Role Of Caffeine Research Articles

Acute hemodynamic effects of caffeine administration in premature infants

Administration of caffeine citrate (caffeine) has been a central component of the treatment of apnea of prematurity. However, given its multiple pharmacologic effects, caffeine might be expected to produce hemodynamic changes in heart rate, stroke volume, cardiac output and vascular resistance. In this prospective observational study, we report the hemodynamic effects of intravenous caffeine administration in a population of premature infants who received caffeine to correct or prevent apnea of prematurity. Hemodynamic effects of caffeine were determined in 31 infants. Stroke volume was measured via echocardiogram, using velocity time integral at the aortic root diameter. Statistically univariate analyses were performed parametrically using paired t-test and nonparametrically (sign test). Multivariate linear regression models were used to identify subgroup covariate effects. After intravenous caffeine, cardiac index increased in 31 of 31 trials, by an average of 14.6+/-16.3% (s.d.); stroke volume increased in 24 of 31 trials, by 7.8+/-12.2%; heart rate increased in 28 of 31 trials by 7.7+/-7.2 beats per min; and blood pressure increased in 25 of 31 trials, by 4.1+/-5.8 mm Hg (all P<0.001). Multivariate linear regression revealed no significant effect of dose, birth weight, gestational age or postnatal age. Intravenous caffeine consistently increases cardiac output and blood pressure in relatively stable premature infants, when given to treat or prevent apnea of prematurity. We speculate that there may be a role for caffeine in the hemodynamic treatment of hypotensive/hypoperfused infants.

Assessing caffeine exposure in pregnant women

Studies on the effects of caffeine on health, while numerous, have produced inconsistent results. One of the most uncertain and controversial effects is on pregnancy outcome. Studies have produced conflicting results due to a number of methodological variations. The major challenge is the accurate assessment of caffeine intake. The aim of the present study was to explore different methods of assessing caffeine exposure in pregnant women. Twenty-four healthy pregnant women from the UK city of Leeds completed both a detailed questionnaire, the caffeine assessment tool (CAT) designed specifically to assess caffeine intake and a prospective 3 d food and drink diary. The women also provided nine saliva samples over two consecutive days for estimation of caffeine and a metabolite (paraxanthine). Caffeine intakes from the CAT and diary showed adequate agreement (intra-class correlation coefficient of 0.5). For saliva caffeine and paraxanthine measures, the between-sample variation (within the same woman) was greater than between-woman and between-day variation. However, there was still adequate agreement between these measures and the CAT. The CAT is a valuable tool that is now being used in a large prospective study investigating caffeine's role in pregnancy outcome.

Association between coffee consumption and markers of inflammation and cardiovascular function during mental stress

Coffee is widely consumed in the Western diet and therefore has important implications for public health. Research findings pertaining to the effects of coffee consumption on cardiovascular health are conflicting, and the role of caffeine is not clear. To examine the relationship between coffee intake, inflammation and cardiovascular function at baseline and during mental stress, both cross-sectionally and after a 4-week period of withdrawal of coffee during which intake of caffeine was maintained. Eighty-five healthy, non-smoking men with varying coffee-drinking habits were recruited. Blood pressure, heart rate, and markers of inflammation [C-reactive protein (CRP), von Willebrand factor antigen (vWF)], were measured at baseline and during mental stress. These measures were repeated after a 4-week period of withdrawal of coffee, during which intake of caffeine was maintained. Habitual levels of coffee and caffeine consumption were assessed from a self-reported questionnaire, and saliva samples for the analysis of caffeine concentrations were collected regularly throughout the period of withdrawal, to confirm compliance. Multiple linear regression analysis of pre-withdrawal data, adjusted for age, body mass index and intake of tea, red wine, fruit, vegetables, oily fish and dietary supplements revealed that coffee consumption was positively related to baseline systolic blood pressure, and increased heart rate and vWF responses to mental stress. Four weeks after withdrawal of coffee, the heightened vWF and heart rate responses to stress in habitual coffee drinkers persisted, whereas baseline systolic blood pressure had decreased. Total caffeine intake was unrelated to any measures of physiological function. Habitual coffee consumption is associated with heightened acute vascular inflammatory responses to mental stress, although these effects are not affected by short-term abstinence from coffee. These findings suggest that the relationship between coffee and markers of cardiovascular risk may be explained by residual or unmeasured confounding factors.

