Roles of estradiol in hindbrain signal transduction activity and hindbrain AMPK regulation on hypothalamic AMPK activity and metabolic neurotransmitter mRNA and protein expression

Energy homeostasis is required for optimal body function, including successful reproduction; it is defined by sufficient availability of metabolic substrate fuel to sustain cell requirements. Energy homeostasis depends upon the interaction of several organs such as liver, muscle, white and brown adipose tissue, and brain for detecting and correcting the metabolic imbalance. The brain is highly sensitive to energy insufficiency as specialized neurons in that structure have the ability to identify cellular energy deficiency and activate mechanisms that restore energy balance. Estradiol (E) hormone regulates energy balance in female mammals via central and peripheral mechanisms which regulate food intake, metabolism, and storage. In this project, we investigated the role of E in mediating the effects of hindbrain adenosine 5'-monophosphate-activated protein kinase (AMPK) on caudal dorsal vagal complex (cDVC) neuron genomic activation and systemic glucostasis. In addition, we investigated the impact of E on hindbrain AMPK activity on the hypothalamic AMPK and metabolic neuropeptides that are expressed in the hypothalamus and regulate the energy balance such as pro-opiomelanocortin (POMC), orexigenic neuropeptide Y (NPY), Steroidogenic factor-1 neurons (SF-1), corticotropin releasing hormone (CRH), and orexin A. Additionally, we studied the cooperative between western blot analysis and Fos immunolabeling because Fos immunocytochemistry is a valuable anatomical mapping tool for distinguishing cells within complex tissues that undergo genomic activation. Therefore, western blotting was applied to hypothalamic tissue removed from histological sections of E- versus oil (O)-implanted ovariectomized (OVX) female rat brain to measure levels of metabolic transmitters associated with Fos-positive structures.;Our results showed that E exerts distinctive effects on caudal vagal complex (cDVC) in the hindbrain signal transduction pathway marker gene reactivity to activated AMPK. In addition, results showed that hypothalamic metabolic effector neurotransmitter sensitivity, that's indicated by adjustments in PVH CRH, VMH SF-1, and ARH POMC and NPY mRNA and protein expression patterns, to the hindbrain AMPK activity state. Moreover, the results supported the role of E-dependent adjustments in POMC and NPY neuropeptide profiles in response to the 4th ventricular administration of AMPK activator in the hindbrain and showed that E might control the balance of ARH-derived anabolic and catabolic metabolic signaling during energy instability, furthermore, our data indicated the role of E hormone on hypothalamic structure-specific AMPK reactivity to hindbrain AMPK manipulation (activation or inhibition), which support the role of E in the regulation of hindbrain-hypothalamic connectivity in the female rat. Additionally, data showed E may establish hypothalamic targets of hindbrain AMPK-driven norepinephrine (NE) signaling. Moreover, our results indicated the distinctive patterns of ARH, VMH, and LHA Fos labeling in OVX+E and OVX+O female rats treated by fourth ventricular AMPK activator administration match with modifications in hypothalamic tissue levels of neuropeptides synthesized in those sites (e.g. POMC and NPY, SF-1, and ORX-A, respectively) at one or both drug dosages which emphasizes advantages of multi-purpose utilization of histological tissue sections for complimentary neuroanatomical and molecular analyses.;Collectively, correlative outcomes of this research support the role of E in energy balance through mediating the hindbrain-hypothalamic AMPK connectivity in the female rat, moreover, the hypothalamic metabolic neurotransmitter responses to dorsomedial hindbrain AMPK signaling may differ when E is present or absent. In addition, the E may establish hypothalamic targets of hindbrain AMPK-driven NE signaling. Furthermore, results showed the advantages of multi-purpose utilization of histological tissue sections for complimentary neuroanatomical and molecular analyzes.