Date of Graduation
School of Medicine
Physiology, Pharmacology & Neuroscience
I Mark Olfert
Randy W Bryner
Stan M Hileman
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.
Breit, Matthew J., "Effects of Chronic Electronic Vapor Exposure on Body Weight, Appetite, and Metabolism" (2017). Graduate Theses, Dissertations, and Problem Reports. 5257.