Nesfatin-1, a recently discovered anorectic peptide processed from NUCB2, is expressed in the neurons in specific brain areas including the paraventricular nucleus of hypothalamus (PVN), a pivotal center of feeding regulation. The regulation of nesfatin-1 expressing neurons in the PVN has little been studied. Since starvation decreases and refeeding stimulates nesfatin-1 expression specifically in the PVN, we examined direct effects of meal-evoked metabolic factors, glucose, insulin and cholecystokinin (CCK), on PVN nesfatin-1 neurons.

We isolated single neurons from PVN and measured cytosolic calcium concentration ([Ca²⁺]_i) by ratiometric fura-2 fluorescence imaging.

Glucose (10 mM), insulin (10^-13M) and CCK (10^-13M) induced increases in [Ca²⁺]_i in 55 of 311 (16.6%), 32 of 249 (12.9%) and 8 of 39 (20.5%) PVN neurons tested, respectively. Moreover, the post [Ca²⁺]_i measurement immunocytochemistry identified 58% of glucose-responsive neurons, 63% of insulin-responsive neurons, and 50% of CCK-responsive neurons as nesfatin-1 neurons, indicating that nesfatin-1 neuron is the major target for glucose, insulin and CCK in the PVN. Intracerebroventricular injection of CCK (30 pmol) significantly increased mRNA expression of nesfatin-1 in the PVN and inhibited feeding. In addition, antiserum against nesfatin-1 blocked CCK-induced anorexia.

These results demonstrate that glucose, insulin and CCK directly interact with and increase [Ca²⁺]_i in PVN nesfatin-1 neurons, and that the nesfatin-1 neuron is the major target for all of them in the PVN. Postprandial activation of the PVN nesfatin-1 neurons could be mediated by these meal-evoked nutritional and endocrine factors, which potentially contributes to generation of satiety.