Chicken muscle hydrolysate reduces blood pressure in spontaneously hypertensive rats, upregulates ACE2, and ameliorates vascular inflammation, fibrosis, and oxidative stress.

Spent hens are egg-laying chicken reaching the end of their egg-laying cycle and are seen as a by-product to the egg industry. A spent hen muscle protein hydrolysate prepared by food-grade thermoase PC10F (SPH-T) has previously shown antihypertensive potential. In the present work, we further investigated its antihypertensive effect and underlying mechanisms in spontaneously hypertensive rats. There are three groups: untreated, low dose (250 mg SPH-T/kg/day body weight), and high dose (1,000 mg SPH-T/kg/day body weight). Oral administration of SPH-T over a period of 20 days reduced systolic blood pressure by 25.7 mm Hg (p < 0.001) and 11.9 mm Hg (p < 0.05), respectively, for the high- and low-dose groups. The high-dose treatment decreased the circulating level of angiotensin II (from 25.0 to 5.7 pg/ml) while increased angiotensin-converting enzyme 2 (ACE2) (from 1.3 to 3.3 IU/ml) and angiotensin (1-7) (from 37.0 to 70.1 pg/ml) significantly (p < 0.05). Furthermore, the high-dose group doubled the aortic expression of ACE2 while reduced the expression of angiotensin (Ang) II type 1 receptor (by 35%). Circulating inflammatory cytokines including tumor necrosis factor alpha and monocyte chemoattractant protein-1 as well as vascular inflammatory proteins including inducible nitric oxide synthase and vascular cell adhesion molecule-1 were attenuated by ∼15%-50% by the treatment; nitrosative stress (35%) and type I collagen synthesis (50%) in the aorta were also attenuated significantly (p < 0.05). Moreover, SPH-T possessed an umami taste (no obvious bitter taste) as analyzed by electronic tongue. PRACTICAL APPLICATION: Hypertension is a global health concern, afflicting more than 20% of adults worldwide. Uncovering the antihypertensive effect of spent hen protein hydrolysate underpinned its functional food nutraceutical applications for the prevention and treatment of hypertension.