Discussion
Even though MI has been associated with both hsCRP as well as IL-6,
albeit to a lesser extent, it has been challenging to establish the
direct role of inflammatory cytokines in MI. Nonetheless, a few studies
have implicated the IL-6 pathway in the pathogenesis of MI and other
heart diseases. According to the present study results, both the IL6 and
CRP levels were higher in MI patients than in healthy controls.
Additionally, CRP was significantly correlated with BMI and waist
circumference. Few studies have also demonstrated that CRP and IL-6 are
significantly associated with adverse cardiovascular
events.14-16 For example, aChinese study demonstrated
a significant correlation between both IL-6 and hsCRP and CVD risk
factors and mortality.17 In line with our study, Lai
et al. reported that the serum IL-6 concentrations in coronary disease
patients were substantially high (p<0.001) in contrast to
those in the control group.14 Another study reported
that the IL-6 levels were positively correlated to the risk factors for
CVD that cause inflammation and plaque formation, and therefore, IL-6
and CRP can be used as indicators of the prognosis of adverse cardiac
events.15 In another study, Velásquezet al. reported
that CRP and IL-6 had a significant association with hypertension,
diabetes, smoking, BMI, and age. The study concluded that elevations in
IL-6 levels were associated with the risk of MI.16
In a study on 44 STEMI patients, Wilkowska et al. reported elevated
levels of IL-6 in all the patients and observed that the IL-6 levels
were higher among depressed MI subjects than among non-depressed MI
subjects.18 In another study in the STEMI population,
the circulating levels of CRP and IL-6 were found to be increased,
especially in patients with a high peak of troponin
T.19 Although the biochemical parameters were deranged
in MI patients, these parameters were not significantly correlated with
IL-6 and CRP.
A study on 73 patients with acute MI (AMI) reported elevated IL-6 levels
in CAD patients than in the controls; further, the study concluded that
both the IL-6 and CRP levels were associated with AMI and cardiac
injury.20 In our MI patients, too, the CRP levels were
elevated compared with the controls (p<0.05) and were preceded
by an increase in IL-6 levels. Additionally, another study on the
association of CRP and IL-6 levels with the risk of death and
cardiovascular events in atrial fibrillation patients reported that the
IL-6 level was significantly correlated with vascular death, major
bleeding, i.e., hemorrhagic stroke, and thromboembolic outcomes, while
CRP was significantly associated with MI.21
IL-6 has been reported to be more strongly correlated with the risk of
cardiovascular mortality than CRP.22 Elevated IL-6
level is an important biomarker and powerful predictor for long-term
assessment of cardiovascular mortality risk in STEMI
patients.23 This is because serum IL-6 is the main
stimulator for acute phase hepatic response, which is linked with an
increase in blood viscosity as well as platelet count and activity.
Further, IL-6 slows down lipoprotein lipase activity as well as its
levels in plasma, thereby leading to an increase in the uptake of lipid
through macrophages.24 In addition to this,
circulating IL-6 stimulates the hypothalamic-pituitary-adrenal axis, and
the triggering of this axis is significantly correlated with central
obesity, insulin resistance, and hypertension, all of which are risk
factors for cardiovascular mortality.25 We also
observed that age in the control group was negatively correlated with
IL6, but there is no specific explanation for this correlation.
The findings discussed in this study support the assumption that IL-6
and CRP levels are involved in the MI, but their correlation with
cardiovascular biochemical risk factors is not found. It seems that IL6
and CRP are not involved in AMI’s mechanism via biochemical factors, but
these might play a pathogenic role in AMI by some other mechanism.