Cyclocarya paliurus Triterpenoids Improve Diabetes-Induced Hepatic Inflammation via the Rho-Kinase-Dependent Pathway

Black mulberry extract inhibits hepatic adipogenesis through AMPK/mTOR signaling pathway in T2DM mice

ETHNOPHARMACOLOGICAL RELEVANCE

Black mulberry (Morus nigra L.) is an ancient dual-use plant resource for medicine and food. It is widely used in Uyghur folklore for hypoglycemic treatment and is a folkloric plant medicine with regional characteristics. However, the mechanism of Morus nigra L. treatment in diabetes mellitus has not been fully understood, especially from the perspective of hepatic lipid accumulation is less reported.

OBJECTIVE OF THIS STUDY

This study was to explore the potential of Morus nigra L. fruit ethyl acetate extract (MNF-EA) to reduce blood sugar levels by preventing the production of hepatic lipogenesis and to provide more evidence for the use of MNF-EA as an adjuvant therapy for type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS

In this study, the chemical composition of MNF-EA was first analyzed and characterized using UPLC-Q-TOF-MS technique. A series of in vitro studies were performed with HepG2-IR cells and oleic acid (OA)-induced HepG2 cells, including MTT assay, glucose uptake assay, oil red O staining and Western blot analysis. The STZ-HFD co-induced T2DM mice were employed for in vivo research, including physical indices, biochemical analysis, histopathological examination, and Western blot analysis.

RESULTS

The 19 compounds in MNF-EA were identified by UPLC-Q-TOF-MS technique. Insulin resistance (IR) and lipid droplet accumulation in HepG2 cells were greatly improved by MNF-EA treatment, which had no appreciable side effects at the dosage used. In T2DM mice, MNF-EA decreased fasting blood glucose (FBG), saved body weight, and significantly improved oral glucose tolerance (OGTT) and IR status. In addition, MNF-EA treatment also improved lipid metabolism disorders and liver function in T2DM mice. Histopathological sections showed that MNF-EA treatment reduced hepatic steatosis. Mechanistic studies suggest that MNF-EA acted through the AMPK/mTOR pathway.

CONCLUSIONS

These results suggest that MNF-EA has great potential to reverse the metabolic abnormalities associated with T2DM by regulating the AMPK/mTOR signaling pathway. Therefore, we believe that MNF is a promising medicinal and food-homologous agent to improve T2DM.

Triterpenoids from the Leaves of Cyclocarya paliurus and Their Glucose Uptake Activity in 3T3-L1 Adipocytes

Four new dammarane triterpenoid saponins cypaliurusides Z₁-Z₄ (1-4) and eight known analogs (5-12) were isolated from the leaves of Cyclocarya paliurus. The structures of the isolated compounds were determined using a comprehensive analysis of 1D and 2D NMR and HRESIMS data. The docking study demonstrated that compound 10 strongly bonded with PTP1B (a potential drug target for the treatment of type-II diabetes and obesity), hydrogen bonds, and hydrophobic interactions, verifying the importance of sugar unit. The effects of the isolates on insulin-stimulated glucose uptake in 3T3-L1 adipocytes were evaluated and three dammarane triterpenoid saponins (6, 7 and 10) were found to enhance insulin-stimulated glucose uptake in 3T3-L1 adipocytes. Furthermore, compounds 6, 7, and 10 exhibited potent abilities to promote insulin-stimulated glucose uptake in 3T3-L1 adipocytes in a dose-dependent manner. Thus, the abundant dammarane triterpenoid saponins from C. paliurus leaves exhibited stimulatory effects on glucose uptake with application potential as a antidiabetic treatment.

New triterpenoids from the Cyclocarya paliurus (Batalin) Iljinskaja and their anti-fibrotic activity

Cyclocarya paliurus, a Chinese herbal medicine and new food resource, contains a triterpenic-acid-rich extract that demonstrated ameliorative effect on diabetic nephropathy (DN). A more in-depth discovery of functional components led to the isolation of seven new triterpenoids including two pentacyclic triterpenes, 1α,2α,3β,23-tetrahydroxyolean-12-en-28-oic acid and 2α,3β,22α-tirhydroxyurs-12-en-28-oic acid 28-O-β-D-glucopyranoside, and five tetracyclic triterpenoid glycosides (cypaliurusides N-R), together with twelve known compounds from the leaves of C. paliurus. Their structures were determined using a comprehensive analysis of chemical and spectroscopic data. Partial compounds were assessed for anti-fibrotic activities in high-glucose and TGF-β1 induced HK-2 cells. Compound 16 remarkably decreased the level of fibronectin with an inhibition rate of 37.1%. Furthermore, 16 effectively alleviated the epithelial-mesenchymal transformation (EMT) process by upregulating E-cadherin expression and downregulating α-SMA expression, and it significantly decreased the level of the transcriptional inhibitors (Snail and Twist) of E-cadherin. The discovery of anti-fibrotic compounds from C. paliurus provides the potential utilization and functional candidates for the DN prevention.

