The association of gut microbiota dysbiosis with various human diseases is being substantiated with increasing evidence. Metabolites derived from both, microbiota and the human host play a central role in disease susceptibility and disease progression by extensively modulating host physiology and metabolism. Several of these metabolites have the potential to serve as diagnostic biomarkers for monitoring disease states in conjunction with intestinal microbiota dysbiosis. In this narrative review we evaluate the potential of trimethylamine-N-oxide, short-chain fatty acids, 3-indoxyl sulfate, p-cresyl sulfate, secondary bile acids, hippurate, human β-defensin-2, chromogranin A, secreted immunoglobulins and zonulin to serve as biomarkers for metabolite profiling and diagnostic suitability for dysbiosis and disease.

Background and purposeThe gut microbiome is involved in autoimmunity. Data on its composition in chronic inflammatory demyelinating polyneuropathy (CIDP), the most common chronic autoimmune disorder of peripheral nerves, are currently lacking.MethodsIn this monocentric exploratory pilot study, stool samples were prospectively collected from 16 CIDP patients (mean age 58 ± 10 years, 25% female) before and 1 week after administration of intravenous immunoglobulin (IVIg). Gut microbiota were analyzed via bacterial 16S rRNA gene sequencing and compared to 15 age‐matched healthy subjects (mean age 59 ± 15 years, 66% female).ResultsThe gut microbiota of CIDP patients showed an increased alpha‐diversity (p = 0.005) and enrichment of Firmicutes, such as Blautia (p = 0.0004), Eubacterium hallii (p = 0.0004), or Ruminococcus torques (p = 0.03), and of Actinobacteriota (p = 0.03) compared to healthy subjects. IVIg administration did not alter the gut microbiome composition in CIDP in this short‐term observation (p = 0.95).ConclusionsThe gut microbiome in IVIg‐treated CIDP shows distinct features, with increased bacterial diversity and enrichment of short‐chain fatty acid producing Firmicutes. IVIg had no short‐term impact on the gut microbiome in CIDP patients. As the main limitation of this exploratory pilot study was small cohort size, future studies also including therapy‐naïve patients are warranted to verify our findings and to explore the impact of long‐term IVIg treatment on the gut microbiome in CIDP.