Correlation between prognosis and peripheral blood levels of NLRP3 and triglyceride-glucose index after myocardial ischemia-reperfusion injury

Abstract

Objective

We aim to investigate the association between prognosis and outcomes following myocardial ischemia-reperfusion injury, as well as peripheral blood levels of NLRP3 and the triglyceride-glucose index (TyG).

Methods

A total of 100 patients who underwent emergency coronary intervention following myocardial infarction confirmed by coronary angiography at our hospital between October 2021 and May 2023 were included in this study. Patients were stratified into two groups based on their prognoses: the control group (n = 73), which did not experience new myocardial infarctions or require hospitalization for heart failure or suffer sudden cardiac death post-interventional treatment; and the observation group (n = 27), which experienced one or more cardiovascular events post-treatment. Patient demographics were obtained from clinical records while biochemical analyses assessed peripheral blood triglycerides, blood glucose levels, and TyG index. Additionally, ELISA measurements determined levels of NLRP3 as well as inflammatory factors IL-6, TNF-α, and CRP in peripheral blood samples. Cardiac function was evaluated according to NYHA standards. Univariable Cox regression analysis identified factors influencing patient prognosis while Pearson correlation analysis examined relationships among prognosis, outcomes following myocardial ischemia-reperfusion injury, TyG index, and peripheral blood NLRP3.

Results

No significant differences were observed in the general characteristics between the two patient groups (P > 0.05). However, the observation group exhibited higher levels of peripheral blood triglycerides, blood glucose, and TyG index compared to the control group (P < 0.05). Additionally, levels of NLRP3 and inflammatory factors IL-6, TNF-α, and CRP were elevated in the observation group compared to the control group (P < 0.05). Cardiac function impairment was more pronounced in the observation group (P < 0.05). Notably, TyG index and peripheral blood NLRP3 demonstrated higher risk ratios compared to other biomarkers (P < 0.05), indicating their significance in prognosis and outcomes. Elevated levels of NLRP3 and TyG index were associated with poorer recovery of cardiac function, increased rehospitalization rates, and higher mortality (P < 0.05).

Conclusion

Elevated NLRP3 levels and an increased TyG index are strongly associated with impaired cardiac function and heightened risk of cardiovascular events. These findings suggest that these biomarkers may serve as crucial prognostic indicators following myocardial ischemia-reperfusion injury.

Introduction

Myocardial ischemia-reperfusion injury (MI/R) frequently occurs as a complication subsequent to the treatment of acute myocardial infarction (AMI). Despite the restoration of coronary artery blood flow, this phase can result in additional damage to myocardial cells, a phenomenon referred to as reperfusion injury [1,2,3]. The incidence of acute myocardial infarction (AMI) is notably high in China, serving as a primary cause of mortality in numerous regions. Despite reperfusion, the mortality rate remains elevated due to myocardial ischemia/reperfusion injury (MI/R), imposing substantial economic burdens on families and society. Hence, early identification of risk factors for MI/R and timely intervention are imperative for improving the prognosis of MI/R patients. The pathophysiological processes underlying reperfusion injury encompass oxidative stress, calcium overload, inflammatory responses, and mitochondrial dysfunction [1]. Therefore, understanding and assessing biomarkers of reperfusion injury are crucial for enhancing patient management and prognosis post-AMI.