Cyclocarya paliurus triterpenoids suppress hepatic gluconeogenesis via AMPK-mediated cAMP/PKA/CREB pathway

BACKGROUND

Abnormal enhancement of hepatic gluconeogenesis is a vital mechanism of the pathogenesis of Type 2 diabetes mellitus (T2DM); thus, its suppression may present an efficient therapeutic strategy for T2DM. Cyclocarya paliurus (CP), a plant species native to China, has been reported to have anti-hyperglycemia activity. Our previous studies have revealed that Cyclocarya paliurus triterpenic acids (CPT) exert the favorable glucose-lowering activity, but the regulatory effect of CPT on hepatic gluconeogenesis is still unclarified.

PURPOSE

This study aimed to investigate the potential role and mechanism of CPT in gluconeogenesis.

STUDY DESIGN

In this study, the ameliorative effect and underlying mechanism of CPT on gluconeogenesis were investigated: high-fat diet and streptozotocin-induced T2DM mice and glucagon-challenged mouse primary hepatocytes.

METHODS

T2DM model mice with or without oral administration of CPT for 4 weeks were monitored for body weight, glucose and lipid metabolism. Hematoxylin and eosin staining was used to observe liver lipid deposition. Real-time PCR assays were performed to examine the mRNA expression of glucose-6-phosphate (G6Pase), and phosphoenolpyruvate carboxykinase (PEPCK), two key enzymes involved in liver gluconeogenesis. Western blotting was used to determine AMP-dependent protein kinase (AMPK) expression and induction of the glucagon signaling pathway. The possible mechanism of CPT on liver gluconeogenesis was further explored in glucagon-induced mouse primary hepatocytes.

RESULTS

In vivo and in vitro experiments revealed that CPT treatment significantly reduced fasting blood glucose, total cholesterol and triglyceride levels, and improved insulin resistance. Furthermore, CPT could obviously decreased the mRNA and protein expression of G6Pase and PEPCK, the cyclic AMP content, the phosphorylation level of protein kinase A and cyclic AMP response element-binding protein. But CPT promoted the phosphorylation of AMP-dependent protein kinase (AMPK) and activation of phosphodiesterase 4B. Mechanistically, intervention with Compound C (an AMPK inhibitor) partially blocked the suppressive effect of CPT on hepatic gluconeogenesis.

CONCLUSION

These findings suggested that CPT may inhibit hepatic gluconeogenesis against T2DM by activating AMPK.

Advances on Cyclocarya paliurus polyphenols: Extraction, structures, bioactivities and future perspectives

Cyclocaryapaliurus (C. paliurus) is an edible and medicinal plant, distributed in southern China. As a kind of new food raw material, the leaves of C. paliurus are processed as tea products in daily life. C. paliurus is recognized as a good source to polyphenols, showing excellent bioactivities, which has attracted more and more attention. Polyphenols are important functional bioactive components in C. paliurus. C. paliurus polyphenols perform nutritional functions in anti-diabetes, anti-hyperlipidemic, anti-obesity, anti-oxidant, and other activities. In this review, we summarize the research progress of extraction technologies, structural characteristics, and bioactivities of C. paliurus polyphenols. Other potential functions of C. paliurus polyphenols are prospected. This review provides a reference for further research and applications of C. paliurus polyphenols in a field of functional food and medicines.

The Leaves of Cyclocarya paliurus: A Functional Tea with Preventive and Therapeutic Potential of Type 2 Diabetes

Type 2 diabetes mellitus (T2DM) has become a universal and chronic global public health concern and causes multiple complex complications. In order to meet the rapidly growing demand for T2DM treatment, increased research has been focused on hypoglycemic drugs. Cyclocarya paliurus (Batal.) Iljinsk is the only living species of the genus Cyclocarya Iljinskaja, whose leaves have been extensively used as a functional tea to treat obesity and diabetes in China. An enormous amount of very recent pharmacological research on the leaves of C. paliurus has demonstrated that they carry out numerous biological activities, such as hypoglycemic, anti-inflammatory, and intestinal microbiota regulation. Multiple in vitro and in vivo studies have also shown that the extracts of C. paliurus leaves are innocuous and safe. This study aims to provide an up-to-date review of the botany, traditional uses, phytochemistry, pharmacological effects against diabetes, toxicology, and clinical studies of C. paliurus leaves, in hopes of promoting a better understanding of their role in the prevention and treatment of T2DM.

