Cardiometabolic effects of two coffee blends differing in content for major constituents in overweight adults: a randomized controlled trial.

PURPOSE: The hypothesis was tested that coffee types differing in content of major constituents also differ with regard to cardiometabolic effects. METHODS: Overweight persons (n = 118) were randomized to consume a dark roast [rich in N-methylpyridinium (NMP)] or medium roast (rich in caffeoylquinic acids, trigonelline) coffee blend for 3 months, after a washout period of 4 weeks. Before and after the intervention period, body weight and 15 further general and biochemical parameters were determined. RESULTS: Participants consumed an average of 4-5 cups per day. Mean body weight, body mass index and waist circumference did not change during the coffee consumption phase in either of the study groups. Systolic blood pressure decreased in the dark roast coffee group only (p < 0.05). High-density lipoprotein cholesterol levels increased in the medium roast coffee group only, and triglyceride levels increased in the dark roast coffee group only. Glucoregulation and insulin levels were not affected, although there was a small increase of hemoglobin A1c values in both groups. An increase of adiponectin levels occurred in the medium roast coffee group only and was negatively associated with NMP concentrations. Differences did not remain statistically significant after correction for multiple testing. CONCLUSIONS: Medium and dark roast coffee blends exert small but possibly relevant different cardiometabolic effects. Further studies of health outcomes in relation to coffee constituents seem warranted.

A dark brown roast coffee blend is less effective at stimulating gastric acid secretion in healthy volunteers compared to a medium roast market blend.

Coffee consumption sometimes is associated with symptoms of stomach discomfort. This work aimed to elucidate whether two coffee beverages, containing similar amounts of caffeine, but differing in their concentrations of (ß) N-alkanoyl-5-hydroxytryptamides (C5HTs), chlorogenic acids (CGAs), trigonelline, and N-methylpyridinium (N-MP) have different effects on gastric acid secretion in healthy volunteers. The intragastric pH after administration of bicarbonate with/without 200 mL of a coffee beverage prepared from a market blend or dark roast blend was analyzed in nine healthy volunteers. Coffee beverages were analyzed for their contents of C5HT, N-MP, trigonelline, CGAs, and caffeine using HPLC-DAD and HPLC-MS/MS. Chemical analysis revealed higher concentrations of N-MP for the dark brown blend (87 mg/L) compared to the market blend coffee (29 mg/L), whereas concentrations of C5HT (0.012 versus 0.343 mg/L), CGAs (323 versus 1126 mg/L), and trigonelline (119 versus 343 mg/L) were lower, and caffeine concentrations were similar (607 versus 674 mg/mL). Gastric acid secretion was less effectively stimulated after administration of the dark roast blend coffee compared to the market blend. Future studies are warranted to verify whether a high ratio of N-MP to C5HT and CGAs is beneficial for reducing coffee-associated gastric acid secretion.

N-methylpyridinium, a degradation product of trigonelline upon coffee roasting, stimulates respiratory activity and promotes glucose utilization in HepG2 cells.

N-Methylpyridinium (NMP) is a thermal degradation product of trigonelline formed upon coffee roasting and hypothesized to exert several health benefits in humans. Since for trigonelline evidence for hypoglycemic effects exists, we examined whether NMP also affects mechanisms of glucose utilization and cellular energy formation. For this purpose, the impact of trigonelline and NMP on respiratory activity, extracellular acidification, cellular adenosine nucleotides, energy supply from fatty acids and glucose as well as thermogenesis in HepG2 cells was analyzed. A 24 hour incubation with nanomolar concentrations of NMP enhanced oxygen consumption rates, resulting in increased ATP levels. Glucose was identified as the prevalent energy substrate as its uptake was augmented up to 18.1% ± 7.44% by NMP at 0.09 µM, whereas the uptake of fatty acids decreased upon NMP treatment. Cellular glucose uptake was also stimulated by trigonelline administration; however, a shift to the anaerobic energy production pathway was monitored. Both pyridine derivatives induced thermogenesis, although trigonelline presumably promoted proton leaks, while NMP increased the concentration of the uncoupling protein-2. We provide evidence that both compounds appear to stimulate cellular energy metabolism in HepG2 cells. Human intervention studies are warranted to ensure these effects in vivo.

Potential antioxidant response to coffee - A matter of genotype?

