Baicalein protects against hypertension associated with diabetes: effect on vascular reactivity and stiffness

Study on the potential mechanism of Qingxin Lianzi Yin Decoction on renoprotection in db/db mice via network pharmacology and metabolomics

BACKGROUND

Diabetic nephropathy (DN) was one of the most popular and most significant microvascular complications of diabetes mellitus. Qingxin Lianzi Yin Decoction (QXLZY) was a traditional Chinese classical formula, suitable for chronic urinary system diseases. QXLZY had good clinical efficacy in early DN, but the underlying molecular mechanism remained unrevealed.

PURPOSE

This study aimed to establish the content determination method of QXLZY index components and explore the mechanism of QXLZY on DN by network pharmacology and metabolomics studies.

METHODS

Firstly, the content determination methods of QXLZY were established with calycosin-7-O-β-d-glucoside, acteoside, baicalin and glycyrrhizic acid as index components. Secondly, pharmacological experiments of QXLZY were evaluated using db/db mice. UHPLC-LTQ-Orbitrap MS was used to carry out untargeted urine metabolomics, serum metabolomics, and kidney metabolomics studies. Thirdly, employing network pharmacology, key components and targets were analyzed. Finally, targeted metabolomics studies were performed on the endogenous constituents in biological samples for validation based on untargeted metabolomics results.

RESULTS

A method for the simultaneous determination of multiple index components in QXLZY was established, which passed the comprehensive methodological verification. It was simple, feasible, and scientific. The QXLZY treatment alleviated kidney injury of db/db mice, included the degree of histopathological damage and the level of urinary microalbumin/creatinine ratio. Untargeted metabolomics studies had identified metabolic dysfunction in pathways associated with amino acid metabolism in db/db mice. Treatment with QXLZY could reverse metabolite abnormalities and influence the pathways related to energy metabolism and amino acid metabolism. It had been found that pathways with a high degree were involved in signal transduction, prominently on amino acids metabolism and lipid metabolism, analyzed by network pharmacology. Disorders of amino acid metabolism did occur in db/db mice. QXLZY could revert the levels of metabolites, such as quinolinic acid, arginine, and asparagine.

CONCLUSION

This study was the first time to demonstrate that QXLZY alleviated diabetes-induced pathological changes in the kidneys of db/db mice by correcting disturbances in amino acid metabolism. This work could provide a new experimental basis and theoretical guidance for the rational application of QXLZY on DN, exploring the new pharmacological effect of traditional Chinese medicine, and promoting in-depth research and development.

Natural compounds efficacy in complicated diabetes: A new twist impacting ferroptosis

Ferroptosis, as a way of cell death, participates in the body's normal physiological and pathological regulation. Recent studies have shown that ferroptosis may damage glucose-stimulated islets β Insulin secretion and programmed cell death of T2DM target organs are involved in the pathogenesis of T2DM and its complications. Targeting suppression of ferroptosis with specific inhibitors may provide new therapeutic opportunities for previously untreated T2DM and its target organs. Current studies suggest that natural bioactive compounds, which are abundantly available in drugs, foods, and medicinal plants for the treatment of T2DM and its target organs, have recently received significant attention for their various biological activities and minimal toxicity, and that many natural compounds appear to have a significant role in the regulation of ferroptosis in T2DM and its target organs. Therefore, this review summarized the potential treatment strategies of natural compounds as ferroptosis inhibitors to treat T2DM and its complications, providing potential lead compounds and natural phytochemical molecular nuclei for future drug research and development to intervene in ferroptosis in T2DM.

Combined Effects of Methyldopa and Baicalein or Scutellaria baicalensis Roots Extract on Blood Pressure, Heart Rate, and Expression of Inflammatory and Vascular Disease-Related Factors in Spontaneously Hypertensive Pregnant Rats

The aim of the study was to investigate the effect of baicalein or Scutellaria baicalensis root extract interaction with methyldopa in pregnant spontaneously hypertensive rats (SHR) at the pharmacodynamic, molecular, and biochemical levels. The rats, after confirming pregnancy, received baicalein (200 mg/kg/day, p.o.) and extract (1000 mg/kg/day, p.o.), in combination with methyldopa (400 mg/kg/day; p.o.), for 14 consecutive days, 1 h before blood pressure and heart rate measurements. In the heart and placenta from mothers after giving birth to their offspring, mRNA expression of factors related to inflammatory processes (TNF-α, Il-1β, IL-6) and vascular diseases (TGF-β, HIF-1α, VEGF, PlGF) was measured. Levels of markers of oxidative stress (superoxide dismutase and malondialdehyde) in the placenta and indicators of myocardial damage (troponin cTnC and cTnI, creatine kinase, myoglobin, and lactate dehydrogenase) in the heart were also assessed. Baicalein co-administered with methyldopa was associated with reduced blood pressure, especially during the first three days. The interactions were more pronounced for such factors as TGF-β, HIF-1α, VEGF, and PlGF than TNF-α, Il-1β, and IL-6. Combined application of baicalein and extract with methyldopa may be of value in the development of a new antihypertensive medication intended for patients suffering from preeclampsia or pregnancy-induced hypertension.

