Metformin inhibits mitochondrial complex I in intestinal epithelium to promote glycaemic control.
Level 5 - mechanism / opinion, no new human data
Preclinical animal model (male mice) and mechanistic metabolomic study
PubMed 42103929 · doi:10.1038/s42255-026-01530-y
What was done
Researchers investigated the mechanism of metformin's glucose-lowering effects using human metabolomic datasets combined with genetic mouse models (specifically male mice). They evaluated changes in mitochondrial complex I activity within the small intestine, tracking downstream metabolites including citrulline, lactate, lactoyl-phenylalanine, and circulating GDF15, and compared responses to phenformin and berberine.
What was found
The abstract reports no numerical values or effect sizes. Metformin was reported to inhibit mitochondrial complex I specifically within the intestinal epithelium, suppressing small-intestine citrulline synthesis, elevating GDF15, and driving intestinal glucose uptake with conversion to lactate and lactoyl-phenylalanine. Glucose lowering occurred via repeated bolus exposure rather than cumulative chronic response. Phenformin and berberine were found to share this intestine-specific complex I inhibition mechanism.
Why it matters
This study identifies the small intestine's mitochondrial complex I as a primary site mediating metformin's postprandial glucose clearance, clarifying a long-debated mechanism of action and linking it to a shared pathway used by phenformin and berberine.
Limits
The abstract does not provide quantitative data, confidence intervals, or sample sizes (n = ?). In vivo genetic experiments were conducted in male mice only, limiting direct generalizability to females and humans. Human evidence was limited to metabolomic data rather than direct clinical interventional endpoints.
Cited by
- supports Metformin impairs mitochondrial complex I.