Serum Metabolome of Coffee Consumption and its Association With Bone Mineral Density: The Hong Kong Osteoporosis Study.

BACKGROUND: Inconsistent associations between coffee consumption and bone mineral density (BMD) have been observed in epidemiological studies. Moreover, the relationship of bioactive components in coffee with BMD has not been studied. The aim of the current study is to identify coffee-associated metabolites and evaluate their association with BMD. METHODS: Two independent cohorts totaling 564 healthy community-dwelling adults from the Hong Kong Osteoporosis Study (HKOS) who visited in 2001-2010 (N = 329) and 2015-2016 (N = 235) were included. Coffee consumption was self-reported in an food frequency questionnaire. Untargeted metabolomic profiling on fasting serum samples was performed using liquid chromatography-mass spectrometry platforms. BMD at lumbar spine and femoral neck was measured by dual-energy X-ray absorptiometry. Multivariable linear regression and robust regression were used for the association analyses. RESULTS: 12 serum metabolites were positively correlated with coffee consumption after Bonferroni correction for multiple testing (P < 4.87 × 10-5), with quinate, 3-hydroxypyridine sulfate, and trigonelline (N'-methylnicotinate) showing the strongest association. Among these metabolites, 11 known metabolites were previously identified to be associated with coffee intake and 6 of them were related to caffeine metabolism. Habitual coffee intake was positively and significantly associated with BMD at the lumbar spine and femoral neck. The metabolite 5-acetylamino-6-formylamino-3-methyluracil (AFMU) (ß = 0.012, SE = 0.005; P = 0.013) was significantly associated with BMD at the lumbar spine, whereas 3-hydroxyhippurate (ß = 0.007, SE = 0.003, P = 0.027) and trigonelline (ß = 0.007, SE = 0.004; P = 0.043) were significantly associated with BMD at the femoral neck. CONCLUSIONS: 12 metabolites were significantly associated with coffee intake, including 6 caffeine metabolites. Three of them (AFMU, 3-hydroxyhippurate, and trigonelline) were further associated with BMD. These metabolites could be potential biomarkers of coffee consumption and affect bone health.

Determination of 12 potential nephrotoxicity biomarkers in rat serum and urine by liquid chromatography with mass spectrometry and its application to renal failure induced by Semen Strychni.

In previous nephrotoxicity metabonomic studies, several potential biomarkers were found and evaluated. To investigate the relationship between the nephrotoxicity biomarkers and the therapeutic role of Radix Glycyrrhizae extract on Semen Strychni-induced renal failure, 12 typical biomarkers are selected and a simple LC-MS method has been developed and validated. Citric acid, guanidinosuccinic acid, taurine, guanidinoacetic acid, uric acid, creatinine, hippuric acid, xanthurenic acid, kynurenic acid, 3-indoxyl sulfate, indole-3-acetic acid, and phenaceturic acid were separated by a Phenomenex Luna C18 column and a methanol/water (5 mM ammonium acetate) gradient program with a runtime of 20 min. The prepared calibration curves showed good linearity with regression coefficients all above 0.9913. The absolute recoveries of analytes from serum and urine were all more than 70.4%. With the developed method, analytes were successfully determined in serum and urine samples within 52 days. Results showed that guanidinosuccinic acid, guanidinoacetic acid, 3-indoxyl sulfate, and indole-3-acetic acid (only in urine) were more sensitive than the conventional renal function markers in evaluating the therapeutic role of Radix Glycyrrhizae extract on Semen Strychni-induced renal failure. The method could be further used in predicting and monitoring renal failure cause by other reasons in the following researches.

Phenolic acid concentrations in plasma and urine from men consuming green or black tea and potential chemopreventive properties for colon cancer.

SCOPE: Tea polyphenols are metabolized by the colonic microflora yielding phenolic metabolites, which may contribute to the health benefits of tea. We determined the serum and urine concentrations of phenolic acids, hippuric acid, and polyhydroxyphenyl-γ-valerolactones during green tea (GT) and black tea (BT) administration. The effects of (-)-epigallocatechin gallate (EGCG) and 3,4-dihydroxyphenylacetic acid (3,4-DHPAA) alone and in combination on bioavailability, intracellular metabolism, and antiproliferative activity were determined in HCT-116 colon cancer cells. METHODS AND RESULTS: The concentration of phenolic metabolites was quantified by HPLC with electrochemical detection and MS. Urine concentrations of 4-hydroxyphenylacetic acid (4-HPAA), 3-hydroxyphenylacetic acid (3-HPAA), and polyhydroxy-γ-valerolactones were increased significantly in men drinking GT compared to control. Urine concentration of 3-O-methylgallic acid (3OMGA) was significantly increased in men drinking BT compared to control. Serum 3,4-DHPAA was significantly increased after consumption of GT and BT and 4-HPAA after GT consumption. In vitro treatment of HCT-116 colon cancer cells with 3,4-DHPAA and EGCG exhibited an additive antiproliferative effect, while methylation of 3,4-DHPAA was significantly decreased. 3OMGA exhibited the strongest antiproliferative activity among the phenolic acids. CONCLUSION: The consumption of both, GT and BT, was associated with a significant increase in urinary and serum phenolic acids.

