Protective effects of marein on high glucose-induced glucose metabolic disorder in HepG2 cells

Marein Alleviates Doxorubicin-Induced Cardiotoxicity through FAK/AKT Pathway Modulation while Potentiating its Anticancer Activity

Doxorubicin (DOX) is an effective anticancer agent, yet its clinical utility is hampered by dose-dependent cardiotoxicity. This study explores the cardioprotective potential of Marein (Mar) against DOX-induced cardiac injury and elucidates underlying molecular mechanisms. Neonatal rat cardiomyocytes (NRCMs) and murine models were employed to assess the impact of Mar on DOX-induced cardiotoxicity (DIC). In vitro, cell viability, oxidative stress were evaluated. In vivo, a chronic injection method was employed to induce a DIC mouse model, followed by eight weeks of Mar treatment. Cardiac function, histopathology, and markers of cardiotoxicity were assessed. In vitro, Mar treatment demonstrated significant cardioprotective effects in vivo, as evidenced by improved cardiac function and reduced indicators of cardiac damage. Mechanistically, Mar reduced inflammation, oxidative stress, and apoptosis in cardiomyocytes, potentially via activation of the Focal Adhesion Kinase (FAK)/AKT pathway. Mar also exhibited an anti-ferroptosis effect. Interestingly, Mar did not compromise DOX's efficacy in cancer cells, suggesting a dual benefit in onco-cardiology. Molecular docking studies suggested a potential interaction between Mar and FAK. This study demonstrates Mar's potential as a mitigator of DOX-induced cardiotoxicity, offering a translational perspective on its clinical application. By activating the FAK/AKT pathway, Mar exerts protective effects against DOX-induced cardiomyocyte damage, highlighting its promise in onco-cardiology. Further research is warranted to validate these findings and advance Mar as a potential adjunctive therapy in cancer treatment.

Marein, a novel natural product for restoring chemo-sensitivity to cancer cells through competitive inhibition of ABCG2 function

The pivotal roles of ATP-binding cassette (ABC) transporters in drug resistance have been widely appreciated. Here we report that marein, a natural product from Coreopsis tinctoria Nutt, is a potent chemo-sensitizer in drug resistant cancer cells overexpressing ABCG2 transporter. We demonstrate that marein can competitively inhibit efflux activity of ABCG2 protein and increase the intracellular accumulation of the chemotherapeutic drugs that belong to substrate of this transporter. We further show that marein can bind to the conserved amino acid residue F439 of ABCG2, a critical site for drug-substrate interaction. Moreover, marein can significantly sensitize the ABCG2-expressing tumor cells to chemotherapeutic drugs such as topotecan, mitoxantrone, and olaparib. This study reveals a novel role and mechanism of marein in modulating drug resistance, and may have important implications in treatment of cancers that are resistant to chemotherapeutic drugs that belong to the substrates of ABCG2 transporters.

Insights into Antimicrobial and Anti-Inflammatory Applications of Plant Bioactive Compounds

Plants have long been thought to contribute to health promotion due to their fiber and phenolic content, as well as their inherent biological potential. The bioactive derivatives of medicinal plants are a valuable resource in the fight against serious diseases all around the world. The present review focuses on the current state of knowledge on the usage and medicinal applications of plant bioactives. Issues concerning the effect of aromatic plant derivatives on human gut microbiota and their antimicrobial and anti-inflammatory potentials are discussed and worth further exploring.

Marein reduces lipid levels via modulating the PI3K/AKT/mTOR pathway to induce lipophagy

ETHNOPHARMACOLOGICAL RELEVANCE

The capitulum of Coreopsis tinctoria Nutt. (CT, Xue-Ju in Chinese) is a precious medicine in Xinjiang Uygur Autonomous region of China. The Coreopsis tinctoria Nutt. is used to prevent and treat dyslipidemia, coronary heart disease, etc. Recent studies have shown that its extract has a pharmacological effect on hyperlipidemia and hyperglycemia.

AIM OF THE STUDY

The study aimed to systematically evaluate the lipid-lowering activity of CT through a mice model of hyperlipidemia and a human hepatoma G2 (HepG2) cells model of lipid accumulation, and to investigate its main active components and mechanism.

MATERIALS AND METHODS

Biochemical analysis of blood/liver lipids and liver histopathology were used to evaluate the effect of the aqueous extract of Coreopsis tinctoria Nutt. (AECT) on hyperlipidemia mice. High-performance liquid chromatography (HPLC) analysis was used to identify the main components in the AECT. Oil red O staining, immunofluorescence, western blotting, and determination of the total cholesterol (TC), total triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) were used to further study the effect and potential mechanism of the AECT main components on sodium oleate-induced lipid accumulation in HepG2 cells.

