Beneficial Effects of Simulated Gastro-Intestinal Digests of Fried Egg and Its Fractions on Blood Pressure, Plasma Lipids and Oxidative Stress in Spontaneously Hypertensive Rats

Background: We have previously characterized several antihypertensive peptides in simulated digests of cooked eggs and showed blood pressure lowering property of fried whole egg digest. However, the long-term effects of this hydrolysate and its fractions on blood pressure are not known. Therefore, the objectives of the study were to determine the effects of long term administration of fried whole egg hydrolysate and its fractions (i.e. egg white and egg yolk) on regulation of blood pressure and associated factors in cardiovascular disease such as plasma lipid profile and tissue oxidative stress. Methods and Results: We used spontaneously hypertensive rats (SHR), an animal model of essential hypertension. Hydrolysates of fried egg and its fractions were prepared by simulated gastro-intestinal digestion with pepsin and pancreatin. 16–17 week old male SHRs were orally administered fried whole egg hydrolysate, non-hydrolyzed fried whole egg, egg white hydrolysate or egg yolk hydrolysates (either defatted, or not) daily for 18 days. Blood pressure (BP) and heart rate were monitored by telemetry. Animals were sacrificed at the end of the treatment for vascular function studies and evaluating plasma lipid profile and tissue oxidative stress. BP was reduced by feeding fried whole egg hydrolysate but not by the nonhydrolyzed product suggesting a critical role for in vitro digestion in releasing anti-hypertensive peptides. Egg white hydrolysate and defatted egg yolk hydrolysate (but not egg yolk hydrolysate) also had similar effects. Reduction in BP was accompanied by the restoration of nitric oxide (NO) dependent vasorelaxation and reduction of plasma angiotensin II. Fried whole egg hydrolysate also reduced plasma levels of triglyceride although it was increased by the non-hydrolyzed sample. Additionally the hydrolyzed preparations attenuated tissue oxidative stress. Conclusion: Our results demonstrate that fried egg hydrolysates exert antihypertensive effects, improve plasma lipid profile and attenuate tissue oxidative stress in vivo

Perspectives on the Potential Benefits of Antihypertensive Peptides towards Metabolic Syndrome

In addition to the regulation of blood pressure, the renin-angiotensin system (RAS) also plays a key role in the onset and development of insulin resistance, which is central to metabolic syndrome (MetS). Due to the interplay between RAS and insulin resistance, antihypertensive compounds may exert beneficial effects in the management of MetS. Food-derived bioactive peptides with RAS blocking properties can potentially improve adipose tissue dysfunction, glucose intolerance, and insulin resistance involved in the pathogenesis of MetS. This review discusses the pathophysiology of hypertension and the association between RAS and pathogenesis of the MetS. The effects of bioactive peptides with RAS modulating effects on other components of the MetS are discussed. While the in vivo reports on the effectiveness of antihypertensive peptides against MetS are encouraging, the exact mechanism by which these peptides infer their effects on glucose and lipid handling is mostly unknown. Therefore, careful design of experiments along with standardized physiological models to study the effect of antihypertensive peptides on insulin resistance and obesity could help to clarify this relationship

Food-Derived Bioactive Peptides on Inflammation and Oxidative Stress

Chronic diseases such as atherosclerosis and cancer are now the leading causes of morbidity and mortality worldwide. Inflammatory processes and oxidative stress underlie the pathogenesis of these pathological conditions. Bioactive peptides derived from food proteins have been evaluated for various beneficial effects, including anti-inflammatory and antioxidant properties. In this review, we summarize the roles of various food-derived bioactive peptides in inflammation and oxidative stress and discuss the potential benefits and limitations of using these compounds against the burden of chronic diseases

Beneficial Effects of Simulated Gastro-Intestinal Digests of Fried Egg and Its Fractions on Blood Pressure, Plasma Lipids and Oxidative Stress in Spontaneously Hypertensive Rats

Background: We have previously characterized several antihypertensive peptides in simulated digests of cooked eggs and showed blood pressure lowering property of fried whole egg digest. However, the long-term effects of this hydrolysate and its fractions on blood pressure are not known. Therefore, the objectives of the study were to determine the effects of long term administration of fried whole egg hydrolysate and its fractions (i.e. egg white and egg yolk) on regulation of blood pressure and associated factors in cardiovascular disease such as plasma lipid profile and tissue oxidative stress. Methods and Results: We used spontaneously hypertensive rats (SHR), an animal model of essential hypertension. Hydrolysates of fried egg and its fractions were prepared by simulated gastro-intestinal digestion with pepsin and pancreatin. 16–17 week old male SHRs were orally administered fried whole egg hydrolysate, non-hydrolyzed fried whole egg, egg white hydrolysate or egg yolk hydrolysates (either defatted, or not) daily for 18 days. Blood pressure (BP) and heart rate were monitored by telemetry. Animals were sacrificed at the end of the treatment for vascular function studies and evaluating plasma lipid profile and tissue oxidative stress. BP was reduced by feeding fried whole egg hydrolysate but not by the nonhydrolyzed product suggesting a critical role for in vitro digestion in releasing anti-hypertensive peptides. Egg white hydrolysate and defatted egg yolk hydrolysate (but not egg yolk hydrolysate) also had similar effects. Reduction in BP was accompanied by the restoration of nitric oxide (NO) dependent vasorelaxation and reduction of plasma angiotensin II. Fried whole egg hydrolysate also reduced plasma levels of triglyceride although it was increased by the non-hydrolyzed sample. Additionally the hydrolyzed preparations attenuated tissue oxidative stress. Conclusion: Our results demonstrate that fried egg hydrolysates exert antihypertensive effects, improve plasma lipid profile and attenuate tissue oxidative stress in vivo

EWH actions are partly mediated through insulin receptor.