Absorption and metabolism of benzoic acid in growing pigs.

Dietary benzoic acid (BA) supplementation causes a pronounced reduction in urinary pH but only small changes in blood pH. The present study aimed to investigate the portal absorption profile, hepatic metabolism of BA, and renal excretion of hippuric acid (HA) underlying the relatively small impact of BA on systemic acid-base status. Eight growing pigs (BW = 63 +/- 1 kg at sampling) fitted with permanent indwelling catheters in the abdominal aorta, hepatic portal vein, hepatic vein, and mesenteric vein were allocated to 4 sampling blocks and randomly assigned to control (CON; nonsupplemented diet) or BA supplementation (B; control diet + 1% BA top-dressed). Feed intake was restricted to 3.6% of BW and the ration divided into 3 equally sized meals offered at 8-h intervals. Blood pH (7.465 and 7.486 +/- 0.004) and urinary pH (4.99 and 7.01 +/- 0.09) were less (P = 0.03 and P < 0.01) in B compared with CON. The arterial concentration, net portal flux, and net hepatic uptake of BA increased (P < 0.01) in B compared with CON. The net portal flux of BA increased (P < 0.01) after feeding with B, but remained positive (P < 0.01) at all sampling times (n = 8). Recovery of dietary BA as increased net portal flux and hepatic uptake of BA was 87 +/- 5% and 89 +/- 15%, respectively. The recovery of dietary BA as urinary excretion of BA and HA was 0.08 +/- 0.02% and 85 +/- 7%, respectively. It is concluded that the small impact of BA supplementation on systemic acid-base status was caused by a protracted BA absorption and efficient hepatic extraction and glycine conjugation in combination with efficient renal clearance of HA. Together, these physiological mechanisms prevented major BA and HA accumulation in body fluids.

Pharmacokinetics and bioavailability of cinnamic acid after oral administration of Ramulus Cinnamomi in rats.

The pharmacokinetics of cinnamic acid (CA) after oral administration of Decoction of Ramulus Cinnamomi (RC) 7.4 g/kg [containing CA 7.62 x 10(-5) mol/kg and cinnamaldehyde (CNMA) 1.77 x 10(-5) mol/kg], was compared with that after oral administration of pure CA 7.62 x 10(-5) mol/kg in rats. Plasma concentrations of CA and hippuric acid (HA) were determined by HPLC. Pharmacokinetic parameters were calculated from the plasma concentration-time data. CA was quickly absorbed and then metabolized mainly into HA. The AUC(0-t) and AUC(0-infinity)) of CA were higher in RC group than those in pure CA group and the bioavailability of CA from RC was higher than that from pure CA. After ig administration of 3.79 x 10(-4) mol/kg, CNMA was at least partially metabolized into CA in stomach and small intestine and almost completely metabolized into CA in liver before it is absorbed into blood in rats. The results showed that plasma CA in RC group might partly come from transformation of CNMA in RC.

Antioxidant metabolism induced by quinic acid. Increased urinary excretion of tryptophan and nicotinamide.

For over 50 years, hippuric/quinic acids were believed to have no biological efficacy. Here data are presented to support the hypothesis that quinic acid is not responsible for any efficacy, but rather that quinic acid nutritionally supports the synthesis of tryptophan and nicotinamide in the gastrointestinal (GI) tract, and that this in turn leads to DNA repair enhancement and NF-kB inhibition via increased nicotinamide and tryptophan production.Moreover, it is shown that quinic acid is a normal constituent of our diet, capable of conversion to tryptophan and nicotinamide via the GI tract microflora, thus providing an in situ physiological source of these essential metabolic ingredients to humans. The concentrations of quinic and hippuric acids in the diet were dependent on each other when analysed in urine, as was evidenced by a significant linear regression analysis that included unsupplemented control subjects (n = 45, p < 0.001). Thus, these ingredients were identified as major dietary components, and not simply originating from environmental pollution as previously had been thought.

