Effect of short-term cigarette smoke exposure on body weight, appetite and brain neuropeptide Y in mice

Sex-dependent differences in the ability of nicotine to modulate discrimination learning and cognitive flexibility in mice

Nicotine, an addictive compound found in tobacco, functions as an agonist of nicotinic acetylcholine receptors (nAChRs) in the brain. Interestingly, nicotine has been reported to act as a cognitive enhancer in both human subjects and experimental animals. However, its effects in animal studies have not always been consistent, and sex differences have been identified in the effects of nicotine on several behaviors. Specifically, the role that sex plays in modulating the effects of nicotine on discrimination learning and cognitive flexibility in rodents is still unclear. Here, we evaluated sex-dependent differences in the effect of daily nicotine intraperitoneal (i.p.) administration at various doses (0.125, 0.25, and 0.5 mg/kg) on visual discrimination (VD) learning and reversal (VDR) learning in mice. In male mice, 0.5 mg/kg nicotine significantly improved performance in the VDR, but not the VD, task, while 0.5 mg/kg nicotine significantly worsened performance in the VD, but not VDR task in female mice. Furthermore, 0.25 mg/kg nicotine significantly worsened performance in the VD and VDR task only in female mice. Next, to investigate the cellular mechanisms that underlie the sex difference in the effects of nicotine on cognition, transcriptomic analyses were performed focusing on the medial prefrontal cortex tissue samples from male and female mice that had received continuous administration of nicotine for 3 or 18 days. As a result of pathway enrichment analysis and protein-protein interaction analysis using gene sets of differentially expressed genes, decreased expression of postsynaptic-related genes in males and increased expression of innate immunity-related genes in females were identified as possible molecular mechanisms related to sex differences in the effects of nicotine on cognition in discrimination learning and cognitive flexibility. Our result suggests that nicotine modulates cognitive function in a sex-dependent manner by alternating the expression of specific gene sets in the medial prefrontal cortex.

The causal relationship of cigarette smoking to metabolic disease risk and the possible mediating role of gut microbiota

BACKGROUND

Cigarette smoking is a leading cause of preventable death worldwide, with its associated diseases and conditions. Emerging evidence suggests that cigarette smoking contributes to a range of pathological metabolic injuries, including diabetes and nonalcoholic fatty liver disease (NAFLD). The impact of gut microbiota on metabolic health and diseases has been observed, but the causality remains uncertain.

OBJECTIVE

To confirm the causal relationship between cigarette smoking and metabolic diseases, and to investigate the possible mediating effect of gut microbiota on these connections.

METHODS

The relationships among cigarette smoking, metabolic diseases, and the gut microbiome were analyzed by Univariate Mendelian randomization (UVMR). Furthermore, to mitigate the impact of confounding factors, adjusted models were conducted via the multivariate Mendelian randomization (MVMR) method, aiming to improve the accuracy of prediction. Ultimately, the study evaluated the effect of the intermediary factor, gut microbiome, on the relationship between cigarette smoke and metabolic diseases.

RESULTS

The phenomenon that a causal relationship between cigarette smoke (249752 individuals) and gut microbiota (7738 individuals), diabetes (406831 individuals), NAFLD (377998 individuals), hypercholesterolaemia (463010 individuals), and obesity (463010 individuals) was observed using UVMR. In the MVMR model, the genetic connection between cigarette smoking, gut microbiota, and type 2 diabetes remained significant. Of note, paraprevotella_clara served an important mediating role in the type 2 diabetes associated with cigarette smoke.

CONCLUSION

This work offered genetic evidence linking cigarette smoke to metabolic diseases, suggesting that the gut microbiota, particularly paraprevotella_clara, might be a crucial mediator in the development of type 2 diabetes caused by cigarette smoke. Our future studies should consider conducting other ethnic groups MR analyses, particularly with larger sample sizes. Still, more in vivo and in vitro work should be carried out to validate the precise effect and molecular mechanisms of the gut microbiome.

Interplay of Oxidative Stress, Gut Microbiota, and Nicotine in Metabolic-Associated Steatotic Liver Disease (MASLD)

Oxidative stress has been described as one of the main drivers of intracellular damage and metabolic disorders leading to metabolic syndrome, a major health problem worldwide. In particular, free radicals alter lipid metabolism and promote lipid accumulation in the liver, existing in the hepatic facet of metabolic syndrome, the metabolic dysfunction-associated steatotic liver disease (MASLD). Recent literature has highlighted how nicotine, especially if associated with a high-fat diet, exerts a negative effect on the induction and progression of MASLD by upregulating inflammation and increasing oxidative stress, abdominal fat lipolysis, and hepatic lipogenesis. Moreover, considerable evidence shows the central role of intestinal dysbiosis in the pathogenesis of MASLD and the impact of nicotine-induced oxidative stress on the gut microbiome. This results in an intricate network in which oxidative stress stands at the intersection point between gut microbiome, nicotine, and MASLD. The aim of this review is to delve into the molecular mechanisms linking tobacco smoking and MASLD, focusing on nicotine-induced microbiota modifications and their impact on MASLD development.

Sex- and age-dependent impacts of nicotine and ethanol binge drinking on the brain: Insights from preclinical research

Electronic cigarette use among adolescents is a growing concern, not only due to the high incidence of co-use with other substances, such as alcohol, but also due to the fact brain is still maturing during this period. Combined exposure to alcohol and nicotine leads to plastic adaptation of crucial circuits in the brain, which can contribute to the development of addiction. It is well established that nicotine exposure can facilitate alcohol binge drinking, and vice-versa, in a sex-, age- and exposure-dependent manner. Nonetheless, the central mechanisms underlying the synergistic relationship between these two substances and the emergence of differential behavioural traits dependent on these factors remain underexplored. Preclinical studies continue to provide valuable insights into such mechanisms. Here, we discuss recent preclinical findings that report behavioural changes characteristic of addiction following nicotine consumption, primarily in models of vaping and alcohol use; and insights into the neural mechanisms impacted by intake of these two substances, with a focus on the adolescent brain.

The association of smoking with different eating and dietary behaviours: A cross-sectional analysis of 80 296 United Kingdom adults

BACKGROUND AND AIMS

Smokers typically have a lower body mass index (BMI) than non-smokers, while smoking cessation is associated with weight gain. In pre-clinical research, nicotine in tobacco smoking suppresses appetite and influences subsequent eating behaviour; however, this relationship is unclear in humans. This study measured the associations of smoking with different eating and dietary behaviours.

DESIGN

A cross-sectional analysis of data from health assessments conducted between 2004 and 2022.

SETTING

An independent healthcare-based charity within the United Kingdom.

PARTICIPANTS

A total of 80 296 men and women (mean ± standard deviation [SD]: age, 43.0 ± 10.4 years; BMI, 25.7 ± 4.2 kg/m2; 62.5% male) stratified into two groups based on their status as a smoker (n = 6042; 7.5%) or non-smoker (n = 74 254; 92.5%).

MEASUREMENTS

Smoking status (self-report) was the main exposure, while the primary outcomes were selected eating and dietary behaviours. Age, sex and socioeconomic status (index of multiple deprivation [IMD]) were included as covariates and interaction terms, while moderate-to-vigorous exercise and sleep quality were included as covariates only.

FINDINGS

Smokers had lower odds of snacking between meals and eating food as a reward or out of boredom versus non-smokers (all odds ratio [OR] ≤ 0.82; P < 0.001). Furthermore, smokers had higher odds of skipping meals, going more than 3 h without food, adding salt and sugar to their food, overeating and finding it hard to leave something on their plate versus non-smokers (all OR ≥ 1.06; P ≤ 0.030). Additionally, compared with non-smokers, smoking was associated with eating fried food more times per week (rate ratio [RR] = 1.08; P < 0.001), eating fewer meals per day, eating sweet foods between meals and eating dessert on fewer days per week (all RR ≤ 0.93; P < 0.001). Several of these relationships were modified by age, sex and IMD.

CONCLUSIONS

Smoking appears to be associated with eating and dietary behaviours consistent with inhibited food intake, low diet quality and altered food preference. Several of these relationships are moderated by age, sex and socioeconomic status.

Causal effects from tobacco smoking initiation on obesity-related traits: a Mendelian randomization study

BACKGROUND

There is a widespread notion that tobacco smoking controls weight based on the appetite suppressive effect of nicotine. However, the causal relationship between smoking initiation and obesity-related traits in the general population are unclear.

