Hydroxytyrosol ameliorates metabolic, cardiovascular and liver changes in a rat model of diet-induced metabolic syndrome: Pharmacological and metabolism-based investigation

Cardioprotective potential of oleuropein, hydroxytyrosol, oleocanthal and their combination: Unravelling complementary effects on acute myocardial infarction and metabolic syndrome

Clinical studies have previously established the role of olive products in cardiovascular disease (CVD) prevention, whilst the identification of the responsible constituents for the beneficial effects is still pending. We sought to assess and compare the cardioprotective potential of oleuropein (OL), hydroxytyrosol (HT), oleocanthal (OC) and oleanolic Acid (OA), regarding Ischemia/Reperfusion Injury (IRI) and CVD risk factors alleviation. The scope of the study was to design a potent and safe combinatorial therapy for high-cardiovascular-risk patients on a bench-to-bedside approach. We evaluated the IRI-limiting potential of 6-weeks treatment with OL, HT, OC or OA at nutritional doses, in healthy and metabolic syndrome (MS)-burdened mice. Three combinatorial regimens were designed and the mixture with preponderant benefits (OL-HT-OC, Combo 2), including infarct sparing and antiglycemic potency, compared to the isolated compounds, was further investigated for its anti-atherosclerotic effects. In vivo experiments revealed that the combination regimen of Combo 2 presented the most favorable effects in limiting infarct size and hyperglycemia, which was selected to be further investigated in the clinical setting in Chronic Coronary Artery Syndrome (CCAS) patients. Cardiac function, inflammation markers and oxidative stress were assessed at baseline and after 4 weeks of treatment with the OL-HT-OC supplement in the clinical study. We found that OL, OC and OA significantly reduced infarct size in vivo compared to Controls. OL exhibited antihyperglycemic properties and OA attenuated hypercholesterolemia. OL-HT-OA, OL-HT-OC and OL-HT-OC-OA combination regimens were cardioprotective, whereas only OL-HT-OC mitigated hyperglycemia. Combo 2 cardioprotection was attributed to apoptosis suppression, enhanced antioxidant effects and upregulation of antioxidant enzymes. Additionally, it reduced atherosclerotic plaque extent in vivo. OL-HT-OC supplement ameliorated cardiac, vascular and endothelial function in the small-scale clinical study. Conclusively, OL-HT-OC combination therapy exerts potent cardioprotective, antihyperglycemic and anti-atherosclerotic properties in vivo, with remarkable and clinically translatable cardiovascular benefits in high-risk patients.

Ifanosine: Olea europaea L. and Hyphaene thebaica L. combination, from traditional utilization to rational formulation: Preclinical and clinical efficacy on hypertensives patients

ETHNOPHARMACOLOGICAL RELEVANCE

Olea europaea L. and Hyphaene thebaica L. are commonly employed by traditional healers in Africa for treating and preventing hypertension, either individually or in a polyherbal preparation (Ifanosine).

AIM OF THE STUDY

The primary aim was to assess the antihypertensive effects of Olea europaea L. leaves aqueous extract (OEL), Hyphaene thebaica L. mesocarp extract (HT), and the Ifanosine on isolated rat aorta rings. The secondary objective was to evaluate the clinical benefits of a new oral formulation of Ifanosine.

MATERIALS AND METHODS

In vitro studies using an isometric transducer examined the antihypertensive effects of HT, OEL, and Ifanosine on rat aorta. Ussing chambers technic were employed to measure mucosal to serosal fluxes and total transepithelial electrical conductance (Gt) to assess the intestinal bioavailability of HT, OEL, and Ifanosine. HPLC was utilized to determine the phytochemical composition of OEL and HT extracts. Subchronic toxicity investigations involved two groups of rats, treated with either water (control) or Ifanosine at 5 g/kg for 28 days. Clinical benefits of the new Ifanosine formulation were evaluated in an observational study with 32 hypertensive patients receiving a fixed oral dose of 3.5 mg three times a day for 30 days.

RESULTS

Aqueous extracts induced dose-dependent relaxation of rat aorta rings, with HT and OEL having higher IC50 values than Ifanosine (IC50 = 44.76 ± 1.35 ng/mL, 58.67 ± 1.02 ng/mL, and 29.46 ± 0.26 ng/mL, respectively). The pA2 values of OEL and HT were 1 and 0.6, respectively, while Ifanosine was 0.06. Intestinal bioavailability studies revealed better Prazosin bioavailability than plant extracts. Toxicological studies demonstrated the safety of Ifanosine, supported by histological examinations and biochemical parameters in rat blood. Biochemical analyses indicated flavonoids and phenolic acids as dominant active constituents. Clinical benefits in humans included reduced SBP, DBP, LDL-c, VLDL-c, and TAG, and increased HDL-c without overt adverse effects.

CONCLUSION

This study validates the traditional use of OEL and HT for hypertension and advocates for alternative and combinatorial polyphytotherapy (ACP) to enhance traditional remedies.

