Proanthocyanidins are the major anti-diabetic components of cinnamon water extract

Pomegranate peel, chokeberry leaves and Ironwort extract as novel natural inhibitors of amylin aggregation and cellular toxicity in pancreatic β cells

Impeding or reducing human amylin aggregation and/or its toxicity can be key to preventing pancreatic islet amyloidosis and β-cell loss in patients with Type 2 Diabetes Mellitus (T2DM). Here, Punica granatum (pomegranate) peel, Sideritis raeseri (ironwort) and Aronia melanocarpa (chokeberry) leaf extracts, were tested for their novel anti-aggregative and antitoxic properties in human amylin (hIAPP) treated rat pancreatic insulinoma (INS) cells. The protein aggregation (Th-T) assay revealed an inhibitory trend of all three plant extracts against amylin aggregates. In agreement with this finding, pomegranate peel and ironwort extracts effectively prevented the transition of hIAPP from disordered, random coil structures into aggregation prone β-sheet enriched molecular assemblies, revealed by CD spectroscopy. Consistent with their anti-aggregative action, all three extracts prevented, to various degrees, reactive oxygen species (ROS) accumulation, mitochondrial stress, and, ultimately, apoptosis of INS cells. Collectively, the results from this study demonstrate effectiveness of natural products to halt hIAPP aggregation, redox stress, and toxicity, which could be exploited as novel therapeutics against amylin-derived islet amyloidosis and β-cell stress in T2DM.

Effects of Cinnamon Powder on Glucose Metabolism in Diabetic Mice and the Molecular Mechanisms

The liver is the primary organ regulating glucose metabolism. In our recent study, cinnamon improved liver function in diabetic mice. However, it is not clear whether cinnamon can reduce the glycemia of diabetic animals by regulating liver glucose metabolism. The purpose of this study was to investigate the hypoglycemic mechanism of cinnamon powder (CP) from the perspective of regulating liver glucose metabolism. To achieve this, different doses of CP (200, 400, or 800 mg/kg body weight) were given to diabetic mice by gavage once per day for 8 weeks. These mice were compared with healthy controls, untreated diabetic mice, and diabetic mice treated with metformin (the main first-line drug for type 2 diabetes). CP treatment effectively reduced fasting blood glucose levels and food intake, improved glucose tolerance and fasting serum insulin levels, and decreased glycated serum protein levels in diabetic mice. Furthermore, treatment with CP increased liver glycogen content and reduced the level of the gluconeogenesis precursor pyruvate in the liver. Data obtained by qPCR and western blotting suggested that CP improved glucose metabolism disorders by regulating AMPKα/PGC1α-mediated hepatic gluconeogenesis and PI3K/AKT-mediated hepatic glycogen synthesis. CP exhibits good hypoglycemic effects by improving hepatic glycogen synthesis and controlling hepatic gluconeogenesis. Therefore, CP may be applied as a functional food to decrease blood glucose.

Nonionizing Electromagnetic Irradiations; Biological Interactions, Human Safety

Human is usually exposed to environmental radiation from natural and man-made sources. Therefore, it is important to investigate the effects of exposure to environmental radiation, partly related to understanding and protecting against the risk of exposure to environmental radiation with beneficial and adverse impacts on human life. The rapid development of technologies causes a dramatic enhancement of radiation in the human environment. In this study, we address the biological effects caused by different fractions of non-ionizing electromagnetic irradiation to humans and describe possible approaches for minimizing adverse health effects initiated by radiation. The main focus was on biological mechanisms initiated by irradiation and represented protection, and safety approaches to prevent health disorders.

Prospective Nutraceutical Effects of Cinnamon Derivatives Against Insulin Resistance in Type II Diabetes Mellitus-Evidence From the Literature

Apart from advances in pharmaceutical antidiabetic agents, efforts are being made toward hypoglycemic agents derived from natural sources. Cinnamon has been reported to have significant benefits for human health, particularly as an anti-inflammatory, antidiabetic, and anti-hypertriglyceridemic agent. The phytochemicals in cinnamon can be extracted from different parts of plant by distillation and solvent extraction. These chemicals help in decreasing insulin resistance and can act against hyperglycemia and dyslipidemia, inflammation and oxidative stress, obesity, overweight, and abnormal glycation of proteins. Cinnamon has shown to improve all of these conditions in in vitro, animal, and/or human studies. However, the mechanism of action of active ingredients found in cinnamon remains unclear. The current review presents the outstanding ability of cinnamon derivatives to control diabetes by various pathways modulating insulin release and insulin receptor signaling. It was also found that the type and dosage of cinnamon as well as subject characteristics including drug interactions are likely to affect the response to cinnamon. Future research directions based on this review include the synergistic usage of various cinnamon derivatives in managing and/or preventing diabetes and possible other relevant chronic diseases.

Aqueous Extract of Cinnamon (Cinnamomum spp.): Role in Cancer and Inflammation

Cinnamon (Cinnamomum spp.; family Lauraceae), a plant widely used as a spice and flavoring agent and in the perfume industry, has high therapeutic value. However, the components and chemical properties of cinnamon extracts vary depending on the part of the plant, the method, and the solvent used for extraction. Green extraction methods using safe and green solvents have gained increased interest in recent years. Water is an environmentally friendly and safe green solvent widely used for preparing cinnamon extracts. This review focuses on the various preparation techniques for the aqueous extract of cinnamon, its major bioactive components, and their beneficial roles in different pathological conditions, specifically cancer and inflammation. The aqueous extract of cinnamon contains several bioactive compounds, such as cinnamaldehyde, cinnamic acid, and polyphenols, and exerts anticancer and anti-inflammatory properties by altering key apoptotic and angiogenic factors. The whole extract is a better anticancer and anti-inflammatory agent than the purified fractions, indicating a synergistic effect between various components. Studies have indicated that aqueous cinnamon extract has immense therapeutic potential, and to better understand its synergistic effects, extensive characterization of the aqueous extract and its potential to be used with other therapies should be explored.

