Diabetes concomitant to aortic stenosis is associated with increased expression of NF-κB and more pronounced valve calcification

Abstract

Aims/hypothesis Type 2 diabetes has been demonstrated to predispose to aortic valve calcification. We investigated whether type 2 diabetes concomitant to aortic stenosis (AS) enhances valvular inflammation and coagulation activation via upregulated expression of NF-κB, with subsequent increased expression of bone morphogenetic protein 2 (BMP-2). Methods In this case–control study, 50 individuals with severe isolated AS and concomitant type 2 diabetes were compared with a control group of 100 individuals without diabetes. The median (IQR) duration of diabetes since diagnosis was 11 (7–18) years, and 36 (72%) individuals had HbA1c ≥48 mmol/mol (≥6.5%). Stenotic aortic valves obtained during valve replacement surgery served for in loco NF-κB, BMP-2, prothrombin (FII) and active factor X (FXa) immunostaining. In vitro cultures of valve interstitial cells (VICs), isolated from obtained valves were used for mechanistic experiments and PCR investigations. Results Diabetic compared with non-diabetic individuals displayed enhanced valvular expression of NF-κB, BMP-2, FII and FXa (all p ≤ 0.001). Moreover, the expression of NF-κB and BMP-2 positively correlated with amounts of valvular FII and FXa. Only in diabetic participants, valvular NF-κB expression was strongly associated with serum levels of HbA1c, and moderately with fructosamine. Of importance, in diabetic participants, valvular expression of NF-κB correlated with aortic valve area (AVA) and maximal transvalvular pressure gradient. In vitro experiments conducted using VIC cultures revealed that glucose (11 mmol/l) upregulated expression of both NF-κB and BMP-2 (p < 0.001). In VIC cultures treated with glucose in combination with reactive oxygen species (ROS) inhibitor (N-acetyl-l-cysteine), the expression of NF-κB and BMP-2 was significantly suppressed. A comparable effect was observed for VICs cultured with glucose in combination with NF-κB inhibitor (BAY 11–7082), suggesting that high doses of glucose activate oxidative stress leading to proinflammatory actions in VICs. Analysis of mRNA expression in VICs confirmed these findings; glucose caused a 6.9-fold increase in expression of RELA (NF-κB p65 subunit), with the ROS and NF-κB inhibitor reducing the raised expression of RELA by 1.8- and 3.2-fold, respectively. Conclusions/interpretation Type 2 diabetes enhances in loco inflammation and coagulation activation within stenotic valve leaflets. Increased valvular expression of NF-κB in diabetic individuals is associated not only with serum HbA1c and fructosamine levels but also with AVA and transvalvular gradient, indicating that strict long-term glycaemic control is needed in AS patients with concomitant type 2 diabetes. This study suggests that maintaining these variables within the normal range may slow the rate of AS progression. Graphical abstract

Diabetes mellitus as a risk factor for aortic stenosis: from new mechanisms to clinical implications

“…Similar results were obtained by Larsson et al [8], who have shown that type 2 DM was associated with a 34% increased risk of AS and Martinsson et al [51], who have reported DM as an independent risk factor for AS development. On the other hand, Testuz et al [9] have failed, during a 3-year follow-up, to observe the association between AS progression and metabolic syndrome or diabetes; however, in this study only fasting glucose levels were analyzed while it has been shown that long-term glycemic control may be of key importance [10,11].…”

“…Interestingly, both the quantity of fibrin and the degree of valve calcification correlated with factor (F)XIII expression derived mainly from the alternatively activated macrophages recruited to the valve leaflets [29]. Recently, it has been shown that VICs are also able to express prothrombin and active FX [11]. Moreover, growing evidence indicates that AS patients are characterized by impaired clot susceptibility to fibrinolysis [33,34], the process closely regulated by specific inhibitors, such as plasminogen activator inhibitor type-1 and thrombin-activatable fibrinolysis inhibitor [35].…”

“…AGEs are a heterogonous group of proteins or lipids irreversibly glycated by the attachment of reducing sugars onto the free amino groups. AGEs modify tissue structure and function through cross-linking of intra-/extracellular matrix proteins or binding to the cell surface receptor for AGEs (RAGE), which affects multiple cellular processes (Table 2) [11,51,53,54,56,[58][59][60][61][62][63][64][65][66][67]. Ex-posure to increased blood levels of glucose in DM rapidly accelerates AGEs formation [68].…”

“…In patients with the bicuspid aortic valve, which is the most common congenital heart disease occurring in 1%-2% of the population, AS development occurs statistically more frequently [2]. Growing evidence indicates that diabetes mellitus (DM) can increase the risk of AS development and the rate of AS progression [4][5][6][7][8][9][10][11]. The diagnosis of AS is based on echocardiographic assessment.…”

“…Patients with DM are at 2-to 4-fold higher cardiovascular risk as compared to non-diabetic individuals, and cardiovascular disease (CVD) remains the leading cause of mortality in patients with this condition [16,17]. DM accompanied by inflammation is thought to be involved in the pathophysiological mechanism of atherosclerosis and is an important factor enhancing this disease [11]. Based on similarities between AS and atherosclerosis one might suspect the major importance of DM on AS progression; however, the mechanism underlying the cross-talk between DM and AS is not fully understood to date.…”