Plant polyphenols mechanisms of action on insulin resistance and against the loss of pancreatic beta cells.

Diabetes mellitus describes a group of metabolic disorders characterized by a prolonged period hyperglycemia with long-lasting detrimental effects on the cardiovascular and nervous systems, kidney, vision, and immunity. Many plant polyphenols are shown to have beneficial activity for the prevention and treatment of diabetes, by different mechanisms. This review article is focused on synthesizing the mechanisms by which polyphenols decrease insulin resistance and inhibit loss of pancreatic islet ß-cell mass and function. To achieve the objectives, this review summarizes the results of the researches realized in recent years in clinical trials and in various experimental models, on the effects of foods rich in polyphenols, polyphenolic extracts, and commercially polyphenols on insulin resistance and ß-cells death. Dietary polyphenols are able to reduce insulin resistance alleviating the IRS-1/PI3-k/Akt signaling pathway, and to reduce the loss of pancreatic islet ß-cell mass and function by several molecular mechanisms, such as protection of the surviving machinery of cells against the oxidative insult; increasing insulin secretion in pancreatic ß-cells through activation of the FFAR1; cytoprotective effect on ß-cells by activation of autophagy; protection of ß-cells to act as activators for anti-apoptotic pathways and inhibitors for apoptotic pathway; stimulating of insulin release, presumably by transient ATP-sensitive K+ channel inhibition and whole-cell Ca2+ stimulation; involvement in insulin release that act on ionic currents and membrane potential as inhibitor of delayed-rectifier K+ current (IK(DR)) and activator of current. dietary polyphenols could be used as potential anti-diabetic agents to prevent and alleviate diabetes and its complications, but further studies are needed.

Comparative study of the influence of hawthorn (Crataegus monogyna) berry ethanolic extract and butylated hydroxylanisole (BHA) on lipid peroxidation, myoglobin oxidation, consistency and firmness of minced pork during refrigeration.

BACKGROUND: Following public concern on the use of synthetic food antioxidants, there is an increasing demand for the application of mixed or purified natural antioxidants to maintain quality of meat products quality during storage. The aim of this research was to investigate the effect of ethanolic extract of hawthorn berry, compared to butylated hydroxylanisole (BHA), on lipid peroxidation, myoglobin oxidation, protein electrophoresis pattern, consistency and firmness of minced pork during refrigeration at 4 °C, and to identify the relationship between chemical modifications and consistency variation. RESULTS: After 6 days of refrigeration it was found that the thiobarbituric acid reactive substances value of minced pork containing 200 mg GAE kg-1 total phenolics in minced meat (200 HP) was significantly lower (0.1543 ± 0.006 mg) compared to BHA-treated meat. The ratio of oxymyoglobin to metmyoglobin in treated minced pork was respectively 0.845 for 200 HP and 0.473 for BHA-treated minced meat. Concentrations of 100 HP or 300 HP will generate statistically higher firmness than BHA in minced pork. CONCLUSION: Hawthorn berry ethanolic extract was more effective than BHA in reducing lipid oxidation and protein degradation, for maintaining firmness and consistency of minced pork during 6 days of refrigeration at 4 °C. © 2017 Society of Chemical Industry.

Mechanisms of Oxidative Processes in Meat and Toxicity Induced by Postprandial Degradation Products: A Review.

Antioxidant system loss after slaughtering, reactive species production, cell disruption, contact with oxygen and light, heme and nonheme iron, and irradiation starts up mainly by 2 related oxidative processes: lipid peroxidation and protein oxidation. Products generated in these processes are responsible for meat quality loss, and some of them are suspected to be toxic to humans. This review article is focused on reactive species implicated in oxidative processes in meat, on lipid peroxidation mechanisms, heme protein, and nonheme protein oxidation, and on some toxic oxidation and digestion products. Nonenzymatic fatty acid peroxidation is exemplified by an arachidonic acyl group, and the initiation of chain reaction can be described by 3 pathways: singlet oxygen, hydroxyl radical from the Fenton reaction, and perferrylmyoglobin. Enzymatic oxidation of fatty acids is exemplified using linoleic acid, and the main characteristics of lipoxygenase are also presented. Heme protein oxidation is described in an interrelation with lipid peroxidation and the significance for food quality is shown. For protein oxidation, 3 different mechanism types are described: oxidation of amino acid residues, oxidation of protein backbone, and reactions of proteins with carbonyl compounds from lipid peroxidation. The effects of oxidative damage on protein properties and bioavailability are also shown. At the end of each oxidative process, the postprandial toxicity induced by oxidation products and the dietary degradation products are presented. Also discussed are reports by some researchers who suggest that dietary lipid and protein oxidation products and heme iron from red meat are in part cytotoxic and/or genotoxic.