RESULTS

We confirmed the lipid-lowering activity of the aqueous extract and further identified flavonoids as its main components. Among them, five Coreopsis tinctoria Nutt. flavonoids mixture (FM) significantly reduced lipid droplet area, lipid content, TC, TG, and LDL-C levels, and elevated HDL-C levels in HepG2 cells induced by sodium oleate. Furthermore, they increased lipophagy in HepG2 lipid-accumulating cells, while decreasing the ratio of p-PI3K/PI3K, p-AKT/AKT, and p-mTOR/mTOR. Most importantly, marein may be a key component.

CONCLUSIONS

Our study demonstrated that AECT, with flavonoids as the main component, can improve diet-induced hyperlipidemia in obese mice. Among the main five flavonoids, marein plays a key role in promoting lipophagy by regulating the PI3K/AKT/mTOR pathway, resulting in a lipid-lowering effect.

Integrated UPLC-Q-TOF-MS/MS and Network Pharmacology Approach to Investigating the Metabolic Profile of Marein of Coreopsis tinctoria Nutt

Marein is the main active compound of Coreopsis tinctoria Nutt., and its main activities include antioxidant, hypoglycemic, and hypotensive. After oral administration of marein, the blood concentration of marein is low. The metabolites of marein have not been reported systematically. In this study, a rapid and systematic method based on ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS/MS) was established to detect metabolites of marein in vivo (plasma and urine) after oral administration and injection. Sixty-one metabolites were identified. The metabolites are formed through a wide range of metabolic reactions, including hydroxylation, glucuronidation, methylation, hydrolysis, and desorption of hydrogen. The liver microsome incubation was further used to investigate the metabolic rate of marein. Network pharmacology was applied to study the targets and pathways of marein and its metabolites. Marein and its metabolites act on the same targets to enhance the therapeutic effect. This research illuminates the metabolites and metabolic reaction of marein and establishes a basis for the development and rational utilization of C. tinctoria. Meanwhile, the analysis of prototype and metabolites together by network pharmacology techniques could provide a methodology for the study of component activity.

Anti-hyperglycemic effects of Eryngium billardierei F. Delaroche extract on insulin-resistance HepG2 cells in vitro

BACKGROUND

Insulin resistance as a major problem is associated with type 2 diabetes mellitus. This study investigated the effect of Eryngium billardierei on insulin-resistance induced HepG2 cells.

METHODS AND RESULTS

MTT method was used to evaluate the viability of HepG2 cells treated with various doses of E. billardierei extract. An insulin-resistance model was established in HepG2 cells. Next, MTT assay and Acridine orange staining were performed to investigate the viability of cells in the vicinity of different concentrations of insulin, pioglitazone, and E. billardierei extract in an insulin-resistance media. The glucose uptake test was performed to select the optimal insulin concentration. Expression levels of IR, G6Pase, and PEPCK genes were assessed by real-time RT-PCR. According to obtained data, E. billardierei at concentrations of 0.5 and 1 mg/mL show no toxicity on cells. Furthermore, based on MTT assay and glucose uptake test 10^-5 mol/L insulin was chosen as the model group to induce insulin-resistance in HepG2 cells for gene expression analysis. Finally, 1 mg/mL E. billardierei not only induced no cytotoxicity but also showed an increase in the expression of IR as well as a reduction in G6Pase and PEPCK level compared to the control and model groups.

CONCLUSIONS

The obtained data indicated that 1 mg/mL E. billardierei might have an anti-insulin resistance effect on insulin-resistance HepG2 cells in vitro and could be a promising candidate with anti-hyperglycemic properties for diabetes treatments.

Network Pharmacology-Based Dissection of the Active Ingredients and Protective Mechanism of the Salvia Miltiorrhiza and Panax Notoginseng Herb Pair against Insulin Resistance

The Salvia miltiorrhiza and Panax notoginseng herb pair (DQ) has been widely utilized in traditional Chinese medicine for the longevity and for preventing and treating cardio-cerebrovascular diseases. Often associated with cardio-cerebrovascular diseases are comorbidities such as insulin resistance. However, the protective mechanisms of DQ against insulin resistance remain not well understood. Through network pharmacology analysis, a total of 94 candidate active compounds selected from DQ (61 from S. miltiorrhiza Bunge and 33 from P. notoginseng (Burk.) F. H. Chen) interacted with 52 corresponding insulin resistance-related targets, which mainly involved insulin resistance and the AMPK signaling pathway. Furthermore, the contribution index calculation results indicated 25 compounds as the principal components of this herb pair against insulin resistance. Among them, ginsenoside F2, protocatechuic acid, and salvianolic acid B were selected and validated to promote glucose consumption through activating AMPK phosphorylation and upregulating GLUT4 in insulin-resistant cell model (HepG2/IR) cells. These findings indicated that DQ has the potential for repositioning in the treatment of insulin resistance mainly through the AMPK signaling pathway.

