# Evaluation of In Vitro Antihypertensive and Anti-Inflammatory Properties of Dairy By-Products
In recent years, consumption of fermented dairy products has grown worldwide, and market trends indicate that this will further increase. Greek-style yogurt and cheese are two major categories of fermented dairy products [6]. The manufacture of fermented dairy products results in dairy by-products, the composition of which depends mainly on the used raw material [7]. The huge amounts of dairy by-products, sweet whey (SW), and yogurt acid whey (YAW), derived from cheese and Greek-style yogurt, respectively, present both economic and environmental challenges [7; 8]. Caseins and whey proteins are the major protein fractions in dairy products, with casein comprising about 80% of milk protein. Protein from dairy products is considered an excellent source of numerous bioactive peptides with multifunctional properties, including antihypertensive, antioxidant, antimicrobial, immunomododulatory, opioid, and antithrombotic activities [9; 10; 11; 12; 13]. It is well known that milk proteins are considered a high-quality source of bioactive peptides with antihypertensive and anti-inflammatory functions [14]. However, bioactive peptides are encrypted and inactive in the parental protein and are generated during gastrointestinal digestion by enzymatic hydrolysis or microbial fermentation of food protein [15]. There is an ever-increasing number of studies supporting the idea that whey proteins could be used as potential functional food ingredients, and this idea is attributed to the enhanced bioactivity of milk-derived peptides. Among the several bioactive activities of whey protein peptides, ACE-inhibitory and anti-inflammatory activity have received special attention due to their beneficial effects on hypertension and immunoregulation, respectively. The exopeptidase angiotensin I-converting enzyme (ACE; EC 3.4.15.1) has been classically associated with the renin-angiotensin system, which plays a central role in the regulation of peripheral blood pressure. ACE controls the levels of endogenous regulatory peptides such as angiotensin II, a potent vasoconstrtictor, and bradykinin, a potent vasodilator. Currently, synthetic ACE inhibitors have been extensively used to treat hypertension. Although synthetic drugs are effective, they have several side effects on human health. Therefore, researchers have focused on various ACE inhibitors obtained from natural foods [16] since the inhibition of ACE activity by food-protein-derived peptides can lead to an overall antihypertensive effect [17]. Regarding the ACE activity of dairy proteins, there is one study showing that digested and filtrated dairy proteins have higher values for ACE-inhibitory activity compared to the corresponding plant proteins [18]. Furthermore, the major milk whey proteins (\(\alpha\)-lactalbumin and \(\beta\)-lactoglobulin) have been reported to contain peptides which exhibit ACE-inhibitory activity [19]. Inflammation is an important physiological response of the body mediated by immune cells against injury and tissue damage. In more detail, firstly, immune cells (cells of the innate immune system such as monocytes, macrophages, and neutrophils) and inflammatory mediators (such as cytokines and chemokines) are known to be involved in the inflammatory process [20]. Nitric oxide (NO) is one of the inflammatory mediators that regulate a variety of physiological and pathological immune responses, including inflammation [21]. There are two types of nitric oxide synthases (NOSs), with the expression of inducible NOSs (iNOSs) in activated macrophages being responsible for the overproduction of NO, which in turn enhances inflammation. Another important inflammatory macrophage mediator is cyclooxygenase-2 (COX-2), which is related with prostaglandin E2 (PGE2), and the inhibition of its production is considered important for the inflammatory process [22].