Characteristics of the Fatty Acid Composition in Elderly Patients with Occupational Pathology from Organophosphate Exposure

Background/Objectives: The delayed effects of subchronic and chronic organophosphate poisoning may manifest years after exposure, often masked by age-related diseases. The aim of this retrospective cohort study was to identify the biochemical "trace" that could remain in the patients decades after the poisoning. To achieve this goal, we determined a wide range of biochemical parameters, along with the spectrum of esterified and non-esterified fatty acids (EFA and NEFA, respectively), in the blood plasma of a cohort of elderly patients diagnosed with occupational pathology (OP) due to subacute or (sub)chronic exposure to organophosphates in the 1980s. Methods: Elderly patients with and without a history of exposure to organophosphates were retrospectively divided into two groups: controls (n=59, aged 73±4, men 29% and women 71%) and having the OP (n=84, aged 74±4, men 29% and women 71%). The period of neurological examination and blood sampling for subsequent analysis was approximately one and a half years - from mid-2022 to the end of 2023. Determination of the content of biomarkers of metabolic syndrome, NEFA and EFA in blood plasma was performed by HPLC-MS/MS and GC-MS. Results: The medical history of the examined elderly individuals with OP and the aged control group includes common age-related diseases. However, patients with OP more often have hepatitis (33 vs 7%, p<0.001) and other gastrointestinal diseases (54 vs 32%, p<0.05), total with diagnosis of polyneuropathy (87 vs 66%, p<0.01) and polyneuropathy of the upper and lower extremities (29 vs 12%, p<0.05), impaired distal sensitivity (83 vs 56%, p<0.001), increased body mass index (30.0±4.6 vs 28.4±4.1, p<0.05), and also they have an increased drug load (5 vs 4, p<0.001). Patients with OP more often have balance problems (84 vs 69%, p<0.05) and difficulties in performing daily activities (75 vs 49%, p<0.01). No differences were found between the groups when assessing cognitive function using the MMSE (mini mental state examination), SAGE (self-administered gerocognitive exam), and “Clock” tests. Of the 34 basic biochemical parameters determined on the biochemical analyzer, statistically significant changes were found for only 11, with their median values not going beyond the reference range (clinical norm), and the differences being due to significant individual deviations. Analysis of some metabolic biomarkers with HPLC-MS/MS revealed in the OP group a 1.4-fold decrease in the concentration of 3-hydroxybutyrate (p<0.05, AUC=0.62) and 1.6-fold decrease in the concentration of 2-hydroxybutyrate (p<0.0001, AUC=0.72). In the OP group, a 26% decrease in acetyl-L-carnitine concentration was found (p<0.001, AUC=0.69). An additional study of the esterase profile of patients revealed a decrease in the activity of butyrylcholinesterase (BChE) by 14% (p<0.05, AUC=0.62) though increase in the esterase activity of albumin by 29% (p<0.05, AUC=0.62) in the OP group. Correlation analysis revealed the most significant relationships between albumin esterase activity and arachidonic acid concentration in the OP group (0.64, p<0.0001). A study of a wide range of fatty acids in patients with OP revealed reciprocal relationships between EFA and NEFA. A decrease in concentration was shown for esters of margaric (p<0.01, AUC=0.65), stearic (p<0.01, AUC=0.65), eicosadienoic (p<0.01, AUC=0.63), eicosatrienoic (p<0.01, AUC=0.66), arachidonic (p<0.001, AUC=0.67), eicosapentaenoic (p<0.05, AUC=0.60), and docosahexaenoic (p<0.0001, AUC=0.74) fatty acids. An increase in the concentration was shown for free (non-esterified) fatty acids: heptadecenoic (p<0.0001, AUC=0.72), eicosapentaenoic (p<0.05, AUC=0.62), eicosatrienoic (p<0.001, AUC=0.68), docosahexaenoic (p<0.01, AUC=0.66), γ-linolenic (p<0.01, AUC=0.66), myristic (p<0.0001, AUC=0.71), eicosenoic (p<0.01, AUC=0.65), arachidonic (p<0.01, AUC=0.66), eicosadienoic (p<0.001, AUC=0.67), oleic (p<0.01, AUC=0.66), linoleic (p<0.01, AUC=0.65), palmitic (p<0.001, AUC=0.68), linoelaidic (p<0.01, AUC=0.65), stearic (p<0.01, AUC=0.64), palmitoleic (p<0.05, AUC=0.61), pentadecanoic (p<0.05, AUC=0.61), and margaric (p<0.01, AUC=0.64). Decrease in the ratios of omega-3 to other unsaturated fatty acids were observed only for the esterified forms: by 29% for n3/n6 (p<0.0001, AUC=0.70), by 33% for n3/(n6+n9) (p<0.0001, AUC=0.72), and by 26% for n3/(all fatty acids) (p<0.0001, AUC=0.72). Finally, we have found out how the most reliable indicators correlate with each other. The esterified docosahexaenoic acid – lactate dehydrogenase (LDH) (0.67, p <0.0001) and LDH – total antioxidant status (TAS) (-0.61, p <0.0001) correlations are stronger in the OP group compared to the correlation in the overall sample and lose their strength and statistical significance in the control group. In the OP group, esterified docosahexaenoic fatty acid, LDH activity, and TAS concentration have a moderate correlation with calcium concentration (-0.66, p <0.0001; -0.67, p <0.0001; 0.63, p <0.0001, respectively). In the control group, this correlation is significantly weakened. Esterified docosahexaenoic acid in the OP group also demonstrated strong positive correlations with a row of other esterified fatty acids, though these correlations were not significantly weakened in the control group. Conclusions: The data obtained allow us to consider an increased level of NEFA as one of the main cytotoxic factors for the vascular endothelium, which can determine the specificity of age-related diseases. Modification of albumin properties by arachidonic acid decreased bioavailability of docosahexaenoic acid could be molecular links that cause specific manifestations of OP-induced pathology at late stages after exposure. Epigenetic changes, the contribution of dietary patterns and intestinal microbiota to the spectrum of EFA and NEFA require additional research.