Indiana University-Purdue University Indianapolis (IUPUI) / Many signaling pathways which are classically understood for their roles in early development are also known to be involved in tissue maintenance and adult energy homeostasis. Furthermore, dysfunction of these signaling pathways results in human diseases such as cancer. An in depth understanding of how developmentally important signaling pathways function in the adult will provide mechanistic insights into disease and potential new therapeutic targets. Here in Chapter 1, the Wnt, fibroblast growth factor (FGF), and Hedgehog (Hh) signaling pathways are discussed and examples of their relevance in development, adult homeostasis, and disease are provided. Wnt signaling provides an example of this concept as it has well described roles during both development and adult metabolism. Work included in Chapter 2, investigates the regulation of adult energy homeostasis by a member of the endocrine FGF family, FGF19. The three endocrine FGFs, FGF19 (FGF15 in mice), FGF21, and FGF23 have well described roles in the regulation of metabolic processes in adults. While FGF23 is primarily involved in the regulation of phosphate and vitamin D homeostasis, FGF19 and FGF21 have shown similar pharmacological effects on whole body metabolism. Here, the importance of adaptive thermogenesis for the pharmacological action of FGF19 is explored. Using UCP1KO animals we show that whole-body thermogenesis is dispensable for body weight loss following FGF19 treatment. Finally, the potential involvement of Hh signaling in mediating the hyperphagia driven obesity observed in certain ciliopathies is explored in Chapter 3. Emerging evidence suggests cilia play an important role in the regulation of feeding behavior. In mammals, the hedgehog pathway is dependent on the primary cilium as an organizing center and defects in hedgehog signaling share some clinical symptoms of ciliopathies. Here, we characterized the expression of core pathway components in the adult hypothalamus. We show that neurons within specific nuclei important for regulation of feeding behavior express Hh ligand and members of its signaling pathway. We also demonstrate that the Hh pathway is transcriptionally upregulated in response to an overnight fast. This work provides an important foundation for understanding the functional role of Hh signaling in regulation of energy homeostasis. In its entirety, this work highlights the emerging clinical relevance of developmentally critical pathways in diseases associated with dysfunction of adult tissue homeostasis, such as obesity.

Distribution of orexin-A-like immunoreactivity (ORX-LI) in rat brains was investigated with the use of a rabbit polyclonal antibody against the full length peptide orexin A. Virtually all the ORX-LI cell bodies were observed in the lateral hypothalamus at the level of median eminence. The large majority of ORX-LI neurons appeared spherical or fusiform, 20-30 μm in diameter and issued two to five cell processes with few secondary branchings. Numerous ORX-LI fibers were observed in subregions of the hypothalamus. ORX- LI cell processes were sparsely distributed in the cortex, hippocampus and thalamus. Many varicose ORX-LI cell processes were situated close to the 3rd and lateral ventricles, some of which appeared to be protruding into the lumen. As a corollary, orexin A may be released into the ventricles and interact with neurons in distant targets, in addition to influencing the activity of neurons with which ORX-LI axons make synaptic contacts.

Post-traumatic stress disorder (PTSD) is characterized by fear extinction deficit; chronic stress worsens this deficit. Using a Chronic Unpredictable Stress (CUS) model, we previously found that CUS increased fear extinction deficit in female mice and knockout of Ciliary Neurotrophic Factor (CNTF) attenuated it. The amygdala, specifically the medial amygdala, is strongly associated with fear conditioning and extinction. CUS increased CNTF and reduced Urocortin 3 (UCN3) in the medial amygdala, suggesting CNTF-mediated UCN3 inhibition may be involved in CUS-induced deficit of fear extinction. The medial amygdala connects to the hypothalamic paraventricular nucleus (PVN) via posterior bed nucleus of stria terminalis (pBNST) and mediates the stress response (Fig. 1). The objective of this project is to determine whether CUS affects CNTF, UCN3, and CNTF-related cytokine leukemia inhibitory factor (LIF) and interleukin-6 (IL-6) in the pBNST and hypothalamic PVN. Hippocampal CNTF expression was also examined as a brain region outside of the medial amygdala-pBNST-hypothalamic PVN circuitry. 4 groups (5 mice/group) of CNTF+/+ and CNTF-/- mice were treated with 4 weeks of CUS or control handling. At the end, fresh brain samples were collected. The hypothalamic PVN, pBNST and hippocampus were punched out from 600-700 um cryostat frozen sections. CUS was applied for 4 weeks. The control mice were handled daily for 4 weeks. RNA was extracted from tissue using QIANGEN Rneasy mini kit. BCA assay was performed to analyze protein concentration, then 10% SDS gel was used to run the protein samples. Statistical analysis included one-way ANOVA followed by Bonferroni multiple comparison or 2-tailed T test. p <0.05 was defined as significant difference. In the pBNST, CUS did not affect CNTF and UCN3 mRNA expression. However, UCN3 protein was upregulated by CUS in CNTF+/+ but not CNTF-/- mice, suggesting CNTF inhibits UCN3 expression, possibly through post-transcriptional mechanism. CUS did not alter LIF and IL-3 in the pBNST. CUS did not alter CNTF mRNA expression in the PVN and further study will measure UCN3 mRNA and protein in the PVN. Finally, there was no CUS effect on CNTF, LIF and IL-6 mRNA in the hippocampus. These results and further studies are useful in development of therapeutic medications and drug targets in the case of chronic stress.

