Date of Graduation

2017

Document Type

Thesis

Degree Type

MS

College

School of Medicine

Department

Physiology, Pharmacology & Neuroscience

Committee Chair

I Mark Olfert

Committee Co-Chair

Randy W Bryner

Committee Member

Stan M Hileman

Abstract

Cigarette smokers weigh less than non-smokers and gain weight upon smoking cessation. Electronic cigarettes (E-cigs) have been used as a smoking cessation tool among many, however, their effects on metabolism, appetite, and energy balance are virtually unknown. This study compares the effects of chronic E-cig vapor exposure on body mass, food intake, metabolism, and body composition in mice. We hypothesized that E-cig exposure would elicit similar changes on body mass, body composition, food intake, and metabolic and appetite-regulating markers as conventional cigarettes (i.e. 3R4F reference cigarette). Female C57BL/6 mice were exposed to filtered room air (n=15), mainstream smoke from 3R4F reference cigarettes (n=15), or E-cig vapor (n=15) for a total of 8-months (4 h/d, 5d/wk). Body mass, food intake, metabolic and appetite-regulating markers, heat production, and body composition were measured. Weight gain, fat-free mass (FFM), and fat mass were significantly elevated in E-cig and control mice compared to 3R4F mice. Food consumption and heat production (kcal expended/hr) was significantly increased in E-cig mice compared to control and 3R4F mice. Appetite-regulating markers (NPY, POMC, leptin, and GLP-1) were similar between all groups. Mitochondrial uncouplers (UCP-1 and UCP-3) remained unchanged between E-cig and control groups, however, UCP-1 was significantly elevated in E-cig mice compared to 3R4F mice and UCP-3 was significantly elevated in control vs. 3R4F mice. Oxygen consumption (VO2) and carbon dioxide production (VCO2) were also significantly elevated in E-cig and 3R4F mice compared to control mice, while respiratory exchange ratios (RER) were unchanged. Unlike conventional cigarettes, we found that E-cig exposure did not elicit reductions in total body or adipose mass. This suggests the effects of E-cig may not be the same as that occurring with traditional tobacco cigarettes, or that the exposure to nicotine and/or other chemicals in the E-cig liquid elicits a different response on appetite or feeding behavior. While E-cig mice increased food intake, their basal metabolism was also elevated, suggesting energy dissipation resulting in a similar net energy balance compared to control mice. Further studies are needed to evaluate the effect that flavorings and/or the compounds produced in E-cig vapor exert on metabolism, energy balance, and the neural regulation of appetite.

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