When metabolic disease rewrites infection biology: Long-term multiorgan consequences of Helicobacter pylori infection in diabetes

Table 3 Controversies and unanswered questions in the field of Helicobacter pylori infection and diabetes mellitus

Controversy/question	Current evidence (for)	Current evidence (against/Limitations)	Research priority
Does H. pylori cause T2DM or is the association confounded?	Meta-analyses show increased T2DM risk with H. pylori infection[11-13]; eradication improves glycemic markers in some RCTs	Confounding by socioeconomic status, diet, obesity; bidirectional causality plausible	Mendelian randomization studies with large biobanks; long-term eradication RCTs with glycemic endpoints
Is hepatic virulence factor detection artefactual?	Exosome-mediated CagA delivery demonstrated in vitro[29]; NAFLD meta-analysis supports association[36]	Tissue contamination possible; causal pathway not fully established in vivo in humans	In vivo tracing studies with fluorescently tagged OMVs; human liver biopsy studies in H. pylori-positive diabetics
Does eradication reverse microbiota disruption?	Short-term restoration of some taxa post-eradication[43,44]; SCFA producers may recover	Antibiotic-associated dysbiosis may worsen microbiota short term; long-term data lacking	Longitudinal microbiome studies pre- and post-eradication in diabetic cohorts, with and without probiotics
Is the STZ model adequate to model T2DM-H. pylori interaction?	Validated platform for metabolic complications; reproducible hyperglycemia; feasible for mechanism discovery	Models T1DM physiology; lacks insulin resistance component; different inflammatory landscape from T2DM	High-fat diet, db/db, or ob/ob mouse models of H. pylori infection are needed for T2DM-relevant data
Therapeutic time window: When is eradication most effective?	Early eradication in H. pylori-positive T2DM patients associated with improved insulin sensitivity[48,49]	No RCT defines optimal timing relative to diabetes duration or infection stage	Staged RCTs stratifying by duration of diabetes and infection at time of eradication

T2DM: Type 2 diabetes mellitus; RCT: Randomized controlled trial; OMV: Outer membrane vesicle; SCFA: Short-chain fatty acid; NAFLD: Non-alcoholic fatty liver disease; STZ: Streptozotocin; T1DM: Type 1 diabetes mellitus; H. pylori: Helicobacter pylori; CagA: Cytotoxin-associated gene A.