Metformin Blunts Exercise-Mediated Increases in Insulin Sensitivity

TUESDAY, Nov. 18, 2025 (HealthDay News) -- Metformin blunts exercise-mediated increases in vascular insulin sensitivity among adults at risk for metabolic syndrome, according to a study published online Oct. 7 in the Journal of Clinical Endocrinology & Metabolism.Steven K. Malin, Ph.D., from Rutgers University in New Brunswick, New Jersey, and colleagues conducted a double-blind trial to examine whether metformin blunts insulin sensitivity in an intensity-based manner among adults at risk for metabolic syndrome. Participants were randomly assigned to low-intensity exercise plus placebo (LoEx+PL) or metformin (2,000 mg/day; LoEx+Met) and high-intensity exercise plus placebo (HiEx+PL) or metformin (HiEx+Met) for 16 weeks (22, 21, 24, and 24 participants, respectively). Pretreatment and posttreatment, a 120-minute euglycemic-hyperinsulinemic clamp was conducted to assess macrovascular insulin sensitivity via brachial artery flow-mediated dilation (percentFMD, conduit artery) and microvascular insulin sensitivity via contrast-enhanced ultrasound (microvascular blood volume and microvascular blood flow [MBF]).The researchers found that both LoEx+PL and HiEx+PL increased maximal oxygen consumption while no change was seen with LoEx+Met or HiEx+Met. Following HiEx+PL and HiEx+Met, body fat was reduced. The increase in insulin-stimulated FMDallometric and MBF seen with LoEx+PL and HiEx+PL was blunted by metformin. In addition, the reductions in fasting glucose, endothelin-1, and tumor necrosis factor-α were attenuated by metformin compared with LoEx+PL and HiEx+PL."Blood vessel function improved with exercise training, regardless of intensity," Malin said in a statement. "Metformin blunted that observation, suggesting one type of exercise intensity is not better either with the drug for blood vessel health."Abstract/Full Text (subscription or payment may be required).Sign up for our weekly HealthDay newsletter

Metformin Blunts Exercise-Mediated Increases in Insulin Sensitivity

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