The Short-Term Effect of Olive Oil Extract Enriched with Hydroxytyrosol on Cardiovascular Function

Olive is rich in polyphenols such as hydroxytyrosol (HT) that have antioxidative and anti-inflammatory effects. In this study, we examined the short-term effects of olive oil extract (OE) enriched with HT on left atrial function, left ventricular (LV) function, and arterial elastic properties in patients with chronic coronary artery disease (CAD). Sixty-one patients with chronic CAD were enrolled. This randomized study had a two-period, two-sequence crossover (AB/BA) design. Group AB (n = 32) initially received OE capsules (500 mg) enriched with HT (5 mg) (two capsules/day) for 30 days, and after a wash out of 48 h, placebo for another 30 days. The opposite occurred in Group BA (n = 29). Exclusion criteria included age >70 years, diabetes, anemia, hypertension, liver and thyroid disease, malignancy, autoimmune disease, kidney disease, use of corticosteroids, weight loss, excessive exercise dietary intervention, and use of antioxidant vitamins. Patients underwent echocardiography/Doppler and applanation tonometry applied to radial artery at the beginning and end of the study. No significant change regarding Vmax, Vp, Vmin, E wave, A wave, deceleration time, LV ejection fraction, central aortic systolic and pulse pressure, and augmentation index. However, a trend toward improvement of E/e' (P = .062) and pulse wave velocity (P = .091) was observed. Use of OE enriched with HT for a limited time period was associated with a trend toward improvement of LV diastolic function and aortic elastic properties in chronic CAD patients. Studies of longer duration are needed to delineate the effect of this promising agent on cardiovascular function and outcomes in chronic CAD.

Hydroxytyrosol produced by engineered Escherichia coli strains activates Nrf2/HO-1 pathway: An in vitro and in vivo study

This study explores the biological effects of hydroxytyrosol (HT), produced by the metabolic engineering of Escherichia coli, in a series of in vitro and in vivo experiments. In particular, a metabolically engineered Escherichia coli strain capable of producing HT was constructed and utilized. HEK293 and HeLa cells were exposed to purified HT to determine non-toxic doses that can offer protection against oxidative stress (activation of Nrf2/HO-1 signaling pathway). Male CD-1 mice were orally supplemented with HT to evaluate (1) renal and hepatic toxicity, (2) endogenous system antioxidant response, and (3) activation of Nrf2/HO-1 system in the liver. HT protected cells from oxidative stress through the activation of Nrf2 regulatory network. Activation of Nrf2 signaling pathway was also observed in the hepatic tissue of the mice. HT supplementation was safe and produced differential effects on mice's endogenous antioxidant defense system. HT biosynthesized from genetically modified Escherichia coli strains is an alternative method to produce high-quality HT that exerts favorable effects in the regulation of the organism's response to oxidative stress. Nonetheless, further investigation of the multifactorial action of HT on the antioxidant network regulation is needed.

Targeting Metabolic Syndrome in Hidradenitis Suppurativa by Phytochemicals as a Potential Complementary Therapeutic Strategy

Hidradenitis suppurativa (HS) is a chronic inflammatory disease characterized by the appearance of painful inflamed nodules, abscesses, and pus-draining sinus tracts in the intertriginous skin of the groins, buttocks, and perianal and axillary regions. Despite its high prevalence of ~0.4-1%, therapeutic options for HS are still limited. Over the past 10 years, it has become clear that HS is a systemic disease, associated with various comorbidities, including metabolic syndrome (MetS) and its sequelae. Accordingly, the life expectancy of HS patients is significantly reduced. MetS, in particular, obesity, can support sustained inflammation and thereby exacerbate skin manifestations and the chronification of HS. However, MetS actually lacks necessary attention in HS therapy, underlining the high medical need for novel therapeutic options. This review directs attention towards the relevance of MetS in HS and evaluates the potential of phytomedical drug candidates to alleviate its components. It starts by describing key facts about HS, the specifics of metabolic alterations in HS patients, and mechanisms by which obesity may exacerbate HS skin alterations. Then, the results from the preclinical studies with phytochemicals on MetS parameters are evaluated and the outcomes of respective randomized controlled clinical trials in healthy people and patients without HS are presented.

Metabolomic-Based Studies of the Intake of Virgin Olive Oil: A Comprehensive Review

Virgin olive oil (VOO) is a high-value product from the Mediterranean diet. Some health and nutritional benefits have been associated with its consumption, not only because of its monounsaturated-rich triacylglycerols but also due to its minor bioactive components. The search for specific metabolites related to VOO consumption may provide valuable information to identify the specific bioactive components and to understand possible molecular and metabolic mechanisms implicated in those health effects. In this regard, metabolomics, considered a key analytical tool in nutritional studies, offers a better understanding of the regulatory functions of food components on human nutrition, well-being, and health. For that reason, the aim of the present review is to summarize the available scientific evidence related to the metabolic effects of VOO or its minor bioactive compounds in human, animal, and in vitro studies using metabolomics approaches.

Table olive elicits antihypertensive activity in spontaneously hypertensive rats

BACKGROUND

Table olives are a food with a high content of bioactive compounds with cardioprotective properties, such as oleic acid, polyphenols, and pentacyclic triterpenes. Here, we investigate the effect of the intake of table olives on blood pressure (BP) and body weight in spontaneously hypertensive rats (SHR) and their normotensive controls, Wistar Kyoto (WKY) rats. 'Arbequina' table olives (3.85 g kg^-1 ) were administered by gavage to SHR and WKY rats in short-term (1 day) and long-term (7 weeks) experiments. BP was measured by the tail-cuff method, and polyphenols and triterpenes were determined in olives and plasma by liquid chromatography-mass spectrometry.