Probing the interactions between amyloidogenic proteins and bio-membranes

Protein misfolding diseases (PMDs) in humans are characterized by the deposition of protein aggregates in tissues, including Alzheimer's disease, Parkinson's disease, type 2 diabetes, and amyotrophic lateral sclerosis. Misfolding and aggregation of amyloidogenic proteins play a central role in the onset and progression of PMDs, and these processes are regulated by multiple factors, especially the interaction between proteins and bio-membranes. Bio-membranes induce conformational changes in amyloidogenic proteins and affect their aggregation; on the other hand, the aggregates of amyloidogenic proteins may cause membrane damage or dysfunction leading to cytotoxicity. In this review, we summarize the factors that affect the binding of amyloidogenic proteins and membranes, the effects of bio-membranes on the aggregation of amyloidogenic proteins, mechanisms of membrane disruption by amyloidogenic aggregates, technical approaches for detecting these interactions, and finally therapeutic strategies targeting membrane damage caused by amyloidogenic proteins.

Proanthocyanidins at the gastrointestinal tract: mechanisms involved in their capacity to mitigate obesity-associated metabolic disorders

The prevalence of overweight and obesity is continually increasing worldwide. Obesity is a major public health concern given the multiple associated comorbidities. Finding dietary approaches to prevent/mitigate these conditions is of critical relevance. Proanthocyanidins (PACs), oligomers or polymers of flavan-3-ols that are extensively distributed in nature, represent a major part of total dietary polyphenols. Although current evidence supports the capacity of PACs to mitigate obesity-associated comorbidities, the underlying mechanisms remain speculative due to the complexity of PACs' structure. Given their limited bioavailability, the major site of the biological actions of intact PACs is the gastrointestinal (GI) tract. This review discusses the actions of PACs at the GI tract which could underlie their anti-obesity effects. These mechanisms include: i) inhibition of digestive enzymes at the GI lumen, including pancreatic lipase, α-amylase, α-glucosidase; ii) modification of gut microbiota composition; iii) modulation of inflammation- and oxidative stress-triggered signaling pathways, e.g. NF-κB and MAPKs; iv) protection of the GI barrier integrity. Further understanding of the mechanisms and biological activities of PACs at the GI tract can contribute to develop nutritional and pharmacological strategies oriented to mitigate the serious comorbidities of obesity.

Beneficial effects of cinnamon and its extracts in the management of cardiovascular diseases and diabetes

Cardiovascular diseases (CVDs) and diabetes are the leading causes of death worldwide, which underlines the urgent necessity to develop new pharmacotherapies. Cinnamon has been an eminent component of spice and traditional Chinese medicine for thousands of years. Numerous lines of findings have elucidated that cinnamon has beneficial effects against CVDs in various ways, including endothelium protection, regulation of immune response, lowering blood lipids, antioxidative properties, anti-inflammatory properties, suppression of vascular smooth muscle cell (VSMC) growth and mobilization, repression of platelet activity and thrombosis and inhibition of angiogenesis. Furthermore, emerging evidence has established that cinnamon improves diabetes, a crucial risk factor for CVDs, by enhancing insulin sensitivity and insulin secretion; regulating the enzyme activity involved in glucose; regulating glucose metabolism in the liver, adipose tissue and muscle; ameliorating oxidative stress and inflammation to protect islet cells; and improving diabetes complications. In this review, we summarized the mechanisms by which cinnamon regulates CVDs and diabetes in order to provide a theoretical basis for the further clinical application of cinnamon.

Computational study and in vitro alpha-glucosidase inhibitory effects of medicinal plants from a Thai folk remedy

The number of patients with type 2 diabetes mellitus (T2DM) has increased worldwide. Although an instant cure was achieved with the standard treatment acabose, unsatisfactory symptoms associated with cardiovascular disease after acabose administration have been reported. Therefore, it is important to explore new treatments. A Thai folk recipe has long been used for T2DM treatment, and it effectively decreases blood glucose. However, the mechanism of this recipe has never been proven. Therefore, the potential anti-T2DM effect of this recipe, which is used in Thai hospitals, was determined to involve alpha-glucosidase (AG) inhibition with a half maximal inhibitory concentration (IC50). In vitro experiments showed that crude Cinnamomum verum extract (IC50 = 0.35 ± 0.12 mg/mL) offered excellent inhibitory activity, followed by extracts from Tinospora crispa (IC50 = 0.69 ± 0.39 mg/mL), Stephania suberosa (IC50 = 1.50 ± 0.17 mg/mL), Andrographis paniculate (IC50 = 1.78 ± 0.35 mg/mL), and Thunbergia laurifolia (IC50 = 4.66 ± 0.27 mg/mL). However, the potencies of these extracts were lower than that of acabose (IC50 = 0.55 ± 0.11 mg/mL). Therefore, this study investigated and developed a formulation of this recipe using computational docking. Among 61 compounds, 7 effectively inhibited AG, including chlorogenic acid (IC50 = 819.07 pM) through 5 hydrogen bonds (HBs) and 2 hydrophobic interactions (HIs); β-sitosterol (IC50 = 4.46 nM, 6 HIs); ergosterol peroxide (IC50 = 4.18 nM, 6 HIs); borapetoside D (IC50 = 508.63 pM, 7 HBs and 2 HIs); borapetoside A (IC50 = 1.09 nM, 2 HBs and 2 His), stephasubimine (IC50 = 285.37 pM, 6 HIs); and stephasubine (IC50 = 1.09 nM, 3 HBs and 4 HIs). These compounds bind with high affinity to different binding pockets, leading to additive effects. Moreover, the pharmacokinetics of six of these seven compounds (except ergosterol peroxide) showed poor absorption in the gastrointestinal tract, which would allow for competitive binding to AG in the small intestine. These results indicate that the development of these 6 compounds into oral antidiabetic agents is promising.