Traditional uses, phytochemistry, pharmacology, and toxicology of Coreopsis tinctoria Nutt.: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Coreopsis tinctoria Nutt. (family Asteraceae) is an important traditional medicine in North America, Europe, and Asia for quite a long historical period, which has received great attention due to its health-benefiting activities, including disinfection, treatment sexual infection, diarrhoea, acute and chronic dysentery, red-eye swelling as well as pain, heat, thirst, hypertension, palpitation, gastrointestinal discomfort, and loss of appetite.

AIM OF THE REVIEW

The purpose of this review is to give an overview of the current phytochemistry and pharmacological activities of C. tinctoria, and reveals the correlation among its traditional uses, phytochemistry, pharmacological profile, and potential toxicity.

MATERIALS AND METHODS

This review is based on published studies and books from electronic sources and library, including the online ethnobotanical database, ethnobotanical monographs, Scopus, SciFinder, Baidu Scholar, CNKI, and PubMed. These reports are related to the traditional uses, phytochemistry, pharmacology, and toxicology of C. tinctoria.

RESULTS

Coreopsis tinctoria is traditionally used in diarrhoea, infection, and chronic metabolic diseases. From 1954 to now, more than 120 chemical constituents have been identified from C. tinctoria, such as flavonoids, polyacetylenes, polysaccharides, phenylpropanoids, and volatile oils. Flavonoids are the major bioactive components in C. tinctoria. Current research has shown that its extracts and compounds possess diverse biological and pharmacological activities such as antidiabetes, anti-cardiovascular diseases, antioxidant, anti-inflammatory, protective effects on organs, neuroprotective effects, antimicrobial, and antineoplastic. Studies in animal models, including acute toxicity, long-term toxicity, and genotoxicity have demonstrated that Snow Chrysanthemum is a non-toxic herb, especially for its water-soluble parts.

CONCLUSIONS

Recent findings regarding the main phytochemical and pharmacological properties of C. tinctorial have confirmed its traditional uses in anti-infection and treatment of chronic metabolic disease and, more importantly, have revealed the plant as a valuable medicinal plant resource for the treatment of a wide range of diseases. The available reports indicated that most of the bioactivities in C. tinctorial could be attributed to flavonoids. However, higher quality studies on animals and humans studies are required to explore the efficacy and mechanism of action of C. tinctoria in future.

FoxO1 is required for high glucose-dependent cardiac fibroblasts into myofibroblast phenoconversion

In the normal heart, cardiac fibroblasts (CFs) maintain extracellular matrix (ECM) homeostasis, whereas in pathological conditions, such as diabetes mellitus (DM), CFs converse into cardiac myofibroblasts (CMFs) and this CFs phenoconversion increase the synthesis and secretion of ECM proteins, promoting cardiac fibrosis and heart dysfunction. High glucose (HG) conditions increase TGF-β1 expression and FoxO1 activity, whereas FoxO1 is crucial to CFs phenoconversion induced by TGF-β1. In addition, FoxO1 increases CTGF expression, whereas CTGF plays an active role in the fibrotic process induced by hyperglycemia. However, the role of FoxO1 and CTGF in CFs phenoconversion induced by HG is not clear. In this study, we investigated the effects of FoxO1 pharmacological inhibition on CFs phenoconversion in both in vitro and ex vivo models of DM. Our results demonstrate that HG induces CFs phenoconversion and FoxO1 activation. Moreover, AS1842856, a pharmacological inhibitor of FoxO1 activity, prevents CFs phenoconversion and CTGF expression increase induced by HG, whereas these results were corroborated by FoxO1 silencing. Additionally, K252a, a pharmacological blocker of CTGF receptor, prevents HG-induced CFs phenoconversion, which was corroborated with CTGF expression knockdown. Furthermore, through CFs isolation from heart of diabetic rats, we showed that hyperglycemia induces FoxO1 activation, the increase of CTGF expression and CFs phenoconversion, whereas the FoxO1 activity inhibition reverses the effects induced by hyperglycemia on CFs. Altogether, our results demonstrate that FoxO1 and CTGF are necessary for CFs phenoconversion induced by HG and suggest that both proteins are likely to become a potential targeted drug for fibrotic response induced by hyperglycemic conditions.

