Neonatal Metformin Exposure Is Associated with Altered Adult Metabolic Responses to Hyperlipidic Diet in Male Wistar Rats

Obesity is a multifactorial disorder with increasing global prevalence, highlighting the importance of identifying early-life factors that may influence long-term metabolic outcomes. While metformin is widely used to improve metabolic dysfunction in adulthood, whether neonatal exposure to this drug modifies adult responses to subsequent dietary challenges remains poorly understood. This exploratory study evaluated whether intraperitoneal metformin administration during the neonatal period alters adult metabolic responses to hyperlipidic diet (HL) exposure in Wistar rats. Following weaning and sex determination, male offspring (n = 80) were included in the study and distributed among four experimental groups, i.e., saline–normolipidic (SAL-NL), saline–high-fat (SAL-HL), metformin–normolipidic (MET-NL), and metformin–high-fat (MET-HL), with 20 animals per group. From postnatal days 1 to 12, animals received daily intraperitoneal saline or metformin (100 mg/kg/day). From days 60 to 90, animals were fed normolipidic or hyperlipidic diets. Body mass, food intake, glucose tolerance (GTT), and insulin tolerance (ITT) were assessed. Neonatal metformin exposure was associated with reduced body mass gain in MET-HL animals compared to SAL-HL, while food intake differed according to dietary condition. Metformin-treated animals also exhibited improved insulin sensitivity, reflected by higher kITT values, while no significant differences were observed in glucose tolerance. These preliminary findings suggest that neonatal metformin administration may influence adult metabolic responses to dietary challenge. Further studies are required to elucidate the mechanisms and long-term implications of this early-life intervention.