METHODS

This Mendelian randomization analysis utilized 378 genetic variants associated with tobacco smoking initiation (usually in adolescence or young adulthood) identified in a genome-wide association study (meta-analysis) of 1.2 million individuals. Outcome data for body mass index, waist circumference, hip circumference, and waist-to-hip ratio were extracted from the 337,138 white British-ancestry UK Biobank participants aged 40-69 years. Replication analyses were performed for genome-wide association study meta-analysis for body mass index, including the GERA/GIANT data including 364,487 samples from mostly European individuals. In addition, summary-level Mendelian randomization by inverse variance weighted method and pleiotropy-robust Mendelian randomization methods, including median-based and MR-Egger regression, was performed.

RESULTS

Summary-level Mendelian randomization analysis indicated that genetically predicted smoking initiation is causally linked to higher body mass index [+0.28 (0.18-0.38) kg/m2], waist circumference [+0.88 (0.66-1.10) cm], hip circumference [+0.40 (0.23-0.57) cm], and waist-to-hip ratio [+0.006 (0.005-0.007)]. These results were consistent with those of the pleiotropy-robust Mendelian randomization analysis. Additionally, in replication analysis, genetically predicted smoking initiation was significantly associated with a higher body mass index [+0.03 (0.01, 0.05] kg/m2).

CONCLUSION

Tobacco initiation may lead to worse obesity-related traits in the general 40- to 69-year-old individuals. Therefore, tobacco-use initiation as a long-term weight-control measure should be discouraged.

The association between chemical constituents of ambient fine particulate matter and obesity in adults: A large population-based cohort study

OBJECTIVES

Current evidence demonstrated that ambient fine particulate matter with an aerodynamic diameter ≤2.5 μm (PM2.5) and its constituents may be obesogenic in children, but evidence from adults is lacking. Our aim was to characterize the association between PM2.5 and its constituents and obesity in adults.

METHODS

We included 68,914 participants from the China Multi-Ethnic Cohort (CMEC) baseline survey. Three-year average concentrations of PM2.5 and its constituents were evaluated by linking pollutant estimates to the geocoded residential addresses. Obesity was defined as body mass index (BMI) ≥ 28 kg/m2. Logistic regression was used to examine the relationship between PM2.5 and its constituents and obesity. We performed weighed quantile sum (WQS) regression to get the overall effect of PM2.5 and its constituents and the relative contribution of each constituent.

RESULTS

Per-SD increase in PM2.5 (odds ratio [OR] = 1.43, 95% confidence interval [CI]: 1.37-1.49), black carbon (BC) (1.42, 1.36-1.48), ammonium (1.43, 1.37-1.49), nitrate (1.44, 1.38-1.50), organic matter (OM) (1.45, 1.39-1.51), sulfate (1.42, 1.35-1.48), and soil particles (SOIL) (1.31, 1.27-1.36) were positively associated with obesity, and SS (0.60, 0.55-0.65) was negatively associated with obesity. The overall effect (OR = 1.34, 95% CI: 1.29-1.41) of the PM2.5 and its constituents was positively associated with obesity, and ammonium made the most contribution to this relationship. Participants who were older, female, never smoked, lived in urban areas, had lower income or higher levels of physical activity were more significantly adversely affected by PM2.5, BC, ammonium, nitrate, OM, sulfate and SOIL compared to other individuals.

CONCLUSION

Our study revealed that PM2.5 constituents except SS were positively associated with obesity, and ammonium played the most important role. These findings provided new evidence for public health interventions, especially the precise prevention and control of obesity.

Modeling the effects of cigarette smoke extract on influenza B virus infections in mice

Influenza B virus (IBV) is a major respiratory viral pathogen. Due to a lack of pandemic potential for IBV, there is a lag in research on IBV pathology and immunological responses compared to IAV. Therefore, the impact of various lifestyle and environmental factors on IBV infections, such as cigarette smoking (CS), remains elusive. Despite the increased risk and severity of IAV infections with CS, limited information exists on the impact of CS on IBV infections due to the absence of suitable animal models. To this end, we developed an animal model system by pre-treating mice for two weeks with cigarette smoke extract (CSE), then infected them with IBV and monitored the resulting pathological, immunological, and virological effects. Our results reveal that the CSE treatment decreased IBV specific IgG levels yet did not change viral replication in the upper airway/the lung, and weight recovery post infection. However, higher concentrations of CSE did result in higher mortality post infection. Together, this suggests that CS induced inflammation coupled with IBV infection resulted in exacerbated disease outcome.

Modulation of mouse laryngeal inflammatory and immune cell responses by low and high doses of mainstream cigarette smoke

Cigarette smoking is a major risk factor for laryngeal diseases. Despite well-documented cigarette smoke (CS) induced laryngeal histopathological changes, the underlying immunopathological mechanisms remain largely unexplored. The goal of this study was to evaluate inflammatory and immune cell responses in a CS-exposed larynx. Specifically, we used a 4-week subacute whole-body CS inhalation mouse model to assess these responses in the laryngeal mucosa upon exposure to low (LD; 1 h/day) and high dose (HD; 4 h/day) CS. Laryngeal tissues were harvested and evaluated using a 254-plex NanoString inflammation panel and neutrophil/macrophage/T-cell immunohistochemistry (IHC). NanoString global and differential gene expression analysis revealed a unique expression profile only in the HD group, with 26 significant differentially expressed genes (DEGs). StringDB KEGG pathway enrichment analysis revealed the involvement of these DEGs with pro-inflammatory pathways including TNF/TNFα and IL-17. Furthermore, inflammatory responses remained inhibited in conjunction with predicted activated states of anti-inflammatory regulators like PPARγ and NFE2L2 upon Ingenuity Pathway Analysis (IPA). Subglottic T-cell levels remained significantly inhibited as corroborated by IPA predictions. Overall, our key findings are consistent with HD exposures being anti-inflammatory and immunosuppressive. Furthermore, the identification of important regulatory genes and enriched pathways may help improve clinical interventions for CS-induced laryngeal diseases.

Effects of Cigarette Smoke Exposure on the Gut Microbiota and Liver Transcriptome in Mice Reveal Gut–Liver Interactions

Cigarette smoke exposure has a harmful impact on health and increases the risk of disease. However, studies on cigarette-smoke-induced adverse effects from the perspective of the gut–liver axis are lacking. In this study, we evaluated the adverse effects of cigarette smoke exposure on mice through physiological, biochemical, and histopathological analyses and explored cigarette-smoke-induced gut microbiota imbalance and changes in liver gene expression through a multiomics analysis. We demonstrated that cigarette smoke exposure caused abnormal physiological indices (including reduced body weight, blood lipids, and food intake) in mice, which also triggered liver injury and induced disorders of the gut microbiota and liver transcriptome (especially lipid metabolism). A significant correlation between intestinal bacterial abundance and the expression of lipid-metabolism-related genes was detected, suggesting the coordinated regulation of lipid metabolism by gut microbiota and liver metabolism. Specifically, Salmonella (harmful bacterium) was negatively and positively correlated with up- (such as Acsl3 and Me1) and downregulated genes (such as Angptl4, Cyp4a12a, and Plin5) involved in lipid metabolism, while Ligilactobacillus (beneficial bacterium) showed opposite trends with these genes. Our results clarified the key role of gut microbiota in liver damage and metabolism and improved the understanding of gut–liver interactions caused by cigarette smoke exposure.

Effects of Cigarette Smoke on Adipose and Skeletal Muscle Tissue: In Vivo and In Vitro Studies

Chronic obstructive pulmonary disease (COPD), often caused by smoking, is a chronic lung disease with systemic manifestations including metabolic comorbidities. This study investigates adaptive and pathological alterations in adipose and skeletal muscle tissue following cigarette smoke exposure using in vivo and in vitro models. Mice were exposed to cigarette smoke or air for 72 days and the pre-adipose cell line 3T3-L1 was utilized as an in vitro model. Cigarette smoke exposure decreased body weight, and the proportional loss in fat mass was more pronounced than the lean mass loss. Cigarette smoke exposure reduced adipocyte size and increased adipocyte numbers. Adipose macrophage numbers and associated cytokine levels, including interleukin-1β, interleukine-6 and tumor necrosis factor-α were elevated in smoke-exposed mice. Muscle strength and protein synthesis signaling were decreased after smoke exposure; however, muscle mass was not changed. In vitro studies demonstrated that lipolysis and fatty acid oxidation were upregulated in cigarette smoke-exposed pre-adipocytes. In conclusion, cigarette smoke exposure induces a loss of whole-body fat mass and adipose atrophy, which is likely due to enhanced lipolysis.