In a human intervention study, coffee combining natural green coffee bean constituents and dark roast products was identified as a genotype-dependent inducer of the Nrf2/ARE pathway, significantly affecting Nrf2 gene expression and downstream GST1A1 and UGT1A1 gene transcription. The observed transcriptional changes correlated with the presence of specific Nrf2 genotypes suggesting their influence on both Nrf2 and subsequent ARE-dependent GST1A1 and UGT1A1 transcription. While the presence of the - 653 SNP seems to be advantageous, resulting in higher Nrf2, GST1A1 and UGT1A1 gene transcription following coffee consumption, in contrast, the presence of the - 651 SNP significantly down-regulated the response to the study coffee. Furthermore, the presence of the B/B genotype in GST1A1 along with the frequency of the [TA]6/6 and [TA]7/7 polymorphisms in UGT1A1 appeared to significantly increase sensitivity toward coffee-induced gene transcription. This data suggests that when examining the role of the Nrf2/ARE pathway in the regulation of antioxidative and chemopreventive phase II efficacy, individual genotypes should be included when considering the potency of bioactive food/food constituents and their therapeutic potential.

Quantitative studies on roast kinetics for bioactives in coffee.

Quantitative analysis of the bioactives trigonelline (1), N-methylpyridinium (2), caffeine (3), and caffeoylquinic acids (4) in a large set of roasted Arabica (total sample size n = 113) and Robusta coffees (total sample size n = 38) revealed that the concentrations of 1 and 4 significantly correlated with the roasting color (P < 0.001, two tailed), whereas that of 2 significantly correlated inversely with the color (P < 0.001, two tailed). As dark-roasted coffees were rich in N-methylpyridinium whereas light-roasted coffees were rich in trigonelline and caffeoylquinic acids, manufacturing of roast coffees rich in all four bioactives would therefore necessitate blending of two or even more coffees of different roasting colors. Additional experiments on the migration rates during coffee brewing showed that all four bioactives were nearly quantitatively extracted in the brew (>90%) when a water volume/coffee powder ratio of >16 was used.

Effect of coffee combining green coffee bean constituents with typical roasting products on the Nrf2/ARE pathway in vitro and in vivo.

This study investigated Nrf2-activating properties of a coffee blend combining raw coffee bean constituents with 5-O-caffeoylquinic acid (CGA) as a lead component with typical roasting products such as N-methylpyridinium (NMP). In cell culture (HT29) the respective coffee extract (CN-CE) increased nuclear Nrf2 translocation and enhanced the transcription of ARE-dependent genes as exemplified for NAD(P)H:quinone oxidoreductase and glutathione-S-transferase (GST)A1, reflected in the protein level by an increase in GST enzyme activity. In a pilot human intervention study (29 healthy volunteers), daily consumption of 750 mL of CN-coffee for 4 weeks increased Nrf2 transcription in peripheral blood lymphocytes on average. However, the transcriptional response pattern of Nrf2/ARE-dependent genes showed substantial interindividual variations. The presence of SNPs in the Nrf2-promoter, reported recently, as well as the detection of GSTT1*0 (null) genotypes in the study collective strengthens the hypothesis that coffee acts as a modulator of Nrf2-dependent gene response in humans, but genetic polymorphisms play an important role in the individual response pattern.

Caffeine dose-dependently induces thermogenesis but restores ATP in HepG2 cells in culture.

Caffeine has been hypothesised as a thermogenic agent that might help to maintain a healthy body weight. Since very little is known about its actions on cellular energy metabolism, we investigated the effect of caffeine on mitochondrial oxidative phosphorylation, cellular energy supply and thermogenesis in HepG2 cells, and studied its action on fatty acid uptake and lipid accumulation in 3T3-L1 adipocytes at concentrations ranging from 30-1500 µM. In HepG2 cells, caffeine induced a depolarisation of the inner mitochondrial membrane, a feature of mitochondrial thermogenesis, both directly and after 24 h incubation. Increased concentrations of uncoupling protein-2 (UCP-2) also indicated a thermogenic activity of caffeine. Energy generating pathways, such as mitochondrial respiration, fatty acid oxidation and anaerobic lactate production, were attenuated by caffeine treatment. Nevertheless, HepG2 cells demonstrated a higher energy charge potential after exposure to caffeine that might result from energy restoration through attenuation of energy consuming pathways, as typically found in hibernating animals. In 3T3-L1 cells, in contrast, caffeine increased fatty acid uptake, but did not affect lipid accumulation. We provide evidence that caffeine stimulates thermogenesis but concomitantly causes energy restoration that may compensate enhanced energy expenditure.

Induction of antioxidative Nrf2 gene transcription by coffee in humans: depending on genotype?

