Cannabinoids, both endogenous and exogenous, exert a profound impact on the hypothalamic control of biological processes such as reproduction and energy homeostasis. The overall goal of this proposal is to gain a better understanding of the cannabinoid regulation of energy homeostasis, and the cellular mechanism(s) by which they affect the excitability of anorexigenic proopiomelanocortin (POMC) neurons in the arcuate nucleus (ARC) of the hypothalamus to alter these actions. The fundamental hypothesis is that endocannabinoids modulate energy balance in a sex- and diet-dependent fashion that can be differentially influenced by gonadal steroid hormones. They do so, in large part, via retrograde inhibition of excitatory glutamatergic neurotransmission in POMC neurons in a manner that is sexually differentiated, and dependent on dietary composition and the gonadal steroid milieu. Endocannabinoid regulation of energy homeostasis and synaptic transmission onto POMC neurons will be studied using a transgenic, Nr5a1-cre animal model, in which either channelrhodpsin-2 or a modified Gq-coupled muscarinic M3 receptor is delivered via a viral vector construct into the hypothalamic ventromedial nucleus (VMN) and integrated into neurons expressing steroidogenic factor- 1 (SF-1; encoded by the Nr5a1 gene) for in vivo and in vitro optogenetic experimentation. Females are ovariectomized and males orchidectomized one week prior to experimentation, respectively, and treated with estradiol, testosterone, or their respective vehicles according to well-established protocols.
In Specific Aim 1, I will evaluate the mechanisms through which long-term exposure to a Westernized high-fat diet differentially enhances endocannabinoid sensitivity in males and females by assessing how it influences the capability of endogenous cannabinoids to retrogradely inhibit light- and chemically- evoked glutamatergic neurotransmission at VMN SF-1/ARC POMC synapses.
In Specific Aim 2, the objective is to determine whether these high-fat diet-induced alterations in endocannabinoid sensitivity effectively translate into changes in energy balance. Specifically, I will evaluate whether high-fat diet exposure differentially attenuates the capability of opto- and chemogenetically stimulated VMN SF-1 neurons to suppress energy intake and enhance energy expenditure, and whether these adaptations are due to alterations in the expression/activity of the energy-sensing signaling molecules like phosphatidylinositol-3-kinase and AMP-activated protein kinase. This proposal describes an integrated approach to study sex differences in, and gonadal steroid hormonal influences on, the cannabinoid regulation of energy balance. Further, it will elucidate the relevant cellular mechanisms and neuroanatomical substrates that differentially predispose males and females to dysregulated endocannabinoid signaling and food consumption under conditions of diet-induced obesity/insulin resistance.
When talking about sex differences in the cannabinoid regulation of energy balance, we mean that there are differences between males and females in their sensitivity to cannabinoid- induced changes in energy intake and expenditure. This project is right in line with one of the major goals of NIDA, which is to promote the conduct of research on sex/gender differences and women's health relating to drugs of abuse. The findings generated from this research will advance our understanding of exactly how cannabinoid intoxication increases appetite and alters metabolism more effectively in males than in females, and under different dietary conditions. They also will heighten our awareness that the therapeutic effectiveness of cannabinoids in treating cancer- and AIDS-related body wasting, as well as obesity and food addiction, may differ between men and women, which will necessitate the development of gender-specific strategies for improving these conditions.
Showing the most recent 10 out of 17 publications