Short-term exposure to JUUL electronic cigarettes can worsen ischemic stroke outcome

BACKGROUND

The short and long-term health effects of JUUL electronic cigarette (e-Cig) are largely unknown and warrant extensive research. We hypothesized that JUUL exposure could cause cerebrovascular toxicities impacting the progression and outcome of ischemic stroke comparable to tobacco smoke (TS) exposure.

METHODS

We exposed male C57 mice to TS/JUUL vapor for 14 days. LCMS/MS was used to measure brain and plasma nicotine and cotinine level. Transient middle cerebral artery occlusion (tMCAO) followed by reperfusion was used to mimic ischemic stroke. Plasma levels of IL-6 and thrombomodulin were assessed by enzyme-linked immunosorbent assay. At the same time, western blotting was used to study blood-brain barrier (BBB) tight junction (TJ) proteins expression and key inflammatory and oxidative stress markers.

RESULTS

tMCAO upregulated IL-6 and decreased plasma thrombomodulin levels. Post-ischemic brain injury following tMCAO was significantly worsened by JUUL/TS pre-exposure. TJ proteins expression was also downregulated by JUUL/TS pre-exposure after tMCAO. Like TS, exposure to JUUL downregulated the expression of the antioxidant Nrf2. ICAM-1 was upregulated in mice subjected to tMCAO following pre-exposure to TS or JUUL, with a greater effect of TS than JUUL.

CONCLUSIONS

These results suggest that JUUL exposure could negatively impact the cerebrovascular system, although to a lesser extent than TS exposure.

Understanding the Effects of Antipsychotics on Appetite Control

Antipsychotic drugs (APDs) represent a cornerstone in the treatment of schizophrenia and other psychoses. The effectiveness of the first generation (typical) APDs are hampered by so-called extrapyramidal side effects, and they have gradually been replaced by second (atypical) and third-generation APDs, with less extrapyramidal side effects and, in some cases, improved efficacy. However, the use of many of the current APDs has been limited due to their propensity to stimulate appetite, weight gain, and increased risk for developing type 2 diabetes and cardiovascular disease in this patient group. The mechanisms behind the appetite-stimulating effects of the various APDs are not fully elucidated, partly because their diverse receptor binding profiles may affect different downstream pathways. It is critical to identify the molecular mechanisms underlying drug-induced hyperphagia, both because this may lead to the development of new APDs, with lower appetite-stimulating effects but also because such insight may provide new knowledge about appetite regulation in general. Hence, in this review, we discuss the receptor binding profile of various APDs in relation to the potential mechanisms by which they affect appetite.

Anatabine, Nornicotine, and Anabasine Reduce Weight Gain and Body Fat through Decreases in Food Intake and Increases in Physical Activity

Obesity is a leading cause of preventable death in the United States. Currently approved pharmacotherapies for the treatment of obesity are associated with rebound weight gain, negative side effects, and the potential for abuse. There is a need for new treatments with fewer side effects. Minor tobacco alkaloids (MTAs) are potential candidates for novel obesity pharmacotherapies. These alkaloids are structurally related to nicotine, which can help reduce body weight, but without the same addictive potential. The purpose of the current study was to examine the effects of three MTAs (nornicotine, anatabine, and anabasine) and nicotine on weight gain, body composition, chow intake, and physical activity. We hypothesized that the MTAs and nicotine would reduce weight gain through reductions in chow intake and increases in physical activity. To test this, male Sprague Dawley rats were housed in metabolic phenotyping chambers. Following acclimation to these chambers and to (subcutaneous (sc)) injections of saline, animals received daily injections (sc) of nornicotine, anabasine, anatabine, or nicotine for one week. Compared to saline-injected animals that gained body weight and body fat during the treatment phase, injections of nornicotine and anatabine prevented additional weight gain, alongside reductions in body fat. Rats receiving anabasine and nicotine gained body weight at a slower rate relative to rats receiving saline injections, and body fat remained unchanged. All compounds reduced the intake of chow pellets. Nornicotine and nicotine produced consistent increases in physical activity 6 h post-injection, whereas anabasine’s and anatabine’s effects on physical activity were more transient. These results show that short-term, daily administration of nornicotine, anabasine, and anatabine has positive effects on weight loss, through reductions in body fat and food intake and increases in physical activity. Together, these findings suggest that MTAs are worthy of further investigations as anti-obesity pharmacotherapies.

Smoking and obesity among long-haul truck drivers in France

INTRODUCTION

This study examines the health status of long-haul truck drivers (LHTDs) and more specifically smoking and obesity, in France.

METHODS

A total of 373 French and other LHTDs were randomly interviewed at six highway rest stops. Variables recorded were self-reported sociodemographic characteristics (age, gender, marital status, and nationality), behavioral variables (consumption of sodas, daily exercise, smoking status), weight and height. Body mass index (BMI) was also calculated. Statistical analysis was conducted using chi-squared analysis and multiple logistic ordinal regression models (MLR) were developed.

RESULTS

The mean age was 43.4 and the largest proportion (41.2%) of respondents were aged 40–50 years. Most respondents were French (70.3%), married (73.8%) and did not report having an active exercise routine (66.0%). Almost two-thirds of the drivers consumed daily 1–2 sodas (34.2%) or 3–4 sodas (33.2%). Based on the BMI, respondents were divided into normal (34.3%), overweight (39.8%), obese (19.5%) or morbidly obese (9.4%) categories. The mean BMI was 27.9 kg/m² and 51.1% of LHTDs were current or active smokers. MLR analysis revealed that French LHTDs were more likely (OR=3.04; 95% CI: 1.62–5.69) to have a normal BMI compared to other drivers. Smokers were significantly more likely than non-smokers (OR=2.12; 95% CI: 1.26–3.58) to have an above normal BMI.

CONCLUSIONS

These results confirm that French and other LHTDs are at high risk of non-communicable diseases. They also highlight the need to address the health risks associated with smoking and obesity among LHTDs using multifaceted strategies.

Cigarette smoke exposure causes systemic and autonomic cardiocirculatory changes in rats depending on the daily exposure dose

AIMS

To evaluate the systemic changes and autonomic cardiocirculatory control of awaken rats chronically exposed to the cigarette smoke (CS) of 1 or 2 cigarettes/day.

MAIN METHODS

Rats were exposed to clean air (control) or cigarette smoke of 1 (CS1) or 2 (CS2) cigarettes/animal/day for 30 days. Then, arterial pressure (AP) and heart rate (HR) were recorded in conscious rats to assess spontaneous baroreflex sensitivity and HR and AP variabilities. Evoked baroreflex and cardiac autonomic tone were evaluated by vasoactive drugs and autonomic blockers, respectively. In another group, ventilatory and cardiovascular parameters were recorded under hypoxia and hypercapnia stimulus. At the end of protocols, heart, lung, kidneys and liver were collected for histological analysis.

KEY FINDINGS

Rats exposed to CS showed morphological changes, being more evident in the CS2 group. Also, less weight gain and cardiac hypertrophy were prominent in CS2 rats. Basal AP and HR, spontaneous baroreflex sensitivity and cardiovascular variabilities were similar among groups. CS exposure progressively blunted the bradycardia response to phenylephrine (-2.2 ± 0.1 vs. -1.7 ± 0.2 vs. -1.5 ± 0.2) while the tachycardia response to sodium nitroprusside was slightly increased compared to control. Vagal tone was not affected by CS, but CS2 rats exhibited higher sympathetic tone (-25 ± 4 vs. -28 ± 4 vs. -56 ± 9) and lower intrinsic HR (411 ± 4 vs. 420 ± 8 vs. 390 ± 6). Exposure to CS of 2 cigarettes also exacerbated the reflex cardiovascular and ventilatory responses to hypoxia and hypercapnia.

SIGNIFICANCE

CS exposure for 30 days promoted systemic changes and autonomic cardiocirculatory dysfunction in rats depending on the daily exposure dose.

Two Weeks of Smoking Cessation Reverse Cigarette Smoke-Induced Skeletal Muscle Atrophy and Mitochondrial Dysfunction in Mice

INTRODUCTION

Apart from its adverse effects on the respiratory system, cigarette smoking also induces skeletal muscle atrophy and dysfunction. Whether short-term smoking cessation can restore muscle mass and function is unknown. We, therefore, studied the impact of 1- and 2-week smoking cessation on skeletal muscles in a mouse model.

METHODS

Male mice were divided into four groups: Air-exposed (14 weeks); cigarette smoke (CS)-exposed (14 weeks); CS-exposed (13 weeks) followed by 1-week cessation; CS-exposed (12 weeks) followed by 2 weeks cessation to examine exercise capacity, physical activity levels, body composition, muscle function, capillarization, mitochondrial function and protein expression in the soleus, plantaris, and diaphragm muscles.

