Nesfatin-1 Influences The Excitability Of Glucosensing Neurons In The Hypothalamic Nuclei And Inhibits The Food Intake

Nesfatin-1, derived from the precursor NEFA/nucleobindin 2 (NUCB2), was recently identified as anorexigenic signal. NUCB2 mRNA expression was detected in rat hypothalamic and brainstem nuclei implicated in the regulation of food intake, notably in the ARC, PVN, LHA and NTS. Nesfatin-1 has been shown to inhibit food intake after lateral, third, or fourth brain ventricle, cisterna magna administration, or PVN injection in ad libitum fed rats. With regards to the understanding of nesfatin-1's brain sites of action, additional microinjection studies will be necessary to define specific nuclei responsive to nesfatin-1 to get insight into the differential effects on food intake. Neural mechanisms involved in nesfatin-1's anorexigenic effect encompass the recruitment of several hypothalamic and medullary anorexigenic pathways. Glucosensing neurons located in the hypothalamus and lower brainstem are involved in glucoprivic feeding and homeostatic control of blood glucose. Feeding related peptides modulate glucose sensing neurons to control food intake. Food intake also affects the secretion of feeding related peptides.Object:To shed light on the mechanisms by which nesfatin-1 exerts its satiety-promoting actions and to investigate the influence of food intake on plasm nesfatin-1's level.Methods:in vivo extracellular recording, behavioral test and ELASA were performed in the present studies.Results:1. Nesfatin-1 injection (50 pmol) into the PVN significantly reduced cumulative food intake by 58.6%,61.4%,44.5%,41.9% and 30.4%, respectively, compared with vehicle-injected controls at the end of 1,2,3,4 and 5 h after injection into the PVN.2. Nesfatin-1 (50 pmol) significantly reduced feeding at the end of 1-5 h after injection into the LHA but of a less magnitude than that observed in the PVN. Nesfatin-1 decreased cumulative food intake by 38.9%,34.0%,22.3%,25.4% and 17.6%, respectively, compared with vehicle-injected controls at the end of 1,2,3,4 and 5h after injection into the LHA. 3. The VMN exhibited a delayed inhibitory response to 50 pmol nesfatin-1, observed at the end of 2 h postinjection. The response was markedly less than the feeding response at the end of 2 h after PVN and LHA injection.4. Nesfatin-1 (50 pmol) significantly reduced cumulative water intake at the end of 2-6 h after injection into the PVN but not in the LHA and VMN.5. Among 97 recorded neurons in PVN,64 units responded to micro-injection of glucose. 27 were GE neurons and 37 were GI neurons. The main effect was excitatory after intra-PVN administration of nesfatin-1 in GI neurons. Micro-injection of nesfatin-1 significantly increased the spontaneous firing rate of GI neurons from 20.6±4.8 Hz to 32.7±6.5 Hz (P<0.01). In 37 GI neurons,73.0% were excited,13.5% were inhibited, and 13.5% were not affected.6. Of 118 neurons in the LHA tested,28.8% were inhibited by glucose (GI neurons). Glucose decreased the firing rate from 5.3±1.0 Hz to 2.4±0.5Hz (P<0.01). Of 34 GI neurons in the LHA tested, inhibitory effects were seen in 24 of GI neurons while the 4 cells were excited in response to nesfatin-1. Micro-injection of nesfatin-1 significantly decreased the spontaneous firing rate of GI neurons from 4.8±1.5 Hz to 1.6±0.4 Hz (P<0.01).7. In VMN,35 (35/77,45.4%) were GE neurons and 6 (6/77,7.7%) were GI neurons. The main effects were excitatory after intra-VMN administration of nesfatin-1 in GE neurons (27/35,77.1%). Micro-injection of nesfatin-1 significantly increased the spontaneous firing rate of GE neurons from 3.4±0.2 to 6.7±0.4 Hz (n=27, P<0.01). Of 35 GE neurons in VMN,3 were inhibited, and 5 were not affected by nesfatin-1.8. I.c.v injection of nesfatin-1 significantly reduced cumulative food intake at the end of 2,3,5 h and decreased cumulative water intake at the end of 2,3,4,5 h in MSG-treated mice. Compared with saline-treated mice, nesfatin-1 didn't change the cumulative food and water intake in MSG-treated mice at the end of 2h after injection.9. Oral saline, glucose solution, protein powder solution and fat emulsion did not affect human plasma nesfatin-1 level. Conclusion:1. Nesfatin-1 may exert at least a part of its physiological actions on the control of food intake as a direct result of its role in controlling the excitability of glucosensing neurons in the LHA, VMN and PVN.2. Nesfatin-1 inhibits water intake in the PVN.3. ARC plays a partial role in nesfatin-1's regulation of food intake.4. Macronutrients do not influence postprandial plasma nesfatin-1 level.