The Nrf2/ARE pathway is a major cellular defense mechanism that prevents damage by reactive oxygen species through induction of antioxidative phase II enzymes. However, the activity of the Nrf2/ARE system is not uniform with variability in response presumed to be dependent on the Nrf2 genotype. We recently completed a pilot human coffee intervention trial with healthy humans, where large interindividual differences in the antioxidative response to the study coffee were examined. Here, we address the question whether differences in the modulation of Nrf2 gene transcription, assessed as an induction of Nrf2 gene transcription by Q-PCR, might be correlated with specific Nrf2 genotypes. To date, nine single nucleotide polymorphisms (SNPs) have been identified in the Nrf2 (NFE2L2) gene. Two of these, the -617C/A and -651G/A SNPs are located within the promoter region and have previously been reported to influence the activity of the Nrf2/ARE pathway by reducing Nrf2 transcriptional activity. Sequencing of the critical Nrf2 gene promoter region not only confirmed the existence of these SNPs within the participants of the trial at the expected frequency (33% carrying the -617C/A, 17% the -651G/A and 56% the -653A/G SNP) but also indicated reduced Nrf2 gene transcription associated with a normal diet if the SNPs at position -617, -651 or -653 were present. Of note, the data also indicated the study coffee increased Nrf2 gene transcription even in SNP carriers. This further highlights the relevance of genotype-dependent induction of Nrf2 gene transcription that appears to be largely influenced by dietary factors.

Dark roast coffee is more effective than light roast coffee in reducing body weight, and in restoring red blood cell vitamin E and glutathione concentrations in healthy volunteers.

Recent results from prospective cohort studies have shown that moderate coffee consumption is associated with a reduced risk for diabetes mellitus type II or Alzheimer's disease. Since reactive oxygen species (ROS) are believed to be involved in the pathogenesis of these diseases, antioxidants in coffee might contribute to this risk reduction. We aimed at elucidating whether a dark roast coffee beverage (CB) rich in N-methylpyridinium ions (NMP: 785 µmol/L) and low in chlorogenic acids (CGA: 523 µmol/L) has stronger antioxidant effects on human erythrocytes than a CB prepared from a light roast with opposite proportions (CGA: 4538 µmol/L; NMP: 56 µmol/L). Following a 2-wk wash out period, 500 mL of the respective CB was administered to 30 subjects daily for 4-wk. Blood and spot urine samples were collected at the beginning and at the end of each intervention. Intake of the dark roast CB most effectively improved the antioxidant status of erythrocytes: superoxide dismutase and glutathione peroxidase activity decreased by 5.8 and 15%, respectively, whereas tocopherol and total glutathione concentrations increased by 41 and 14%, respectively. Furthermore, administration of the NMP-rich CB led to a significant body weight reduction in pre-obese subjects, whereas the CGA-rich CB did not.

Antioxidant-rich coffee reduces DNA damage, elevates glutathione status and contributes to weight control: results from an intervention study.

Epidemiological and experimental evidence increasingly suggests coffee consumption to be correlated to prevention or delay of degenerative diseases connected with oxidative cellular stress. In an intervention study comprising 33 healthy volunteers, we examined DNA-protective and antioxidative effects exerted in vivo by daily ingestion of 750 mL of freshly brewed coffee rich in both green coffee bean constituents as well as roast products. The study design encompassed an initial 4 wk of wash-out, followed by 4 wk of coffee intake and 4 wk of second wash-out. At the start and after each study phase blood samples were taken to monitor biomarkers of oxidative stress response. In addition, body weight/composition and intake of energy/nutrients were recorded. In the coffee ingestion period, the primary endpoint, oxidative DNA damage as measured by the Comet assay (± FPG), was markedly reduced (p<0.001). Glutathione level (p<0.05) and GSR-activity (p<0.01) were elevated. Body weight (p<0.01)/body fat (p<0.05) and energy (p<0.001)/nutrient (p<0.001-0.05) intake were reduced. Our results allow to conclude that daily consumption of 3-4 cups of brew from a special Arabica coffee exerts health beneficial effects, as evidenced by reduced oxidative damage, body fat mass and energy/nutrient uptake.

Coffees rich in chlorogenic acid or N-methylpyridinium induce chemopreventive phase II-enzymes via the Nrf2/ARE pathway in vitro and in vivo.

Recently, the coffee constituents 5-O-caffeoylquinic acid (CGA) and N-methylpyridinium (NMP) were identified as inducers of the Nrf2/antioxidant-response element (ARE) detoxifying pathway under cell-culture condition. To study the impact of CGA and NMP on the Nrf2-activating properties of a complex coffee beverage, two different model coffees were generated by variation of the roasting conditions: a low-roast coffee rich in CGA and a heavy-roast low in CGA but containing high levels of NMP. Activation of the Nrf2/antioxidant-response element pathway was monitored in vitro and in vivo.

