Does the microbiota play a role in the pathogenesis of autoimmune diseases?

The microbiota of the human metaorganism is not a mere bystander. These microbes have coevolved with us and are pivotal to normal development and homoeostasis. Dysbiosis of the GI microbiota is associated with many disease susceptibilities, including obesity, malignancy, liver disease and GI pathology such as IBD. It is clear that there is direct and indirect crosstalk between this microbial community and host immune response. However, the precise mechanism of this microbial influence in disease pathogenesis remains elusive and is now a major research focus. There is emerging literature on the role of the microbiota in the pathogenesis of autoimmune disease, with clear and increasing evidence that changes in the microbiota are associated with some of these diseases. Examples include type 1 diabetes, coeliac disease and rheumatoid arthritis, and these contribute significantly to global morbidity and mortality. Understanding the role of the microbiota in autoimmune diseases may offer novel insight into factors that initiate and drive disease progression, stratify patient risk for complications and ultimately deliver new therapeutic strategies. This review summarises the current status on the role of the microbiota in autoimmune diseases.

Being overweight or obese is associated with harboring a gut microbial community not capable of metabolizing the soy isoflavone daidzein to O-desmethylangolensin in peri- and post-menopausal women.

OBJECTIVE: Obesity can be a considerable health concern for peri- and post-menopausal women. Evidence suggests an association between the gut microbiome and obesity. The study objective was to evaluate the association between being overweight or obese and phenotypic markers of having an overall gut microbial environment not capable of metabolizing the isoflavone daidzein to equol or O-desmethylangolensin (ODMA). STUDY DESIGN: Cross-sectional study of 137 peri- and 218 post-menopausal women, aged 44-55 years, who consumed at least three servings per week of soy (source of daidzein). Equol and ODMA producers and non-producers were identified based on urinary concentrations of daidzein, equol and ODMA in a 24-h urine sample. MAIN OUTCOME MEASURES: Mean body mass index (BMI) and odds of obesity. RESULTS: Fifty-one women were ODMA non-producers and 226 were equol non-producers. The ODMA non-producer phenotype was positively associated with obesity (OR: 3.33, 95% CI: 1.53, 7.23), and mean BMI was significantly higher in non-producers (28.9kg/m2) than in producers (26.7kg/m2), after adjusting for age, ethnicity, and menopausal status. Positive associations with being obese were observed in both peri-menopausal (OR=3.92, 95% CI: 0.90, 17.0) and post-menopausal (OR=3.00, 95% CI: 1.22, 7.70) women. The equol non-producer phenotype was not associated with obesity (OR=1.13, 95% CI: 0.64, 1.98), and mean BMI was not significantly different between equol producers (27.3kg/m2) and non-producers (26.5kg/m2). CONCLUSIONS: These results suggest that the ODMA non-producer phenotype is associated with obesity in peri- and post-menopausal women. Further work is needed to confirm these observations in additional populations and to evaluate possible mechanisms.