Causal relationships between gut microbiota and IgA nephropathy: evidence from Mendelian randomization and microbiome validation
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Detection of MicroRNA Expression in the Kidneys of Immunoglobulin A Nephropathic Mice
Published on: July 8, 2020
Xin Wang1,2,3,4,5, Jiong Liu1,2,3,4,5, Wuda Huoshen6
1Renal Division, Peking University First Hospital, Beijing, China.
Background:
Emerging evidence links gut microbiota strongly with IgA Nephropathy (IgAN). However, the causal role of specific gut microbiota in IgAN remains unclear. This study used a two-sample Mendelian randomization (MR) approach, validated with 16S rRNA datasets, to identify these causal relationships.
Methods:
We performed MR analysis using genetic instruments for 412 gut microbiota taxa from genome-wide association studies (GWAS) as exposures and IgAN GWAS data as outcomes. The inverse-variance weighted method was used as the primary analysis, supplemented by MR-Egger regression, weighted median methods, and Cochran's Q test to assess pleiotropy and heterogeneity. Significant findings were validated using reverse, multivariable, and mediation MR analyses. Results were validated using genus-level 16S rRNA datasets with batch correction (ConQuR), and microbial function was inferred via PICRUSt2.
Results:
Three gut microbiota species were protective against IgAN: s_Alistipes_senegalensis (OR = 0.64, p = .002), s_Ruminococcus_bromii (OR = 0.75, p = .040), and s_Bilophila_unclassified (OR = 0.68, p = .040). Six species were associated with increased IgAN risk, including g_Barnesiella (OR = 1.32, p = .030) and s_Rothia_mucilaginosa (OR = 1.52, p = .040). After multiple-testing correction, significant associations persisted for s_Alistipes_senegalensis (p = .043), s_Bacteroides_clarus (p = .035), and s_Bilophila_unclassified (p = .002). Sensitivity analyses confirmed robust results without pleiotropy or heterogeneity. Genus-level validation confirmed consistent microbial shifts. Functional predictions showed upregulation of carbohydrate/fatty acid metabolism and downregulation of the urea cycle.
Conclusions:
This study reveals specific gut microbes and metabolic pathways potentially driving IgAN, offering novel biomarkers and therapeutic targets for microbiome-based interventions.
Insights
This study identified specific gut microbes influencing IgA Nephropathy (IgAN) risk. Certain bacteria like Alistipes senegalensis were protective, while others increased IgAN risk, suggesting potential microbiome-based treatments.
Area of Science:
- Genetics
- Microbiology
- Immunology
Background:
- Emerging research highlights a strong connection between gut microbiota and IgA Nephropathy (IgAN).
- The precise causal impact of distinct gut microbial species on IgAN pathogenesis remains largely undetermined.
- This investigation employs a robust Mendelian randomization (MR) approach to elucidate these complex relationships.
Purpose of the Study:
- To identify specific gut microbial taxa causally associated with IgA Nephropathy (IgAN).
- To explore the potential of gut microbiota as biomarkers and therapeutic targets for IgAN.
- To validate findings using complementary datasets and analytical methods.
Main Methods:
- A two-sample Mendelian randomization (MR) analysis was conducted using genome-wide association study (GWAS) data for 412 gut microbiota taxa.
- Inverse-variance weighted (IVW) method was the primary analysis, supported by MR-Egger, weighted median, and Cochran's Q tests for robustness.
- Results were validated through reverse, multivariable, and mediation MR analyses, alongside 16S rRNA gene sequencing data and PICRUSt2 for functional predictions.
Main Results:
- Three microbial species, *s_Alistipes_senegalensis*, *s_Ruminococcus_bromii*, and *s_Bilophila_unclassified*, demonstrated a protective effect against IgAN.
- Six species, including *g_Barnesiella* and *s_Rothia_mucilaginosa*, were associated with an increased risk of IgAN.
- Post-correction, significant associations were confirmed for *s_Alistipes_senegalensis*, *s_Bacteroides_clarus*, and *s_Bilophila_unclassified*, with no evidence of pleiotropy or heterogeneity.
Conclusions:
- Specific gut microbes and metabolic pathways are implicated in the development of IgAN.
- Identified microbial signatures may serve as novel biomarkers for IgAN.
- Findings support the development of microbiome-targeted interventions for IgAN management.
