In rat submitted to a 5 dayinfusion with glucose, hyperinsulinemia (1126 ± 101pmol/l vs. 215 ± 25 pmol/1 in Wistar control rats),coincided with an enhanced intraislet UCP2 geneexpression, whereas a 8h or a 2 day-infusion did notinduce significant changes in UCP2 mRNA expression.In rats made hypoinsulinemic and mildlydiabetic by the injection of a low dose of streptozotocin,and in 4-day-fasting rats (plasma insulin28 ± 5 pmol/1) UCP2 gene expression was sharplydecreased. Here, UCP2 is linked to hyperinsulinism.