Smoking induces insulin resistance--a potential link with the insulin resistance syndrome

The acute effect of smoking and snuffing on insulin sensitivity was studied in a group of healthy habitual smokers.

The euglycaemic clamp technique was combined with the subcutaneous injection of a bolus (0.1 U kg-1) of fast-acting insulin (Actrapid). Randomized subjects smoked either one cigarette per hour for 6 h, took one bag-packed snuff per hour for 6 h or refrained from nicotine for 48 h before as well as during the clamp.

Seven healthy smokers, four females and three males, of normal weight (BMI, mean +/- SEM, 21 +/- 0.7 kg m-2 with a range of 18.6-23.9), aged 31 +/- 2 years (range 24-35 years), who had consumed at least 20 cigarettes per day for at least 5 years were studied. They were recruited through an advertisement in a newspaper.

The steady-state plasma nicotine levels were similar during smoking and snuffing. The insulin and glucose levels were also similar during all three clamps. Smoking, but not snuffing, impaired insulin action (P < 0.05) mainly due to a lower peripheral glucose uptake. The mean growth hormone levels during the 6-h study were more than doubled during smoking (P < 0.01) while no significant differences were seen in the other counter-regulatory hormones.

Smoking (also in habitual smokers) acutely impairs insulin action and leads to insulin resistance. Thus, smoking can be of importance for the development of the insulin resistance syndrome associated with risk for cardiovascular disease.