Selected Plant-Derived Polyphenols as Potential Therapeutic Agents for Peripheral Artery Disease: Molecular Mechanisms, Efficacy and Safety

Vascular diseases, such as peripheral artery disease (PAD), are associated with diabetes mellitus and a higher risk of cardiovascular disease and even death. Surgical revascularization and pharmacological treatments (mainly antiplatelet, lipid-lowering drugs, and antidiabetic agents) have some effectiveness, but the response and efficacy of therapy are overly dependent on the patient’s conditions. Thus, the demand for new cures exists. In this regard, new studies on natural polyphenols that act on key points involved in the pathogenesis of vascular diseases and, thus, on PAD are of great urgency. The purpose of this review is to take into account the mechanisms that lead to endothelium dysfunction, such as the glycoxidation process and the production of advanced glycation end-products (AGEs) that result in protein misfolding, and to suggest plant-derived polyphenols that could be useful in PAD. Thus, five polyphenols are considered, baicalein, curcumin, mangiferin, quercetin and resveratrol, reviewing the literature in PubMed. The key molecular mechanisms and preclinical and clinical studies of each selected compound are examined. Furthermore, the safety profiles of the polyphenols are outlined, together with the unwanted effects reported in humans, also by searching the WHO database (VigiBase).

Scutellaria baicalensis georgi is a promising candidate for the treatment of autoimmune diseases

Autoimmune diseases a group of disorders elicited by unexpected outcome of lymphocytes self-tolerance failure, and the common members of which include multiple sclerosis, systemic lupus erythematosus, inflammatory bowel disease, rheumatoid arthritis, and type 1 diabetes mellitus, etc. The pathogenesis of autoimmune diseases is not fully understood and the current therapeutic regimen’s inefficacy in certain cases coupled with low rates of success, exorbitant financial burden, as well as numerous side effects, which do open new avenues for the role of natural products as novel therapeutic agents for auto-inflammatory disorders. Scutellaria baicalensis Georgi is a well-known and widely-recognized herbal medicine with certain ameliorative effect on diverse inflammation-involved dysfunction. Though recent advances do highlight its potential to be applied in the fight against autoimmune diseases, the specific mechanism and the related opinion on the exploring possibility are still limited which hampered the further progress. Here in this timeline review, we traced and collected the evidence of how Scutellaria baicalensis Georgi and its bioactive contents, namely baicalin, baicalein, wogonoside and wogonin affect autoimmune diseases. Moreover, we also discussed the clinical implications and therapeutic potential of Scutellaria baicalensis Georgi and its bioactive contents in autoimmune diseases treatment.

Investigating Polyphenol Nanoformulations for Therapeutic Targets against Diabetes Mellitus

Diabetes mellitus (DM) is a fatal metabolic disorder, and its prevalence has escalated in recent decades to a greater extent. Since the incidence and severity of the disease are constantly increasing, plenty of therapeutic approaches are being considered as a promising solution. Many dietary polyphenols have been reported to be effective against diabetes along with its accompanying vascular consequences by targeting multiple therapeutic targets. Additionally, the biocompatibility of these polyphenols raises questions about their use as pharmacological mediators. Nevertheless, the pharmacokinetic and biopharmaceutical properties of these polyphenols limit their clinical benefit as therapeutics. Pharmaceutical industries have attempted to improve compliance and therapeutic effects. However, nanotechnological approaches to overcome the pharmacokinetic and biopharmaceutical barriers associated with polyphenols as antidiabetic medications have been shown to be effective to improve clinical compliance and efficacy. Therefore, this review highlighted a comprehensive and up-to-date assessment of polyphenol nanoformulations in the treatment of diabetes and vascular consequences.

Baicalein Prevents Fructose-Induced Hepatic Steatosis in Rats: In the Regulation of Fatty Acid De Novo Synthesis, Fatty Acid Elongation and Fatty Acid Oxidation

Non-alcoholic fatty liver disease (NAFLD), ranging from simple steatosis to non-alcoholic steatohepatitis (NASH), hepatic fibrosis and even hepatocellular carcinoma, is a liver disease worldwide without approved therapeutic drugs. Baicalein (BAL), a flavonoid compound extracted from the Traditional Chinese Medicine (TCM) Scutellariae Radix (Scutellaria baicalensis Georgi.), has been used in TCM clinical practice for thousands of years to treat liver diseases due to its “hepatoprotective effect”. However, the underlying liver-protecting mechanisms remain largely unknown. Here, we found that oral administration of BAL significantly decreased excess serum levels of triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), aspartate aminotransferase (AST) as well as hepatic TG in fructose-fed rats. Attenuation of the increased vacuolization and Oil Red O staining area was evident on hepatic histological examination in BAL-treated rats. Mechanistically, results of RNA-sequencing, western-blot, real-time quantitative PCR (RT-qPCR) and hepatic metabolomics analyses indicated that BAL decreased fructose-induced excessive nuclear expressions of mature sterol regulatory element-binding protein 1c (mSREBP1c) and carbohydrate response element-binding protein (ChREBP), which led to the decline of lipogenic molecules [including fatty acid synthase (FASN), stearoyl-CoA desaturase 1 (SCD1), elongation of very long chain fatty acids 6 (ELOVL6), acetyl-CoA carboxylase (ACC)], accompanying with the alternation of hepatic fatty acids composition. Meanwhile, BAL enhanced fatty acid oxidation by activating AMPK/PGC1α signaling axis and PPARα signal pathway, which elicited high expression of carnitine palmitoyl transferase 1α (CPT1α) and Acyl-CoA oxidase 1 (ACO1) in livers of fructose-fed rats, respectively. BAL ameliorated fructose-induced hepatic steatosis, which is associated with regulating fatty acid synthesis, elongation and oxidation.

