Plasma Fatty Acid Profiling and Mathematical Estimation of the Omega-3 Index: Toward Diagnostic Tools in Atherosclerosis and Statin Therapy Monitoring

Abstract

Background/Objectives: Omega-3 highly unsaturated fatty acids (HUFAs), particularly EPA and DHA, have anti-inflammatory and lipid-modulating properties for treating atherosclerosis. However, the relationship between plasma fatty acid profiles, omega-3 status, and statin efficacy in carotid atherosclerosis remains poorly defined. Objectives: This study evaluates plasma and plaque fatty acid (FA) composition, explores their associations with plaque stability, and examines the relationship of omega-3 levels, lipid biomarkers (VLDL-C, LDL-C, HDL-C, total cholesterol, and triglycerides) with statin and β-blocker treatment. A mathematical model was developed to predict the erythrocyte omega-3 index from plasma. Methods: In this case-control study, plasma and carotid plaques of 52 patients undergoing carotid endarterectomy were analyzed. Plasma was compared with that of 50 healthy controls. FAs were quantified by LC-MS/MS. Plaques were histologically classified as stable or unstable. Results: Atherosclerotic patients showed disturbed FA metabolism, including decreased plasma omega-3 EPA + DHA, SFAs and HUFAs, increased MUFAs, and impaired desaturase and elongase activity. Unstable plaques had higher MUFA and lower HUFA content compared with stable plaques. Significant correlations between plasma EPA + DHA and HDL-C and triglycerides were observed in statin-naïve patients, whereas statins appeared to attenuate these associations. Co-treatment with β-blockers had no significant effect. A validated logit-based model accurately predicted the erythrocyte omega-3 index from plasma (R² = 0.782). Conclusions: Altered plasma and plaque FA profiles correlate with atherosclerosis's plaque instability and inflammatory lipid profiles. Statins significantly influence these associations, suggesting their complex interaction with lipid metabolism. Plasma measurements of omega-3 fatty acids in combination with predictive modelling may be beneficial for diagnostic and therapeutic monitoring in carotid atherosclerosis.

Keywords: atherosclerotic plaques; carotid atherosclerosis; lipid metabolism; omega-3 fatty acids; regression analysis; statins.

Figure 2

Biosynthesis pathway of SFA and MUFA with graph data of fatty acid composition in the plasma of the control and atherosclerosis (AS) group. 1—Palmitic acid (C16:0) % content; 2—C16:0/C18:0 ratio; 3—Stearic acid (C18:0) % content; 4—C18:0/20:0 ratio; 5—C20:0/22:0 ratio; 6—C18:0/C18:1n-9 ratio; 7—Oleic acid (C18:1n-9) % content; 8—Gondoic acid (C20:1n-9) % content. Statistically significant differences are indicated by ** (p < 0.01), and *** (p < 0.001), which were evaluated by an appropriate test. The enzyme nomenclature and metabolic scheme presented are based on previously published data [24,25,26,27,28,29]. FAs determined by the applied HPLC-MS/MS method are highlighted in bold. The other FAs involved in metabolism are written in italics. Fatty acid contents are expressed as percentages of the total identified fatty acids (%), whereas all fatty acid ratios (e.g., C16:0/C18:0) are reported as dimensionless numbers. The boxplots of parameters for stearic acid (C18:0) and oleic acid (C18:1n-9) indicate the mean ± SD. The other parameters’ boxplots are the median and [IQR 25–75%].

Figure 1

Comparative plasma levels of major fatty acid classes in healthy individuals (Control) and atherosclerosis patients (AS). The asterisks indicate that there are statistically significant differences versus the control group p-value < 0.05 (*), < 0.01 (**), and < 0.001 (***). All values in the figure are expressed as percentages (%). The boxplots of parameters TFA and HUFA indicate the median and [IQR 25–75%]. The lines inside the boxplots of other parameters indicate the mean ± SD.

Figure 3

Biosynthetic pathway of omega-3 and omega-6 with graphical data of fatty acid composition in plasma of control and atherosclerosis (AS) group. 1—C18:3n-6/C20:3n-6 ratio; 2—arachidonic acid (C20:4n-6) % content; 3—C20:4n-6/C22:4n-6 ratio; 4—EPA % content; 5—EPA/DPA ratio. Statistically significant differences are indicated by * (p < 0.05), ** (p < 0.01) and *** (p < 0.001), which were evaluated by an appropriate test. Enzyme names and the metabolic pathway diagram are adapted from literature sources as cited [34,35]. FAs determined by the applied HPLC-MS/MS method are highlighted in bold. The other FAs involved in metabolism are written in italics. Fatty acid contents are expressed as percentages of the total identified fatty acids (%), whereas all fatty acid ratios (e.g., EPA/DHA) are reported as dimensionless numbers. All the boxplots indicate the median and [IQR 25–75%].

Figure 4

Differences in fatty acid content in the plasma of control and atherosclerosis group with (Statin+) or without statin therapy (Statin−). Statistically significant differences are indicated by ** (p < 0.01), evaluated by the Kruskal–Wallis test. AA content is expressed as a percentage of the total identified fatty acids (%), whereas AA/APE ratio is reported as dimensionless numbers. All the boxplots indicate the median and [IQR 25–75%].

Figure 5

Linear regression (left) and logit-transformed regression (right) of EPA + DHA (%) between plasma and erythrocyte fractions (total lipids fraction). The logit transformation is defined as logit(y) = log (y/(100% − y)). The light gray area represents 95% prediction bands; the dark gray area represents 95% confidence bands (α = 0.05).