The toxicology of cocoa and methylxanthines: a review of the literature

Preclinical Pharmacokinetic Study on Caffeine as an Excipient for Monoclonal Antibody Formulations

Caffeine is a novel excipient that effectively reduces viscosity of high concentration mAb formulations intended for subcutaneous (SQ) delivery. Two preclinical studies were conducted in rats to evaluate pharmacokinetic (PK) parameters of caffeine as well as its effects on the PK profile of a model mAb, namely ipilimumab. Results show that SQ absorption and elimination of caffeine was rapid, with the average Tmax of 0.4 h and T1/2 of 1.6 h, administered with or without ipilimumab. Furthermore, caffeine did not affect ipilimumab SQ PK profiles. Independent of caffeine concentration, ipilimumab serum T1/2 was between 2 and 3 days, Tmax was between 3 and 4 days and SQ bioavailability was about 64%. In addition, SQ injection of caffeine at different dose levels showed no irritation at the injection site or adverse effects. Results from the current PK studies warrant further development of caffeine as a viscosity reducing excipient for mAb SQ formulations.

Comparison of Gelatin Flavors for Oral Dosing of C57BL/6J and FVB/N Mice

Precise oral dosing in rodents is usually achieved by intragastric gavage. If performed incorrectly due to technical difficulties, inexperience, or animal resistance, oral gavage may have animal welfare implications such as esophageal and gastric rupture and aspiration. The stress that is induced by this procedure can also lead to confounding results. In several animal models, drug vehicles must be sugar-free, deliver drugs in a specific formulation, and sometimes supply water. Gelatin has all of these properties. The current study aimed to evaluate the use of gelatin vehicles with different sensory features as an alternative to oral gavage. We investigated the time taken by 2 different inbred mouse strains, FVB/N and C57BL/6J, to ingest sugar-free gelatin pellets of varying flavors. Results showed that FVB/N mice took more time to eat the unflavored, strawberry and diet-flavored gelatin pellets than did C57BL/6J mice. Both strains showed low preference for lemon flavor, with the same ingestion times after the second day. This study showed that the C57BL/6J mice are more likely to eat gelatin than are FVB/N mice, and that the 2 strains of mice show a lower preference for lemon flavoring as compared with other flavors. This method of voluntarily oral administration offers an alternative to gavage for studies that use oral dosing studies.

New framework for a non-animal approach adequately assures the safety of cosmetic ingredients - A case study on caffeine

This case study on the model substance caffeine demonstrates the viability of a 10-step read-across (RAX) framework in practice. New approach methodologies (NAM), including RAX and physiologically-based kinetic (PBK) modelling were used to assess the consumer safety of caffeine. Appropriate animal systemic toxicity data were used from the most relevant RAX analogue while assuming that no suitable animal toxicity data were available for caffeine. Based on structural similarities, three primary metabolites of the target chemical caffeine (theophylline, theobromine and paraxanthine) were selected as its most relevant analogues, to estimate a point of departure in order to support a next generation risk assessment (NGRA). On the basis of the pivotal mode of action (MOA) of caffeine and other methylxanthines, theophylline appeared to be the most potent and suitable analogue. A worst-case aggregate exposure assessment determined consumer exposure to caffeine from different sources, such as cosmetics and food/drinks. Using a PBK model to estimate human blood concentrations following exposure to caffeine, an acceptable Margin of Internal Exposure (MOIE) of 27-fold was derived on the basis of a RAX using theophylline animal data, which suggests that the NGRA approach for caffeine is sufficiently conservative to protect human health.

Sub-chronic and chronic toxicity evaluation of 7-methylxanthine: a new molecule for the treatment of myopia

Myopia (nearsightedness) is a vision disorder with a blurring of far objects, affect millions worldwide. 7-methylxanthine (7-MX) is a molecule that is presently under clinical investigation for the treatment of myopia. In the present study, we have investigated sub-chronic and chronic toxicity of 7-MX in comparison to other clinically used methylxanthines i.e., caffeine and theobromine as per OECD guidelines 408 and 452. 7-MX was administered orally for 90 days at three different doses of 250, 500, and 1000 mg/kg for sub-chronic toxicity evaluation, and at a limit dose of 1000 mg/kg in 180 days chronic toxicity evaluation in rats. In sub-chronic treatment, 7-MX showed no mortality and signs for toxicity in any group, whereas 10% and 40% mortality with signs for toxicity were observed in caffeine and theobromine treated groups, respectively. A similar, safety profile was observed with 7-MX in 180 days of chronic toxicity study. Further, to confirm any morphological changes in organs; ultrasound and X-rays analysis were performed and no changes in the size of organs, cyst formation, fluid retention, or crystal formation was observed. Thus, the repeated dose study of 7-MX for 180 days may augment the possibility of using 7-MX clinically for the safe and effective treatment of myopia.

Caffeine Consumption through Coffee: Content in the Beverage, Metabolism, Health Benefits and Risks

Caffeine (1,3,7-trimethylxanthine) is the most consumed psychoactive substance in the world, acting by means of antagonism to adenosine receptors, mainly A1 and A2A. Coffee is the main natural source of the alkaloid which is quite soluble and well extracted during the brew’s preparation. After consumption, caffeine is almost completely absorbed and extensively metabolized in the liver by phase I (cytochrome P450) enzymes, mainly CYP1A2, which appears to be polymorphically distributed in human populations. Paraxanthine is the major caffeine metabolite in plasma, while methylated xanthines and methyluric acids are the main metabolites excreted in urine. In addition to stimulating the central nervous system, caffeine exerts positive effects in the body, often in association with other substances, contributing to prevention of several chronic diseases. The potential adverse effects of caffeine have also been extensively studied in animal species and in humans. These aspects will be approached in the present review.

The Adenosine Receptor Antagonist, 7-Methylxanthine, Alters Emmetropizing Responses in Infant Macaques

Purpose

Previous studies suggest that the adenosine receptor antagonist, 7-methylxanthine (7-MX), retards myopia progression. Our aim was to determine whether 7-MX alters the compensating refractive changes produced by defocus in rhesus monkeys.

