The Pivotal Role of Oleuropein in the Anti-Diabetic Action of the Mediterranean Diet: A Concise Review

Adherence to Mediterranean Diet and Breast Cancer Risk: A Meta-Analysis of Prospective Observational Studies

Background and Aim

The Mediterranean diet (MD) is widely recognized for its health benefits and potential protective effects against various chronic diseases such as cardiovascular conditions and cancer. This meta-analysis evaluates the association between MD adherence and breast cancer risk in women.

Methods

A comprehensive search of major databases was conducted until November 2024 to identify cohort or case-control studies. The meta-analysis employed a random-effects model to pool multivariable-adjusted effect sizes, reporting them as hazard ratios (HR) while evaluating heterogeneity using the I² statistic and assessing publication bias.

Results

The pooled analysis of 31 studies indicated a significant association between adherence to the MD and a 13% risk reduction in risk of breast cancer (HR: 0.87, 95% CI: 0.82-0.92; I 2 = 70%). Specifically, postmenopausal women exhibited a 12% significant reduction in the risk of breast cancer (HR: 0.88; 95% CI: 0.84, 0.92), while premenopausal women showed no significant effect (HR: 0.98, 95% CI: 0.90, 1.06). Geographically, the effect was most pronounced in Asia (OR: 0.59, 95% CI: 0.50, 0.68), while from America (OR: 0.92, 95% CI: 0.82, 1.02) and Europe (OR: 0.90, 95% CI: 0.83, 0.97) showed moderate associations. Subgroup analysis suggested a stronger significant association in case-control studies (HR: 0.77, 95% CI: 0.70, 0.85), whereas no significant association was observed in cohort studies (HR: 0.96, 95% CI: 0.90, 1.02).

Conclusion

Adherence to the Mediterranean diet is associated with a significant reduction in breast cancer risk, particularly among postmenopausal women and in regions such as Asia. These findings suggest that the Mediterranean diet may be an important dietary factor in reducing breast cancer risk, especially in certain populations. However, further research is needed to confirm its impact in different study designs and geographical areas.

Mediterranean diet: Why a new pyramid? An updated representation of the traditional Mediterranean diet by the Italian Society of Human Nutrition (SINU)

In recent decades, an increasing body of research has highlighted significant scientific evidence linking adherence to the Mediterranean diet with a reduced risk of chronic diseases. Simultaneously, concerns about the environmental impact of the food system have intensified, particularly considering projected population growth in the coming years. This work introduces a new graphical representation of the traditional Mediterranean dietary model, developed by a dedicated Working Group of the Italian Society of Human Nutrition (SINU). This new model emphasizes plant-based foods, including fruits, vegetables, whole grains, legumes, and extra-virgin olive oil, at its foundation, reflecting their historical and scientific significance in the Mediterranean diet. Animal products, particularly red and processed meats, are de-emphasized, with dairy, white meats, and eggs recommended for moderate, weekly consumption. The pyramid also advocates limiting added sugars, salt, and alcohol to address their links with chronic diseases. Sustainability principles are woven into the framework, prioritizing local, seasonal, and minimally processed foods while discouraging food waste. The pyramid aligns with global recommendations from FAO and WHO, offering a comprehensive guide to adopting a healthy, sustainable dietary lifestyle while preserving cultural traditions and addressing contemporary nutritional and environmental challenges.

Postprandial Glucose Response in Type 2 Diabetes Mellitus Patients and Possible Antioxidant Properties of a Plant-Based Snack Bar

Daily, more and more people consume snack bars that may have an impact on blood glucose levels. The aim of the present study was to compare the acute effects of a common snack and a plant-based snack bar (PB) that was developed at the University of Thessaly as a functional diabetic snack on blood glucose and insulin in patients with type 2 diabetes mellitus (T2DM). Adults with T2DM (n = 10) treated with oral medications were studied in a randomized, crossover clinical trial. On each trial day, postprandial glucose and insulin levels were measured at 30, 60, 90, and 120 min, and a morning snack containing 25 g of carbohydrate was consumed. The procedure was carried out on 2 days, with one of the test meals being consumed on each day. Consumption of a PB snack bar resulted in a smaller and steeper increase in postprandial glucose and insulin levels compared with the usual snack, and there were significant differences 60 and 90 min after consumption of the two tested snacks. The PB snack bar is rich in protein, fiber, vitamins, and minerals and can therefore be suggested as a nutritious and convenient snack for patients with T2DM. In addition, the extract of the snack bar was tested for its bioactivity in human cell cultures.

