The effect of smoking on peripheral insulin sensitivity and plasma endothelin level

Objectives: The aim of the present study was to investigate the effect of smoking on peripheral insulin effectiveness. Methods: Seven healthy volunteers, nonsmokers, of mean age 39.6 +/- 7.1 years and mean BMI 22.65 +/- 11.98 kg/m(2), without family history of diabetes mellitus, with normal blood pressure participated in the study. All the parameters were studied twice - at baseline as well as after smoking (4 cigarettes per one hour). The study was performed in three days: at the first day we studied peripheral insulin effectiveness (M) in vivo by the artificial endocrine pancreas (Biostator), using the euglycaemic hyperinsulinaemic clamp technique, and insulin-receptor binding on circulating mononuclear blood cells; at the second day - the same parameters after one-hour smoking during the third hour of clamping; at the third day - plasma endothelin level, blood pressure and heart rate at baseline and after one-hour smoking. Results: There was a significant decrease in glucose utilization during the second clamp test, when the volunteers smoked during the third hour as compared to the test at baseline (p = 0.04). This was accompanied by a significant decrease in insulin receptor affinity (p = 0.04). Systolic blood pressure and heart rate increased significantly after one-hour smoking (p = 0.03 and p = 0.001, respectively). Plasma endothelin level increased significantly after smoking (fro m 0.62 +/- 0.15 pg/ml to 2.05 +/- 1.67 pg/ml, p = 0.03). Conclusion: Our results demonstrate that smoking decreases peripheral insulin sensitivity reducing insulin receptor affinity. We have confirmed that smoking increases plasma endothelin level, which pro ably by causing vasoconstriction and consequent tissue hypoxaemia could decrease peripheral glucose utilization. We consider that smoking could also have a direct effect on insulin receptor affinity, thus leading to decreased peripheral insulin effectiveness.