Cyclocarya paliurus triterpenoids attenuate glomerular endothelial injury in the diabetic rats via ROCK pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Cyclocarya paliurus (Batal.) Iljinskaja. (C. paliurus) is a distinctive traditional Chinese herb, with remarkable hypoglycemic capacity. Emerging evidence suggested that glomerular endothelial injury is a crucial pathological process of diabetic kidney disease (DKD). Our previous research found that C. paliurus triterpenoids fraction (CPT) has ameliorative effects on DKD. However, whether C. paliurus could counteract the glomerular endothelial injury of DKD is still undefined.

AIM OF THE STUDY

We aimed to investigate the effects of CPT on glomerular endothelial function and explore its underlying mechanisms with in vivo and in vitro experiments.

MATERIALS AND METHODS

The effects and possible mechanisms of CPT on glomerular endothelial injury in streptozotocin (STZ)-induced diabetic rats and H₂O₂-challenged primary rat glomerular endothelial cells were successively investigated.

RESULTS

In vivo, we found that CPT treatment obviously decreased the levels of blood glucose, microalbumin, BUN and mesangial expansion. Additionally, CPT could ameliorate renal endothelium function by reducing the content of VCAM-1 and ICAM-1, and blocking the loss of glycocalyx. In vitro, CPT could also alleviate H₂O₂-induced endothelial injury. Mechanistically, CPT remarkably increased the phosphorylation levels of Akt and eNOS, decreased the expression of ROCK and Arg₂in vivo and in vitro. Noticeably, the favorable effects mediated by CPT were abolished following ROCK overexpression with plasmid transfection.

CONCLUSION

These findings suggested that CPT could be sufficient to protect against glomerular endothelial injury in DKD through regulating ROCK pathway.

The Modulatory Effect of Cyclocarya paliurus Flavonoids on Intestinal Microbiota and Hypothalamus Clock Genes in a Circadian Rhythm Disorder Mouse Model

Circadian rhythm disruption is detrimental and results in adverse health consequences. We used a multi-omics profiling approach to investigate the effects of Cyclocarya paliurus flavonoid (CPF)-enriched diets on gut microbiota, metabolites, and hypothalamus clock genes in mice with induced circadian rhythm disruption. It was observed that CPF supplementation altered the specific composition and function of gut microbiota and metabolites induced by circadian rhythm disruption. Analysis showed that the abundance of Akkermansia increased, while the abundance of Clostridiales and Ruminiclostridium displayed a significant downward trend after the CPF intervention. Correlation analysis also revealed that these gut microbes had certain correlations with the metabolites, suggesting that CPFs help the intestinal microbiota to repair the intestinal environment and modulate the release of some beneficial metabolites. Notably, single-cell RNA-seq revealed that CPF supplementation significantly regulated the expression of genes associated with circadian rhythm, myelination, and neurodegenerative diseases. Altogether, these findings highlight that CPFs may represent a promising dietary therapeutic strategy for treating circadian rhythm disruption.

Metformin in Combination with Malvidin Prevents Progression of Non-Alcoholic Fatty Liver Disease via Improving Lipid and Glucose Metabolisms, and Inhibiting Inflammation in Type 2 Diabetes Rats

Background

Non-alcoholic fatty liver disease (NAFLD) is one of the primary causes of chronic liver disease and is closely linked to insulin resistance, type 2 diabetes mellitus (T2DM), and dyslipidemia. However, no effective drug therapies have been approved to treat this disease. The present research aimed to evaluate the therapeutic effects of the combination of oral hypoglycemic drug metformin (MET) and a natural product malvidin (MAL) on hepatic damage in HFD/STZ-induced diabetic rats.

Methods

Sprague-Dawley rats were divided into five groups: normal control group (NC), diabetic control group (DC), DC+MET group, DC+MAL group, and DC+MET+MAL group and treated for eight weeks. Blood and liver tissue samples were collected for metabolic parameters, histological, and RT-qPCR analysis.

Results

Our findings indicated that hyperglycemia, insulin resistance, hyperlipidemia, and non-alcoholic fatty liver disease (NAFLD) in diabetic rats were alleviated after oral treatment with MET and MAL, particularly their combination therapy. Besides, the expression of SREBP-1c, ACC, FAS, IL-6, IL-8, and NF-κB mRNA was down-regulated by MET+MAL, and the expression of PPARα, CPT1, and LPL was up-regulated by MET+MAL.

