism linking gut microbiota and obesity.

An Amino Acid Signature Associated with Obesity Predicts 2-Year Risk of Hypertriglyceridemia in School-Age Children

Childhood obesity is associated with a number of metabolic abnormalities leading to increased cardiovascular risk. Metabolites can be useful as early biomarkers and new targets to promote early intervention beginning in school age. Thus, we aimed to identify metabolomic profiles associated with obesity and obesity-related metabolic traits. We used data from the Obesity Research Study for Mexican children (ORSMEC) in Mexico City and included a case control (n = 1120), cross-sectional (n = 554) and a longitudinal study (n = 301) of 6-12-year-old children. Forty-two metabolites were measured using electrospray MS/MS and multivariate regression models were used to test associations of metabolomic profiles with anthropometric, clinical and biochemical parameters. Principal component analysis showed a serum amino acid signature composed of arginine, leucine/isoleucine, phenylalanine, tyrosine, valine and proline significantly associated with obesity (OR = 1.57; 95%CI 1.45-1.69, P = 3.84 × 10-31) and serum triglycerides (TG) (β = 0.067, P = 4.5 × 10-21). These associations were validated in the cross-sectional study (P < 0.0001). In the longitudinal cohort, the amino acid signature was associated with serum TG and with the risk of hypertriglyceridemia after 2 years (OR = 1.19; 95%CI 1.03-1.39, P = 0.016). This study shows that an amino acid signature significantly associated with childhood obesity, is an independent risk factor of future hypertriglyceridemia in children.

Nopal feeding reduces adiposity, intestinal inflammation and shifts the cecal microbiota and metabolism in high-fat fed rats

Nopal is a cactus plant widely consumed in Mexico that has been used in traditional medicine to aid in the treatment of type-2 diabetes. We previously showed that chronic consumption of dehydrated nopal ameliorated hepatic steatosis in obese (fa/fa) rats; however, description of the effects on other tissues is sparse. The aim of the present study was to investigate the effects of nopal cladode consumption on intestinal physiology, microbial community structure, adipose tissue, and serum biochemistry in diet-induced obese rats. Rats were fed either a normal fat (NF) diet or a HF diet containing 4% of dietary fiber from either nopal or cellulose for 6 weeks. Consumption of nopal counteracted HF-induced adiposity and adipocyte hypertrophy, and induced profound changes in intestinal physiology. Nopal consumption reduced biomarkers of intestinal inflammation (mRNA expression of IL-6) and oxidative stress (ROS), modfied gut microbiota composition, increasing microbial diversity and cecal fermentation (SCFA), and altered the serum metabolome. Interestingly, metabolomic analysis of dehydrated nopal revealed a high choline content, which appeared to generate high levels of serum betaine, that correlated negatively with hepatic triglyceride (TAG) levels. A parallel decrease in some of the taxa associated with the production of trimethylamine, suggest an increase in choline absorption and bioavailability with transformation to betaine. The latter may partially explain the previously observed effect of nopal on the development of hepatic steatosis. In conclusion, this study provides new evidence on the effects of nopal consumption on normal and HF-diet induced changes in the intestine, the liver and systemic metabolism.

Diet: friend or foe of enteroendocrine cells--how it interacts with enteroendocrine cells

Gut hormones play a key role in the regulation of food intake, energy expenditure, glucose homeostasis, lipid metabolism, and a wide range of metabolic functions in response to food ingestion. These hormones are altered in metabolic diseases, such as obesity and type 2 diabetes, and are thus proposed to be possible targets for the prevention or treatment of these diseases. It is clear that food composition, macronutrients, and other non-nutrient components as well as the physical properties of food not only modulate the secretion of gut peptides but also modulate transcription and enteroendocrine cell differentiation, which ultimately modifies gut hormone response. The specific mechanisms or sensing machinery that respond to the different components of the diet have been studied for many years; however, over the last few years, new molecular genetic techniques have led to important advances, thereby allowing a deeper understanding of these mechanisms. This review addresses the current knowledge regarding enteroendocrine cells and how diet interacts with this machinery to stimulate and regulate the secretion of gut peptides. The potential for diet interventions as a promising strategy for modulating gut hormone responses to food ingestion and, ultimately, preventing or treating metabolic diseases is being emphasized considering that these diseases are currently a public health burden.