Fish protein improves blood pressure but alters HDL2 and HDL3 composition and tissue lipoprotein lipase activities in spontaneously hypertensive rats

Beneficial effects of fish and fish peptides on main metabolic syndrome associated risk factors: Diabetes, obesity and lipemia

The definition of metabolic syndrome (MetS) fairly varies from one to another guideline and health organization. Per description of world health organization, occurrence of hyperinsulinemia or hyperglycemia in addition to two or more factors of dyslipidemia, hypoalphalipoproteinemia, hypertension and or large waist circumference factors would be defined as MetS. Conventional therapies and drugs, commonly with adverse effects, are used to treat these conditions and diseases. Nonetheless, in the recent decades scientific community has focused on the discovery of natural compounds to diminish the side effects of these medications. Among many available bioactives, biologically active peptides have notable beneficial effects on the management of diabetes, obesity, hypercholesterolemia, and hypertension. Marine inclusive of fish peptides have exerted significant bioactivities in different experimental in-vitro, in-vivo and clinical settings. This review exclusively focuses on studies from the recent decade investigating hypoglycemic, hypolipidemic, hypercholesterolemic and anti-obesogenic fish and fish peptides. Related extraction, isolation, and purification methodologies of anti-MetS fish biopeptides are reviewed herein for comparison purposes only. Moreover, performance of biopeptides in simulated gastrointestinal environment and structure-activity relationship along with absorption, distribution, metabolism, and excretion properties of selected oligopeptides have been discussed, in brief, to broaden the knowledge of readers on the design and discovery trends of anti-MetS compounds.Supplemental data for this article is available online at https://doi.org/10.1080/10408398.2022.2052261 .

Antihypertensive and Angiotensin-I-Converting Enzyme (ACE)-Inhibitory Peptides from Fish as Potential Cardioprotective Compounds

The term metabolic/cardiometabolic/insulin resistance syndrome could generally be defined as the co-occurrence of several risk factors inclusive of systemic arterial hypertension. Not only that organizations, such as the world health organization (WHO) have identified high blood pressure as one of the main risk factors of the cardiometabolic syndrome, but there is also a link between the occurrence of insulin resistance/impaired glucose tolerance and hypertension that would consequently lead to type-2 diabetes (T2D). Hypertension is medicated by various classes of synthetic drugs; however, severe or mild adverse effects have been repeatedly reported. To avoid and reduce these adverse effects, natural alternatives, such as bioactive peptides derived from different sources have drawn the attention of researchers. Among all types of biologically active peptides inclusive of marine-derived ones, this paper's focus would solely be on fish and fishery by-processes' extracted peptides and products. Isolation and fractionation processes of these products alongside their structural, compositional and digestion stability characteristics have likewise been briefly discussed to better address the structure-activity relationship, expanding the reader's knowledge on research and discovery trend of fish antihypertensive biopeptides. Furthermore, drug-likeness of selected biopeptides was predicted by Lipinski's rules to differentiate a drug-like biopeptide from nondrug-like one.

Preclinical and Clinical Studies on Antioxidative, Antihypertensive and Cardioprotective Effect of Marine Proteins and Peptides-A Review

High seafood consumption has traditionally been linked to a reduced risk of cardiovascular diseases, mainly due to the lipid lowering effects of the long chained omega 3 fatty acids. However, fish and seafood are also excellent sources of good quality proteins and emerging documentation show that, upon digestion, these proteins are sources for bioactive peptides with documented favorable physiological effects such as antioxidative, antihypertensive and other cardioprotective effects. This documentation is mainly from in vitro studies, but also animal studies are arising. Evidence from human studies evaluating the positive health effects of marine proteins and peptides are scarce. In one study, a reduction in oxidative stress after intake of cod has been documented and a few human clinical trials have been performed evaluating the effect on blood pressure. The results are, however, inconclusive. The majority of the human clinical trials performed to investigate positive health effects of marine protein and lean fish intake, has focused on blood lipids. While some studies have documented a reduction in triglycerides after intake of lean fish, others have documented no effects.