Methods

Starting at age 3 weeks, monkeys were reared with −3 diopter (D; n = 10; 7-MX −3D/pl) or +3D (n = 6; 7-MX +3D/pl) spectacles over their treated eyes and zero-powered lenses over their fellow eyes. In addition, they were given 100 mg/kg of 7-MX orally twice daily throughout the lens-rearing period (age 147 ± 4 days). Comparison data were obtained from lens-reared controls (−3D/pl, n = 17; +3D/pl, n = 9) and normal monkeys (n = 37) maintained on a standard diet. Refractive status, corneal power, and axial dimensions were assessed biweekly.

Results

The −3D/pl and +3D/pl lens-reared controls developed compensating myopic (−2.10 ± 1.07 D) and hyperopic anisometropias (+1.86 ± 0.54 D), respectively. While the 7-MX +3D/pl monkeys developed hyperopic anisometropias (+1.79 ± 1.11 D) that were similar to those observed in +3D/pl controls, the 7-MX −3D/pl animals did not consistently exhibit compensating myopia in their treated eyes and were on average isometropic (+0.35 ± 1.96 D). The median refractive errors for both eyes of the 7-MX −3D/pl (+5.47 D and +4.38 D) and 7-MX +3D/pl (+5.28 and +3.84 D) monkeys were significantly more hyperopic than that for normal monkeys (+2.47 D). These 7-MX–induced hyperopic ametropias were associated with shorter vitreous chambers and thicker choroids.

Conclusions

In primates, 7-MX reduced the axial myopia produced by hyperopic defocus, augmented hyperopic shifts in response to myopic defocus, and induced hyperopia in control eyes. The results suggest that 7-MX has therapeutic potential in efforts to slow myopia progression.

Bio-detheobromination of cocoa pod husks: reduction of ochratoxin A content without change in nutrient profile

Background

Utilization of cocoa pod husks (CPH) in animal feed is hindered by the presence of theobromine, which is variably toxic to animals. Treatment of this agro-waste to remove theobromine, while preserving its nutrient content, would allow beneficial use of the millions of metric tonnes discarded annually. The aim of this study was to assess the suitability of selected theobromine-degrading filamentous fungi for use as bio-tools in degradation of theobromine in CPH.

Results

The candidate fungi assessed in this study were an Aspergillus niger (AnTD) and three Talaromyces spp. (TmTD-1, TmTD-2, TvTD) isolates. All the fungi eliminated CPH theobromine, 0.15% w/w starting concentration, within 7 days of start of treatment, and were capable of degrading caffeine and theophylline. The fungi decreased CPH ochratoxin A content by 31–74%. Pectin was not detectable in fungus-treated CPH whereas parameters assessed for proximate composition were not affected.

Conclusions

The data provide ample evidence that the four isolates can be applied to CPH for the purpose of eliminating theobromine and decreasing ochratoxin A content without affecting nutrient profile. Comparatively, Talaromyces verruculosus TvTD was considered as most suitable for use as a bio-tool in detheobromination of CPH for animal feed.

Pharmacological potential of methylxanthines: Retrospective analysis and future expectations

Methylated xanthines (methylxanthines) are available from a significant number of different botanical species. They are ordinarily included in daily diet, in many extremely common beverages and foods. Caffeine, theophylline and theobromine are the main methylxanthines available from natural sources. The supposedly relatively low toxicity of methylxanthines, combined with the many beneficial effects that have been attributed to these compounds through time, generated a justified attention and a very prolific ground for dedicated scientific reports. Methylxanthines have been widely used as therapeutical tools, in an intriguing range of medicinal scopes. In fact, methylxanthines have been/were medically used as Central Nervous System stimulants, bronchodilators, coronary dilators, diuretics and anti-cancer adjuvant treatments. Other than these applications, methylxanthines have also been hinted to hold other beneficial health effects, namely regarding neurodegenerative diseases, cardioprotection, diabetes and fertility. However, it seems now consensual that toxicity concerns related to methylxanthine consumption and/or therapeutic use should not be dismissed. Taking all the knowledge and expectations on the potential of methylxanthines into account, we propose a systematic look at the past and future of methylxanthine pharmacologic applications, discussing all the promise and anticipating possible constraints. Anyways, methylxanthines will still substantiate considerable meaningful research and discussion for years to come.

Sustained consumption of cocoa-based dark chocolate enhances seizure-like events in the mouse hippocampus

While the consumption of caffeine and cocoa has been associated with a variety of health benefits to humans, some authors have proposed that excessive caffeine intake may increase the frequency of epileptic seizures in humans and reduce the efficiency of antiepileptic drugs. Little is known, however, about the proconvulsant potential of the sustained, excessive intake of cocoa on hippocampal neural circuits. Using the mouse as an experimental model, we examined the effects of the chronic consumption of food enriched in cocoa-based dark chocolate on motor and mood-related behaviours as well as on the excitability properties of hippocampal neurons. Cocoa food enrichment did not affect body weights or mood-related behaviours but rather promoted general locomotion and improved motor coordination. However, ex vivo electrophysiological analysis revealed a significant enhancement in seizure-like population spike bursting at the neurogenic dentate gyrus, which was paralleled by a significant reduction in the levels of GABA-α1 receptors thus suggesting that an excessive dietary intake of cocoa-enriched food might alter some of the synaptic elements involved in epileptogenesis. These data invite further multidisciplinary research aiming to elucidate the potential deleterious effects of chocolate abuse on behaviour and brain hyperexcitability.

Methylxanthines induce structural and functional alterations of the cardiac system in zebrafish embryos

Background

Zebrafish embryos are emerging as a model for pharmacological and toxicological studies. We used zebrafish embryos to study the general toxicity and cardiovascular effects of eight methylxanthines: aminophylline, caffeine, diprophylline, doxofylline, etophylline, 3-isobutyl-1-methylxanthine (IBMX), pentoxifylline and theophylline.

Methods

Microinjections of the eight methylxanthines were performed in 1-2 cell stage zebrafish embryos and the general toxicity and cardiovascular effects were analyzed at different time points. Embryotoxicity and teratogenicity were evaluated to understand the general toxicity of these compounds. Structural and functional alterations of the heart were evaluated to assess the cardiovascular effects.