Modulation of neuronal [Ca2+]i by caffeine is altered with aging

Voltage-dependent calcium channels play an important role in controlling many neuronal processes such as neuronal excitability and synaptic transmission. Any slight alteration in intracellular calcium concentration ([Ca2+]i) can have a considerable impact on various neuronal functions. The effects of caffeine on [Ca2+]i were studied in CA1 hippocampal neurons of young (2 months) and old (24 months) C57BL mice. Fura 2-AM fluorescence photometry was used to measure [Ca2+]i in the presence and absence of caffeine (100μM) in response to KCl (26mM) application. Caffeine enhanced the peak [Ca2+]i as compared to control solution in young mice (control: 325±8nM, caffeine: 402±10nM), but had no effect on the peak [Ca2+]i in old mice (control: 222±6nM, caffeine: 223±7nM). These results indicate that caffeine can impact neuronal functions through the modification of [Ca2+]i. The lack of caffeine-induced modulation of [Ca2+]i in old mice suggests that this role of caffeine has been compromised with aging.

Coffee Consumption and Risk of Type 2 Diabetes Mellitus

Coffee intake may be associated with reduced risk of type 2 diabetes mellitus because of minerals, phytochemicals, and antioxidants in coffee, but the role of caffeine is unclear. Our objective was to examine the association between total, caffeinated, and decaffeinated coffee intake, as assessed by food frequency questionnaire at baseline, and risk of incident type 2 diabetes mellitus. This prospective analysis of the Iowa Women's Health Study (1986-1997) included 28 812 postmenopausal women free of diabetes and cardiovascular disease in the general community. The main outcome measure was incident type 2 diabetes mellitus as determined by mailed questionnaire. Coffee intake was categorized as 0, less than 1, 1 to 3, 4 to 5, and 6 or more cups per day. During 11 years of follow-up, there were 1418 incident cases of diabetes. Relative risks (RRs) were adjusted for a variety of demographic, adiposity, and lifestyle measures. Compared with women who reported 0 cups of coffee per day, women who consumed 6 or more cups per day had a 22% lower risk (RR = 0.78; 95% confidence interval [CI], 0.61-1.01) of diabetes (P for linear trend across categories, .06). This association appeared to be largely explained by decaffeinated coffee (RR = 0.67; 95% CI, 0.42-1.08; P for trend, .006) rather than regular coffee (RR = 0.79; 95% CI, 0.59-1.05; P for trend, .90). Intake of magnesium and phytate did not explain these associations. Intakes of caffeine from all sources was not associated with risk of diabetes. Coffee intake, especially decaffeinated, was inversely associated with risk of type 2 diabetes mellitus in this cohort of postmenopausal women.

Caffeine-mediated enhancement of glucocorticoid receptor activity in human osteoblastic cells

Caffeine-containing beverage consumption has been reported to be associated with an increased risk for osteoporosis. Since the glucocorticoid receptor (GR) is a major factor in the induction of osteoporosis we analyzed whether caffeine may act via altering GR function. Applying a reporter gene assay we provide evidence that caffeine drastically amplifies GR transcriptional activity in human osteoblastic cells. Substances that increase the intracellular cyclic AMP-concentration also strengthen the transactivity of the GR and coincubation with caffeine further reinforces this potentiation, indicating that caffeine-mediated enhancement of GR transcriptional function is due to the inhibitory activity of caffeine on the cyclic AMP phosphodiesterase. Our data suggest evidence for a hitherto unrecognized crosstalk between caffeine-modulated signalling and GR-initiated gene expression in human osteoblastic cells and could provide the molecular basis for the role of caffeine in osteoporosis.

