Effects of natural peptides from food proteins on angiotensin converting enzyme activity and hypertension

Functional potato bioactive peptide intensifies Nrf2-dependent antioxidant defense against renal damage in hypertensive rats

Hypertension, which is known as a silent killer, is the second leading cause of kidney failure worldwide. Elevated blood pressure causes approximately 7.6 million deaths, which account for ~13.5% of the total deaths and will continue to rise. High blood pressure is the prime risk factor associated with complications in major organs, including the heart, brain and kidney. High blood pressure accelerates oxidative stress and thereby causes organ dysfunction through the production of reactive oxygen species. In this study, we investigated the renal-protective effects of the bioactive peptide IF from alcalase potato protein hydrolysate in spontaneously hypertensive rat kidney. Sixteen-week-old spontaneously hypertensive rats were divided into three groups (n = 6), and Sixteen-week-old Wistar Kyoto rats (n = 6) served as the control group. The rats were administered IF and captopril via oral gavage for 8 weeks and then sacrificed, and their kidneys were harvested. The kidney sections from the rats treated with IF showed restoration of the structure of the glomerulus and Bowman's capsule. The expression levels of Nrf2-mediated antioxidants were also increased, as confirmed by 4-hydroxynonenal immunohistochemical staining. The TUNEL assay revealed a significant reduction in the number of apoptotic cells in the IF-treated groups, which was consistent with the western blot results. Thus, the bioactive peptide IF exerts potential protective effects against hypertension-associated ROS-mediated renal damage via the Nrf2-dependent antioxidant pathway along the DJ-1 and AKT axes. Hence, we speculate that IF might have promising therapeutic effects on renal damage associated with hypertension.

Beyond plucking: Feathers bioprocessing into valuable protein hydrolysates

The livestock production and subsequent processing of meat results in huge quantities of solid waste such as viscera, bones, skin and keratin-rich materials, including feathers, hair, wool, claws and hooves. In particular, the continuous growth of poultry industry generates massive amounts of feathers as major waste material. The conversion of such by-products into materials with increased value has been studied. Hydrothermal, chemical or biological approaches have been investigated to achive effective conversion of highly recalcitrant proteins that are abundant in animal waste, but increasing interest is devoted to the development of biotechnological methods. The processing of feathers and other by-products into protein hydrolysates may have industrial and commercial significance. Therefore, this review comprehensively addresses the postulated applications of hydrolysates obtained from keratinous biomasses. Examples on the utilization of feather hydrolysates as organic soil fertilizers, feed ingredients, cosmetic formulations and biofuel production are described in the literature. Microbial feather hydrolysis can generate bioactive peptides as well. The use of protein-rich waste from meat industry to produce hydrolysates with biological activities constitutes a point of utmost interest for development of functional ingredients with elevated value.

Amino Acids and Hypertension in Adults

Accumulating evidence suggests a potential role of dietary protein among nutritional factors interfering with the regulation of blood pressure. Dietary protein source (plant versus animal protein), and especially, protein composition in terms of amino acids has been postulated to interfere with mechanisms underlying the development of hypertension. Recently, mounting interest has been directed at amino acids in hypertension focusing on habitual dietary intake and their circulating levels regardless of single amino acid dietary supplementation. The aim of the present review was to summarize epidemiological evidence concerning the connection between amino acids and hypertension. Due to the large variability in methodologies used for assessing amino acid levels and heterogeneity in the results obtained, it was not possible to draw robust conclusions. Indeed, some classes of amino acids or individual amino acids showed non-causative association with blood pressure as well as the incidence of hypertension, but the evidence was far from being conclusive. Further research should be prompted for a thorough understanding of amino acid effects and synergistic actions of different amino acid classes on blood pressure regulation.

Evidence that Nitric Oxide is Involved in the Blood Pressure Lowering Effect of the Peptide AVFQHNCQE in Spontaneously Hypertensive Rats

AVFQHNCQE is an antihypertensive nonapeptide obtained from a chicken foot protein hydrolysate. The present study aims to investigate the mechanisms involved in its blood pressure (BP)-lowering effect. Male (17⁻20 weeks old) spontaneously hypertensive rats (SHR) were used in this study. Rats were divided into two groups and orally administered water or 10 mg/kg body weight (bw) AVFQHNCQE. One hour post-administration, animals of both groups were intra-peritoneally treated with 1 mL of saline or with 1 mL of saline containing 30 mg/kg bw Nω-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide (NO) synthesis, or with 1 mL of saline containing 5 mg/kg bw indomethacin, which is an inhibitor of prostacyclin synthesis (n = 6 per group). Systolic BP was recorded before oral administration and six hours after oral administration. In an additional experiment, SHR were administered water or 10 mg/kg bw AVFQHNCQE (n = 6 per group) and sacrificed six hours post-administration to study the mechanisms underlying the peptide anti-hypertensive effect. Moreover, the relaxation caused by AVFQHNCQE in isolated aortic rings from Sprague-Dawley rats was evaluated. The BP-lowering effect of the peptide was not changed after indomethacin administration but was completely abolished by L-NAME, which demonstrates that its anti-hypertensive effect is mediated by changes in endothelium-derived NO availability. In addition, AVFQHNCQE administration downregulated aortic gene expression of the vasoconstrictor factor endothelin-1 and the endothelial major free radical producer NADPH. Moreover, while no changes in plasma ACE activity were observed after its administration, liver GSH levels were higher in the peptide-treated group than in the water group, which demonstrates that AVFQHNCQE presents antioxidant properties.

Chicken Protein Hydrolysates Have Anti-Inflammatory Effects on High-Fat Diet Induced Obesity in Mice

Background: Studies have shown that dietary source of protein and peptides can affect energy metabolism and influence obesity-associated diseases. This study aimed to investigate the impact of different chicken protein hydrolysates (CPHs) generated from chicken rest raw materials in a mouse obesity model. Methods: Male C57BL/6 mice were fed a high-fat, high-sucrose diet with casein or CPHs generated using Papain + Bromelain, Alcalase, Corolase PP, or Protamex for 12 weeks (n = 12). Body weight, feed intake, and intraperitoneal glucose tolerance was determined, and plasma and liver and adipose tissues were collected at sacrifice. Results: The average feed intake and body weight did not differ between the groups and white adipose tissue depots were unchanged, except for a reduction in the subcutaneous depot in mice fed the Protamex CPH diet. Moreover, the CPH diets did not prevent increased fasting glucose and insulin levels. Interestingly, the hepatic mitochondrial fatty acid β-oxidation was increased in mice fed Alcalase and Corolase PP CPHs. All CPH diets reduced plasma interleukine (IL)-1β, interferon-γ, tumor necrosis factor α, and monocyte chemotactic protein 1 compared to control, indicating anti-inflammatory effects. In addition, Corolase PP and Protamex CPHs significantly reduced plasma levels of IL-1α, IL-2, IL-6, IL-10, and granulocyte macrophage colony-stimulating factor. Conclusions: CPH diets were not able to counteract obesity and glucose intolerance in a mouse obesity model, but strongly reduced inflammatory parameters associated with obesity. Alcalase and Corolase PP CPHs also stimulated mitochondrial fatty acid β-oxidation. The possibility that hydrolysates from chicken rest raw materials could alleviate obesity-associated metabolic disease should be investigated further.