Hydrophilic interaction chromatography-mass spectrometry for anionic metabolic profiling of urine from antibiotic-treated rats.

Hydrophilic interaction chromatography-mass spectrometry (HILIC-MS) was used for anionic metabolic profiling of urine from antibiotic-treated rats to study microbial-host co-metabolism. Rats were treated with the antibiotics penicillin G and streptomycin sulfate for four or eight days and compared to a control group. Urine samples were collected at day zero, four and eight, and analyzed by HILIC-MS. Multivariate data analysis was applied to the urinary metabolic profiles to identify biochemical variation between the treatment groups. Principal component analysis found a clear distinction between those animals receiving antibiotics and the control animals, with twenty-nine discriminatory compounds of which twenty were down-regulated and nine up-regulated upon treatment. In the treatment group receiving antibiotics for four days, a recovery effect was observed for seven compounds after cessation of antibiotic administration. Thirteen discriminatory compounds could be putatively identified based on their accurate mass, including aconitic acid, benzenediol sulfate, ferulic acid sulfate, hippuric acid, indoxyl sulfate, penicillin G, phenol and vanillin 4-sulfate. The rat urine samples had previously been analyzed by capillary electrophoresis (CE) with MS detection and proton nuclear magnetic resonance ((1)H NMR) spectroscopy. Using CE-MS and (1)H NMR spectroscopy seventeen and twenty-five discriminatory compounds were found, respectively. Both hippuric acid and indoxyl sulfate were detected across all three platforms. Additionally, eight compounds were observed with both HILIC-MS and CE-MS. Overall, HILIC-MS appears to be highly complementary to CE-MS and (1)H NMR spectroscopy, identifying additional compounds that discriminate the urine samples from antibiotic-treated and control rats.

Long-term intake of a high-protein diet with or without potassium citrate modulates acid-base metabolism, but not bone status, in male rats.

High dietary protein intake generates endogenous acid production, which may adversely affect bone health. Alkaline potassium citrate (Kcit)(2) may contribute to the neutralization of the protein-induced metabolic acidosis. We investigated the impact of 2 levels of protein intake and Kcit supplementation on acid-base metabolism and bone status in rats. Two-month-old Wistar male rats were randomly assigned to 4 groups (n = 30 per group). Two groups received a normal-protein content (13%) (NP) or a high-protein (HP) content diet (26%) for 19 mo. The 2 other groups received identical diets supplemented with Kcit (3.60%) (NPKcit and HPKcit). Rats were pair-fed based on the ad libitum intake of the HP group. At 9, 16, and 21 mo of age, 10 rats of each group were killed. The HP diet induced a metabolic acidosis characterized by hypercalciuria, hypermagnesuria, and hypocitraturia at all ages. Kcit supplementation neutralized this effect, as evidenced by decreased urinary calcium and magnesium excretion by the HPKcit rats. Femoral bone mineral density, biomechanical properties, bone metabolism biomarkers (osteocalcin and deoxypyridinoline), and plasma insulin-like growth factor 1 levels were not affected by the different diets. Nevertheless, at 21 mo of age, calcium retention was reduced in the HP group. This study suggests that lifelong excess of dietary protein results in low-grade metabolic acidosis without affecting the skeleton, which may be protected by an adequate calcium supply.

Effects of plant food potassium salts (citrate, galacturonate or tartrate) on acid-base status and digestive fermentations in rats.

Potassium (K) organic anion salts, such as potassium citrate or potassium malate in plant foods, may counteract low-grade metabolic acidosis induced by western diets, but little is known about the effect of other minor plant anions. Effects of K salts (chloride, citrate, galacturonate or tartrate) were thus studied on the mineral balance and digestive fermentations in groups of 6-week-old rats adapted to an acidogenic/5 % inulin diet. In all diet groups, substantial amounts of lactate and succinate were present in the caecum, besides SCFA. SCFA were poorly affected by K salts conditions. The KCl-supplemented diet elicited an accumulation of lactate in the caecum; whereas the lactate caecal pool was low in rats fed the potassium tartrate-supplemented (K TAR) diet. A fraction of tartrate (around 50 %) was recovered in urine of rats fed the K TAR diet. Potassium citrate and potassium galacturonate diets exerted a marked alkalinizing effect on urine pH and promoted a notable citraturia (around 0.5 micro mol/24 h). All the K organic anion salts counteracted Ca and Mg hyperexcretion in urine, especially potassium tartrate as to magnesuria. The present findings indicate that K salts of unabsorbed organic anions exert alkalinizing effects when metabolizable in the large intestine, even if K and finally available anions (likely SCFA) are not simultaneously bioavailable. Whether this observation is also relevant for a fraction of SCFA arising from dietary fibre breakdown (which represents the major organic anions absorbed in the digestive tract in man) deserves further investigation.

High-sensitivity capillary electrophoresis determination of inorganic anions in serum and urine using on-line preconcentration by transient isotachophoresis.

Concentrations of inorganic anions, both as individual species and biotransformation products, in physiological fluids are of strong concern in clinical studies. To date, analytical methodologies have either required different analytical procedures to determine these analytes in plasma and urine, or extensive sample preparation, or unconventional and often expensive detection schemes, or both. A simple and sensitive capillary electrophoresis (CE) method with direct UV detection was developed for the simultaneous determination of iodide, bromide and nitrate in human plasma and urine, with a special focus on reliable quantification of the trace serum iodide. With the latter objective, the method incorporates a transient isotachophoresis (tITP) procedure enabling an efficient on-line preconcentration of iodide (limit of detection, 1.4 microg l(-1)) as well as other moderately mobile analytes that fall into the tITP range. The analyses of both types of biofluids were performed using an acidic electrolyte system composed of 0.25 mol l(-1) sodium chloride and 7.5 mmol l(-1) cetyltrimethylammonium chloride at pH 2.2 and 0.5 mol l(-1) 2-(N-morpholino)ethanesulfonate (pH 6.0) as terminating electrolyte. Relative standard deviations (R.S.D.) below 3.0% and 9.2% were obtained for within-day and between-day precision, respectively. Resolution and quantification of oxalic acid was also feasible under optimized tITP-CE conditions. Sample preparation required only ultrafiltration (serum) and dilution (urine). A number of plasma and urine samples were evaluated with this assay and the iodide, bromide and nitrate concentrations were in the expected clinical concentration ranges.