A comparison between the impact of two types of dietary protein on brain glucose concentrations and oxidative stress in high fructose-induced metabolic syndrome rats

The present study explored the potential of fish proteins to counteract high glucose levels and oxidative stress induced by fructose in the brain. A total of 24 male Wistar rats consumed sardine protein or casein with or without high fructose (64%). After 2 months, brain tissue was used for analyses. The fructose rats exhibited an increase in body mass index (BMI), body weight, absolute and relative brain weights and brain glucose; however, there was a decrease in food and water intake. Fructose disrupts membrane homeostasis, as evidenced by an increase in the brain hydroperoxides and a decrease in catalase (CAT) and glutathione peroxidase (GSH-Px) compared to the control. The exposure to the sardine protein reduced BMI, food intake, glucose and hydroperoxides, and increased CAT and GSH-Px in the brain. In conclusion, the metabolic dysfunctions associated with the fructose treatment were ameliorated by the presence of sardine protein in the diet by decreasing BMI, brain glucose and lipid peroxidation, and increasing CAT and GSH-Px activities.

Antihypertensive effects of dietary protein and its mechanism

Hypertension is a leading cause of morbidity and mortality worldwide. Individuals with hypertension are at increased risk of stroke, heart disease and kidney failure. Both genetic and lifestyle factors, particularly diet, have been attributed an important role in the development of hypertension. Reducing dietary sugar and salt intake can help lower blood pressure; similarly, adequate protein intake may also attenuate hypertension. Observational, cross-sectional and longitudinal epidemiological studies, and controlled clinical trials, have documented significant inverse associations between protein intake and blood pressure. Human and animal studies have shown that specific amino acids within proteins may have antihypertensive effects. Cysteine, glutathione (a tripeptide), glutamate and arginine attenuate and prevent alterations that cause hypertension including insulin resistance, decreased nitric oxide bioavailability, altered renin angiotensin system function, increased oxidative stress and formation of advanced glycation end products. Leucine increases protein synthesis in skeletal muscle and improves insulin resistance by modulating hepatic gluconeogenesis. Taurine and tryptophan attenuate sympathetic nervous system activity. Soy protein helps lower blood pressure through its high arginine content and antioxidant activity exhibited by isoflavones. A diet containing an ample amount of protein may be a beneficial lifestyle choice for individuals with hypertension; one example is the Dietary Approaches to Stop Hypertension (DASH) diet, which is low in salt and saturated fat; includes whole grains, lean meat, poultry, fish and nuts; and is rich in vegetables, fruits and low-fat dairy products, which are good sources of antioxidant vitamins, minerals and fibre. Including an adequate supply of soy in the diet should also be encouraged.

Effects of a supplementation of n-3 polyunsaturated fatty acids with or without fish gelatin on gene expression in peripheral blood mononuclear cells in obese, insulin-resistant subjects

AIM

To investigate gene expression changes in peripheral blood mononuclear cells (PBMCs) following an n-3 polyunsaturated fatty acid (PUFA) and n-3 PUFA plus fish gelatin (+FG) supplementation.

METHODS

A transcriptome comparison of 8-week supplementation with n-3 PUFA and n-3 PUFA+FG was carried out in PBMCs of 16 obese insulin-resistant subjects.

RESULTS

Erythrocyte n-3 PUFA concentration increased and plasma triglycerides decreased significantly without altering inflammatory parameters after both supplementations. n-3 PUFA supplementation changed the expression of 805 genes, whereas n-3 PUFA+FG supplementation altered the expression of 184 genes. Three genes were commonly changed: fatty acid desaturase 1, free fatty acid receptor 3, and ectodysplasin. Pathway analyses indicate changes in gene expression via the nuclear receptor peroxisome proliferator-activated receptor α pathway after both supplementations. Further, the extent of modifications in the expression of genes implicated in the inflammatory pathways - the oxidative stress response mediated by nuclear factor (erythroid-derived 2)-like 2, nuclear transcription factor κB, oxidative stress, and hypoxia-inducible factor signaling - was different after each supplementation.

