Associations of Observational and Genetically Determined Caffeine Intake With Coronary Artery Disease and Diabetes Mellitus

Genome-wide characterization of 54 urinary metabolites reveals molecular impact of kidney function

Dissecting the genetic mechanisms underlying urinary metabolite concentrations can provide molecular insights into kidney function and open possibilities for causal assessment of urinary metabolites with risk factors and disease outcomes. Proton nuclear magnetic resonance metabolomics provides a high-throughput means for urinary metabolite profiling, as widely applied for blood biomarker studies. Here we report a genome-wide association study meta-analysed for 3 European cohorts comprising 8,011 individuals, covering both people with type 1 diabetes and general population settings. We identify 54 associations (p < 9.3 × 10-10) for 19 of 54 studied metabolite concentrations. Out of these, 33 were not reported previously for relevant urinary or blood metabolite traits. Subsequent two-sample Mendelian randomization analysis suggests that estimated glomerular filtration rate causally affects 13 urinary metabolite concentrations whereas urinary ethanolamine, an initial precursor for phosphatidylcholine and phosphatidylethanolamine, was associated with higher eGFR lending support for a potential protective role. Our study provides a catalogue of genetic associations for 53 metabolites, enabling further investigation on how urinary metabolites are linked to human health.

Comparison of caffeine consumption behavior with plasma caffeine levels as exposure measures in drug-target mendelian randomization

Mendelian randomization is an epidemiologic technique that can explore the potential effect of perturbing a pharmacological target. Plasma caffeine levels can be used as a biomarker to measure the pharmacological effects of caffeine. Alternatively, this can be assessed using a behavioral proxy, such as average number of caffeinated drinks consumed per day. Either variable can be used as the exposure in a Mendelian randomization investigation, and to select which genetic variants to use as instrumental variables. Another possibility is to choose variants in gene regions with known biological relevance to caffeine level regulation. These choices affect the causal question that is being addressed by the analysis, and the validity of the analysis assumptions. Further, even when using the same genetic variants, the sign of Mendelian randomization estimates (positive or negative) can change depending on the choice of exposure. Some genetic variants that decrease caffeine metabolism associate with higher levels of plasma caffeine, but lower levels of caffeine consumption, as individuals with these variants require less caffeine consumption for the same physiological effect. We explore Mendelian randomization estimates for the effect of caffeine on body mass index, and discuss implications for variant and exposure choice in drug target Mendelian randomization investigations.

Potential genetic association between coffee/caffeine consumption and erectile dysfunction: a Mendelian randomization study and meta-analysis

Background

Coffee is a widely consumed beverage with potential benefits for various chronic diseases. Its effect on reducing erectile dysfunction (ED) risk is unclear. This Mendelian randomization (MR) study investigates the impact of coffee/caffeine consumption on ED.

Methods

Two sets of coffee consumption-associated genetic variants at the genome-wide significance level were obtained from recent studies of coffee consumption. Taking into account other sources of caffeine, genetic variants associated with caffeine consumption from tea were also obtained. The inverse variance weighted (IVW) method was utilized as the primary analysis. Sensitivity analysis methods and meta-analysis methods were performed to confirm the robustness of the results, while the genetic variants associated with confounders, e.g., diabetes and hypertension, were excluded.

Results

Genetically predicted coffee/caffeine consumption was unlikely to be associated with the risk of ED in the Bovijn datasets, with similar directional associations observed in the FinnGen datasets. The combined odds ratio for ED was 1.011 (95% CI 0.841-1.216, p=0.906) for coffee consumption from the genome-wide meta-analysis, 1.049 (95% CI 0.487-2.260, p=0.903) for coffee consumption from the genome-wide association study, and 1.061 (95% CI 0.682-1.651, p=0.793) for caffeine from tea.

Conclusion

Using genetic data, this study found no association between coffee/caffeine consumption and the risk of ED.

Association of the ABCG2 rs2231142 variant with the Framingham Cardiovascular Disease Risk score in the Taiwanese population

Background

Serum uric acid (SUA) is an important predictor of cardiovascular events and mortality. The ABCG2 rs2231142 variant (TT genotype) is associated with hyperuricemia (HUA), but the relationship between ABCG2 gene polymorphisms and coronary artery disease (CAD) risk is poorly elucidated. We investigated the association between ABCG2 rs2231142 genetic variants and the Framingham Risk Score for Cardiovascular Disease (FRS-CVD) in a Taiwanese population.

Methods

This cross-sectional study enrolled 139,508 Taiwanese participants aged 30-70 years based on data from the Taiwan Biobank (TWB) database that was obtained from questionnaires, laboratory investigations, anthropometry, and Affymetrix TWB genome-wide single-nucleotide polymorphism (SNP) chip data analysis. The association between ABCG2 rs2231142 and FRS-CVD risk was evaluated using logistic regression analysis.

Results

Compared to those with the GG genotype, participants with the ABCG2 rs2231142 TT genotype had a significantly lower systolic blood pressure, smoking rate, body mass index, triglyceride level, waist circumference, waist-hip ratio, and body fat percentage, but had higher high-density lipoprotein cholesterol level. Despite the same FRS-CVD score, participants with TT genotypes had higher SUA. Even with the same SUA, TT carriers had a lower FRS-CVD than GT and GG carriers. Participants with the TT genotype had significantly lower CVD risk, particularly female participants with HUA and BMI <27 (OR: 0.760, 95 % CI: 0.587-0.985; p = 0.0381) group.

