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A Health Threat to Bystanders Living in the Homes of Smokers: How Smoke Toxins Deposited on Surfaces Can Cause Insulin Resistance.

ABSTRACT: Thirdhand smoke (THS) is the accumulation of secondhand smoke on environmental surfaces. THS is found on the clothing and hair of smokers as well as on surfaces in homes and cars of smokers. Exposure occurs by ingestion, inhalation and dermal absorption. Children living in homes of smokers are at highest risk because they crawl on the floor, touch parents' clothing/hair and household objects. Using mice exposed to THS under conditions that mimic exposure of humans, we show that THS increases cellular oxidative stress by increasing superoxide dismutase (SOD) activity and hydrogen peroxide (H2O2) levels while reducing the activity of antioxidant enzymes catalase and glutathione peroxidase (GPx) that break down H2O2 into H2O and O2. This results in lipid peroxidation, protein nitrosylation and DNA damage. Consequences of these cell and molecular changes are hyperglycemia and insulinemia. Indeed, we found reduced levels of insulin receptor, PI3K, AKT, all important molecules in insulin signaling and glucose uptake by cells. To determine whether these effects on THS-induced insulin resistance are due to increase in oxidative stress, we treated mice exposed to THS with the antioxidants N-acetyl cysteine (NAC) and alpha-tocopherol (alpha-toc) and showed that the oxidative stress, the molecular damage, and the insulin resistance, were significantly reversed. Conversely, feeding the mice with chow that mimics "western diet", which is known to increase oxidative stress, while exposing the mice to THS, further increased the oxidative stress and aggravated hyperglycemia and insulinemia. In conclusion, THS exposure results in insulin resistance in the form of non-obese type II diabetes (NODII) through oxidative stress. If confirmed in humans, these studies could have a major impact on how people view exposure to environmental tobacco toxins, in particular to children, elderly and workers in environments where tobacco smoke has taken place.

SUBMITTER: Adhami N

PROVIDER: S-EPMC4774920 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND:Exposure to secondhand smoke (SHS) early in life increases the risk of sudden infant death syndrome (SIDS), asthma, and respiratory illnesses. Since children's primary exposure to SHS occurs in the home, these most vulnerable members of our society are not fully protected by recent increases in the adoption of smoking bans in public spaces. Although exposure to SHS is a quickly reversible cause of excess morbidity, few low-income homes strictly enforce smoking restrictions. OBJECTIVE:This study aims to test a novel approach to motivate the adoption of home smoking restrictions and to eliminate child SHS exposure by providing parents with objective data documenting home SHS exposure and "biomarker feedback" of child ingestion of tobacco toxins, that is, objective, laboratory-based results of assays performed on child urine, documenting levels of nicotine; cotinine; and NNAL (4-[methylnitrosamino]-1-[3-pyridyl]-1-butanol), which is a metabolite of the known tobacco carcinogen NNK (4-[methylnitro-samino]-1-[3-pyridyl]-1-butanone). METHODS:From 2011 to 2013, 195 low-income, female smokers with children aged ?10 years residing in their homes were recruited into a two-arm randomized clinical trial. Participants were assigned to one of two groups: biomarker feedback (n=98) and health education (n=97). In-home assessments were administered at baseline, week 16, and week 26. Children's home SHS exposure and nicotine, cotinine, and NNAL levels from urine samples, measured through a passive nicotine dosimeter and a surface sample of residual tobacco smoke (ie, thirdhand smoke), were collected at all three time points. Primary outcome was dosimeter-verified, self-reported complete home smoking restrictions at 6 months after randomization. Secondary outcomes included parental self-report of smoking behavior change and child urine tobacco toxin (biomarker) change. RESULTS:Data collection and analyses are complete, and the results are being interpreted. CONCLUSIONS:The study protocol describes the development of a novel community-based controlled trial designed to examine the efficacy of biomarker feedback documenting home and child exposure to SHS on parental smoking behavior change. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID):RR1-10.2196/12654.

Project description:BACKGROUND:Monitoring disparities in secondhand smoke (SHS) exposure is important for tailoring smoke-free policies to the needs of different groups. We examined disparity and trends in SHS exposure among both nonsmokers and smokers at Japanese workplaces between 2002 and 2012. METHODS:A total of 32,940 employees in nationally representative, population-based, repeated cross-sectional surveys in 2002, 2007 and 2012 in Japan was analyzed. Adjusted rate ratios for workplace SHS exposure from other people ("everyday" and "everyday or sometimes") were calculated according to covariates, using log-binomial regression models with survey weights. In this survey, employees who do not smoke at workplace are defined as workplace-nonsmokers; and those smoke at workplace are used as workplace-smokers. SHS exposure for smokers does not involve their own SHS. RESULTS:While everyday SHS exposure prevalence in workplace-nonsmokers decreased markedly (33.2% to 11.4%), that in workplace-smokers decreased only slightly (63.3% to 55.6%). Workplace-smokers were significantly more likely to report everyday SHS exposure than workplace-nonsmokers, and the degree of association increased over time: compared with the nonsmokers (reference), covariates-adjusted rate ratio (95% confidence interval) for the smokers increased from 1.70 (1.62-1.77) in 2002 to 4.16 (3.79-4.56) in 2012. Similar results were observed for everyday or sometimes SHS exposure. Compared with complete workplace smoking bans, partial and no bans were consistently and significantly associated with high SHS exposure among both nonsmokers and smokers. We also observed disparities in SHS exposure by employee characteristics, such as age group and worksite scale. CONCLUSIONS:Although overall SHS exposure decreased among Japanese employees between 2002 and 2012, the SHS exposure disparity between nonsmokers and smokers widened. Because smokers reported more frequent SHS exposure than nonsmokers, subsequent mortality due to SHS exposure may be higher in smokers than in nonsmokers. This information may be useful for advocating workplace smoke-free policies.

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A Health Threat to Bystanders Living in the Homes of Smokers: How Smoke Toxins Deposited on Surfaces Can Cause Insulin Resistance.

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