Brain health is independently impaired by E-vaping and high-fat diet

The potential health effects associated with electronic-cigarette

A good old gateway theory that electronic-cigarettes (e-cigarettes) are widely recognized as safer tobacco substitutes. In actuality, demographics also show that vaping cannibalizes smoking, the best explanation of the data is the "common liability". However, the utilization of e-cigarette products remains a controversial topic at present. Currently, there has been a widespread and substantial growth in e-cigarette use worldwide owing to their endless new flavors and customizable characteristics. Furthermore, e-cigarette has grown widespread among smokers as well as non-smokers, including adolescents and young adults. And some studies have shown that e-cigarette users are at greater risk to start using combustible cigarettes while e-cigarettes use was also observed the potential benefits to people who want to quit smoking or not. Although it is true that e-cigarettes generally contain fewer toxic substances than combustible cigarettes, this does not mean that the chemical composition in e-cigarettes aerosols poses absolutely no risks. While concerns about toxic substances in e-cigarettes and their widespread use in the population are reasonable, it is also crucial to consider that e-cigarettes have been associated with the potential for promoting smoking cessation and the clinically relevant improvements in users with smoking-related pathologies. Meanwhile, there is still short of understanding of the health impacts associated with e-cigarette use. Therefore, in this review, we discussed the health impacts of e-cigarette exposure on oral, nasal, pulmonary, cardiovascular systems and brain. We aspire for this review to change people's previous perceptions of e-cigarettes and provide them with a more balanced perspective. Additionally, we suggest appropriate adjustments on regulation and policy for e-cigarette to gain greater public health benefits.

Effects of e-vapour and high-fat diet on the immunohistochemical staining of nicotinic acetylcholine receptors, apoptosis, microglia and astrocytes in the adult male mouse hippocampus

The use of e-cigarettes/e-vapour, and the consumption of a high-fat diet (HFD), are two popular lifestyle choices associated with alterations in the hippocampus. This study, using a mouse model, investigated the effects of exposure to e-vapour (± nicotine) and HFD (43% fat) consumption, on the expression of nicotinic acetylcholine receptor (nAChR) subunits α3, α4, α7 and β2, apoptosis markers caspase-3 and TUNEL, microglial marker Iba-1, and astrocyte marker GFAP, in hippocampal subregions of dentate gyrus (DG) and cornu ammonis (CA) 1-3. The major findings included: (1) HFD alone had minimal effect with no consistent pattern or interaction between the markers, (2) E-vapour (± nicotine) predominantly affected the CA2 subregion, decreasing α7 and β2 nAChR subunits and Iba-1, (3) Nicotine e-vapour increased TUNEL across all subregions, and (4) HFD, in the presence of nicotine-free e-vapour, decreased caspase-3 and increased TUNEL across all regions, and decreased Iba-1 in the CA subregions, while HFD and nicotine-containing e-vapour, subregion specifically affected the α3, α4 and α7 nAChR subunits, with a protective effect against change in GFAP in the DG and Iba-1 in the CA1 and CA3. These findings highlight that e-vapour itself alters nAChRs, particularly in the CA2 subregion, associated with a decrease in neuroinflammatory response (Iba-1) across the whole hippocampus, and the addition of nicotine increases cell apoptosis across the whole hippocampus. HFD alone was not detrimental in our model, but in the presence of nicotine-free e-vapour, it differentially affected apoptosis, while the addition of nicotine increased nAChR subunits.

Effect of E-Vaping on Kidney Health in Mice Consuming a High-Fat Diet

High-fat diet (HFD) consumption and tobacco smoking are risk factors for chronic kidney disease. E-cigarettes have gained significant popularity among younger populations worldwide, especially among overweight individuals. It is unclear whether vaping interacts with HFD consumption to impact renal health. In this study, Balb/c mice (male, 7 weeks old) were fed a pellet HFD (43% fat, 20 kJ/g) for 16 weeks when exposed to nicotine or nicotine-free e-vapour from weeks 11 to 16. While HFD alone increased collagen Ia and IV depositions, it did not cause significant oxidative stress and inflammatory responses in the kidney itself. On the other hand, e-vapour exposure alone increased oxidative stress and damaged DNA and mitochondrial oxidative phosphorylation complexes without significant impact on fibrotic markers. However, the combination of nicotine e-vapour and HFD increased inflammatory responses, oxidative stress-induced DNA injury, and pro-fibrotic markers, suggesting accelerated development of renal pathology. Nicotine-free e-vapour exposure and HFD consumption suppressed the production of mitochondrial OXPHOS complexes and extracellular matrix protein deposition, which may cause structural instability that can interrupt normal kidney function in the future. In conclusion, our study demonstrated that a HFD combined with e-cigarette vapour exposure, especially when containing nicotine, can increase susceptibility to kidney disease.

