Northwestern University researchers reported preclinical findings in mice suggesting metformin’s glucose-lowering effects are driven primarily by actions in gut cells rather than solely by hepatic glucose suppression. The study, published in Nature Metabolism, links metformin to inhibited mitochondrial complex I activity in intestinal epithelium. According to the work, metformin “co-opts” intestinal cells to function as a glucose sink, increasing glucose utilization and helping prevent blood glucose rises. The researchers said the same pathway appears engaged by phenformin and berberine, both described as biguanide-adjacent or mitochondria-targeting candidates in prior literature. The study’s framing centers on explaining clinical observations that have been difficult to reconcile with a liver-only mechanism, including attenuated postprandial glucose excursions and elevated intestinal glucose uptake. While the results are preclinical, the mechanistic pathway points to potential therapeutic strategies that target mitochondrial metabolism in the intestine to control glycemia.