The NLRP3 inflammasome, a pivotal complex governing immune and inflammatory responses, particularly in the context of cardiovascular disease, holds significant implications [4, 5]. During myocardial ischemia and reperfusion injury, the activation of the NLRP3 inflammasome promotes the secretion of pro-inflammatory cytokines, thereby exacerbating damage and fibrosis in cardiac tissue, consequently influencing cardiac repair and function [6, 7]. Accordingly, NLRP3 presents itself as a potential prognostic biomarker following myocardial infarction. Inflammasomes are multiprotein complexes primarily comprised of cytoplasmic pattern recognition receptors, associated proteins, and effector molecules that recognize and respond to inflammatory signals [8]. Assembly activation of the inflammasome can lead to self-cleavage and generation of active caspase-1 forms, which in turn facilitate the maturation and release of inflammatory factors such as interleukin-1 β (IL-1 β) and interleukin-18 (IL-18), thereby initiating an inflammatory response [8]. Furthermore, inflammasome activation can induce caspase-1-dependent cell pyroptosis, thus propagating the spread of inflammation. Inflammasomes are named based on the pattern recognition receptors that they engage with; among these, the NLRP3 inflammasome is currently the most extensively studied and comprehensively understood [9]. Recent research indicates that various risk factors for cardiovascular disease, including dyslipidemia, hypertension, kidney disease, hyperhomocysteinemia, obesity, diabetes mellitus, and metabolic syndrome can activate NLRP3 inflammasome signaling pathways leading to increased expression and release of pro-inflammatory mediators IL-1 β and IL-18 [10]. This process promotes atherosclerosis development while also impacting plaque stability-suggesting a pivotal role in cardiovascular disease pathogenesis. Interventions targeting NLRP3 inflammasome generation and activation hold promise for novel approaches to prevent and treat cardiovascular diseases [10]. The triglyceride-glucose index (TyG index) emerges as an additional biomarker intricately linked to cardiovascular health [11,12,13]. As a non-invasive indicator of insulin resistance, numerous studies have established its association with increased risk of cardiovascular disease [14, 15]. To date, no studies have investigated the correlation between NLRP3 inflammasome, TyG index, and the prognosis of acute myocardial infarction (MI/R).

Insulin resistance is not only associated with coronary artery disease, but also with the severity of reperfusion injury following myocardial infarction [16]. Therefore, the TyG index emerges as a crucial metric for assessing patient prognosis in MI/R. Given the potential link between NLRP3 and the TyG index with MI/R, this study aims to further explore the correlation between these biomarkers and patient prognosis following myocardial infarction through clinical investigation. Furthermore, it aims to evaluate the association between NLRP3 levels, the TyG index, and cardiac function recovery, as well as the long-term health outcomes of patients undergoing emergency coronary intervention after myocardial infarction confirmed by coronary angiography. Hence, we posit that a significant correlation exists between the NLRP3 inflammasome, TyG index, and the prognosis of acute myocardial infarction (MI/R), particularly with regard to mortality, disability, or cardiovascular adverse events.

MI/R poses a significant challenge in the treatment of myocardial infarction, encompassing the additional damage to myocardial cells incurred upon re-establishing blood supply following the removal of obstructed blood flow during myocardial infarction [17, 18]. This form of injury can precipitate a further decline in cardiac function and significantly impact the long-term prognosis and survival rates of patients [17]. Consequently, identifying biomarkers capable of predicting and monitoring the severity of this injury holds immense importance. NLRP3, an inflammatory complex central to the inflammatory response, particularly in heart diseases, exerts a profound influence on the extent and recovery process of myocardial injury by modulating the release of inflammatory factors [19]. Activation of NLRP3 is closely linked to myocardial cell death following acute myocardial infarction, with elevated expression levels often indicative of a poorer prognosis for cardiac events [20]. As such, NLRP3, functioning as an inflammatory marker, is deemed a promising target for evaluating the severity and prognosis of reperfusion injury post-myocardial infarction. The TyG index, serving as a non-invasive measure of insulin resistance, has garnered attention in recent years for its potential to predict cardiovascular disease risk [21]. Insulin resistance stands as a pivotal pathophysiological mechanism in cardiovascular diseases, and the TyG index has been shown to correlate with heightened risk of cardiovascular events by reflecting individuals’ metabolic status [22]. Monitoring the TyG index in patients with myocardial infarction enables physicians to gain deeper insights into their metabolic status and anticipate the risk of cardiac events, facilitating more targeted treatment and management strategies. Hence, investigating NLRP3 and the TyG index as biomarkers following MI/R not only advances our understanding of the intricate pathological processes post-myocardial infarction but also furnishes a critical clinical foundation for early identification of high-risk patients, optimization of treatment regimens, and enhancement of patient prognosis [22].

The findings of this study have the potential to assist clinicians in more accurately assessing the risk following myocardial infarction, thereby facilitating early intervention and reducing the incidence of adverse cardiovascular events.

Materials and methods

General information

Between October 2021 and May 2023, we enrolled 100 patients who underwent emergency coronary intervention following myocardial infarction confirmed by coronary angiography. Based on prognosis, patients were stratified into the control group (comprising individuals who did not experience new myocardial infarction, hospitalization for heart failure, or sudden cardiac death after interventional therapy; n = 73) and the observation group (comprising individuals who experienced one or more cardiovascular events post-treatment; n = 27). Cardiovascular events encompass myocardial ischemic incidents such as myocardial infarction or angina pectoris. The research protocol received approval from the author’s hospital’s relevant ethics review committee prior to commencement.

