Changes in circulating lipid and carbohydrate metabolites following systemic nicotine treatment in healthy men

In the present study the influence of low doses of intravenous nicotine administration on hormonal and metabolic events was studied in man in view of the clinical implications of moderate smoking on the development of hyperlipidemia. Hormonal, metabolic and cardiovascular effects of a 30 min intravenous nicotine infusion (0.25 or 0.5 micrograms/kg/ min) were determined in seven non-smoking, healthy, normal weight male individuals after an overnight fast. Nicotine caused a significant dose-dependent increase in the plasma levels of nicotine, cotinine, noradrenaline, adrenaline, glycerol and free fatty acids (FFA). The serum nicotine concentrations peaked at the end of the infusion followed by a gradual decline, although they were still increased 90 min after cessation of infusion. Serum cotinine levels (the main nicotine metabolite) continuously increased during the experiment and statistically significant increases were found from 30 min after the start of infusion of nicotine. Serum noradrenaline, adrenaline, glycerol and FFA levels had increased significantly by 15 min of nicotine infusion. Nicotine produced significant elevations of adrenaline, glycerol and FFA concentrations at both doses (maximal increments of 247, 184 and 153%, respectively) and the peak effect occurred at 30 min. However, noradrenaline levels only responded to the high nicotine dose and the maximal increment (168%) was already found at 15 min. The increments of noradrenaline and adrenaline failed to elicit changes in systolic and diastolic blood pressure or heart rate. Nicotine did not alter plasma levels of glucagon, insulin, glucose, pyruvate or lactate and a non-significant increase in serum cortisol and growth hormone levels was observed. Systemic nicotine administration elevates plasma glycerol levels via a mechanism which is not clarified in detail, but may involve catecholamine release. The present results indicate that this effect seems to be mainly mediated by adrenaline, in view of the absence of changes in noradrenaline levels following low dose nicotine administration. The lipolytic effect of nicotine occurs at nicotine levels which do not affect glucose metabolism, heart rate or blood pressure, indicating that adipose tissue is one of the most sensitive organs to nicotine exposure.