The counterregulatory response to hypoglycemia, which restores normal blood glucose levels to ensure sufficient provision of glucose to the brain, is critical for survival. To discover underlying brain regulatory systems, we performed a genetic screen in recombinant inbred mice for quantitative trait loci (QTL) controlling glucagon secretion in response to neuroglucopenia. We identified a QTL on the distal part of chromosome 7 and combined this genetic information with transcriptomic analysis of hypothalami. This revealed Fgf15 as the strongest candidate to control the glucagon response. Fgf15 was expressed by neurons of the dorsomedial hypothalamus and the perifornical area. Intracerebroventricular injection of FGF19, the human ortholog of Fgf15, reduced activation by neuroglucopenia of dorsal vagal complex neurons, of the parasympathetic nerve, and lowered glucagon secretion. In contrast, silencing Fgf15 in the dorsomedial hypothalamus increased neuroglucopenia-induced glucagon secretion. These data identify hypothalamic Fgf15 as a regulator of glucagon secretion.

Studies on designed peptides that exhibit high tendencies for medium-induced conformational transitions have recently attracted much attention because structural changes are considered as molecular key processes in degenerative diseases. The experimental access to these events has been limited so far mainly due to the intrinsic tendency of the involved polypeptides for self-association and aggregation, e.g. amyloid ? plaque formation, thought to be at the origin of Alzheimer's disease. We have developed a new concept termed 'switch-peptides' which allows the controlled onset of polypeptide folding and misfolding in vitro and in vivo, starting from a soluble, non-toxic precursor molecule. As a major feature, the folding process is initiated by enzyme-triggered N,O-acyl migrations restoring the native peptide backbone in situ. As the folding is set off in the moment of creating the bioactive molecule ('in statu nascendi', ISN), our concept allows for the first time the investigation of the early steps of protein misfolding as relevant in degenerative diseases, opening new perspectives for the rational design of therapeutically relevant compounds.

The peptidic neurotransmitter neuropeptide Y (NPY) has received great attention because it has been implicated in the regulation of several organ systems. In particular, NPY is involved in the regulatory loops that control food intake in the hypothalamus and appears also to be important for regulating the activity of neuroendocrine axes under poor metabolic conditions. Furthermore, NPY exerts vasoconstrictive action on the vasculature and potentiates the actions of many other vasoconstrictors. In addition, it was demonstrated to have trophic properties and could therefore contribute to cardiovascular remodeling. These various effects plus a number of others make NPY an attractive target for the potential treatment of human diseases, such as obesity, metabolic disorders, hypertension and heart failure.

Leptin, a hormone secreted from the adipose tissue, is involved in the regulation of food intake and neuroendocrine function, by modulation of the expression and/or function of various neuropeptides in the hypothalamus. The long isoform (OB-Rb) is the major signaling form of the leptin receptor in the hypothalamus. We have used double-labeling immunohistochemistry to examine the extent of OB-Rb expression in neurochemically defined cell types in the ovine hypothalamus. OB-Rb-like immunoreactivity was widespread within cells localized to the periventricular, paraventricular, supraoptic, dorsomedial hypothalamic, ventromedial hypothalamic and arcuate nuclei, as well as the median eminence, perifornical, anterior hypothalamic and lateral hypothalamic areas and the zona incerta. Double-labeling showed expression of OB-Rb in 59.6±6.0% neuropeptide Y-containing cells, 60.8±4.7% galanin-containing cells, 89.8±2.65% pro-opiomelanocortin-containing cells, 73.4±3.5% tyrosine hydroxylase-containing cells and 31.8±2.8% corticotropin-releasing factor-containing cells. Interestingly 100% of melanin-concentrating hormone and orexin positive cells were also OB-Rb immunoreactive. These data provide semi-quantitative information on the extent to which various cell types express OB-Rb in the hypothalamus. Expression of OB-Rb within specific neuropeptidergic neurons provides evidence for the direct action of leptin upon the various neurochemical systems that regulate food intake, neuroendocrine and autonomic function in the brain.

