Soluble Corin Predicts the Risk of Cardiovascular Disease

Background As a key enzyme of the natriuretic peptides system, corin may participate in the development of cardiovascular disease (CVD). Its level in circulation predicted CVD recurrence in patients with myocardial infarction and heart failure, but no study examined this prediction in general populations. Objectives This study sought to examine the prospective association between corin and CVD in a community-based population of Chinese adults. Methods The Gusu cohort included 2,498 participants (mean age 53 years, 39% men) who were free of CVD at baseline. Serum corin was measured by enzyme-linked immunosorbent assay kits at baseline and CVD events were followed every 2 years for all participants. A competing-risks survival regression model was used to examine the association between serum corin and CVD. Results During 10 years of follow-up, 210 participants developed CVD including 88 stroke events. A higher serum corin (after log-transformation) at baseline was significantly associated with an increased risk of CVD (HR: 1.88; P = 0.019) and stroke (HR: 3.19; P = 0.014). Analysis using categorical serum corin (in quartiles) showed that participants in the highest quartile had a 62% and 179% increased risk for CVD (HR: 1.62; P = 0.024) and stroke (HR: 2.79; P = 0.004), respectively, compared with those in the lowest quartile. We did not find a significant association between serum corin and coronary heart disease. Conclusions A higher serum corin at baseline predicted a higher risk of CVD events and stroke, but not coronary heart disease, in Chinese adults, independent of conventional risk factors. Serum corin may be a predictor for stroke but the underlying mechanism needs further investigation.

H uman corin, a type II transmembrane serine protease highly expressed in cardiac myocytes, 1 is the physiological activator of atrial natriuretic peptide (ANP) and can also activate B-type natriuretic peptide (BNP), both of which are the main constitutes of the natriuretic peptides system that maintains blood pressure homeostasis through natriuresis, diuresis, and vasodilatation. 2 As illustrated in the Central Illustration, corin may play a switching role in the natriuretic peptides system, 3 thereby delivering an important impact on the homeostasis of the cardiovascular system. For example, animal studies found that transgenic mice with overexpression of corin had reduced myocardial fibrosis, 4 and mice with the corin gene knockout developed cardiac hypertrophy and heart failure. 5 In humans, single-nucleotide variations in the CORIN gene that encodes corin protease have been associated with hypertension. [6][7][8] In published reports, corin protein was found to be shed from the cardiac myocyte surface by hydrolysis and autocleavage physiologically. 9 Shed corin molecules could apparently enter the circulation and were found to possess the same activity in activating ANP as the membrane-bound corin was. 10 . Although the correlation between levels of corin in the circulation and expression on membrane-anchored corin is unclear, some small clinical studies have found that soluble corin was associated with cardiovascular disorders, such as atrial fibrillation, 11 heart failure, 12 and myocardial infarction. 13 Our previous community-based casecontrol study also found a significant association between serum soluble corin and stroke. 14   with heart failure, 15 acute myocardial infarction, 16 and coronary heart disease (CHD), 17  All the samples were processed in a duplicate assay      Table 2). Their baseline median levels of serum corin are shown in Figure 1. The cumulative incidence of cardiovascular disease (CVD) was 6.08%, 7.87%, 9.25%, and 10.43% in participants with increasing quartiles of serum corin at baseline, respectively, with a significant group difference (P ¼ 0.038 for the Fine-Gray test).
Chen et al

Corin and Cardiovascular Events
A U G U S T 2 0 2 2 : 4 9 0 -5 0 1 Compared with participants who remained free of CVD pg/mL) had a significantly increased level of serum corin at baseline (P < 0.001).
The cumulative incidence of CVD was 6.08%, 7.87%, 9.25%, and 10.43% in participants with increasing quartiles of serum corin at baseline, respectively, with a significant group difference (P ¼ 0.038 for the Fine-Gray test) ( Figure 2). After further adjustment for conventional risk factors, the association between serum corin at baseline and CVD was also observed. As shown in Table 3, the regression using log-corin as the independent variable revealed that a higher level of serum corin was significantly associated with an increased risk of CVD P ¼ 0.004) higher risk of incident stroke ( Table 2). As for specific subtype of stroke, the association between serum corin and ischemic stroke persisted (Supplemental Table 1). The impact of serum corin level at baseline on the risk of stroke is also visualized in  4.64%, 5.94%, 6.70%, and 6.26%, respectively, but without statistically significant difference (P ¼ 0.451 for the Fine-Gray test) (Supplemental Figure 1). Univariate analysis found that serum corin at baseline was significantly associated with a higher risk of CHD (HR: 1.86; P ¼ 0.011), but this association did not survive after adjusting for conventional risk factors ( Table 3).
RESULTS OF SENSITIVITY ANALYSIS. Subgroup analysis by sex found that the associations between serum corin and CVD events persisted in men rather than in women but without significant heterogeneity (Supplemental Table 2 Figure 2). We did not find significant association between serum corin and allcause death ( Table 3).