RESULTS

CS-induced loss of body and muscle mass was significantly improved within 1 week of cessation due to increased lean and fat mass. Mitochondrial respiration and protein levels of the respiratory complexes in the soleus were lower in CS-exposed mice, but similar to control values after 2 weeks of cessation. Exposing isolated soleus muscles to CS extracts reduced mitochondrial respiration that was reversed after removing the extract. While physical activity was reduced in all groups, exercise capacity, limb muscle force, fatigue resistance, fiber size and capillarization, and diaphragm cytoplasmic HIF-1α were unaltered by CS-exposure. However, CS-induced diaphragm atrophy and increased capillary density were not seen after 2 weeks of smoking cessation.

CONCLUSION

In male mice, 2 weeks of smoking cessation reversed smoking-induced mitochondrial dysfunction, limb muscle mass loss, and diaphragm muscle atrophy, highlighting immediate benefits of cessation on skeletal muscles.

IMPLICATIONS

Our study demonstrates that CS-induced skeletal muscle mitochondrial dysfunction and atrophy are significantly improved by 2 weeks of cessation in male mice. We show for the first time that smoking cessation as short as 1 to 2 weeks is associated with immediate beneficial effects on skeletal muscle structure and function with the diaphragm being particularly sensitive to CS-exposure and cessation. This could help motivate smokers to quit smoking as early as possible. The knowledge that smoking cessation has potential positive extrapulmonary effects is particularly relevant for patients referred to rehabilitation programs and those admitted to hospitals suffering from acute or chronic muscle deterioration yet struggling with smoking cessation.

Ebselen prevents cigarette smoke-induced gastrointestinal dysfunction in mice

Gastrointestinal (GI) dysfunction is a common comorbidity of chronic obstructive pulmonary disease (COPD) for which a major cause is cigarette smoking (CS). The underlying mechanisms and precise effects of CS on gut contractility, however, are not fully characterised. Therefore, the aim of the present study was to investigate whether CS impacts GI function and structure in a mouse model of CS-induced COPD. We also aimed to investigate GI function in the presence of ebselen, an antioxidant that has shown beneficial effects on lung inflammation resulting from CS exposure. Mice were exposed to CS for 2 or 6 months. GI structure was analysed by histology and immunofluorescence. After 2 months of CS exposure, ex vivo gut motility was analysed using video-imaging techniques to examine changes in colonic migrating motor complexes (CMMCs). CS decreased colon length in mice. Mice exposed to CS for 2 months had a higher frequency of CMMCs and a reduced resting colonic diameter but no change in enteric neuron numbers. Ten days cessation after 2 months CS reversed CMMC frequency changes but not the reduced colonic diameter phenotype. Ebselen treatment reversed the CS-induced reduction in colonic diameter. After 6 months CS, the number of myenteric nitric-oxide producing neurons was significantly reduced. This is the first evidence of colonic dysmotility in a mouse model of CS-induced COPD. Dysmotility after 2 months CS is not due to altered neuron numbers; however, prolonged CS-exposure significantly reduced enteric neuron numbers in mice. Further research is needed to assess potential therapeutic applications of ebselen in GI dysfunction in COPD.

Maternal High Fat Diet Consumption Exaggerates Metabolic Disorders in Mice With Cigarette-Smoking Induced Intrauterine Undernutrition

Objectives: Maternal smoking causes fetal underdevelopment and results in births which are small for gestation age due to intrauterine undernutrition, leading to various metabolic disorders in adulthood. Furthermore, postnatal high fat diet (HFD) consumption is also a potent obesogenic factor, which can interact with maternal smoking. In this study, we aimed to determine whether maternal HFD consumption during pregnancy can reverse the adverse impact of maternal smoking and change the response to postnatal HFD consumption.

Methods: Female mice were exposed to cigarette smoke (SE, 2 cigarettes/day) or sham exposed for 5 weeks before mating, with half of the SE dams fed HFD (43% fat, SE+HFD). The same treatment continued throughout gestation and lactation. Male offspring from each maternal group were fed the same HFD or chow after weaning and sacrificed at 13 weeks.

Results: Maternal SE alone increased body weight and fat mass in HFD-fed offspring, while SE+HFD offspring showed the highest energy intake and glucose metabolic disorder in adulthood. In addition, postnatal HFD increased the body weight and aggravated the metabolic disorder caused by maternal SE and SE+HFD.

Conclusions: Maternal HFD consumption could not ameliorate the adverse effect of maternal SE but exaggerate metabolic disorders in adult offspring. Smoking cessation and a healthy diet are needed during pregnancy to optimize the health outcome in the offspring.

Associations between smoking, sex hormone levels and late-onset hypogonadism in men differ depending on age

Few studies have investigated whether associations between smoking, sex hormone levels, and symptoms of late-onset hypogonadism (LOH) in men are affected by age. This multi-center, cross-sectional study involving 6,296 men aged 40-79 years was conducted between June 1, 2013 and August 31, 2016 in 6 provinces of China. Total testosterone, free testosterone, and Aging Males’ Symptoms scale (AMS) scores were compared depending on smoking status and the number of cigarettes smoked. Total testosterone was higher in smokers than in non-smokers in all except the 70-79 year old subgroup. Free testosterone was higher in smokers than non-smokers for the 40-49 and 50-59 year old subgroups, but not the 60-69 and 70-79 year old subgroups. Total testosterone was positively associated with number of cigarettes consumed in smokers aged 40-49 and 50-59 years. Sexual and somatic AMS scores were higher in current and ex-smokers than in non-smokers in all age subgroups from 40 to 79 years and were negatively associated with cigarette consumption in smokers aged 40-49 years. These results indicate that, as men age, the positive association between smoking and testosterone weakens, while the positive association between smoking and LOH symptoms becomes stronger.

The Confounders of Cancer Immunotherapy: Roles of Lifestyle, Metabolic Disorders and Sociological Factors

Checkpoint blockade immunotherapy (CPI) is an effective treatment option for many types of cancers. Irrespective of its wide clinical implications, the overall efficacy remains unpredictable and even poor in certain pathologies such as breast cancer. Thus, it is imperative to understand the role of factors affecting its responsiveness. In this review, we provide an overview on the involvement of sociological factors, lifestyles and metabolic disorders in modulating the CPI response in patients from multiple malignancies. Lifestyle habits including exercise, and diet promoted therapeutic responsiveness while alcohol consumption mitigated the CPI effect by decreasing mutational burden and hampering antigen presentation by dendritic cells. Metabolic disorder such as obesity was recognized to enhance the PD-1 expression while diabetes and hypertension were consequences of CPI therapy rather than causes. Among the sociologic factors, sex and race positively influenced the CPI effectiveness on account of increased effector T cell activity and increased PD-1 expression while ageing impaired CPI responsiveness by decreasing functional T cell and increased toxicity. The combined effect of these factors was observed for obesity and gender, in which obese males had the most significant effect of CPI. Therefore these variables should be carefully considered before treating patients with CPI for optimal treatment outcome.

Nicotine' actions on energy balance: Friend or foe?

Obesity has reached pandemic proportions and is associated with severe comorbidities, such as type 2 diabetes mellitus, hepatic and cardiovascular diseases, and certain cancer types. However, the therapeutic options to treat obesity are limited. Extensive epidemiological studies have shown a strong relationship between smoking and body weight, with non-smokers weighing more than smokers at any age. Increased body weight after smoking cessation is a major factor that interferes with their attempts to quit smoking. Numerous controlled studies in both humans and rodents have reported that nicotine, the main bioactive component of tobacco, exerts a marked anorectic action. Furthermore, nicotine is also known to modulate energy expenditure, by regulating the thermogenic activity of brown adipose tissue (BAT) and the browning of white adipose tissue (WAT), as well as glucose homeostasis. Many of these actions occur at central level, by controlling the activity of hypothalamic neuropeptide systems such as proopiomelanocortin (POMC), or energy sensors such as AMP-activated protein kinase (AMPK). However, direct impact of nicotine on metabolic tissues, such as BAT, WAT, liver and pancreas has also been described. Here, we review the actions of nicotine on energy balance. The relevance of this interaction is interesting, because considering the restricted efficiency of obesity treatments, a possible complementary approach may focus on compounds with known pharmacokinetic profile and pharmacological actions, such as nicotine or nicotinic acetylcholine receptors signaling.