Conclusion

The ABCG2 rs2231142 TT genotype is associated with a lower FRS-CVD, particularly in non-obese hyperuricemic female individuals. The complicated interplay among genetic variations, metabolic profile, and CVD risk provides insights for precision health.

Genome-wide association studies of coffee intake in UK/US participants of European ancestry uncover cohort-specific genetic associations

Coffee is one of the most widely consumed beverages. We performed a genome-wide association study (GWAS) of coffee intake in US-based 23andMe participants (N = 130,153) and identified 7 significant loci, with many replicating in three multi-ancestral cohorts. We examined genetic correlations and performed a phenome-wide association study across hundreds of biomarkers, health, and lifestyle traits, then compared our results to the largest available GWAS of coffee intake from the UK Biobank (UKB; N = 334,659). We observed consistent positive genetic correlations with substance use and obesity in both cohorts. Other genetic correlations were discrepant, including positive genetic correlations between coffee intake and psychiatric illnesses, pain, and gastrointestinal traits in 23andMe that were absent or negative in the UKB, and genetic correlations with cognition that were negative in 23andMe but positive in the UKB. Phenome-wide association study using polygenic scores of coffee intake derived from 23andMe or UKB summary statistics also revealed consistent associations with increased odds of obesity- and red blood cell-related traits, but all other associations were cohort-specific. Our study shows that the genetics of coffee intake associate with substance use and obesity across cohorts, but also that GWAS performed in different populations could capture cultural differences in the relationship between behavior and genetics.

Caffeine consumption outcomes on amyotrophic lateral sclerosis disease progression and cognition

Caffeine consumption outcomes on Amyotrophic Lateral Sclerosis (ALS) including progression, survival and cognition remain poorly defined and may depend on its metabolization influenced by genetic variants. 378 ALS patients with a precise evaluation of their regular caffeine consumption were monitored as part of a prospective multicenter study. Demographic, clinical characteristics, functional disability as measured with revised ALS Functional Rating Scale (ALSFRS-R), cognitive deficits measured using Edinburgh Cognitive and Behavioural ALS Screen (ECAS), survival and riluzole treatment were recorded. 282 patients were genotyped for six single nucleotide polymorphisms tagging different genes involved in caffeine intake and/or metabolism: CYP1A1 (rs2472297), CYP1A2 (rs762551), AHR (rs4410790), POR (rs17685), XDH (rs206860) and ADORA2A (rs5751876) genes. Association between caffeine consumption and ALSFRS-R, ALSFRS-R rate, ECAS and survival were statistically analyzed to determine the outcome of regular caffeine consumption on ALS disease progression and cognition. No association was observed between caffeine consumption and survival (p = 0.25), functional disability (ALSFRS-R; p = 0.27) or progression of ALS (p = 0.076). However, a significant association was found with higher caffeine consumption and better cognitive performance on ECAS scores in patients carrying the C/T and T/T genotypes at rs2472297 (p-het = 0.004). Our results support the safety of regular caffeine consumption on ALS disease progression and survival and also show its beneficial impact on cognitive performance in patients carrying the minor allele T of rs2472297, considered as fast metabolizers, that would set the ground for a new pharmacogenetic therapeutic strategy.

The role of coffee and potential mediators in subclinical atherosclerosis: insights from Mendelian randomization study

Background and aims

Coffee contains many bioactive compounds, and its inconsistent association with subclinical atherosclerosis has been reported in observational studies. In this Mendelian randomization study, we investigated whether genetically predicted coffee consumption is associated with subclinical atherosclerosis, as well as the role of potential mediators.

Methods

We first conducted a two-sample Mendelian randomization analysis to examine the causal effect of coffee and its subtypes on subclinical atherosclerosis inferred from coronary artery calcification (CAC). Next, the significant results were validated using another independent dataset. Two-step Mendelian randomization analyses were utilized to evaluate the causal pathway from coffee to subclinical atherosclerosis through potential mediators, including blood pressure, blood lipids, body mass index, and glycated hemoglobin. Mendelian randomization analyses were performed using the multiplicative random effects inverse-variance weighted method as the main approach, followed by a series of complementary methods and sensitivity analyses.

Results

Coffee, filtered coffee, and instant coffee were associated with the risk of CAC (β = 0.79, 95% CI: 0.12 to 1.47, p = 0.022; β = 0.66, 95% CI: 0.17 to 1.15, p = 0.008; β = 0.66, 95% CI: 0.20 to 1.13, p = 0.005; respectively). While no significant causal relationship was found between decaffeinated coffee and CAC (β = -1.32, 95% CI: -2.67 to 0.04, p = 0.056). The association between coffee and CAC was validated in the replication analysis (β = 0.27, 95% CI: 0.07 to 0.48, p = 0.009). Body mass index mediated 39.98% of the effect of coffee on CAC (95% CI: 9.78 to 70.19%, p = 0.009), and 5.79% of the effect of instant coffee on CAC (95% CI: 0.54 to 11.04%, p = 0.030).

Conclusion

Our study suggests that coffee other than decaffeinated coffee increases the risk of subclinical atherosclerosis inferred from CAC. Body mass index mediated 39.98 and 5.79% of the causal effects of coffee and instant coffee on CAC, respectively. Coffee should be consumed with caution, especially in individuals with established cardiovascular risk factors, and decaffeinated coffee appears to be a safer choice.