Potential Actions of Baicalein for Preventing Vascular Calcification of Smooth Muscle Cells In Vitro and In Vivo

Vascular calcification (VC) is associated with cardiovascular disease. Baicalein, a natural flavonoid extract of Scutellaria baicalensis rhizome has several biological properties which may inhibit VC. We investigated whether baicalein suppresses Runt-related transcription factor 2 (Runx2) and bone morphogenetic protein 2 (BMP-2) and upregulates smooth muscle 22-alpha (SM22-α) and alpha-smooth muscle actin (α-SMA). In an in vitro experiment, primary rat aortic vascular smooth muscle cells (VSMCs) were pretreated with 0.1, 1, and 5 μM baicalein, followed by β-glycerophosphate (β-GP) to induce calcification. In an in vivo experiment, VC was generated by vitamin D3 plus nicotine (VDN) administration to male Sprague Dawley (SD) rats randomly assigned into a control group, a VC group, a VC group pretreated with baicalein, and a baicalein alone group. Each group comprised 10 rats. Left ventricular (LV) morphology, function and performance were assessed by echocardiography. Calcium content was measured by Alizarin red S staining and alkaline phosphatase (ALP) activity assays. Apoptotic VSMCs were detected by flow cytometry. Protein levels and superoxide changes were evaluated using Western blotting and immunofluorescence assays respectively. Plasma malondialdehyde (MDA) was assayed. Baicalein pretreatment significantly reduced calcium content in calcified VSMCs (p < 0.001) as well as in VC rat aortic smooth muscle (p < 0.001). Additionally, ALP activity was decreased in calcified VSMCs and VC rat aortic smooth muscle (p < 0.001). Apoptosis was significantly attenuated by 1 μM baicalein pretreatment in calcified VSMCs. Runx2 and BMP-2 expressions were downregulated by the baicalein in calcified VSMCs. Baicalein pretreatment increased typical VSMCs markers SM22-α and α-SMA in calcified VSMCs. Baicalein pretreatment was associated with adverse changes in LV morphometry. Markers of oxidative stress declined, and endogenous antioxidants increased in VC rats pretreated with baicalein. Baicalein mitigates VC through the inhibition of Runx2/BMP-2 signaling pathways, enhancement of vascular contractile phenotype and oxidative stress reduction. However, our study is of basic experimental design; more advanced investigations to identify other molecular regulators of VC and their mechanisms of action is required.

Protective effect of the curcumin-baicalein combination against macrovascular changes in diabetic angiopathy

Endothelial dysfunction is an early pathological event in diabetic angiopathy which is the most common complication of diabetes. This study aims to investigate individual and combined actions of Curcumin (Cur) and Baicalein (Bai) in protecting vascular function. The cellular protective effects of Cur, Bai and Cur+Bai (1:1, w/w) were tested in H₂O₂ (2.5 mM) impaired EA. hy926 cells. Wistar rats were treated with vehicle control as the control group, Goto-Kakizaki rats (n=5 each group) were treated with vehicle control (model group), Cur (150 mg/kg), Bai (150 mg/kg), or Cur+Bai (75 mg/kg Cur + 75 mg/kg Bai, OG) for 4 weeks after a four-week high-fat diet to investigate the changes on blood vessel against diabetic angiopathy. Our results showed that Cur+Bai synergistically restored the endothelial cell survival and exhibited greater effects on lowering the fasting blood glucose and blood lipids in rats comparing to individual compounds. Cur+Bai repaired the blood vessel structure in the aortic arch and mid thoracic aorta. The network pharmacology analysis showed that Nrf2 and MAPK/JNK kinase were highly relevant to the multi-targeted action of Cur+Bai which has been confirmed in the in vitro and in vivo studies. In conclusion, Cur+Bai demonstrated an enhanced activity in attenuating endothelial dysfunction against oxidative damage and effectively protected vascular function in diabetic angiopathy rats.

Combination of Captopril with Gliclazide Decreases Vascular and Renal Complications and Improves Glycemic Control in Rats with Streptozotocin- Induced Diabetes Mellitus

BACKGROUND

The common antihypertensive angiotensin-converting enzyme (ACE) inhibitor captopril was reported to possess anti-oxidant and anti-inflammatory effects in different experimental models. Diabetic vascular complications arise from increased vascular endothelial inflammation and oxidative stress as well as decreased nitric oxide bioavailability in the vessel walls due to poor glycemic control.

OBJECTIVE

This study aimed to evaluate the role of captopril and gliclazide in decreasing diabetes mellitus (DM) vascular complications caused by decreased cellular glucose uptake and impaired endothelial nitric oxide metabolism, as well as examine the effects of the combination on diabetic renal complication and plasma lipid profile.

METHODS

Adult male Wister rats received captopril (25 mg/kg/day) and/or gliclazide (10 mg/kg/- day) by oral gavage daily for one month after induction of DM using streptozotocin (50 mg/kg, i.p., once). Serum glucose and insulin levels, inflammatory mediators like TNF-α, oxidative stress biomarkers like glutathione and nitric oxide, and plasma lipid profile were measured. Besides, histopathological examination of the thoracic aorta and kidney tissues, Western blot assessed the expression of nitric oxide synthase (NOS) subtypes in the thoracic aorta.

RESULTS

Captopril significantly improved vascular architecture and oxidative stress and modulated nitric oxide synthesis via regulation of nitric oxide synthases, as well as decreased inflammation via down-regulating TNF-α, decreased systolic and diastolic blood pressure, and improved serum lipid profile in diabetic rats. Gliclazide increased serum insulin and decreased serum glucose, as well as its anti-oxidant and anti-inflammatory effects.

CONCLUSION

Captopril showed a promising protective effect against DM vascular complications, at least via nitric oxide modulating effect, anti-oxidant effect, and anti-inflammatory activity that appeared in biochemical and histopathological findings, lipid profile, renal function, and architecture improvements. Combining gliclazide with captopril gives an additive effect through enhanced glycemic control and increased anti-oxidant and anti-inflammatory properties above captopril alone.

