Beneficial effect of walnuts on vascular tone is associated with Akt signalling, voltage-dependent calcium channel LTCC and ATP-sensitive potassium channel Kv1.2

Unlocking the Cardiovascular Benefits of Walnuts: Insights on Molecular Mechanism From Animal Studies

The health-promoting benefits of walnut consumption are substantially ascribed to its fatty acid (FA) profile, which is rich in polyunsaturated FA with an exceptionally high n-3 to n-6 ratio. There are also phytonutrients in walnuts that are linked to health welfare. This review article integrates all studies on the effects of walnuts on the cardiovascular system performed on experimental animals, and thus is a source of data on the mechanisms underlying the observed effects. These studies, which are very diverse in experimental design, indicate that a diet enriched with walnuts or treating animals with walnut extract or chemical constituents of walnuts, has many favorable effects on heart and vascular system function. The cardiovascular effect of walnuts depends on the metabolic status of the organism. Among the cardiovascular effects of walnuts is that they improve the FA profile in the circulation and heart in favor of n-3 polyunsaturated FAs. In addition, a favorable effect on triglyceride and cholesterol status, which reduces cardiovascular disease risk, is observed. Intake of walnuts promotes FA catabolism and has anti-inflammatory, antioxidant, and antiarrhythmic effects. Walnuts also have a beneficial effect on vascular tone, accompanied by a decrease in blood pressure and reduced risk for atherosclerosis. In conclusion, studies on experimental animals encourage the consumption of walnuts as a simple, convenient approach to improve cardiovascular health.

Walnut supplementation increases levels of UCP1 and CD36 in brown adipose tissue independently of diet type

Dietary interventions that modulate the brown adipose tissue (BAT) thermogenic activity could represent a promising therapy for metabolic disorders. In order to examine if dietary walnuts intake regulates the expression of BAT thermogenic markers levels in healthy and metabolically challenged (fructose fed) animals, rats were initially divided into the control and fructose-fed groups. After nine weeks, these groups were subdivided into the one kept on the original regimens and the other supplemented with walnuts. High-fructose diet resulted in an increased relative BAT mass and no change in UCP1 content, while the walnut supplementation increased the amount of UCP1 in BAT, but did not affect 5-HT, NA, DHPG content and DHPG/NA ratio regardless of the diet. Moreover, the CD36 levels were increased following the walnut consumption, unlike FATP1, GLUT1, GLUT4, and glycogen content which remained unchanged. Additionally, the BAT levels of activated IR and Akt were not affected by walnut consumption, while ERK signaling was decreased. Overall, we found that walnut consumption increased UCP1 and CD36 content in the BAT of both control and metabolically challenged rats, suggesting that FFAs represent the BAT preferred substrate under the previously described circumstances. This further implies that incorporating walnuts into the everyday diet may help to alleviate some symptoms of the metabolic disorder.

Can daily consumption of enriched fatty acids diet be effective in improving metabolic syndrome? An attractive paradox for walnut kernel

Imagine consuming a daily diet rich in fatty acids to help treat diseases such as hypertension and obesity. This concept presents an attractive paradox. In particular, consuming walnut kernels is beneficial for treating diseases associated with metabolic syndrome (MetS), including type 2 diabetes, cardiovascular disease, dyslipidemia, and obesity. Different parts of the Juglans regia tree (family Juglandaceae), including its leaves, green husks, bark, and septum, have shown promising effects on pathological conditions related to MetS. The therapeutic advantages of consuming walnut kernels for MetS can be attributed to the presence of polyunsaturated fatty acids and polyphenolic compounds such as juglone and ellagic acid. Diets enriched with walnut kernel have a positive impact on MetS complications by reducing diastolic blood pressure, improving blood lipid profiles, lowering fasting blood sugar levels, and increasing insulin sensitivity. The potential cellular mechanisms responsible for these benefits involve activating the cholesterol hemostasis pathway by inhibiting sterol regulatory element-binding proteins (SREBPs), proprotein convertase subtilisin/kexin type 9 (PCSK9), and cholesteryl ester transfer protein (CETP). Furthermore, other by-products of walnuts, such as leaves and green husks, have also demonstrated effectiveness in managing MetS. These findings highlight the potential of incorporating walnut-based products into our diets as a natural approach to combating MetS and its complications.