RESULTS

Administration of 'Arbequina' olives to WKY rats did not exert any change in BP in any of the experiments. However, in SHR, the single dose induced a transient reduction in BP of approximately 15 mmHg, from the second to the tenth hour after the administration. In the long-term assay, a similar decrease was established in the second week and was maintained throughout the experiment. Moreover, the daily administration of olives to rats did not affect their body weight when compared with controls in either the WKY rats or SHR. The determination of polyphenols and triterpenes in plasma indicated that, at the end of the experiment, only maslinic acid, oleanolic acid, hydroxytyrosol, and luteolin were found, all of them being compounds with already described capacity to decrease BP.

CONCLUSION

The results suggest that the daily intake of table olives could decrease BP in hypertension without affecting body weight, indicating that table olives could contribute to improving cardiovascular health. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The Effect of the Extra Virgin Olive Oil Minor Phenolic Compound 3',4'-Dihydroxyphenylglycol in Experimental Diabetic Kidney Disease

The aim of this study was to analyze the possible nephroprotective effect of 3',4'-dihydroxyphenylglycol (DHPG), a polyphenolic compound of extra virgin olive oil (EVOO), on renal lesions in an experimental model of type 1 diabetes. Rats were distributed as follows: healthy normoglycemic rats (NDR), diabetic rats treated with saline (DR), and DR treated with 0.5 mg/kg/day or 1 mg/kg/day of DHPG. DR showed a significantly higher serum and renal oxidative and nitrosative stress profile than NDR, as well as reduced prostacyclin production and renal damage (defined as urinary protein excretion, reduced creatinine clearance, increased glomerular volume, and increased glomerulosclerosis index). DHPG reduced the oxidative and nitrosative stress and increased prostacyclin production (a 59.2% reduction in DR and 34.7-7.8% reduction in DHPG-treated rats), as well as 38-56% reduction in urinary protein excretion and 22-46% reduction in glomerular morphological parameters (after the treatment with 0.5 or 1 mg/kg/day, respectively). Conclusions: DHPG administration to type 1-like diabetic rats exerts a nephroprotective effect probably due to the sum of its antioxidant (Pearson's coefficient 0.68-0.74), antinitrosative (Pearson's coefficient 0.83), and prostacyclin production regulator (Pearson's coefficient 0.75) effects.

Phosphorus Supplementation Mitigates Perivascular Adipose Inflammation-Induced Cardiovascular Consequences in Early Metabolic Impairment

Background

The complexity of the interaction between metabolic dysfunction and cardiovascular complications has long been recognized to extend beyond simple perturbations of blood glucose levels. Yet, structured interventions targeting the root pathologies are not forthcoming. Growing evidence implicates the inflammatory changes occurring in perivascular adipose tissue (PVAT) as early instigators of cardiovascular deterioration.

Methods and Results

We used a nonobese prediabetic rat model with localized PVAT inflammation induced by hypercaloric diet feeding, which dilutes inorganic phosphorus (Pi) to energy ratio by 50%, to investigate whether Pi supplementation ameliorates the early metabolic impairment. A 12‐week Pi supplementation at concentrations equivalent to and twice as much as that in the control diet was performed. The localized PVAT inflammation was reversed in a dose‐dependent manner. The increased expression of UCP1 (uncoupling protein1), HIF‐1α (hypoxia inducible factor‐1α), and IL‐1β (interleukin‐1β), representing the hallmark of PVAT inflammation in this rat model, were reversed, with normalization of PVAT macrophage polarization. Pi supplementation restored the metabolic efficiency consistent with its putative role as an UCP1 inhibitor. Alongside, parasympathetic autonomic and cerebrovascular dysfunction function observed in the prediabetic model was reversed, together with the mitigation of multiple molecular and histological cardiovascular damage markers. Significantly, a Pi‐deficient control diet neither induced PVAT inflammation nor cardiovascular dysfunction, whereas Pi reinstatement in the diet after a 10‐week exposure to a hypercaloric low‐Pi diet ameliorated the dysfunction.

Conclusions

Our present results propose Pi supplementation as a simple intervention to reverse PVAT inflammation and its early cardiovascular consequences, possibly through the interference with hypercaloric‐induced increase in UCP1 expression/activity.

Protective effect of olive leaves phenolic compounds against neurodegenerative disorders: Promising alternative for Alzheimer and Parkinson diseases modulation

The main objective of this work was to review literature on compounds extracted from olive tree leaves, such as simple phenols (hydroxytyrosol) and flavonoids (Apigenin, apigenin-7-O-glucoside, luteolin.) and their diverse pharmacological activities as antioxidant, antimicrobial, anti-viral, anti-obesity, anti-inflammatory and neuroprotective properties. In addition, the study discussed the key mechanisms underlying their neuroprotective effects. This study adopted an approach of collecting data through the databases provided by ScienceDirect, SCOPUS, MEDLINE, PubMed and Google Scholar. This review revealed that there was an agreement on the great impact of olive tree leaves phenolic compounds on many metabolic syndromes as well as on the most prevalent neurodegenerative diseases such as Alzheimer and Parkinson. These findings would be of great importance for the use of olive tree leaves extracts as a food supplement and/or a source of drugs for many diseases. In addition, this review would of great help to beginning researchers in the field since it would offer them a general overview of the studies undertaken in the last two decades on the topic.