E-Cigarette Vapour Alters High-Fat Diet-Induced Systemic Inflammatory Responses but Has No Effect on High-Fat Diet-Induced Changes in Gut Microbiota

Background: The gut microbiome, which can be altered by different diets or smoking, has been implicated in the pathogenesis of lung conditions. E-cigarette vaping is now recognised to have detrimental health effects, with several of these being similar to cigarette smoking. However, whether e-cigarettes can alter high-fat diet (HFD)-induced systemic effects and gut microbiota is unknown. In this study, we investigated the effects of HFD in the absence/presence of e-cigarette exposure on systemic inflammation, lipid metabolic markers, and the gut microbiome. Methods: Mice were fed a HFD (or chow) in the absence/presence of e-vapour exposure (±nicotine) and serum inflammation, lipid levels, and microbial diversity were assessed. Results: HFD increased the circulating levels of both triglycerides and non-esterified fatty acids, which were significantly reduced by e-vapour exposure in HFD-fed mice. Serum TNF-α was increased by HFD consumption or e-vapour. HFD had a significant effect on microbial diversity, but there were no additional effects of e-vapour exposure. Conclusions: This study highlights both similarities and differences in how the body responds to e-cigarette vapours, and it is therefore likely that the long-term sequelae of e-cigarette vapour exposure/vaping might not involve the significant alteration of the gut microbiome.

Comparison of periodontal status and salivary IL-15 and -18 levels in cigarette-smokers and individuals using electronic nicotine delivery systems

BACKGROUND

It is hypothesized that periodontal status is compromised and whole salivary (WS) interleukin (IL)-15 and IL-18 levels are higher among cigarette-smokers and electronic-nicotine-delivery-systems (ENDS)-users than never-smokers. The aim of the present case-control study was to compare the periodontal status and WS IL-15 and -18 levels among cigarette-smokers, ENDS-users and controls (never-smokers).

METHODS

Participants were divided into 4 groups as follows: Group-1:Current cigarette-smokers; Group-2:ENDS-users; Group-3:Never-smokers with periodontitis; and Group-4: Never-smokers without periodontitis. Demographic data was collected and plaque index (PI), gingival index (GI), probing-depth (PD), clinical attachment-loss (AL), and marginal bone loss (MBL) were measured. Number of missing teeth were recorded and WS IL-15 and IL-18 levels were determined. Group-comparisons were done and P < 0.01 was selected as an indicator of statistical analysis.

RESULTS

Nineteen, 18, 19 and 19 individuals were enrolled in groups 1, 2, 3 and 4, respectively. Scores of PI, clinical AL, PD, and number of missing-teeth were elevated in groups 1(P < 0.001), 2 (P < 0.001) and 3 (P < 0.001) than -4. Scores of PI, clinical AL, PD, MBL and missing teeth were comparable among patients in groups 1, 2 and 3. Levels of IL-15 and IL-18 were elevated in groups 1 (P < 0.001) and 2 (P < 0.001) than groups 3 and 4. The levels of IL-15 and -18 were higher in Group-3 than in Group-4 (P < 0.001).

CONCLUSION

Clinically, cigarette-smokers and never-smokers demonstrate similar periodontal statuses; however, WS immunoinflammatory biomarkers (IL-15 and -18) are elevated in these individuals than non-smokers.

Inhaled or Ingested, Which Is Worse, E-Vaping or High-Fat Diet?

Long term e-cigarette vaping induces inflammation, which is largely nicotine independent. High-fat diet (HFD) consumption is anoter cause of systemic low-grade inflammation. The likelihood of using e-cigarettes as a weight control strategy is concomitant with the increase in obesity. In Australia, only nicotine-free e-fluid is legal for sale. Therefore, this study aimed to investigate how nicotine-free e-cigarette vapour exposure affects inflammatory responses in mice with long term HFD consumption. Mice were fed a HFD for 16 weeks, while in the last 6 weeks, half of the chow and HFD groups were exposed to nicotine-free e-vapour, while the other half to ambient air. Serum, lung, liver and epididymal fat were collected to measure inflammatory markers. While both e-vapour exposure and HFD consumption independently increased serum IFN-γ, CX3CL1, IL-10, CCL20, CCL12, and CCL5 levels, the levels of IFN-γ, CX3CL1, and IL-10 were higher in mice exposed to e-vapour than HFD. The mRNA expression pattern in the epididymal fat mirrors that in the serum, suggesting the circulating inflammatory response to e-vapour is from the fat tissue. Of the upregulated cytokines in serum, none were found to change in the lungs. The anti-inflammatory cytokine IL-10 was increased by combining e-vapour and HFD in the liver. We conclude that short-term nicotine-free e-vapour is more potent than long term HFD consumption in causing systemic inflammation. Future studies will be needed to examine the long-term health impact of nicotine-free e-cigarettes.