Varenicline rescues nicotine-induced decrease in motivation for sucrose reinforcement

Varenicline is one of the top medications used for smoking cessation and is often prescribed before termination of nicotine use. The effect of this combined nicotine and varenicline use on the reward system and motivation for primary reinforcement is underexplored. The goal of this study was to assess the effects of nicotine and varenicline on motivation for a food reinforcer. In Experiment 1, we first assessed the responding for sucrose after pretreatment with nicotine (0, 0.1, or 0.4 mg/kg) and varenicline (0.0, 0.1, 1.0 mg/kg) using a behavioral economics approach. The responding for sucrose was then assessed using a progressive ratio schedule of reinforcement after pretreatment with all possible combinations of nicotine and varenicline doses. In Experiment 2, rats were assessed for the consumption of sucrose in home cages after pretreatment with nicotine and varenicline. We found that (a) nicotine decreased economic demand for sucrose, (b) varenicline rescued nicotine-induced reduction in economic demand for sucrose, and (c) history of varenicline treatment predicted responding for sucrose on a progressive ratio schedule of reinforcement where rats with a history of varenicline treatment responded significantly lower for sucrose across nicotine doses than rats that had not been exposed to varenicline. The results of Experiment 2 largely confirmed that nicotine decreases motivation for sucrose using a passive consumption protocol and that varenicline rescues this effect. Overall, these findings suggest that varenicline interacts with the effects of nicotine by restoring nicotine-induced reduction in motivation for appetitive rewards.

Effects of Human Umbilical Cord-Derived Mesenchymal Stem Cells on the Acute Cigarette Smoke-Induced Pulmonary Inflammation Model

Cigarette smoke (CS) has been reported to induce oxidative stress and inflammatory process in the lungs. However, the role of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) in the regulation of pulmonary inflammation remains unclear. The objective of this study is to investigate the effects of hUC-MSCs on lung inflammation in the acute CS-induced pulmonary inflammation animal model. Eight-week-old male C57BL/6 mice were intravenously administered 3 × 10⁶, 1 × 10⁷, and 3 × 10⁷ cells/kg of hUC-MSCs as well as normal saline alone (control) after 3 days of CS exposure. Mice exposed to high-efficiency particulate air (HEPA)-filtered room air served as the CS control group. High-dose (3 × 10⁷ cells/kg) hUC-MSC administration significantly decreased tumor necrosis factor (TNF)-α in the bronchoalveolar lavage fluid (BALF) of CS-exposed mice (p < 0.05). The chemokine (CXC motif) ligand 1/keratinocyte chemoattractant (CXCL1/KC) in BALF were significantly reduced by low-dose (3 × 10⁶ cells/kg) and high-dose (3 × 10⁷ cells/kg) hUC-MSC (p < 0.05). Medium-dose hUC-MSC administration decreased interleukin (IL)-1β in lung of mice, and TNF-α and caspase-3 were decreased in the lung of CS-exposed mice by medium- and high-dose MSC (p < 0.05). Low-dose hUC-MSCs significantly elevated serum CXCL1/KC and IL-1β in CS-exposed mice (p < 0.05). Our results suggest that high-dose hUC-MSCs reduced pulmonary inflammation and had antiapoptotic effects in acute pulmonary inflammation.

Effects of sex and chronic cigarette smoke exposure on the mouse cecal microbiome

RATIONALE

Chronic smoke exposure is associated with weight loss in patients with Chronic Obstructive Pulmonary Disease (COPD). However, the biological contribution of chronic smoking and sex on the cecal microbiome has not been previously investigated.

METHODS

Adult male, female and ovariectomized mice were exposed to air (control group) or smoke for six months using a standard nose-only smoke exposure system. DNA was extracted from the cecal content using the QIAGEN QIAamp® DNA Mini Kit. Droplet digital PCR was used to generate total 16S bacterial counts, followed by Illumina MiSeq® analysis to determine microbial community composition. The sequencing data were resolved into Amplicon Sequence Variants and analyzed with the use of QIIME2®. Alpha diversity measures (Richness, Shannon Index, Evenness and Faith's Phylogenetic Diversity) and beta diversity (based on Bray-Curtis distances) were assessed and compared according to smoke exposure and sex.

RESULTS

The microbial community was different between male and female mice, while ovariectomy made the cecal microbiome similar to that of male mice. Chronic smoke exposure led to significant changes in the cecal microbial community in both male and female mice. The organism, Alistipes, was the most consistent bacteria identified at the genus level in the cecal content that was reduced with chronic cigarette exposure and its expression was positively related to the whole-body weight of these mice.

CONCLUSION

Chronic smoke exposure is associated with changes in the cecal content microbiome; these changes may play a role in the weight changes that are observed in cigarette smokers.

Nicotinic Acetylcholine Receptor Signaling in the Hypothalamus: Mechanisms Related to Nicotine's Effects on Food Intake

Despite health risks associated with smoking, up to 20% of the US population persist in this behavior; many smoke to control body weight or appetite, and fear of post-cessation weight gain can motivate continued smoking. Nicotine and tobacco use is associated with lower body weight, and cessation yields an average weight gain of about 4 kg, which is thought to reflect a return to the body weight of a typical nonsmoker. Nicotine replacement therapies can delay this weight gain but do not prevent it altogether, and the underlying mechanism for how nicotine is able to reduce weight is not fully understood. In rodent models, nicotine reduces weight gain, reduces food consumption, and alters energy expenditure, but these effects vary with duration and route of nicotine administration. Nicotine, acting through nicotinic acetylcholine receptors (nAChRs), increases the firing rate of both orexigenic agouti-related peptide and anorexigenic proopiomelanocortin neurons in the arcuate nucleus of the hypothalamus (ARC). Manipulation of nAChR subunit expression within the ARC can block the ability of nicotine and the nicotinic agonist cytisine from decreasing food intake; however, it is unknown exactly how this reduces food intake. This review summarizes the clinical and preclinical work on nicotine, food intake, and weight gain, then explores the feeding circuitry of the ARC and how it is regulated by nicotine. Finally, we propose a novel hypothesis for how nicotine acts on this hypothalamic circuit to reduce food intake. Implications: This review provides a comprehensive and updated summary of the clinical and preclinical work examining nicotine and food intake, as well as a summary of recent work examining feeding circuits of the hypothalamus. Synthesis of these two topics has led to new understanding of how nAChR signaling regulates food intake circuits in the hypothalamus.

Cigarette Smoke Exposure to Pig Larynx in an Inhalation Chamber

OBJECTIVES

This study investigated the effects of cigarette smoke exposure on the pig larynx using an inhalation chamber. Specifically, we compared the effects of cigarette smoke exposure from either 3 cigarettes per day (3cd) or 15 cigarettes per day (15cd) for 20 days.

STUDY DESIGN

In vivo prospective design.

METHODS

Female pigs were exposed via an inhalation chamber to cigarette smoke (3R4F research cigarettes) from 3cd (n = 6) or 15cd (n = 6) for 20 days. Outcomes included histopathology of vocal fold and airway tissues; gene expression of interleukins, TNF-α, and VEGF; protein levels of TNF-α and IL-6; and number of coughs recorded in the chamber.

RESULTS

Pigs exposed to cigarette smoke from 15cd exhibited mild vocal fold edema as compared to the 3cd group on histopathological evaluation. There was also minimal inflammation of nasal and tracheal tissue characterized by presence of more granulocytes in the 15cd group compared to the 3cd group. Cough frequency was significantly greater for the 15cd group compared to the 3cd group.

CONCLUSIONS

A custom-designed large animal inhalation chamber successfully challenged pigs repeatedly, to varying levels of cigarette smoke. Future studies will combine such low levels of smoke exposure with other common challenges such as acid reflux to understand the multifactorial causation of laryngeal pathologies.

Immunological and pathological effects of electronic cigarettes

Electronic cigarettes (E-cigarettes) are considered a preferable alternative to conventional cigarettes due to the lack of combustion and the absence of tobacco-specific toxicants. E-cigarettes have rapidly gained in popularity in recent years amongst both existing smokers and previous non-smokers. However, a growing literature demonstrates that E-cigarettes are not as safe as generally believed. Here, we discuss the immunological, and other, deleterious effects of E-cigarettes on a variety of cell types and host defence mechanisms in humans and in murine models. We review not only the effects of complete E-cigarette liquids, but also each of the main components-nicotine, humectants and flavourings. This MiniReview thus highlights the possible role of E-cigarettes in the pathogenesis of disease and raises awareness of the potential harm that E-cigarettes may cause.