Nephroprotective Effect of the Virgin Olive Oil Polyphenol Hydroxytyrosol in Type 1-like Experimental Diabetes Mellitus: Relationships with Its Antioxidant Effect

The aim of this study was to determine whether hydroxytyrosol administration prevented kidney damage in an experimental model of type 1 diabetes mellitus in rats. Hydroxytyrosol was administered to streptozotocin-diabetic rats: 1 and 5 mg/kg/day p.o. for two months. After hydroxytyrosol administration, proteinuria was significantly reduced (67-73%), calculated creatinine clearance was significantly increased (26-38%), and the glomerular volume and glomerulosclerosis index were decreased (20-30%). Hydroxytyrosol reduced oxidative and nitrosative stress variables and thromboxane metabolite production. Statistical correlations were found between biochemical and kidney function variables. Oral administration of 1 and 5 mg/kg/day of hydroxytyrosol produced an antioxidant and nephroprotective effect in an experimental model of type 1-like diabetes mellitus. The nephroprotective effect was significantly associated with the systemic and renal antioxidant action of hydroxytyrosol, which also influenced eicosanoid production.

Natural and synthetic antioxidants targeting cardiac oxidative stress and redox signaling in cardiometabolic diseases

Cardiometabolic diseases (CMDs) are metabolic diseases (e.g., obesity, diabetes, atherosclerosis, rare genetic metabolic diseases, etc.) associated with cardiac pathologies. Pathophysiology of most CMDs involves increased production of reactive oxygen species and impaired antioxidant defense systems, resulting in cardiac oxidative stress (OxS). To alleviate OxS, various antioxidants have been investigated in several diseases with conflicting results. Here we review the effect of CMDs on cardiac redox homeostasis, the role of OxS in cardiac pathologies, as well as experimental and clinical data on the therapeutic potential of natural antioxidants (including resveratrol, quercetin, curcumin, vitamins A, C, and E, coenzyme Q10, etc.), synthetic antioxidants (including N-acetylcysteine, SOD mimetics, mitoTEMPO, SkQ1, etc.), and promoters of antioxidant enzymes in CMDs. As no antioxidant indicated for the prevention and/or treatment of CMDs has reached the market despite the large number of preclinical and clinical studies, a sizeable translational gap is evident in this field. Thus, we also highlight potential underlying factors that may contribute to the failure of translation of antioxidant therapies in CMDs.

Diagnostic Criteria for Metabolic Syndrome in Diet-Induced Rodent Models: A Systematic Review

BACKGROUND

Thousands of publications in recent years have addressed the induction of metabolic syndrome (MetS) in rodents. However, the criteria and the reference values for diagnosing this disease have not been defined.

OBJECTIVE

Our main objective was to carry out a systematic review to gather evidence about the criteria for biochemical and anthropometric parameters in which scientific studies have relied on to report that rats developed MetS from a previous dietary manipulation.

METHODS

We compiled characteristics and findings of diet-induced MetS with high-fat, high-carbohydrate, high-fat/high-carbohydrates, and cafeteria diet from PubMed and Science Direct databases published in the last 5 years.

RESULTS

The results on the principal determinants for the syndrome, published in the reviewed articles, were chosen to propose reference values in the rat models of food induction.

CONCLUSION

The values obtained will serve as reference cut-of points in the development of the disease; in addition, the compilation of data will be useful in planning and executing research protocols in animal models.

Diet to Reduce the Metabolic Syndrome Associated with Menopause. The Logic for Olive Oil

The rates of metabolic syndrome are increasing in parallel with the increasing prevalence of obesity, primarily due to its concomitant insulin resistance. This is particularly concerning for women, as the years around menopause are accompanied by an increase in visceral obesity, a strong determinant of insulin resistance. A fall in estrogens and increase in the androgen/estrogen ratio is attributed a determining role in this process, which has been confirmed in other physiological models, such as polycystic ovary syndrome. A healthy lifestyle, with special emphasis on nutrition, has been recommended as a first-line strategy in consensuses and guidelines. A consistent body of evidence has accumulated suggesting that the Mediterranean diet, with olive oil as a vital component, has both health benefits and acceptable adherence. Herein, we provide an updated overview of current knowledge on the benefits of olive oil most relevant to menopause-associated metabolic syndrome, including an analysis of the components with the greatest health impact, their effect on basic mechanisms of disease, and the state of the art regarding their action on the main features of metabolic syndrome.

Extrapolation of hydroxytyrosol and its analogues as potential anti-inflammatory agents

Discovery of potential lead molecule is a challenging, and complex process which require lots of money, patience, and manpower. Human beings are using natural products, predominantly secondary metabolites, for this purpose since ancient time and they are still working on them as a potent source for drug discovery due to their wide structural diversity. Phenolic phytochemicals such as hydroxytyrosol and tyrosol are natural antioxidant and involved in many biological disease cure. Herein, we have carried out the quantum chemical calculations for conformational analysis, geometry optimization and computation of electronic as well as optical properties of hydroxytyrosol and its analogues (1a-1k) in terms of density functional theory by using Gaussian 09 program suite. The eventual charge transfer within the molecules has been confirmed by the analysis of frontier molecular orbitals. The molecular docking studies of 1a-1k with cyclooxygenase-2 showed the noticeable binding affinity as compared to other nonsteroidal anti-inflammatory drugs viz. aspirin, naproxen and celecoxib. Computation of pharmacokinetics and pharmacological properties confirmed the lead/drug like potential of these screened molecules. Furthermore, the molecular dynamics simulation of best three docked ligands (1f, 1h and 1k)-receptor complex and their binding free energy calculations reveals that these molecules bind in the catalytic cavity of cyclooxygenase-2 and found stable during the 100 ns of simulation. Communicated by Ramaswamy H. Sarma.

