Smoking attenuates the vasoconstrictor response to noradrenaline in type I diabetic patients and normal subjects: possible relevance to diabetic nephropathy

Increased systolic ambulatory blood pressure and microalbuminuria in treated and non‐treated hypertensive smokers

OBJECTIVE

The primary aim of the present study was to evaluate the impact of smoking status on both clinic and ambulatory blood pressure (BP) and heart rate (HR) by using 24-h ambulatory BP monitoring in treated and non-treated hypertensive smokers and non-smokers. A secondary aim was to evaluate the interrelations between BP, smoking status and microalbuminuria.

DESIGN

Five hundred and eighty treated and non-treated hypertensive smokers and non-smokers were consecutively recruited. The patients were divided into groups of non-smokers (n = 414) and smokers (n = 166). We were able to match 115 smokers with 230 non-smokers with regard to clinic BP, gender and age.

METHODS

Microalbuminuria (albumin/creatinine ratio on morning spot urine sample), sitting clinic BP (mercury sphygmomanometry) and ambulatory BP (A&D TM 2421) were measured.

RESULTS

In the matched group we found a significant difference in ambulatory systolic and diastolic daytime BP between smokers and non-smokers (146.5 +/- 15.0/90.6 +/- 9.7 mmHg vs 142.3 +/- 12.6/89.0 +/- 9.0 mmHg). The smokers had significantly higher log albumin/creatinine ratio (0.51 +/- 0.93 vs 0.19 +/- 0.87). These results were found to be valid for treated as well as untreated patients. In both the matched and unmatched groups, the smokers had significantly higher HR.

CONCLUSION

The higher daytime BP and HR as well as microalbuminuria in smokers may contribute to their increased cardiovascular risk. Furthermore, the higher ambulatory BP in smokers implicates that these patients tend to be underdiagnosed and undertreated if only clinic BP is used.

Smoking cessation does not change urinary albumin excretion in normal subjects

The aim of the study was to examine the effect of smoking cessation on urinary albumin excretion (UAE) in normal subjects. The study consisted of two parts. The first was a randomized 4-week study, in which 182 heavy smokers were asked to quit smoking immediately (n = 69, available for analysis) or to continue smoking for another 4 weeks (n = 70, available for analysis). After 4 weeks, the latter group was also asked to stop smoking. The second part was a non-randomized follow-up study comparing UAE in 33 unsuccessful and 57 successful quitters followed for 26 weeks. Measurements of UAE (ELISA) were taken from 24-h urine samples before smoking cessation, after 4 weeks, and after 26 weeks. After 4 weeks, no statistically significant change in UAE was found within each group or between quitters and smokers. The 95% confidence intervals of the change in log UAE were -7.4 to 9.9% of the initial value in the smoker group and -4.9 to 11.3% in the quitter group. In the second part of the study, after 26 weeks, a 16% increase (95% confidence interval 5.5 to 26.5%) in mean log UAE was found in the group that had stopped smoking (p < 0.003), but no statistically significant difference in UAE between continued smokers and quitters was found after adjusting for the baseline level (ANCOVA). In conclusion, smoking cessation seems to have no effect on UAE within the physiological range in normal subjects over an observation period of 4 weeks, and no sign of a decrease in UAE was seen after 26 weeks of smoking cessation.

Plasma noradrenaline and ageing: effects of smoking habits

We tested the hypothesis that long-term smoking is responsible for increased plasma noradrenaline (NA) in elderly healthy subjects. Thirty-nine subjects were studied both at rest and during exercise: 10 young non-smokers (median age 24 years, range 21-33), 10 young smokers (30.5 years, 27-36), 10 elderly non-smokers (64 years, 52-75) and nine elderly smokers (62 years, 56-68). The young and elderly subjects had smoked for an average of 15 years and 46.8 years respectively. Plasma NA was significantly elevated in elderly long-term smokers compared with elderly non-smokers, young non-smokers and young smokers in both supine and sitting positions (supine: 1.06 +/- 0.24 vs. 0.71 +/- 0.22, 0.53 +/- 0.12, and 0.70 +/- 0.29 nmol L-1 respectively; sitting: 3.01 +/- 0.83 vs. 2.07 +/- 0.77, 1.89 +/- 0.52 and 2.25 +/- 0.47 nmol L-1 respectively). Plasma adrenaline did not differ among the groups. At submaximal exercise (60 W), plasma NA was significantly elevated in the elderly smokers compared with the other groups, owing to the elevated basal values. Increments in plasma NA at 60, 100 and 140 W were correlated with the relative exertion and not influenced by smoking. Plasma NA increased more in young subjects than in the elderly during maximal work load (21.7 +/- 8.0 vs. 13.4 +/- 5.4 nmol L-1) and correlated with the peak O2 uptake. Total blood volume was not different among the four groups and correlated inversely with basal plasma NA. It is concluded that long-term smoking may contribute to increased basal plasma NA concentrations and probably also increased sympathetic nerve activity in elderly healthy subjects, whereas smoking has little if any effect on plasma NA responses induced by exercise. Interindividual variability in basal plasma NA concentrations may in part be explained by differences in blood volume.

Hemodynamic and vascular effects of active and passive smoking

Epidemiologic studies suggest that active and passive exposure to tobacco smoke is an important cause of cardiovascular morbidity and mortality. Numerous clinical studies have demonstrated that cigarette smoking causes coronary vasoconstriction, an increase in coronary vascular resistance, and a decrease in coronary blood flow, despite an increase in myocardial oxygen demand. Cigarette smoking also induces diffuse or segmental coronary artery spasm. In habitual smokers, smoking one cigarette increases heart rate, blood pressure, cardiac index, and myocardial oxygen demand and impairs cardiac performance, probably through adrenergic stimulation and catecholamine release. Several experimental studies, however, show that cigarette smoke inhalation causes pulmonary vasodilation because of inhalation of NO and CO in the vapor phase of cigarette smoke. Similar to active smoking, passive smoking has the same adverse effects on the cardiovascular system, with similar changes in hemodynamics and coronary vasomotor tone, platelet activation, impairment of endothelium-dependent vasodilation, and endothelial dysfunction. The adverse cardiovascular effects of smoking can be partially abolished by alpha- and beta-blockers or by calcium entry blockers.