Dietary 5,6,7-Trihydroxy-flavonoid Aglycones and 1-Deoxynojirimycin Synergistically Inhibit the Recombinant Maltase-Glucoamylase Subunit of α-Glucosidase and Lower Postprandial Blood Glucose

1-Deoxynojirimycin (1-DNJ) is the major effective component of mulberry leaves, exhibiting inhibitory activity against α-glucosidase. However, due to the low content of 1-DNJ in mulberry products, its level cannot meet the lowest dose to exhibit its activity. In this study, a combination of dietary 5,6,7-trihydroxy-flavonoid aglycones with 1-DNJ showed synergistic inhibitory activity against maltase of mice α-glucosidase and recombinant C- and N-termini of maltase-glucoamylase (MGAM) and baicalein with 1-DNJ exhibited the strongest synergistic effect. The synergistic effect of the combination was also confirmed by the maltose tolerance test in vivo. Enzyme kinetics, molecular docking, fluorescence spectrum, and circular dichroism spectrometry studies indicated that the major mechanism of the synergism is that baicalein was a positive allosteric inhibitor and bound to the noncompetitive site of MGAM, causing an increase of the binding affinity of 1-DNJ to MGAM. Our results might provide a theoretical basis for the design of dietary supplements containing mulberry products.

Baicalein Alleviates Liver Oxidative Stress and Apoptosis Induced by High-Level Glucose through the Activation of the PERK/Nrf2 Signaling Pathway

Baicalein, a widely-distributed natural flavonoid, exhibits antioxidative activity in mice with type-2 diabetes. However, the underlying mechanisms remain partially elucidated. In this study, we investigated the effect of baicalein on protein kinase R-like ER kinase (PERK)/nuclear factor erythroid-2-related factor 2 (Nrf2) pathway for the alleviation of oxidative stress and apoptosis. Human liver HL-7702 cells were stimulated with 60.5 mM of glucose to induce oxidative stress and treated with baicalein. The apoptosis was determined by fluorescence microscopy and flow cytometry. The regulation of the PERK/Nrf2 pathway by baicalein was determined by immunoblotting in both HL-7702 cells and liver tissues from diabetic mice. We found that baicalein significantly alleviated the oxidative stress and apoptosis in HL-7702 cells stimulated with glucose. Mechanistic studies showed that baicalein downregulated PERK and upregulated Nrf2, two key proteins involved in endoplasmic reticulum stress, in both HL-7702 cells and liver tissues from diabetic mice receiving baicalein treatment. Furthermore, the subcellular localization of Nrf2 and the regulation of downstream proteins including heme oxygenase-1 and CCAAT-enhancer-binding protein homologous protein (CHOP) by baicalein were also investigated. Our results suggest that the regulation of the PERK/Nrf2 pathway is one of the mechanisms contributing to the bioactivities of baicalein to improve diabetes-associated complications.

Baicalin and its aglycone: a novel approach for treatment of metabolic disorders

BACKGROUND

The current strategies for prevention and treatment of insulin resistance and type 2 diabetes are not fully effective and frequently accompanied by many negative effects. Therefore, novel ways to prevent insulin resistance and type 2 diabetes are urgently needed. The roots of Scutellaria radix are commonly used in traditional Chinese medicines for prevention and treatment of type 2 diabetes, atherosclerosis, hypertension, hyperlipidemia, dysentery, and other respiratory disorders. Baicalin and baicalein are the major and active ingredient extracts from Scutellaria baicalensis.

METHODS

A comprehensive and systematic review of literature on baicalin and baicalein was carried out.

RESULTS

Emerging evidence indicated that baicalin and baicalein possessed hepatoprotective, anti-oxidative, anti-dyslipidemic, anti-lipogenic, anti-obese, anti-inflammatory, and anti-diabetic effects, being effective for treating obesity, insulin resistance, non-alcoholic fatty liver, and dyslipidemia. Besides, baicalin and baicalein are almost non-toxic to epithelial, peripheral, and myeloid cells.

CONCLUSION

The purpose of this study is to focus on the therapeutic applications and accompanying molecular mechanisms of baicalin and baicalein against hyperglycemia, insulin resistance, type 2 diabetes, hyperlipidemia, obesity, and non-alcoholic fatty liver, and trying to establish a novel anti-obese and anti-diabetic strategy.

Flavonoids and type 2 diabetes: Evidence of efficacy in clinical and animal studies and delivery strategies to enhance their therapeutic efficacy

Diabetes mellitus type 2 (T2DM) is a metabolic disorder develops due to the overproduction of free radicals where oxidative stress could contribute it. Possible factors are defective insulin signals, glucose oxidation, and degradation of glycated proteins as well as alteration in glutathione metabolism which induced hyperglycemia. Previous studies revealed a link between T2DM with oxidative stress, inflammation and insulin resistance which are assumed to be regulated by numerous cellular networks such as NF-κB, PI3K/Akt, MAPK, GSK3 and PPARγ. Flavonoids are ubiquitously present in the nature and classified according to their chemical structures for example, flavonols, flavones, flavan-3-ols, anthocyanidins, flavanones, and isoflavones. Flavonoids indicate poor bioavailability which could be improved by employing various nano-delivery systems against the occurrences of T2DM. These bioactive compounds exert versatile anti-diabetic activities via modulating targeted cellular signaling networks, thereby, improving glucose metabolism, α -glycosidase, and glucose transport or aldose reductase by carbohydrate metabolic pathway in pancreatic β-cells, hepatocytes, adipocytes and skeletal myofibres. Moreover, anti-diabetic properties of flavonoids also encounter diabetic related complications. This review article has designed to shed light on the anti-diabetic potential of flavonoids, contribution of oxidative stress, evidence of efficacy in clinical, cellular and animal studies and nano-delivery approaches to enhance their therapeutic efficacy. This article might give some new insights for therapeutic intervention against T2DM in near future.

