Restraint stress affects circulating NUCB2/nesfatin-1 and phoenixin levels in male rats.

The two peptides phoenixin and nesfatin-1 are colocalized in hypothalamic nuclei involved in the mediation of food intake and behavior. Phoenixin stimulates food intake and is anxiolytic, while nesfatin-1 is an anorexigenic peptide shown to increase anxiety and anhedonia. Interestingly, central activation of both peptides can be stimulated by restraint stress giving rise to a role in the mediation of stress. Thus, the aim of the study was to test whether also peripheral circulating levels of NUCB2/nesfatin-1 and phoenixin are altered by restraint stress. Male ad libitum fed Sprague Dawley rats equipped with a chronic intravenous catheter were subjected to restraint stress and plasma levels of NUCB2/nesfatin-1, phoenixin and cortisol were measured over a period of 240 min and compared to levels of freely moving rats. Peripheral cortisol levels were significantly increased in restrained rats at 30, 60, 120 and 240 min compared to controls (p < 0.05). In contrast, restraint stress decreased plasma phoenixin levels at 15 min compared to unstressed conditions (0.8-fold, p < 0.05). Circulating NUCB2/nesfatin-1 levels were increased only at 240 min in restrained rats compared to those in unstressed controls (1.3-fold, p < 0.05). In addition, circulating NUCB2/nesfatin-1 levels correlated positively with phoenixin levels (r = 0.378, p < 0.001), while neither phoenixin nor nesfatin-1 were associated with cortisol levels (r = 0.0275, and r=-0.143, p> 0.05). These data suggest that both peptides, NUCB2/nesfatin-1 and phoenixin, are affected by restraint stress, although less pronounced than circulating cortisol.

Central blockage of nesfatin-1 has anxiolytic effects but does not prevent corticotropin-releasing factor-induced anxiety in male rats.

Nesfatin-1, a pleotropic peptide, was recently implicated in the regulation of anxiety and depression-like behavior in rats. However, the underlying mechanisms remain unclear so far. Thus, this study aimed to investigate the role of endogenous nesfatin-1 in the mediation of anxiety and depression-like behavior induced by corticotropin-releasing factor (CRF). Therefore, normal weight male intracerebroventricularly (icv) cannulated Sprague Dawley rats received two consecutive icv injections of anti-nesfatin-1 antibody or IgG control antibody followed by CRF or saline, before being exposed to a behavioral test. In the elevated zero maze test, assessing anxiety and explorative behavior, blockade of nesfatin-1 using an anti-nesfatin-1 antibody under basal conditions increased the number of entries into the open arms compared to control antibody/vehicle (1.6-fold, p < 0.05) and the time in open arms compared to the other groups (p < 0.05). Control antibody/CRF-treated animals tended to spend less time in the open arms compared to control antibody/vehicle (0.7-fold, p = 0.17), an effect not altered by the nesfatin-1 antibody (control antibody/CRF-treated animals vs. nesfatin-1 antibody/CRF group, p = 1.00). In the novelty-induced hypophagia test, assessing anhedonia as part of depression-like behavior, no significant differences were observed between the four groups for the latency to the first bout, number of bouts and the amount of palatable snack eaten (p > 0.05). In summary, CRF tended to increase anxiety and explorative behavior an effect not altered by blockade of nesfatin-1, whereas no significant effect of CRF on anhedonia was observed. Blockade of endogenous nesfatin-1 significantly decreased anxiety-like behavior giving rise to a physiological role of brain nesfatin-1 in the mediation of anxiety.

Intracerebroventricular injection of phoenixin alters feeding behavior and activates nesfatin-1 immunoreactive neurons in rats.

Phoenixin is a novel neuropeptide initially associated with reproductive functions, but subsequently also with feeding behavior. Nesfatin-1 is also involved in the regulation of food intake and has been shown to largely colocalize with phoenixin in the rat brain; however, a functional link is missing so far. The current study investigated whether phoenixin activates nesfatin-1 immunoreactive nuclei in the rat brain. Male Sprague Dawley rats chronically equipped with an intracerebroventricular cannula were injected with vehicle (5 µl ddH2O) or phoenixin (1.7 nmol in 5 µl ddH2O, n = 5-6 group). Behavior was assessed manually and c-Fos as well as nesfatin-1 immunoreactivity using immunohistochemistry. Phoenixin significantly increased feeding and drinking behavior as well as locomotor activity compared to vehicle (p < 0.01). Moreover, phoenixin injected intracerebroventricularly (icv) activated several nuclei throughout the rat brain as assessed using c-Fos; the number of c-Fos/nesfatin-1 immunoreactive neurons was increased in the lateral septal nucleus (4-fold), supraoptic nucleus (107-fold), paraventricular nucleus (6-fold) and the nucleus of the solitary tract (18-fold) compared to vehicle (p < 0.05). In summary, phoenixin activates several nesfatin-1 immunoreactive nuclei in the rat brain. This activation may play a role in the modulation of food intake.

Alteration of peptidergic gut-brain signaling under conditions of obesity.

The prevalence of obesity is rising worldwide; therefore, the World Health Organization introduced the term 'globesity'. This rise also causes an increase of associated diseases such as cardiovascular diseases, type 2 diabetes, several malignomas as well as psychiatric disorders. In order to face this medical challenge, a better understanding of the pathophysiological alterations under conditions of obesity is necessary. Hunger and satiety are largely regulated by peptidergic hormones predominantly produced in the gastrointestinal tract and signaling to the brain via the gut-brain axis. While several hormones are known to decrease food intake such as nesfatin-1, cholecystokinin (CKK), glucagon-like peptide 1 (GLP-1), pancreatic polypeptide (PP) and peptide YY (PYY), only one peripherally produced and centrally acting hormone - ghrelin - is known so far that stimulates food intake. Several alterations of the signaling of these hormones have been described in the past years e.g. an attenuated postprandial response of CCK, GLP-1 and PYY as well as a reduced postprandial suppression of ghrelin that might contribute to the development and/or maintenance of obesity and will be discussed in the present review. Lastly, gaps in knowledge will be highlighted.