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

Abstract

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. 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. 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. 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). 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.