Deterioration of endothelial function and carotid intima-media thickness in Tibetan male adolescents exposed to second-hand smoke

Abstract

Introduction: It has been commonly accepted that second-hand smoke (SHS) is associated with atherosclerosis and endothelial dysfunction. There is growing evidence that the changes might begin in childhood. Unfortunately, no study has focused on the early atherosclerosis of Tibetan adolescents exposed to SHS. Aims: We aimed to investigate the endothelial function and carotid atherosclerosis in healthy school-aged Tibetan male adolescents. Materials and methods: All passive smoking participants (SHS) were students were 16 years old and male, and were recruited through middle schools in Lhasa city. In total 624 subjects were accepted after excluding subjects who actively smoked. The adolescents were divided into three groups according to serum cotinine level: high cotinine group (High Group) with 205 boys, intermediate cotinine group (Intermediate Group) with 210 boys, and low cotinine group (Low Group) with 209 boys. Venous blood was sampled for the measurement of cotinine concentration, lipid profile and endothelin-1 (ET-1) quantitation. High-resolution B-mode ultrasonography was performed to evaluate carotid intimamedia thickness (cIMT) and intima smoothness. The invasive vascular endothelial function was evaluated through the measurement of flow-mediated dilation (FMD) with B-mode ultrasound and ankle-brachial index (ABI) by using a blood pressure cuff and a Doppler instrument. Results: No statistical significance was found between groups in total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglyceride, ApoA-I, systolic blood pressure, diastolic blood pressure, and heart rate (p>0.05). In the lipid profile, only apolipoprotein B (ApoB) values were different between groups: ApoB in the High Group was higher than in the Low Group (p=0.0164). Plasma ET-1 concentrations in the High Group were also much higher than in the Intermediate and Low Groups (p=0.0112, p<0.001). The cIMT and intima smoothness had deteriorated in the High Group compared with the Low Group (p<0.001 and p<0.05 respectively). FMD and ABI, which indicate vascular endothelial function, was decreased in the High Group compared with the Intermediate and Low Groups (FMD, p<0.001; ABI, p<0.001). Conclusions: SHS was associated with sub-clinical carotid atherosclerosis and endothelial dysfunction in Tibetan schoolaged male adolescents. Considering the widespread exposure to SHS and the clinical relevance of early atherosclerosis, this result is of public health importance in Tibet, where health education is not satisfactory. Data from our study emphasize the importance of endorsing smoke-free environments for adolescents.

Protecting Children From Tobacco, Nicotine, and Tobacco Smoke

“…85 Carotid intima-media thickness was greater and peak flow-mediated dilation of the brachial artery was lower in children in the highest tertile of tobacco smoke exposure. Similar results were found in a study of 16-year-old male adolescents (N = 610) in Lhasa City, Tibet, 86 and in a case-control study of healthy young adults. 87 Using pooled data from the Cardiovascular Risk in Young Finns study (Finland) and the Childhood Determinants of Adult Health study (Australia), exposure to parental smoking was assessed in 3416 children and carotid intimamedia thickness was assessed in adulthood, 21 to 28 years later.…”

Cardiovascular Consequences of Childhood Secondhand Tobacco Smoke Exposure: Prevailing Evidence, Burden, and Racial and Socioeconomic Disparities: A Scientific Statement From the American Heart Association

“…Abnormalities have been documented in low-density lipoprotein cholesterol (LDL C) as well. Yang et al, in their study of Tibetan adolescents, documented that Apolipoprotein-B values were significantly lower in SHS exposed teenagers compared with controls 73 . Furthermore, in an ex-vivo study performed in healthy non-smokers exposed to SHS for 5.5 hours, Valkonen and Kuusi noted that exposure of non-smoking subjects to SHS leads to accelerated lipid peroxidation, LDL C modification, and accumulation of LDL C in human macrophages 74 .…”

“…This effect was also observed in a Chinese population of adolescents. Yang et al studied FMD in 16 year-old Tibetan school students and documented impaired endothelial function in those exposed to SHS 73 .…”

Evaluation of the Impact of Passive Smoke on Arterial Elasticity via Echo‐Tracking Technology in a Rabbit Model

“…Epidemiologic studies have shown that smoking, either actively or passively, is associated with increased cardiovascular risk. It has been reported that passive smoking results in a 30% to 60% increase in cardiovascular events 1 and is associated with atherosclerosis and endothelial dysfunction 2 . Several cross‐sectional analyses have found that smoking adversely affects arterial structure (increased intima‐media thickness) and function (decreased elasticity and endothelial function).…”

“…It has been reported that passive smoking results in a 30% to 60% increase in cardiovascular events 1 and is associated with atherosclerosis and endothelial dysfunction. 2 Several cross-sectional analyses have found that smoking adversely affects arterial structure (increased intima-media thickness) and function (decreased elasticity and endothelial function). Moreover, we previously used a rabbit model to demonstrate that secondhand smoke reduces pulmonary artery endothelium-dependent relaxation by decreasing nitric oxide synthase activity.…”