Results

Our results showed different activity patterns of the methylxanthines drugs. Caffeine, IBMX, pentoxifylline and theophylline were highly embryotoxic and teratogenic; aminophylline, doxofylline and etophylline were embryotoxic and teratogenic only at higher doses, and diprophylline showed a minimal (<10%) embryotoxicity and teratogenicity. Most of these drugs induced structural alteration of the heart in 20-40% of the injected embryos with the maximum dose. This structural alteration was fatal with the embryos ultimately dying within 120 hpf. All the drugs induced a transient increase in heart rate at 48 hpf which returned to baseline within 96 hpf. This functional effect of methylxanthines showed similarity to the studies done in humans and other vertebrates.

Conclusion

Our results indicate the potential toxicity and teratogenicity of different methylxanthines in the embryos during embryonic development, the most sensitive period of life. Although interspecies differences need to be considered before drawing any conclusion, our study elucidated that a single exposure of methylxanthines at therapeutic range could induce cardiac dysfunction besides causing embryotoxicity and teratogenicity. Of all the drugs, diprophylline appeared to be safer, with lower degree of embryotoxicity, teratogenicity and cardiac toxicity as compared to other methylxanthines.

Electronic supplementary material

The online version of this article (10.1186/s40360-017-0179-9) contains supplementary material, which is available to authorized users.

Scientific Opinion on Flavouring Group Evaluation 49, Revision 1 (FGE.49Rev1): xanthine alkaloids from the priority list

Following a request from the European Commission, the EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF) was requested to deliver a scientific opinion on the safety assessment of the flavouring substances caffeine [FL-no: 16.016] and theobromine [FL-no: 16.032] in the Flavouring Group Evaluation 49, Revision 1. Consequent to the 2015 scientific opinion from the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) on the safety of caffeine from all dietary sources, the CEF Panel considered it inappropriate to evaluate the two substances through the Procedure. For caffeine, the Panel based its assessment on the safety threshold of 5.7 mg/kg body weight (bw) per day for adults, except pregnant/lactating women, and 3 mg/kg bw per day for children, adolescents, pregnant and lactating women, as established by the NDA Panel. The safety evaluation of theobromine takes into account that approximately 11% of an oral dose of caffeine is metabolised to theobromine and that both substances have a similar pharmacological profile. For the exposure assessment, a brand loyalty model was chosen. In this model, it was assumed that a consumer is exposed on a long-term basis to a specific category of food (i.e. non-alcoholic beverages), containing caffeine or theobromine at their respective maximum use levels. For the rest of the categories, normal use levels applied. Daily dietary exposure to caffeine and theobromine (excluding systemic exposure) added as a chemically defined flavouring substance ranged 0-2.3 and 0-0.4 mg/kg bw, respectively, across all population groups. The Panel concluded that caffeine [FL-no: 16.016] and theobromine [FL-no: 16.032] would not be expected to present safety concern based on their estimated levels of intake from their use as flavouring substances.

Structure-Bioactivity Relationships of Methylxanthines: Trying to Make Sense of All the Promises and the Drawbacks

Methylxanthines are a group of phytochemicals derived from the purine base xanthine and obtained from plant secondary metabolism. They are unobtrusively included in daily diet in common products as coffee, tea, energetic drinks, or chocolate. Caffeine is by far the most studied methylxanthine either in animal or epidemiologic studies. Theophylline and theobromine are other relevant methylxanthines also commonly available in the aforementioned sources. There are many disseminated myths about methylxanthines but there is increased scientific knowledge to discuss all the controversy and promise shown by these intriguing phytochemicals. In fact, many beneficial physiologic outcomes have been suggested for methylxanthines in areas as important and diverse as neurodegenerative and respiratory diseases, diabetes or cancer. However, there have always been toxicity concerns with methylxanthine (over)consumption and pharmacologic applications. Herein, we explore the structure-bioactivity relationships to bring light those enumerated effects. The potential shown by methylxanthines in such a wide range of conditions should substantiate many other scientific endeavors that may highlight their adequacy as adjuvant therapy agents and may contribute to the advent of functional foods. Newly designed targeted molecules based on methylxanthine structure may originate more specific and effective outcomes.

Macro- and Microelemental Composition and Toxicity of Unsweetened Natural Cocoa Powder in Sprague-Dawley Rats

Unsweetened natural cocoa powder (UNCP) is a pulverized high-grade powder of compressed solid blocks which remains after extraction. Little scientific data is available concerning its safety despite the presence of potential toxic elements. Elemental composition in UNCP was analyzed with ED-XRF spectroscopy. Single oral high dose toxicity study was conducted on adult male Sprague-Dawley rats (150 g) by the limit test method. One group received water and the test group 2000 mg/kg UNCP. All animals were observed for 14 days and then euthanized for haematological, biochemical, and histopathological examinations. Thirty-eight (38) elements were found in UNCP. There was an increase in HDL cholesterol (p < 0.05), reduction in LDL cholesterol (p > 0.05), alkaline phosphatase (p < 0.05), and creatinine levels, and slight increase in urea levels (p > 0.05). Haematological changes were not significant. Histopathological analysis showed no toxic effect on the heart, liver, kidney, lungs, testis, and spleen. Intestinal erosion was observed in the test group. UNCP appears to be relatively safe when taken as a single oral high dose of 2000 mg/kg b.w.t. in rats. Caution should however be exercised at high doses due to the high elemental content of copper and high possibility of intestinal lining erosion.

Theobromine increases NAD⁺/Sirt-1 activity and protects the kidney under diabetic conditions

Reduction in sirtuin 1 (Sirt-1) is associated with extracellular matrix (ECM) accumulation in the diabetic kidney. Theobromine may reduce kidney ECM accumulation in diabetic rats. In the current study, we aimed to unravel, under diabetic conditions, the mechanism of kidney ECM accumulation induced by a reduction in Sirt-1 and the effect of theobromine in these events. In vitro, we used immortalized human mesangial cells (iHMCs) exposed to high glucose (HG; 30 mM), with or without small interfering RNA for NOX4 and Sirt-1. In vivo, spontaneously hypertensive rats (SHR) were rendered diabetic by means of streptozotocin and studied after 12 wk. The effects of treatment with theobromine were investigated under both conditions. HG leads to a decrease in Sirt-1 activity and NAD(+) levels in iHMCs. Sirt-1 activity could be reestablished by treatment with NAD(+), silencing NOX4, and poly (ADP-ribose) polymerase-1 (PARP-1) blockade, or with theobromine. HG also leads to a low AMP/ATP ratio, acetylation of SMAD3, and increased collagen IV, which is prevented by theobromine. Sirt-1 or AMPK blockade abolished these effects of theobromine. In diabetic SHR, theobromine prevented increases in albuminuria and kidney collagen IV, reduced AMPK, elevated NADPH oxidase activity and PARP-1, and reduced NAD(+) levels and Sirt-1 activity. These results suggest that in diabetes mellitus, Sirt-1 activity is reduced by PARP-1 activation and NAD(+) depletion due to low AMPK, which increases NOX4 expression, leading to ECM accumulation mediated by transforming growth factor (TGF)-β1 signaling. It is suggested that Sirt-1 activation by theobromine may have therapeutic potential for diabetic nephropathy.

