Mendelian randomization analyses support causal relationship between gut microbiota and childhood obesity

Identification of 1,400 metabolites as mediators of obesity in 473 gut microbiota taxa: a mediation Mendelian randomization study

Obesity is a global health problem driven by genetic, endocrine, and environmental factors. Gut microbiota significantly influences obesity, yet causal relationships and underlying pathways remain elusive. The objective of the study was to investigate causal relationships between gut microbiota, metabolites, and obesity; elucidate potential pathways mediating obesity onset; identify novel genes; and explore the impact of plasma proteins on obesity risk. Bidirectional and two-sample Mendelian randomization (MR) were used to explore causal relationships. Mediation analyses identified mechanisms linking gut microbiota, metabolites, and obesity. Pathway analyses and protein-protein interaction assessed genetic and protein associations. The MR analysis results identified 11 gut microbiota species with causal associations with obesity, 69 metabolites that were significantly causally related to obesity, and seven bacteria with causal relationships, mediated by metabolites. Single nucleotide polymorphisms (SNP)-related gene set enrichment analysis revealed clustering in a concentration of genes enriched for phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB/AKT) and plasma membrane-related signaling pathways. Fms-related receptor tyrosine kinase 1 (FLT1), growth-associated protein 43 (GAP43), and SLIT and NTRK-like family member 1 (SLITRK1) plasma proteins had protective effects against obesity. This study revealed causal links between gut bacteria, metabolites, and obesity, and identified potential therapeutic targets. Findings deepen understanding of obesity's complex mechanisms and suggest novel prevention and treatment strategies, emphasizing the gut microbiota and treatment targets.

IMPORTANCE

This study pioneered the use of genetic approaches and mediator analyses to confirm the causal relationship between gut microbiota, metabolites, and obesity, and also explored how these factors work together to promote obesity through specific signaling pathways and protein interactions. This finding provides a theoretical basis and potential targets for precision medicine strategies against obesity, which is of great clinical significance. In addition, the identification of protective plasma proteins as biomarkers for obesity prevention opens up new avenues for tailoring obesity intervention strategies.

Rumen microbiome and fat deposition in sheep: insights from a bidirectional mendelian randomization study

Rumen microbiotas are known to influence the fat deposition (FD) in sheep, but controversy over causality remains unresolved. Here, we performed microbiome-wide association studies (MWAS), microbiome genome-wide association analysis (mbGWAS) and bidirectional mendelian randomization (MR) analyses on 1,150 sheep with genotype data from whole-genome resequencing, 16S rRNA sequencing and multilevel FD-traits data. We quantified the proportion of individual variation in FD-traits explained by host genetics, rumen microbiota, and their interaction effects. We identified 32 rumen microbiota biomarkers including Bifidobacterium that were associated with FD-traits (Padj <0.05). Further, utilizing five MR methods, we identified eight causal associations between marker genera and FD-traits (Padj <0.05), including Butyrivibrio, Olsenella, p-2534-18B5 gut group, Prevotellaceae UCG-003, and Pseudobutyrivibrio causing forward causal effects on FD, and changes in Flexilinea and Suttonella induced by FD. To our knowledge, this is the inaugural attempt to employ MR in sheep to investigate the causal relationships between gastrointestinal microbiota and complex phenotypes, underscoring the potential for developing interventions related to adipose deposition in sheep from the perspective of the rumen microbiome.

Research trends between childhood obesity and gut microbiota: a bibliometric analysis (2002-2023)

Background

In recent years, the prevalence of childhood obesity has escalated alarmingly, posing significant threats to the physical and mental well-being of children, with an elevated likelihood of persisting into adulthood. Notably, recent investigations have uncovered a profound association between intestinal microbiota, a crucial component of the internal milieu, and childhood obesity. Disturbances in intestinal microbiota and their by-products are now understood to be profoundly intertwined with the evolutionary pathway of childhood obesity. Bibliometric analysis offers a deep understanding of the current research landscape, so we apply it to a review of the emerging trends and patterns between childhood obesity and gut microbiota.