In nine anaesthetized pigs we have studied the influence of intranasal or intrabronchial pretreatment with TASP‐V, a neuropeptide Y (NPY) Y2 agonist formed by the attachment of NPY 21–36 to a template‐assembled synthetic peptide (TASP), on the functional responses to subsequent intranasal or intrabronchial histamine challenge. In a parallel study, subjective and objective nasal airway resistance (NAR) increase following intranasal histamine challenge was evaluated in 11 healthy volunteers after TASP‐V or placebo pretreatment. In pigs, increase in sphenopalatine blood flow induced by histamine dihydrochloride nasal spray (0.25 mg kg−1 in 3 ml of saline) was significantly reduced by 65% (P<0.05) following intranasal pretreatment with 10 μg kg−1 of TASP‐V. Bronchoconstriction induced by histamine dihydrochloride nebulization (0.5 mg kg−1 in 3 ml of saline) was significantly attenuated by 25 and 55% following aerosolized pretreatment with TASP‐V analogue at 10 and 20 μg kg−1, respectively. In healthy volunteers, objective increase in NAR and reduction in nasal minimal cross section area (MCSA) induced by intranasal spray of histamine dihydrochloride (15 μg kg−1 in 200 μl of saline) were significantly attenuated by 50% following local pretreatment with 1.275 μg kg−1 of TASP‐V when compared with saline. It is concluded that intranasal or intrabronchial pretreatment with TASP‐V reduced nasal obstruction and bronchoconstriction evoked by histamine challenge in the pig. In healthy human volunteers, this agent attenuated NAR increase and MCSA reduction induced by intranasal application of histamine. British Journal of Pharmacology (1999) 126, 989–996; doi:10.1038/sj.bjp.0702388

Neuropeptide Y (NPY) is a key modulator of the autonomic nervous system playing pivotal roles in cardiovascular and neuronal functions. In this study, we assessed the cellular localization and gene expression of NPY in rat kidneys. We also examined the relationship between NPY gene expression and renin in two rat models of hypertension (two-kidney, one-clip renal hypertension (2K1C), and deoxycorticosterone-salt-induced hypertension (DOCA-salt)) characterized by a similar blood pressure elevation. In situ hybridization and immunohistochemistry, using anti-NPY or anti-C-flanking peptide of NPY (CPON) antibodies, showed that NPY transcript and protein were colocalized in the tubules of rat kidneys. During experimental hypertension, NPY mRNA was decreased in both kidneys of the 2K1C animals, but not in the kidney of DOCA-salt rats. In 2K1C rats, renal NPY content was also decreased. The difference in NPY gene expression between 2K1C rats (a high renin model of hypertension) and DOCA-salt rats (a low renin model of hypertension) suggests that circulating angiotensin II plays a role in local renal NPY gene expression and that the elevated blood pressure per se is not the primary factor responsible for the control of NPY gene expression in the kidney.

The present work examined the effects of the subtype 2 of angiotensin II (AT2) receptors on the pressure‐natriuresis using a new peptide agonist, and the possible involvement of cyclic guanosine 3′, 5′ monophosphate (cyclic GMP) in these effects. In adult anaesthetized rats (Inactin, 100 mg kg−1, i.p.) deprived of endogenous angiotensin II by angiotensin converting enzyme inhibition (quinapril, 10 mg kg−1, i.v.), T2‐(Ang II 4–8)2 (TA), a highly specific AT2 receptor agonist (5, 10 and 30 μg kg−1 min−1, i.v.) or its solvent was infused in four groups. Renal functions were studied at renal perfusion pressures (RPP) of 90, 110 and 130 mmHg and urinary cyclic GMP excretion when RPP was at 130 mmHg. The effects of TA (10 μg kg−1 min−1) were reassessed in animals pretreated with PD 123319 (PD, 50 μg kg−1 min−1, i.v.), an AT2 receptor antagonist and the action of the same dose of PD alone was also determined. Increases in RPP from 90 to 130 mmHg did not change renal blood flow (RBF) but induced 8 and 15 fold increases in urinary flow and sodium excretion respectively. The 5 μg kg−1 min−1 dose of TA was devoid of action. The 10 and 30 μg kg−1 min−1 doses did not alter total RBF and glomerular filtration rate, but blunted pressure‐diuresis and natriuresis relationships. These effects were abolished by PD. TA decreased urinary cyclic GMP excretion. After pretreatment with PD, this decrease was reversed to an increase which was also observed in animals receiving PD alone. In conclusion, renal AT2 receptors oppose the sodium and water excretion induced by acute increases in blood pressure and this action cannot be directly explained by changes in cyclic GMP. British Journal of Pharmacology (1999) 126, 826–832; doi:10.1038/sj.bjp.0702362