Effect of coffee, tea and alcohol intake on circulating inflammatory cytokines: a two sample-Mendelian randomization study

BACKGROUND

Despite the abundance of research examining the effects of coffee, tea, and alcohol on inflammatory diseases, there is a notable absence of conclusive evidence regarding their direct causal influence on circulating inflammatory cytokines. Previous studies have primarily concentrated on established cytokines, neglecting the potential impact of beverage consumption on lesser-studied but equally important cytokines.

METHODS

Information regarding the consumption of coffee, tea, and alcohol was collected from the UK Biobank, with sample sizes of 428,860, 447,485, and 462,346 individuals, respectively. Data on 41 inflammatory cytokines were obtained from summary statistics of 8293 healthy participants from Finnish cohorts.

RESULTS

The consumption of coffee was found to be potentially associated with decreased levels of Macrophage colony-stimulating factor (β = -0.57, 95% CI -1.06 ~ -0.08; p = 0.022) and Stem cell growth factor beta (β = -0.64, 95% CI -1.16 ~ -0.12; p = 0.016), as well as an increase in TNF-related apoptosis-inducing ligand (β = 0.43, 95% CI 0.06 ~ 0.8; p = 0.023) levels. Conversely, tea intake was potentially correlated with a reduction in Interleukin-8 (β = -0.45, 95% CI -0.9 ~ 0; p = 0.045) levels. Moreover, our results indicated an association between alcohol consumption and decreased levels of Regulated on Activation, Normal T Cell Expressed and Secreted (β = -0.24, 95% CI -0.48 ~ 0; p = 0.047), as well as an increase in Stem cell factor (β = 0.17, 95% CI 0.02 ~ 0.31; p = 0.023) and Stromal cell-derived factor-1 alpha (β = 0.20, 95% CI 0.04 ~ 0.36; p = 0.013).

CONCLUSION

Revealing the interactions between beverage consumption and various inflammatory cytokines may lead to the discovery of novel therapeutic targets, thereby facilitating dietary interventions to complement clinical disease treatments.

Causal association of genetically determined caffeine intake from tea or coffee with bone health: a two-sample Mendelian randomization study

BACKGROUND

Relationship of caffeine intake and consumption of caffeinated beverages, such as tea and coffee, with bone health remains controversial. This study aimed to evaluate whether genetically determined caffeine intake from tea or coffee has causal effects on overall total body bone mineral density (TB-BMD) and fracture. We also assessed the association with TB-BMD in five age strata.

METHODS

Using two-sample Mendelian randomization approach, summary statistics were retrieved from genome-wide association studies (GWAS)/GWAS meta-analyses of caffeine intake from tea (n = 395 866)/coffee (n = 373 522), TB-BMD (n = 66 628), and fracture (n = 426 795). Inverse variance weighted method was adopted as the main univariable analysis. Multivariable analysis was conducted to evaluate whether the causal effect is independent.

RESULTS

In univariable analysis, genetically determined caffeine intake from tea had positive association with overall TB-BMD (per SD increase in genetically determined caffeine intake, beta of TB-BMD [in SD]: 0.166; 95% confidence interval (CI): 0.006-0.326) and inverse association with fracture (OR = 0.79; 95% CI: 0.654-0.954). Genetically determined caffeine intake from coffee was also positively associated with overall TB-BMD (beta = 0.231; 95% CI: 0.093-0.369). The association remained significant after adjustment for smoking in multivariable analysis. Genetically determined caffeine intake from tea or coffee was both positively associated with TB-BMD in the age strata of 45-60 years, but we lacked evidence of association in other strata.

CONCLUSIONS

Genetically, caffeine intake from tea or coffee may be beneficial to bone health. Due to the ascertainment method of caffeine intake from tea, our study also implied genetically higher tea consumption may improve TB-BMD and lower fracture risk.

Beverages - a scoping review for Nordic Nutrition Recommendations 2023

Background: Coffee, tea, sugar-sweetened beverages (SSBs), and low- and no-calorie sweetened beverages (LNCSBs) are generally frequently consumed in the Nordic and Baltic countries. These beverages have also been related to potential health effects. This scoping review describes the evidence for the role of coffee, tea, SSBs, and LNCSBs for health-related outcomes as a basis for setting and updating food-based dietary guidelines. We used evidence from several qualified systematic reviews (i.e. World Cancer Research Fund, US Dietary Guidelines Advisory Committee, European Food Safety Authority, and World Health Organization) and performed a search for additional systematic reviews. The evidence suggests that moderate coffee and tea consumption do not have long-term adverse health effects. The long-term favorable effects of coffee consumption are related to reduced risk of endometrial and liver cancer, type 2 diabetes, and cardiovascular deaths. However, results from randomized controlled trials (RCTs) suggest that coffee brews that are rich in diterpenes, such as boiled coffee, increase serum cholesterol concentrations. High caffeine intake in pregnancy is associated with higher risk of pregnancy loss, preterm birth, and low birth weight. High consumption of SSBs has been associated with increased risk of obesity, type 2 diabetes, hypertension, and cardiovascular disease, based on data from RCTs and prospective cohort studies. The consumption of LNCSBs may result in a small reduction in body weight in adults, likely mediated through the effect of reduced energy intake, but has neutral effects on other cardiometabolic risk markers using evidence from RCTs. However, evidence from observational studies indicates increased risk of cardiometabolic diseases among high LNCSB consumers. In conclusion, current evidence suggests that moderate coffee and tea consumption have no long-term adverse health effects. The evidence of beneficial effects of coffee consumption on liver and endometrial cancer risk, and some cardiovascular outcomes, comes from observational studies. High consumption of boiled coffee should be avoided due to negative effect on lipid profile. Pregnant women should not exceed the recommended daily dose of caffeine intake of 200 mg set by the European Food Safety Authority as a safe level for the fetus. High consumption of SSBs has consistently been associated with adverse health effects, which is mainly due to excess energy intake, and should be limited. The conflicting results from RCTs and observational studies regarding LNCSBs may be due to revere causation and should be explored further.