Cinnamomum Species: Bridging Phytochemistry Knowledge, Pharmacological Properties and Toxicological Safety for Health Benefits

The genus Cinnamomum includes a number of plant species largely used as food, food additives and spices for a long time. Different traditional healing systems have used these plants as herbal remedies to cure diverse ailments. The aim of this comprehensive and updated review is to summarize the biodiversity of the genus Cinnamomum, its bioactive compounds, the mechanisms that underlie the pharmacological activities and molecular targets and toxicological safety. All the data in this review have been collected from databases and recent scientific literature including Web of Science, PubMed, ScienceDirect etc. The results showed that the bioactive compounds of Cinnamomum species possess antimicrobial, antidiabetic, antioxidant, anti-inflammatory, anticancer and neuroprotective effects. The preclinical (in vitro/in vivo) studies provided the possible molecular mechanisms of these action. As a novelty, recent clinical studies and toxicological data described in this paper support and confirm the pharmacological importance of the genus Cinnamomum. In conclusion, the obtained results from preclinical studies and clinical trials, as well as reduced side effects provide insights into future research of new drugs based on extracts and bioactive compounds from Cinnamomum plants.

Identification of Crocin as a New hIAPP Amyloid Inhibitor via a Simple Yet Highly Biospecific Screening System

Amylin (hIAPP) amyloid formation plays an important role in the pathogenesis of type 2 diabetes (T2D), which makes it a promising therapeutic target for T2D. In this study, we established a screening tool for identifying chemicals affecting hIAPP amyloid formation based on a reported genetic tool, which constantly tracks protein aggregates in Saccharomyces cerevisiae. In order to obtain the hIAPP with better aggregation ability, the gene of hIAPP was tandemly ligated to create 1×, 2×, 4× or 6×-hIAPP expressing strains. By measuring the cell density and fluorescence intensity of green fluorescent protein (GFP) regulated by the aggregation status of hIAPP, it was found that four intramolecular ligated hIAPP (4×hIAPP) could form obvious amyloids with mild toxicity. The validity and reliability of the screening tool were verified by testing six reported hIAPP inhibitors, including curcumin, epigallocatechin gallate and so on. Combined with surface plasmon resonance (SPR) and the screening tool, which could be a screening system for hIAPP inhibitors, we found that crocin specifically binds to hIAPP and acts inhibit amyloid formation of hIAPP. The effect of crocin was further confirmed by Thioflavin T (ThT) fluorescence and transmission electron microscopy (TEM) analysis. Thus, a screening system for hIAPP amyloid inhibitors and a new mechanism of crocin on anti-T2D were obtained as a result of this study.

A Systematic Screening of Traditional Chinese Medicine Identifies Two Novel Inhibitors Against the Cytotoxic Aggregation of Amyloid Beta

The toxic aggregates of amyloid beta (Aβ) disrupt the cell membrane, induce oxidative stress and mitochondrial dysfunction, and eventually lead to Alzheimer’s disease (AD). Intervening with this cytotoxic aggregation process has been suggested as a potential therapeutic approach for AD and other protein misfolding diseases. Traditional Chinese Medicine (TCM) has been used to treat AD and related cognitive impairment for centuries with obvious efficacy. Extracts or active ingredients of TCMs have been reported to inhibit the aggregation and cytotoxicity of Aβ. However, there is a lack of systematic research on the anti-Aβ aggregation effects of TCM components. In this study, we performed a systematic screening to identify the active ingredients of TCM against the cytotoxic aggregation of Aβ42. Through a literature and database survey, we selected 19 TCM herbals frequently used in the treatment of AD, from which 76 major active chemicals without known anti-amyloid effects were further screened. This took place through two rounds of MTT-based screening detection of the cytotoxicity of these chemicals and their effects on Aβ42-induced cytotoxicity, respectively. Tetrahydroxystilbene-2-O-β-D-glucoside (TSG) and sinapic acid (SA) were found to be less toxic, and they inhibited the cytotoxicity of Aβ42. Further studies demonstrated that TSG and SA concentration-dependently attenuated the amyloidosis and membrane disruption ability of Aβ42. Thus, we identified two novel chemicals (TSG and SA) against the cytotoxic aggregation of Aβ42. Nonetheless, further exploration of their therapeutic potential is warranted.