No description available.

No description available.

The mammalian central clock, located in the suprachiasmatic nucleus (SCN) of the anterior hypothalamus, controls circadian rhythms in behaviour such as the sleep-wake cycle. It is made up of approximately 20,000 heterogeneous neurons that can be classified by their expression of neuropeptides. There are three major populations: AVP neurons (arginine vasopressin), VIP neurons (vasoactive intestinal peptide), and GRP neurons (gastrin releasing peptide). How these neuronal clusters form functional units to govern various aspects of rhythmic behavior is poorly understood. At a molecular level, biological clocks are represented by transcriptional-posttranslational feedback loops that induce circadian oscillations in the electrical activity of the SCN and hence correlate with behavioral circadian rhythms. In mammals, the sleep wake cycle can be accurately predicted by measuring electrical muscle and brain activity. To investigate the link between the electrical activity of heterogeneous neurons of the SCN and the sleep wake cycle, we optogenetically manipulated AVP neurons in vivo with SSFO (stabilized step function opsin) and simultaneously recorded an electroencephalogram (EEG) and electromyogram (EMG) in freely moving mice. SSFO-mediated stimulation of AVP positive neurons in the anterior hypothalamus increased the total amount of wakefulness during the hour of stimulation. Interestingly, this effect led to a rebound in sleep in the hour after stimulation. Markov chain sleep-stage transition analysis showed that the depolarization of AVP neurons through SSFO promotes the transition from all states to wakefulness. After the end of stimulation, a compensatory increase in transitions to NREM sleep was observed. Ex vivo, SSFO activation in AVP neurons causes depolarization and modifies the activity of AVP neurons. Therefore, the results of this thesis project suggest an essential role of AVP neurons as mediators between circadian rhythmicity and sleep-wake behaviour. / Die zentrale Uhr von Säugetieren, die sich im Nucleus suprachiasmaticus (SCN) des vorderen Hypothalamus befindet, steuert zirkadiane Verhaltensrhythmen wie den Schlaf-Wach-Rhythmus. Sie besteht aus etwa 20.000 heterogenen Neuronen, die nach ihrer Expression von Neuropeptiden klassifiziert werden können. Es gibt drei große Populationen: AVP-Neuronen, VIP-Neuronen und GRP-Neuronen. Wie diese Neuronengruppen funktionelle Einheiten bilden, um verschiedene Aspekte des rhythmischen Verhaltens zu steuern, ist nur unzureichend bekannt. Bei Säugetieren kann der Schlaf-Wach-Zyklus durch Messung der elektrischen Muskel- und Gehirnaktivität genau vorhergesagt werden. Um den Zusammenhang zwischen der elektrischen Aktivität heterogener Neuronen des SCN und dem Schlaf-Wach-Zyklus zu untersuchen, wurden AVP-Neuronen in vivo mit SSFO optogenetisch manipuliert und gleichzeitig ein Elektroenzephalogramm (EEG) und ein Elektromyogramm (EMG) bei frei beweglichen Mäusen aufgezeichnet. Die SSFO-vermittelte Stimulation von AVP-positiven Neuronen im vorderen Hypothalamus erhöhte den Gesamtanteil der Wachheit während der Stunde der Stimulation. Interessanterweise führte dieser Effekt zu einem Ansteigen des Schlafes in der Stunde nach der Stimulation. Eine Markov-Ketten-Analyse der Schlafphasenübergänge zeigte, dass die Depolarisierung der AVP-Neuronen durch SSFO den Übergang von allen Zuständen zum Wachsein fördert. Nach dem Ende der Stimulation wurde ein kompensatorischer Anstieg der Schlafphasenübergänge zum NREM-Schlaf beobachtet. Ex vivo verursachte die SSFO-Aktivierung in AVP-Neuronen eine Depolarisation und veränderte die Aktivität der AVP-Neuronen. Die Ergebnisse dieser Doktorarbeit könnten auf die Rolle der AVP-Neuronen als Vermittler zwischen zirkadianer Rhythmik und Schlaf-Wach-Verhalten hinweisen.

No description available.

No description available.

No description available.

No description available.