Psychopharmacology of theobromine in healthy volunteers

BACKGROUND

Theobromine, a methylxanthine related to caffeine and present in high levels in cocoa, may contribute to the appeal of chocolate. However, current evidence for this is limited.

OBJECTIVES

We conducted a within-subjects placebo-controlled study of a wide range of oral theobromine doses (250, 500, and 1,000 mg) using an active control dose of caffeine (200 mg) in 80 healthy participants.

RESULTS

Caffeine had the expected effects on mood including feelings of alertness and cardiovascular parameters. Theobromine responses differed according to dose; it showed limited subjective effects at 250 mg and negative mood effects at higher doses. It also dose-dependently increased heart rate. In secondary analyses, we also examined individual differences in the drug's effects in relation to genes related to their target receptors, but few associations were detected.

CONCLUSIONS

This study represents the highest dose of theobromine studied in humans. We conclude that theobromine at normal intake ranges may contribute to the positive effects of chocolate, but at higher intakes, effects become negative.

Crystal structures of human pyridoxal kinase in complex with the neurotoxins, ginkgotoxin and theophylline: insights into pyridoxal kinase inhibition

Several drugs and natural compounds are known to be highly neurotoxic, triggering epileptic convulsions or seizures, and causing headaches, agitations, as well as other neuronal symptoms. The neurotoxic effects of some of these compounds, including theophylline and ginkgotoxin, have been traced to their inhibitory activity against human pyridoxal kinase (hPL kinase), resulting in deficiency of the active cofactor form of vitamin B₆, pyridoxal 5'-phosphate (PLP). Pyridoxal (PL), an inactive form of vitamin B₆ is converted to PLP by PL kinase. PLP is the B₆ vitamer required as a cofactor for over 160 enzymatic activities essential in primary and secondary metabolism. We have performed structural and kinetic studies on hPL kinase with several potential inhibitors, including ginkgotoxin and theophylline. The structural studies show ginkgotoxin and theophylline bound at the substrate site, and are involved in similar protein interactions as the natural substrate, PL. Interestingly, the phosphorylated product of ginkgotoxin is also observed bound at the active site. This work provides insights into the molecular basis of hPL kinase inhibition and may provide a working hypothesis to quickly screen or identify neurotoxic drugs as potential hPL kinase inhibitors. Such adverse effects may be prevented by administration of an appropriate form of vitamin B₆, or provide clues of how to modify these drugs to help reduce their hPL kinase inhibitory effects.

Paradoxical and bidirectional drug effects

A paradoxical drug reaction constitutes an outcome that is opposite from the outcome that would be expected from the drug's known actions. There are three types: 1. A paradoxical response in a condition for which the drug is being explicitly prescribed. 2. Paradoxical precipitation of a condition for which the drug is indicated, when the drug is being used for an alternative indication. 3. Effects that are paradoxical in relation to an aspect of the pharmacology of the drug but unrelated to the usual indication. In bidirectional drug reactions, a drug may produce opposite effects, either in the same or different individuals, the effects usually being different from the expected beneficial effect. Paradoxical and bidirectional drug effects can sometimes be harnessed for benefit; some may be adverse. Such reactions arise in a wide variety of drug classes. Some are common; others are reported in single case reports. Paradoxical effects are often adverse, since they are opposite the direction of the expected effect. They may complicate the assessment of adverse drug reactions, pharmacovigilance, and clinical management. Bidirectional effects may be clinically useful or adverse. From a clinical toxicological perspective, altered pharmacokinetics or pharmacodynamics in overdose may exacerbate paradoxical and bidirectional effects. Certain antidotes have paradoxical attributes, complicating management. Apparent clinical paradoxical or bidirectional effects and reactions ensue when conflicts arise at different levels in self-regulating biological systems, as complexity increases from subcellular components, such as receptors, to cells, tissues, organs, and the whole individual. These may be incompletely understood. Mechanisms of such effects include different actions at the same receptor, owing to changes with time and downstream effects; stereochemical effects; multiple receptor targets with or without associated temporal effects; antibody-mediated reactions; three-dimensional architectural constraints; pharmacokinetic competing compartment effects; disruption and non-linear effects in oscillating systems, systemic overcompensation, and other higher-level feedback mechanisms and feedback response loops at multiple levels. Here we review and provide a compendium of multiple class effects and individual reactions, relevant mechanisms, and specific clinical toxicological considerations of antibiotics, immune modulators, antineoplastic drugs, and cardiovascular, CNS, dermal, endocrine, musculoskeletal, gastrointestinal, haematological, respiratory, and psychotropic agents.

Effects of 7-methylxanthine on the sclera in form deprivation myopia in guinea pigs

PURPOSE

The aim of this study was to determine the effect of the adenosine receptor antagonist 7-methylxanthine (7-MX) on form deprivation myopia in 3-week-old guinea pigs.

METHODS

Two groups of 3-week-old guinea pigs were subjected to monocular deprivation (MD) using a diffuser and fed either 7-MX (300 mg/kg body weight; n = 7) or vehicle control (saline at an equal volume to 7-MX; n = 7). A control group (n = 6) was not subjected to form deprivation. Ocular refraction, axial length and body weight were measured at the start and after 21 days. The thickness of the posterior sclera was measured by light microscopy and the collagen fibril diameter in the inner, middle and outer layers of the sclera was measured by electron microscopy.