Cinnamtannin D1 Protects Pancreatic β-Cells from Glucolipotoxicity-Induced Apoptosis by Enhancement of Autophagy In Vitro and In Vivo

In our previous study, cinnamtannin D1 (CD-1), one of the A-type procyanidin oligomers isolated from Cinnamomum tamala, was reported to have the activity of antiapoptosis in palmitic acid-treated pancreatic β cells via alleviating oxidative stress in vitro. In this study, the aim was to further disclose its protective effect and underlying mechanisms against glucolipotoxicity-induced β-cells apoptosis in vitro and in vivo. We found that CD-1 was able to dose-dependently and time-dependently activate autophagy in INS-1 pancreatic β-cells. High glucose and palmitic acid (HG/PA)-induced apoptosis and autophagy impairment could be attenuated by CD-1 in INS-1 cells as well as primary cultured murine islets. We also demonstrated that CD-1-induced autophagy was through AMPK/mTOR/ULK1 pathway. Moreover, it was shown that the effects of CD-1 on activation of Keap1/Nrf2 antioxidant signaling pathway and the amelioration of inflammation, endoplasmic reticulum stress, and apoptosis were through autophagy induction in HG/PA-treated INS-1 cells. These protective effects in vivo and hypoglycemic activity of CD-1 were also observed in diabetic db/db mice. These findings have great significance in revealing the antidiabetic mechanisms of procyanidin oligomers and paving the way for their application in the treatment of diabetes.

Chitosan-Based Coatings Incorporated with Cinnamon and Tea Extracts to Extend the Fish Fillets Shelf Life: Validation by FTIR Spectroscopy Technique

The aim of this study was to evaluate the effect of active coatings prepared from the chitosan on the quality parameters of fish fillets. Antimicrobial and antioxidant properties were improved by addition of tea and cinnamon extracts. Different quality parameters including free fatty acids (FFA), thiobarbituric acid value (TBA), trimethylamine (TMA), total volatile basic nitrogen (TVBN), whiteness, and pH of coated and noncoated samples were evaluated during storage for 20 d at 5 ± 1°C. Moreover, FTIR characterization (i.e., wavenumber and absorbance values) was used to investigate the oxidative stability. Extracts addition to chitosan coating had noticeable influence on reducing FFA and TBA. Moreover, modified chitosan coating decreased TVBN and TMA significantly. Based on FTIR finding, control sample showed the highest oxidation value, while the treated samples with chitosan\incorporated with tea and cinnamon extracts (CTCECS) had the lowest oxidation. The results showed that FTIR technique could be successfully applied to monitor the lipid oxidation of fish fillet. Therefore, FTIR provides a fast approach to study the compositional changes of food products rather than conventional chemical analysis. The findings of our research showed that chitosan coating modified with tea and cinnamon extracts could be used as a novel active packaging to prolong the shelf life quality of fish fillet.

Potential of solid lipid microparticles covered by the protein-polysaccharide complex for protection of probiotics and proanthocyanidin-rich cinnamon extract

Probiotics and proanthocyanidin-rich cinnamon extract (PRCE) have numerous potential health benefits, but they are very sensitive to degradation in various environmental conditions. Additionally, the combination of these two materials into a single structure could possibly enhance their therapeutic properties. Thus, the aim of this study was to produce and evaluate the solid lipid microparticles covered by electrostatic interactions of polymers in which Lactobacillus paracasei (BGP1) and Bifidobacterium animalis subsp. lactis (BLC1) were either encapsulated alone or co-encapsulated with PRCE. Through turbidimetric titration and zeta potential measurement, the optimum coacervates were obtained at a pH of 4.2 with the protein:polysaccharide mixing ratio of 6:1. Along with quantification of the probiotics, total phenolic compounds, and proanthocyanidins, morphological and physicochemical characterizations were performed during storage for 120 days at both 7 and 25 °C. All the produced powders had similar morphological and physicochemical properties. The treatments with BLC1 and 5% PRCE presented greater encapsulation efficiencies for probiotic, phenolics, and proanthocyanids with 98.59% ± 0.45, 119.49% ± 4.21, and 81.25% ± 1.9, respectively. Additionally, there was greater viability for BLC1 (9.30 ± 0.16 log CFU / g) after 120 days of storage at 7 °C. In conclusion, solid lipid particles with BLC1 and 5% PRCE are a promising solution for the preservation and consumption of both materials.

Copper and iron ions accelerate the prion-like propagation of α-synuclein: A vicious cycle in Parkinson's disease

Protein fibrils drive the onset and progression of many diseases in a prion-like manner, i.e. they transcellular propagate through the extracellular space to health cells to initiate toxic aggregation as seeds. The conversion of native α-synuclein into filamentous aggregates in Lewy bodies is a hallmark of Parkinson's disease (PD). Copper and iron ions accumulate in PD brains, however, whether they influence the prion-like propagation of α-synuclein remain unclear. Here, we reported that copper/iron ions accelerate prion-like propagation of α-synuclein fibrils by promoting cellular internalization of α-synuclein fibrils, intracellular α-synuclein aggregation and the subsequent release of mature fibrils to the extracellular space to induce further propagation. Mechanistically, copper/iron ions enhanced α-synuclein fibrils internalization was mediated by negatively charged membrane heparan sulfate proteoglycans (HSPGs). α-Synuclein fibrils formed in the presence of copper/iron ions were more cytotoxic, causing increased ROS production, cell apoptosis, and shortened the lifespan of a C. elegans PD model overexpressing human α-synuclein. Notably, these deleterious effects were ameliorated by two clinically used chelators, triethylenetetramine and deferiprone. Together, our results suggest a new role for heavy metal ions, e.g. copper and iron, in the pathogenesis of PD through accelerating prion-like propagation of α-synuclein fibrils.