Is Extra Virgin Olive Oil an Ally for Women's and Men's Cardiovascular Health?

Noncommunicable diseases are long-lasting and slowly progressive and are the leading causes of death and disability. They include cardiovascular diseases (CVD) and diabetes mellitus (DM) that are rising worldwide, with CVD being the leading cause of death in developed countries. Thus, there is a need to find new preventive and therapeutic approaches. Polyphenols seem to have cardioprotective properties; among them, polyphenols and/or minor polar compounds of extra virgin olive oil (EVOO) are attracting special interest. In consideration of numerous sex differences present in CVD and DM, in this narrative review, we applied "gender glasses." Globally, it emerges that olive oil and its derivatives exert some anti-inflammatory and antioxidant effects, modulate glucose metabolism, and ameliorate endothelial dysfunction. However, as in prescription drugs, also in this case there is an important gender bias because the majority of the preclinical studies are performed on male animals, and the sex of donors of cells is not often known; thus a sex/gender bias characterizes preclinical research. There are numerous clinical studies that seem to suggest the benefits of EVOO and its derivatives in CVD; however, these studies have numerous limitations, presenting also a considerable heterogeneity across the interventions. Among limitations, one of the most relevant in the era of personalized medicine, is the non-attention versus women that are few and, also when they are enrolled, sex analysis is lacking. Therefore, in our opinion, it is time to perform more long, extensive and lessheterogeneous trials enrolling both women and men.

Antihypertensive phytocomplexes of proven efficacy and well-established use: Mode of action and individual characterization of the active constituents

Hypertension has become the leading risk factor for worldwide cardiovascular diseases. Conventional pharmacological treatment, after both dietary and lifestyle changes, is generally proposed. In this review, we present the antihypertensive properties of phytocomplexes from thirteen plants, long ago widely employed in ethnomedicines and, in recent years, increasingly evaluated for their activity in vitro and in vivo, also in humans, in comparison with synthetic drugs acting on the same systems. Here, we focus on the demonstrated or proposed mechanisms of action of such phytocomplexes and of their constituents proven to exert cardiovascular effects. Almost seventy phytochemicals are described and scientifically sound pertinent literature, published up to now, is summarized. The review emphasizes the therapeutic potential of these natural substances in the treatment of the 'high normal blood pressure' or 'stage 1 hypertension', so-named according to the most recent European and U.S. guidelines, and as a supplementation in more advanced stages of hypertension, however needing further validation by clinical trial intensification.

Comparative Study on Beneficial Effects of Hydroxytyrosol- and Oleuropein-Rich Olive Leaf Extracts on High-Fat Diet-Induced Lipid Metabolism Disturbance and Liver Injury in Rats

Oleuropein and hydroxytyrosol, as major compounds of olive leaves, have been reported to exert numerous pharmacological properties, including anticancer, antidiabetic, and anti-inflammatory activities. The purpose of this study is to evaluate and compare the protective effect of oleuropein- and hydroxytyrosol-rich extracts, derived from olive leaves, on high-fat diet-induced lipid metabolism disturbance and liver injury in rats. In this respect, four groups of male rats (8 per group) were used: control group (Control), group treated with high-fat diet (HFD), group treated with HFD and oleuropein (HFD + OLE), and group treated with HFD and hydroxytyrosol (HFD + HYD). The current research showed that the treatment with the HFD increased the body weight and adipose tissue mass in male rats. Moreover, the plasma levels of triglycerides, total cholesterol, LDL-cholesterol, AST, ALT, LDH, and TNF-α were also raised. The hepatic immunohistochemical analysis revealed a significant increase in the expression of inflammatory genes (COX-2, NF-κB, and TNF-α). Equally, it showed a rise of the apoptotic markers (a decrease in the expression of the Bcl-2 and an increase of the P53). In addition, the oral administration of oleuropein- and hydroxytyrosol-rich olive leaf extracts at 16 mg/kg similarly reduced the body weight and adipose tissue mass and improved the lipid profile. Moreover, these extracts, mainly the hydroxytyrosol-rich extract, reduced the elevated liver enzymes, enhanced the antioxidant status, and attenuated the liver inflammation and apoptosis. These findings suggest that the oleuropein- and hydroxytyrosol-rich olive leaf extracts possessed hypolipidemic and hepatoprotective effects against the HFD-induced metabolic disorders by enhancing the antioxidative defense system and blocking the expression of the proteins involved in inflammation and liver damage.

Hydroxytyrosol prevents PM2.5-induced adiposity and insulin resistance by restraining oxidative stress related NF-κB pathway and modulation of gut microbiota in a murine model

