Indirect Chronic Effects of an Oleuropein-Rich Olive Leaf Extract on Sucrase-Isomaltase In Vitro and In Vivo

Olive leaf extract effect on cardiometabolic risk factors: a systematic review and meta-analysis of randomized clinical trials

CONTEXT

Olive leaf extract (OLE) is rich in phenolic compounds, which are known for their health benefits. Cardiovascular diseases, primarily coronary heart disease and stroke, are leading causes of mortality globally.

OBJECTIVE

This systematic review aimed to assess the impact of OLE on cardiometabolic risk factors in adults. The selection of studies was based on intervention and outcomes, using relevant search descriptors.

DATA SOURCES

The databases PubMed, EMBASE, and Web of Science were systematically searched for pertinent studies published up to August 2021.

DATA EXTRACTION

Only randomized clinical trials, either cross-over or parallel, involving adult individuals aged ≥18 years, were considered. Additionally, trials that had a comparative or placebo group and used pure OLEs for oral treatment were included.

DATA ANALYSIS

Twelve randomized clinical trials (RCTs) met the inclusion criteria. These trials had follow-up periods ranging from 2 days to 12 weeks and involved 703 patients aged 18 years-79 years. The outcomes demonstrated a positive correlation between the intervention group and glucose metabolism (4 RCTs), blood pressure (2 RCTs), lipid profile (2 RCTs), and inflammatory markers (2 RCTs). The RoB2 tool and the GRADE system were used to evaluate the risk of bias and the quality of evidence in the studies.

CONCLUSIONS

In the meta-analysis, fasting glycemia, as evaluated in studies using a low dose of OLE, showed a significant result favoring the control group. To obtain more consistent results, further clinical studies in humans, using similar methodologies, are required.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42020200877.

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.

Valorizing the usage of olive leaves, bioactive compounds, biological activities, and food applications: A comprehensive review

Olive oil production is a significant source of economic profit for Mediterranean nations, accounting for around 98 percent of global output. Olive oil usage has increased dramatically in recent years, owing to its organoleptic characteristics and rising knowledge of its health advantages. The culture of olive trees and the manufacture of industrial and table olive oil produces enormous volumes of solid waste and dark liquid effluents, involving olive leaves, pomace, and olive oil mill wastewaters. These by-products cause an economic issue for manufacturers and pose major environmental concerns. As a result, partial reuse, like other agronomical production wastes, is a goal to be achieved. Because these by-products are high in bioactive chemicals, which, if isolated, might denote components with significant added value for the food, cosmetic, and nutraceutical sectors, indeed, they include significant amounts of beneficial organic acids, carbohydrates, proteins, fibers, and phenolic materials, which are distributed differently between the various wastes depending on the olive oil production method and table olive agronomical techniques. However, the extraction and recovery of bioactive materials from chosen by-products is a significant problem of their reasonable value, and rigorous detection and quantification are required. The primary aims of this review in this context are to outline the vital bioactive chemicals in olive by-products, evaluate the main developments in extraction, purification, and identification, and study their uses in food packaging systems and safety problems.

Measuring key human carbohydrate digestive enzyme activities using high-performance anion-exchange chromatography with pulsed amperometric detection

Carbohydrate digestion in the mammalian gastrointestinal tract is catalyzed by α-amylases and α-glucosidases to produce monosaccharides for absorption. Inhibition of these enzymes is the major activity of the drugs acarbose and miglitol, which are used to manage diabetes. Furthermore, delaying carbohydrate digestion via inhibition of α-amylases and α-glucosidases is an effective strategy to blunt blood glucose spikes, a major risk factor for developing metabolic diseases. Here, we present an in vitro protocol developed to accurately and specifically assess the activity of α-amylases and α-glucosidases, including sucrase, maltase and isomaltase. The assay is especially suitable for measuring inhibition by compounds, drugs and extracts, with minimal interference from impurities or endogenous components, because the substrates and digestive products in the enzyme activity assays are quantified directly by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD). Multiple enzyme sources can be used, but here we present the protocol using commercially available human α-amylase to assess starch hydrolysis with maltoheptaose as the substrate, and with brush border sucrase-isomaltase (with maltase, sucrase and isomaltase activities) derived from differentiated human intestinal Caco-2(/TC7) cells to assess hydrolysis of disaccharides. The wet-lab assay takes ~2-5 h depending on the number of samples, and the HPAE-PAD analysis takes 35 min per sample. A full dataset therefore takes 1-3 d and allows detection of subtle changes in enzyme activity with high sensitivity and reliability.

Flavonoids as Human Intestinal α-Glucosidase Inhibitors

Certain flavonoids can influence glucose metabolism by inhibiting enzymes involved in carbohydrate digestion and suppressing intestinal glucose absorption. In this study, four structurally-related flavonols (quercetin, kaempferol, quercetagetin and galangin) were evaluated individually for their ability to inhibit human α-glucosidases (sucrase, maltase and isomaltase), and were compared with the antidiabetic drug acarbose and the flavan-3-ol(−)-epigallocatechin-3-gallate (EGCG). Cell-free extracts from human intestinal Caco-2/TC7 cells were used as the enzyme source and products were quantified chromatographically with high accuracy, precision and sensitivity. Acarbose inhibited sucrase, maltase and isomaltase with IC₅₀ values of 1.65, 13.9 and 39.1 µM, respectively. A similar inhibition pattern, but with comparatively higher values, was observed with EGCG. Of the flavonols, quercetagetin was the strongest inhibitor of α-glucosidases, with inhibition constants approaching those of acarbose, followed by galangin and kaempferol, while the weakest were quercetin and EGCG. The varied inhibitory effects of flavonols against human α-glucosidases depend on their structures, the enzyme source and substrates employed. The flavonols were more effective than EGCG, but less so than acarbose, and so may be useful in regulating sugar digestion and postprandial glycaemia without the side effects associated with acarbose treatment.

Efficacy and Mechanisms of Oleuropein in Mitigating Diabetes and Diabetes Complications

The global pandemic of diabetes and diabetes complications confers heavy pressure on public health. Novel antidiabetes strategies with negligible unwanted effects are urgently needed. Currently, the anti-hyperglycemic potential of plant-based functional ingredients has been explored to provide alternative strategies. As a kind of dietary bioactive compound, oleuropein has aroused the growing interest of researchers in diabetes and diabetes complications management. This review reveals the research progress of oleuropein in treating diabetes and diabetes complications and summarizes the molecular mechanisms involved in these beneficial effects of oleuropein. Oleuropein achieves amelioration of diabetes, the mechanisms of which include the modulation of insulin secretion, the repairment islet morphology, the activation of hepatic AMP-activated protein kinase singling, and the improvement of glucose tolerance and insulin resistance. Oleuropein also can relieve diabetes complications including diabetic nephropathy, diabetes cardiovascular complications, diabetic retinopathy, poor wound healing, diabetic neuropathy, and diabetic testicular dysfunction. Oleuropein reverses cell apoptosis, regenerates tissues, restores the histological organization, and decreases oxidative stress in treating diabetes complications. Taken together, oleuropein is a promising compound for diabetes and diabetes complications management and can be used as a nutraceutical to fight against these diseases.