We identified a gene in the ovine hypothalamus encoding for RFamide-related peptide-3 (RFRP-3), and tested the hypothesis that this system produces a hypophysiotropic hormone that inhibits the function of pituitary gonadotropes. The RFRP-3 gene encodes for a peptide that appears identical to human RFRP-3 homolog. Using an antiserum raised against RFRP-3, cells were localized to the dorsomedial hypothalamic nucleus/paraventricular nucleus of the ovine brain and shown to project to the neurosecretory zone of the ovine median eminence, predicating a role for this peptide in the regulation of anterior pituitary gland function. Ovine RFRP-3 peptide was tested for biological activity in vitro and in vivo, and was shown to reduce LH and FSH secretion in a specific manner. RFRP-3 potently inhibited GnRH-stimulated mobilization of intracellular calcium in gonadotropes. These data indicate that RFRP-3 is a specific and potent mammalian gonadotropin-inhibiting hormone, and that it acts upon pituitary gonadotropes to reduce GnRH-stimulated gonadotropin secretion.

Background-We hypothesized that molecular imaging of endothelial cell adhesion molecule expression could noninvasively evaluate prelesion atherogenic phenotype. Methods and Results-Mice deficient for the LDL-receptor and the Apobec-1 editing peptide (DKO mice) were studied as an age-dependent model of atherosclerosis. At 10, 20, and 40 weeks of age, ultrasound molecular imaging of the proximal thoracic aorta was performed with contrast agents targeted to P-selectin and VCAM-1. Atherosclerotic lesion severity and content were assessed by ultrahigh frequency ultrasound, histology, and immunohistochemistry. In wild-type mice at all ages, there was neither aortic thickening nor targeted tracer signal enhancement. In DKO mice, lesions progressed from sparse mild intimal thickening at 10 weeks to widespread severe lesions with luminal encroachment at 40 weeks. Molecular imaging for P-selectin and VCAM-1 demonstrated selective signal enhancement (PϽ0.01 versus nontargeted agent) at all ages for DKO mice. P-selectin and VCAM-1 signal in DKO mice were greater by 3-fold at 10 weeks, 4-to 6-fold at 20 weeks, and 9-to 10-fold at 40 weeks compared to wild-type mice. En face microscopy demonstrated preferential attachment of targeted microbubbles to regions of lesion formation. Conclusions-Noninvasive

Prader-Willi syndrome (PWS) is the predominant genetic cause of obesity in humans. Recent clinical reports have suggested that micro-deletion of the Snord116 gene cluster can lead to PWS, however, the extent of the contributions of the encoded snoRNAs is unknown. Here we show that mice lacking Snord116 globally have low birth weight, increased body weight gain, energy expenditure and hyperphagia. Consistent with this, microarray analysis of hypothalamic gene expression revealed a significant alteration in feeding related pathways that was also confirmed by in situ hybridisation. Importantly, selective deletion of Snord116 only from NPY expressing neurons mimics almost exactly the global deletion phenotype including the persistent low birth weight, increased body weight gain in early adulthood, increased energy expenditure and hyperphagia. Mechanistically, the lack of Snord116 in NPY neurons leads to the upregulation of NPY mRNA consistent with the hyperphagic phenotype and suggests a critical role of Snord116 in the control of NPY neuronal functions that might be dysregulated in PWS.

ObjectivesInsulin signaling in the brain has been implicated in the control of satiety, glucose homeostasis and energy balance. However, insulin signaling is dispensable in energy homeostasis controlling AgRP or POMC neurons and it is unclear which other neurons regulate these effects. Here we describe an ancient insulin/NPY neuronal network that governs energy homeostasis across phyla.MethodsTo address the role of insulin action specifically in NPY neurons, we generated a variety of models by selectively removing insulin signaling in NPY neurons in flies and mice and testing the consequences on energy homeostasis.ResultsBy specifically targeting the insulin receptor in both fly and mouse NPY expressing neurons, we found NPY-specific insulin signaling controls food intake and energy expenditure, and lack of insulin signaling in NPY neurons leads to increased energy stores and an obese phenotype. Additionally, the lack of insulin signaling in NPY neurons leads to a dysregulation of GH/IGF-1 axis and to altered insulin sensitivity.ConclusionsTaken together, these results suggest that insulin actions in NPY neurons is critical for maintaining energy balance and an impairment of this pathway may be causally linked to the development of metabolic diseases.