Materials and methods

We conducted a rigorous and extensive search of the Web of Science (WoS) Core Collection database, spanning the years from 1900 to 2023, to analyze scholarly articles pertaining to childhood obesity and gut microbiota. Utilizing VOSviewer, CiteSpace, the R package "bibliometrix," and the online bibliometric analysis platform (https://bibliometric.com/), we delved into the intricate details of research hotspots, academic collaborations, and emerging trends within this domain.

Results

The exhaustive search encompassed the globe, uncovering a cumulative total of 1,384 pertinent studies originating from 429 nations. The results were compelling, revealing a profound influence exerted by the United States and China in this specific field of research. Furthermore, it was observed that the volume of scholarly works pertaining to childhood obesity and gut microbiota is steadily growing year on year. The current hot topics in this field include "abuse," "maltreatment," "adverse childhood experiences," "students," and "food addiction".

Conclusion

This comprehensive review offers a meticulous exploration of the evolving trends and emerging research agendas pertaining to childhood obesity and gut microbiota over the past two decades. It strives to equip researchers with a thorough understanding of the key nations, institutions, journals, and potential collaborators in these specialized fields. Additionally, it sheds light on the current frontiers of research and strategic avenues for further exploration, thus serving as an invaluable resource for scholars delving deeper into the intricacies of childhood obesity and the gut microbiome.

Exploring causal effects of gut microbiota and metabolites on body fat percentage using two-sample Mendelian randomization

AIM

The relationship between the gut microbiota, metabolites and body fat percentage (BFP) remains unexplored. We systematically assessed the causal relationships between gut microbiota, metabolites and BFP using Mendelian randomization analysis.

MATERIALS AND METHODS

Single nucleotide polymorphisms associated with gut microbiota, blood metabolites and BFP were screened via a genome-wide association study enrolling individuals of European descent. Summary data from genome-wide association studies were extracted from the MiBioGen consortium and the UK Biobank. The inverse variance-weighted model was the primary method used to estimate these causal relationships. Sensitivity analyses were performed using pleiotropy, Mendelian randomization-Egger regression, heterogeneity tests and leave-one-out tests.

RESULTS

In the aspect of phyla, classes, orders, families and genera, we observed that o_Bifidobacteriales [β = -0.05; 95% confidence interval (CI): -0.07 to -0.03; false discovery rate (FDR) = 2.76 × 10-3], f_Bifidobacteriaceae (β = -0.05; 95% CI: -0.07 to -0.07; FDR = 2.76 × 10-3), p_Actinobacteria (β = -0.06; 95% CI: -0.09 to -0.03; FDR = 6.36 × 10-3), c_Actinobacteria (β = -0.05; 95% CI: -0.08 to -0.02; FDR = 1.06 × 10-2), g_Bifidobacterium (β = -0.05; 95% CI: -0.07 to -0.02; FDR = 1.85 × 10-2), g_Ruminiclostridium9 (β = -0.03; 95% CI: -0.06 to -0.01; FDR = 4.81 × 10-2) were negatively associated with BFP. G_Olsenella (β = 0.02; 95% CI: 0.01-0.03; FDR = 2.16 × 10-2) was positively associated with BFP. Among the gut microbiotas, f_Bifidobacteriales, o_Bifidobacteriales, c_Actinobacteria and p_Actinobacteria were shown to be significantly associated with BFP in the validated dataset. In the aspect of metabolites, we only observed that valine (β = 0.77; 95% CI: 0.5-1.04; FDR = 8.65 × 10-6) was associated with BFP.

CONCLUSIONS

Multiple gut microbiota and metabolites were strongly associated with an increased BFP. Further studies are required to elucidate the mechanisms underlying this putative causality. In addition, BFP, a key indicator of obesity, suggests that obesity-related interventions can be developed from gut microbiota and metabolite perspectives.