CONCLUSION

Although n-3 PUFA and n-3 PUFA+FG supplementations have a distinct impact on gene expression levels, the consequences on biochemical parameters and metabolic pathways were comparable after both supplementations.

The effect of farmed trout on cardiovascular risk markers in healthy men

Increased intake of marine long-chain n-3 PUFA (n-3 LCPUFA) may decrease the risk of CVD and reduce mortality by lowering serum TAG and blood pressure (BP). Furthermore, n-3 LCPUFA may affect novel CVD risk markers related to inflammation and vascular function. The objective of the present study was to examine the effect of farmed trout on novel and traditional CVD risk markers in healthy men, and to evaluate whether this was affected by the aquacultural feed regime. We performed a parallel, 8-week intervention study in which sixty-eight healthy male volunteers were randomised to consume either a daily meal with 150 g farmed trout raised on either marine or vegetable-based feed, or a reference meal containing 150 g chicken. Twenty-four hour BP, pulse wave velocity, augmentation index, fatty acid composition of erythrocyte (RBC), and concentrations of TAG, HDL-cholesterol, LDL-cholesterol, glucose, insulin, C-reactive protein (CRP) and other markers of inflammation were measured at weeks 0 and 8. RBC content of total n-3 LCPUFA, both EPA and DHA, was significantly higher among men consuming trout raised on marine feed compared with men consuming the vegetable-fed trout or chicken. The three intervention groups did not differ significantly with respect to any of the other outcome variables, although there were trends towards associations between the changes in RBC n-3 LCPUFA and those in BP and CRP. In the present study, we conclude that we could not confirm the fish oil-induced reduction in CVD risk markers after daily consumption of trout with high or low n-3 LCPUFA content. However, trout raised on vegetable-based feed had less pronounced impact on RBC n-3 LCPUFA status.

Fish nutrients decrease expression levels of tumor necrosis factor-α in cultured human macrophages

Numerous studies have demonstrated the beneficial effects of fish consumption on inflammatory markers. Until now, these beneficial effects of fish consumption have been mostly linked to the omega-3 fatty acids (FA). The objective of the present study was to examine, in vitro, whether expression levels of genes involved in the inflammatory response differ in human macrophages incubated with casein hydrolysates (CH) or fish protein hydrolysates (FPH) in the presence or absence of omega-3 FA compared with omega-3 FA alone. Peripheral blood monocytes differentiated into macrophages from 10 men were incubated in the presence of omega-3 FA (10 μM eicosapentaenoic acid and 5 μM docosahexaenoic acid) or CH or FPH (10, 100, 1,000 μg) with or without omega-3 FA for 48 h. Results demonstrate that expression levels of tumor necrosis factorα ( TNFα) had a tendency to be lower after the addition of FPH alone or CH with omega-3 FA compared with omega-3 FA treatment. Furthermore, the combination of FPH and omega-3 FA synergistically decreased expression levels of TNFα compared to treatment with omega-3 FA or FPH alone. No difference on gene expression levels of interleukin-6 was observed between treatments. In conclusion, these preliminary results suggest that the anti-inflammatory effects of fish consumption can be explained by a synergistic effect of the omega-3 FA with the protein components of fish on TNFα expression and therefore contribute to the beneficial effects of fish consumption. Hence, follow-up studies should be performed to confirm the effects of a diet rich in FPH and omega-3 FA on serum proinflammatory cytokine concentrations.

Influence of herring (Clupea harengus) and herring fractions on metabolic status in rats fed a high energy diet

AIM

Few dietary studies have looked beyond fish oil to explain the beneficial metabolic effects of a fish-containing diet. Our aim was to study whether addition of herring, or sub-fractions of herring, could counteract negative metabolic effects known to be induced by a high-fat, high-sugar diet.

METHODS

Rats were given six different diets: standard pellets; high energy diet with chicken mince (HiE control); high energy diet with herring mince (HiE herring); and high energy diet with chicken mince and either herring oil (HiE herring oil), herring press juice, PJ (HiE PJ) or herring low molecular weight PJ (HiE LMW-PJ). Factors associated with the metabolic syndrome were measured.