Flavonoids and Their Anti-Diabetic Effects: Cellular Mechanisms and Effects to Improve Blood Sugar Levels

Diabetes mellitus (DM) is a prevailing global health metabolic disorder, with an alarming incidence rate and a huge burden on health care providers. DM is characterized by the elevation of blood glucose due either to a defect in insulin synthesis, secretion, binding to receptor, or an increase of insulin resistance. The internal and external factors such as obesity, urbanizations, and genetic mutations could increase the risk of developing DM. Flavonoids are phenolic compounds existing as secondary metabolites in fruits and vegetables as well as fungi. Their structure consists of 15 carbon skeletons and two aromatic rings (A and B) connected by three carbon chains. Flavonoids are furtherly classified into 6 subclasses: flavonols, flavones, flavanones, isoflavones, flavanols, and anthocyanidins. Naturally occurring flavonoids possess anti-diabetic effects. As in vitro and animal model’s studies demonstrate, they have the ability to prevent diabetes and its complications. The aim of this review is to summarize the current knowledge addressing the antidiabetic effects of dietary flavonoids and their underlying molecular mechanisms on selected pathways: Glucose transporter, hepatic enzymes, tyrosine kinase inhibitor, AMPK, PPAR, and NF-κB. Flavonoids improve the pathogenesis of diabetes and its complications through the regulation of glucose metabolism, hepatic enzymes activities, and a lipid profile. Most studies illustrate a positive role of specific dietary flavonoids on diabetes, but the mechanisms of action and the side effects need more clarification. Overall, more research is needed to provide a better understanding of the mechanisms of diabetes treatment using flavonoids.

Antidiabetic Potential of Flavonoids from Traditional Chinese Medicine: A Review

Diabetes mellitus (DM) is a group of metabolic disorders in which high blood sugar levels occur over a prolonged period. Approximately 4% of the global population is affected by DM. Western medical treatment methods for diabetes including injection or oral hypoglycemic drugs have some toxic or side effects, economic pressures, and so on. Many researchers turn to discover new drugs from natural products or Traditional Chinese Medicine (TCM). Flavonoids are widely distributed in plants, and many studies have shown that flavonoids possess antidiabetic properties, exhibiting not only well-recognized antidiabetic and hypoglycemic activities but also activity in the treatment of diabetic complications. In this review, we systematically summarized anti-diabetic flavonoid compounds based on structure classification by examining the PubMed, Springer Link, Web of Science, and CNKI databases. There are 13 flavonoid compounds listed which have been studied extensively and have antidiabetic features respectively. Apigenin, baicalein, and catechin mainly reduces blood glucose via anti-oxidation; hesperidin is good for diabetic neuropathy; glycyrrhiza flavonoids have a significant effect on gestational DM; quercetin takes advantage of crossing the blood–brain barrier and improving renal function. Some compounds have protective and preventive effects on diabetic complications, such as kaempferol and puerarin which are beneficial to cardiomyopathy; myricetin has therapeutic potential in the treatment of DN; dihydromyricetin might improve CI. It is a pity or might be a pointcut that most studies remain in the animal experimental stage, and further investigation should be carried out.

In vitro and in vivo activities of flavonoids – apigenin, baicalin, chrysin, scutellarin – in regulation of hypertension – a review for their possible effects in pregnancy-induced hypertension

Flavonoids and their conjugates are the most important group of natural chemical compounds in drug discovery and development. The search for pharmacological activity and new mechanisms of activity of these chemical compounds, which may inhibit mediators of inflammation and influence the structure and function of endothelial cells, can be an interesting pharmacological strategy for the prevention and adjunctive treatments of hypertension, especially induced by pregnancy. Because cardiovascular diseases have multi-factorial pathogenesis these natural chemical compounds with wide spectrum of biological activities are the most interesting source of new drugs. Extracts from one of the most popular plant used in Traditional Chinese Medicine, Scutellaria baicalensis Georgi could be a very interesting source of flavonoids because of its exact content in quercetin, apigenin, chrysin and scutellarin as well as in baicalin. These flavonoids exert vasoprotective properties and many activities such as: anti-oxidative via several pathways, anti-in-flammatory, anti-ischaemic, cardioprotective and anti-hypertensive. However, there is lack of summaries of results of studies in context of potential and future application of flavonoids with determined composition and activity. Our review aims to provide a literature survey of in vitro, in vivo and ex vivo pharmacological studies of selected flavonoids (apigenin, chrysin and scutellarin, baicalin) in various models of hypertension carried out in 2008–2018.

Baicalein improves glucose metabolism in insulin resistant HepG2 cells

Insulin resistance (IR) is the primary pathogenesis of Type 2 diabetes mellitus (T2DM). Scutellaria baicalensis Georgi is a traditional Chinese herbal medicine, often used in the clinical treatment of T2DM. Baicalein which is considered to have anti-IR effects is one of its active ingredients. IR-induced HepG2 cells were used to investigate the effect of baicalein on glucose metabolism and insulin-signaling pathway, using metformin as a positive control. We found that the use of both baicalein and metformin increased the glucose consumption of IR cells, as well as increasing the pyruvate kinase (PK) and glucokinase (GCK) activity. Also increased was the expression levels of insulin receptor (InsR), insulin receptor substrate-1 (IRS-1), phosphoinositide 3-kinase (PI3K), protein kinase B (AKT) pathway and glucose transporter 2 (GLUT2). Reduced expression levels were found in that of glucose 6 phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK) mRNA. The results confirmed that baicalein (10^-6 and 10^-5 mol/L) promotes glucose uptake and glycolysis, inhibits gluconeogenesis of hepatocytes to improve glucose metabolism, and may be as a result from regulation of InsR/IRS-1/PI3K/AKT pathway. Additionally, baicalein has large concentration range on inhibiting IR, and at lower concentrations has strong anti-IR hepatocyte activity.