Uremic sera contain inhibitors that block digitoxin-valproic acid interaction.

BACKGROUND: Digitoxin and valproic acid show strong binding to serum albumin. Thus, when present simultaneously in serum, digitoxin and valproic acid compete for binding sites. We studied digitoxin-valproic acid interaction in normal and uremic sera. METHODS: Fluorescence polarization immunoassays were used for measuring total digitoxin and total valproic acid concentrations. We used a modified protocol of improved sensitivity to measure free digitoxin concentrations. We supplemented 2 normal and 2 uremic pools with digitoxin and then aliquots of these pools were further supplemented with various concentrations of valproic acid. After incubation at 37 degrees C for 2 hours in a water bath, specimens were allowed to re-equilibrate at room temperature for 20 minutes. Free digitoxin concentrations were measured. We also investigated digoxin-valproic acid interaction using 1 normal and 1 uremic serum pool. RESULTS: We observed significant increases in free digitoxin concentrations in normal sera in the presence of valproic acid. In contrast, we observed a slight decline in free digitoxin concentration in the presence of valproic acid in uremic sera. We speculated that uremic sera contained inhibitors that block digitoxin-valproic acid interaction and identified indoxyl sulfate as an inhibitor. However, another uremic compound, hippuric acid showed no inhibitory effect. Interestingly, we observed no significant interaction between digoxin and valproic acid in either normal or uremic serum pool. This is probably because of poor protein binding of digoxin. CONCLUSION: We conclude that valproic acid significantly displaces digitoxin from protein binding sites in normal serum. However, uremic sera contain inhibitors that block digitoxin-valproic acid interaction.

Pharmacokinetics of salicin after oral administration of a standardised willow bark extract.

OBJECTIVE: To evaluate the pharmacokinetics of salicin and its major metabolites in humans after oral administration of a chemically standardised willow bark extract. METHODS: Willow bark extract corresponding to 240 mg salicin (1,360 mg, 838 micromol) was ingested by ten healthy volunteers in two equal doses at times 0 h and 3 h. Over a period of 24 h, urine and serum levels of salicylic acid and its metabolites, i.e. gentisic acid and salicyluric acid, were determined using reverse-phase high-performance liquid chromatography. Renal excretion rate, elimination half-life and total bioavailability of salicylates were calculated. RESULTS: Salicylic acid was the major metabolite of salicin detected in the serum (86% of total salicylates), besides salicyluric acid (10%) and gentisic acid (4%). Peak levels were reached within less than 2 h after oral administration. Renal elimination occurred predominantly in the form of salicyluric acid. Peak serum levels of salicylic acid were on average 1.2 mg/l, and the observed area under the serum concentration time curve (AUC) of salicylic acid was equivalent to that expected from an intake of 87 mg acetylsalicylic acid. CONCLUSION: Willow bark extract in the current therapeutic dose leads to much lower serum salicylate levels than observed after analgesic doses of synthetic salicylates. The formation of salicylic acid alone is therefore unlikely to explain analgesic or anti-rheumatic effects of willow bark.

Effects of gavage versus dosed feed administration on the toxicokinetics of benzyl acetate in rats and mice.

Effects of gavage versus dosed feed administration on the toxicokinetics of benzyl acetate were studied in male F344 rats and B6C3F1 mice. Benzyl acetate was rapidly hydrolysed to benzyl alcohol and then oxidized to benzoic acid. After gavage administration of benzyl acetate in corn oil at 500 mg/kg (rats) and 1000 mg/kg (mice), high benzoic acid plasma concentrations were observed. In contrast, much lower benzoic acid plasma concentrations were found after dosed feed administration at about 615 mg/kg/day for rats and about 850 mg/kg/day for mice. Results show that although the daily doses of benzyl acetate are comparable, bolus gavage administration effectively saturated the benzoic acid elimination pathway whereas dosed feed administration did not. In contrast, hippuric acid plasma concentrations were similar after both gavage and dosed feed administration due to the depletion of the glycine supply pool. Study results could explain the different toxicity and carcinogenicity responses of benzyl acetate observed in 2-yr chronic gavage and dosed feed studies.

Effects of dietary sodium selenite supplementation on salicylate-induced embryo- and fetotoxicity in the rat.