Marein ameliorates Ang II/hypoxia-induced abnormal glucolipid metabolism by modulating the HIF-1α/PPARα/γ pathway in H9c2 cells

The objectives of this study were to investigate the effects of marein, a major bioactive compound in functional food Coreopsis tinctoria, in hypertrophic H9c2 cells. Treating angiotensin II/hypoxia-stimulated H9c2 cells with marein led to decreasing cell surface area, intracellular total protein, atrial natriuretic peptide, and free fatty acids levels, but increasing glucose level. Marein treatment decreased hypoxia inducible factor-1α (HIF-1α), peroxisome proliferator activated receptor γ (PPARγ), medium chain acyl-coenzyme A dehydrogenase, glucose transporter-4, and glycerol-3-phosphate acyltransferase protein expressions, and increased PPARα, fatty acid transport protein-1, carnitine palmitoyltransferase-1, and pyruvate dehydrogenase kinase-4 protein expressions. Similar results were observed in HIF-1α-overexpressing H9c2 cells, whereas these effects were abolished in siRNA-HIF-1α-transfected H9c2 cells. It was concluded that marein could ameliorate abnormal glucolipid metabolism in hypertrophic H9c2 cells, and the effects could be attributable to reduction of HIF-1α expression and subsequent regulation PPARα/γ-mediated lipogenic gene expressions.

Marein ameliorates diabetic nephropathy by inhibiting renal sodium glucose transporter 2 and activating the AMPK signaling pathway in db/db mice and high glucose-treated HK-2 cells

Marein, an active component of the Coreopsis tinctoria Nutt. plant, is known to improve diabetic nephropathy (DN). However, its anti-diabetic functions in DN and potential mechanisms remain unclear. The aim of this study was to elucidate the effects and mechanisms of Marein in diabetic db/db mice with DN, and in high glucose-treated HK-2 cells. In vivo, treating diabetic db/db mice with Marein for 12 consecutive weeks restored diabetes-induced hyperglycemia and dyslipidemia, and ameliorated renal function deterioration, glomerulosclerosis, and renal ectopic lipid deposition. Marein exerted renoprotective effects by directly inhibiting renal tubule sodium glucose transporter 2 (SGLT2) expression, and then activating the AMP-activated protein kinase (AMPK)/acetyl CoA carboxylase (ACC)/peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) pathway in db/db mice. Meanwhile, Marein ameliorated fibrosis and inflammation by suppressing the pro-inflammatory factors interleukin-6 (IL-6) and monocyte chemotactic protein-1 (MCP-1), and expression of the extracellular matrix proteins, fibronectin (FN) and collagen 1 (COL1) in diabetic mice. In vitro, MDCK monolayer cells were established to explore the characteristics of Marein transmembrane transport. Marein was found to be absorbed across the membrane at a medium level that involved active transport and this was mediated by SGLTs. In HK-2 cells, Marein decreased uptake of the fluorescent glucose analog, 2-NBDG, by 22 % by inhibiting SGLT2 expression. In high glucose-treated HK-2 cells, Marein decreased SGLT2 expression and increased phosphorylated (p)-AMPK/p-ACC to improve high glucose-induced cellular dysfunction. Furthermore, Marein treatment decreased SGLT2 expression in SGLT2-overexpressing HK-2 cells. In addition, molecular docking and dynamics analysis revealed that SGLT2 was a direct target of Marein. Collectively, our results demonstrated that Marein ameliorates DN by inhibiting renal SGLT2 and activating p-AMPK, suggesting Marein can potentially prevent DN by suppressing renal SGLT2 expression directly.

Curcumin metabolites contribute to the effect of curcumin on ameliorating insulin sensitivity in high-glucose-induced insulin-resistant HepG2 cells

ETHNOPHARMACOLOGICAL EVIDENCE

Curcumin (CUR) is the active ingredient of Traditional Chinese Medicine turmeric (Curcuma longa L.), which has been used for treatment of diabetes in Ayurveda and China. CUR exerts potent anti-insulin-resistant effects in various cell lines. However, previous studies indicated CUR was metabolized extensively in vivo and massively degraded in a medium alkaline buffer solution. The real active component of the anti-insulin-resistant activity of CUR in vitro is not clear.

AIM OF THE STUDY

Our study identified the functional contribution of the metabolites of CUR and the related molecular mechanism in improving insulin sensitivity.

MATERIALS AND METHODS

HPLC and UPLC-QQQ-MS analyses were used to investigate the stability and metabolism of CUR in HepG2 cells. The effect of the metabolic products of CUR on insulin sensitivity was evaluated in high glucose (HG)-induced insulin-resistant HepG2 cells. A network pharmacology approach was used to examine the potential targets of the metabolites, and Western blotting was performed to verify changes in the targets.