Ginkgo biloba modulates ET-I/NO signalling in Lead Acetate induced rat model of endothelial dysfunction: Involvement of oxido-inflammatory mediators

This study investigated the modulatory effect of Ginkgo biloba extract on lead acetate-induced endothelial dysfunction. Animals were administered GBE (50 mg/kg and 100 mg/kg orally) after exposures to lead acetate (25 mg/kg orally) for 14 days. Aorta was harvested after euthanasia, the tissue was homogenised, and supernatants were decanted after centrifuging. Oxidative, nitrergic, inflammatory, and anti-apoptotic markers were assayed using standard biochemical procedure, ELISA, and immunohistochemistry, respectively. GBE reduced lead-induced oxidative stress by increasing SOD, GSH, and CAT as well as reducing MDA levels in endothelium. Pro-inflammatory cytokines (TNF-α and IL-6) were reduced while increasing Bcl-2 protein expression. GBE lowered endothelin-I and raised nitrite levels. Histological changes caused by lead acetate were normalised by GBE. Our findings suggest that Ginkgo biloba extract restored endothelin-I and nitric oxide functions by increasing Bcl-2 protein expression and reducing oxido-inflammatory stress in endothelium.

Effects of Walnut-Rich Diet on Cation-Handling Proteins in the Heart of Healthy and Metabolically Compromised Male Rats

The transport of cations in the cardiomyocytes, crucial for the functioning of the heart, can be affected by walnut diet due to the high content of polyunsaturated fatty acids. Healthy and metabolically compromised rats (drinking 10% fructose solution) were subjected to a diet supplemented with 2.4 g of walnuts for 6 weeks to investigate the effect on proteins involved in cation transport in the heart cells. Fructose increased the level of the α1 subunit of Na+/K+-ATPase and the phosphorylation of extracellular signal-regulated kinase 1/2 in the heart of control and walnut-eating rats, while elevated L-type calcium channel α (LTCCα), sodium-calcium exchanger 1 (NCX1), and Maxi Kα level were observed only in rats that did not consume walnuts. However, walnuts significantly increased the cardiac content of LTCC, NCX1, and Maxi Kα, as well as Kir6.1 and SUR2B subunits of KATP channel, but only in fructose-naive rats. In animals that drank fructose, a significant increasing effect of walnuts was observed only in Akt kinase phosphorylation, which may be a part of the antiarrhythmic mechanism of decreasing cation currents in cardiomyocytes. The walnut diet-induced increase in LTCC and NCX1 expression in healthy rats may indicate intense cardiac calcium turnover, whereas the effect on Kir6.1 and SUR2B subunits suggests stimulation of KATP channel transport in the cardiac vasculature. The effects of walnuts on the cation-handling proteins in the heart, mostly limited to healthy animals, suggest the possible use of a walnut-supplemented diet in the prevention rather than the treatment of cardiological channelopathies.

Walnut supplementation after fructose-rich diet is associated with a beneficial fatty acid ratio and increased ACE2 expression in the rat heart

Increased fructose consumption has been linked with chronic inflammation and metabolic syndrome (MetS). Activation of the renin-angiotensin system (RAS) and NF-κB have been detected in MetS. Walnuts are a rich source of polyunsaturated omega-3 fatty acids (n-3 PUFA) that were suggested to exert anti-inflammatory effects related to cardio-metabolic health. We hypothesized that walnut supplementation has the capacity to revert unfavorable fructose-rich diet (FRD)-induced activation of cardiac RAS and NF-κB in male rats. Due to the lack of similar studies, we investigated the effects of walnut supplementation (6 weeks) on the expression of four RAS molecules (ACE, ACE2, AT1R, and AT2R) and NF-κB in rat heart after FRD (10% w/v, 9 weeks). In addition, we followed the changes in the n-6/n-3 PUFA ratio in the total pool of heart lipids after both treatments to elucidate the walnut effects on fatty acids in the heart. 36 animals (9 per group) participated in the experiment. FRD significantly increased the ACE protein level in the heart (p < 0.001). Walnut supplementation significantly increased the ACE2 protein level in the heart of FRD (p < 0.001). In addition, walnut supplementation showed a significant main effect on the arachidonic acid/eicosapentaenoic acid ratio (p = 0.004). Walnut supplementation significantly reduced this ratio, in comparison with both, the control group (C vs. FW, p < 0.05) and the FRD group (F vs. FW, p < 0.05). However, walnut treatment failed to revert the significant effect of fructose (p < 0.001) on the elevation of NF-κB protein level. Our results suggest a beneficial effect of walnut supplementation on ACE2 protein level and n-6/n-3 PUFA level in the heart of the animal model of MetS. Such results highlight the approach of omega-3-rich walnut supplementation in the stimulation of endogenous production of favorable molecules in the heart which could be an affordable nutritional treatment formaintenance of cardio-metabolic health.