Genetic association between coffee/caffeine consumption and the risk of obstructive sleep apnea in the European population: a two-sample Mendelian randomization study

BACKGROUND

The association between coffee/caffeine consumption and obstructive sleep apnea (OSA) risk remains unclear.

PURPOSE

To determine the relationship between coffee/caffeine consumption and the risk of OSA, using the Mendelian randomization (MR) method in the European population.

METHODS

Two sets of coffee consumption-associated genetic variants were, respectively, extracted from the recent genome-wide meta-analysis (GWMA) and genome-wide association study (GWAS) of coffee consumption. Taking other caffeine sources into account, genetic variants associated with caffeine consumption from tea and plasma caffeine (reflecting total caffeine intake) were also obtained. The inverse variance weighted (IVW) technique was utilized as the primary analysis, supplemented by the MR-Egger, weighted-median, and MR-Pleiotropy RESidual Sum and Outlier (PRESSO) techniques. Leave-one-out (LOO) analysis was performed to assess whether the overall casual estimates were driven by a single SNP. Additional sensitivity analyses were performed using similar methods, while the genetic variants associated with confounders, e.g., body mass index and hypertension, were excluded.

RESULTS

The IVW method demonstrated that coffee consumption GWMA (OR: 1.065, 95% CI 0.927-1.224, p = 0.376), coffee consumption GWAS (OR: 1.665, 95% CI 0.932-2.977, p = 0.086), caffeine from tea (OR: 1.198, 95% CI 0.936-1.534, p = 0.151), and blood caffeine levels (OR: 1.054, 95% CI 0.902-1.231, p = 0.508) were unlikely to be associated with the risk of OSA. The other three methods presented similar results, where no significant associations were found. No single genetic variant was driving the overall estimates by the LOO analysis. These findings were also supported by the sensitivity analyses with no confounding genetic variants.

CONCLUSION

Our study found no association between coffee/caffeine consumption and the risk of OSA.

Appraising the Causal Role of Risk Factors in Coronary Artery Disease and Stroke: A Systematic Review of Mendelian Randomization Studies

BACKGROUND Mendelian randomization (MR) offers a powerful approach to study potential causal associations between exposures and health outcomes by using genetic variants associated with an exposure as instrumental variables. In this systematic review, we aimed to summarize previous MR studies and to evaluate the evidence for causality for a broad range of exposures in relation to coronary artery disease and stroke. METHODS AND RESULTS MR studies investigating the association of any genetically predicted exposure with coronary artery disease or stroke were identified. Studies were classified into 4 categories built on the significance of the main MR analysis results and its concordance with sensitivity analyses, namely, robust, probable, suggestive, and insufficient. Studies reporting associations that did not perform any sensitivity analysis were classified as nonevaluable. We identified 2725 associations eligible for evaluation, examining 535 distinct exposures. Of them, 141 were classified as robust, 353 as probable, 110 as suggestive, and 926 had insufficient evidence. The most robust associations were observed for anthropometric traits, lipids, and lipoproteins and type 2 diabetes with coronary artery; disease and clinical measurements with coronary artery disease and stroke; and thrombotic factors with stroke. CONCLUSIONS Despite the large number of studies that have been conducted, only a limited number of associations were supported by robust evidence. Approximately half of the studies reporting associations presented an MR sensitivity analysis along with the main analysis that further supported the causality of associations. Future research should focus on more thorough assessments of sensitivity MR analyses and further assessments of mediation effects or nonlinearity of associations.

Genome-Wide Association Studies of Coffee Intake in UK/US Participants of European Ancestry Uncover Gene-Cohort Influences

Coffee is one of the most widely consumed beverages. We performed a genome-wide association study (GWAS) of coffee intake in US-based 23andMe participants (N=130,153) and identified 7 significant loci, with many replicating in three multi-ancestral cohorts. We examined genetic correlations and performed a phenome-wide association study across thousands of biomarkers and health and lifestyle traits, then compared our results to the largest available GWAS of coffee intake from UK Biobank (UKB; N=334,659). The results of these two GWAS were highly discrepant. We observed positive genetic correlations between coffee intake and psychiatric illnesses, pain, and gastrointestinal traits in 23andMe that were absent or negative in UKB. Genetic correlations with cognition were negative in 23andMe but positive in UKB. The only consistent observations were positive genetic correlations with substance use and obesity. Our study shows that GWAS in different cohorts could capture cultural differences in the relationship between behavior and genetics.

Genetic Underpinnings of the Transition From Alcohol Consumption to Alcohol Use Disorder: Shared and Unique Genetic Architectures in a Cross-Ancestry Sample

OBJECTIVE

Recent genome-wide association studies (GWASs) of alcohol-related phenotypes have uncovered key differences in the underlying genetic architectures of alcohol consumption and alcohol use disorder (AUD), with the two traits having opposite genetic correlations with psychiatric disorders. Understanding the genetic factors that underlie the transition from heavy drinking to AUD has important theoretical and clinical implications.