The Role of Ruthenium Red as a Partial Agonist in Caffeine-Induced Neurotoxicity in Cerebellar Granular Cell Culture of Rats

Caffeine is widely spread and well known as a mild stimulant of the central nervous system. The present study tested the role of caffeine and Ruthenium red on the intact neuronal cells alone and Ruthenium red in caffeine-induced neurotoxicity. One-day-old newborn rats were used to obtain cerebellar cell cultures. Caffeine at a concentration of 1 mM was found to be most toxic. Dead cell scores were 5.9 ± 0.8 for control, and 56.2 ± 3.4 for caffeine (p < .00l). Ruthenium red alone has also caused the reduction in neuronal cell number 36.1 ± 4.5 for 10−5 and 47 ± 2.7 for 10−6 M concentrations (p < .001 for both). Interestingly Ruthenium red used in caffeine-induced neurotoxicity has partly diminished the number of dead cells 28.7 ± 3.2 for 10−5 and 23.8 ± 2.27 for 10−6 M concentrations (p < .001 for both). The results suggest that both Ruthenium red and caffeine are neurotoxic alone but, in combination, the neurotoxicity may be reduced through partial agonistic action.

Effects of Long-Term Administration of Caffeine on Fat Storage in Ovariectomized Rats

It is well known that obesity occurs in women with climacteric disorders. The aim of this study was to examine whether caffeine prevents obesity and bone loss in ovariectomized rats (ovx). Eight-week-old female Wistar rat were assigned to 4 groups: a sham-operated group fed the control diet (CE-2); an ovx-c group fed the control diet; an ovx-caf 0.15% group fed the control diet containing 1.5 g/kg of caffeine; and an ovx-caf 0.3% group fed the control diet containing 3 g/kg of caffeine. Body weights at 2-9 weeks and the final parametrail adipose tissue weights were significantly lower in the ovx-caf 0.3% group than in the ovx-c group. Food intakes were significantly lower in the ovx-caf 0.3% group than in the ovx-c group. After 9 weeks, the rats were killed and adipose tissues were sampled immediately. Basal lipolysis was increased in the ovx-caf 0.3% group fed the control diet containing 3 g/kg of caffeine than in the ovx-c group fed the control diet. The relative content of calcium (g/100 g body weight) in the ovx-caf 0.3% group was significantly increased compared with that in the ovx-c group. These results show a new possible role for caffeine in the prevention of lifestyle-related diseases.

Caffeine and resistance of coffee to the berry borer Hypothenemus hampei (Coleoptera: Scolytidae).

The role of caffeine as a chemical defense of coffee against the berry borer Hypothenemus hampei was investigated. No positive correlation was observed between resistance and caffeine content in experiments in which seeds from several coffee species presenting genetic variability for the alkaloid were exposed to adult insects. The same was observed in an experiment with coffee seeds that had their caffeine content doubled by imbibition with caffeine aqueous solutions. Other experiments showed that the attractiveness to insects was not related to the caffeine content of mature fruits. These results indicate that H. hampei has evolved an adaptation to handle the toxic effects of caffeine.

The effect of caffeine on peripheral vascular resistance in isolated perfused guinea pig hind limbs.

The role of caffeine in cardiovascular disease is controversial. Most of its pharmacologic actions are attributed to its role as an adenosine antagonist. Adenosine is one of the most important endogenous vasodilatative substances and is released under ischemic conditions, for example, in the skeletal muscle of patients with peripheral arterial occlusive disease. We aimed to investigate the influence of caffeine on peripheral vascular resistance and on the beneficial vasodilatory effect of adenosine in isolated perfused guinea pig hind limbs. (1) Caffeine was administered at 0.5, 5, and 50 micromol/L under normoxic conditions. (2) The vasculature of the perfused guinea pig hind limb was precontracted with noradrenaline (3 micromol/L), followed by adenosine (10 micromol/L) under normoxic conditions. When vascular resistance (VR) had reached a steady state, caffeine was administered additionally at dosages of 0.5, 5, and 50 micromol/L. (3) This protocol was repeated using iloprost 0.1 micromol/L instead of adenosine as vasodilatory substance. (4) Under hypoxia, caffeine was again administered at the above dosages. (5) Under hypoxia, experiments with adenosine A2-receptor antagonists (alloxazine 10 micromol/L and ZM 241385 100 nmol/L) were done. Under normoxic conditions, 0.5 and 5 micromol/L caffeine had nearly no effect on vascular resistance compared with baseline conditions. A slight, but statistically not significant decrease in VR was achieved with 50 micromol/L caffeine. In the presence of noradrenaline, the vasodilatory effect of adenosine was reduced by 7.6 +/- 1.6% after the addition of 0.5 micromol/L caffeine, and by 37.3 +/- 3.8% at a dosage of 5 micromol/L caffeine. A dosage of 50 micromol/L caffeine completely abolished the vasodilatative effect of adenosine. In the presence of iloprost, only a slight but statistically insignificant inhibitory influence (0.9%) of caffeine at a dosage of 50 micromol/L could be seen. Hypoxia significantly reduced VR. Caffeine at 0.5 micromol/L diminished this effect by about 53.2 +/- 4.6% and abolished it at 5 and 50 micromol/L. The hypoxia-induced adenosine-mediated vasodilatation seems to be an adenosine A2A-receptor-mediated effect. The observed effect of hypoxia-induced vasodilatation in peripheral arteries may be the result of the vasodilatory effect of elevated endogenous adenosine during hypoxia. For patients with peripheral arterial disease, drinking of caffeine-containing beverages may reduce the beneficial vasodilatory effect of elevated endogenous adenosine levels.

