Sidestream smoke inhalation decreases respiratory clearance of 99mTc-DTPA acutely

A Review of the Impact of Smoking on Inhaled Insulin: Would You Stop Smoking if Insulin Can Be Inhaled?

High prevalence of diabetes and the need for tight glycemic control have been well established. With the invention of inhaled insulin, an alternate route has been explored and shows great promise. Inhaled insulin shows a similar physiologic response to subcutaneous insulin, with a faster onset of action, making it suitable for post-prandial hyperglycemia. This comes as a great relief, especially to those who are hesitant to use multiple injections in a day. Many factors affect insulin absorption, including device, particle size, airway patency. Another essential factor is smoking, which is prevalent among people with diabetes, as is in the non-diabetic population. Smoking increases the absorption of inhaled insulin, but it is not a straight fact, since acute smoking, passive smoking, chronic smoking - all have different effects on inhaled insulin. Furthermore, inhaled insulin is also affected by lung diseases. Most studies that have been conducted have included limited populations, thus questioning their generalisability. The studies from inception till 2020 have shown increased permeability of epithelial with acute smoking, change of epithelial layer back to normal after few weeks of smoking cessation, and reverting to chronic smoker levels with just one to two days of start in smoking. Data also suggests that smoking causes a reduction in insulin sensitivity, which could compensate for its increased absorption. Nicotine causes a decrease in the absorption of subcutaneous insulin, but its effect has not been seen on inhaled insulin. More studies, including diabetic smoker patients, need to be performed to give a specific set of variables. This would also add another reason to encourage smokers to quit smoking.

Hyaluronan and layilin mediate loss of airway epithelial barrier function induced by cigarette smoke by decreasing E-cadherin

Cigarette smoke (CigS) exposure is associated with increased bronchial epithelial permeability and impaired barrier function. Primary cultures of normal human bronchial epithelial cells exposed to CigS exhibit decreased E-cadherin expression and reduced transepithelial electrical resistance. These effects were mediated by hyaluronan (HA) because inhibition of its synthesis with 4-methylumbelliferone prevented these effects, and exposure to HA fragments of <70 kDa mimicked these effects. We show that the HA receptor layilin is expressed apically in human airway epithelium and that cells infected with lentivirus expressing layilin siRNAs were protected against increased permeability triggered by both CigS and HA. We identified RhoA/Rho-associated protein kinase (ROCK) as the signaling effectors downstream layilin. We conclude that HA fragments generated by CigS bind to layilin and signal through Rho/ROCK to inhibit the E-cadherin gene and protein expression, leading to a loss of epithelial cell-cell contact. These studies suggest that HA functions as a master switch protecting or disrupting the epithelial barrier in its high versus low molecular weight form and that its depolymerization is a first and necessary step triggering the inflammatory response to CigS.

Acute passive cigarette smoke exposure and inhaled human insulin (Exubera) pharmacokinetics

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Active cigarette smoking is associated with increased permeability of the pulmonary alveolar epithelium, resulting in faster absorption of inhaled drugs such as Exubera (EXU). Absorption of EXU is increased approximately twice to four times as much in chronic smokers compared with nonsmokers. The rate of clearance of radioaerosols such as technetium-labelled diethylenetriamine penta-acetic acid is decreased in response to passive smoke exposure.

WHAT THIS STUDY ADDS

Passive smoke exposure causes a decrease in lung permeability, an effect opposite to that of active smoking. Acute passive smoke exposure results in a decrease in EXU bioavailability and does not create a risk of hypoglycaemia. These results are consistent with previous studies of radioaerosol lung clearance. AIMS Relative to nonsmokers, the bioavailability of inhaled human insulin (Exubera(R); EXU) is markedly increased in chronic smokers. The pharmacokinetics of EXU following passive cigarette smoke exposure is unknown. METHODS In an open-label, crossover study, healthy nonsmoking volunteers received two treatments in randomized sequence separated by a 2-week wash-out: (i) EXU 3 mg with no passive smoke exposure and (ii) EXU 3 mg after passive smoke exposure (atmospheric nicotine levels 75-125 mug m(-3)) for 2 h. Blood samples were obtained at prespecified times up to 6 h after EXU administration.