Prior cigarette smoke exposure does not affect acute post-stroke outcomes in mice

Chronic obstructive pulmonary disease (COPD) is currently the third leading cause of death globally and is characterized by airflow limitation that is progressive and not fully reversible. Cigarette smoking is the major cause of COPD. Fifty percent of deaths in the COPD population are due to a cardiovascular event and it is now recognised that COPD is a risk factor for stroke. Whether COPD increases stroke severity has not been explored. The aim of this study was to investigate whether functional and histological endpoints of stroke outcomes in mice after transient middle cerebral artery occlusion (tMCAo) were more severe in mice exposed to cigarette smoke (CS). 7-week-old male C57BL/6 mice were exposed to room air or CS generated from 9 cigarettes/day, 5 days/week for 2, 8 and 12 weeks. Following air or CS exposure, mice underwent tMCAO surgery with an ischaemic period of 30-40 min or sham surgery. Mice were euthanised 24 h following the induction of ischaemia and bronchoalveolar lavage fluid (BALF), lungs and brains collected. Mice exposed to CS for 2 weeks and subjected to a stroke had similar BALF macrophages to air-exposed and stroke mice. However, CS plus stroke mice had significantly more BALF total cells, neutrophils and lymphocytes than air plus stroke mice. Mice exposed to CS for 8 and 12 weeks had significantly greater BALF total cells, macrophages, neutrophils and lymphocytes than air-exposed mice, but stroke did not affect CS-induced BALF cellularity. Prior CS exposure did not worsen stroke-induced neurological deficit scores, reduced foregrip strength, infarct and oedema volumes. Collectively, we found that although CS exposure caused significant BALF inflammation, it did not worsen acute post-stroke outcomes in mice. This data suggests that while patients with COPD are at increased risk of stroke, it may not translate to COPD patients having more severe stroke outcomes.

Fibroblast Growth Factor 21 and Browning of White Adipose Tissue

Interest has been focused on differentiating anatomical, molecular, and physiological characteristics of the types of mammalian adipose tissues. White adipose tissue (WAT) and brown adipose tissue (BAT) are the two main forms of adipose tissue in humans. WAT functions as an endocrine organ and serves as a reservoir of energy in the form of triglycerides. The hormones released by WAT are called adipokines. BAT consists of a group of specialized cells with abundant uncoupling protein 1 (UCP1) in the inner mitochondrial membrane and also fulfills endocrine functions. Following the identification of functional (BAT) in human adults, there has been a great deal of interest in finding out how it is induced, its localization, and the mechanisms by which it regulates thermogenesis. Fibroblast growth factor 21 (FGF21) is a key regulator of the differentiation to brown adipocytes. The main mechanisms occur through enhancing UCP1 expression. In addition, following exposure to cold or exercise, FGF21 induces upregulation of local peroxisome proliferator-activated receptor gamma co-activator (PGC)-1-alfa and thus promotes thermogenesis in adipose tissue and skeletal muscle. FGF21 integrates several pathways allowing the regulation of human energy balance, glucose levels, and lipid metabolism. Such mechanisms and their clinical relevance are summarized in this review.

Analysis of the Association between Eating Behaviors and Weight Loss after Laparoscopic Sleeve Gastrectomy

SETTING

In a private medical center, 300 patients who underwent a laparoscopic sleeve gastrectomy (LSG) were classified into 4 groups according to their eating behaviors (EB) preoperatively. During a 3-year postoperative follow-up, dietary changes in relation to weight loss were studied.

OBJECTIVES

To explore the influence of abnormal EB on the outcome of sleeve gastrectomy.

BACKGROUND

Patients with morbid obesity often suffer from abnormal EB. After LSG, the outcome depends largely on improvement of the feeding behaviors acquired.

METHODS

This prospective study includes 300 patients who underwent LSG from 2013 to 2014, divided into the following 4 groups: binge eaters, snack eaters, sweet eaters, and volume eaters.

RESULTS

The average age was 41.65 years, the ratio of male to females was 1 to 2. The average baseline body mass index (BMI) was 42.02. After 3 years, no significant change was found in the number of binge eaters (p = 0.396), but there was an 8.9% increase in snack eaters (p < 0.001), a 12.9% increase in sweet eaters (p < 0.001), and 17.2% increase in healthy eating habits (p < 0.001). Sixty-five (24.8%) patients did not experience changes in their eating patterns. However, after surgery, 24.6% of the patients continued with the same EB and 125 (49.5%) patients changed from one EB to another unhealthy EB. Weight loss, measure as ΔBMI, was similar in each group after 3 years, with a mean BMI of 29.8. When eating habits were related to different features such as gender, sports practice, type of work, smoking, marital status, comorbidities, no influence on the operative results were found.

CONCLUSION

LSG promotes the reduction of overeaters; however, it promotes a switch between other unhealthy EB. The significant increase in snack eaters and sweet eaters is outstanding, although it did not affect weight loss in the midterm follow-up. Worsening of eating habits after LSG is a common fact.

Smoking cessation, weight gain, and risk of stroke among postmenopausal women

The relationship between smoking cessation, concurrent weight gain, and stroke events is not yet understood. Thus, we examined the association between smoking cessation and subsequent stroke risk and whether the association was modified by concurrent weight gain. In 2017, we analyzed data from 109,498 postmenopausal US women enrolled in the Women's Health Initiative from 1993 to 1998. Women with a history of cancer or cardiovascular disease events were excluded. The median length of follow-up time was 14.01 years. Variables of primary focus were smoking cessation, weight change, and clinically confirmed incident cases of hemorrhagic and ischemic stroke. Hazard ratios were estimated for stroke incidences (all, ischemic, and hemorrhagic) associated with smoking cessation using Cox regression. The exposure-outcome relationship of smoking cessation and risk of stroke was evaluated for effect modification by weight change. Recent quitters between baseline and year 3 had a significantly lower risk for all stroke and ischemic stroke, but not hemorrhagic stroke, when compared to the reference group of continuing smokers. In the multivariable-adjusted model for ischemic stroke, the hazard ratio for recent quitters was 0.66 (95% CI: 0.46, 0.95). In the model for hemorrhagic stroke, the hazard ratio for recent quitters was 0.76 (95% CI: 0.36, 1.61). The association between recent quitting and stroke risk was not significantly modified by weight change. Smoking cessation was associated with a significant reduction in stroke risk. The benefit of smoking cessation on the risk of stroke was not attenuated by concurrent weight gain.

Pharmacological Effects and Regulatory Mechanisms of Tobacco Smoking Effects on Food Intake and Weight Control

Beyond promoting smoking initiation and preventing smokers from quitting, nicotine can reduce food intake and body weight and thus is viewed as desirable by some smokers, especially many women. During the last several decades, the molecular mechanisms underlying the inverse correlation between smoking and body weight have been investigated extensively in both animals and humans. Nicotine's weight effects appear to result especially from the drug's stimulation of α3β4 nicotine acetylcholine receptors (nAChRs), which are located on pro-opiomelanocortin (POMC) neurons in the arcuate nucleus (ARC), leading to activation of the melanocortin circuit, which is associated with body weight. Further, α7- and α4β2-containing nAChRs have been implicated in weight control by nicotine. This review summarizes current understanding of the regulatory effects of nicotine on food intake and body weight according to the findings from pharmacological, molecular genetic, electrophysiological, and feeding studies on these appetite-regulating molecules, such as α3β4, α7, and α4β2 nAChRs; neuropeptide Y (NPY); POMC; melanocortin 4 receptor (MC4R); agouti-related peptide (AgRP); leptin, ghrelin, and protein YY (PYY).

Protocols to Evaluate Cigarette Smoke-Induced Lung Inflammation and Pathology in Mice

Cigarette smoking is a major cause of chronic obstructive pulmonary disease (COPD). Inhalation of cigarette smoke causes inflammation of the airways, airway wall remodelling, mucus hypersecretion and progressive airflow limitation. Much of the disease burden and health care utilisation in COPD is associated with the management of its comorbidities and infectious (viral and bacterial) exacerbations (AECOPD). Comorbidities, in particular skeletal muscle wasting, cardiovascular disease and lung cancer markedly impact on disease morbidity, progression and mortality. The mechanisms and mediators underlying COPD and its comorbidities are poorly understood and current COPD therapy is relatively ineffective. Many researchers have used animal modelling systems to explore the mechanisms underlying COPD, AECOPD and comorbidities of COPD with the goal of identifying novel therapeutic targets. Here we describe a mouse model that we have developed to define the cellular, molecular and pathological consequences of cigarette smoke exposure and the development of comorbidities of COPD.