Dietary Polyphenols Targeting Arterial Stiffness: Interplay of Contributing Mechanisms and Gut Microbiome-Related Metabolism

Increased arterial stiffness is a degenerative vascular process, progressing with age that leads to a reduced capability of arteries to expand and contract in response to pressure changes. This progressive degeneration mainly affects the extracellular matrix of elastic arteries and causes loss of vascular elasticity. Recent studies point to significant interference of dietary polyphenols with mechanisms involved in the pathophysiology and progression of arterial stiffness. This review summarizes data from epidemiological and interventional studies on the effect of polyphenols on vascular stiffness as an illustration of current research and addresses possible etiological factors targeted by polyphenols, including pathways of vascular functionality, oxidative status, inflammation, glycation, and autophagy. Effects can either be inflicted directly by the dietary polyphenols or indirectly by metabolites originated from the host or microbial metabolic processes. The composition of the gut microbiome, therefore, determines the resulting metabolome and, as a consequence, the observed activity. On the other hand, polyphenols also influence the intestinal microbial composition, and therefore the metabolites available for interaction with relevant targets. As such, targeting the gut microbiome is another potential treatment option for arterial stiffness.

Baicalein attenuates monocrotaline-induced pulmonary arterial hypertension by inhibiting endothelial-to-mesenchymal transition

AIMS

Endothelial-to-mesenchymal transition (EndoMT) was shown to lead to endothelial cell (EC) dysfunction in pulmonary arterial hypertension (PAH). Baicalein was reported to inhibit epithelial-to-mesenchymal transition (EMT), a biological process that has many regulatory pathways in common with EndoMT. Whether it can attenuate PAH by inhibiting EndoMT remains obscure.

MAIN METHODS

PAH was induced by a single subcutaneous injection of MCT (60 mg/kg) in male Sprague Dawley rats. Two weeks after MCT administration, the rats in the treatment groups received baicalein orally (50 or 100 mg/kg/day) for an additional 2 weeks. Hemodynamic changes and right ventricular hypertrophy (RVH) were evaluated on day 28. Cardiopulmonary interstitial fibrosis was detected using Masson's trichrome, Picrosirius-red, and immunohistochemical staining. The reactivity of pulmonary arteries (PAs) was examined ex vivo. The protein expresson of EndoMT molecules, bone morphogenetic protein receptor 2 (BMPR2), and nuclear factor-κB (NF-κB) was examined to explore the mechanism of protective action of baicalein.

KEY FINDINGS

Baicalein (50 and 100 mg/kg) significantly alleviated MCT-induced PAH and cardiopulmonary interstitial fibrosis. Furthermore, baicalein treatment enhanced PA responsiveness to acetylcholine (ACh) in PAH rats. The upregulation of EndoMT molecules (N-cadherin, vimentin, Snail, and Slug) strongly suggest that EndoMT participates in MCT-induced PAH, which was reversed by baicalein (50 and 100 mg/kg) treatment. Moreover, baicalein partially reversed MCT-induced reductions in BMPR2 and NF-κB activation in the PAs.

SIGNIFICANCE

Baicalein attenuated MCT-induced PAH in rats by inhibiting EndoMT partially via the NF-κB-BMPR2 pathway. Thus, baicalein might be considered as a promising treatment option for PAH.

Arginase overexpression and NADPH oxidase stimulation underlie impaired vasodilation induced by advanced glycation end products

BACKGROUND

Advanced glycation endproducts (AGEs) play a major role in the development of many vascular complications that are mediated by endothelial dysfunction. The present work aimed to investigate the mechanism by which AGEs impair vasodilation.

METHODS

The effect of AGEs on vasodilation induced by acetylcholine or D NONOate was examined by incubating isolated rat aortae with different AGEs concentrations. ACh-induced nitric oxide generation was assessed using the fluorescent probe diaminofluorecein (DAF-FM). The effect of AGEs on expression of mRNA for arginase 2, NADPH oxidase and endothelial nitric oxide synthase (eNOS) were determined by real-time PCR.

RESULTS

One-hour in vitro incubation of rat aortae with AGEs impaired endothelial-dependent vasodilation produced by ACh, while increasing D NONOate-induced vasodilation. Preincubation of aortae with l-ornithine, an arginase 2-inhibitor, prevented the impairment effect induced by AGEs on endothelial-dependent vasodilation. Superoxide scavenging by tempol or NADPH oxidase inhibition by apocynin also blocked the effect of AGEs. AGEs decreased ACh-induced NO production and this was inhibited by both l-ornithine and apocynin. Furthermore, AGEs exposure increased arginase mRNA expression but decreased mRNA expression for eNOS in isolated rat aortae.

CONCLUSION

The present results indicate that AGEs impairs endothelial-dependent vasodilation, and this effect is mediated via arginase overexpression and NADPH oxidase stimulation.

Limonin alleviates macro- and micro-vascular complications of metabolic syndrome in rats: A comparative study with azelnidipine

BACKGROUND

Hypertension is a serious component of metabolic syndrome (MetS).