RESULTS

Twenty-seven subjects completed both study periods. Mean plasma insulin AUC(0-360) decreased by 17% [ratio 83%, 95% confidence interval (CI) 68.8, 99.5] and mean C(max) by 29% (ratio 71%, 95% CI 59.8, 83.1) after passive cigarette smoke exposure. The median (range) t(max) was 60 min (20-120 min) and 75 min (20-360 min) in the EXU with no exposure and EXU passive exposure groups, respectively. EXU was well tolerated.

CONCLUSIONS

Unlike active chronic smoking, acute passive cigarette smoke exposure modestly decreases EXU bioavailability and thus should not increase hypoglycaemia risk. These results are consistent with those from published literature involving technetium-labelled diethylenetriamine penta-acetic acid and suggest that passive cigarette smoke exposure causes an acute decrease in lung permeability vs. active smoking, which causes an increase in permeability.

The effect of smoking cessation and subsequent resumption on absorption of inhaled insulin

OBJECTIVE

To assess the absorption profile of inhaled insulin in healthy, actively smoking subjects at baseline, after smoking cessation, and after smoking resumption and compare it with nonsmoking subjects.

RESEARCH DESIGN AND METHODS

Insulin pharmacokinetics and glucodynamics were measured in 20 male smoking subjects (10-20 cigarettes/day) and 10 matched nonsmoking subjects after receiving inhaled insulin (1 mg) or the approximate subcutaneous insulin equivalent (3 units) in a randomized cross-over fashion. All smokers then received inhaled insulin 12 h, 3 days, and 7 days into a smoking cessation period. They then resumed smoking for 2-3 days before again receiving inhaled insulin 1 h after the last cigarette.

RESULTS

Before smoking cessation, maximum insulin concentration (Cmax) and area under the curve (AUC) for insulin concentration time (AUC-Insulin(0-360)) with inhaled insulin were higher, and time to Cmax (t(max)) shorter, in smokers than nonsmokers (Cmax 26.8 vs. 9.7 microU/ml; AUC-Insulin(0-360) 2,583 vs. 1,645 microU x ml(-1) x min(-1); t(max) 20 vs. 53 min, respectively; all P < 0.05), whereas with subcutaneous insulin, systemic exposure was unchanged (AUC-Insulin(0-360) 2,324 vs. 2,269 microU x ml(-1) x min(-1); P = NS). After smoking cessation, AUC-Insulin(0-360) decreased with inhaled insulin by up to 50% within 1 week and approached nonsmoker levels. Cmax decreased and t(max) increased relative to baseline but were still not comparable with nonsmoker values. Smoking resumption completely reversed the effect of smoking cessation. Glucodynamics corroborated the observed findings in insulin pharmacokinetics.

CONCLUSIONS

Cessation and resumption of smoking greatly altered the pharmacokinetics of inhaled insulin. As rapid changes in systemic insulin exposure increase hypoglycemia risk, inhaled insulin should not be used in people with diabetes who choose to continue smoking. This is consistent with recommendations that people with diabetes refrain from smoking altogether.

Evaluation of two 99mTc-DTPA radioaerosols with different characteristics in lung ventilation studies

Two radioaerosol preparations, TechneScan -DTPA (99mTc-DTPA, 40 mCi/3 ml; IPEN-CNEN, São Paulo, SP, Brazil) and TechneScan -DTPA/AEROSOL (99mTc-DTPA/A, 15 mCi/1.5 ml with 0.5 ml ethanol; Mallinckrodt Medical, St. Louis, MO, USA), were compared in pulmonary ventilation studies in terms of total radiocounts and clearance after inhalation. An aerosol with ethanol is supposed to better distribute the radioparticles in the lungs. Twenty normal nonsmoking volunteers (10 men and 10 women), mean age of 23.2 years (range: 20 to 35 years), were studied. Images were obtained immediately and 30, 60 and 90 min after inhalation. Total and regional counts were obtained and the clearance half-lives of both lungs were determined. There was no difference in total counts between the two types of radioaerosol at any time (mean of approximately 188,000 cpm for male and female subjects at time zero in both aerosols). The highest count was obtained in the middle region of both lungs (P<0.001) with both preparations. The clearance half-life did not differ between aerosols (mean of ~80-88 min for male and female subjects for both aerosols). Small nonsignificant regional differences were observed. No differences between genders or between right and left lung were observed. 99mTc-DTPA/A generated the highest output of radioaerosol. 99mTc-DTPA with alcohol costs approximately five times more than the aerosol without alcohol. The present results show that either kind of aerosol may be adopted routinely for use in pulmonary examinations without affecting diagnosis. We suggest that the amount of 740 mBq (20 mCi) of 99mTc-DTPA in 1.5 ml saline can be used for routine examinations resulting in reduction of costs in pulmonary ventilation studies without diagnostic impairment.