Access to nicotine in drinking water reduces weight gain without changing caloric intake on high fat diet in male C57BL/6J mice

Nicotine and tobacco use is associated with lower body weight, and many smokers report concerns about weight. In animal studies, nicotine reduces weight gain, reduces food consumption, and alters energy expenditure, but these effects vary with duration and route of nicotine administration. Previous studies have used standardized nicotine doses, however, in this study, male and female mice had free access to nicotine drinking water for 30 days while fed either a high fat diet (HFD) or chow, allowing animals to titrate their nicotine intake. In male mice, HFD increased body weight and caloric intake. Nicotine attenuated this effect and decreased weight gain per calorie consumed without affecting overall caloric intake or acute locomotion, suggesting metabolic changes. Nicotine did not decrease weight in chow-fed animals. In contrast, the same paradigm did not result in significant differences in weight gain in female animals, but did alter corticosterone levels and locomotion, indicating sex differences in the response to HFD and nicotine. We measured levels of mRNAs encoding nicotinic acetylcholine receptor subunits, uncoupling proteins (UCP) 1-3, and neuropeptides involved in energy balance in adipose tissues and the arcuate nucleus of the hypothalamus (ARC). HFD and nicotine regulated UCP levels in adipose tissues and ARC from female, but not male, mice. Regulation of agouti-related peptide, neuropeptide-Y, melanin-concentrating hormone, and cocaine- and amphetamine-regulated transcript in ARC varied with diet and nicotine in a sex-dependent manner. These data demonstrate that chronic consumption of nicotine moderates the effect of HFD in male mice by changing metabolism rather than food intake, and identify a differential effect on female mice.

A Study of the Feasibility of FDG-PET/CT to Systematically Detect and Quantify Differential Metabolic Effects of Chronic Tobacco Use in Organs of the Whole Body-A Prospective Pilot Study

RATIONALE AND OBJECTIVES

The aim of this study was to assess the feasibility of ¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography/computed tomography (PET/CT) to systematically detect and quantify differential effects of chronic tobacco use in organs of the whole body.

MATERIALS AND METHODS

Twenty healthy male subjects (10 nonsmokers and 10 chronic heavy smokers) were enrolled. Subjects underwent whole-body FDG-PET/CT, diagnostic unenhanced chest CT, mini-mental state examination, urine testing for oxidative stress, and serum testing. The organs of interest (thyroid, skin, skeletal muscle, aorta, heart, lung, adipose tissue, liver, spleen, brain, lumbar spinal bone marrow, and testis) were analyzed on FDG-PET/CT images to determine their metabolic activities using standardized uptake value (SUV) or metabolic volumetric product (MVP). Measurements were compared between subject groups using two-sample t tests or Wilcoxon rank-sum tests as determined by tests for normality. Correlational analyses were also performed.

RESULTS

FDG-PET/CT revealed significantly decreased metabolic activity of lumbar spinal bone marrow (MVPmean: 29.8 ± 9.7 cc vs 40.8 ± 11.6 cc, P = 0.03) and liver (SUVmean: 1.8 ± 0.2 vs 2.0 ± 0.2, P = 0.049) and increased metabolic activity of visceral adipose tissue (SUVmean: 0.35 ± 0.10 vs 0.26 ± 0.06, P = 0.02) in chronic smokers compared to nonsmokers. Normalized visceral adipose tissue volume was also significantly decreased (P = 0.04) in chronic smokers. There were no statistically significant differences in the metabolic activity of other assessed organs.

CONCLUSIONS

Subclinical organ effects of chronic tobacco use are detectable and quantifiable on FDG-PET/CT. FDG-PET/CT may, therefore, play a major role in the study of systemic toxic effects of tobacco use in organs of the whole body for clinical or research purposes.

Interaction between Physical Activity and Smoking on Lung, Muscle, and Bone in Mice

Physical inactivity is an important contributor to skeletal muscle weakness, osteoporosis, and weight loss in chronic obstructive pulmonary disease. However, the effects of physical inactivity, in interaction with smoking, on lung, muscle, and bone are poorly understood. To address this issue, male mice were randomly assigned to an active (daily running), moderately inactive (space restriction), or extremely inactive group (space restriction followed by hindlimb suspension to mimic bed rest) during 24 weeks and simultaneously exposed to either cigarette smoke or room air. The effects of different physical activity levels and smoking status and their respective interaction were examined on lung function, body composition, in vitro limb muscle function, and bone parameters. Smoking caused emphysema, reduced food intake with subsequent loss of body weight, and fat, lean, and muscle mass, but increased trabecular bone volume. Smoking induced muscle fiber atrophy, which did not result in force impairment. Moderate inactivity only affected lung volumes and compliance, whereas extreme inactivity increased lung inflammation, lowered body and fat mass, induced fiber atrophy with soleus muscle dysfunction, and reduced exercise capacity and all bone parameters. When combined with smoking, extreme inactivity also aggravated lung inflammation and emphysema, and accelerated body and muscle weight loss. This study shows that extreme inactivity, especially when imposed by absolute rest, accelerates lung damage and inflammation. When combined with smoking, extreme inactivity is deleterious for muscle bulk, bone, and lungs. These data highlight that the consequences of physical inactivity during the course of chronic obstructive pulmonary disease should not be neglected.

Genetic Control of Fatty Acid β-Oxidation in Chronic Obstructive Pulmonary Disease

Bioenergetics homeostasis is important for cells to sustain normal functions and defend against injury. The genetic controls of bioenergetics homeostasis, especially lipid metabolism, remain poorly understood in chronic obstructive pulmonary disease (COPD), the third leading cause of death in the world. Additionally, the biological function of most of the susceptibility genes identified from genome-wide association studies (GWASs) in COPD remains unclear. Here, we aimed to address (1) how fatty acid oxidation (FAO), specifically β-oxidation, a key lipid metabolism pathway that provides energy to cells, contributes to cigarette smoke (CS)-induced COPD; and (2) whether-and if so, how-FAM13A (family with sequence similarity 13 member A), a well-replicated COPD GWAS gene, modulates the FAO pathway. We demonstrated that CS induced expression of carnitine palmitoyltransferase 1A (CPT1A), a key mitochondrial enzyme for the FAO pathway, thereby enhancing FAO. Pharmacological inhibition of FAO by etomoxir blunted CS-induced reactive oxygen species accumulation and cell death in lung epithelial cells. FAM13A promoted FAO, possibly by interacting with and activating sirutin 1, and increasing expression of CPT1A. Furthermore, CS-induced cell death was reduced in lungs from Fam13a-/- mice. Our results suggest that FAM13A, the COPD GWAS gene, shapes the cellular metabolic response to CS exposure by promoting the FAO pathway, which may contribute to COPD development.

Eating moderates the link between body mass index and perceived social connection

Some studies have demonstrated that heavier people perceive themselves as lacking social connections, whereas others have not. The current study investigated whether eating alters the link between body mass index (BMI) and perceived social connection, providing one explanation for inconsistencies across previous studies. Participants were instructed to refrain from eating or drinking anything except water after 9 p.m. the prior night. Upon arrival at the lab, participants were assigned to the food (n = 63) or no food (n = 110) condition. They also provided a saliva sample that was assayed for ghrelin (an appetite-relevant hormone), and completed a series of questionnaires about their relationships. Participants with a higher BMI felt more socially disconnected than people with a lower BMI, but only among those who had not recently eaten. BMI and perceived social disconnection were unrelated among people who had recently eaten. These results were consistent across multiple measures of perceived social disconnection, and also across the experimental manipulation and continuously measured ghrelin.

Browning of white adipose tissue: lessons from experimental models

Beige or brite (brown-in-white) adipocytes are present in white adipose tissue (WAT) and have a white fat-like phenotype that when stimulated acquires a brown fat-like phenotype, leading to increased thermogenesis. This phenomenon is known as browning and is more likely to occur in subcutaneous fat depots. Browning involves the expression of many transcription factors, such as PR domain containing 16 (PRDM16) and peroxisome proliferator-activated receptor (PPAR)-γ, and of uncoupling protein (UCP)-1, which is the hallmark of thermogenesis. Recent papers pointed that browning can occur in the WAT of humans, with beneficial metabolic effects. This fact indicates that these cells can be targeted to treat a range of diseases, with both pharmacological and nutritional activators. Pharmacological approaches to induce browning include the use of PPAR-α agonist, adrenergic receptor stimulation, thyroid hormone administration, irisin and FGF21 induction. Most of them act through the induction of PPAR-γ coactivator (PGC) 1-α and the consequent mitochondrial biogenesis and UCP1 induction. About the nutritional inducers, several compounds have been described with multiple mechanisms of action. Some of these activators include specific amino acids restriction, capsaicin, bile acids, Resveratrol, and retinoic acid. Besides that, some classes of lipids, as well as many plant extracts, have also been implicated in the browning of WAT. In conclusion, the discovery of browning in human WAT opens the possibility to target the adipose tissue to fight a range of diseases. Studies have arisen showing promising results and bringing new opportunities in thermogenesis and obesity control.

