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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 60?g/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.

SUBMITTER: Rupprecht LE

PROVIDER: S-EPMC6044443 | biostudies-literature | 2017 Jul

REPOSITORIES: biostudies-literature

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

Rupprecht Laura E LE Smith Tracy T TT Donny Eric C EC Sved Alan F AF

Physiology & behavior 20170209

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 ...[more]

PMID: 28189503

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Project description:IntroductionThe action of nicotine to suppress body weight is often cited as a factor impacting smoking initiation and the failure to quit. Despite the weight-suppressant effects of nicotine, smokers and nonsmokers report equal daily caloric intake. The weight-suppressive effects of nicotine in animal models of smoking are poorly understood. Furthermore, the Food and Drug Administration has authority to implement a policy markedly reducing nicotine levels in cigarettes; such a reduction could reduce smoking behavior, but have detrimental effects on body weight. The aim of this investigation was to examine the effects of self-administered nicotine on body weight and food intake in rats.MethodsIn Experiment 1, rats with ad libitum access to chow responded for intravenous infusions of nicotine (60 µg/kg/infusion) or saline in daily 1-hour sessions; body weight and 24-hour food intake were measured. Experiment 2 tested the effects of subcutaneous injections of nicotine on food intake. In Experiment 3, rats were food restricted and self-administered nicotine across a range of doses (3.75-60 µg/kg/infusion) while body weight was measured. In Experiment 4, rats self-administered 60 µg/kg/infusion nicotine before reduction to one of several doses (1.875-15 µg/kg/infusion) for 50 days.ResultsSelf-administered nicotine suppressed weight gain independent of food intake. In food restricted rats, self-administered nicotine dose-dependently suppressed body weight gain. In rats self-administering 60 µg/kg/infusion nicotine, dose reduction increased body weight.ConclusionsSelf-administered nicotine, even at low doses, suppressed body independent of food intake; this may have important implications for nicotine reduction policy.ImplicationsThe results of the present studies demonstrate that self-administered nicotine suppresses body weight independent of food intake in rats. Further, the present studies establish that self-administered nicotine suppresses body weight even at very low doses and that reduction of nicotine dose results in weight gain. These results have important implications for nicotine reduction policy.

Project description:Extracellular matrix (ECM) remodelling of the adipose tissue plays a pivotal role in the pathophysiology of obesity. The lysyl oxidase (LOX) family of amine oxidases, including LOX and LOX-like (LOXL) isoenzymes, controls ECM maturation, and upregulation of LOX activity is essential in fibrosis; however, its involvement in adipose tissue dysfunction in obesity is unclear. In this study, we observed that LOX is the main isoenzyme expressed in human adipose tissue and that its expression is strongly upregulated in samples from obese individuals that had been referred to bariatric surgery. LOX expression was also induced in the adipose tissue from male Wistar rats fed a high-fat diet (HFD). Interestingly, treatment with β-aminopropionitrile (BAPN), a specific and irreversible inhibitor of LOX activity, attenuated the increase in body weight and fat mass that was observed in obese animals and shifted adipocyte size toward smaller adipocytes. BAPN also ameliorated the increase in collagen content that was observed in adipose tissue from obese animals and improved several metabolic parameters - it ameliorated glucose and insulin levels, decreased homeostasis model assessment (HOMA) index and reduced plasma triglyceride levels. Furthermore, in white adipose tissue from obese animals, BAPN prevented the downregulation of adiponectin and glucose transporter 4 (GLUT4), as well as the increase in suppressor of cytokine signaling 3 (SOCS3) and dipeptidyl peptidase 4 (DPP4) levels, triggered by the HFD. Likewise, in the TNFα-induced insulin-resistant 3T3-L1 adipocyte model, BAPN prevented the downregulation of adiponectin and GLUT4 and the increase in SOCS3 levels, and consequently normalised insulin-stimulated glucose uptake. Therefore, our data provide evidence that LOX plays a pathologically relevant role in the metabolic dysfunction induced by obesity and emphasise the interest of novel pharmacological interventions that target adipose tissue fibrosis and LOX activity for the clinical management of this disease.

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

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

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