Non-polyphenolic natural inhibitors of amyloid aggregation

Protein misfolding diseases (PMDs) are chronic and progressive, with no effective therapy so far. Aggregation and misfolding of amyloidogenic proteins are closely associated with the onset and progression of PMDs, such as amyloid-β (Aβ) in Alzheimer's disease, α-Synuclein (α-Syn) in Parkinson's disease and human islet amyloid polypeptide (hIAPP) in type 2 diabetes. Inhibiting toxic aggregation of amyloidogenic proteins is regarded as a promising therapeutic approach in PMDs. The past decade has witnessed the rapid progresses of this field, dozens of inhibitors have been screened and verified in vitro and in vivo, demonstrating inhibitory effects against the aggregation and misfolding of amyloidogenic proteins, together with beneficial effects. Natural products are major sources of small molecule amyloid inhibitors, a number of natural derived compounds have been identified with great bioactivities and translational prospects. Here, we review the non-polyphenolic natural inhibitors that potentially applicable for PMDs treatment, along with their working mechanisms. Future directions are proposed for the development and clinical applications of these inhibitors.

Triterpene Acid and Phenolics from Ancient Apples of Friuli Venezia Giulia as Nutraceutical Ingredients: LC-MS Study and In Vitro Activities

Triterpene acid and phenolic constituents from nine ancient varieties of apple (Malus domestica) fruits cultivated in Fanna, Friuli Venezia Giulia region, northeast Italy, were analyzed and compared with four commercial apples ('Golden Delicious', 'Red Delicious', 'Granny Smith' and 'Royal Gala'). Total phenolic and flavonoid contents were measured by spectrophotometric assays. The quali-quantitative fingerprint of secondary metabolites including triterpene acid was obtained by LC-DAD-(ESI)-MS and LC-(APCI)-MS, respectively. Based on the two LC-MS datasets, multivariate analysis was used to compare the composition of ancient fruit varieties with those of four commercial apples. Significant differences related mainly to the pattern of triterpene acids were found. Pomolic, euscaphyc, maslinic and ursolic acids are the most abundant triterpene in ancient varieties pulps and peels, while ursolic and oleanolic acids were prevalent in the commercial fruits. Also, the content of the phenolic compounds phloretin-2-O-xyloglucoside and quercetin-3-O-arabinoside was greater in ancient apple varieties. The antioxidant (radical scavenging, reducing power, metal chelating and phosphomolybdenum assays) and enzyme inhibitory effects (against cholinesterase, tyrosinase, amylase and glucosidase) of the samples were investigated in vitro. Antioxidant assays showed that the peels were more active than pulps. However, all the samples exhibited similar enzyme inhibitory effects. Ancient Friuli Venezia Giulia apple cultivars can be a source of chlorogenic acid and various triterpene acids, which are known for their potential anti-inflammatory activity and beneficial effects on lipid and glucose metabolism. Our results make these ancient varieties suitable for the development of new nutraceutical ingredients.

Lignan and flavonoid support the prevention of cinnamon against oxidative stress related diseases

BACKGROUND

Oxidative stress contributes to the pathogenesis of many human diseases. Cinnamon is a worldwide used spice, dietary supplement and traditional medicine, and is used for the therapy of oxidative stress related diseases. A well-established concept is that the functions of cinnamon preventing oxidative stress-induced diseases are attributed to the occurrence of cinnamaldehyde and its analogues.

HYPOTHESIS

In our continuous searching of natural molecules with antioxidant capacity, we have found that cinnamaldehyde and its analogues in cinnamon are weak inhibitors of oxidative stress, and thus we speculate that there are novel and/or potent molecules inhibiting oxidative stress in cinnamon.

STUDY DESIGN AND METHODS

A systemic phytochemical investigation of cinnamon using column chromatography was performed to identify the chemical constituents of cinnamon, and then their capacity of inhibiting oxidative stress and action of mechanism targeting Nrf2 pathway were investigated using diverse bioassay, including NAD(P)H: quinone reductase (QR) assay, immunoblot analysis, luciferase reporter gene assay, immunofluorescence and flow cytometry.

RESULTS

Cinnamon improved the intracellular antioxidant capacity. A systemic phytochemical investigation of cinnamon gave the isolation of twenty-two chemical ingredients. The purified constituents were tested for their potential inhibitory effects against oxidative stress. Besides cinnamaldehyde analogues, a lignan pinoresinol (PRO) and a flavonol (-)-(2R,3R)-5,7-dimethoxy-3', 4'-methylenedioxy-flavan-3-ol (MFO) were firstly identified to be inhibitors of oxidative stress. Further study indicated that PRO and MFO activated Nrf2-mediated antioxidant response, and protected human lung epithelial cells against sodium arsenite [As(III)]-induced oxidative insults.

CONCLUSION

The lignan PRO and the flavonoid MFO are two novel Nrf2 activators protecting tissues against oxidative insults, and these two constituents support the application of cinnamon as an agent against oxidative stress related diseases.

Enhancement of Berberine Hypoglycemic Activity by Oligomeric Proanthocyanidins

This study investigated the possible enhancement of berberine’s (BB) hypoglycemic activity by oligomeric proanthocyanidins (OPCs) and its underlying mechanism. The hypoglycemic activity of the studied compounds was evaluated in diabetic db/db mice. The cellular uptake and efflux of BB with or without OPCs were investigated using Caco-2 intestinal cells. A pharmacokinetic study of BB and OPCs was performed in Sprague Dawley (SD) mice by oral administration of the study compounds. Liquid chromatography–tandem mass spectrometry (LC–MS/MS) was employed to determine the cellular efflux, retention, and the serum concentrations of the compounds. The results revealed that OPCs considerably potentiated the hypoglycemic efficacy of BB in diabetic db/db mice. In the in vitro experiments, OPCs significantly inhibited the efflux and increased the uptake of the P-glycoprotein (P-gp) substrate rhodamine-123 (R123) and BB in Caco-2 intestinal cells. Moreover, OPCs substantially reduced the expression of P-gp in Caco-2 cells. The inhibition of BB efflux by OPCs was translated into the improved pharmacokinetics in vivo. When co-administered, OPCs obviously increased the average maximum concentration of BB in mice. In summary, this study demonstrated that combination of BB with OPCs could significantly improve the pharmacokinetics and hypoglycemic efficacy of BB, which is valuable for future exploration of the combination of BB and OPCs as oral hypoglycemic agents.