Menthol Flavor in E-Cigarette Vapor Modulates Social Behavior Correlated With Central and Peripheral Changes of Immunometabolic Signalings

The use of electronic cigarette (e-cigarette) has been increasing dramatically worldwide. More than 8,000 flavors of e-cigarettes are currently marketed and menthol is one of the most popular flavor additives in the electronic nicotine delivery systems (ENDS). There is a controversy over the roles of e-cigarettes in social behavior, and little is known about the potential impacts of flavorings in the ENDS. In our study, we aimed to investigate the effects of menthol flavor in ENDS on the social behavior of long-term vapor-exposed mice with a daily intake limit, and the underlying immunometabolic changes in the central and peripheral systems. We found that the addition of menthol flavor in nicotine vapor enhanced the social activity compared with the nicotine alone. The dramatically reduced activation of cellular energy measured by adenosine 5′ monophosphate-activated protein kinase (AMPK) signaling in the hippocampus were observed after the chronic exposure of menthol-flavored ENDS. Multiple sera cytokines including C5, TIMP-1, and CXCL13 were decreased accordingly as per their peripheral immunometabolic responses to menthol flavor in the nicotine vapor. The serum level of C5 was positively correlated with the alteration activity of the AMPK-ERK signaling in the hippocampus. Our current findings provide evidence for the enhancement of menthol flavor in ENDS on social functioning, which is correlated with the central and peripheral immunometabolic disruptions; this raises the vigilance of the cautious addition of various flavorings in e-cigarettes and the urgency of further investigations on the complex interplay and health effects of flavoring additives with nicotine in e-cigarettes.

Differential Effects of 'Vaping' on Lipid and Glucose Profiles and Liver Metabolic Markers in Obese Versus Non-obese Mice

Tobacco smoking increases the risk of metabolic disorders due to the combination of harmful chemicals, whereas pure nicotine can improve glucose tolerance. E-cigarette vapour contains nicotine and some of the harmful chemicals found in cigarette smoke at lower levels. To investigate how e-vapour affects metabolic profiles, male Balb/c mice were exposed to a high-fat diet (HFD, 43% fat, 20kJ/g) for 16weeks, and e-vapour in the last 6weeks. HFD alone doubled fat mass and caused dyslipidaemia and glucose intolerance. E-vapour reduced fat mass in HFD-fed mice; only nicotine-containing e-vapour improved glucose tolerance. In chow-fed mice, e-vapour increased lipid content in both blood and liver. Changes in liver metabolic markers may be adaptive responses rather than causal. Future studies can investigate how e-vapour differentially affects metabolic profiles with different diets.

Acyl Peptide Enzyme Hydrolase (APEH) activity is inhibited by lipid metabolites and peroxidation products

Acyl Peptide Enzyme Hydrolase (APEH) activity is decreased in certain diseases but the mechanism and impact behind this loss in activity is not well understood. We hypothesized that lipid metabolites and lipid peroxidation products produced in inflammatory diseases may bind to and inhibit APEH activity. In vitro studies carried out in mammalian cell lysates, as well as with purified APEH protein, support our hypothesis that cellular lipid metabolites and lipid peroxidation products significantly decrease APEH activity. Enzymatic assays and molecular docking in silico analysis suggest that larger lipid metabolites are the best APEH inhibitors. APEH activity was measured in vivo in mice exposed to chronic e-cigarette vapor, as e-cigarettes are known to increase reactive oxygen species and lipid peroxidation products. In support of our in vitro findings, APEH activity in our mouse model demonstrates decreased APEH activity in the brains of mice exposed to e-cigarette vapor. These results provide a novel mechanism by which APEH activity may be inhibited in disease states. Furthermore, APEH inhibition may contribute to disease development and progression in pathologies associated with redox imbalances and can potentially act as biomarker for oxidative stress in disease.

Nicotine-free vapor inhalation produces behavioral disruptions and anxiety-like behaviors in mice: Effects of puff duration, session length, sex, and flavor

Electronic-cigarette's (ECIGs) popularity has grown over the last decade and changed the way individuals administer nicotine. Preclinical research is imperative for understanding the addictive properties and health-risks associated with ECIG use; however, there is not a standard dosing regimen used across research laboratories. The main objective was to determine how vapor puff durations, administration session length, and flavored e-liquid alter general and mood-disorder related behaviors while providing a foundation of vapor administration parameters. Adult male and female C57BL/6 mice were exposed to several nicotine-free unflavored vapor puff durations (1, 3, 6, or 10 s) and vapor administration session lengths (10 and 30 min) then measured on the following assays: locomotor activity (LMA), tail suspension test (TST), and light-dark test. The effects of mecamylamine and the time-course of vapor-induced depression of LMA also were assessed. Additionally, mice were exposed to flavored (strawberry and adventurers tobacco blend) vapor inhalation and measured on locomotor activity, tail suspension test, and light-dark test. Following both 10 and 30 min vapor administration session, there was a puff duration-dependent decrease in distance traveled, time in center, and rearing. The vapor-induced depression of LMA was not mediated by nicotine or nicotinic acetylcholine receptor (nAChR) activation and lasted 60-90 min. The 10 s puff duration produced an anxiogenic-like effect in the light-dark test by decreasing the time spent in the light side. Vapor inhalation did not significantly alter TST behavior. No significant effects of sex or flavor were found. The anxiogenic-like effects of nicotine-free vapor inhalation are concerning as many adolescents vape nicotine-free flavored e-liquid, and there is an association between ECIGs and mood disorders. Additionally, these studies demonstrate that vapor puff duration, but not vapor administration session length, is an important variable to consider during research design as it can become a confounding variable and alter baseline behaviors.