DISCUSSION
In the community-based prospective longitudinal study of middle-aged and elderly Chinese adults, we examined for the first time the prospective association between soluble corin at baseline and the future risk of CVD in a general population. We found that a higher level of serum corin at baseline predicted a higher risk of incident CVD during a 10-year followup. This association was independent of conventional risk factors, including behavioral and metabolic factors. As for specific CVD events, serum corin at baseline was also significantly associated with an increased risk of stroke, rather than CHD, during follow-up. The level of circulating corin could be a predictor of the risk of stroke. These findings suggest that corin may play a considerable effect on the cardiovascular system and may therefore serve as a candidate risk factor or a potential therapeutic target for stroke. Nevertheless, the causal effect of corin on stroke development still needs more evidence from trials.
In the present study, the serum corin levels of each participant were measured using commercial enzyme-linked immunosorbent assays, which are also widely used in other studies. 12,[22][23][24][25] As an activator of the natriuretic peptides system, corin plays a critical role in maintaining blood pressure hemostasis through natriuresis, diuresis, and vasodilatation. 2 Therefore, elevated blood pressure may need more corin to reduce the levels to normal. In our study, there were 1,109 hypertensive participants (44%) and serum corin was significantly higher in participants with hypertension than in those without. 19 However, the range of serum corin levels (373.39-2,833.35 pg/mL) detected in nonhypertensive individuals in our study was similar to that (256-2,590 pg/mL) in previous studies. 20 In line with our study, the identified association between serum corin and CVD has also been suggested by other studies. For example, a basic study reported an up-regulated expression of corin in human endothelial cells with atherosclerosis. 26 In animals, the expression of the corin gene was upregulated in hypertrophic cardiomyocytes and failing myocardium in mice. 27 Plasma corin level was significantly increased in mice with myocardial infarction 28 and heart failure, 29 compared with in their wild littermates. In humans, some single-