Exposure to fine particular matter (≤2.5 μM, PM_2.5) contributes to increased risk of obesity and type 2 diabetes. Hydroxytyrosol (HT), a simple polyphenol found in virgin olive oil, is considered to be beneficial for cardiovascular and metabolic disorders. The current study determined whether HT could improve PM_2.5-induced adiposity and insulin resistance (IR), and explored the underlying mechanisms. Fifteen adult female C57BL/6j mice on a chow diet were randomly divided into three groups receiving (1) sterile PBS, (2) PM_2.5 suspended in sterile PBS (1 mg/mL) and (3) PM_2.5+HT (50 mg/kg/day). PM_2.5/PBS exposure was administered by oropharynx instillation every other day and HT supplementation was achieved by gavage every day. Four-week PM_2.5 exposure did not affect body weight, but significantly increased visceral fat mass. The abdominal adiposity coincided with adipocyte hypertrophy and proliferation in visceral white adipose tissue (WAT), as well as decreased metabolic activity in brown adipose tissue and subcutaneous WAT. PM_2.5 enhanced the oxidative stress by diminishing antioxidant enzyme activities in liver and serum, whereas contents of 4-hydroxynonenal (4-HNE), malondialdehyde (MDA) levels in liver and serum were elevated. These changes were accompanied by macrophage infiltration and activation of NF-κB pathway in the liver. Moreover, PM_2.5 exposure led to glucose intolerance and insulin insensitivity, impaired hepatic glycogenesis, and decreased insulin-stimulated Akt phosphorylation in peripheral tissues. Importantly, HT treatment prevented PM_2.5-induced visceral adipogenesis, oxidative stress, hepatic inflammation and NF-κB activation, systemic and peripheral IR. In vitro, after HepG2 cells were incubated with PM_2.5 (0, 5, 25, 50, 100 and 200 μg/mL), reduced glutathione depletion and 4-HNE, 8-hydroxy-2'-deoxyguanosine, MDA increment in a dose-dependent manner were observed; likewise, insulin-stimulated glucose uptake decreased in a dose-dependent manner. Further, with antioxidant NAC and NF-κB inhibitor PDTC, we confirmed that HT attenuated PM_2.5-induced IR through restraining NF-κB activation evoked by oxidative stress. In addition, HT could expand gut microbiota richness, reduce pathogenic bacteria and accommodate the microbial architecture in PM_2.5-exposed mice, which were correlated with parameters of adiposity, oxidative stress and glycometabolism. HT could effectively correct imbalanced oxidative stress triggered by PM_2.5, in turn ameliorated NF-κB pathway and insulin signaling. Gut microbiota may mediate the actions of HT.

Antidiabetic Effects of Hydroxytyrosol: In Vitro and In Vivo Evidence

Insulin resistance, a pathological condition characterized by defects in insulin action leads to the development of Type 2 diabetes mellitus (T2DM), a disease which is currently on the rise that pose an enormous economic burden to healthcare systems worldwide. The current treatment and prevention strategies are considerably lacking in number and efficacy and therefore new targeted therapies and preventative strategies are urgently needed. Plant-derived chemicals such as metformin, derived from the French lilac, have been used to treat/manage insulin resistance and T2DM. Other plant-derived chemicals which are not yet discovered, may have superior properties to prevent and manage T2DM and thus research into this area is highly justifiable. Hydroxytyrosol is a phenolic phytochemical found in olive leaves and olive oil reported to have antioxidant, anti-inflammatory, anticancer and antidiabetic properties. The present review summarizes the current in vitro and in vivo studies examining the antidiabetic properties of hydroxytyrosol and investigating the mechanisms of its action.

Comparison of the anti-angiogenic potential of hydroxytyrosol and five derivatives

Hydroxytyrosol is a phenolic compound present in extra virgin olive oil, either in free form or as derivatives, and related to some of the health benefits described for olive oil intake. We have demonstrated previously that hydroxytyrosol inhibits angiogenesis both in vitro and in vivo. In the present study, we evaluate the anti-angiogenic potential of five hydroxytyrosol derivatives. Three of these derivatives contain a nitro group and they exhibit a much weaker effect than hydroxytyrosol in the tubule formation assay on Matrigel and therefore were not studied further. In contrast, both hydroxytyrosyl acetate and ethyl hydroxytyrosyl ether show more potent inhibitory effects than hydroxytyrosol in both the in vitro tubule formation assay on Matrigel and the in vivo chorioallantoic membrane assay. Additionally, these three compounds had slight pro-apoptotic effects and decreased matrix metalloproteinase-2 levels in cell extracts.

Hydroxytyrosol protects against myocardial ischemia reperfusion injury by inhibiting mitochondrial permeability transition pore opening

Hydroxytyrosol (HT), a phenolic compound extracted from olive oil, is reported to protect against myocardial ischemia reperfusion injury (MIRI), but its mechanism has not been fully elucidated. The mitochondria permeability transition pore (MPTP) is an important therapeutic target for MIRI. The present study aimed to investigate the role of MPTP in the cardioprotection of HT. Isolated rat hearts were mounted on a Langendorff apparatus and subjected to 30 min of ischemia followed by 120 min of reperfusion to mimic a MIRI model. Isolated hearts were pretreated with different doses of HT (10, 100 and 1,000 µM) for 10 min prior to ischemia. Myocardial infarct size was detected using TTC staining. Changes in myocardial cell structure were observed using hematoxylin and eosin staining. MPTP opening was detected spectrophotometrically. Myocardial cell apoptosis was observed with terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling assays. The expression of apoptosis-associated proteins was measured by western blot analysis. The data revealed that HT (100 and 1,000 µM) treatment significantly alleviated pathological damage in ischemic myocardium and reduced myocardial infarct size compared with the untreated control. However, no significant difference was observed in the 10 µM HT treatment group compared with the untreated control. It was further revealed that HT decreased the B cell lymphoma-2 (Bcl-2)-like protein 4 (Bax)/Bcl-2 ratio, suppressed MPTP opening and subsequently decreased the expression of cytochrome c, cleaved caspase-9 and -3, thereby inhibiting apoptosis. Additionally, the beneficial effects of HT on MIRI were reversed by atractyloside, which induces MPTP opening. In conclusion, the present study demonstrated that HT inhibited MPTP opening, partially via modulation of Bax and Bcl-2, thereby protecting against MIRI and thereby providing a pharmacological basis for future research and treatment of MIRI.