The Effect of Medical Marijuana Laws on Body Weight

This study is the first to examine the effects of medical marijuana laws (MMLs) on body weight, physical wellness, and exercise. Using data from the 1990 to 2012 Behavioral Risk Factor Surveillance System and a difference-in-difference approach, we find that the enforcement of MMLs is associated with a 2% to 6% decline in the probability of obesity. We find some evidence of age-specific heterogeneity in mechanisms. For older individuals, MML-induced increases in physical mobility may be a relatively important channel, while for younger individuals, a reduction in consumption of alcohol, a substitute for marijuana, appears more important. These findings are consistent with the hypothesis that MMLs may be more likely to induce marijuana use for health-related reasons among older individuals, and cause substitution toward lower-calorie recreational 'highs' among younger individuals. Our estimates suggest that MMLs induce a $58 to $115 per-person annual reduction in obesity-related medical costs. Copyright © 2015 John Wiley & Sons, Ltd.

Leptin and calorie intake among different nicotine dependent groups

BACKGROUND

Exposure to nicotine via tobacco smoking may influence leptin release and decrease food intake among smokers. However, the effect of nicotine exposure on leptin and food intake among different nicotine dependent groups is unclear.

OBJECTIVE

We aimed to measure leptin and calorie intake among different nicotine dependent groups.

DESIGN

Cross-sectional study.

SETTING

Research department in school of medical sciences.

PATIENTS AND METHODS

Subjects were selected by purposive (non-probability) sampling and categorized as having low, moderate and high nicotine dependency based on the Fagerstrom Test for Nicotine Dependence (FTND) score. Diet was recorded by interview. Anthropometry, blood pressure, body composition, lipid profile, and physical activity level were measured accordingly. Fasting serum leptin was measured using a commercial ELISA kit.

MAIN OUTCOME MEASURE(S)

Nicotine dependency, 24-hour diet, clinical anthropometric and clinical measurements.

RESULTS

In 107 Malay male smokers leptin concentration was inversely correlated with nicotine dependence. However, body weight, smoking period, blood pressure, body composition, lipid profile and physical activity level were not significantly different among low, moderately and highly dependent smoking groups. Leptin concentration and total calorie intake were also not significantly different among these groups.

CONCLUSION

Leptin concentration was inversely correlated with nicotine dependence, but leptin concentration and total calorie intake status were not significantly different among our different nicotine dependency subjects.

LIMITATIONS

Purposive sampling for subject recruitment and inaccurate information in the self-administered questionnaire.

Blood Levels of Monoamine Precursors and Smoking in Patients with Schizophrenia

Smoking is highly prevalent in patients with schizophrenia and exerts a negative impact on cardiovascular mortality in these patients. Smoking has complex interactions with monoamine metabolism through the ability of cigarette smoke to suppress Type 1 T helper cell (Th1) type immunity, the immunophenotype that is implicated in phenylalanine hydroxylase (PAH) dysfunction and tryptophan (Trp) breakdown to kynurenine (Kyn) via indoleamine 2,3-dioxygenase. Nicotine also induces tyrosine hydroxylase (TH) gene expression, leading to increased synthesis of catecholamines. Furthermore, there is evidence for PAH dysfunction in schizophrenia. This study aimed to compare the plasma levels of selected monoamine precursors and their metabolites in smokers vs. non-smokers in a large sample of patients with schizophrenia. We measured plasma phenylalanine (Phe), tyrosine (Tyr), Trp, and Kyn levels using high-performance liquid chromatography and calculated Phe:Tyr and Kyn:Trp ratios in 920 patients with schizophrenia. Analysis of variance and linear regression analyses were used to compare these endpoints between three groups of patients with schizophrenia: (1) current smokers, (2) past smokers, and (3) non-smokers. There were significant differences among the three groups with regards to Tyr levels [F_(2,789) = 3.77, p = 0.02], with current smokers having lower Tyr levels when compared with non-smokers (p = 0.02). Kyn levels and Kyn:Trp ratio were different among the three groups [F_(2,738) = 3.17, p = 0.04, F_(2,738) = 3.61, p = 0.03] with current smokers having lower Kyn levels (p = 0.04) and higher Kyn:Trp ratio (p = 0.02) when compared with past smokers. These findings need to be replicated with protocols that include healthy controls to further elucidate the neurobiological underpinnings of altered Tyr and Kyn levels in smokers. Results do suggest potential molecular links between schizophrenia and smoking that may represent biomarkers and treatment targets for reducing an important modifiable cause of general morbidity and mortality in patients with schizophrenia.

Effects of drugs of abuse on the central neuropeptide Y system

Neuropeptide Y (NPY), which is widely expressed in the central nervous system is involved in several neuropathologies including addiction. Here we comprehensively and systematically review alterations on the central NPY system induced by several drugs. We report on the effects of psychostimulants [cocaine, amphetamine, methamphetamine, 3,4-methylenedioxymethamphetamine (MDMA) and nicotine], ethanol, and opioids on NPY protein levels and expression of different NPY receptors. Overall, expression and function of NPY and its receptors are changed under conditions of drug exposure, thus affecting several physiologic behaviors, such as feeding, stress and anxiety. Drugs of abuse differentially affect the components of the NPY system. For example methamphetamine and nicotine lead to a consistent increase in NPY mRNA and protein levels in different brain sites whereas ethanol and opioids decrease NPY mRNA and protein expression. Drug-induced alterations on the different NPY receptors show more complex regulation pattern. Manipulation of the NPY system can have opposing effects on reinforcing and addictive properties of drugs of abuse. NPY can produce pro-addictive effects (nicotine and heroin), but can also exert inhibitory effects on addictive behavior (AMPH, ethanol). Furthermore, NPY can act as a neuroprotective agent in chronically methamphetamine and MDMA-treated rodents. In conclusion, manipulation of the NPY system seems to be a potential target to counteract neural alterations, addiction-related behaviors and cognitive deficits induced by these drugs.

Murine models of cardiovascular comorbidity in chronic obstructive pulmonary disease

Patients with chronic obstructive pulmonary disease (COPD) have an increased risk for cardiovascular disease (CVD). Currently, COPD patients with atherosclerosis (i.e., the most important underlying cause of CVD) receive COPD therapy complemented with standard CVD therapy. This may, however, not be the most optimal treatment. To investigate the link between COPD and atherosclerosis and to develop specific therapeutic strategies for COPD patients with atherosclerosis, a substantial number of preclinical studies using murine models have been performed. In this review, we summarize the currently used murine models of COPD and atherosclerosis, both individually and combined, and discuss the relevance of these models for studying the pathogenesis and development of new treatments for COPD patients with atherosclerosis. Murine and clinical studies have provided complementary information showing a prominent role for systemic inflammation and oxidative stress in the link between COPD and atherosclerosis. These and other studies showed that murine models for COPD and atherosclerosis are useful tools and can provide important insights relevant to understanding the link between COPD and CVD. More importantly, murine studies provide good platforms for studying the potential of promising (new) therapeutic strategies for COPD patients with CVD.

Apocynin and ebselen reduce influenza A virus-induced lung inflammation in cigarette smoke-exposed mice

Influenza A virus (IAV) infections are a common cause of acute exacerbations of chronic obstructive pulmonary disease (AECOPD). Oxidative stress is increased in COPD, IAV-induced lung inflammation and AECOPD. Therefore, we investigated whether targeting oxidative stress with the Nox2 oxidase inhibitors and ROS scavengers, apocynin and ebselen could ameliorate lung inflammation in a mouse model of AECOPD. Male BALB/c mice were exposed to cigarette smoke (CS) generated from 9 cigarettes per day for 4 days. On day 5, mice were infected with 1 × 10(4.5) PFUs of the IAV Mem71 (H3N1). BALF inflammation, viral titers, superoxide production and whole lung cytokine, chemokine and protease mRNA expression were assessed 3 and 7 days post infection. IAV infection resulted in a greater increase in BALF inflammation in mice that had been exposed to CS compared to non-smoking mice. This increase in BALF inflammation in CS-exposed mice caused by IAV infection was associated with elevated gene expression of pro-inflammatory cytokines, chemokines and proteases, compared to CS alone mice. Apocynin and ebselen significantly reduced the exacerbated BALF inflammation and pro-inflammatory cytokine, chemokine and protease expression caused by IAV infection in CS mice. Targeting oxidative stress using apocynin and ebselen reduces IAV-induced lung inflammation in CS-exposed mice and may be therapeutically exploited to alleviate AECOPD.