High Gal-3 levels are associated with the presence of significant carotid plaques, independent of sex, age, LDL levels, or previous myocardial infarction [13, 14]. Gal-3 and carotid intima-media thickness are independent indicators of increased mortality in patients with previous myocardial infarction [15]. Similarly, patients with low serum Gal-3 levels who underwent coronary angiography had a lower incidence of cardiovascular (CV) events during short-term follow-up. Low serum Gal-3 levels were a better predictor of a lower incidence of CV events than the absence of carotid plaques [16]. In long-term follow-up, higher Gal-3 levels were associated with higher CV mortality [17, 18]. A recent study by Li et al. indicated that serum Gal-3 levels were significantly higher in patients with angiographically proven coronary artery disease than in patients without CAD; as well as in patients with acute coronary syndrome (ACS) than in patients without ACS [19 − 16]. Gal-3 was an independent predictor of CAD, which was also associated with Syntax score complexity, and in the one-year follow-up MACE, the rate was significantly higher in patients with elevated Gal-3 [19, 20]. However, data on Gal-3 in patients with stable CAD are scarce and there are no studies investigating Gal-3 as a biomarker for MACE risk stratification in that subset of patients
Our study’s findings support previous findings [21, 22, 23] confirming the association of Gal-3 levels and the presence of significant atherosclerotic epicardial stenosis, indicating that it may serve as a biomarker of the existence of a major atherosclerotic process. However, there was no difference between PCI and CABG groups in Gal-3 levels. This can be explained by the fact that the decision on the treatment modality is quite subjective, it depends on the skill of the operator or invasive cardiologist as well as the available equipment. Therefore, a difference between these two groups could not be presumed because a patient undergoing PCI may have at least equally severe CAD as one undergoing CABG. Clinically, the exact role of Gal-3 is not fully elucidated when it comes to coronary heart disease, but the results of other authors confirm our results [19, 24]. The association of Gal-3 with higher hs-CRP and WBC count was also confirmed in the previous studies, indicating a role of an inflammatory process contributing to the formation of atherosclerotic plaque [19]. Gal-3 can instigate inflammation processes by increasing neutrophil superoxide production, stimulating respiratory chain outbreaks, and triggering oxidative stress reactions, increasing ox-LDL uptake by macrophages, vascular endothelial cells, and smooth muscle cells, promoting atherosclerosis [25].
The use of the Syntax score has a prognostic significance and serves as a tool for objectifying the complexity of coronary lesions, depending on their number and extensiveness, contributing to treatment decision-making [26]. In our study, we confirmed the correlation between serum levels of Gal-3 and Ss I. The strongest association of Ss I with GAL-3 was observed in the group of subjects with the most complex lesions, Ss > 33. Similar results were demonstrated by Aksan et al. [18], but after adjustment for other risk factors, Ss did not prove to be an independent risk factor for the severity of lesions. On the other hand, we have avoided possible confounding factors by including a specific population without major risk factors and with no in-between group differences. Turan et al., along with other authors, have shown that Gal-3 was independently associated with Ss [27, 28]. Similar results were obtained when comparing serum Gal-3 levels with the number of vascular lesions. The highest level of Gal-3 was found in three-vessel disease, just as in the Ss > 33 group of subjects. As patients with reduced LV fraction, and significant renal impairment, were excluded from the study, it was expected that patients with lower Ss and fewer affected vessels would have lower Gal-3 values. Our findings support results from other studies reporting that patients with three-vessel disease had higher levels of Gal-3 than patients with 1- or 2-vessel disease [21, 22].
Patients with chronic coronary syndrome often develop acute coronary syndrome and other adverse events (occurrence of atrial fibrillation or heart failure) despite optimal drug therapy and nonpharmacological measures. It is necessary to identify patients from this group who are at the highest risk for MACE and who require additional intervention (PCI or CABG) in addition to optimal drug therapy. In one study including patients with heart failure, the cut-off value of Gal-3 was 17.8 ng/mL, with values < 17.8 ng/mL, 17.8–23.9 ng/mL, and > 23.9 ng/mL set as low, moderate, and high risk, respectively, for MACE [12]. In our study, the arithmetic means of Syntax I was highest at high-risk Gal-3 levels. In addition, a significant correlation between Ss I and Gal-3 levels was also confirmed. Therefore, we could speculate that Gal-3 levels in combination with Ss could serve as a predictor of MACE in this subset of patients and influence therapeutic decisions.
Galectin-3 as a macrophage/endothelial derivative with its role in the atherosclerotic-inflammatory process has not been fully elucidated. It is known that patients with ACS have higher Gal-3 levels than patients with stable coronary artery disease or without coronary artery disease [19]. Moreover, elevated Gal-3 levels increase the risk of plaque destabilization and the occurrence of ACS [19, 28]. For this reason, patients with stable CAD, such as those included in our study, who have high Gal-3 levels in addition to optimal drug therapy that includes statins, could be classified as high-risk patients. It is also known that statins can affect Gal-3 and thus prevent the occurrence of MACE [29, 30]. The observed association between Gal-3 and Syntax score suggests that patients with more complex and multiple lesions are at higher risk for adverse events. Other authors reported similar findings [18].
Gal-3 could be an additional marker for assessing the presence of significant coronary disease as well as a predictor of adverse cardiovascular events. We aimed to study a highly selected group of patients diagnosed with CAD only, without additional factors that might have an impact on serum Gal-3 levels. Patients in daily clinical practice are more complex and often have CAD, arterial hypertension, heart failure, diabetes, and CKD, so elevated Gal-3 levels may have an even greater significance in this group of patients. In addition to the importance of Gal-3 as a diagnostic and prognostic biomarker for atherosclerotic disease and heart failure, Gal-3 may also be a potential target for pharmacological treatment to inhibit inflammatory and fibrotic tissue processes.
The main limitation of this study is the relatively small number of subjects since this was a single-center retrospective cohort study. Further prospective studies including a larger sample size monitoring the outcomes should be conducted to explore the prognostic value of Gal-3 in patients with stable CAD. In addition, it would be interesting to include subjects with non-obstructive coronary heart disease and coronary artery stenosis < 50%. However, one of the main strengths of our study is the recruitment of a patient population with “pure” CAD and no other significant comorbidities that could affect Gal-3 levels. In addition, there were no significant differences in baseline characteristics between the groups thus avoiding potential confounding factors.