RESULTS

There were no differences in energy intake or body weight between the groups, but animals fed high energy diets had a higher body fat content compared with the pellet group, although not statistically significant in all groups. Mesenteric adipocyte size was smaller in the HiE herring oil group compared with the HiE control. Glucose clamp studies showed that, compared with the pellet group, the HiE control and HiE herring diets, but not the HiE herring oil diet, induced insulin resistance. Addition of herring or herring oil to the high energy diet decreased total cholesterol levels, triacylglycerols and the atherogenic index compared with the HiE control group.

CONCLUSIONS

The results suggest that addition of herring or herring oil counteracts negative effects on blood lipids induced by a high energy diet. The lipid component of herring thus seems to be responsible for these beneficial effects.

Herring (Clupea harengus) intake influences lipoproteins but not inflammatory and oxidation markers in overweight men

Fish consumption is associated with a lower incidence of CVD and decreases in risk factors for atherosclerosis. Although fish contains other interesting components than fish oil, few studies focus on total fish composition and the influence food preparation might have on health-beneficial components. In the present cross-over intervention study the effect of a 6-week herring diet compared with a reference diet on CVD risk factors was investigated. Thirty-five healthy, but overweight, men (mean BMI 28·3 kg/m2) were randomised to a 6-week herring diet (150 g baked herring fillets/d, 5 d/week) or a reference diet (150 g baked lean pork and chicken fillets/d, 5 d/week). Diets were switched after a 12-week washout period. Plasma total cholesterol, TAG, HDL, HDL2, HDL3, LDL, C-reactive protein, IL-6, IL-18, intercellular adhesion molecule-1, oxidised LDL, oxygen radical absorbance capacity using perchloric acid (ORACPCA), whole-blood fatty acids, bleeding time and blood pressure were measured at the beginning and end of each dietary period. HDL was significantly higher after the herring diet period compared with after the reference diet period: 1·04v.0·99 mmol/l. TAG decreased after both diets, with no significant difference between the two diets. ORACPCAvalues did not indicate lower concentrations of non-protein plasma antioxidants, and oxidised LDL was not higher after the herring diet than after the reference diet. To conclude, a 6-week herring-rich diet significantly raised HDL compared with a diet of matched lean pork and chicken dishes. No adverse effects onin vivooxidation or serum antioxidants were found after herring intake.

Combination effect of herring roe lipids and proteins on plasma lipids and abdominal fat weight of mouse

Dietary effects of herring roe lipids (HR-L) and proteins (HR-P) on plasma lipids and abdominal fat pad weight were determined. The main lipid class of HR-L was phospholipids (74%) and the main fatty acids were palmitic acid (16:0, 25.8%), DHA (22:6n-3, 21.6%), EPA (20:5n-3, 14.4%), and oleic acid (18:1n-9, 13.2%). A little increase in total cholesterol level was observed in plasma lipids of mouse fed with HR-L, although HR-L contained 9% cholesterol. This would be due to the lowering effect of EPA and DHA contained in HR-L on plasma cholesterol. Replacement of a part of dietary protein (5%) to HR-P reduced abdominal fat pad weight, but not significantly. On the other hand, combination of HR-P and HR-L significantly reduced the fat pad weight of the mouse as compared with the control. A significant effect of HR-P + HR-L was also observed in the reducing plasma lipid levels.

