Adiponectin Receptors Are Expressed in Hypothalamus and Colocalized with Proopiomelanocortin and Neuropeptide Y in Rodent Arcuate Neurons

Adiponectin is involved in the control of energy homeostasis in peripheral tissues through Adipor1 and Adipor2 receptors. An increasing amount of evidence suggests that this adipocyte-secreted hormone may also act at the hypothalamic level to control energy homeostasis. In the present study, we observed the gene and protein expressions of Adipor1 and Adipor2 in rat hypothalamus using different approaches. By immunohistochemistry, Adipor1 expression was ubiquitous in the rat brain. By contrast, Adipor2 expression was more limited to specific brain areas such as hypothalamus, cortex, and hippocampus. In arcuate and paraventricular hypothalamic nuclei, Adipor1, and Adipor2 were expressed by neurons and astrocytes. Furthermore, using transgenic green fluorescent protein mice, we showed that Adipor1 and Adipor2 were present in pro-opiomelanocortin (POMC) and neuropeptide Y (NPY) neurons in the arcuate nucleus. Finally, adiponectin treatment by intracerebroventricular injection induced AMP-activated protein kinase (AMPK) phosphorylation in the rat hypothalamus. This was confirmed by in vitro studies using hypothalamic membrane fractions. In conclusion, Adipor1 and Adipor2 are both expressed by neurons (including POMC and NPY neurons) and astrocytes in the rat hypothalamic nuclei. Adiponectin is able to increase AMPK phosphorylation in the rat hypothalamus. These data reinforced a potential role of adiponectin and its hypothalamic receptors in the control of energy homeostasis.