Modulatory Effect of Polyphenolic Compounds from the Mangrove Tree Rhizophora mangle L. on Non-Alcoholic Fatty Liver Disease and Insulin Resistance in High-Fat Diet Obese Mice

No scientific report proves the action of the phytochemicals from the mangrove tree Rhizophora mangle in the treatment of diabetes. The aim of this work is to evaluate the effects of the acetonic extract of R. mangle barks (AERM) on type 2 diabetes. The main chemical constituents of the extract were analyzed by high-performance liquid chromatography (HPLC) and flow injection analysis electrospray-iontrap mass spectrometry (FIA-ESI-IT-MS/MS). High-fat diet (HFD)-fed mice were used as model of type 2 diabetes associated with obesity. After 4 weeks of AERM 5 or 50 mg/kg/day orally, glucose homeostasis was evaluated by insulin tolerance test (kiTT). Hepatic steatosis, triglycerides and gene expression were also evaluated. AERM consists of catechin, quercetin and chlorogenic acids derivatives. These metabolites have nutritional importance, obese mice treated with AERM (50 mg/kg) presented improvements in insulin resistance resulting in hepatic steatosis reductions associated with a strong inhibition of hepatic mRNA levels of CD36. The beneficial effects of AERM in an obesity model could be associated with its inhibitory α-amylase activity detected in vitro. Rhizophora mangle partially reverses insulin resistance and hepatic steatosis associated with obesity, supporting previous claims in traditional knowledge.

Effects of cinnamic acid on memory deficits and brain oxidative stress in streptozotocin-induced diabetic mice

The present study aimed to evaluate the cinnamic acid effect on memory impairment, oxidative stress, and cholinergic dysfunction in streptozotocin (STZ)-induced diabetic model in mice. In this experimental study, 48 male Naval Medical Research Institute (NMRI) mice (30–35 g) were chosen and were randomly divided into six groups: control, cinnamic acid (20 mg/kg day, i.p. ), diabetic, and cinnamic acid-treated diabetic (10, 20 and 40 mg/kg day, i.p. ). Memory was impaired by administering an intraperitoneal STZ injection of 50 mg/kg. Cinnamic acid was injected for 40 days starting from the 21st day after confirming STZ-induced dementia to observe its therapeutic effect. Memory function was assessed using cross-arm maze, morris water maze and passive avoidance test. After the administration, biochemical parameters of oxidative stress and cholinergic function were estimated in the brain. Present data indicated that inducing STZ caused significant memory impairment, whereas administration of cinnamic acid caused significant and dose-dependent memory improvement. Assessment of brain homogenates indicated cholinergic dysfunction, increase in lipid peroxidation and reactive oxygen species (ROS) levels, and decrease in glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT) activities in the diabetic group compared to the control animals, whereas cinnamic acid administration ameliorated these indices in the diabetic mice. The present study demonstrated that cinnamic acid improves memory by reducing the oxidative stress and cholinergic dysfunction in the brain of diabetic mice.

Interaction between amyloidogenic proteins and biomembranes in protein misfolding diseases: Mechanisms, contributors, and therapy

The toxic deposition of misfolded amyloidogenic proteins is associated with more than fifty protein misfolding diseases (PMDs), including Alzheimer's disease, Parkinson's disease and type 2 diabetes mellitus. Protein deposition is a multi-step process modulated by a variety of factors, in particular by membrane-protein interaction. The interaction results in permeabilization of biomembranes contributing to the cytotoxicity that leads to PMDs. Different biological and physiochemical factors, such as protein sequence, lipid composition, and chaperones, are known to affect the membrane-protein interaction. Here, we provide a comprehensive review of the mechanisms and contributing factors of the interaction between biomembranes and amyloidogenic proteins, and a summary of the therapeutic approaches to PMDs that target this interaction. This article is part of a Special Issue entitled: Protein Aggregation and Misfolding at the Cell Membrane Interface edited by Ayyalusamy Ramamoorthy.

Cinnamon, a promising prospect towards Alzheimer's disease

Over the last decades, an exponential increase of efforts concerning the treatment of Alzheimer's disease (AD) has been practiced. Phytochemicals preparations have a millenary background to combat various pathological conditions. Various cinnamon species and their biologically active ingredients have renewed the interest towards the treatment of patients with mild-to-moderate AD through the inhibition of tau protein aggregation and prevention of the formation and accumulation of amyloid-β peptides into the neurotoxic oligomeric inclusions, both of which are considered to be the AD trademarks. In this review, we presented comprehensive data on the interactions of a number of cinnamon polyphenols (PPs) with oxidative stress and pro-inflammatory signaling pathways in the brain. In addition, we discussed the potential association between AD and diabetes mellitus (DM), vis-à-vis the effluence of cinnamon PPs. Further, an upcoming prospect of AD epigenetic pathophysiological conditions and cinnamon has been sighted. Data was retrieved from the scientific databases such as PubMed database of the National Library of Medicine, Scopus and Google Scholar without any time limitation. The extract of cinnamon efficiently inhibits tau accumulations, Aβ aggregation and toxicity in vivo and in vitro models. Indeed, cinnamon possesses neuroprotective effects interfering multiple oxidative stress and pro-inflammatory pathways. Besides, cinnamon modulates endothelial functions and attenuates the vascular cell adhesion molecules. Cinnamon PPs may induce AD epigenetic modifications. Cinnamon and in particular, cinnamaldehyde seem to be effective and safe approaches for treatment and prevention of AD onset and/or progression. However, further molecular and translational research studies as well as prolonged clinical trials are required to establish the therapeutic safety and efficacy in different cinnamon spp.