<p>3T3-F442A cells were incubated with EWH (5 mg/mL) for 48 hrs prior to stimulation with insulin (10 μg/mL) for 20 or 40 min. The cells were then lysed and western blotting of the lysates was performed with antibodies against the: total and phosphorylated forms of IRβ (a), total IRβ and α-tubulin (loading control) (b), and total and phosphorylated forms of IRS-1 (c). Representative sets of images are shown. Bands were quantified by densitometric analysis. Data are presented as mean±SEM of 4–7 independent experiments. *, ** and **** indicate p<0.05, p<0.01, and p<0.0001 respectively.</p

Egg white hydrolysate shows insulin mimetic and sensitizing effects in 3T3-F442A pre-adipocytes

<div><p>Insulin resistance and inflammation in adipose tissue is a key mechanism underlying metabolic syndrome, a growing health problem characterized by diabetes, obesity and hypertension. Previous work from our research group has demonstrated the potential of egg white ovotransferrin derived bioactive peptides against hypertension, oxidative stress and inflammation <i>in vitro</i> and <i>in vivo</i>. Egg white hydrolysate (EWH) has also shown anti-hypertensive effects in spontaneously hypertensive rats. Given the interplay among hypertension, inflammation, oxidative stress and metabolic syndrome, the objective of the study was to test the EWH on differentiation, insulin signaling and inflammatory responses in 3T3-F442A pre-adipocytes. Our study suggested that EWH could promote adipocyte differentiation as shown by increased lipid accumulation, increased release of adiponectin and upregulation of peroxisome proliferator associated receptor gamma (PPARγ) and CCAAT/ enhancer binding protein alpha (C/EBP-α). In addition to enhanced insulin effects on the upregulation of protein kinase B/Akt phosphorylation, EWH treatment increased extracellular signal regulated kinase 1/2 (ERK1/2) phosphorylation to a level similar to that of insulin, indicating insulin sensitizing and mimetic properties of the EWH. EWH further attenuated cytokine induced inflammatory marker; cyclooxygenase -2 (COX-2) by 48.78%, possibly through the AP-1 pathway by down regulating c-Jun phosphorylation in adipocytes. Given the critical role of adipose in the pathogenesis of insulin resistance and metabolic syndrome, EWH may have potential applications in the prevention and management of metabolic syndrome and its complications.</p></div

EWH upregulates markers of adipocyte differentiation.

<p>3T3-F442A cells were incubated with EWH (5 mg/mL) or insulin (positive control; 10 μg/mL) for 72 hrs. The cells were then lysed and western blotting of the lysates was performed with antibodies against PPARγ (a), C/EBP-α (b) and α-tubulin (loading control; both a and b). A representative set of images are shown. Bands were quantified by densitometric analysis. Data are presented as mean±SEM of 4–5 independent experiments. *, ** and *** indicate p<0.05, p<0.01 and p<0.001 respectively, compared to the untreated control (Untr).</p

EWH upregulates PPARγ expression in a dose-dependent manner.

<p>3T3-F442A cells were incubated with different dosages of EWH (0.63–10 mg/mL) or insulin (10 μg/mL) for 72 hrs. The cells were then lysed and western blotting of the lysates was performed with antibodies against PPARγ and α-tubulin (loading control). A representative set of images is shown. Bands were quantified by densitometric analysis. Data are presented as mean±SEM of 3–4 independent experiments. **, *** and **** indicate p<0.01, p<0.001 and p<0.0001 respectively, compared to the untreated control (Untr).</p

EWH treatment induces adipogenic differentiation in 3T3-F442A cells.

<p>3T3-F442A cells were incubated with EWH (5 mg/mL) or insulin (positive control; 10 μg/mL) for 72 hrs. (a) Following incubation, the cells were fixed and stained with the neutral lipid-specific dye LipidTox (green), the nuclear stain Hoechst3342 (blue) and visualized under fluorescence microscopy. A set of representative images are shown. (b) The cell-free culture supernatants were collected and analyzed by ELISA to determine adiponectin levels. Data are presented as mean±SEM of 4–5 independent experiments. * and ** indicate p<0.05 and p<0.01 respectively compared to the untreated control (Untr).</p

EWH differentially modulates insulin-mediated phosphorylation of ERK and Akt.

<p>3T3-F442A cells were incubated with EWH (5 mg/mL) for 48 hrs prior to stimulation with insulin (10 μg/mL) for 20 or 40 min. The cells were then lysed and western blotting of the lysates was performed with antibodies against the total and phosphorylated forms of ERK (a) and Akt (b). Representative sets of images are shown. Bands were quantified by densitometric analysis. Data are presented as mean±SEM of 5 independent experiments. *, ** and *** indicate p<0.05, p<0.01 and p<0.001 respectively compared to untreated control by a two-way ANOVA. ‘ns’ indicates: not significant.</p