Self-administered nicotine differentially impacts body weight gain in obesity-prone and obesity-resistant rats

Abstract

Obesity and tobacco smoking represent the largest challenges to public health, but the causal relationship between nicotine and obesity is poorly understood. Nicotine suppresses body weight gain, a factor impacting smoking initiation and the failure to quit, particularly among obese smokers. The impact of nicotine on body weight regulation in obesity-prone and obesity-resistant populations consuming densely caloric diets is unknown. In the current experiment, body weight gain of adult male rats maintained on a high energy diet (31.8% kcal from fat) distributed into obesity-prone (OP), obesity-resistant (OR) and an intermediate group, which was placed on standard rodent chow (Chow). These rats were surgically implanted with intravenous catheters and allowed to self-administer nicotine (0 or 60μg/kg/infusion, a standard self-administration dose) in 1-h sessions for 20 consecutive days. Self-administered nicotine significantly suppressed body weight gain but not food intake in OP and Chow rats. Self-administered nicotine had no effect on body weight gain in OR rats. These data suggest that: 1) OR rats are also resistant to nicotine-induced suppression of body weight gain; and 2) nicotine may reduce levels of obesity in a subset of smokers prone to obesity.

Keywords: Dietary intake; Drugs; Nicotine; Obesity phenotypes.

Fig. 1

Self-administered nicotine (60 μg/kg/infusion) suppressed body weight gain in OP and Chow rats, but not OR rats (a). Open symbols indicates saline, and filled indicate nicotine groups. For clarity, bar graphs demonstrate suppression of body weight gain in Chow (b), OP (c), and lack of suppression in OR (d) groups after 20 days of self-administration. Data expressed as means ± SEM. *Indicate p < 0.05, between 0 and 60 μg/kg/infusion nicotine within phenotype group.

Fig. 2

Self-administered nicotine (60 μg/kg/infusion) did not impact 24 h food intake, expressed as kcal as a percentage of BW to account for the between subjects design of the experiment, in Chow (a), OP (b), or OR (c) rats after 20 days of self-administration, when nicotine intake was maximal in all groups. Data expressed as means ± SEM. Values within each bar are mean 24 h kcal consumed on Day 20 of the experiment ± SEM.