RESULTS

In the vehicle control group, 21 days of MD produced significant amounts of myopia, axial elongation, thinning of the posterior sclera and thinning of the median collagen fibril diameter in the posterior sclera relative to the contralateral eyes. In the guinea pigs fed with 7-MX, however, form deprivation produced significantly less myopia and axial elongation compared with vehicle control animals. The 7-MX-treated animals exhibited a thickening of the posterior sclera in both the MD eye and the contralateral eye. In the 7-MX-treated animals, the median collagen fibril diameter in the posterior sclera was not reduced by form deprivation.

CONCLUSIONS

Treatment with 7-MX appears to not only decrease the amount of myopia by around 50% and eliminate the eye elongation induced by form deprivation in guinea pigs, but also to prevent form deprivation myopia-related scleral changes, such as thinning of the sclera and thinning of the collagen fibril diameter in the posterior sclera.

Pharmacokinetics and metabolism of natural methylxanthines in animal and man

Caffeine, theophylline, theobromine, and paraxanthine administered to animals and humans distribute in all body fluids and cross all biological membranes. They do not accumulate in organs or tissues and are extensively metabolized by the liver, with less than 2% of caffeine administered excreted unchanged in human urine. Dose-independent and dose-dependent pharmacokinetics of caffeine and other dimethylxanthines may be observed and explained by saturation of metabolic pathways and impaired elimination due to the immaturity of hepatic enzyme and liver diseases. While gender and menstrual cycle have little effect on their elimination, decreased clearance is seen in women using oral contraceptives and during pregnancy. Obesity, physical exercise, diseases, and particularly smoking and the interactions of drugs affect their elimination owing to either stimulation or inhibition of CYP1A2. Their metabolic pathways exhibit important quantitative and qualitative differences in animal species and man. Chronic ingestion or restriction of caffeine intake in man has a small effect on their disposition, but dietary constituents, including broccoli and herbal tea, as well as alcohol were shown to modify their plasma pharmacokinetics. Using molar ratios of metabolites in plasma and/or urine, phenotyping of various enzyme activities, such as cytochrome monooxygenases, N-acetylation, 8-hydroxylation, and xanthine oxidase, has become a valuable tool to identify polymorphisms and to understand individual variations and potential associations with health risks in epidemiological surveys.

Theobromine and the pharmacology of cocoa

The effects of theobromine in man are underresearched, possibly owing to the assumption that it is behaviourally inert. Toxicology research in animals may appear to provide alarming results, but these cannot be extrapolated to humans for a number of reasons. Domestic animals and animals used for racing competitions need to be guarded from chocolate and cocoa-containing foods, including foods containing cocoa husks. Research ought to include caffeine as a comparative agent, and underlying mechanisms need to be further explored. Of all constituents proposed to play a role in our liking for chocolate, caffeine is the most convincing, though a role for theobromine cannot be ruled out. Most other substances are unlikely to exude a psychopharmacological effect owing to extremely low concentrations or the inability to reach the blood-brain barrier, whilst chocolate craving and addiction need to be explained by means of a culturally determined ambivalence towards chocolate.

Comparison of the effects of dietary factors in the management and prophylaxis of migraine

Migraine is defined as a disorder characterized by intermittent headache episodes, accompanied with nausea, photophobia and/or phonophobia. Pharmacological therapy is in accordance with the severity of pain and may include acute, prophylactic and most commonly both approaches. The aim of the acute therapy is stopping or alleviating the attack or progression of the pain and, in case of a migraine attack that has started, lessening the pain. Preventive therapy aims to reduce attack frequency and severity. This study was designed to evaluate the effect of dietary factors in the management and prophylaxis of migraine in cases diagnosed as having migraine disorder according to the 2003-IHS criteria. Fifty consecutive Turkish patients (13 men, 37 women) with diagnosis of migraine were randomly divided into two groups for treatment protocols with the written approval of the ethics committee. The cases in the first group (K) were treated with metoprolol, vitamin B(2) (riboflavin), and naproxen sodium just at the aura or at the beginning of the attacks. The cases in the second group (D) were also supplied with a comprehensive dietary list arranged by our algology clinic in addition to the same medication protocol. There were no demographic differences between the cases (P > 0.05). VAS scores were lower in group D than group K (P < 0.01), and also the migraine attack frequencies and monthly amounts of analgesic consumed amounts were also statistically significantly less. It was concluded that beta-blocker and riboflavin therapy supplemented with a convenient diet with appropriate alternatives in patients with migraine disorder was associated with statistically significant decreases in headache frequency, intensity, duration and medication intake.

Identification of paraxanthine as the most potent caffeine-derived inhibitor of connective tissue growth factor expression in liver parenchymal cells

BACKGROUND

Recently, we identified hepatocytes as the major cellular source of profibrogenic connective tissue growth factor (CTGF/CCN2) in the liver. Based on reports of a hepatoprotective effect of coffee consumption, we were the first to provide evidence that caffeine suppresses transforming growth factor (TGF)-beta dependent and -independent CTGF expression in hepatocytes in vitro and in vivo, thus suggesting this xanthine-alkaloid as a potential therapeutic agent.

AIM

This study aims at comparing the inhibitory capacities of caffeine and its three demethylated derivates paraxanthine, theophylline and theobromine on CTGF expression in hepatocytes and hepatic stellate cells (HSC).

RESULTS

Our data suggest paraxanthine as the most important pharmacological repressor of hepatocellular CTGF expression among the caffeine-derived metabolic methylxanthines with an inhibitory dosage (ID)50 of 1.15 mM, i.e. 3.84-fold lower than what is observed for caffeine. In addition, paraxanthine displayed the least cell toxicity as proven by the water-soluble tetrazolium-1 cell vitality assay. However, caffeine or any of the metabolites did not inhibit CTGF expression in HSC. At the toxicological threshold concentration of 1 mM for paraxanthine, we observed an inhibition of hepatocellular CTGF synthesis by 44%, which was strongly reverted in the presence of the specific competitive cyclic adenosine monophosphate inhibitor Rp-adenosine 3',5-cyclic monophosphorothioate triethylammonium salt. Furthermore, CTGF protein expression induced by various concentrations of TGF-beta (0.13-1 ng/ml) is still reduced by, on average, 27%/45% in the presence of paraxanthine (1.25 mM/2.5 mM).

