The development of accurate and applicable methods to assess the severity of patient condition is an urgent need in critical care medicine.The goal of the study was to determine whether the quantitave evaluation of phenylcarboxylic acids (PhCAs) concentrations in blood might be employed to assess the severity of patient condition and treatment efficiency intensive care unit.Materials and methods. Clinical and laboratory findings in patients (n=58) with acute surgical diseases of abdominal organs were registered on the day of admission to intensive care unit and during follow-up control including lactate level and blood serum PhCA concentrations of phenyllactic (PhLA), p#hydroxyphenyllactic (p-HPhLA) and phydroxyphenylacetic (p#HPhAA) acids. Patients' condition was assessed using APACHE II and SOFA international scales. PhCA concentrations were determined by gas chromatography. The reference group included healthy blood donors (n=25).Results. PhLA, p-HPhAA, p-HPhLA levels and total concentration of the three PhCAs were shown to be in direct correlation with APACHE II score (rs: 0.624; 0.757; 0.763 and 0.804, respectively; P<0.001). When testing PhCAs as a molecular prognostic criteria, areas under ROC#curves (AUC) were within the range of 0.800—0.900 (P<0.001). Therewith the molecular prognostic criteria were comparable with APACHE II multi#parameter scale by accuracy: AUCAPACHE II was 0.897 (P<0.001). Lactate level dynamics as a prognostic criterion was inferior in accuracy to the dynamics of PhCA total concentration: AUCС lactate, % 0.667 (P=0.071) vs AUCС 3PhCAs, % 0.862 (P<0.001). In patients with documented bacterial inflammatory complications PhCA level was 2.5 times higher (P<0,001, n=35) and p#HPhLA level was 1.5 times higher than in patients without infectious complications (P=0.048, n=23).Conclusion. The findings provide evidence for the inclusion of PhCAs (PhLA, p-HPhAA, p-HPhLA, 3PhCAs) in clinical practice as biomarkers of the severity of condition in patients with surgical diseases of abdominal organs. The study showed that change in PhCA serum concentrations reflected the dynamics of patient condition and might be used for objective monitoring of the treatment.

Previous studies showed that large amounts of phenylcarboxylic acids (PhCAs) are accumulated in a septic patient’s blood due to increased endogenous and microbial phenylalanine and tyrosine biotransformation. Frequently, biochemical aromatic amino acid transformation into PhCAs is considered functionally insignificant for people without monogenetic hereditary diseases. The blood of healthy people contains the same PhCAs that are typical for septic patients as shown in this paper. The overall serum PhCAs level was 6 μM on average as measured by gas chromatography with flame ionization detection. This level is a stable biochemical parameter indicating the normal metabolism of aromatic amino acids. The concentrations of PhCAs in the metabolic profile of healthy people are distributed as follows: phenylacetic ≈ p-hydroxyphenyllactic > p-hydroxyphenylacetic > phenyllactic ≈ phenylpropionic > benzoic. We conclude that maintaining of stable PhCAs level in the serum is provided as the result of integration of human endogenous metabolic pathways and microbiota.

A method has been developed for the determination of phenylcarboxylic acids (benzoic, p-hydroxyphenyllactic, p-hydroxyphenylacetic, phenyllactic, 3-phenylpropanoic, and phenylacetic) in blood serum by gas chromatography with a flame-ionization detector (FID). The quantitative characteristics of analysis obtained with the FID and mass spectrometric detectors are in the same range and exhibit common trends for different groups of samples. It has been shown that the reproducibility of the results increases with the addition of a stage of salting out to the sample preparation procedure. The accuracy of the results is estimated using the added-found method. A possibility of the application of widely used FID to the quantitative determination of phenylcarboxylic acids in blood serum has been demonstrated for routine clinical practice.

The effects of microbial phenolic metabolites on the activities of enzymes of the tricarboxylic acid cycle were investigated in isolated mitochondria. The detection of metabolites of the tricarboxylic acid cycle in the blood of patients with sepsis as potential biomarkers of mitochondrial dysfunction was investigated. We found that microbial phenolic metabolites possess an inhibitory effect on the activity of dehydrogenases, as determined by the reduction of dichlorophenolindophenol and nitroblue tetrazolium in liver mitochondria and liver homogenates. The effect was more pronounced in the case of the oxidation of NAD-dependent substrates than succinate oxidation, as well as at lower concentrations of microbial metabolites than in the case of inhibition of respiration. Using gas chromatography coupled with mass spectrometry it was shown that the content of the tricarboxylic acid cycle metabolites is lower in the blood of patients with sepsis as compared to healthy donors. Our data demonstrate that microbial phenolic acids can significantly contribute to mitochondrial dysfunction and to metabolic suppression, both of which are characteristic of these pathologies.