A review of monoamine oxidase (MAO) inhibitors in tobacco or tobacco smoke

Smoking, coffee intake, and Parkinson's disease: Potential protective mechanisms and components

Parkinson's disease (PD) is a common progressive neurodegenerative disease characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). Environmental and lifestyle factors, such as smoking and coffee drinking, have been associated with a decreased risk for PD. However, the biological mechanisms underlying protective effects on PD are still not fully understood. It has been suggested that non-nicotine components in cigarette smoke and non-caffeine components in coffee may contribute to this protective effect. The aim of this review was to explore candidate molecules and mechanisms behind the effects of smoking and coffee drinking on PD by integrating findings from previous studies. By cross-referencing an index of tobacco constituents and a list of coffee constituents with existing literature on natural compounds and their structural analogs that show inhibitory activities against monoamine oxidase B, catechol O-methyltransferase, and α-synuclein fibrillation, we have identified tobacco and coffee components that inhibit these targets. Furthermore, tobacco and coffee components potentially play roles in suppressing neuroinflammation, activating the Nrf2 pathway as natural activators, and altering the gut microbiome. This review suggests that the phenolic compounds from tobacco and coffee investigated may contribute to the low incidence of PD in smokers and coffee drinkers, showing moderate to strong potential as therapeutic interventions. The current review suggests that multifunctional molecules found in coffee and cigarette smoke may have potential neuroprotective effects, but none of the data indicates that multifunctionality is required for these effects. This review will deepen our understanding of how smoking and coffee drinking are linked to a reduced risk of PD and will also be important in elucidating the mechanisms underlying the protective effects of smoking and coffee drinking on PD.

The effect of mixed tobacco monoamine oxidase inhibitors in animal models relevant to tobacco dependence

RATIONALE

Tobacco monoamine oxidase (MAO) inhibitors have long been suspected of influencing tobacco dependence, but direct evidence of their effects has been difficult to obtain. Recently we have identified two new groups of monoamine oxidase inhibitors, hydroquinones and polyunsaturated fatty acids (linoleic and linolenic acid), abundant in tobacco smoke.

OBJECTIVES

To test, in relevant animal models, whether the combined effect of these inhibitors is sufficient to affect addictive responses to nicotine.

METHODS

Here we report the first tests of the effects of mixed tobacco MAO inhibitors in three animal behavioural tests relevant to nicotine addiction, conditioned place preference, locomotor sensitisation and nicotine self-administration. Inhibitors used were the aforementioned linoleic and linolenic acid, and catechol, 4-ethylcatechol, 4-methyl catechol and hydroquinone, together with the already known inhibitors harman and norharman. They were administered together in the ratios found in tobacco smoke.

RESULTS

In conditioned place preference and in self-administration tests the addition of these tobacco MAO inhibitors significantly increased responding to nicotine and motivation to self-administer nicotine, supporting the hypothesis that inhibition of MAO enzymes in the brain enhances addictive responses such as that for nicotine. The combined MAO inhibitors without nicotine did not cause increased locomotor activity and did not induce a place conditioned response.

CONCLUSIONS

Our results show that the combined effect of three groups of major MAO inhibitors present in tobacco smoke can enhance the addictive responses to nicotine in rats. There is no evidence from this study that these MAO inhibitors are addictive in themselves.

Contribution of Nutritional, Lifestyle, and Metabolic Risk Factors to Parkinson's Disease

BACKGROUND

Modifiable risk factors for Parkinson's disease (PD) are poorly known.

OBJECTIVES

The aim is to evaluate independent associations of different nutritional components, physical activity, and sedentary behavior and metabolic factors with the risk of PD.

METHODS

In this population-based prospective cohort study using the data of the United Kingdom Biobank (from 2006-2010), 502,017 men and women who were free from PD (International Classification of Diseases 10th edition; "G20") at baseline were included. We implemented a Cox proportion hazard's model to evaluate the associations of different levels of physical activity, sitting time, sleep habits, diet quality, alcohol and coffee consumption, smoking, and body mass index with PD risk, adjusting for several confounding variables.

RESULTS

During a median follow-up of 12.8 years, lifestyle factors including vigorous physical activity (hazard ration [HR] = 0.84; 95% confidence interval [CI], 0.75-0.94), low-to-moderate sitting time (HR = 0.89; 95% CI, 0.81-0.97), and high sleep quality (HR = 0.89; 95% CI, 0.80-0.99) were associated with a reduced risk of PD. Small amounts of coffee (HR = 0.88; 95% CI, 0.82-0.95), red meat (HR = 0.86; 95% CI, 0.76-0.97), and current smoking (HR = 0.65; 95% CI, 0.56-0.75) were also associated with a lower risk of PD, whereas alcohol intake (HR = 1.29; 95% CI, 1.06-1.56) with higher PD risk. Secondary analysis, including metabolic risk factors, confirmed these findings and highlighted the potential protective effect of plasma vitamin D and uric acid, but of low-density lipoprotein-cholesterol, triglycerides, and C-reactive protein as well.

