Integrated gut microbiota and metabolome signatures revealed by deep metagenomic sequencing in post-stroke cognitive impairment with type 2 diabetes

After a stroke, many people develop memory and thinking problems — a condition called post-stroke cognitive impairment (PSCI). When the patient also has type 2 diabetes, these cognitive problems tend to be worse, but scientists have not fully understood why. This study looked at gut bacteria, fungi, and small molecules in stool samples from 28 diabetic PSCI patients and 29 healthy controls, using detailed DNA sequencing and chemical profiling. The researchers found that diabetic PSCI patients had fewer gut bacteria that produce butyrate — a beneficial fatty acid thought to protect the brain — and were missing certain fungal species, while some potentially harmful microbes were more abundant. They also detected drops in specific neuroprotective metabolites and changes in bile acid and lipid chemistry. Crucially, three features — a fungus called Pichia kudriavzevii and two metabolites, Nb-palmitoyltryptamine and pipecolic acid — were independently linked to scores on a standard cognitive test (MoCA). The work paints a picture of a coordinated breakdown across bacteria, fungi, and host chemistry in the gut that may contribute to worse brain outcomes after stroke in people with diabetes, and suggests that targeted probiotics or metabolite-based therapies could be worth exploring.

• Depletion of butyrate-producing bacteria (Lachnospira spp. and Butyribacter intestini) and enrichment of Butyricimonas virosa in the PSCI-DM group compared with controls, despite preserved overall alpha diversity.
• Five fungal species were significantly reduced in PSCI-DM patients, including Torulaspora globosa and Pichia kudriavzevii; fungal dysbiosis across kingdoms occurred in parallel with bacterial shifts.
• 45 differentially abundant metabolites were identified: neuroprotective compounds (9-oxononanoic acid, C16-ceramide, nootkatone) were decreased, while metformin and bile acid derivatives were increased.
• Microbial functional pathways related to energy metabolism were elevated, whereas those involved in cofactor biosynthesis and neurotransmitter precursor synthesis were reduced.
• Independent associations with MoCA cognitive scores were found only for Pichia kudriavzevii (fungal species), Nb-palmitoyltryptamine, and pipecolic acid (metabolites), highlighting a subset of features most directly tied to cognitive performance.

This was a cross-sectional, case-control study enrolling 28 patients with both type 2 diabetes and post-stroke cognitive impairment (PSCI-DM) and 29 matched non-PSCI, non-diabetic controls from a Chinese clinical cohort. Baseline fecal samples were analyzed by deep shotgun metagenomic sequencing targeting both bacterial and fungal communities, complemented by untargeted metabolomics to profile small-molecule metabolites. Cognitive performance was assessed using the Montreal Cognitive Assessment (MoCA). No longitudinal follow-up or intervention was performed; all measurements reflect a single time-point.

The cross-sectional design means causal direction cannot be established — it is unknown whether gut dysbiosis contributes to cognitive decline or results from the post-stroke and diabetic state, or both. The small sample size (n=57 total) limits statistical power and generalizability, and the single-centre Chinese cohort may not represent other ethnicities or healthcare settings. Metformin use in the PSCI-DM group confounds microbial and metabolite findings, as metformin itself is a known microbiome modifier. A longitudinal interventional study — ideally a randomized trial of butyrate-producing probiotics or targeted metabolite supplementation — would be needed to establish whether correcting these microbial signatures improves cognitive outcomes.

This study extends [§76], which examined how dietary fiber modulates carbohydrate metabolism and intestinal microbiota in type 2 diabetes patients, by revealing the specific butyrate-producer taxa and neuroprotective metabolites that are depleted when T2DM is complicated by post-stroke cognitive impairment. It parallels [§72], which used metagenomic sequencing to characterize microbiota remodeling and metabolic implications after bariatric surgery, applying a similarly deep multi-omic approach to a different metabolic-neurological comorbidity context. The bile acid metabolite changes identified here also connect to [§101], which describes how specific bile acid species and gut microbial taxa drive metabolic dysfunction, suggesting a shared bile acid–microbiota axis across metabolic disease states. More broadly, the cross-kingdom (bacterial + fungal) dysbiosis framework parallels the ecological and translational perspective articulated in [§100], which emphasizes that microbiome-disease links require both ecological and causal framing — a standard this cross-sectional study approaches but does not yet fully meet.

• The Effect of OptiFibre Dietary Fiber on Carbohydrate Metabolism and Intestinal Microbiota Metabolism in Patients With Type 2 Diabetes Mellitus
  Directly comparable T2DM patient population studied with gut microbiota and metabolomics methods; contrasting an intervention (dietary fiber) against the natural dysbiotic state seen in PSCI-DM clarifies which microbial shifts are diabetes-specific versus complication-specific.
• Microbiota remodeling after bariatric surgery: Procedure-specific dynamics and metabolic implications
  Uses the same deep metagenomic + metabolomics framework to map microbiota-metabolite remodeling in a metabolic disease context (bariatric surgery), allowing methodological comparison and highlighting how different clinical triggers produce overlapping or distinct microbial signatures.
• Letter to the Editor: Gut microbiota–bile acid crosstalk - Prevotellaceae NK3B31 and 7-ketolithocholic acid drive metabolic benefits of distal bowel resection with preservation of terminal ileum
  Focuses on the gut microbiota–bile acid crosstalk axis in metabolic dysfunction, directly relevant to the bile acid derivative changes reported in PSCI-DM patients and offering mechanistic context for interpreting those metabolomic findings.
• The human microbiome at translational crossroads: an ecological and causal perspective
  Provides an ecological and causal-inference framework for evaluating microbiome-disease associations, making it essential reading for contextualizing the limitations of this cross-sectional PSCI-DM study and what would be needed to move from correlation to causation.
• Gut microbiota-modulating interventions in paediatric type 1 diabetes: a systematic review and meta-analysis
  A systematic review of gut microbiota-modulating interventions in paediatric type 1 diabetes that offers the best available evidence on whether correcting diabetic gut dysbiosis can produce clinically meaningful outcomes — the translational question this PSCI-DM study ultimately raises.