Significant metabolic improvement by a water extract of olives: animal and human evidence

PURPOSE

Dyslipidemia and impaired glucose metabolism are the main health issues of growing prevalence and significant high healthcare cost, requiring novel prevention and/or therapeutic approaches. Epidemiological and animal studies revealed that olive oil is an important dietary constituent, inducing normolipidemia. However, no studies have specifically investigated the polyphenol-rich water extract of olives (OLWPE), generated during olive oil production.

METHODS

In the present work, we initially examined the effect of OLPWE on animals' metabolic parameters. Rats fed with a high-fat diet were treated with three different doses of OLPWE for 4 months. Additionally, bioavailability was explored. Afterwards, OLWPE's metabolic effect was explored in humans. Healthy volunteers consumed microencapsulated OLWPE for 4 weeks, in a food matrix [one portion (30 g) of a meat product].

RESULTS

High-fat-fed rats developed a metabolic dysfunction, with increased LDL and insulin levels and decreased HDL; this syndrome was significantly impaired when treated with OLWPE. Treated rats had increased total plasma antioxidant capacity, while several phenolic compounds were detected in their blood. These findings were also verified in humans that consumed OLWPE, daily, for 4 weeks. Interestingly, in individuals with elements of cardio-metabolic risk, OLWPE consumption resulted in reduced glucose, insulin, total cholesterol, LDL and oxLDL levels.

CONCLUSIONS

Our data clearly show that OLWPE can improve glucose and lipid profile, indicating its possible use in the design of functional food and/or therapeutic interventions.

Comparative Analysis of the Effects of Olive Oil Hydroxytyrosol and Its 5-S-Lipoyl Conjugate in Protecting Human Erythrocytes from Mercury Toxicity

Oxidative stress is one of the underlying mechanisms of the toxic effects exerted by mercury (Hg) on human health. Several antioxidant compounds, including the olive oil phenol hydroxytyrosol (HT), were investigated for their protective action. Recently, we have reported that 5-S-lipoylhydroxytyrosol (Lipo-HT) has shown increased antioxidant activities compared to HT and exerted potent protective effects against reactive oxygen species (ROS) generation and oxidative damage in human hepatocellular carcinoma HepG2 cell lines. In this study, the effects of Lipo-HT and HT on oxidative alterations of human erythrocytes induced by exposure to 40 μM HgCl₂ were comparatively evaluated. When administered to the cells, Lipo-HT (5–20 μM) proved nontoxic and it decreased the Hg-induced generation of ROS, the hemolysis, and the depletion of intracellular GSH levels. At all tested concentrations, Lipo-HT exhibited higher ability to counteract Hg-induced cytotoxicity compared to HT. Model studies indicated the formation of a mercury complex at the SH group of Lipo-HT followed by a redox reaction that would spare intracellular GSH. Thus, the enhanced erythrocyte protective action of Lipo-HT from Hg-induced damage with respect to HT is likely due to an effective chelating and reducing ability toward mercury ions. These findings encourage the use of Lipo-HT in nutraceutical strategies to contrast heavy metal toxicity in humans.

Hydroxytyrosol ameliorates insulin resistance by modulating endoplasmic reticulum stress and prevents hepatic steatosis in diet-induced obesity mice

Endoplasmic reticulum (ER) is a principal organelle responsible for energy and nutrient management. Its dysfunction has been viewed in the context of obesity and related glucolipid metabolic disorders. However, therapeutic approaches to improve ER adaptation and systemic energy balance in obesity are limited. Thus, we examined whether hydroxytyrosol (HT), an important polyphenolic compound found in virgin olive oil, could correct the metabolic impairments in diet-induced obesity (DIO) mice. Here, we found that HT gavage for 10 weeks significantly ameliorated glucose homeostasis and chronic inflammation and decreased hepatic steatosis in DIO mice. At the molecular level, ER stress indicators, inflammatory and insulin signaling markers demonstrated that high-fat diet (HFD)-induced ER stress and insulin resistance (IR) in insulin sensitive tissue were corrected by HT. In vitro studies confirmed that HT supplementation (100 μM) attenuated palmitate-evoked ER stress, thus rescuing the downstream JNK/IRS pathway. As a result from suppression of ER stress in the liver, HT further decreased hepatic sterol regulatory element-binding protein-1 expression (SREBP1). Additionally, aberrant expression of genes involved in hepatic lipogenesis (SREBP1, ACC, FAS, SCD1) caused by HFD was restored by HT. These findings suggested that HT ameliorated chronic inflammation and IR and decreased hepatic steatosis in obesity by beneficial modulation of ER stress.