METHODS

The authors used longitudinal data from the cross-ancestry Million Veteran Program sample to identify 1) novel loci associated with AUD and alcohol consumption (measured by the score on the consumption subscale of the Alcohol Use Disorders Identification Test [AUDIT-C]), 2) the impact of phenotypic variation on genetic discovery, and 3) genetic variants with direct effects on AUD that are not mediated through alcohol consumption.

RESULTS

The authors identified 26 loci associated with AUD and 22 loci associated with AUDIT-C score, including ancestry-specific and novel loci. In secondary GWASs that excluded individuals who report abstinence, the authors identified seven additional loci for AUD and eight additional loci for AUDIT-C score. Although the heterogeneity of the abstinent group biases the GWAS findings, unique variance between alcohol consumption and disorder remained after the abstinent group was excluded. Finally, using mediation analysis, the authors identified a set of variants with effects on AUD that are not mediated through alcohol consumption.

CONCLUSIONS

Differences in genetic architecture between alcohol consumption and AUD are consistent with their having different biological contributions. Genetic variants with direct effects on AUD are potentially relevant to understanding the transition from heavy alcohol consumption to AUD and may be targets for translational prevention and treatment efforts.

Overview of Caffeine Effects on Human Health and Emerging Delivery Strategies

Caffeine is a naturally occurring alkaloid found in various plants. It acts as a stimulant, antioxidant, anti-inflammatory, and even an aid in pain management, and is found in several over-the-counter medications. This naturally derived bioactive compound is the best-known ingredient in coffee and other beverages, such as tea, soft drinks, and energy drinks, and is widely consumed worldwide. Therefore, it is extremely important to research the effects of this substance on the human body. With this in mind, caffeine and its derivatives have been extensively studied to evaluate its ability to prevent diseases and exert anti-aging and neuroprotective effects. This review is intended to provide an overview of caffeine's effects on cancer and cardiovascular, immunological, inflammatory, and neurological diseases, among others. The heavily researched area of caffeine in sports will also be discussed. Finally, recent advances in the development of novel nanocarrier-based formulations, to enhance the bioavailability of caffeine and its beneficial effects will be discussed.

Tea Consumption and New-Onset Acute Kidney Injury: The Effects of Milk or Sweeteners Addition and Caffeine/Coffee

Aims: To explore the relationship between tea consumption and the risk of incident acute kidney injury (AKI) and examine the effects of coffee consumption, genetic variation in caffeine metabolism, and the use of tea additives (milk and sweeteners) on this association. Methods: Using data from the UK Biobank, 498,621 participants who were free of AKI and had information on tea intake were included. Black tea is the main type consumed in this population. Dietary information was collected from standardized and validated Food-Frequency Questionnaire (FFQ). Outcome was incident AKI, determined via primary care data, hospital inpatient data, death register records, or self-reported data at follow-up visits. Results: After a median follow-up period of 12.0 years, 21,202 participants occurred AKI. Overall, there was a reversed J-shaped relation between tea consumption and incident AKI, with an inflection point at 3.5 cup/d (p for nonlinearity < 0.001). The relation was similar among participants with different genetically predicted caffeine metabolism (p-interaction = 0.684), while a more obvious positive association was found between heavy tea consumption and AKI when more coffee was consumed (p-interaction < 0.001). Meanwhile, there was a reversed J-shaped relationship for drinking tea with neither milk nor sweeteners, and a L-shaped association for drinking tea with milk (with or without sweeteners) with incident AKI. However, no significant association was found between drinking tea with sweeteners only and incident AKI. Conclusions: There was a reversed J-shaped relation between tea consumption and incident AKI, suggesting that light to moderate tea consumption, especially adding milk, can be part of a healthy diet.

Deeply functional identification of TCS1 alleles provides efficient technical paths for low-caffeine breeding of tea plants

Caffeine is an important functional component in tea, which has the effect of excitement and nerve stimulation, but excessive intake can cause insomnia and dysphoria. Therefore, the production of tea with low-caffeine content can meet the consumption needs of certain people. Here, in addition to the previous alleles of the tea caffeine synthase (TCS1) gene, a new allele (TCS1h) from tea germplasms was identified. Results of in vitro activity analysis showed that TCS1h had both theobromine synthase (TS) and caffeine synthase (CS) activities. Site-directed mutagenesis experiments of TCS1a, TCS1c, and TCS1h demonstrated that apart from the 225th amino acid residue, the 269th amino acid also determined the CS activity. GUS histochemical analysis and dual-luciferase assay indicated the low promoter activity of TCS1e and TCS1f. In parallel, insertion and deletion mutations in large fragments of alleles and experiments of site-directed mutagenesis identified a key cis-acting element (G-box). Furthermore, it was found that the contents of purine alkaloids were related to the expression of corresponding functional genes and alleles, and the absence or presence and level of gene expression determined the content of purine alkaloids in tea plants to a certain extent. In summary, we concluded TCS1 alleles into three types with different functions and proposed a strategy to effectively enhance low-caffeine tea germplasms in breeding practices. This research provided an applicable technical avenue for accelerating the cultivation of specific low-caffeine tea plants.

Appraisal of the causal effect of plasma caffeine on adiposity, type 2 diabetes, and cardiovascular disease: two sample mendelian randomisation study

Objective

To investigate the potential causal effects of long term plasma caffeine concentrations on adiposity, type 2 diabetes, and major cardiovascular diseases.

Design

Two sample mendelian randomisation study.

Setting

Genome-wide association study summary data for associations of two single nucleotide polymorphisms associated with plasma caffeine at the genome-wide significance threshold (rs2472297 near the CYP1A2 gene and rs4410790 near the AHR gene) and their association with the outcomes.