A symposium report. We report on the synthesis of TASP (template assembled synthetic proteins) mols. able to bind to neurotensin Y and angiotensin II receptors, in which a-cyclodextrin is used as template. [on SciFinder (R)]

Sympathetic nerves have long been suspected of trophic activity, but the nature of their angiogenic factor has not been determined. Neuropeptide Y (NPY), a sympathetic cotransmitter, is the most abundant peptide in the heart and the brain. It is released during nerve activation and ischemia and causes vasoconstriction and smooth muscle cell proliferation. Here we report the first evidence that NPY is angiogenic. At low physiological concentrations, in vitro, it promotes vessel sprouting and adhesion, migration, proliferation, and capillary tube formation by human endothelial cells. In vivo, in a murine angiogenic assay, NPY is angiogenic and is as potent as a basic fibroblast growth factor. The NPY action is specific and is mediated by Y1 and Y2 receptors. The expression of both receptors is upregulated during cell growth; however, Y2 appears to be the main NPY angiogenic receptor. Its upregulation parallels the NPY-induced capillary tube formation on reconstituted basement membrane (Matrigel); the Y2 agonist mimics the tube-forming activity of NPY, whereas the Y2 antagonist blocks it. Endothelium contains not only NPY receptors but also peptide itself, its mRNA, and the "NPY-converting enzyme" dipeptidyl peptidase IV (both protein and mRNA), which terminates the Y1 activity of NPY and cleaves the Tyr(1)-Pro(2) from NPY to form an angiogenic Y2 agonist, NPY3-36 Endothelium is thus not only the site of action of NPY but also the origin of the autocrine NPY system, which, together with the sympathetic nerves, may be important in angiogenesis during tissue development and repair.

Human neuropeptide Y (hNPY) potentiates the postjunctional vasoconstrictor effects of alpha(1)-adrenoceptor agonists in animals and in human hand veins in vivo. We therefore hypothesized that such an interaction might also occur in the human arterial bed. With the present single-blind cross-over study in 12 healthy volunteers, the effect of subpressor doses of hNPY on the blood pressure response to alpha(1)-adrenoceptor stimulation was evaluated. Dose-response curves were constructed to intravenously infuse phenylephrine with and without coinfusion with two different doses of hNPY (1.4 and 14.3 pmol.kg(-1). min(-1)). Blood pressure, heart rate, and forearm blood flow were recorded, and plasma hNPY was determined. During infusion of the higher hNPY dose, which increased hNPY from 24.0 +/-: 12.0 to 495.1 +/-. 12.6 pmol/l, blood pressure curves were 2.4-fold shifted toward lower phenylephrine dose rates (P < 0.001). Forearm vascular resistance showed a similar trend, whereas the counter-regulatory decrease of heart rate was similar in both groups. In contrast, the lower hNPY dose rate producing a fourfold increase in hNPY concentrations did not modify the response to phenylephrine. This in vivo study in humans demonstrates that hNPY induced potentiating effects on alpha(1)-adrenergic constriction also in the systemic arterial circulation and suggests that circulating hNPY may participate in the control of vascular tone.