Introduction:

Damage to the coronary microvascular endothelial cell (CMVEC) glycocalyx has been implicated in cardiometabolic disease and may contribute to microvascular dysfunction. The glycocalyx is a complex and dynamic structure composed of proteoglycans and glycoproteins and plays a key role in regulating vascular permeability. Given the sensitivity of the myocardium to alterations in microvascular barrier function, disruption of the glycocalyx may be linked to impaired cardiac relaxation. However, its relationship with diastolic dysfunction across cardiometabolic conditions and its responsiveness to therapeutic intervention remain incompletely understood.

We aimed to determine whether glycocalyx integrity is associated with diastolic function in experimental models of cardiometabolic disease and to assess whether pharmacological interventions that preserve the glycocalyx are accompanied by improvements in cardiac function.

Methods:

In vitro: Human CMVEC were treated with 10ng/ml of TNF-α for 6 hours and treated with the MMP2/9-specific inhibitor, SB-3CT (10mg/ml) or finerenone (3mM). Quantitative PCR arrays, immunofluorescence, and ELISAs were used for investigation.

In vivo: Type 1 diabetes was induced in male FVB mice by injection of streptozotocin (STZ). Diabetic mice were treated with SB-3CT (10mg/kg), daily for 2 weeks from 7 weeks post STZ. In a second model, aged female mice (~17–20 months), were fed on a high fat diet or control low fat diet for 12 weeks. After 8 weeks, mice were given finerenone at 2 mg/kg/day orally for 4 weeks.  Echocardiography was utilised to assess diastolic function. Lectin staining was conducted on heart tissue to give an indication of glycocalyx depth.

Results:

TNF-α significantly increased MMP-9 and heparanase mRNA expression (p<0.01–0.001) and promoted shedding of syndecan-4 (SDC4) and glycosaminoglycans into the conditioned media (p<0.05–0.001), alongside reduced cell surface SDC4 expression (p<0.05). Treatment with the MMP-2/9 inhibitor SB-3CT attenuated SDC4 shedding and restored surface expression (p<0.01), while both SB-3CT and finerenone reduced glycosaminoglycan shedding (p<0.05–0.01). Finerenone also significantly suppressed TNF-α-induced heparanase expression (p<0.001), supporting a protective effect on glycocalyx integrity under inflammatory conditions.

In vivo, streptozotocin-induced diabetic mice exhibited diastolic dysfunction, evidenced by a reduced E/A ratio (n=10 for controls and 5 for diabetes; control: 2.0±0.12 vs diabetes: 1.5±0.09; p<0.05), accompanied by reduced glycocalyx depth (n=5, control: 279.4±11.7 nm vs diabetes: 158.7±30.2 nm; p<0.05), increased cardiac MMP-9 activity, and enhanced vascular permeability as indicated by albumin extravasation. Treatment with SB-3CT restored glycocalyx depth (n=5 for SB-3CT + diabetes; 270.3±31.3 nm; p<0.05), improved diastolic function (E/A: 2.2±0.15; p<0.05), reduced MMP-9 activity (p<0.01), and decreased albumin leakage. Glycocalyx depth was positively correlated with diastolic function, while cardiac MMP-9 activity was negatively correlated (p<0.05).

In a complementary model, aged female mice subjected to high-fat diet feeding developed diastolic dysfunction, which was significantly improved following finerenone treatment (n=6 for all groups, p<0.05) without alterations in blood pressure.

Conclusion:

Glycocalyx integrity is closely associated with diastolic function across distinct cardiometabolic models and is responsive to pharmacological intervention. These findings support the glycocalyx as a central marker of coronary microvascular health and a potential therapeutic target in diastolic dysfunction.