Consumption of walnuts suppresses the conversion of palmitic to palmitoleic acid and enhances omega-3 fatty acid metabolism in the heart of fructose-fed rats

Walnut consumption mostly has a positive implication for cardiovascular health. Walnut diet effects on the cardiac fatty acid (FA) metabolism of healthy rats and those with fructose diet-induced metabolic burden were analysed. Both walnuts and fructose increased CD36 transporter level and the nuclear content of some/all of Lipin 1/PPARα/PGC-1 complex partners, as well as cytosolic and nuclear FOXO1. However, fructose, independently of walnuts, increased the content of palmitic (PA), oleic, and vaccenic acid (VA), while in walnut-fed rats failed to increase palmitoleic acid (POA) level and the POA/PA ratio, as well as total MUFA content. In opposite, walnuts reduced the level of PA and VA and increased alpha-linolenic, eicosapentaenoic and docosapentaenoic acid level, regardless of fructose. In conclusion, both fructose and walnuts stimulated the uptake and oxidation of FA in the heart, but the walnuts, opposite to fructose, favourably altered cardiac FA profile in healthy and metabolically compromised rats.

Effect of Brazil Nuts on Selenium Status, Blood Lipids, and Biomarkers of Oxidative Stress and Inflammation: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Tree nuts, including Brazil nuts, have been hypothesized to impact cardiovascular health through the modulation of oxidative stress and inflammation. Nonetheless, a quantitative analysis of these effects has not been performed. Therefore, the aim of this study was to systematically revise and quantify the effect of Brazil nut intervention on selenium status, blood lipids, and biomarkers of oxidative stress and inflammation using a meta-analytical approach. To meet the goals of this study, a systematic search of PubMed, EMBASE, and Web of Science databases of published randomised clinical trials reporting on dietary interventions with Brazil nuts and their effects on selenium status, blood lipids, and markers of oxidative stress and inflammation was performed. Eight articles were included for systematic review and meta-analysis. Based on the conducted analysis, a significant positive effect of Brazil nuts on selenium blood concentration (SMD = 6.93, 95% CI: 3.99; 9.87) was found. Additionally, a positive effect of Brazil nut intervention on glutathione peroxidase activity (SMD = 0.53, 95% CI: 0.07; 0.99) was observed. However, no significant results were found when considering blood lipid levels, including results for total cholesterol (SMD = −0.22, 95% CI: −0.57; 0.14), HDL cholesterol (SMD = −0.04, 95% CI: −0.28; 0.19) and LDL cholesterol (SMD = −0.15; 95% CI: −0.43; 0.13). In conclusion, the findings from this study suggest that Brazil nut consumption improves selenium status and exerts antioxidant effects, which could be considered a potential pathway for the prevention of metabolic disorders related to altered blood lipid profiles. However, further studies are needed to elucidate the effect of Brazil nuts toward blood lipid profile, also preferably controlling for other biomarkers.

