Circadian rhythm of airways caliber and its autonomic modulation

An update on long-acting muscarinic agents for asthma therapy

INTRODUCTION

The manifestations of asthma are influenced by the dysfunction of the autonomic nervous system, which results in elevated vagal tone within the airways. Acetylcholine (ACh) plays a pivotal role in the pathophysiology of asthma through its interaction with muscarinic acetylcholine receptors (mAChRs). Consequently, using mAChR antagonists to counteract the actions of ACh is scientifically sound.

AREAS COVERED

This narrative review methodically examines the latest information on the mechanisms and evidence supporting the use of long-acting muscarinic antagonists (LAMAs) in asthma.

EXPERT OPINION

Adding a LAMA to existing asthma treatments involving an ICS and a LABA, within a single inhaler triple therapy (SITT), improves lung function regulating airflow limitation, reduces exacerbations, and eosinophilic inflammation and offers a more comprehensive approach to managing inflammation and tissue remodeling, which are linked to ACh. Additionally, it disrupts the vicious cycle of ACh release that contributes to neuronal plasticity and dysfunction of small airways. Identifying treatable traits is key to using SITT in a customized way that aligns with patients' needs. The 5T (Triple Therapy Targeting Treatable Traits) approach proposes the utilization of SITT for all asthma cases, not solely severe ones, and involves using LAMAs in ICS/LABA combinations earlier than current guidelines recommend.

Influence of Chronotype and Theobromine on the 24-h Variation in Peak Expiratory Flow Rate in Healthy Adults

The influence of morningness-eveningness preference and dietary components on the circadian variation in peak expiratory flow (PEF), an established criterion for pulmonary function, is not fully understood. This study aimed to investigate (a) how the chronotype influences the 24-h variation in PEF and (b) whether the bronchodilator theobromine affects this variation differently in different chronotypes. Ninety-seven healthy non-smoking females (54 early chronotypes, ET; 43 late chronotypes, LT; 18-35 years) recorded their PEF over 24 hours at 4-h intervals (08:00/12:00/16:00/20:00/24:00/04:00/08:00 h). In a subgroup (26 ET, 18 LT), the effect of 48 mg theobromine (40 g dark chocolate) on PEF was compared on three consecutive 24-h days with no administration, morning administration and evening administration of theobromine. Repeated measures ANOVA tested for 24-h variation in PEF. Both chronotypes displayed significant 24-h variation in PEF (P < 0.0001) explaining 36% (ET) and 31% (LT) of variance of PEF. The time of maximum PEF was three hours earlier in ET than in LT (P = 0.003) and correlated negatively with chronotype scores (P = 0.001) and positively with bedtimes (awakening time: P < 0.001; sleep-onset time: P = 0.012). The chronotypes showed no differences in 24-h mean and amplitude % mean for PEF. Administration of theobromine strengthened the morning increase (P = 0.004) and weakened the evening decrease (P = 0.063) of PEF in LT, but had no effect in ET. The differences found between chronotypes in timing of maximum PEF and responsiveness to the bronchodilator theobromine might have clinical relevance. Therapy for respiratory diseases should consider the chronotype of patients for drug timing and dosage.

Is it preferable to administer a bronchodilator once- or twice-daily when treating COPD?

Nocturnal and early morning symptoms are common and uncomfortable in many patients with COPD, and are likely to affect their long-term outcomes. However, it is still debated whether it is better to give long-acting bronchodilators once- or twice-daily to symptomatic COPD patients. The functional link between circadian rhythms of autonomic tone and airway calibre explains why the timing of administration of bronchodilators in chronic airway diseases can induce different effects when taken at different biological (circadian) times. However, the timing also depends on the pharmacological characteristics of the bronchodilator to be used. Because the profile of bronchodilation produced by once-daily vs. twice-daily long-acting bronchodilators differs throughout 24 h, selecting long-acting bronchodilators may be customized to specific patient preferences based on the need for further bronchodilation in the evening. This is especially helpful for people who experience respiratory symptoms at night or early morning. Compared to placebo, evening bronchodilator administration is consistently linked with persistent overnight improvements in dynamic respiratory mechanics and inspiratory neural drive. The current evidence indicates that nocturnal and early morning symptoms control is best handled by a LAMA taken in the evening. In contrast, it seems preferable to use a LABA for daytime symptoms. Therefore, it can be speculated that combining a LAMA with a LABA can improve bronchodilation and control symptoms better. Both LAMA and LABA must be rapid in their onset of action. Aclidinium/formoterol, a twice-daily combination, is the most studies of the available LAMA/LABA combinations in terms of impact on daytime and nocturnal symptoms.

Association of the Time to First Cigarette and the Prevalence of Chronic Respiratory Diseases in Chinese Elderly Population

BACKGROUND

Increasing number of studies have suggested the time to first cigarette after waking (TTFC) have significant positive effect on respiratory diseases. However, few of them focused on the Chinese population. This study aims to estimate the impact of TTFC on the prevalence of chronic respiratory diseases (CRD) in Chinese elderly and explore the association in different sub-populations.

METHODS

Cross-sectional data of demographic characteristics, living environment, smoking-related variables, and CRD were drawn from the Chinese Longitudinal Healthy Longevity Survey in 2018. Multivariate stepwise logistic regression analyses were conducted to examine the association of the TTFC with the prevalence of CRD.

RESULTS

This study includes 13,208 subjects aged 52 years and older, with a mean age of 85.3 years. Of them, 3,779 participants were ex- or current smokers (44.9% had the TTFC ≤30 minutes, 55.1% >30 minutes) and 1,492 had suffered from CRD. Compared with non-smokers, participants with TTFC ≤30 minutes seemed to have higher prevalence of CRD (OR 1.97; 95% CI, 1.65-2.35) than those with TTFC >30 minutes (OR 1.70; 95% CI, 1.44-2.00), although the difference was statistically insignificant (Pinteraction = 0.12). Compared with TTFC >30 minutes, TTFC ≤30 minutes could drive a higher prevalence of CRD among female participants, those aged 90 years and older, urban residents, and ex-smokers (Pinteraction < 0.05).

CONCLUSION

Shorter TTFC relates to higher prevalences of CRD in Chinese older females, those aged 90 years and older, urban residents, and ex-smokers. Delaying TTFC might partially reduce its detrimental impact on respiratory disease in these specific subpopulations.

Association analysis between chronic obstructive pulmonary disease and polymorphisms in circadian genes

Background

Circadian genes have been suggested to play an important role in lung pathology. However, it remains unknown whether polymorphisms of these genes are associated with chronic obstructive pulmonary disease (COPD). Here, we aimed to investigate the association of circadian genes polymorphisms with COPD in a case-control study of 477 COPD patient and 323 control Han Chinese persons.

Methods

Genotyping assays were carried out for nine single nucleotide polymorphisms (SNPs) from five circadian genes (PER3, CLOCK, RORB, BMAL1 and CRY2) that were previously identified in lung pathology. Age, sex, BMI and smoking status and comorbidities were recorded for all subjects.

Results

No significant association was found in all SNP sites in overall subjects and no significant difference was found in age, sex, smoking status stratification analysis.

Discussion

The findings of this investigation indicated the effect of circadian genes polymorphisms on COPD susceptibility may only be small and possibly dependent on the subject factors, such as age and sex.