RESULTS

CUR was unstable in the cell culture medium, but the prototypes, metabolites and degradation products of CUR coexisted in the HepG2 cell culture experiment. The insulin sensitivity assay demonstrated that CUR and its metabolites enhanced insulin sensitivity in HG-induced insulin-resistant HepG2 cells, but the total degradation products of CUR may not play the major role. Similar to CUR, hexahydrocurcumin (HHC) and octahydrocurcumin (OHC) improved insulin sensitivity by strengthening the PI3K-AKT-GSK3B signal and suppressing the phosphorylation of ERK/JNK in HG-induced insulin-resistant HepG2 cells.

CONCLUSIONS

Metabolites of CUR played a critical role in counteracting insulin resistance in HG-induced HepG2 cells. CUR exerted anti-insulin resistance effect in HepG2 cells in a multi-component, multi-target, and multi-pathway manner.

A Systematic Review on Anti-diabetic Properties of Chalcones

The use of anti-diabetic drugs has been increasing worldwide and the evolution of therapeutics has been enormous. Still, the currently available anti-diabetic drugs do not present the desired efficacy and are generally associated with serious adverse effects. Thus, entirely new interventions, addressing the underlying etiopathogenesis of type 2 diabetes mellitus, are required. Chalcones, secondary metabolites of terrestrial plants and precursors of the flavonoids biosynthesis, have been used for a long time in traditional medicine due to their wide-range of biological activities, from which the anti-diabetic activity stands out. This review systematizes the information found in literature about the anti-diabetic properties of chalcones, in vitro and in vivo. Chalcones are able to exert these properties by acting in different therapeutic targets: Dipeptidyl Peptidase 4 (DPP-4); Glucose Transporter Type 4 (GLUT4), Sodium Glucose Cotransporter 2 (SGLT2), α-amylase, α-glucosidase, Aldose Reductase (ALR), Protein Tyrosine Phosphatase 1B (PTP1B), Peroxisome Proliferator-activated Receptor-gamma (PPARγ) and Adenosine Monophosphate (AMP)-activated Protein Kinase (AMPK). Chalcones are, undoubtedly, promising anti-diabetic agents, and some crucial structural features have already been established. From the Structure-Activity Relationships analysis, it can generally be stated that the presence of hydroxyl, prenyl and geranyl groups in their skeleton improves their activity for the evaluated anti-diabetic targets.

Polyphenol-rich extract of Zhenjiang aromatic vinegar ameliorates high glucose-induced insulin resistance by regulating JNK-IRS-1 and PI3K/Akt signaling pathways

Zhenjiang aromatic vinegar is a famous traditional fermented cooking ingredient in China, with multiple nutritional and medicinal applications. Zhenjiang aromatic vinegar extract (100-400 μg/mL) is rich in polyphenols increased the glucose uptake and glucose consumption in high glucose-induced insulin resistant HepG2 (IR-HepG2) cells. Zhenjiang aromatic vinegar extract enhanced glycogen synthesis and attenuated gluconeogenesis by regulating key enzymes in IR-HepG2 cells. In addition, Zhenjiang aromatic vinegar extract ameliorated high glucose-induced IR by inhibiting phosphorylated insulin receptor substrate-1 (IRS-1) expression and activating phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway in IR-HepG2 cells. Moreover, Zhenjiang aromatic vinegar extract reduced reactive oxygen species generation and phosphorylated c-Jun NH₂ terminal kinase (JNK) expression in IR-HepG2 cells. The attenuation of the high glucose is owned to the PI3K/Akt pathway activation, glycogen synthesis induction and gluconeogenesis suppression in IR-HepG2 cells.

Marein protects human nucleus pulposus cells against high glucose-induced injury and extracellular matrix degradation at least partly by inhibition of ROS/NF-κB pathway

Intervertebral disc degeneration (IDD), a major cause of discogenic low back pain, is a musculoskeletal disorder involving the apoptosis of nucleus pulposus cells (NPCs) and extracellular matrix (ECM) degradation. Marein is a major active flavonoid ingredient extracted from the hypoglycemic plant Coreopsis tinctoria with several beneficial biological activities including anti-diabetic effects. Nevertheless, there are no reports concerning the effects of marein on IDD. Our study aimed to evaluate the effects of marein on high glucose (HG)-induced injury and ECM degradation in human NPCs (HNPCs). CCK-8 assay was applied to evaluate cell viability. Flow cytometry analysis, a cell death detection ELISA, and caspase-3 activity assay were used to assess apoptosis. The mRNA expression of ECM-related proteins matrix metalloproteinase (MMP)-3, MMP-13, Collagen II, and aggrecan were determined by qRT-PCR. The changes of the nuclear factor-kappa B (NF-κB) pathway were examined by western blot. Stimulation with HG significantly reduced cell viability and induced apoptosis in HNPCs. Moreover, HG exposure increased MMP-3 and MMP-13 expression and decreased Collagen II and aggrecan expression in HNPCs. Notably, marein effectively alleviated HG-induced viability reduction, apoptosis and ECM degradation in HNPCs. We also found that marein inhibited HG-induced ROS generation and NF-κB activation in HNPCs. Inhibition of NF-κB pathway reinforced HG-induced injury and ECM degradation in HNPCs. In summary, marein protected HNPCs against HG-induced injury and ECM degradation at least partly by inhibiting the ROS/NF-κB pathway.

