Distribution of Adiponectin Receptors 1 and 2 in the Rat Olfactory Bulb and the Effect of Adiponectin Injection on Insulin Receptor Expression

Abstract

Background. Adiponectin (APN) is an adipocyte-derived hormone that has peripheral beneficial effects. Although its receptors AdipoR1 and AdipoR2 are expressed in the brain, their function in neurons is poorly understood. The aims of this work were to describe the distribution of APN receptors in the olfactory bulb (OB) as well as the possible effects of APN injection on the insulin receptor (InsR) content and Akt kinase. Method. We performed the double immunofluorescence technique to describe the distribution of AdipoRs and the cellular type they were expressing. mRNA transcript and protein content were assessed by RT-PCR and Western blot, respectively. APN injection was performed to analyze its possible effect on the insulin pathway. Results. We found that AdipoRs were localized in all cell layers and in both neurons and astrocytes. We observed the presence of mRNA transcripts and immunoblot analysis confirmed the protein on the intact OB; APN injection in the OB resulted in a slight decrease of the total InsR and Akt phosphorylation and a reduction of phopho-InsR content. Conclusions. These data demonstrated that AdipoRs are expressed in OB regions, and APN injection could act as an insulin pathway modulator in the OB and thus possibly contribute to olfaction physiology.