Metabolite and hormonal response in smokers during rest and sustained exercise

To evaluate the effects of acute and chronic smoking on blood glucose homeostasis, concentrations of metabolites, and hormonal responses at rest and during submaximal exercise, seven male smokers and seven similar nonsmokers were studied after an overnight fast. Nonsmokers (NS) and chronic smokers, abstaining from smoking (CS), were tested during rest and 60 min of cycle ergometry exercise at 49.7 +/- 0.8% of VO2peak. Smokers were restudied after acutely smoking (AS) two cigarettes prior to rest and one prior to exercise. Blood glucose levels were similar among NS, CS, and AS at all times. Lactate levels were elevated in AS compared with NS during exercise (2.32 +/- 0.22 mM vs 1.81 +/- 0.11; P < 0.05), with no differences in alanine. Free fatty acid levels were initially lower at rest in CS (0.45 +/- 0.04 mM) than in either AS (0.77 +/- 0.11) or NS (0.64 +/- 0.06; p < 0.05), but no other differences were found. During exercise, CS had lower glycerol levels (0.31 +/- 0.02 mM) than either AS (0.38 +/- 0.02) or NS (0.41 +/- 0.02; P < 0.05). Nevertheless, respiratory exchange ratio values were not significantly different during steady-state rest or exercise; and insulin, glucagon, and norepinephrine levels were also similar. Smokers effectively maintained normal blood glucose levels with only minor changes in some metabolite and hormone concentrations during rest and sustained exercise.