Effect of Peroxyl Radical-Induced Oxidation on Functional and Structural Characteristics of Walnut Protein Isolates Revealed by High-Resolution Mass Spectrometry

The present study aims to investigate the structural and functional properties of oxidated walnut protein isolates (WPI) by 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH). The oxidation degree, changes in structural characteristics, processing properties, and protein modifications of WPI were measured. The results showed that oxidation significantly induced structural changes, mainly reflected by the increasing carbonyl content, and decreasing sulfhydryl and free amino groups. Moreover, the secondary structure of WPI was altered in response to oxidation, and large aggregates formed through disulfide cross-linking and hydrophobic interactions. Almost all the property indicators were significantly decreased by oxidation except the foaming property and water/oil holding capacity. Mass spectrometry analysis showed that 16 different modifications occurred in amino acid side chains, and most of the protein groups with higher numbers of modifications were found to be associated with allergies, which was further confirmed by the reduction in antigenicity of the major allergen (Jug r 1) in WPI. Meanwhile, we used oxidation-related proteins for gene ontology (GO) enrichment analyses, and the results indicated that 115, 204 and 59 GO terms were enriched in terms of biological process, molecular function, and cellular component, respectively. In conclusion, oxidation altered the groups and conformation of WPI, which in turn caused modification in the functional properties correspondingly. These findings might provide a reference for processing and storage of walnut protein foods.

Walnut Supplementation Restores the SIRT1-FoxO3a-MnSOD/Catalase Axis in the Heart, Promotes an Anti-Inflammatory Fatty Acid Profile in Plasma, and Lowers Blood Pressure on Fructose-Rich Diet

The benefits of walnut (Juglans regia) consumption for metabolic health are known, but the molecular background underlying their putative antioxidant and anti-inflammatory/immunomodulatory effects is underexplored. We assessed that walnut supplementation (6 weeks) reverted unfavorable changes of the SIRT1/FoxO3a/MnSOD/catalase axis in the heart induced by fructose-rich diet (FRD). Intriguingly, Nox4 was increased by both FRD and walnut supplementation. FRD increased the cytosolic fraction and decreased the nuclear fraction of the uniquely elucidated ChREBP in the heart. The ChREBP nuclear fraction was decreased in control rats subjected to walnuts. In addition, walnut consumption was associated with a reduction in systolic BP in FRD and a decrease in fatty acid AA/EPA and AA/DHA ratios in plasma. In summary, the protective effect of walnut supplementation was detected in male rats following the fructose-induced decrease in antioxidative/anti-inflammatory capacity of cardiac tissue and increase in plasma predictors of low-grade inflammation. The current results provide a novel insight into the relationship between nutrients, cellular energy homeostasis, and the modulators of inflammatory/immune response in metabolic syndrome, emphasizing the heart and highlighting a track for translation into nutrition and dietary therapeutic approaches against metabolic disease.

Walnut Consumption Induces Tissue-Specific Omega-6/Omega-3 Decrease in High-Fructose-Fed Wistar Rats

Increased dietary, blood, and tissue n-6/n-3 fatty acid ratios are associated with obesity and metabolic syndrome. Due to Westernized dietary patterns, the increasing n-6/n-3 ratio is of growing concern worldwide, and dietary strategies aimed at its lowering are of public health importance. Walnuts are rich in dietary fats, and their consumption promotes cardiometabolic health. This study aimed to examine the effect of 6-week walnut consumption on tissue-specific n-6/n-3 ratio and fatty acid metabolic conversion in fructose-fed rats with a cluster of metabolic disorders. Male Wistar rats were fed a standard diet with or without 10% fructose in drinking water for 9 weeks. Diets of half of the animals were then supplemented with walnuts (2.4 g/day) for 6 weeks, upon which fatty acid profiles were determined in plasma, liver, adipose tissue, and kidney total lipids. Results showed that walnuts induced significant decreases in the n-6/n-3 content of total lipid pool in plasma and examined tissues, irrespective of metabolic burden. Walnut intervention decreased plasma and liver palmitoleic/palmitic, arachidonic/linoleic, and docosahexaenoic/α-linolenic acid ratios. It also modulated individual fatty acid levels by reducing arachidonic and palmitic acid and increasing α-linolenic, eicosapentaenoic, and docosapentaenoic acid in plasma and most tissues. Our study demonstrated that 6-week consumption of walnuts favorably modulated n-6/n-3 plasma and tissue ratio in male Wistar rats regardless of high-fructose feeding, underscoring the promising potential of walnuts in both prevention and treatment of the metabolic syndrome.