Caffeine (TMX) disposition was studied in mean after 1, 5, and 10 mg/kg in water, as mocha coffee (1.54 mg/kg) and as a soft drink (0.22 mg/kg). TMX and its metabolites were analyzed in plasma and urine by high-pressure liquid chromatography. The design permitted confirmation of most of the partial results in various experimental settings and contributed new data on the metabolic disposition of TMX, with specific reference to main dimethylxanthine metabolite found in plasma, paraxanthine (1,7-dimethylxanthine). Different analysis methods were compared for the calculated parameters (absorption and elimination rate constants and renal clearance)to assess the consistency of results. The kinetics of TMX and of its dimethylated metabolites in plasma were described with a model that used an analogdigital hybrid computing system. In addition to providing a comprehensive profile of TMS disposition in the healthy adult, the results indicate tha TMX exhibits dose-independent kinetics at the levels at which man normally takes TMX.
Serum uric acid (SUA) levels discriminating across the different strata of cardiovascular risk is still unknown. By utilizing a large population-based database, we assessed the threshold of SUA that increases the risk of total mortality and cardiovascular mortality (CVM). The URRAH study (Uric Acid Right for Heart Health) is a multicentre retrospective, observational study, which collected data from several large population-based longitudinal studies in Italy and subjects recruited in the hypertension clinics of the Italian Society of Hypertension. Total mortality was defined as mortality for any cause, CVM as death due to fatal myocardial infarction, stroke, sudden cardiac death, or heart failure. A total of 22 714 subjects were included in the analysis. Multivariate Cox regression analyses identified an independent association between SUA and total mortality (hazard ratio, 1.53 [95% CI, 1.21–1.93]) or CVM (hazard ratio, 2.08 [95% CI, 1.146–2.97];
P
<0.001). Cutoff values of SUA able to discriminate total mortality (4.7 mg/dL [95% CI, 4.3–5.1 mg/dL]) and CVM status (5.6 mg/dL [95% CI, 4.99–6.21 mg/dL]) were identified. The information on SUA levels provided a significant net reclassification improvement of 0.26 and of 0.27 over the Heart Score risk chart for total mortality and CVM, respectively (
P
<0.001). Sex-specific cutoff values for total mortality and CVM were also identified and validated. In conclusion, SUA levels increasing the risk of total mortality and CVM are significantly lower than those used for the definition of hyperuricemia in clinical practice. Our data provide evidence of a cardiovascular SUA threshold that might contribute in clinical practice to improve identification of patients at higher risk of CVM.
Abdominal adiposity was associated with altered renal tubular sodium handling apart from insulin resistance and high blood pressure. The data indicate that men with prevalent abdominal adiposity have an enhanced rate of tubular sodium reabsorption, mainly at proximal sites. These findings provide a possible mechanistic link between central adiposity and salt-dependent hypertension.
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