Antioxidant effectiveness of coffee extracts and selected constituents in cell-free systems and human colon cell lines.

SCOPE: Epidemiological studies suggest that coffee can reduce the risk of degenerative diseases such as diabetes type 2, cardiovascular disease and cancer. These beneficial effects have partly been attributed to the antioxidant activity of coffee. We determined composition and antioxidant potential of differentially roasted coffee extracts and investigated the impact of selected original constituents and roast products. METHODS AND RESULTS: Parameters studied were direct antioxidant activity (trolox equivalent antioxidant capacity/oxygen radical absorbing capacity), cellular reactive oxygen species (ROS) level, DNA damage and protein expression of NAD(P)H: quinone oxidoreductase, γ-glutamylcysteine ligase and glutathione reductase in HT-29/Caco-2 cells at 24-h incubation. All extracts showed distinct direct antioxidant activity: medium roasts>light roast AB1 (caffeoylquinic acid (CQA)-rich Arabica Brazil extract); dark roast AB2 (N-methylpyridinium (NMP)-rich Arabica Brazil extract), and diminished t-butylhydroperoxide-induced ROS level in HT-29 cells (AB2>medium roasts>AB1). NAD(P)H:quinone oxidoreductase 1 expression and γ-glutamylcysteine ligase expression were distinctly induced by AB1 and 5-CQA, but not by AB2 and NMP. 5-CQA and caffeic acid exhibited highest trolox equivalent antioxidant capacity/oxygen radical absorbing capacity values (5-CQA: 1.3/3.5 mM and caffeic acid: 1.3/3.9 mM trolox); ROS level was distinctly diminished by 5-CQA (≥3 µM), catechol (30 µM) and trigonelline (≥30 µM), whereas menadione-induced DNA damage in Caco-2 cells was reduced by NMP compounds (1-30 µM). CONCLUSION: The results emphasize that both original constituents and roast products contribute to the cellular antioxidant effectiveness of coffee.

Fate of 14C-acrylamide in roasted and ground coffee during storage.

Acrylamide (AA) is formed during heating of carbohydrate rich foods in the course of the Maillard reaction. AA has been classified as probably carcinogenic to humans. Storage experiments with roasted coffee have shown that AA levels decrease depending on storage time and temperature. In the present study the fate of AA lost during storage of roasted and ground (R&G) coffee was studied, using 14C-labeled AA as radiotracer. Radiolabel was measured in coffee brew, filter residue, and volatiles. In the brew, total (14)C-label decreased during storage of R&G coffee, while activity in the filter residue built up concomitantly. [2,3-14C]-AA (14C-AA) was the only 14C-related water extractable low molecular compound in the brew detected by radio-HPLC. No formation of volatile 14C-AA-related compounds was detected during storage and coffee brewing. Close to 90% of the radiolabel in the filter residue (spent R&G coffee, spent grounds) remained firmly bound to the matrix, largely resisting extraction by aqueous ammonia, ethyl acetate, chloroform, hexane, and sequential polyenzymatic digest. Furanthiols, which are abundant as aroma components in roasted coffee, have not been found to be involved in the formation of covalent AA adducts and thus do not contribute substantially to the decrease of AA during storage.

Studies on acrylamide levels in roasting, storage and brewing of coffee.

The content of acrylamide in coffee reaches a peak early in the roasting process, reflecting occurrence of both formation and destruction of acrylamide during roasting. Levels of acrylamide in the fully roasted product are a small fraction of the peak reached earlier. Glucose and moisture in green coffee do not show a significant correlation with acrylamide in roasted coffee. Pre-roasting levels of asparagine show a correlation only in Arabica coffee. The main factors affecting the level of acrylamide in roasted coffee appear to be the Arabica/Robusta ratio, with Robusta giving higher levels; time and degree of roast, with both shorter and lighter roasting at the edges of the normal roasting range giving higher levels; storage condition and time, with clear reduction at ambient storage. This storage reduction of acrylamide followed second order reaction kinetics with an activation energy of 73 KJ/mole. The acrylamide in roasted coffee is largely extracted into the brew and stable within usual time of consumption. As these four main factors also substantially affect the sensorial characteristics of the brew, and as modifications of the process have to comply with the consumer-accepted boundaries of taste profiles, only small effects on the acrylamide level are expected to be achievable.