In recent years, vaping, or smoking electronic cigarettes (e-cigarettes), has emerged as a popular substitute for smoking tobacco-containing cigarettes. E-cigarettes produce a vapor that may contain nicotine as well as a variety of toxic substances, including some carcinogens. Findings from a new study suggest that some compounds in e-cigarettes trigger inflammation, promoting a leaky gut.

Leaky gut, otherwise known as intestinal permeability, is a condition in which gaps form between the tight junctions between the endothelial cells that line the gut. These gaps allow pathogens like bacteria or endotoxins (toxins that are released when bacteria die) to leak through the intestinal wall and pass directly into the bloodstream. Leaky gut has been linked with a number of chronic diseases, including Alzheimer’s disease and cardiovascular disease.

The authors of the study exposed mice to e-cigarette vapors for one hour per day and then they examined the animals' colons at one week and three months after the chronic exposure. Then they measured gene expression in the colons. They also built gut enteroids – three-dimensional tissue models that incorporate many of the features of human gut tissue, including an epithelial layer surrounding a functional lumen and all of the cell types normally found in the gut. They exposed the enteroids to e-cigarette vapor (with or without nicotine).

They found that exposure to e-cigarette vapor promoted leaky gut, increasing the susceptibility of the gut lining to bacterial infections, and triggering gut inflammation. Use of the two models established that the primary components in the vapor responsible for the harmful effects were propylene glycol and vegetable glycerol, compounds present in more than 99 percent of all e-cigarettes. They also found that e-cigarette vapor altered expression of genes involved in the cellular response to stress, infection, and inflammation.

These findings demonstrate that commonly used substances present in e-cigarettes promote leaky gut and drive inflammation and provide insights into the long-term health effects of e-cigarettes. They also underscore public health efforts to reduce e-cigarette use.

• Link to full study (pre-proof).