The effects of dietary supplementation with sodium selenite (3.0 or 4.5 ppm Se) for 8 weeks prior to and throughout gestation on sodium salicylate induced embryo- and fetotoxicity (resorptions, fetal deaths, malformations, fetal weight reduction) have been studied in the rat. Salicylate was administered either as daily intragastric bolus doses of 250 mg/kg on gestation days 6-13 (maternal peak and trough salicylate levels of 222-120 micrograms/ml whole-blood) or via constant rate intravenous infusion of 150 mg/kg/day on the same gestation days via implanted osmotic minipumps (stable average maternal blood salicylate level of 120 micrograms/ml = human antirheumatic concentration). Both gavage and infusion of salicylate resulted in an increase of resorptions and fetal deaths as well as a decrease of fetal body weights. Gavage with salicylate also produced about 50% malformed fetuses. Selenite did not protect against the embryotoxic effects of salicylate administered as intragastric bolus doses. However, selenite was found to significantly increase fetal survival rate in the infusion experiment, although it did not counteract the decrease of fetal body weight. In animals fed selenite only, no negative effects on fetal body development were noted. The protective effect of selenite against salicylate induced embryotoxicity is difficult to explain, since very little is known about the mechanisms of salicylate embryotoxicity and the biological effects of selenium. However, an interaction between selenium, via glutathione peroxidase, and salicylate at the level of prostaglandin synthesis could be possible.

Determination of benzoic acid and hippuric acid in human plasma and urine by high-performance liquid chromatography.

For patients with inborn errors of urea synthesis, oral administration of sodium benzoate is the usual treatment to increase the nitrogen excretion. Thus, monitoring hippuric acid and benzoic acid simultaneously in human biological fluids is considered to be clinically important. We developed a simple and accurate high-performance liquid chromatographic method for the simultaneous determination of hippuric acid and benzoic acid in human plasma and urine. This method requires no extraction step. Aliquots of urine and plasma are added to a solution of internal standard (o-chlorobenzoic acid) in acetonitrile and directly injected onto a reversed-phase column using an acidic (pH 2.7) eluent and ultraviolet detection at 235 nm. The preliminary plasma concentration-time and urinary excretion rate-time profiles of hippuric acid and benzoic acid from a healthy subject receiving small, medium and large doses of sodium benzoate are reported.

Studies on benzyl acetate. I. Effect of dose size and vehicle on the plasma pharmacokinetics and metabolism of [methylene-14C]benzyl acetate in the rat.

Male Fischer 344 rats received [methylene-14C]benzyl acetate by gavage in a dose of 5,250 or 500 mg/kg, as the neat substance, in corn oil or in propylene glycol. Urine and faeces were collected and urinary metabolites were assayed by radio-TLC and HPLC. Other animals were killed at various times and exsanguinated, and plasma levels of 14C in Plasma occurred earliest and were highest when benzyl acetate was given neat. Peak levels were lower and absorption was delayed with the propylene glycol vehicle. The use of corn oil as the dose vehicle at the higher doses (250 and 500 mg/kg) led to the maintenance of plateau plasma levels, at about one half of the peak levels seen with the neat compound, for up to 8 hr after administration. At the 5 mg/kg dose, the plasma levels of 14C were essentially the same whether the dose was given in corn oil or propylene glycol. At the 250- and 500-mg/kg doses, at all time points, the major metabolite in plasma was benzoic acid, accompanied by smaller amounts of hippuric acid. Benzyl alcohol was also detected in some plasma samples. At the 5-mg/kg dose, the major plasma metabolite was hippuric acid, together with a smaller amount of benzoic acid. When propylene glycol was used as the vehicle at this dose level, benzylmercapturic acid was also present in the plasma. The major urinary metabolite was hippuric acid (c. 66% of the dose), with benzoic acid (2%) and benzylmercapturic acid (1%) also present. The elimination of benzoyl glucuronide increased with increasing dose, from c. 3 to 11% of the dose.

Plasma and synovial fluid concentrations of salicylic acid and its metabolites in patients with joint effusions.

Equilibration of salicylic, salicyluric and gentisic acids between plasma and synovial fluid (SF) was measured in 36 patients receiving chronic salicylate therapy and from whom SF was required for diagnostic purposes. Gentisic and salicyluric acids equilibrated completely, while SF salicylic acid concentration was less than that in plasma. The presence of significant gentisic acid concentrations in SF could contribute to the therapeutic response to chronic salicylate therapy, since its antiinflammatory effect is even greater than that of acetylsalicylic acid.