HYPOTHESIS

This research investigates the potential protective effect of limonin against MetS-associated hypertension in comparison with azelnidipine, a common calcium channel blocker.

STUDY DESIGN

MetS was induced in rats by 10% fructose in water and 3% salt in diet over a 16-week period. Limonin (50 mg/kg) and azelnidipine (5 mg/kg) were administered daily in the last four weeks METHODS: Non-invasive blood pressure (BP) was recorded in conscious animals. Concentration-response curves for phenylephrine (PE) and acetylcholine (ACh) were analysed in thoracic aorta (macrovessels) and kidney microvessels. Blood glucose level, serum insulin level, advanced glycation end products (AGEs), tumor necrosis factor-α (TNF-α), malondialdehyde (MDA) and transforming growth factor-β1 (TGF-β1) were determined.

RESULTS

Limonin alleviated elevations in systolic and diastolic BP associated with MetS similar to levels associated with azelnidipine. Limonin prevented the MetS induced exaggerated macro- and micro-vascular contractility to PE and the impaired dilatation to ACh. However, in vitro incubation with limonin partially alleviated the deteriorated vascular reactivity of aorta isolated from MetS animals or AGEs injured aorta. Limonin did not have direct relaxant effect on the isolated vessel. On the other hand, limonin reduced the elevated serum levels of AGEs, TNF-α and MDA. Limonin suppressed the vascular fibrosis through reducing the elevated serum level of TGF-β1 and excessive aortic collagen deposition. Limonin decreased the elevated HOMA-IR in MetS animals.

CONCLUSION

Limonin offsets the hypertensive and vascular impairment associated with MetS via attenuation of inflammation and fibrosis. Its impact is comparable to that of azelnidipine.

Dietary Flavonoids and Acarbose Synergistically Inhibit α-Glucosidase and Lower Postprandial Blood Glucose

The inhibition of porcine pancreatic α-amylase and mammalian α-glucosidase by 16 individual flavonoids was determined. The IC₅₀ values for baicalein, (+)-catechin, quercetin, and luteolin were 74.1 ± 5.6, 175.1 ± 9.1, 281.2 ± 19.2, and 339.4 ± 16.3 μM, respectively, against α-glucosidase. The IC₅₀ values for apigenin and baicalein were 146.8 ± 7.1 and 446.4 ± 23.9 μM, respectively, against α-amylase. The combination of baicalein, quercetin, or luteolin with acarbose showed synergistic inhibition, and the combination of (+)-catechin with acarbose showed antagonistic inhibition of α-glucosidase. The combination of baicalein or apigenin with acarbose showed additive inhibition of α-amylase at lower concentrations and antagonistic inhibition at a higher concentration. Kinetic studies of α-glucosidase activity revealed that baicalein alone, acarbose alone, and the combination showed noncompetitive, competitive, and mixed-type inhibition, respectively. Molecular modeling revealed that baicalein had higher affinity to the noncompetitive binding site of maltase, glucoamylase, and isomaltase subunits of α-glucosidase, with glide scores of -7.64, -6.98, and -6.88, respectively. (+)-Catechin had higher affinity to the active sites of maltase and glucoamylase and to the noncompetitive site of isomaltase. After sucrose loading, baicalein dose-dependently reduced the postprandial blood glucose (PBG) level in mice. The combination of 80 mg/kg baicalein and 1 mg/kg acarbose synergistically lowered the level of PBG, and the hypoglycemic effect was comparable to 8 mg/kg acarbose. The results indicated that baicalein could be used as a supplemental drug or dietary supplement in dietary therapy for diabetes mellitus.

Baicalein Promotes Neuronal and Behavioral Recovery After Intracerebral Hemorrhage Via Suppressing Apoptosis, Oxidative Stress and Neuroinflammation

Intracerebral hemorrhage (ICH) is an important public health problem in neurology, which is not only associated with high mortality but also leading to disability. Yet no satisfactory treatment has been developed. The secondary injury that resulted from a number of self-destructive processes such as neuroinflammation, apoptosis and oxidative stress, is the key factor contributing to ICH-induced brain damage. Baicalein has been proved to improve neuronal functional recovery in rat model of subarachnoid hemorrhage and ischemic brain damage. To investigate the effect of baicalein on ICH and its underlying mechanism, a collagenase-induced ICH rat model was performed. Baicalein treatment significantly decreased neurological severity score at day 1 and 3 after ICH injury. Our results showed that the lesion volume, the brain water content, the expression levels of four pro-inflammatory cytokines (IL-1β, IL-4 and IL-6 and TNF-α) and the numbers of apoptotic cells were reduced significantly in ICH rats receiving baicalein treatment, especially in 50 mg/kg baicalein-treated group. Moreover, baicalein increased SOD and GSH-Px activities and down-regulated MDA level of brain tissues in rats. These results suggested that the therapeutic efficacy of baicalein on repairing brain damage is probably caused by suppressing apoptosis, oxidative stress and neuroinflammation. Baicalein could be developed into a novel drug for clinical treatment of ICH and ICH-related brain injuries.

Metabolomics insights into diabetes nephropathy and protective effects of Radix Scutellariae on rats using ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry

UHPLC-Q-TOF-MS based metabolomics combined with multivariate statistical analysis for evaluating protective effects ofRadix Scutellariaeon DN rats.

Phenolics from Garcinia mangostana alleviate exaggerated vasoconstriction in metabolic syndrome through direct vasodilatation and nitric oxide generation

BACKGROUND

Exaggerated vasoconstriction plays a very important role in the hypertension, a major component of metabolic syndrome (MetS). In the current work, the potential protective effect of methanol extract of fruit hulls of Garcinia mangostana L. on the exaggerated vasoconstriction in MetS has been investigated. In addition, the bioactive fraction and compounds as well as the possible mechanism of action have been illustrated.

