Acute leptin action on insulin blood level and liver insulin receptor in the rat.

Aim of the study was to investigate acute leptin effect on insulin blood level and liver insulin binding in the rat. The administration of leptin induced time and dose dependent decrease in the insulin level, which was statistically significant in comparison to the control animals 120 min after administration of higher dose of peptide (0.30 +/- 0.05 vs 0.14 +/- 0.01 nmol/l, respectively). Simultaneously, we have shown the attenuation of liver sensitivity to insulin 2 hours after higher leptin dose injection. This phenomenon was caused by the decrease of binding capacity of high affinity insulin receptor sites (HAIR), which was statistically significant after higher leptin dose administration at both time points (0.54 +/- 0.13 vs 0.26 +/- 0.03 and 0.71 +/- 0.12 vs 0.40 +/- 0.05 pmol/mg protein for 1 and 2 h, respectively). The present study provides evidence that leptin, in addition to its inhibitory effect on insulin secretion, acts as a modulator of insulin receptor, through the decrease of binding capacity. It seems legitimate to suggest that leptin-induced decrease of insulin receptor binding capacity may be one of several causes of insulin resistance.