Inclusion criteria

The inclusion criteria were as follows: adults aged 18 or older, regardless of gender, with a diagnosis of acute myocardial infarction based on clinical and imaging data, who had undergone emergency coronary intervention within 72 h of myocardial infarction onset. In addition, patients were required to provide blood samples for biochemical index analysis before and after enrollment, as well as during follow-up. Written informed consent was mandatory for participation.

Exclusion criteria

Patients with severe liver dysfunction, such as cirrhosis, and severe renal insufficiency requiring dialysis, as well as those with chronic inflammation or immune diseases, were excluded from the study. Additionally, patients with a history of chronic heart failure, previous myocardial infarction, or heart surgery, along with those on long-term corticosteroid or non-steroidal anti-inflammatory drug therapy were also excluded. Patients who declined to provide informed consent were likewise excluded.

Metabolic index analysis

Patients were instructed to fast for a minimum of 8 h prior to testing in order to ensure the accuracy of the results. Blood samples were obtained from patients’ veins using EDTA anticoagulation tubes. Following collection, the samples underwent centrifugation to separate serum, which was subsequently frozen at -80 °C for future use. Triglyceride levels were measured using a triglyceride detection kit (A110-1) from the Nanjing Jiancheng Institute of Bioengineering, employing an enzymatic method that involved a color reaction at 37 °C for 10 min, with absorbance measured at 546 nm using a spectrophotometer. Glucose levels were determined utilizing a glucose detection kit (GOD-PAP, Beijing Lidman Biochemical Co., Ltd.) via the glucose oxidase method. The TyG index was calculated using the formula LN (triglyceride (mg/dL) × fasting blood glucose (mg/dL)/2), where the product of triglyceride and fasting blood glucose was divided by 2 and then its logarithm taken. This index served as an indicator for evaluating insulin resistance status in patients.

Enzyme-linked immunosorbent assay

The levels of NLRP3, IL-6, TNF-α, and CRP in the peripheral blood of patients were quantified using enzyme-linked immunosorbent assay (ELISA). Venous blood samples were collected from the patients and centrifuged in anticoagulant-containing tubes to obtain serum, which was then stored at -80 °C. Specific ELISA kits for NLRP3 (R&D Systems), IL-6 (American BD Company), TNF-α (Thermo Fisher Scientific Shier Technology), and CRP (Sigma-Aldrich) were selected, and all reagents were prepared according to the provided instructions. Standard and sample solutions were added to microplates precoated with specific antibodies, followed by plate sealing for incubation. After incubation, the microplates underwent washing with a solution to remove unbound substances. Substrate solution was subsequently added, followed by addition of a stop solution after incubation to induce a color reaction. Absorbance at 450 nm wavelength was measured using an enzyme-labeled instrument, and the concentration of the target protein in each sample was determined based on a standard curve.

Assessment of cardiac function grading

Cardiac function was assessed based on the New York Heart Association (NYHA) classification standard. Physicians engaged in a dialogue with patients, inquiring about their experiences of dyspnea, fatigue, or other symptoms related to heart disease during daily activities. Subsequently, patients were prompted to articulate their responses to mild to moderate intensity activities such as walking or climbing stairs. Cardiac function was then categorized into four levels based on the patient’s description and the physician’s observation: Class I indicates no activity restriction, Class II suggests mild activity limitation, Class III denotes significant activity impairment, and Class IV implies an inability to engage in any physical activity, potentially accompanied by symptoms at rest.

Statistical analysis

This study utilized SPSS 28.0 statistical software for data analysis. The measurement data was presented as “mean ± standard deviation” (± s), with intergroup comparisons conducted using one-way ANOVA and t-tests. Counting data was expressed as a percentage (%), and intergroup comparisons were made using χ2 analysis. Univariable Cox regression and Pearson correlation analysis were employed to analyze the relationship between prognosis and peripheral blood levels of NLRP3 and triglyceride glucose index following myocardial ischemia-reperfusion injury. A significance level of P < 0.05 was used to indicate statistical significance.