CONCLUSION

Our data provide an evidence-based suggestion of the caffeine-derived primary metabolite paraxanthine as a potentially powerful antifibrotic drug by its inhibitory effect on (hepatocellular) CTGF synthesis.

Systemic 7-methylxanthine in retarding axial eye growth and myopia progression: a 36-month pilot study

The adenosine antagonist 7-methylxanthine (7-mx) works against myopia in animal models. In a clinical trial, 68 myopic children (mean age 11.3 years) received either placebo or 7-mx tablets for 12 months. All participants subsequently received 7-mx for another 12 months, after which treatment was stopped. Axial length was measured with Zeiss IOL-Master and cycloplegic refraction with Nikon Retinomax at -6, 0, 12, 24, and 36 months. Axial growth was reduced among children treated with 7-mx for 24 months compared with those only treated for the last 12 months. Myopia progression and axial eye growth slowed down in periods with 7-mx treatment, but when the treatment was stopped, both myopia progression and axial eye growth continued with invariable speed. The results indicate that 7-mx reduces eye elongation and myopia progression in childhood myopia. The treatment is safe and without side effects and may be continued until 18-20 years of age when myopia progression normally stops.

Coffee, tea, caffeine and risk of breast cancer: a 22-year follow-up

The relation between consumption of coffee, tea and caffeine and risk of breast cancer remains unsettled. We examined data from a large, long-term cohort study to evaluate whether high intake of coffee and caffeine is associated with increased risk of breast cancer. This was a prospective cohort study with 85,987 female participants in the Nurses' Health Study. Consumption of coffee, tea and caffeine consumption was assessed in 1980, 1984, 1986, 1990, 1994, 1998 and the follow-up continued through 2002. We documented 5,272 cases of invasive breast cancer during 1,715,230 person-years. The multivariate relative risks (RRs) of breast cancer across categories of caffeinated coffee consumption were: 1.0 for <1 cup/month (reference category), 1.01 (95% confidence interval: 0.92-1.12) for 1 month to 4.9 week, 0.92 (0.84-1.01) for 5 week to 1.9 days, 0.93 (0.85-1.02) for 2-3.9 days, 0.92 (0.82-1.03) for >or=4 cups per day (p for trend = 0.14). Intakes of tea and decaffeinated coffee were also not significantly associated with risk of breast cancer. RRs (95% CI) for increasing quintiles of caffeine intake were 1.00, 0.98 (0.90-1.07), 0.92 (0.84-1.00), 0.94 (0.87-1.03) and 0.93 (0.85-1.01) (p for trend = 0.06). A significant inverse association of caffeine intake with breast cancers was observed among postmenopausal women; for the highest quintile of intake compared to the lowest RR 0.88 (95% CI = 0.79-0.97, p for trend = 0.03). We observed no substantial association between caffeinated and decaffeinated coffee and tea consumption and risk of breast cancer in the overall cohort. However, our results suggested a weak inverse association between caffeine-containing beverages and risk of postmenopausal breast cancer.

Mood and cognitive performance effects of "energy" drink constituents: caffeine, glucose and carbonation

Three studies using healthy volunteers (n = 271) investigated the effects of caffeine, carbohydrates and carbonation in functional "energy" drinks (EDs) with the aim of determining their benefit in every-day life. The results showed caffeine to be the main ED constituent responsible for the effects found, with possible minor, relatively weak effects of carbohydrates. EDs were found to improve and/or maintain mood and performance during fatiguing and cognitively demanding tasks relative to placebo. In terms of absolute values, EDs maintained levels of arousal compared to a deterioration in arousal where placebo was consumed. These effects were found in caffeine-deprived participants, and so may be largely due to "withdrawal reversal". There were only minor differences in the effects of water vs. "sensory-matched" placebo, supporting previous findings indicating that the type of placebo does not alter the conclusions drawn about the effects of the full ED. Finally, carbonation had various effects on mood, some of which were present immediately following consumption, others were consistent with slower absorption of caffeine (and possibly carbohydrates) from carbonated drinks.

Methylxanthines are the psycho-pharmacologically active constituents of chocolate

RATIONALE

Liking, cravings and addiction for chocolate ("chocoholism") are often explained through the presence of pharmacologically active compounds. However, mere "presence" does not guarantee psycho-activity.

OBJECTIVES

Two double-blind, placebo-controlled studies measured the effects on cognitive performance and mood of the amounts of cocoa powder and methylxanthines found in a 50 g bar of dark chocolate.

METHODS

In study 1, participants ( n=20) completed a test battery once before and twice after treatment administration. Treatments included 11.6 g cocoa powder and a caffeine and theobromine combination (19 and 250 mg, respectively). Study 2 ( n=22) comprised three post-treatment test batteries and investigated the effects of "milk" and "dark" chocolate levels of these methylxanthines. The test battery consisted of a long duration simple reaction time task, a rapid visual information processing task, and a mood questionnaire.

RESULTS

Identical improvements on the mood construct "energetic arousal" and cognitive function were found for cocoa powder and the caffeine+theobromine combination versus placebo. In chocolate, both "milk chocolate" and "dark chocolate" methylxanthine doses improved cognitive function compared with "white chocolate". The effects of white chocolate did not differ significantly from those of water.

CONCLUSIONS

A normal portion of chocolate exhibits psychopharmacological activity. The identical profile of effects exerted by cocoa powder and its methylxanthine constituents shows this activity to be confined to the combination of caffeine and theobromine. Methylxanthines may contribute to the popularity of chocolate; however, other attributes are probably much more important in determining chocolate's special appeal and in explaining related self-reports of chocolate cravings and "chocoholism".

The epidemiology of tea consumption and colorectal cancer incidence

This manuscript provides a brief synopsis of 30 studies aimed at examining tea consumption as a factor in the incidence of colon and rectal cancers. The 30 papers examine populations in 12 countries and provide data on consumption of both black and green tea. These studies do not provide consistent evidence to support the theory from animal studies and basic research that tea is a potent chemopreventive agent. Details of the studies are presented, and the potential impact of measurement error, publication bias, the form of tea consumed, the appropriateness of the outcomes studied and the adjustment of confounders related to both tea consumption and risk of colorectal cancer or polyps in various countries are explored. In general, the data are not more consistent for green than for black tea. Particularly with green tea, the doses consumed do get into a perceived protective range in a significant subset of the population. A negative association is stronger in observational epidemiologic studies of rectal cancer than in colon cancer. There is no consistent adjustment for important potential confounders of any tea relationship, such as coffee and alcohol consumption and physical activity levels. Finally, the assessment of tea in most of these studies was based on a single question and therefore may have significant measurement error compared with more recent studies specifically aimed at assessing tea consumption.