Corin and Cardiovascular Events
A U G U S T 2 0 2 2 : 4 9 0 -5 0 1 nucleotide variations of the coding gene of corin, such as rs111253292, rs3749585, and rs2271037, have been associated with the susceptibility of hypertension, which is the leading contributor of CVD. 6,8,30,31 Furthermore, corin levels in circulation have also been associated with some cardiovascular disorders.
For instance, a small clinical study including 141 patients with atrial fibrillation and 127 matched control subjects demonstrated that plasma corin was significantly increased in patients with atrial fibrillation. 11 Another study found a significant association between plasma corin and infarct size in 55 patients with myocardial infarction. 32 A recent prospective cohort study including 1,009 patients with heart failure found that a higher level of soluble corin and neprilysin at baseline was significantly associated with a higher risk of cardiovascular death and rehospitalization during 8 years of follow-up. 22 Also, a high level of serum PCSK6, an upstream activator of corin, was found to be associated with an increased risk of CVD during a median follow-up of 2 years in 565 patients who had undergone coronary angiography. 17 In addition, circulating corin was also significantly increased in the pregnant woman with hypertension and preeclampsia. [33][34][35] In the Gusu cohort, our group has examined and found that serum corin was significantly and positively associated with major risk factors of CVD, such as hypertension, 19 diabetes, 36,37 ) dyslipidemia, 38 and obesity. 39 In the current study, we further examined whether serum corin at baseline could predict the future risk of CVD in the Gusu cohort. To the best of our knowledge, this is the first prospective cohort study to examine the association between corin and CVD in a general population. Our findings enrich the published data on the potential role of corin in the cardiovascular system. The cumulative incidence of stroke was 1.92%, 2.89%, 3.51%, and 5.78% in participants with increasing quartiles of serum corin at baseline, respectively, with a significant group difference (P ¼ 0.002 for the Fine-Gray test).
Together with prior studies, the significant prospective association observed in our study increases the possibility that corin might be a candidate risk factor and a therapeutic target for cardiovascular disorders.
In contrast, a negative association between corin and CVD has also been observed in prior studies. For example, transgenic mice with overexpression of corin had a lower risk of myocardial fibrosis and heart failure. 4,40 Mice with the corin gene knockout developed hypertension and cardiac hypertrophy. 5 Casecontrol studies found that circulating corin was lower in patients with stroke, 14 myocardial infarction, 13 and heart failure 12,41 than in their matched healthy control subjects. Prospective cohort studies found that a lower level of plasma corin at admission was associated with a higher risk of CVD during a follow-up of 5 years in patients with chronic heart failure 15 and acute myocardial infarction. 16 Another prospective study including 565 patients undergoing coronary angiography did not find a significant association between corin and CVD. 17 The reasons for the inconsistent findings are unclear. One of the possible explanations could be the varied populations studied: most of the prospective cohort studies included patients who had already suffered from CVD, whereas our study included community members who were free of CVD at baseline. As an activator of ANP and BNP, corin acts as an upstream regulator of the natriuretic peptides system. This system plays a critical role in maintaining salt-water balance and blood pressure through natriuresis, diuresis, and vasodilation in response to cardiac output overload. obesity, 39 and metabolic syndrome. 42 In such conditions, a higher level of corin at baseline may indicate a higher risk of CVD in the future. On the other hand, the expression of corin may not increase in the patients who were decompensated and who already had a myocardial infarction and heart failure. The activity of corin on activation of ANP has been reduced in patients with heart failure. 18,29 Therefore, a negative association between corin and the recurrence of CVD may be observed in a cohort of patients with myocardial infarction and heart failure, as discussed. 15,16 Indeed, mountains of evidence have demonstrated that higher natriuretic peptides predicted a higher risk of cardiovascular events. [43][44][45] Higher levels of natriuretic peptides require more corin protease to activate them because corin is the physical activator of ANP. These findings further support our results that a higher level of serum corin predicts a higher risk of future incidence of CVD for participants who are free of CVD at baseline.
In addition to population studies, basic experiments are also encouraged to deepen our understanding of the role of corin in the cardiovascular system. Corin has been found to play critical roles in the natriuretic peptides system by activating ANP and BNP, 3 energy metabolism by degrading agouti-related protein, 46 and suppression of oxidative stress. 47 These known mechanisms suggest that the function of corin is complicated and it may participate in the development of CVD through multiple pathways.
Whether corin possesses any more biological functions that may affect the cardiovascular system is still

Corin and Cardiovascular Events
A U G U S T 2 0 2 2 : 4 9 0 -5 0 1 yet to be answered. A better understanding of the underlying molecular mechanisms would undoubtedly promote the clinical translation of corin shortly.
To the best of our knowledge, our study represents the first to examine the prospective association between baseline serum corin and CVD incidence in a general population who were free of CVD at baseline.
The strengths of our study include the prospective longitudinal study design with 10 years of follow-up, the comprehensive adjustment of conventional risk factors, and the application of a competing-risks survival regression model to account for the bias introduced by deaths from noncardiovascular causes.
STUDY LIMITATIONS. First, as an observational study, we cannot eliminate residual confounding.
The causality between serum corin and CVD is not established and needs further evidence from clinical trials. However, our prospective design conformed the temporality that elevated corin preceded the incidence of CVD and thereby increasing the possibility of the causality. Second, our study mainly included middle-aged and elderly Chinese adults, the generalization of our results to younger and other ethnic populations would be cautious. Third, we did not have data on natriuretic peptides in our study and cannot determine whether and how serum corin was associated with natriuretic peptides. However, 2 studies reported that serum corin was associated with ANP and BNP levels assessed by their equimolarly cleaved forms N-terminal proANP 48 and N-terminal proBNP, 49 respectively. These results increased the possibility that corin may play a role in cardiovascular health. Fourth, small clinical studies have found that soluble corin was associated with atrial fibrillation 11 and heart failure. 12 These disease states may therefore affect the association between serum corin and CVD. Unfortunately, we did not collect data on atrial fibrillation and heart failure at baseline.
Whether and how these disease states affect our results is unclear.

CONCLUSIONS
Our study demonstrated that higher serum corin at baseline predicted a higher risk of CVD events and stroke, but not CHD, in an unselected community-based population of Chinese adults, independent of conventional risk factors.