The effect of coffee drinking on platelet reactivity was studied in 12 healthy subjects. Plasma beta‐thromboglobulin concentration was determined before and one hour after administration of 100 mg of caffeine, corresponding to one cup of coffee. Mean values were 47.0±19.3 and 179.3±85.5 ng/ml before and after caffeine administration respectively. The increase, 298±150%, is highly significant (p<0.001).

We assessed the contribution of serum homocysteine levels, an independent risk factor for vascular disease, and of the methylenetetrahydrofolate reductase (MTHFR) C677T mutation to the variability of carotid intimal-medial thickness (IMT) in patients with non-insulin-dependent diabetes mellitus (NIDDM). Ninety-five patients (33 males and 62 females, mean age 53 +/- 10 years) without nephropathy or other vascular complications were enrolled. Fasting total serum homocysteine and other biochemical analytes were measured. The MTHFR polymorphism was determined by the polymerase chain reaction. Common carotid IMT and plaques or stenoses in the carotid district were measured by ultrasonography. Serum total homocysteine concentrations were higher in subjects with the mutant (Val/Val) genotype than in those with the Ala/Val plus Ala/Ala genotypes (P = 0.02). On univariate analysis, carotid IMT was significantly associated with age, body mass index (BMI), systolic blood pressure, and total cholesterolemia. No significant association was found between IMT and serum homocysteine or the MTHFR polymorphism, although a slightly greater IMT was observed in the homozygous Val genotypes. On multiple regression analysis, only age and BMI were independently associated with IMT and explained about 40% of IMT variability. The results did not change when the analysis was restricted to the subgroups with or without atherosclerotic plaques in the carotid district. In 95 Italian NIDDM patients without nephropathy, neither basal levels of serum total homocysteine nor the MTHFR C677T polymorphism predicted significant changes in common carotid intimal-medial thickness.

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The authors previously reported an increase in platelet aggregration in the days after coronary angiography, accompanied at times by worrying cardiovascular disorders (ventricular fibrillation in one case, death in two others). In the present study, ten patients received a platelet antiaggregating drug (ticlopidin) 5 days before their coronary angiography. No significant changes were detected in the test for circulating platelet aggregates (CPA test) in these patients.

The influence of caffeine on overall cell metabolism was studied in human platelets by measurement of cell heat production rate. One hour after administration of 100‐200 mg of caffeine, corresponding to 1‐2 cups of coffee, significantly increased values (p<0.001) were found, 12±7%. A return to normal values was noted 1 hour later. The cell metabolic stimulation is presumably due to increased catecholamines. A temporary significant rise in systolic (p<0.02) and diastolic (p<0.05) blood pressure was observed 1 hour after ingestion of caffeine.