Effect of nicotine and ephedrine on brown adipose fat tissue accumulation of FDG with rodent studies

Abstract

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Objectives: To evaluate the effect of various β-adrenergic agonists on the biodistribution of 18F-FDG in brown adipose fat tissue (BAT).

Methods: Caffeine (10mg/kg BW. n=4), ephedrine (5mg/kg BW. n=4), nicotine (0.8mg/kg BW. n=9), and a mixture of nicotine and ephedrine (5mg/kg BW. n=9) were injected into the intra-peritoneal cavity of female Lewis rats 30 minutes prior to intravenous 18F-FDG injections. One hour after injection of 18F-FDG, the animals were sacrificed and BAT, other major organs and blood were extracted. The biodistribution results were compared to body temperature data.

Results: In the rats injected with nicotine or ephedrine, the mean uptake of 18F-FDG %ID/(g of interscapular BAT tissue)×(kg of body weight) was significantly increased (7.9 fold) compared to the controls. Nicotine had strongest effect on 18F-FDG uptake in brown adipose tissue. Caffeine increased BAT uptake slightly but this did not reach statistical significance. The combination of nicotine and ephedrine increased the uptake more than either nicotine or ephedrine alone. Uptake value of combination of nicotine and ephedrine was 12.0 fold greater than controls. There was no significant change in the uptake of 18F-FDG in other major organs. The effect of nicotine was completely blocked by prior injection of β-adrenergic antagonists. Transient temperature down was observed in the nicotine injected groups and this effect was canceled by prior injection of β-adrenergic antagonists. No significant change of baseline temperature was seen before and after pharmaceutical intervention.

Conclusions: Nicotine caused a greater increase in 18F-FDG uptake in brown adipose tissue than other interventions and the effect was increased when nicotine was combined with ephedrine. The effect of nicotine was completely blocked by prior injection of β-adrenergic antagonists, indicating that β-adrenergic agonists increase the metabolism of BAT.