Effect of Konjac Mannan Oligosaccharides on Glucose Homeostasis via the Improvement of Insulin and Leptin Resistance In Vitro and In Vivo

Functional oligosaccharides, particularly konjac mannan oligosaccharides (KMOS), can regulate glucose metabolism. However, the molecular mechanisms involved in the hypoglycemic effect of KMOS remain largely unknown. Here, the effect of KMOS supplementation on glucose homeostasis was evaluated in both high-fat diet (HFD)-fed C57BL/6J mice and high-glucosamine-induced HepG2 cells. KMOS supplementation remarkably ameliorated the fasting blood glucose, glucose tolerance, and insulin tolerance of HFD-fed mice. Abnormalities of triglyceride and glycogen metabolism in the liver induced by the HFD were reversed by KMOS supplementation. The insulin signaling pathway was activated by KMOS, with stimulation of GLUT2 membrane translocation and glucose uptake in HepG2 cells via the AMPK pathway. Moreover, KMOS suppressed p-mTOR expression and stimulated the GSK-3β/CREB pathway via the AMPK pathway. KMOS significantly upregulated leptin receptor expression and downregulated PTP1B and SOCS3 levels in the liver and brain, with a decreased serum leptin concentration. Phosphorylation of JAK2 and STAT3 in the liver was activated by KMOS supplementation, while the expressions of Sirt1, Tfam, and Pgc1-α in the brain were elevated. Conclusively, KMOS attenuated HFD-induced glucose metabolism dysfunction through the regulation of insulin resistance and leptin resistance. This finding indicates that KMOS have potential value as an anti-hyperglycemic dietary supplement.

Therapeutic Mechanisms of Herbal Medicines Against Insulin Resistance: A Review

Insulin resistance is a condition in which insulin sensitivity is reduced and the insulin signaling pathway is impaired. Although often expressed as an increase in insulin concentration, the disease is characterized by a decrease in insulin action. This increased workload of the pancreas and the consequent decompensation are not only the main mechanisms for the development of type 2 diabetes (T2D), but also exacerbate the damage of metabolic diseases, including obesity, nonalcoholic fatty liver disease, polycystic ovary syndrome, metabolic syndrome, and others. Many clinical trials have suggested the potential role of herbs in the treatment of insulin resistance, although most of the clinical trials included in this review have certain flaws and bias risks in their methodological design, including the generation of randomization, the concealment of allocation, blinding, and inadequate reporting of sample size estimates. These studies involve not only the single-flavored herbs, but also herbal formulas, extracts, and active ingredients. Numerous of in vitro and in vivo studies have pointed out that the role of herbal medicine in improving insulin resistance is related to interventions in various aspects of the insulin signaling pathway. The targets involved in these studies include insulin receptor substrate, phosphatidylinositol 3-kinase, glucose transporter, AMP-activated protein kinase, glycogen synthase kinase 3, mitogen-activated protein kinases, c-Jun-N-terminal kinase, nuclear factor-kappaB, protein tyrosine phosphatase 1B, nuclear factor-E2-related factor 2, and peroxisome proliferator-activated receptors. Improved insulin sensitivity upon treatment with herbal medicine provides considerable prospects for treating insulin resistance. This article reviews studies of the target mechanisms of herbal treatments for insulin resistance.