Conclusion

The evidence of this research indicated that the combination therapy may represent an efficient strategy against NAFLD in T2DM rats via improving lipid and glucose metabolisms, and inhibiting inflammation.

α-Glucosidase inhibitory and anti-inflammatory activities of dammarane triterpenoids from the leaves of Cyclocarya paliurus

Diabetes mellitus is caused by chronic inflammation and affects millions of people worldwide. Cyclocarya paliurus leaves have been widely used in traditional folk tea as a remedy for diabetes, but the antidiabetic constituents remain to be further studied. The α-glucosidase inhibitory and anti-inflammatory activities were examined to evaluate their effects on diabetes mellitus, and bioassay-guided separation of C. paliurus leaves led to the identification of twenty dammarane saponins, including eleven new dammarane saponins (1-11). The structures of the isolates were elucidated by spectroscopic methods. Bioactivity assay results showed that compounds 1 and 2 strongly inhibited α-glucosidase activity, with IC50 values ranging from 257.74 μM, 282.23 μM, and strongly inhibited the release of NO, with IC50 values of 9.10 μM, 9.02 μM. Moreover, compound 2 significantly downregulated the mRNA expression of iNOS, COX-2, IL-1β, NF-κB, IL-6 and TNF-α in LPS-mediated RAW 264.7 cells and markedly suppressed the protein expression of iNOS, NF-κB/p65, and COX-2. Dammarane glucoside 2 exhibited the strongest α-glucosidase inhibitory and anti-inflammatory activities. In addition, the structure-activity relationships (SARs) of the dammarane saponins were investigated. In summary, C. paliurus leaves showed marked α-glucosidase inhibitory and anti-inflammatory activities, and dammarane saponins are responsible for regulating α-glucosidase, inflammatory mediators, and mRNA and the protein expression of proinflammatory cytokines, which could be meaningful for discovering new antidiabetic agents.

Potential Role of Natural Plant Medicine Cyclocarya paliurus in the Treatment of Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) is a common chronic metabolic disease that has become increasingly prevalent worldwide. It poses a serious threat to human health and places a considerable burden on global social medical work. To meet the increasing demand for T2DM treatment, research on hypoglycemic drugs is rapidly developing. Cyclocarya paliurus (Batal.) Iljinskaja is a medicinal plant that grows in China. The leaves of C. paliurus contain polysaccharides, triterpenoids, and other chemical components, which have numerous health benefits. Therefore, the use of this plant has attracted extensive attention in the medical community. Over the past few decades, contemporary pharmacological studies on C. paliurus extracts have revealed that it has abundant biological activities. Multiple in vitro and in vivo experiments have shown that C. paliurus extracts are safe and can play a therapeutic role in T2DM through anti-inflammatory and antioxidation activities, and intestinal flora regulation. Its efficacy is closely related to many factors, such as extraction, separation, purification, and modification. Based on summarizing the existing extraction methods, this article further reviews the potential mechanism of C. paliurus extracts in T2DM treatment, and we aimed to provide a reference for future research on natural plant medicine for the prevention and treatment of T2DM and its related complications.

Effects of Cyclocarya paliurus Aqueous and Ethanol Extracts on Glucolipid Metabolism and the Underlying Mechanisms: A Meta-Analysis and Systematic Review

Background and Aims:Cyclocarya paliurus (CP) has been used as an herbal tea to treat diabetes mellitus and obesity for hundreds of years. Previous research suggests that CP specifically restores glucolipid metabolic homeostasis, and the two most studied preparations are aqueous and ethanol extracts. In order to verify the effect of CP on glucolipid metabolism in animal models with metabolic syndrome, a meta-analysis was performed, and the active components and underlying mechanisms were systematically reviewed.

Methods: Four databases: PubMed, Web of Science, Embase, and Cochrane Library were searched to identify potential literature. Data of blood glucose (BG) level, area under curve (AUC) of oral glucose tolerance test (OGTT), total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL), and low-density lipoprotein (LDL) levels were extracted as indicators of the assessment of CP's effects. Follow-up analyses including subgroup analysis, meta-regressions, and publication bias were also conducted.

Results: A total of 96 papers were identified from the databases and 11 papers including 31 data reports were involved in the meta-analysis. CP had a positive effect in down-regulating BG, AUC of OGTT, TC, TG, and LDL, and up-regulating HDL (P < 0.001, 95% confidence interval of standard mean difference did not incorporate the null value 0).

Conclusion: CP showed definite activity of regulating glucolipid metabolism in animal models, and it exerted its function through multiple mechanisms including but not limited to: (1) improving insulin resistance; (2) protecting pancreatic β cells; (3) decreasing inflammatory infiltration; and (4) anti-oxidative stress.