Protective Effect of Proanthocyanidins from Sea Buckthorn (Hippophae Rhamnoides L.) Seed against Visible Light-Induced Retinal Degeneration in Vivo

Dietary proanthocyanidins (PACs) as health-protective agents have become an important area of human nutrition research because of their potent bioactivities. We investigated the retinoprotective effects of PACs from sea buckthorn (Hippophae rhamnoides L.) seed against visible light-induced retinal degeneration in vivo. Pigmented rabbits were orally administered sea buckthorn seed PACs (50 and 100 mg/kg/day) for 14 consecutive days of pre-illumination and seven consecutive days of post-illumination. Retinal function was quantified via electroretinography 7 days after light exposure. Retinal damage was evaluated by measuring the thickness of the full-thickness retina and outer nuclear layer 7 days after light exposure. Sea buckthorn seed PACs significantly attenuated the destruction of electroretinograms and maintained the retinal structure. Increased retinal photooxidative damage was expressed by the depletion of glutathione peroxidase and catalase activities, the decrease of total antioxidant capacity level and the increase of malondialdehyde level. Light exposure induced a significant increase of inflammatory cytokines (IL-1β, TNF-α and IL-6) and angiogenesis (VEGF) levels in retina. Light exposure upregulated the expression of pro-apoptotic proteins Bax and caspase-3 and downregulated the expression of anti-apoptotic protein Bcl-2. However, sea buckthorn seed PACs ameliorated these changes induced by light exposure. Sea buckthorn seed PACs mediated the protective effect against light-induced retinal degeneration via antioxidant, anti-inflammatory and antiapoptotic mechanisms.

Potential therapeutic value of TRPV1 and TRPA1 in diabetes mellitus and obesity

Diabetes mellitus and obesity, which is a major risk factor in the development of type 2 diabetes mellitus, have reached epidemic proportions worldwide including the USA. The current statistics and forecasts, both short- and long-term, are alarming and predict severe problems in the near future. Therefore, there is a race for developing new compounds, discovering new receptors, or finding alternative solutions to prevent and/or treat the symptoms and complications related to obesity and diabetes mellitus. It is well demonstrated that members of the transient receptor potential (TRP) superfamily play a crucial role in a variety of biological functions both in health and disease. In the recent years, transient receptor potential vanilloid type 1 (TRPV1) and transient receptor potential ankyrin 1 (TRPA1) were shown to have beneficial effects on whole body metabolism including glucose homeostasis. TRPV1 and TRPA1 have been associated with control of weight, pancreatic function, hormone secretion, thermogenesis, and neuronal function, which suggest a potential therapeutic value of these channels. This review summarizes recent findings regarding TRPV1 and TRPA1 in association with whole body metabolism with emphasis on obese and diabetic conditions.

Isoliquiritigenin and liquiritin from Glycyrrhiza uralensis inhibit α-synuclein amyloid formation

Bioactive isoliquiritigenin and liquiritin inhibit α-synuclein aggregation and extend the life span of theC. elegansmodel of Parkinson's disease.

Inhibition effects of tanshinone on the aggregation of α-synuclein

Bioactive tanshinone compounds inhibit the aggregation of α-synuclein and extend the life span of aC. elegansmodel of Parkinson's disease.

Bisphenol analogues differently affect human islet polypeptide amyloid formation

Bisphenols (BPs) are widely used in the production of plastic material, misfolded human islet amyloid polypeptide (hIAPP) is a causal factor in diabetes. We demonstrated BPs analogues show different effects on hIAPP amyloid formation.

Inhibitory effects of magnolol and honokiol on human calcitonin aggregation

Amyloid formation is associated with multiple amyloidosis diseases. Human calcitonin (hCT) is a typical amyloidogenic peptide, its aggregation is associated with medullary carcinoma of the thyroid (MTC), and also limits its clinical application. Magnolia officinalis is a traditional Chinese herbal medicine; its two major polyphenol components, magnolol (Mag) and honokiol (Hon), have displayed multiple functions. Polyphenols like flavonoids and their derivatives have been extensively studied as amyloid inhibitors. However, the anti-amyloidogenic property of a biphenyl backbone containing polyphenols such as Mag and Hon has not been reported. In this study, these two compounds were tested for their effects on hCT aggregation. We found that Mag and Hon both inhibited the amyloid formation of hCT, whereas Mag showed a stronger inhibitory effect; moreover, they both dose-dependently disassembled preformed hCT aggregates. Further immuno-dot blot and dynamic light scattering studies suggested Mag and Hon suppressed the aggregation of hCT both at the oligomerization and the fibrillation stages, while MTT-based and dye-leakage assays demonstrated that Mag and Hon effectively reduced cytotoxicity caused by hCT aggregates. Furthermore, isothermal titration calorimetry indicated Mag and Hon both interact with hCT. Together, our study suggested a potential anti-amyloidogenic property of these two compounds and their structure related derivatives.