Plant Polyphenols as Antioxidant and Antibacterial Agents for Shelf-Life Extension of Meat and Meat Products: Classification, Structures, Sources, and Action Mechanisms.

Oxidative processes and meat spoilage bacteria are major contributors to decreasing the shelf-life of meat and meat products. Oxidative processes occur during processing, storage, and light exposure, lowering the nutritional and sensory value and acceptability of meat and generating toxic compounds for humans. Polyphenols inhibit oxidative processes in 3 ways: as reactive species scavengers, lipoxygenase inhibitors, and reducing agents for metmyoglobin. Thus, polyphenols are candidate antioxidants for meat and meat products. The cross-contamination of meat with spoilage and pathogenic microorganisms can occur in production lines and result in economic losses. The ability of polyphenols to interact with bacterial cell wall components and the bacterial cell membrane can prevent and control biofilm formation, as well as inhibit microbial enzymes, interfere in protein regulation, and deprive bacterial cell enzymes of substrates and metal ions. Thus, polyphenols are candidate antimicrobial agents for use with meat and meat products. Commercially available polyphenols can decrease primary and secondary lipid peroxidation levels, inhibit lipoxygenase activity, improve meat color stability, minimize the degradation of salt-soluble myofibrillar protein and sulfhydryl groups, and retard bacterial growth. Further studies are now needed to clarify the synergistic/antagonistic action of various polyphenols, and to identify the best polyphenol classes, concentrations, and conditions of use.

Heat Stress in Broiler Chickens and the Effect of Dietary Polyphenols, with Special Reference to Willow (Salix spp.) Bark Supplements-A Review.

Over the last decade, there has been a growing interest in the use of a wide range of phytoadditives to counteract the harmful effects of heat stress in poultry. Willow (Salix spp.) is a tree with a long history. Among various forms, willow bark is an important natural source of salicin, ß-O-glucoside of saligenin, but also of polyphenols (flavonoids and condensed tannins) with antioxidant, antimicrobial, and anti-inflammatory activity. In light of this, the current review presents some literature data aiming to: (1) describe the relationship between heat stress and oxidative stress in broilers, (2) present or summarize literature data on the chemical composition of Salix species, (3) summarize the mechanisms of action of willow bark in heat-stressed broilers, and (4) present different biological effects of the extract of Salix species in different experimental models.

Influence of Dietary Supplementation of Salix alba Bark on Performance, Oxidative Stress Parameters in Liver and Gut Microflora of Broilers.

The paper aimed to analyse the effect of dietary Salix alba L. bark powder (SAB) on broiler performance in terms of oxidative stress parameters in liver and gut microflora. One hundred and eighty Cobb 500 broiler chicks (14 days) were allotted to three homogeneous treatments (SAB 0%; SAB 0.025%; SAB 0.05%). The broilers were housed in an environmentally controlled space (10 replicates, six broilers/replicate). Compared to dietary control treatment (SAB 0%), the other treatments included 0.025% SAB (SAB 0.025%) and 0.05% SAB (SAB 0.05%). The results showed that SAB powder used in broiler diet had a high total phenolic content. Regarding the performance results, significant differences between experimental and control treatments were recorded only for average daily feed intake (35-42 days). The broilers fed with SAB powder had a significantly lower hepatic level of malondialdehide and glutathione, a higher total antioxidant capacity than those fed control treatment, and demonstrated a positive effect on the development of non-pathogenic bacteria (lactobacilli) but a decrease in the population of pathogenic ones (E. coli, staphylococci). Our findings suggested that dietary 0.05% SAB powder could be an effective solution to impede the oxidative stress in broiler liver and to improve gut microflora.