Salivary lipid changes in young adult tobacco smokers and e-cigarette users: a hidden risk to oral health?

STUDY DESIGN: A cross-sectional, age- and gender-matched study was conducted to investigate the effects of different forms of nicotine delivery on salivary lipid profiles among young adult novice smokers compared to non-smokers.

OBJECTIVE: To assess the effect of smoking traditional cigarettes, e-cigarettes, and heated tobacco products (HTPs) on the levels of specific sphingolipids (sphingosine, sphinganine, and sphingosine-1-phosphate), various ceramides, and lipid peroxidation products [malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE)] in both unstimulated and stimulated saliva samples collected from healthy young adults who had been smoking for 1-3 years and used only 1 of the 3 nicotine delivering methods.

METHODS: Selection criteria included healthy young adults under 30 years old, with normal BMI and typical diet composition, and with no oral inflammatory lesions, orthodontic/dental appliances, or recent intake of medications or supplements. A total of 75 smokers and 25 non-smokers were enrolled in the study. Smokers were categorized into three groups, each comprising 25 individuals: traditional cigarette smokers, e-cigarette users, and HTPs smokers. Saliva samples were collected and analyzed for sphingolipid concentrations using ultra-high-performance liquid chromatography-tandem mass spectrometry. The concentrations of MDA and 4-HNE were measured using colorimetric and ELISA assays, respectively.

RESULTS: The average smoking intensity in the traditional cigarette group was 10 cigarettes per day. Salivary sphingolipid and ceramides concentrations were significantly lower in smokers compared to non-smokers across all nicotine delivery methods (p < 0.0001). Moreover, traditional cigarette smokers exhibited higher levels of 4-HNE and MDA in both stimulated and unstimulated saliva, compared to non-smokers (p < 0.01). In stimulated saliva, both MDA and 4-HNE in e-cigarette users, and MDA in HTPs users, showed significantly lower concentrations than their comparators in traditional cigarette smokers (p < 0.01).

CONCLUSION: Different nicotine delivery methods impact salivary lipid profile during the initial period of smoking habit. Reduced sphingolipids and elevated lipid peroxidation products suggest a disturbed lipid balance in the oral cavity due to enhanced oxidative stress within the salivary glands of novice smokers.