Histological and Histochemical Studies on the Role of Caffeine on Radiation damage of the Liver

Histological and Histochemical Studies on the Role of Caffeine on Radiation damage of the Liver

Histological and Histochemical Studies on the Role of Caffeine on Radiation damage of the Liver

The present study was designed to evaluate effect of caffeine to gamma irradiated rats. Forty eight female albino rats (120-150 gm) were divided into four groups (each of them 12 rats). The first group was considered as control. The animals in the second group were injected I.P. with caffeine (80 mg/Kg b.w.), the third group exposed to (7Gy) -radiation while the animals in the fourth group injected I.P with caffeine (80 mg/Kg. b. w.) 1 h prior to wholebody dose of -rays (7 Gy). Fresh liver specimens were obtained after 1 and 3 days of treatment. Paraffin sections were prepared for histological study (Hx & E.) and frozen sections were prepared for histochemical study for localization of both acid, alkaline phosphatases and succinic dehgdrogenase enzymes. The enzymatic activity was quantitatively evaluated and statistically analyzed. The obtained results showed that whole body -irradiation of rats induced definite microscopic changes in the liver represented by periportal fibrosis with some necrotic hepatic tissue. Meanwhile caffeine alone showed histological pattern more or less near to normal. On the other hand -rays combined with I.P. injection of caffeine revealed vaculated hepatocytes with dilated blood sinusoids. Histochemical changes were also observed showing significant increase in both acid phosphatase and succinic dehydrogenase enzymes activity after one and three days post exposure while the alkaline phosphatase enzyme activity showed significant decrease after one day and increase after three days of exposure. Administration of caffeine (1, 3, 7-trimethylzanthine), a major component of coffee (80 mg/Kg body weight), 60 min prior to whole body lethal dose of gamma-irradiation (7 Gy) resulted in improvement of the radiation induced changes in the activity of measured enzymes

Enhanced UV sensitivity of Thiobacillus ferrooxidans resulting from caffeine and acriflavine treatment of irradiated cells.

This study was aimed at identifying the roles of caffeine and acriflavine, two repair inhibitors, on UV sensitivity of iron-oxidizing Thiobacillus ferrooxidans ATCC 13728. The UV-dose response survival curve was inflected in nature, suggesting the population heterogeneity of the isolate. Caffeine and acriflavine potentiated the UV-induced killing of the organism. With the increase in concentrations of these compounds, the extent of survival decreased. Similarly, the inhibitory effects of caffeine and acriflavine increased with the increase in dose of UV-irradiation. The cells irradiated with 10 s (equivalent to 5.6 x 10(-5) J/m2/s) of UV-exposure tended to become resistant to the inhibitory effects of caffeine and acriflavine, as evidenced by the time course study of recovery. The cells appear to stage a dramatic recovery from UV damage in the presence of caffeine (3.0 mg/ml) and acriflavine (20 microg/ml) over a period of 25-30 h and 35-40 h respectively, when grown in the presence of energy sources.