Participants

Primarily individuals of European ancestry participating in cohorts contributing to genome-wide association study consortia.

Main outcome measures

Outcomes studied were body mass index, whole body fat mass, whole body fat-free mass, type 2 diabetes, ischaemic heart disease, atrial fibrillation, heart failure, and stroke.

Results

Higher genetically predicted plasma caffeine concentrations were associated with lower body mass index (beta -0.08 standard deviation (SD) (95% confidence interval -0.10 to -0.06), where 1 SD equals about 4.8 kg/m² in body mass index, for every standard deviation increase in plasma caffeine) and whole body fat mass (beta -0.06 SD (-0.08 to -0.04), 1 SD equals about 9.5 kg; P<0.001) but not fat-free mass (beta -0.01 SD (-0.02 to -0.00), 1 SD equals about 11.5 kg; P=0.17). Higher genetically predicted plasma caffeine concentrations were associated with a lower risk of type 2 diabetes in two consortia (FinnGen and DIAMANTE), with a combined odds ratio of 0.81 ((95% confidence interval 0.74 to 0.89); P<0.001). Approximately half (43%; 95% confidence interval 30% to 61%) of the effect of caffeine on type 2 diabetes was estimated to be mediated through body mass index reduction. No strong associations were reported between genetically predicted plasma caffeine concentrations and a risk of any of the studied cardiovascular diseases.

Conclusions

Higher plasma caffeine concentrations might reduce adiposity and risk of type 2 diabetes. Further clinical study is warranted to investigate the translational potential of these findings towards reducing the burden of metabolic disease.

Effects of metabolic traits, lifestyle factors, and pharmacological interventions on liver fat: mendelian randomisation study

Objective

To investigate the effects of metabolic traits, lifestyle factors, and drug interventions on liver fat using the mendelian randomisation paradigm.

Design

Mendelian randomisation study.

Setting

Publicly available summary level data from genome-wide association studies.

Participants

Genome-wide association studies of 32 974 to 1 407 282 individuals who were predominantly of European descent.

Exposures

Genetic variants predicting nine metabolic traits, six lifestyle factors, four lipid lowering drug targets, three antihypertensive drug targets, and genetic association estimates formagnetic resonance imaging measured liver fat.

Main outcome measures

Mendelian randomisation analysis was used to investigate the effects of these exposures on liver fat, incorporating sensitivity analyses that relaxed the requisite modelling assumptions.

Results

Genetically predicted liability to obesity, type 2 diabetes, elevated blood pressure, elevated triglyceride levels, cigarette smoking, and sedentary time watching television were associated with higher levels of liver fat. Genetically predicted lipid lowering drug effects were not associated with liver fat; however, β blocker and calcium channel blocker antihypertensive drug effects were associated with lower levels of liver fat.

Conclusion

These analyses provide evidence of a causal effect of various metabolic traits, lifestyle factors, and drug targets on liver fat. The findings complement existing epidemiological associations, further provide mechanistic insight, and potentially supports a role for drug interventions in reducing the burden of hepatic steatosis and related disease. Further clinical study is now warranted to investigate the relevance of these genetic analyses for patient care.

Genetic estimation of correlations and causalities between multifaceted modifiable factors and gastro-oesophageal reflux disease

BACKGROUND

Gastro-oesophageal reflux disease (GORD) is a common gastrointestinal dysfunction that significantly affects the quality of daily life, and health interventions are challenging to prevent the risk of GORD. In this study, we used Mendelian randomization framework to genetically determine the causal associations between multifaceted modifiable factors and the risk of GORD.

MATERIALS AND METHODS

Sixty-six exposures with available instrumental variables (IVs) across 6 modifiable pathways were included in the univariable MR analysis (UVMR). Summary-level genome-wide association studies (GWAS) datasets for GORD were retrieved from the Neale Lab (GORD _Neale , Ncases = 29975, Ncontrols = 390556) and FinnGen (GORD _Finn , Ncases = 13141, Ncontrols = 89695). Using the METAL software, meta-analysis for single nucleotide polymorphisms (SNPs) from GORD _Neale and GORD _Finn was conducted with an inverse variance weighted (IVW) fixed-effect model. Moreover, we leveraged partition around medoids (PAM) clustering algorithm to cluster genetic correlation subtypes, whose hub exposures were conditioned for multivariable MR (MVMR) analyses. P-values were adjusted with Bonferroni multiple comparisons.

RESULTS

Significant causal associations were identified between 26 exposures (15 risk exposures and 11 protective exposures) and the risk of GORD. Among them, 13 risk exposures [lifetime smoking, cigarette consumption, insomnia, short sleep, leisure sedentary behavior (TV watching), body mass index (BMI), body fat percentage, whole body fat mass, visceral adipose tissue, waist circumference, hip circumference, major depressive disorder, and anxious feeling], and 10 protective exposures (leisure sedentary behavior (computer use), sitting height, hand grip strength (left and right), birth weight, life satisfaction, positive affect, income, educational attainment, and intelligence) showed novel significant causal associations with the risk of GORD. Moreover, 13 exposures still demonstrated independent associations with the risk of GORD following MVMR analyses conditioned for hub exposures (educational attainment, smoking initiation and BMI). In addition, 12 exposures showed suggestive causal associations with the risk of GORD.

CONCLUSION

This study systematically elucidated the modifiable factors causally associated with the risk of GORD from multifaceted perspectives, which provided implications for prevention and treatment of GORD.