The impact of oleuropein on miRNAs regulating cell death signaling pathway in human cervical cancer cells

Cervical cancer is known as the second most pervasive malignancy in women across the globe. The role played by microRNAs (miRNAs) in the initiation, progression, and metastasis of this cancer has received specific attention. The use of natural compounds leading cancer cells toward apoptosis is a feasible strategy for cancer therapy. Oleuropein, an olive-extracted phenolic substance, displays anticancer properties. Here, it was attempted to assess the role played by oleuropein in cell viability in cervical cancer and changes in the expression of some miRNAs associated with cervical cancer as well as some of their possible target genes selected using bioinformatics analysis. For this purpose, HeLa cell line was exposed to several oleuropein concentrations for 48 and 72 h. After that, 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay and flow cytometry were employed to assess cell viability and apoptosis, respectively. In addition, to conduct bioinformatics analysis, Cytoscape computer program was used based on STRING database. Furthermore, to examine the role played by oleuropein in the expression of miRNAs of interest as well as their potential target genes, real-time PCR was employed. The findings indicated that oleuropein reduced cell viability through inducing apoptosis. As a result of treatment with oleuropein, miR-34a, miR-125b, and miR-29a showed increased expression levels, whereas miR-181b, miR-221, and miR-16 showed decreased expression levels. Furthermore, oleuropein reduced the expression of the anti-apoptotic genes Bcl-2 and Mcl1, whereas it elevated the expression of the pro-apoptotic Bid, Fas, and TNFRSF10B genes and the p53 tumor suppressor. Our results indicate that the apoptosis induction is a mechanism of action of oleuropein in HeLa cells. Because of its effect on the reflation of the expression of genes and miRNAs effective in the pathogenesis of cervical cancer, oleuropein shows potential as an effective research tool for developing new natural drugs for treating cervical cancer.

Role of Hydroxytyrosol and Oleuropein in the Prevention of Aging and Related Disorders: Focus on Neurodegeneration, Skeletal Muscle Dysfunction and Gut Microbiota

Aging is a multi-faceted process caused by the accumulation of cellular damage over time, associated with a gradual reduction of physiological activities in cells and organs. This degeneration results in a reduced ability to adapt to homeostasis perturbations and an increased incidence of illnesses such as cognitive decline, neurodegenerative and cardiovascular diseases, cancer, diabetes, and skeletal muscle pathologies. Key features of aging include a chronic low-grade inflammation state and a decrease of the autophagic process. The Mediterranean diet has been associated with longevity and ability to counteract the onset of age-related disorders. Extra virgin olive oil, a fundamental component of this diet, contains bioactive polyphenolic compounds as hydroxytyrosol (HTyr) and oleuropein (OLE), known for their antioxidant, anti-inflammatory, and neuroprotective properties. This review is focused on brain, skeletal muscle, and gut microbiota, as these systems are known to interact at several levels. After the description of the chemistry and pharmacokinetics of HTyr and OLE, we summarize studies reporting their effects in in vivo and in vitro models of neurodegenerative diseases of the central/peripheral nervous system, adult neurogenesis and depression, senescence and lifespan, and age-related skeletal muscle disorders, as well as their impact on the composition of the gut microbiota.

Recent Advances in Health Benefits of Bioactive Compounds from Food Wastes and By-Products: Biochemical Aspects

Bioactive compounds, including terpenoids, polyphenols, alkaloids and other nitrogen-containing constituents, exert various beneficial effects arising from their antioxidant and anti-inflammatory properties. These compounds can be found in vegetables, fruits, grains, spices and their derived foods and beverages such as tea, olive oil, fruit juices, wine, chocolate and beer. Agricultural production and the food supply chain are major sources of food wastes, which can become resources, as they are rich in bioactive compounds. The aim of this review is to highlight recent articles demonstrating the numerous potential uses of products and by-products of the agro-food supply chain, which can have various applications.

Neuroprotective Panel of Olive Polyphenols: Mechanisms of Action, Anti-Demyelination, and Anti-Stroke Properties

Neurological diseases such as stroke and multiple sclerosis are associated with high morbidity and mortality, long-term disability, and social and economic burden. Therefore, they represent a major challenge for medical treatment. Numerous evidences support the beneficial effects of polyphenols from olive trees, which can alleviate or even prevent demyelination, neurodegeneration, cerebrovascular diseases, and stroke. Polyphenols from olive oils, especially extra virgin olive oil, olive leaves, olive leaf extract, and from other olive tree derivatives, alleviate inflammation and oxidative stress, two major factors in demyelination. In addition, they reduce the risk of stroke due to their multiple anti-stroke effects, such as anti-atherosclerotic, antihypertensive, antioxidant, anti-inflammatory, hypocholesterolemic, hypoglycemic, and anti-thrombotic effects. In addition, olive polyphenols have beneficial effects on the plasma lipid profiles and insulin sensitivity in obese individuals. This review provides an updated version of the beneficial properties and mechanisms of action of olive polyphenols against demyelination in the prevention/mitigation of multiple sclerosis, the most common non-traumatic neurological cause of impairment in younger adults, and against cerebral insult with increasing incidence, that has already reached epidemic proportions.