INCREASED DEPENDENCE ON BLOOD-GLUCOSE IN SMOKERS DURING REST AND SUSTAINED EXERCISE

To evaluate the hypothesis that smoking increases the dependence on bl ood glucose as a fuel, seven male smokers [28.7 +/- 1.7 (SE) yr, 77.7 +/- 4.3 kg] and seven nonsmokers (NS; 29.1 +/- 0.9 yr, 78.7 +/- 5.3 kg ) were studied in the postabsorptive condition. NS received a primed c ontinuous infusion of [6,6-H-2]glucose and [1-C-13]glucose during 90 m in of rest and 60 min of exercise at 49.7 +/- 0.8% of peak O-2 consump tion on one occasion; chronic smokers continued their overnight abstin ence from smoking (CS) for one trial but, on another occasion, acutely smoked (AS) two cigarettes immediately before resting measurements an d another cigarette before exercise. Plasma glucose levels were simila r among all groups at all times during the trials; however, the glucos e rates of appearance (Ra) at rest in CS (1.96 +/- 0.14 mg.kg(-1).min( -1)) and AS (2.02 +/- 0.14) were higher than in NS (1.41 +/- 0.15, P < 0.05). With exercise, the glucose Pa values rose in all groups above resting values but were significantly greater in CS (4.76 +/- 0.50) an d AS (4.71 +/- 0.53) than in NS (3.31 +/- 0.16). Glucose oxidation dur ing exercise was elevated in smokers (2.31 +/- 0.37 mg.kg(-1).min(-1) in CS and 2.18 +/- 0.34 in AS) compared with NS (1.09 +/- 0.18, P < 0. 05). Nicotine levels correlated with the glucose Ra in AS (r = 0.93, P < 0.01). In conclusion, the results indicate that long-term smoking, independent of acute smoking, increases the dependence on blood glucos e as a fuel during rest and sustained submaximal exercise.