Addictive behavior and incident gallstone disease: A dose-response meta-analysis and Mendelian randomization study

Background

Previous studies have suggested associations between addictive behavior and gallstone disease (GSD) risk, yet conflicting results exist. It also remains unclear whether this association is causal or due to confounding or reverse associations. The present study aims to systematically analyze the epidemiological evidence for these associations, as well as estimate the potential causal relationships using Mendelian randomization (MR).

Methods

We analyzed four common addictive behaviors, including cigarette smoking, alcohol intake, coffee, and tea consumption (N = 126,906–4,584,729 participants) in this meta-analysis based on longitudinal studies. The two-sample MR was conducted using summary data from genome-wide associations with European ancestry (up to 1.2 million individuals).

Results

An observational association of GSD risk was identified for smoking [RR: 1.17 (95% CI: 1.06–1.29)], drinking alcohol [0.84 (0.78–0.91)], consuming coffee [0.86 (0.79–0.93)], and tea [1.08 (1.04–1.12)]. Also, there was a linear relationship between smoking (pack-years), alcohol drinking (days per week), coffee consumption (cups per day), and GSD risk. Our MRs supported a causality of GSD incidence with lifetime smoking [1.008 (1.003–1.013), P = 0.001], current smoking [1.007 (1.002–1.011), P = 0.004], problematic alcohol use (PAU) [1.014 (1.001–1.026), P = 0.029], decaffeinated coffee intake (1.127 [1.043–1.217], P = 0.002), as well as caffeine-metabolism [0.997 (0.995–0.999), P = 0.013], and tea consumption [0.990 (0.982–0.997), P = 0.008], respectively.

Conclusion

Our study suggests cigarette smoking, alcohol abuse, and decaffeinated coffee are causal risk factors for GSD, whereas tea consumption can decrease the risk of gallstones due to the effect of caffeine metabolism or polyphenol intake.

A novel TcS allele conferring the high-theacrine and low-caffeine traits and having potential use in tea plant breeding

Theacrine (1,3,7,9-tetramethyluric acid) is a natural product with remarkable pharmacological activities such as antidepressant, sedative and hypnotic activities, while caffeine (1,3,7-trimethylxanthine) has certain side effects to special populations. Hence, breeding tea plants with high theacrine and low caffeine will increase tea health benefits and promote consumption. In this study, we construct an F₁ population by crossing 'Zhongcha 302' (theacrine-free) and a tea germplasm 'Ruyuan Kucha' (RY, theacrine-rich) to identify the causal gene for accumulating theacrine. The results showed that the content of theacrine was highly negatively correlated with caffeine (R² > 0.9). Bulked segregant RNA sequencing analysis, molecular markers and gene expression analysis indicated that the theacrine synthase (TcS) gene was the candidate gene. The TcS was located in the nucleus and cytoplasm, and the theacrine can be detected in stably genetic transformed tobacco by feeding the substrate 1,3,7-trimethyluric acid. Moreover, an in vitro enzyme activity experiment revealed that the 241st amino acid residue was the key residue. Besides, we amplified the promoter region in several tea accessions with varied theacrine levels, and found a 234-bp deletion and a 271-bp insertion in RY. Both GUS histochemical analysis and dual-luciferase assay showed that TcS promoter activity in RY was relatively high. Lastly, we developed a molecular marker that is co-segregate with high-theacrine individuals in RY's offspring. These results demonstrate that the novel TcS allele in RY results in the high-theacrine and low-caffeine traits and the developed functional marker will facilitate the breeding of characteristic tea plants.

Dietary sources, health benefits, and risks of caffeine

Dietary intake of caffeine has significantly increased in recent years, and beneficial and harmful effects of caffeine have been extensively studied. This paper reviews antioxidant and anti-inflammatory activities of caffeine as well as its protective effects on cardiovascular diseases, obesity, diabetes mellitus, cancers, and neurodegenerative and liver diseases. In addition, we summarize the side effects of long-term or excessive caffeine consumption on sleep, migraine, intraocular pressure, pregnant women, children, and adolescents. The health benefits of caffeine depend on the amount of caffeine intake and the physical condition of consumers. Moderate intake of caffeine helps to prevent and modulate several diseases. However, the long-term or over-consumption of caffeine can lead to addiction, insomnia, migraine, and other side effects. In addition, children, adolescents, pregnant women, and people who are sensitive to caffeine should be recommended to restrict/reduce their intake to avoid potential adverse effects.

Coffee Types and Type 2 Diabetes Mellitus: Large-Scale Cross-Phenotype Association Study and Mendelian Randomization Analysis

PURPOSE

To explore whether coffee intake is associated with the risk of type 2 diabetes mellitus (T2DM) from a genetic perspective, and whether this association remains the same among different types of coffee consumers.

METHODS

We utilized the summary-level results of 12 genome-wide association studies. First, we used linkage disequilibrium score regression and cross-phenotype association analysis to estimate the genetic correlation and identify shared genes between coffee intake and T2DM in addition to some other T2DM-related phenotypes. Second, we used Mendelian randomization (MR) analysis to test whether there is a significant genetically predicted causal association between coffee intake and the risk of T2DM or other T2DM-related phenotypes. For all the analyses above, we also conducted a separate analysis for different types of coffee consumers, in addition to total coffee intake.