Food Components in Health Promotion and Disease Prevention

The current obesity epidemic with its deleterious effects on public health and the increase in the prevalence of non-communicable diseases in our aging society have dramatically increased public awareness of nutrition-related health issues. On one hand, food components, such as fat, sugar, flavors, and spices, are major determinants of the hedonic value of food, and the constant and almost ubiquitous availability of good-tasting food in our affluent societies promotes overeating and weight gain. On the other hand, several food components, including flavoring compounds and the active ingredients of many plants, such as spices and herbs (e.g., polyphenols and capsaicinoids) or thylakoids, supposedly can decrease food intake and affect gastrointestinal function and metabolism. These substances may act as antioxidants, may stimulate the release of incretins and, hence, insulin, and may improve insulin sensitivity or decrease plasma levels of lipids. Such beneficial effects are often difficult to demonstrate in epidemiological studies because they may occur only at supraphysiological doses and/or when the purified compounds are administered, but they can be present under certain circumstances. This review discusses the putative mechanisms of the health-promoting and disease-preventing effects of some food components and their potential physiological relevance, primarily with respect to counteracting obesity and type 2 diabetes.

Natural products for the treatment of type 2 diabetes mellitus: Pharmacology and mechanisms

Epidemiological studies have implied that diabetes mellitus (DM) will become an epidemic accompany with metabolic and endocrine disorders worldwide. Most of DM patients are affected by type 2 diabetes mellitus (T2DM) with insulin resistance and insulin secretion defect. Generally, the strategies to treat T2DM are diet control, moderate exercise, hypoglycemic and lipid-lowing agents. Despite the therapeutic benefits for the treatment of T2DM, most of the drugs can produce some undesirable side effects. Considering the pathogenesis of T2DM, natural products (NPs) have become the important resources of bioactive agents for anti-T2DM drug discovery. Recently, more and more natural components have been elucidated to possess anti-T2DM properties, and many efforts have been carried out to elucidate the possible mechanisms. The aim of this paper was to overview the activities and underlying mechanisms of NPs against T2DM. Developments of anti-T2DM agents will be greatly promoted with the increasing comprehensions of NPs for their multiple regulating effects on various targets and signal pathways.

The relationship between lipid phytochemicals, obesity and its related chronic diseases

This review focuses on phytochemicals in oils, and summarizes the mechanisms of the anti-obesity effects of these compounds in in vitro studies, animal models, and human trials.

Molecular adaptations underlying the beneficial effects of hydroxytyrosol in the pathogenic alterations induced by a high-fat diet in mouse liver: PPAR-α and Nrf2 activation, and NF-κB down-regulation

SCOPE

Non-alcoholic fatty liver disease (NAFLD) is a condition characterized by an increment in the liver fat content, with a concomitant reduction in the content of n-3-long chain polyunsaturated fatty acids (n-3 LCPUFAs), downregulation of PPAR-α activity, and upregulation of NF-κB activity, effects that induce pro-lipogenic and pro-inflammatory responses. Hydroxytyrosol (HT), a polyphenol with cytoprotective effects present in extra virgin olive oil, improves the cellular antioxidant capacity for activation of transcription factor Nrf2. The objective of this work is to evaluate the molecular adaptations involved in the anti-lipogenic, anti-inflammatory, and anti-oxidant effects of HT supplementation in high-fat diet (HFD)-fed mice.

METHODS AND RESULTS

Male C57BL/6J mice received (i) control diet (10% fat); (ii) control diet + HT (daily doses of 5 mg per kg body weight), (iii) HFD (60% fat); or (iv) HFD + HT for 12 weeks. HFD-fed mice exhibited (i) liver steatosis; (ii) inflammation; (iii) oxidative stress; and (iv) depletion of n-3 LCPUFAs, together with down-regulation of PPAR-α and Nrf2, and up-regulation of NF-κB. HT supplementation attenuated the metabolic alterations produced by HFD, normalizing the activity of Nrf2, reducing the drop in activity of PPAR-α, and attenuating increment of NF-κB activation.

CONCLUSION

Supplementation with HT activating transcription factors PPAR-α and Nrf2, along with the deactivation of NF-κB, may reduce the liver alterations induced in HFD-fed mice.

Hydroxytyrosol restores proper insulin signaling in an astrocytic model of Alzheimer's disease

Recent epidemiological evidence demonstrated that diabetes is a risk factor for AD onset and development. Indeed, meta-analyses of longitudinal epidemiologic studies show that diabetes increases AD risk by 50-100%, being insulin resistance (IR) the main binding link between diabetes and AD. Astrocytes are the foremost cerebral macroglial cells and are responsible for converting glucose into lactate and transfer it to neurons that use it as fuel, but Aβ(1-42) impairs insulin signaling and glycogen storage. Recent prospective studies showed that the Mediterranean diet is associated with lower incidence of AD. We hypothesized that hydroxytyrosol (HT, the preeminent polyphenol of olives and olive oil) could exert beneficial effects on IR associated with AD and investigated it mechanisms of action in an astrocytic model of AD. The astrocytic cell line C6 was exposed to Aβ(25-35) and co-incubated with HT for different periods. After treatment with Aβ(25-35), astrocytes' viability was significantly decreased as compared with controls; however, both pre- and post-treatment with HT prevented this effect. Mechanistically, we found that the preventive role of HT on Aβ(25-35)- induced cytotoxicity in astrocytes is moderated by an increased HT-induced activation of Akt, which is mediated by the insulin signaling pathway. In addition, we report that HT prevented the pronounced activation of mTOR, thereby restoring proper insulin signaling. In conclusion, we demonstrate that HT protects Aβ(25-35)-treated astrocytes by improving insulin sensitivity and restoring proper insulin-signaling. These data provide some mechanistic insight on the observed inverse association between olive oil consumption and prevalence of cognitive impairment. © 2017 BioFactors, 43(4):540-548, 2017.