Results

Comparison of general patient data

The patients’ ages ranged from 42 to 68 years, with an average age of 53.35 ± 5.24 years. Of the total, 68 were male and 32 were female. According to clinical records, in the control group, the male-to-female ratio was 50:23, with an average age of 59.38 ± 6.54 years and an average BMI of 22.35 ± 1.62 kg/m². Among them, there were four cases of diabetes and seven cases of hypertension reported. Additionally, there were thirteen cases of smoking and eleven cases of alcohol consumption within the last five years documented for this group. In contrast, in the observation group, the male-to-female ratio was 18:9, with an average age of 63.55 ± 5.26 years and an average BMI of 23.44 ± 1.75 kg/m² recorded for this cohort. One case had diabetes in this group while four had hypertension; additionally, there were four cases reporting smoking and three reporting alcohol consumption within the last five years. No significant differences in general patient data between the two groups were observed (P > 0 0.05). The detailed demographic data are presented in Table 1.

Table 1 Demographical data of patients ($\bar x \pm s$)

Metabolic index analysis

Triglyceride levels, fasting plasma glucose (FPG) levels, and the TyG index in patients’ peripheral blood were evaluated through biochemical analysis. It was noted that these parameters were significantly elevated in the observation group compared to the control group (P < 0.05). (Fig. 1; Table 2)

Fig. 1

Biochemical analysis of metabolic indicators

Table 2 Biochemical analysis of metabolic indicators ($\bar x \pm s$)

Inflammatory metabolism analysis

The levels of NLRP3, the inflammatory factors IL-6, TNF-α, and CRP in the peripheral blood of patients were assessed using ELISA. It was observed that these levels were significantly higher in the observation group compared to the control group (P < 0.05). (Fig. 2; Table 3)

Fig. 2

Analysis of inflammatory metabolism

Table 3 Analysis of inflammation metabolism ($\bar x \pm s$)

Grading analysis of patients’ cardiac function

According to the NYHA standard, the patients’ cardiac function was evaluated. In the control group, 55 cases were classified as NYHA Class I, 14 cases as NYHA Class II, and 4 cases as NYHA Class III. In the observation group, there were 3 cases classified as NYHA Class I and 18 cases as NYHA Class II. The degree of impairment in cardiac function was significantly higher in the observation group compared to the control group (P < 0.05). (Table 4)

Table 4 Analysis of patients’ cardiac function classification ($\bar x \pm s$)

Univariable Cox regression

Univariable Cox regression analysis was utilized to evaluate the prognostic factors of patients. Biomarkers, including triglyceride levels, fasting plasma glucose (FPG) levels, TyG index, peripheral blood NLRP3 levels, IL-6, TNF-α, and CRP were associated with prognosis following MI/R. Among these biomarkers, the TyG index and peripheral blood NLRP3 exhibited higher hazard ratios compared to others (P < 0.05), indicating their significance in prognosis. (Table 5)

Table 5 Univariate Cox regression analysis ($\bar x \pm s$)

Pearson correlation analysis

Pearson correlation analysis was performed to evaluate the association between prognosis and the TyG index as well as peripheral blood NLRP3 levels following MI/R. Elevated levels of NLRP3 and the TyG index were observed to be significantly correlated with poorer recovery of cardiac function, increased rates of readmission, and higher mortality (P < 0.05). (Table 6)

Table 6 Pearson correlation analysis ($\bar x \pm s$)