Food craving and food "addiction": a critical review of the evidence from a biopsychosocial perspective

Although certain commonalities exist between eating and drug use (mood effects, external cue-control of appetites, reinforcement, etc. ), it is argued that the vast majority of cases of (self-reported) food craving and food "addiction" should not be viewed as addictive behavior. An explanation is proposed that instead gives a prominent role to the psychological processes of ambivalence and attribution, operating together with normal mechanisms of appetite control, the hedonic effects of certain foods, and socially and culturally determined perceptions of appropriate intakes and uses of those foods. Ambivalence (e.g., "nice but naughty") about foods such as chocolate arises from the attitude that it is highly palatable but should be eaten with restraint. Attempts to restrict intake, however, cause the desire for chocolate to become more salient, an experience that is then labelled as a craving. This, together with a need to provide a reason for why resisting eating chocolate is difficult and sometimes fails, can, in turn, lead the individual to an explanation in terms of addiction (e.g., "chocoholism"). Moreishness ("causing a desire for more") occurs during, rather than preceding, an eating episode, and is experienced when the eater attempts to limit consumption before appetite for the food has been sated.

Chocolate: food or drug?

Although addictive behavior is generally associated with drug and alcohol abuse or compulsive sexual activity, chocolate may evoke similar psychopharmacologic and behavioral reactions in susceptible persons. A review of the literature on chocolate cravings indicates that the hedonic appeal of chocolate (fat, sugar, texture, and aroma) is likely to be a predominant factor in such cravings. Other characteristics of chocolate, however, may be equally as important contributors to the phenomena of chocolate cravings. Chocolate may be used by some as a form of self-medication for dietary deficiencies (eg, magnesium) or to balance low levels of neurotransmitters involved in the regulation of mood, food intake, and compulsive behaviors (eg, serotonin and dopamine). Chocolate cravings are often episodic and fluctuate with hormonal changes just before and during the menses, which suggests a hormonal link and confirms the assumed gender-specific nature of chocolate cravings. Chocolate contains several biologically active constituents (methylxanthines, biogenic amines, and cannabinoid-like fatty acids), all of which potentially cause abnormal behaviors and psychological sensations that parallel those of other addictive substances. Most likely, a combination of chocolate's sensory characteristics, nutrient composition, and psychoactive ingredients, compounded with monthly hormonal fluctuations and mood swings among women, will ultimately form the model of chocolate cravings. Dietetics professionals must be aware that chocolate cravings are real. The psychopharmacologic and chemosensory effects of chocolate must be considered when formulating recommendations for overall healthful eating and for treatment of nutritionally related health issues.

A double-blind provocative study of chocolate as a trigger of headache

A provocative double-blind study of headache was performed using chocolate as the active agent and carob as the placebo. The chocolate and carob samples were formulated to duplicate products used in an earlier study (1) in which strong differential effects between the ability of chocolate and carob to trigger headache in migraine were shown. Sixty-three women with chronic headache (50% migraine, 37.5% tension-type, 12.5% combined migraine and tension-type) participated in the study. After 2 weeks of following a diet that restricted vasoactive amine-rich foods, each subject underwent double-blinded provocative trials with two samples of chocolate and two of carob presented in random order. Diaries were maintained by the subjects throughout the study, monitoring diet and headache. The results demonstrated that chocolate was not more likely to provoke headache than was carob in any of the headache diagnostic groups (chi2(2)=0.36, p=0.83). Interestingly, these results were independent of subjects' beliefs regarding the role of chocolate in the instigation of headache (chi2(1)=0.73, p=0.39). Headache diagnosis and the concomitant use of additional vasoactive amine-containing foods were also not associated with chocolate acting as a headache trigger. Thus, contrary to the commonly held belief of patients and physicians, chocolate does not appear to play a significant role in triggering headaches in typical migraine, tension-type, or combined headache sufferers.

Discriminative stimulus and subjective effects of theobromine and caffeine in humans

Theobromine versus placebo discrimination and caffeine versus placebo discrimination were studied in two consecutive experiments in seven volunteers who abstained from methylxanthines. Daily sessions involved PO double-blind ingestion of two sets of capsules sequentially, one of which contained drug and the other placebo. Subjects attempted to identify, and were later informed, which set of capsules contained the drug. In each experiment subjects were exposed to progressively lower doses. Five subjects acquired the theobromine discrimination; the lowest dose discriminated ranged from 100 to 560 mg. All seven subjects acquired the caffeine discrimination; the lowest dose discriminated ranged from 1.8 to 178 mg. A final experiment evaluated subjective effect ratings following 560 mg theobromine, 178 mg caffeine and placebo, which were administered double-blind in capsules once daily, five times each in mixed sequence. Caffeine produced changes in both group and individual ratings (e.g. increased well-being, energy, social disposition and alert). Theobromine did not produce changes in group ratings but changed ratings in some subjects. Across subjects, sensitivity to caffeine discriminative effects in the discrimination experiment correlated significantly with the number and magnitude of caffeine subjective effects in the final experiment. This study documents modest discriminative effects of theobromine in humans, but the basis of the discrimination is unclear. This study suggests that commonly consumed cocoa products contain behaviorally active doses of caffeine and possibly theobromine.