Derivation of Cinnamon Blocks Leukocyte Attachment by Interacting with Sialosides

Molecules derived from cinnamon have demonstrated diverse pharmacological activities against infectious pathogens, diabetes and inflammatory diseases. This study aims to evaluate the effect of the cinnamon-derived molecule IND02 on the adhesion of leukocytes to host cells. The anti-inflammatory ability of IND02, a pentameric procyanidin type A polyphenol polymer isolated from cinnamon alcohol extract, was examined. Pretreatment with IND02 significantly reduced the attachment of THP-1 cells or neutrophils to TNF-α-activated HUVECs or E-selectin/ICAM-1, respectively. IND02 also reduced the binding of E-, L- and P-selectins with sialosides. Furthermore, IND02 could agglutinate human red blood cells (RBC), and the agglutination could be disrupted by sialylated glycoprotein. Our findings demonstrate that IND02, a cinnamon-derived compound, can interact with sialosides and block the binding of selectins and leukocytes with sialic acids.

Identification of proanthocyanidins from litchi (Litchi chinensis Sonn.) pulp by LC-ESI-Q-TOF-MS and their antioxidant activity

Content of total proanthocyanidins as well as total phenolics, flavonoids, antioxidant activities were evaluated for litchi (Litchi chinensis Sonn.) pulp of 32 cultivars. One cultivar, Hemaoli, showed the highest total proanthocyanidins and total phenolics, and DPPH or ABTS radical scavenging activities. ESI-MS and NMR analysis of the Hemaoli pulp crude extracts (HPCE) showed that procyandins composed of (epi)catechin unites with degree of polymerization (DP) of 2–6 were dominant proanthocyanidins in HPCE. After the HPCE was fractionated by a Sephadex LH-20 column, 32 procyanidins were identified by LC-ESI-Q-TOF-MS in litchi pulp for the first time. Quantification of individual procyanidin in HPCE indicated that epicatechin, procyanidin B2, procyanidin C1 and A-type procyanidin trimer were the main procyanidins. The radical scavenging activities of different fractions of HPCE as well as six procyanidins standards were evaluated by both DPPH and ABTS assays. HPCE fractions showed similar antioxidant activities with those of Vc and six individual procyanidins, the IC₅₀ of which ranged from 1.88 ± 0.01 to 2.82 ± 0.10 μg/ml for DPPH assay, and from 1.52 ± 0.17 to 2.71 ± 0.15 μg/ml for ABTS assay. Such results indicate that litchi cultivars rich in proanthocyanidins are good resources of dietary antioxidants and have the potential to contribute to human health.

Cinnamic acid exerts anti-diabetic activity by improving glucose tolerance in vivo and by stimulating insulin secretion in vitro

Although the anti-diabetic activity of cinnamic acid, a pure compound from cinnamon, has been reported but its mechanism(s) is not yet clear. The present study was designed to explore the possible mechanism(s) of anti-diabetic activity of cinnamic acid in in vitro and in vivo non-obese type 2 diabetic rats. Non-obese type 2 diabetes was developed by injecting 90 mg/kg streptozotocin in 2-day-old Wistar pups. Cinnamic acid and cinnamaldehyde were administered orally to diabetic rats for assessing acute blood glucose lowering effect and improvement of glucose tolerance. Additionally, insulin secretory activity of cinnamic acid and cinnamaldehyde was evaluated in isolated mice islets. Cinnamic acid, but not cinnamaldehyde, decreased blood glucose levels in diabetic rats in a time- and dose-dependent manner. Oral administration of cinnamic acid with 5 and 10 mg/kg doses to diabetic rats improved glucose tolerance in a dose-dependent manner. The improvement by 10 mg/kg cinnamic acid was comparable to that of standard drug glibenclamide (5 mg/kg). Further in vitro studies showed that cinnamaldehyde has little or no effect on glucose-stimulated insulin secretion; however, cinnamic acid significantly enhanced glucose-stimulated insulin secretion in isolated islets. In conclusion, it can be said that cinnamic acid exerts anti-diabetic activity by improving glucose tolerance in vivo and stimulating insulin secretion in vitro.

Inhibitory effect of leonurine on the formation of advanced glycation end products

Leonurine inhibits AGE formation through scavenging of the carbonyl species

Cinnamon counteracts the negative effects of a high fat/high fructose diet on behavior, brain insulin signaling and Alzheimer-associated changes

Insulin resistance leads to memory impairment. Cinnamon (CN) improves peripheral insulin resistance but its effects in the brain are not known. Changes in behavior, insulin signaling and Alzheimer-associated mRNA expression in the brain were measured in male Wistar rats fed a high fat/high fructose (HF/HFr) diet to induce insulin resistance, with or without CN, for 12 weeks. There was a decrease in insulin sensitivity associated with the HF/HFr diet that was reversed by CN. The CN fed rats were more active in a Y maze test than rats fed the control and HF/HFr diets. The HF/HFr diet fed rats showed greater anxiety in an elevated plus maze test that was lessened by feeding CN. The HF/HFr diet also led to a down regulation of the mRNA coding for GLUT1 and GLUT3 that was reversed by CN in the hippocampus and cortex. There were increases in Insr, Irs1 and Irs2 mRNA in the hippocampus and cortex due to the HF/HFr diet that were not reversed by CN. Increased peripheral insulin sensitivity was also associated with increased glycogen synthase in both hippocampus and cortex in the control and HF/HFr diet animals fed CN. The HF/HFr diet induced increases in mRNA associated with Alzheimers including PTEN, Tau and amyloid precursor protein (App) were also alleviated by CN. In conclusion, these data suggest that the negative effects of a HF/HFr diet on behavior, brain insulin signaling and Alzheimer-associated changes were alleviated by CN suggesting that neuroprotective effects of CN are associated with improved whole body insulin sensitivity and related changes in the brain.