Passive smoking, as measured by hair nicotine, and severity of acute lower respiratory illnesses among children

The aim of this study was to describe the association between passive smoking and the severity of acute lower respiratory illnesses (ALRI) among 351 children aged 3–27 months admitted to hospital. A total of 297 children provided hair samples, which were analysed for hair nicotine levels as an indicator of passive smoking. A severity of illness grading system was developed by using clinical and management criteria used by the medical staff at hospital. The OR for children with more severe illness being exposed to higher nicotine levels was 1.2, 95% CI: 0.57–2.58 when using dichotomised respiratory severity levels and upper versus lower nicotine quartile levels. In an ordinal logistic regression model, the OR of more severe illness being associated with higher nicotine levels was 1.07 (95% CI: 0.92–1.25). When analysis was limited to the more severe cases, the OR of the least severe category compared to the most severe category, in relation to nicotine levels in hair, was 1.79 (95% CI: 0.5–6.30). The ordinal logistic regression of this group of severely-ill children (OR 1.1 (95% CI: 0.94–1.29) was not substantially different from the overall study subjects.

In general, children with more severe illness tended to have higher levels of nicotine in their hair, although the results were within the limit of chance. Possible explanations of our results include environmental tobacco smoke (ETS) being an initiator of ALRI rather than a risk to severity, exposure levels of ETS were too low to demonstrate an effect on severity, or the power of this study was not high enough to detect an association.

Passive smoke inhalation decreases exhaled nitric oxide in normal subjects

Environmental tobacco smoke (ETS) exposure is one of the commonest pollutants in modern society. Despite documented clinical adverse effects of ETS on the lungs, objective methods of assessing airway damage have been lacking. Exhaled nitric oxide (eNO) is a rapid, sensitive method of assessing airway inflammation, and could be useful in this regard. Active smoking decreases eNO in normal subjects and eNO levels are low in habitual smokers, but the effect of ETS exposure on eNO has not previously been examined. In a single-blinded, placebo-controlled cross-over study, we examined the effect of ETS, sham and active smoke inhalation on eNO in non-smoking normal volunteers. Subjects were exposed to smoke over a period of 1 hour in a separately ventilated chamber, and eNO was measured at baseline, 15, 30, 45 and 60 minutes. With sham inhalation (n = 15), eNO levels did not change significantly from baseline, although a small decrease occurred. ETS exposure (n = 15) resulted in a rapid fall in eNO from mean (SE) 134 (29) ppb to 102 (22) ppb, or by 23.6% (p < 0.05), and remained low for 60 minutes. With active smoking (n = 7), levels fell acutely from baseline within the same time interval (71 [16] to 49 [11] ppb, or by 30.3%), and remained low. These changes were significant compared with sham exposure for both ETS (p < 0.05) and active smoke inhalation (p <.01). This suggests that eNO can be used for the investigation of the mechanisms of cigarette-induced lung damage in the experimental setting, and may potentially be useful also for environmental assessment of ETS effects.

The miseries of passive smoking

Passive smoking is defined as an involuntary exposure to a combined but diluted cigarette sidestream smoke (SS, gas and particle phases that are evolved from the smoldering end of a cigarette while the smoker is not puffing) and the exhaled smoke from smokers. SS contains numerous cytotoxic substances such as polycyclic aromatic hydrocarbons (PAHs), aromatic amines, nitrosamines, heavy metals, poisonous gases, pesticide residues, and radioactive elements in quantities much higher than those found from the cigarette mainstream smoke (MS) which is puffed by smokers. Passive smoking is found to be the cause of death from cancers and cardiac disease. Furthermore, it damagingly involves reproductive organs, the nervous system, genetic materials, and is particularly hazardous to mother and child during pregnancy and to those with a history of asthma, chronic infections, induced or earned immune deficiency, or predisposed susceptibility.