Gut microbiota-metabolite interactions meditate the effect of dietary patterns on precocious puberty

Precocious puberty, a pediatric endocrine disorder classified as central precocious puberty (CPP) or peripheral precocious puberty (PPP), is influenced by diet, gut microbiota, and metabolites, but the specific mechanisms remain unclear. Our study found that increased alpha-diversity and abundance of short-chain fatty acid-producing bacteria led to elevated levels of luteinizing hormone and follicle-stimulating hormone, contributing to precocious puberty. The integration of specific microbiota and metabolites has potential diagnostic value for precocious puberty. The Prevotella genus-controlled interaction factor, influenced by complex carbohydrate consumption, mediated a reduction in estradiol levels. Interactions between obesity-related bacteria and metabolites mediated the beneficial effect of seafood in reducing luteinizing hormone levels, reducing the risk of obesity-induced precocious puberty, and preventing progression from PPP to CPP. This study provides valuable insights into the complex interplay between diet, gut microbiota and metabolites in the onset, development and clinical classification of precocious puberty and warrants further investigation.

Unraveling the mystery: a Mendelian randomized exploration of gut microbiota and different types of obesity

Background

Numerous studies have demonstrated the influence of gut microbiota on the development of obesity. In this study, we utilized Mendelian randomization (MR) analysis to investigate the gut microbiota characteristics among different types of obese patients, aiming to elucidate the underlying mechanisms and provide novel insights for obesity treatment.

Methods

Two-sample multivariable Mendelian randomization (MR) analysis was employed to assess causal relationships between gut microbiota and various obesity subtypes. Gut microbiota data were obtained from the international consortium MiBioGen, and data on obese individuals were sourced from the Finnish National Biobank FinnGen. Eligible single-nucleotide polymorphisms (SNPs) were selected as instrumental variables. Various analytical methods, including inverse variance weighted (IVW), MR-Egger regression, weighted median, MR-RAPS, and Lasso regression, were applied. Sensitivity analyses for quality control included MR-Egger intercept tests, Cochran's Q tests, and leave-one-out analyses and others.

Results

Mendelian randomization studies revealed distinct gut microbiota profiles among European populations with different obesity subtypes. Following multivariable MR analysis, we found that Ruminococcaceae UCG010 [Odds Ratio (OR): 0.842, 95% confidence interval (CI): 0.766-0.926, Adjusted P value: 0.028] independently reduced the risk of obesity induced by excessive calorie intake, while Butyricimonas [OR: 4.252, 95% CI: 2.177-8.307, Adjusted P value: 0.002] independently increased the risk of medication-induced obesity. For localized adiposity, Pasteurellaceae [OR: 0.213, 95% CI: 0.115-0.395, Adjusted P value: <0.001] acted as a protective factor. In the case of extreme obesity with alveolar hypoventilation, lactobacillus [OR: 0.724, 95% CI: 0.609-0.860, Adjusted P value: 0.035] reduced the risk of its occurrence. Additionally, six gut microbiota may have potential roles in the onset of different types of obesity. Specifically, the Ruminococcus torques group may increase the risk of its occurrence. Desulfovibrio and Catenabacterium may serve as protective factors in the onset of Drug-induced obesity. Oxalobacteraceae, Actinomycetaceae, and Ruminiclostridium 9, on the other hand, could potentially increase the risk of Drug-induced obesity. No evidence of heterogeneity or horizontal pleiotropy among SNPs was found in the above studies (all P values for Q test and MR-Egger intercept > 0.05).

Conclusion

Gut microbiota abundance is causally related to obesity, with distinct gut microbiota profiles observed among different obesity subtypes. Four bacterial species, including Ruminococcaceae UCG010, Butyricimonas, Pasteurellaceae and lactobacillus independently influence the development of various types of obesity. Probiotic and prebiotic supplementation may represent a novel approach in future obesity management.