Transcriptome analysis reveals the mechanism of the effect of flower tea Coreopsis tinctoria on hepatic insulin resistance

Non-Camellia tea and herbal medicine help prevent the development of diabetes and other metabolic diseases. Previous studies revealed that Coreopsis tinctoria (CT) flower tea increases insulin sensitivity and, in some high-fat diet (HFD)-fed rats, even prevents hepatic metabolic disorders. However, the molecular mechanisms by which CT improves insulin resistance are not known. In this study, six-week-old rats were fed a normal diet (ND), an HFD or an HFD supplemented with CT for 8 weeks. Serum samples were collected, and the livers were extracted for RNA-seq gene expression analysis. Real-time PCR and western blotting further verified the RNA-seq results. In our results, dietary CT ameliorated HFD-induced hepatosteatosis, glucose intolerance, and insulin resistance. In the HFD group, 1667 differentially expressed genes (DEGs) were identified compared with the ND group. In the CT group, 327 DEGs were identified compared with the HFD group. Some of these DEGs were related to insulin signalling, hepatic lipogenesis and glucose homeostasis. This study suggested that insulin resistance with hyperinsulinaemia, and not insulin insufficiency, is an early problem in HFD-fed rats, and CT downregulates insulin secretion genes (e.g., Rasd1, Stxbp1 and Sfxn1). Hepatic gene and protein expression analyses indicated that the regulatory effects of CT on glucose and lipid homeostasis are likely mediated via the Akt/FoxO1 signalling pathway and are regulated by the transcription factors hairy and enhancer of split 1 (HES1) and small heterodimer partner (SHP). Our study provides transcriptomic evidence of the complex pathogenic mechanism involved in hepatic insulin resistance and proves that supplementation with CT improves insulin resistance at a global scale.

miR-96 and autophagy are involved in the beneficial effect of grape seed proanthocyanidins against high-fat-diet-induced dyslipidemia in mice

We aimed to investigate the possible signaling pathways underlying the regulation of grape seed proanthocyanidins extracts (GSPE) on lipid metabolism. One hundred male C57BL/6 mice were divided into four groups: control group (normal diet), GSPE group (normal diet + GSPE), high-fat diet group (HFD), and high-fat diet plus GSPE (200 mg/kg/day) group (HFD + GSPE). Mice received the diets for 180 days. Body weight and serum lipid levels were measured. Autophagic flux characteristics, such as accumulation of lipids, mitochondria, and autophagosomes in the liver, were detected using transmission electron microscopy. Expression profile of microRNAs (miRNAs) in the liver was determined using RNA microarray and quantitative real time polymerase chain reaction (qRt-PCR). GSPE significantly decreased the weight gain, serum levels of triglycerides, total cholesterol, and low-density lipoprotein cholesterol but increased high-density lipoprotein cholesterol in the HFD mice. Autophagic flux was significantly increased by HFD but decreased by GSPE treatment. GSPE significantly attenuated HFD-induced miR-96 upregulation, which in turn reduced the expressions of miR-96 downstream molecules, FOXO1, mTOR, p-mTOR, and LC3A/B. These results suggested that the miR-96 is involved in the protective effect of GSPE against HFD-induced dyslipidemia. Possible mechanisms might be through mTOR and FOXO1, which facilitate autophagic flux for clearance of lipid accumulation.

Anti-hyperglycemic and anti-hyperlipidemia effects of the alkaloid-rich extract from barks of Litsea glutinosa in ob/ob mice

The present study investigated the anti-hyperglycemic and anti-hyperlipidemia effects of the alkaloid-rich extract from Litsea glutinosa barks (CG) in ob/ob mice. CG was orally administrated (50, 100 and 200 mg/kg) to ob/ob mice for 4 weeks. Parameters of glucose metabolism, hepatotoxicity, hyperlipidemia and inflammation were measured. CG was chemically characterized using UPLC-QTOF-MS. CG dose-dependently decreased body and fat weights without reducing average food intake. CG (100–200 mg/kg) significantly reduced the serum levels of fasting glucose, glycosylated hemoglobin (HbAlc) and glycosylated serum protein (GSP). CG increased insulin sensitivity as manifested by decreased fasting serum insulin, reduced homeostasis model assessment-estimated insulin resistance (HOMA-IR) and improved oral glucose tolerance. CG also alleviated dyslipidemia, ameliorated liver steatosis, increased the activity of serum lipase and alleviated inflammation. The activities of liver pyruvate kinase and glucokinase as well as liver content of glycogen were increased after CG treatment. CG was rich in alkaloids and eight main alkaloids were identified, many of which had been demonstrated to possess adequate anti-diabetic activities. These results suggest that the alkaloid-rich extract of CG possesses potential anti-hyperglycemic and anti-hyperlipidemic effects and can be utilized as an effective agent for the treatment of type 2 diabetes.