Potential genotoxic, mutagenic and antimutagenic effects of coffee: a review

Coffee and caffeine are mutagenic to bacteria and fungi, and in high concentrations they are also mutagenic to mammalian cells in culture. However, the mutagenic effects of coffee disappear when bacteria or mammalian cells are cultured in the presence of liver extracts which contain detoxifying enzymes. In vivo, coffee and caffeine are devoid of mutagenic effects. Coffee and caffeine are able to interact with many other mutagens and their effects are synergistic with X-rays, ultraviolet light and some chemical agents. Caffeine seems to potentiate rather than to induce chromosomal aberrations and also to transform sublethal damage of mutagenic agents into lethal damage. Conversely, coffee and caffeine are also able to inhibit the mutagenic effects of numerous chemicals. These antimutagenic effects depend on the time of administration of coffee as compared to the acting time of the mutagenic agent. In that case, caffeine seems to be able to restore the normal cycle of mitosis and phosphorylation in irradiated cells. Finally, the potential genotoxic and mutagenic effects of the most important constituents of coffee are reviewed. Mutagenicity of caffeine is mainly attributed to chemically reactive components such as aliphatic dicarbonyls. The latter compounds, formed during the roasting process, are mutagenic to bacteria but less to mammalian cells. Hydrogen peroxide is not very active but seems to considerably enhance mutagenic properties of methylglyoxal. Phenolic compounds are not mutagenic but rather anticarcinogenic. Benzopyrene and mutagens formed during pyrolysis are not mutagenic whereas roasting of coffee beans at high temperature generates mutagenic heterocyclic amines. In conclusion, the mutagenic potential of coffee and caffeine has been demonstrated in lower organisms, but usually at doses several orders of magnitude greater than the estimated lethal dose for caffeine in humans. Therefore, the chances of coffee and caffeine consumption in moderate to normal amounts to induce mutagenic effects in humans are almost nonexistent.

Caffeine does not increase synthesis of heat shock proteins in rat embryos

Caffeine exposure in utero in rats is known to result in intrauterine growth retardation and lowered birth weight as well as changes to behaviour and brain biochemistry. We have investigated whether caffeine's embryotoxicity is a result of the events associated with increased hsp synthesis, i.e., disruption to normal protein synthesis. Caffeine (30 mg/kg) was administered orally to pregnant rats as single or repeated doses. Embryos were removed 3 h after dosing on gestation day (GD) 9, 10, 11 and 12 and total embryonic protein and RNA analysed. There was no change in the mRNA or protein levels of hsp 88, 71/73, and 25 after acute or chronic treatment. To separate the direct effect of caffeine from those mediated through the mother, whole rat embryo culture was used. Caffeine (50 micrograms/ml) for 90 min did not increase hsp 88, 73 or 25 mRNA levels in 9.5, 10.5 and 11.5 GD cultured embryos. We conclude that in vivo or in vitro treatment of 9-12 GD rat embryos with moderate to high doses of caffeine does not increase the synthesis of the major mammalian hsps. Hence, hsp induction is unlikely to play a role in the embryotoxic actions of caffeine.

Chocolate craving and liking

Liking and craving for chocolate and related substances were surveyed in a sample of University of Pennsylvania undergraduates (n = 249) and their parents (n = 319). Chocolate was highly liked in all groups, with a stronger liking by females. Chocolate is the most craved food among females, and is craved by almost half of the female sample (in both age groups). Although this craving is related to a sweet craving, it cannot be accounted for as a craving for sweets. About half of the female cravers show a very well defined craving peak for chocolate in the perimenstrual period, beginning from a few days before the onset of menses and extending into the first few days of menses. There is not a significant relation in chocolate craving or liking between parents and their children. The current motivation for chocolate preference seems to be primarily, if not entirely, sensory. Liking for chocolate correlates significantly with liking for sweets and white chocolate. The liking for the sensory properties could originate in innate or acquired liking based on the sweetness, texture and aroma of chocolate, or it could be based in part on interactions between the postingestional effects of chocolate and a person's state (e.g., mood, hormone levels). Based on correlational data, we find little evidence for a relation between addiction to chocolate or the pharmacological (e.g., xanthine-based) effects of chocolate and the liking for chocolate.

Chronic toxicity/carcinogenicity studies of cocoa powder in rats

Cocoa powder (CP) was fed at levels of 0.0 (control), 1.5, 3.5 and 5.0% for 104 wk to male and female Sprague-Dawley rats derived from the F3b generation of a multigeneration study using the same CP diets. Initial methylxanthine intake was high in all treatment groups, but steadily declined until wk 26. The high dose level provided a mean methylxanthine intake of approximately 57 mg/kg body weight/day for males and 74 mg/kg body weight/day for females from wk 26 to wk 104 of the study. Compared with controls, the historical trend of methylxanthine-associated growth stimulation was evident in rats consuming diets containing 1.5% CP, while body weight was reduced in rats consuming diets containing 3.5 and 5.0% CP. Survival rates were similar in control and CP-fed rats. No evidence of treatment-related clinical disease or ocular effects was noted. An increased incidence of bilateral testicular atrophy and aspermatogenesis was present in males consuming diets containing 5.0% CP. Non-suppurative myocarditis and interstitial fibrosis of the heart were also increased in incidence in both sexes receiving diets containing 5.0% CP. The overall incidences of both pelvic dilatation and renal pelvic microcalculi were increased in most treatment groups. Although there was no difference in the incidence of benign mammary gland fibroadenomas in female rats between the control group and any CP-fed group, a marginally significant (P = 0.04) trend test was apparent. The significance of this finding is doubtful, since the incidence of this lesion in the highest dose group was well within the historical control range for this strain of rats. No evidence of carcinogenicity from dietary CP was found in either sex.

Tobacco smoking, coffee, cocoa and tea consumption in relation to mortality from urinary bladder cancer in Italy

This paper examines changes in mortality from urinary bladder cancer in Italy during the years 1950-81 in relation to changes in smoking habits and in coffee, cocoa and tea consumption. The authors found that, in both sexes and for all ages, mortality has been increasing throughout this period, although the rates and relative increase have consistently been much lower and more gradual for women than for men. From the analysis of age-cohort-period variation it seems that bladder cancer mortality can also be influenced by changes in smoking habit patterns and by variation in the quality of diagnoses. The increase in death risk for both sexes in Italy up to cohorts born around 1905-10 can be related to occupational exposures and to high-tar-content tobacco smoking, whereas the tendency for mortality rates to stabilize and decline in cohorts born after 1910 were influenced by changes from high-tar-content and no-filter cigarettes to low-tar-content and filter cigarettes and by prevention measures taken in at-risk working environments. The consumption of coffee, cocoa and tea does not seem to be related to the increase in bladder cancer risk in Italy.