Loss of Tight Junction Integrity Drives Increased Intestinal Permeability in Experimental HFpEF

Background: Heart failure with preserved ejection fraction (HFpEF) affects half of the 6.7 million HF patients in the U.S. and currently lacks effective treatments. Evidence implicates the gut–heart axis in HFpEF, where increased intestinal permeability allows microbial translocation that amplifies systemic inflammation and worsens cardiac dysfunction. Methods: HFpEF was induced in 8-week-old male C57BL/6J mice using 1% NaCl in drinking water, subcutaneous deoxycorticosterone pellets (0.83 mg/day), and high-fat diet (60% kcal fat) for 15 weeks. Controls received chow and regular water. Cardiac function was assessed by echocardiography. Ileal morphology was evaluated by H&E. Intestinal permeability was measured 4 h after FITC-dextran gavage. Ileal expression of tight-junction genes and zonulin was quantified by qRT-PCR. Results: The 15-week HFpEF model recapitulates key clinical features: ejection fraction (60±2 vs. 57±2 %) is preserved while cardiac output declines (25.6±1.0 vs. 20.9±1.5*, mL/min). Diastolic dysfunction is evident by decreased e′ (30.6±1.6 vs. 16.7±1.1****, mm/sec), elevated E/e′ ratio (23.1±1.2 vs. 37.0±1.4****), prolonged IVRT (13.3±0.8 vs. 21.1±0.5****, sec), and left-atrial enlargement (1.83±0.05 vs. 2.19±0.09**, mm). Hypertrophy is indicated by increased posterior wall thickness at diastole (0.52±0.03 vs. 0.71±0.04***, mm), left ventricular mass (75.2±3.8 vs. 113.5±7.0**, mg), and heart weight/tibia length (6.7±0.2 vs. 8.6±0.6**, mg/mm). Critically, these structural and functional changes translate into significant exercise intolerance, with a shorter running distance in HFpEF mice compared with controls (156±17 vs. 50±3***, m). Together, the 15-week data provide compelling evidence that this model captures the cardinal features of HFpEF. Gut barrier function was impaired in HFpEF, as shown by elevated plasma FITC–dextran after gavage (45,575±4,004 vs. 143,747±14,199**, raw fluorescence intensity), indicating increased paracellular permeability. Consistently, qRT-PCR analysis of ileal tight junction genes relative to GAPDH showed decreased Zonula Occludens-1 (1.13±0.15 vs. 0.30±0.02***, a.u.) and occludin (1.01±0.01 vs. 0.45±0.14**, a.u.), while claudin-2, a pore-forming protein, was upregulated (1.27±0.15 vs. 1.73±0.27*, a.u.). Zonulin, a tight-junction modulator that promotes junctional disassembly, was also elevated in HFpEF (0.50±0.27 vs. 2.06±0.27*, a.u.). In addition, ileal histology confirmed structural abnormalities, with shortened crypts (80.7±5.5 vs. 59.7±1.86*, µm). A composite ileal tissue histology score showed reduced crypt depth, villus irregularity, thickening of muscular wall, and diminished Paneth cell granularity, consistent with mucosal stress in HFpEF (0.33 ± 0.33 vs. 2.33 ± 0.33*, a.u.). N= 3-10 (mean± SEM). T-test, *= P< 0.05 vs ctrl, **=P< 0.01 vs ctrl, ***=P< 0.001 vs ctrl, ****=P< 0.0001 vs ctrl. Conclusions: These findings demonstrate significant gut barrier dysfunction in HFpEF, including increased permeability, tight-junction loss, and epithelial injury, linking cardiac disease to impaired intestinal integrity. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.