Protective effects of rutin on liver injury in type 2 diabetic db/db mice

The aim of this study was to evaluate the protective effect of rutin on the liver of type 2 diabetic mice and explore the correlation mechanism. The db/db mice, selected as the type 2 diabetes mellitus (T2DM) models, have random blood glucose (RBG) and glucose level after 2 h of oral glucose loading of more than 16.7 mmol/L. After administration of 120 mg/kg or 60 mg/kg rutin, to T2DM mice, RBG, oral glucose tolerance, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in serum, and advanced glycation end products (AGEs) in vivo and vitro of different groups were detected. The liver pathological changes were observed under light and electron microscopy. Western blotting was used to detect the protein expression of insulin receptor substrate 2 (IRS-2) and phosphorylation of phosphatidylinositol 3 kinase (PI3K) on p85, Akt on Ser473, glycogen synthase kinase 3β (GSK-3β) on Ser9, real-time quantitative PCR was used to detect IRS-2 mRNA expression. Moreover, dynamically observing the effect of rutin on the generation of AGEs in non-enzymatic protein glycosylated system, Cell Counting Kit-8 (CCK-8) method was used to detect the effect of rutin on proliferation activity of HepG2 liver cells. The results showed that RBG and glucose levels of oral glucose tolerance test (OGTT) of mice in model group were significantly higher than that of normal group, which were significantly reduced after the rutin treatment. Rutin could reduce the ALT, AST activities and AGEs level in serum and potentiate the expression of IRS-2, P-PI3K (p85), P-Akt (Ser473), P-GSK-3β (Ser9) protein and IRS-2 mRNA in the liver tissue of db/db mice. Moreover, rutin could significantly alleviate the structure disorder of liver, reduce the degeneration and necrosis of liver cells and formation of collagen fibers of db/db mice. The results in vitro also showed that rutin could obviously inhibit the generation of AGEs, and promoted the proliferation activity of high glucose-stimulating HepG2 cells. In general, the protective effect of rutin on the liver of T2DM may be mediated by facilitating signal transduction and activated state of insulin IRS-2/PI3K/Akt/GSK-3β signal pathway, promoting hepatocyte proliferation, reducing blood glucose level and generation of AGEs.

Exposure to 2,4-dichlorophenoxyacetic acid induced PPARβ-dependent disruption of glucose metabolism in HepG2 cells

2,4-Dichlorophenoxyacetic acid is one of the most widely used herbicides. Its impact on health is increasingly attracting great attentions. This study aimed to investigate the effect of 2,4-dichlorophenoxyacetic acid on glucose metabolism in HepG2 cells and the underlying mechanism. After 24 h exposure to 2,4-dichlorophenoxyacetic acid, glycogen was measured by PAS staining and glucose by ELISA in HepG2 cells. The expression of genes involved in glucose metabolism was measured by real-time PCR, Western blotting, and immunofluorescence. HepG2 cells presented more extracellular glucose consumption and glycogen content after exposed to 2,4-dichlorophenoxyacetic acid. Expression of gluconeogenesis-related genes, FoxO1, and CREB is significantly elevated. Moreover, PPARβ was up-regulated dose-dependently. SiRNA knockdown of PPARβ completely rescued the increase of glycogen accumulation and glucose uptake, and the up-regulation of FOXO1 and CREB expression. Our findings propose novel mechanisms that 2,4-dichlorophenoxyacetic acid causes glucose metabolism dysfunction through PPARβ in HepG2 cells.

EGCG evokes Nrf2 nuclear translocation and dampens PTP1B expression to ameliorate metabolic misalignment under insulin resistance condition

As a major nutraceutical component of green tea (-)-epigallocatechin-3-gallate (EGCG) has attracted interest from scientists due to its well-documented antioxidant and antiobesity bioactivities. In the current study, we aimed to investigate the protective effect of EGCG on metabolic misalignment and in balancing the redox status in mice liver and HepG2 cells under insulin resistance condition. Our results indicated that EGCG accelerates the glucose uptake and evokes IRS-1/Akt/GLUT2 signaling pathway via dampening the expression of protein tyrosine phosphatase 1B (PTP1B). Consistently, ectopic expression of PTP1B by Ad-PTP1B substantially impaired EGCG-elicited IRS-1/Akt/GLUT2 signaling pathway. Moreover, EGCG co-treatment stimulated nuclear translocation of Nrf2 by provoking P13K/AKT signaling pathway and thus modulated the downstream expressions of antioxidant enzymes such as HO-1 and NQO-1 in HepG2 cells. Furthermore, knockdown Nrf2 by small interfering RNA (siRNA) notably enhanced the expression of PTP1B and blunt EGCG-stimulated glucose uptake. Consistent with these results, in vivo study revealed that EGCG supplement significantly ameliorated high-fat and high-fructose diet (HFFD)-triggered insulin resistance and oxidative stress by up-regulating the IRS-1/AKT and Keap1/Nrf2 transcriptional pathways. Administration of an appropriate chemopreventive agent, such as EGCG, could potentially serve as an additional therapeutic intervention in the arsenal against obesity.