E-cigarette aerosols as systemic metabolic disruptors: integrated mitochondrial, circadian, and neurobehavioral mechanisms

E-cigarettes are promoted as reduced-harm alternatives to combustible tobacco, yet their aerosols contain metals, aldehydes, solvents, and other bioactive chemicals capable of disrupting metabolic regulation. This review synthesizes evidence from cellular, animal, and early human studies on how e-cigarette aerosol exposure affects metabolic homeostasis across mitochondrial, redox, circadian, and neurobehavioral systems. A systems-level model is proposed in which mitochondrial dysfunction, oxidative stress, circadian misalignment, and neurobehavioral alterations form a feed-forward network that drives metabolic inflexibility. Across experimental systems, e-cigarette exposure is associated with mitochondrial impairment, oxidative stress, AMPK suppression, disrupted lipid oxidation, adipose inflammation, and reduced thermogenic capacity, changes consistent with insulin resistance. Evidence also indicates disruption of circadian clock signaling and modulation of reward and appetite circuits, further biasing energy balance. These findings support a model in which e-cigarette aerosols act as multi-system metabolic disruptors affecting both peripheral organs and central regulatory pathways. However, important uncertainties remain regarding dose-response relationships, exposure patterns, device variability, and long-term human risk. This review provides an integrated framework to clarify potential links between e-cigarette aerosol exposure and metabolic dysfunction and highlights priorities for future translational and human research.