METHODS

The effect of methanol extract of G. mangostana (GMT) fruit hulls on the vascular reactivity of aorta isolated from animals with MetS was investigated through bioassay-guided fractionation procedures. GMT was partitioned with chloroform (I) and the remaining mother liquor was fractionated on a Diaion HP-20 with H2O, 50 and 100 % methanol to give fractions II, III, and IV, respectively. The effect of total extract (GMT), bioactive fraction and the bioactive compounds on the vasoconstriction were examined in aortae isolated from animals with MetS by incubation for 30 min before exposing aortae to cumulative concentrations of phenylephrine (PE). The direct relaxant effect was also examined by adding cumulative concentrations of the bioactive fraction and its bioactive compounds to PE precontracted vessels. In addition, aortic nitric oxide (NO) and reactive oxygen species (ROS) production was investigated.

RESULTS

Bioassay-guided fractionation of GMT revealed isolation of garcimangosone D (1), aromadendrin-8-C-β-D-glucopyranoside (2), 2,4,3'-trihydroxy benzophenone-6-O-β-D-glucopyranoside (3), maclurin-6-O-β-D-glucopyranoside (rhodanthenone) (4), epicatechin (5), and 2,3',4,5',6-pentahydroxy benzophenone (6). Only compounds 2, 4, and 5 significantly alleviated the exaggerated vasoconstriction of MetS aortae and in the same time showed significant vasodilation of PE pre-contracted aortae. To further illustrate the mechanism of action, the observed vasodilation was completely blocked by the nitric oxide (NO) synthase inhibitor, Nω-nitro-L-arginine methyl ester hydrochloride and inhibited by guanylate cyclase inhibitor, methylene blue. However, vasodilation was not affected by the potassium channel blocker, tetraethylammonium or the cyclooxygenase inhibitor, indomethacin. In addition, compounds 2, 4, and 5 stimulated NO generation from isolated aortae to levels comparable with acetylcholine. Furthermore, 4 and 5 inhibited reactive oxygen species generation in MetS aortae.

CONCLUSION

The phenolic compounds 2, 4, and 5 ameliorated the exaggerated vasoconstriction in MetS aortae through vasodilatation-NO generation mechanism.

The Possible Role of Flavonoids in the Prevention of Diabetic Complications

Type 2 diabetes mellitus is a disease that affects many metabolic pathways. It is associated with insulin resistance, impaired insulin signaling, β-cell dysfunction, abnormal glucose levels, altered lipid metabolism, sub-clinical inflammation and increased oxidative stress. These and other unknown mechanisms lead to micro- and macro-complications, such as neuropathy, retinopathy, nephropathy and cardiovascular disease. Based on several in vitro animal models and some human studies, flavonoids appear to play a role in many of the metabolic processes involved in type 2 diabetes mellitus. In this review, we seek to highlight the most recent papers focusing on the relationship between flavonoids and main diabetic complications.

Polyphenol protection and treatment of hypertension

INTRODUCTION

High blood pressure is the major risk factor for cardiovascular diseases and the rising prevalence of human hypertension precedes the trend toward a global epidemic of unhealthy ageing. A focus on lifestyle and dietary interventions minimizes dependency on pharmacological antihypertensive therapies.

REVIEW

Observational studies indicate that the intake of dietary flavonoids is associated with a decreased risk of cardiovascular disease (CVD). The evidence suggests that the dietary intakes of polyphenol-rich foods, herbs and beverages including flavonols, anthocyanidins, proanthocyanidins, flavones, flavanones, isoflavones and flavan-3-ols, improves vascular health, thereby significantly reducing the risk of hypertension and CVD. Consumption is associated with an improvement in endothelial function via vascular eNOS and Akt activation. Increased NO bioavailability improves vasodilation and blood circulation, effects protein kinases, ion channels and phosphodiesterases, counteracting vascular inflammation and LDL oxidative stress. Importantly, some polyphenols also inhibit the activity of matrix metalloproteinases, inhibit angiotensin converting enzyme activity and thereby improving SBP and DSB. We review the improvement of polyphenol intake on blood pressure and endothelial function for the treatment of hypertension, including not only observational but also RCTs and pre-clinical studies.

CONCLUSION

The antihypertensive phytotherapy of polyphenol-rich foods for protection and improving endothelial function with vascular relaxation occurs via the NO-cGMP pathway and ACE inhibition. OPCs stimulate endothelium-dependent vasodilation, suppress vasoconstrictor ET-1 synthesis, activate a laminar shear stress response in endothelial cells and also inhibit the activity of metalloproteinases including ACE lowering blood pressure.

Antidiabetic properties of dietary flavonoids: a cellular mechanism review

Background

Natural food products have been used for combating human diseases for thousands of years. Naturally occurring flavonoids including flavones, flavonols, flavanones, flavonols, isoflavones and anthocyanidins have been proposed as effective supplements for management and prevention of diabetes and its long-term complications based on in vitro and animal models.

Aim

To summarize the roles of dietary flavonoids in diabetes management and their molecular mechanisms.

Findings

Tremendous studies have found that flavonoids originated from foods could improve glucose metabolism, lipid profile, regulating the hormones and enzymes in human body, further protecting human being from diseases like obesity, diabetes and their complications.

Conclusion

In the current review, we summarize recent progress in understanding the biological action, mechanism and therapeutic potential of the dietary flavonoids and its subsequent clinical outcomes in the field of drug discovery in management of diabetes mellitus.