RESULTS

Genetically, choice for ground coffee was significantly negatively associated with the risk of T2DM and some other related risks. While coffee intake and choice for decaffeinated/instant coffee had significant positive correlation with these risks. Between these genetically related phenotypes, there were 1571 genomic shared regions, of which 134 loci were novel. Enrichment analysis showed that these shared genes were significantly enriched in antigen processing related biological processes. MR analysis indicated that higher genetically proxied choice for ground coffee can reduce the risk of T2DM (T2DM: b: -0.2, p-value: 4.70×10^-10; T2DM adjusted for body mass index (BMI): b: -0.11, p-value: 4.60×10^-5), and BMI (b: -0.08, p-value: 6.50×10^-5).

CONCLUSIONS

Compared with other types of coffee, ground coffee has a significant negative genetic and genetically predicated causal relationship with the risk of T2DM. And this association is likely to be mediated by immunity. The effect of different coffee types on T2DM is not equal, researchers on coffee should pay more attention to distinguishing between coffee types.

The Cardiovascular Benefits of Caffeinated Beverages: Real or Surreal? /"Metron Ariston - All in Moderation"

Caffeinated beverages are the most widely consumed beverages globally with coffee and tea as the two most prominent sources of caffeine. Caffeine content varies across different types of beverages. In addition to caffeine, coffee and tea have other biologically active compounds, and all may affect general and cardiovascular (CV) health. Moderate caffeine consumption (<300-400 mg/day), regardless of the source, is considered safe by both European and US Health Authorities, as it is not associated with adverse health and CV effects, while it may confer certain health benefits. There is a nonlinear association between coffee ingestion and CV risk; moderate coffee drinking is inversely significantly associated with CV risk, with the highest benefit at 2-4 cups per day, while heavy coffee drinking might confer increased risk. With regards to tea, due to a lower caffeine content per serving, its consumption is only limited by the total caffeine daily intake. Both these caffeinated beverages, coffee and tea, have additional phenolic compounds, with anti-oxidant and anti-inflammatory activities, which confer cardioprotective benefits. Of the several coffee compounds, chloroacetic acids and melanoidins offer such beneficial effects, while diterpenes may have unfavorable effects on lipids. Most of the tea ingredients (polyphenols) are cardioprotective. A major concern relates to energy drinks with their much higher caffeine content which puts individuals, especially adolescents and young adults, at high health and CV risk. All these issues are herein discussed, including pertinent studies and meta-analyses, pathogenetic mechanisms involved and relevant recommendations from health authorities.

Coffee and Lower Risk of Type 2 Diabetes: Arguments for a Causal Relationship

Prospective epidemiological studies concur in an association between habitual coffee consumption and a lower risk of type 2 diabetes. Several aspects of these studies support a cause–effect relationship. There is a dependency on daily coffee dose. Study outcomes are similar in different regions of the world, show no differences between sexes, between obese versus lean, young versus old, smokers versus nonsmokers, regardless of the number of confounders adjusted for. Randomized controlled intervention trials did not find a consistent impact of drinking coffee on acute metabolic control, except for effects of caffeine. Therefore, lowering of diabetes risk by coffee consumption does not involve an acute effect on the post-meal course of blood glucose, insulin or insulin resistance. Several studies in animals and humans find that the ingestion of coffee phytochemicals induces an adaptive cellular response characterized by upregulation and de novo synthesis of enzymes involved in cell defense and repair. A key regulator is the nuclear factor erythroid 2-related factor 2 (Nrf2) in association with the aryl hydrocarbon receptor, AMP-activated kinase and sirtuins. One major site of coffee actions appears to be the liver, causing improved fat oxidation and lower risk of steatosis. Another major effect of coffee intake is preservation of functional beta cell mass via enhanced mitochondrial function, lower endoplasmic reticulum stress and prevention or clearance of aggregates of misfolded proinsulin or amylin. Long-term preservation of proper liver and beta cell function may account for the association of habitual coffee drinking with a lower risk of type 2 diabetes, rather than acute improvement of metabolic control.

Associations of Observational and Genetically Determined Caffeine Intake With Coronary Artery Disease and Diabetes Mellitus

Background

Caffeine is the most widely consumed psychostimulant and is associated with lower risk of coronary artery disease (CAD) and type 2 diabetes mellitus (T2DM). However, whether these associations are causal remains unknown. This study aimed to identify genetic variants associated with caffeine intake, and to investigate evidence for causal links with CAD or T2DM. In addition, we aimed to replicate previous observational findings.

Methods and Results

Observational associations were tested within UK Biobank using Cox regression analyses. Moderate observational caffeine intakes from coffee or tea were associated with lower risks of CAD or T2DM, with the lowest risks at intakes of 121 to 180 mg/day from coffee for CAD (hazard ratio [HR], 0.77 [95% CI, 0.73–0.82; P<1×10⁻¹⁶]), and 301 to 360 mg/day for T2DM (HR, 0.76 [95% CI, 0.67–0.86]; P=1.57×10⁻⁵). Next, genome‐wide association studies were performed on self‐reported caffeine intake from coffee, tea, or both in 407 072 UK Biobank participants. These analyses identified 51 novel genetic variants associated with caffeine intake at P<1.67×10⁻⁸. These loci were enriched for central nervous system genes. However, in contrast to the observational analyses, 2‐sample Mendelian randomization analyses using the identified loci in independent disease‐specific cohorts yielded no evidence for causal links between genetically determined caffeine intake and the development of CAD or T2DM.

Conclusions

Mendelian randomization analyses indicate genetically determined higher caffeine intake might not protect against CAD or T2DM, despite protective associations in observational analyses.