It is firmly established that states of energy deficiency, such as fasting, anorexia nervosa, cachexia, bulimia, lactation and exercise-induced amenorrhea, as well as states of energy overabundance, such as obesity, are both associated with disruptions in fertility. These studies focus on states of negative energy balance that are associated with a suppression of reproductive function. The identity of the specific metabolic signals or afferent neural pathways that convey information about energy balance to gonadotropin-releasing hormone (GnRH) neurons, the central hypothalamic system regulating reproduction, remains elusive. Key to elucidating this link is an understanding of the regulation of kisspeptin neurons, the primary gatekeepers in controlling GnRH neurons. Our studies use two models of negative energy balance, lactation and caloric restriction, and have shown that kisspeptin signaling is greatly suppressed during these states. A key hypothesis of this proposal is that suppression of kisspeptin signaling is the primary factor in the inhibition of GnRH during states of negative energy balance. Although it is a widely held view that hypoleptinemia is the critical factor linking energy balance and suppressed GnRH, our recent studies demonstrate that restoring leptin to normal physiological levels does not reverse the inhibition of kisspeptin r GnRH in either lactation or caloric restriction. Thus, hypoleptinemia does not appear to be the primary metabolic factor responsible for the suppression of reproductive function. The proposed studies focus on new systems for integrating metabolic signals. Our hypothesis is that brainstem systems, such as glucose sensing catecholaminergic neurons, may be the site where information about metabolic signals is relayed to hypothalamic systems regulating GnRH neurons. This proposal focuses on two hypotheses: 1) Suppression of kisspeptin signaling at the site of GnRH cell bodies and at nerve fibers and terminals are primary components in the inhibition of basal GnRH secretion during states of negative energy balance, and 2) Brainstem systems serve as a site of integration of metabolic signals and provide the afferent signals that are responsible for the suppression of kisspeptin and GnRH during negative energy balance. These studies will use transgenic and wild-type rats and mice to identify mechanisms by which a decrease in kisspeptin tone coupled with increased inhibitory input to GnRH cell bodies results in a decrease in GnRH neuronal excitability, and will explore the roles of kisspeptin and neurokinin B in regulating GnRH release from nerve terminals. Studies will also establish the functional connectivity of afferent neural input that suppresses kisspeptin neurons. We propose that once the inhibitory input to kisspeptin neurons is identified, blocking the input will not onl restore kisspeptin but also reverse the inhibition on GnRH. Elucidating the specific links between energy balance and reproductive function has been a long-term goal for the past several decades. These studies will identify new pathways that regulate kisspeptin neurons that in turn control GnRH neurons and could lead to new treatments for restoring fertility or for new contraceptive agents that inhibit fertility.

Public Health Relevance

An imbalance in energy stores is associated with an inhibition of reproductive function and disruptions in fertility. However, the specific metabolic signals and the integration sites in the brain that link energy balance and reproductive function are poorly understood. These studies will identify key mechanisms and regulatory pathways for transmitting information about energy balance to neural systems regulating reproductive function.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
5R01HD014643-30
Application #
8686008
Study Section
Integrative and Clinical Endocrinology and Reproduction Study Section (ICER)
Program Officer
Lamar, Charisee A
Project Start
1979-12-01
Project End
2016-06-30
Budget Start
2014-07-01
Budget End
2015-06-30
Support Year
30
Fiscal Year
2014
Total Cost
Indirect Cost
Name
Oregon Health and Science University
Department
Other Basic Sciences
Type
Primate Centers
DUNS #
City
Portland
State
OR
Country
United States
Zip Code
97239
True, C; Takahashi, D; Kirigiti, M et al. (2017) Arcuate nucleus neuropeptide coexpression and connections to gonadotrophin-releasing hormone neurones in the female rhesus macaque. J Neuroendocrinol 29:
Baquero, Arian F; Kirigiti, Melissa A; Baquero, Karalee C et al. (2015) Developmental changes in synaptic distribution in arcuate nucleus neurons. J Neurosci 35:8558-69
Baquero, Arian F; de Solis, Alain J; Lindsley, Sarah R et al. (2014) Developmental switch of leptin signaling in arcuate nucleus neurons. J Neurosci 34:9982-94
Verma, Saurabh; Kirigiti, Melissa A; Millar, Robert P et al. (2014) Endogenous kisspeptin tone is a critical excitatory component of spontaneous GnRH activity and the GnRH response to NPY and CART. Neuroendocrinology 99:190-203
True, Cadence; Verma, Saurabh; Grove, Kevin L et al. (2013) Cocaine- and amphetamine-regulated transcript is a potent stimulator of GnRH and kisspeptin cells and may contribute to negative energy balance-induced reproductive inhibition in females. Endocrinology 154:2821-32
Nicol, L E; Grant, W F; Grant, W R et al. (2013) Pancreatic inflammation and increased islet macrophages in insulin-resistant juvenile primates. J Endocrinol 217:207-13
Lee, Shin J; Verma, Saurabh; Simonds, Stephanie E et al. (2013) Leptin stimulates neuropeptide Y and cocaine amphetamine-regulated transcript coexpressing neuronal activity in the dorsomedial hypothalamus in diet-induced obese mice. J Neurosci 33:15306-17
Lee, Shin J; Kirigiti, Melissa; Lindsley, Sarah R et al. (2013) Efferent projections of neuropeptide Y-expressing neurons of the dorsomedial hypothalamus in chronic hyperphagic models. J Comp Neurol 521:1891-914
True, C; Kirigiti, M A; Kievit, P et al. (2011) Leptin is not the critical signal for kisspeptin or luteinising hormone restoration during exit from negative energy balance. J Neuroendocrinol 23:1099-112
Sullivan, Elinor L; Smith, M Susan; Grove, Kevin L (2011) Perinatal exposure to high-fat diet programs energy balance, metabolism and behavior in adulthood. Neuroendocrinology 93:1-8

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