Discussion

In this study, we investigated the association between prognosis and peripheral blood levels of NLRP3 and the TyG index following MI/R. Analysis of data from 100 patients with myocardial infarction who underwent emergency coronary intervention revealed significantly elevated levels of triglycerides, fasting plasma glucose (FPG), and the TyG index in the observation group (comprising patients with cardiovascular events) compared to the control group. Furthermore, levels of inflammatory markers NLRP3, IL-6, TNF-α, and CRP were notably increased in the observation group. The escalation of these biomarkers is closely associated with worsened cardiac function and poorer prognosis. Measurement of biomarkers such as NLRP3, IL-6, TNF-α, and CRP holds profound significance in the study of MI/R, providing direct evidence regarding the degree of inflammatory response; particularly crucial for evaluating reperfusion injury post-myocardial infarction. Elevated levels of these inflammatory factors are closely linked to the severity of myocardial injury and worsened prognosis [23, 24]. NLRP3, as a constituent of the inflammatory complex, can initiate inflammation and cell necrosis following myocardial ischemia, exacerbating cardiac injury by promoting the release of inflammatory cytokines, particularly IL-1β. Therefore, elevated NLRP3 expression often indicates severe MI/R [25]. Remarkably, the observation group, consisting of patients who experienced one or more cardiovascular events, exhibited significantly higher levels of NLRP3 compared to the control group, further emphasizing NLRP3’s potential as an independent predictor of poor prognosis. Additionally, other inflammatory markers such as IL-6 and TNF-α play crucial roles in myocardial injury and repair. IL-6, a multifunctional inflammatory cytokine, activates various immune cells and promotes inflammatory responses. TNF-α, a potent inflammatory mediator, initiates and exacerbates myocardial cell apoptosis [26]. Meanwhile, as a sensitive acute phase protein, the elevation in CRP levels signifies the presence and activity of inflammatory responses within the body. The TyG index, functioning as an indicator of individual insulin resistance and metabolic status, is associated with heightened cardiovascular risk. Post-myocardial infarction, metabolic disturbances may exacerbate oxidative stress and inflammatory responses in the heart, thereby impacting long-term prognosis. Notably, the significantly elevated TyG index in the observation group emphasizes the close link between metabolic disorder and increased risk of cardiovascular adverse events. This discovery underscores the importance of monitoring and intervening in post-myocardial infarction metabolic status. By assessing biomarkers related to inflammation and metabolism, it is possible to more effectively evaluate the prognostic risk of patients with myocardial infarction [27]. These biomarkers not only contribute to the understanding of the pathological mechanism of MI/R, but also provide clinical guidance, thereby facilitating the development of more personalized and targeted treatment strategies.

Employing the NYHA standard for evaluating patients’ cardiac function, our study reveals a significant correlation between the degree of cardiac function impairment and NLRP3 levels and the TyG index, providing insight into the extent of inflammatory response and metabolic dysfunction in individuals with cardiac insufficiency. Specifically, individuals with diminished cardiac function frequently exhibit heightened NLRP3 expression and more pronounced insulin resistance, potentially exacerbating their cardiac condition and precipitating further cardiovascular events and increased mortality. Univariable Cox regression analysis further corroborated the independent correlation between NLRP3 and the TyG index and poor prognosis following MI/R. This analysis not only reaffirms the role of these biomarkers as independent prognostic indicators but also underscores their clinical significance. Importantly, even after adjusting for variables such as age, gender, known history of heart disease, and other potential risk factors, elevated NLRP3 levels and the TyG index remained predictive of a worse prognosis. Vigilant monitoring of these biomarkers is crucial for clinicians to facilitate early intervention and devise effective treatment strategies. Regular monitoring of NLRP3 and the TyG index in patients with myocardial infarction allows clinicians to evaluate the risk of recurrent heart events, facilitating timely implementation of targeted interventions such as reinforcing metabolic control and administering anti-inflammatory treatment. Furthermore, these biomarkers’ levels can serve as benchmarks for assessing therapeutic efficacy, assisting clinicians in refining treatment plans to optimize clinical outcomes for patients [28]. Incorporating NLRP3 and the TyG index into standard cardiovascular disease management and risk assessment processes improves the monitoring and control of patients’ health status, potentially enhancing survival rates and quality of life. These findings not only advance our understanding of the complex mechanisms underlying MI/R but also lay the groundwork for future research, guiding the development of innovative therapeutic strategies, particularly in the field of inflammation and metabolism regulation.

The primary focus of this study is to elucidate the intricate relationship between NLRP3 inflammasome, TyG index, and prognosis of acute myocardial infarction (MI/R), particularly in terms of mortality, disability, or cardiovascular adverse events. The principal limitation and shortcoming of this study lies in the relatively small number of included research cases, leading to a lack of regional representativeness in the research results.

In conclusion, the findings of this study emphasize that post-MI/R patients with elevated NLRP3 and TyG index levels exhibit a poorer prognosis, characterized by exacerbated cardiac function impairment and heightened risk of cardiovascular events. These results underscore the crucial roles of NLRP3 and the TyG index as potential biomarkers for adverse outcomes following MI/R, highlighting the significance of clinical monitoring of these indices to provide essential information for risk assessment and treatment decision-making in patients.