Abstract
Background:
Hypertension is a major global health burden and a leading contributor to cardiovascular morbidity, with a prevalence of 34.1% in Indonesia. Although angiotensin-converting enzyme (ACE) inhibitors such as captopril are widely used, their long-term use is limited due to side effects. Rice bran, a nutrient-rich byproduct of rice milling, has been reported to possess antioxidant and antihypertensive potential; however, its cardioprotective effects in hypertensive conditions remain under-explored.

Aim:
This study aims to evaluate the antihypertensive and cardioprotective effects of rice bran supplementation in a DOCA-salt-induced hypertensive rat model, with a focus on inflammatory and structural changes in the heart.

Methods:
Male Wistar rats were divided into five groups: normotensive control (K−), hypertensive control (K+), a group treated with captopril (5 mg/kg BW), and groups supplemented with rice bran at 1% (D1) and 2% (D2) of the daily diet for four weeks. Hypertension was induced using DOCA-salt. Serum protein profiles were analyzed by SDS-PAGE, cardiac histopathology was assessed using Hematoxylin–Eosin staining, and TNF-α and iNOS expression were evaluated by immunohistochemistry.

Results:
Rice bran supplementation, particularly at 2%, significantly improved cardiac structure, as evidenced by reduced cardiomyocyte hypertrophy, decreased necrosis, and restoration of myocardial organization. SDS-PAGE analysis revealed the reappearance of the ~40 kDa protein band and a reduction in the ~150 kDa band in the treated group, indicating the restoration of cardiac protein expression patterns. Inflammatory markers were significantly suppressed, with TNF-α reduced by 74.9% (D1) and 76.8% (D2), exceeding the reduction observed with captopril (54.1%). Similarly, iNOS expression decreased most effectively in the D2 group (29.52% compared to the hypertensive control).

Conclusion:
Rice bran supplementation provides significant antihypertensive and cardioprotective effects in DOCA-salt-induced hypertensive rats, primarily through reduced inflammatory responses and improved cardiac structural integrity. These findings support the potential of rice bran as a functional dietary intervention for managing hypertension-induced cardiac injury.

Key words: ACE inhibitor; Histopathology; Hypertension; Immunohistochemistry; Rice bran.