Dietary chickpeas reverse visceral adiposity, dyslipidaemia and insulin resistance in rats induced by a chronic high-fat diet

The improved effects of dietary chickpeas on visceral adiposity, dyslipidaemia and insulin resistance were examined. Rats were fed a normal-fat diet (NFD), a high-fat diet (HFD) or a high-fat plus chickpea diet (HFD+CP) for 8 months. The epididymal fat pad weight v. total body weight of rats was higher in the HFD group (0.032 (sd 0.0042) g/g) than in the NFD group (0.015 (sd 0.0064) g/g) and smaller in the HFD+CP group (0.023 (sd 0.0072) g/g) compared with the HFD group (P < 0.05). Chickpea treatment also induced a favourable plasma lipid profile reflecting decreased TAG, LDL-cholesterol (LDL-C) and LDL-C:HDL-cholesterol levels (P < 0.05). HFD-fed rats had higher TAG concentration in muscle and liver, whereas the addition of chickpeas to the HFD drastically lowered TAG concentration (muscle, 39 %; liver, 23 %). The activities of lipoprotein lipase (LPL) in epididymal adipose tissue and hepatic TAG lipase in liver recorded a 40 and 23 % increase respectively in HFD rats compared with those in NFD rats; dietary chickpeas completely normalised the levels. Furthermore, chickpea-treated obese rats also showed a markedly lower leptin and LPL mRNA content in epididymal adipose tissue. An insulin tolerance test, oral glucose tolerance test and insulin-releasing test showed that chickpeas significantly improved insulin resistance, and prevented postprandial hyperglycaemia and hyperinsulinaemia induced by the chronic HFD. The present findings provide a rational basis for the consumption of chickpeas as a functional food ingredient, which may be beneficial for correcting dyslipidaemia and preventing diabetes.

A potential role for angiotensin II in obesity induced cardiac hypertrophy and ischaemic/reperfusion injury

BACKGROUND

The mechanisms for obesity induced myocardial remodelling and subsequent mechanical dysfunction are poorly understood. There is good evidence that angiotensin II and TNFalpha have strong growth promoting properties and are elevated with obesity. In addition, these two peptides may interact to exacerbate myocardial ischaemic/reperfusion injury.

HYPOTHESIS

Obesity increases systemic and myocardial renin-angiotensin system (RAS) activity and TNFalpha levels and contributes to obesity induced cardiac remodelling and ischaemic/reperfusion injury.

METHODS

Male Wistar rats were placed on a standard rat chow diet or cafeteria diet for 16 weeks. Two additional groups of rats received the respective diets and losartan (30 mg/ kg/d) in their drinking water. Hearts were perfused on the isolated working rat heart perfusion system and mechanical function was documented before and after 15 min normothermic total global ischaemia. Blood and myocardial samples were collected for angiotensin II, TNFalpha and NADPH oxidase activity determinations.

RESULTS

The rats on the cafeteria diet became obese compared to rats on the standard rat chow (438 +/- 5.9 g vs 393 +/- 7.3 g for control, p < 0.05). Obesity was associated with elevated serum angiotensin II (0.050 +/- 0.015 pmol/ml vs. 0.035 +/- 0.003 pmol/ml, p < 0.05) and TNFalpha levels (42.8 +/- 5.93 pg/ml vs. 13.18 +/- 2.50 pg/ml, p < 0.05), and increased heart to body weight ratios (3.1 +/- 0.04 mg/g vs. 2.8 +/- 0.03 mg/g, p < 0.05). Losartan had no effect on body weight but decreased basal myocardial angiotensin II and TNFAlpha levels as well as heart to body weight ratio in the obese and lean controls (2.5 +/- 0.05 mg/g and 2.6 +/- 0.04 mg/g relative to their controls, p < 0.05). Hearts from obese rats had lower reperfusion aortic outputs (AO) than their concurrent controls (18.42 +/- 1.17 ml/min vs. 27.8 +/- 0.83 ml/min, p < 0.05). Losartan improved aortic output recoveries in obese rats (23.0 +/- 1.71 ml/min, p < 0.05).

CONCLUSIONS

Obesity increased serum angiotensin II and TNFalpha levels, blood pressure, and heart weight to body weight ratios. These changes were associated with decreased basal and post-ischaemic myocardial mechanical function. Chronic AT(1) receptor antagonism prevented the adverse changes in heart weight, mechanical function and susceptibility to ischaemic/reperfusion injury. Although current data do not exclude additional mechanisms for obesity induced cardiac remodelling, they suggest that angiotensin II may contribute to obesity induced cardiac remodelling and ischaemic/reperfusion injury.