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.

Expression of adiponectin receptors in the brain of adult zebrafish and mouse: Links with neurogenic niches and brain repair

“…We also confirmed by qPCR experiments the expression of both Adipor1 and Adipor2 genes using astrocytes (CLTT) and microglia (BV2) cell lines (data not shown). In accordance with our work, other studies have also shown Adipor1 and Adipor2 expression in astrocytes, notably in the rat olfactory bulbs and hypothalamus (Guillod‐Maximin et al, ; Miranda‐Martinez et al, ; Thundyil et al, ). Interestingly, it was also shown that Adipor1 and Adipor2 were expressed in tanycytes of the hypothalamic rat arcuate nucleus (Guillod‐Maximin et al, ).…”

“…In addition, adiponectin deficiency reduced dendritic length, spine density and branching of granule neurons of male mice, and reduced neural progenitor cell proliferation and differentiation (Zhang et al, 2016), supporting a role of adiponectin signaling in neurogenic activity. Furthermore, Adipor1 and Adipor2 expression in the other brain areas described above showed similar patterns as demonstrated in other studies and in the ISH database from the Allen Brain Atlas (Guillod-Maximin et al, 2009;Lein et al, 2007;Miranda-Martinez et al, 2017;Thundyil et al, 2012). Interestingly, both Adipor appear to be mainly expressed in neurons and almost not detected in astrocytes, as shown by ISH.…”

“…Together, these findings suggest that adiponectin plays a role beyond the metabolic sphere. In rats, Adipor1 has been reported to be mainly expressed in neurons and to a lower extent in astrocytes, while Adipor2 was shown to be strongly detected in both neurons and astrocytes, as reported in the olfactory bulbs and the hypothalamus (Guillod-Maximin et al, 2009;Miranda-Martinez, Arriaga-Avila, & Guevara-Guzman, 2017).…”

Protective effects of intracerebroventricular adiponectin against olfactory impairments in an amyloid β1–42 rat model

“…Microglial M2 activation is characterized by the secretion of anti-inflammatory cytokines and increased phagocytosis for debris removal, thus promoting reparation and neuroprotection [ 55 ]. APN inhibits the activation of the nuclear factor-κB (NF-κB) pathway and the cluster of differentiation 68 (CD68), therefore inhibiting the synthesis of IL-1β, IL-6, and TNF-α in vivo and in vitro, and preventing the cytotoxic actions of microglia [ 26 , 27 , 66 ].…”

Extrinsic neuromodulation in the rodent olfactory bulb

“…As a substrate, the voltageactivated K+ channel Kv1.3 has been identified which, when phosphorylated by insulin receptor kinase, is causing a change in MC excitability (Fadool et al 2011). Adiponectine receptors have been found in all OB cell layers, and OB adiponectine injection was found to regulate the expression of insulin receptors (Miranda-Martinez et al 2017).…”