CONCLUSIONS

Vigorous physical activity, reduced sitting time, good sleep quality together with small coffee intake and vitamin D supplementation are potentially neuroprotective lifestyle interventions for the prevention of PD. © 2024 International Parkinson and Movement Disorder Society.

Influence of microorganisms on flavor substances and functional components of sojae semen praeparatum during fermentation: A study integrating comparative metabolomics and high-throughput sequencing

Sojae semen praeparatum (SSP), a fermented product known for its distinctive flavor and medicinal properties, undergoes a complex fermentation process due to the action of various microorganisms. Despite its widespread use, the effect of these microorganisms on the flavor compounds and functional components of SSP remains poorly understood. This study aimed to shed light on this aspect by identifying 20 metabolites as potential key flavor substances in SSP. Moreover, glycine and lysine were identified as crucial flavor substances. Additionally, 24 metabolites were identified as key functional components. The dominant microorganisms involved in the fermentation process were examined, revealing six genera of fungi and 12 genera of bacteria. At the species level, 16 microorganisms were identified as dominant through metagenome sequencing. Spearman correlation analysis demonstrated a strong association between dominant microorganisms and both flavor substances and functional components. Furthermore, the study validated the significance of four core functional microorganisms in improving the flavor and quality of SSP. This comprehensive exploration of functional microorganisms of SSP on key flavor substances/functional components during SSP fermentation. The study findings serve as a valuable reference for enhancing the overall flavor and quality of SSP.

Association between Single Nucleotide Polymorphisms in Monoamine Oxidase and the Severity of Addiction to Betel Quid

Betel quid (BQ) is the fourth most popular psychoactive substance in the world, and BQ use disorder (BUD) is prevalent in Asian countries. Although the mechanisms underlying BUD remain unclear, studies have reported influences from monoamine oxidase inhibitor. We enrolled 50 patients with BUD and assessed their BQ consumption habits, emotional conditions, and the clinical severity of addiction-assessed using the Diagnostic and Statistical Manual of Mental Disorders [Fifth Edition] (DSM-5) criteria, Substance Use Severity Rating Scale, and Yale-Brown Obsessive Compulsive Disorder Rating Scale for BQ. Patients were categorized into the severe group when showing six or more symptoms defined by DSM-5. A genome-wide association study was conducted for single nucleotide polymorphisms in BRCA1, COL9A1, NOTCH1, HSPA13, FAT1, and MAOA by using patients' blood samples. More severe BUD symptoms were associated with younger age of using BQ and poor oral hygiene and with severe craving for and more anxiety toward BQ use. The MAOA rs5953210 polymorphism was significantly associated with severe BUD (odds ratio, 6.43; 95% confidence interval, 5.12-7.74; p < 0.01) and might contribute to BQ-associated cancer risk. Further studies are required to investigate the addictive properties of BQ and the development of novel diagnostic tools and pharmacotherapeutic alternatives to BUD treatment.

Unveiling the Molecular Mechanism of Diosmetin and its Impact on Multifaceted Cellular Signaling Pathways

BACKGROUND

Diosmetin is an O-methylated flavone and the aglycone part of the flavonoid glycosides diosmin that occurs naturally in citrus fruits. Pharmacologically, diosmetin is reported to exhibit anticancer, antimicrobial, antioxidant, oestrogenic, and anti-inflammatory activities.

OBJECTIVE

This comprehensive review was aimed to critically explore diverse pharmacological activities exhibited by diosmetin. Along with that, this review can also identify potential research areas with an elucidation of the multifactorial underlying signaling mechanism of action of diosmetin in different diseases.

METHODS

A comprehensive collection of evidence and insights was obtained from scientific journals and books from physical libraries and electronic platforms like Google Scholar and PubMed. The time frame selected was from year 1992 to July 2023.

RESULTS

The review delves into diosmetin's impact on cellular signaling pathways and its potential in various diseases. Due to its ability to modulate signaling pathways and reduce oxidative stress, it can be suggested as a potential versatile therapeutic agent for mitigating oxidative stressassociated pathogenesis.

CONCLUSION

The amalgamation of the review underscores diosmetin's promising role as a multifaceted therapeutic agent, highlighting its potential for drug development and clinical applications.