Mania Associated with an Energy Drink: The Possible Role of Caffeine, Taurine, and Inositol

Mania Associated with an Energy Drink: The Possible Role of Caffeine, Taurine, and Inositol

Consumption of tea modulates the urinary excretion of mutagens in rats treated with IQ. Role of caffeine

The present study was undertaken to investigate whether the consumption of green tea and black tea influences the excretion of mutagens and promutagens in rats treated orally with the food carcinogen 2-amino-3-methylimidazo[4,5- f]quinoline (IQ). Rats were maintained on aqueous extracts (2.5%, w/v) of green tea, black tea or decaffeinated black tea as their sole drinking liquid. After 4 weeks, the animals received, by gastric intubation, a single dose of IQ (5 mg/kg), and urine was collected for 48 h. Direct and indirect mutagenicity, in the presence of an activation system derived from Aroclor 1254-treated rats, was determined in the urine samples using the Ames mutagenicity assay. Consumption of green tea and black tea, but not of decaffeinated black tea, markedly decreased the urinary excretion of mutagens and promutagens. In a further study, supplementation of decaffeinated black tea with caffeine suppressed the excretion of mutagens and promutagens in the urine of rats pretreated with IQ. It is concluded that both green tea and black tea modulate the bioactivation and metabolism of IQ, and that caffeine is largely responsible for this effect.

Role of caffeine and tannin in anti-toxigenic properties of coffee and tea

Aflatoxins B 1, B 2, G 1 and G 2 produced by Aspergillus parasiticus var. globosus IMI 120920 in detannin-caffeinated coffee and black tea were five times more concentrated than in normal tea and coffee. Extracts of normal coffee and tea powders significantly reduced aflatoxins production in liquid broth at 1 and 3 % concentrations, with tea extract. having a more pronounced effect than coffee extract Relevant anti-aflatoxigenic properties appear to be due to tannin and caffeine. These induced 95 % inhibition in aflatoxins at 0.3 % and 0.6 %, respectively. Roasting of contaminated coffee beans at 200 °C for 20 min is effective in the reduction of aflatoxins.

Is Caffeine Involved in the Pathogenesis of Combat-Stress Reaction?

The role of caffeine in the pathogenesis of combat-stress reaction is discussed in light of the expanding literature on caffeine's influence on stress reactions in animals and in humans, and in regard to the two clinical entities concerning caffeine: caffeinism and caffeine withdrawal. It is proposed that caffeine is a contributing factor to the development of combat-stress reaction and that the use of decaffeinated coffee in military settings might reduce the prevalence of the various anxiety reactions, including combat-stress reaction.

A reappraisal of the role of caffeine in ECT.

Caffeine lengthens ECT seizures, perhaps by lowering the convulsive threshold. The authors assessed the impact of caffeine on the convulsive threshold and seizure duration. The convulsive threshold and seizure durations of 12 inpatients receiving right unilateral ECT were determined with and without caffeine pretreatment. Caffeine did not change the convulsive threshold, but it did lengthen seizure duration. Caffeine's lengthening of seizure duration without affecting the convulsive threshold is an uncertain benefit in right unilateral ECT.

The role of nicotine in tobacco use

The 1988 US Surgeon General's Report titled "Nicotine Addiction", is cited frequently in the literature as having established the "fact" that nicotine derived from cigarette smoke is addictive in the same sense as "classic" addicting drugs such as heroin and cocaine. This manuscripts critically evaluates key research findings used in support of this claim and identifies shortcomings in the data that seriously question the logic of labeling nicotine as "addictive". In addition, the manuscript argues that the role of nicotine in tobacco use is not like the role of cocaine in coca leaf use as argued by the 1988 Surgeon General's Report, but is, in fact, more like the role of caffeine in coffee drinking as concluded in the 1964 US Surgeon General's Report.

Confounders contributing to the reported associations of coffee or caffeine with disease

The role of caffeine or coffee in causing or promoting the incidence of serious disease is equivocal. Two design factors may account for the discrepancies in reported findings on the effects of coffee drinking: (a) imprecision of measurement and (b) confounding variables. A study of 2,714 white U.S. adults disclosed that, of 32 risk factors analyzed by linear and logistic regression, only sex and cigarette smoking were found to be important potential confounders of caffeine and coffee intake. Partial R 2 values of the other 30 risk factors were relatively small and were inconsistent for each sex. It is unlikely that any of these factors could explain any of the reported associations between caffeine or coffee consumption and certain diseases. However, certain weak associations with caffeine or coffee intake should be included in the study design when they are known to be risk factors of a disease under investigation. These factors for men are dietary fat intake, vitamin C intake, and body mass index; and for women are vitamin use, alcohol intake, stress, and perceived health status.