An extract of Artemisia dracunculus L. inhibits ubiquitin-proteasome activity and preserves skeletal muscle mass in a murine model of diabetes

A Mechanistic Review on Therapeutic Potential of Medicinal Plants and their Pharmacologically Active Molecules for Targeting Metabolic Syndrome

Metabolic syndrome (MetS) therapy with phytochemicals is an emerging field of study with therapeutic potential. Obesity, insulin resistance, high blood pressure, and abnormal lipid profiles are all components of metabolic syndrome, which is a major public health concern across the world. New research highlights the promise of phytochemicals found in foods, including fruits, vegetables, herbs, and spices, as a sustainable and innovative method of treating this illness. Anti-inflammatory, antioxidant, and insulin-sensitizing qualities are just a few of the many positive impacts shown by bioactive substances. Collectively, they alleviate the hallmark symptoms of metabolic syndrome by modulating critical metabolic pathways, boosting insulin sensitivity, decreasing oxidative stress, and calming chronic low-grade inflammation. In addition, phytochemicals provide a multimodal strategy by targeting not only adipose tissue but also the liver, skeletal muscle, and vascular endothelium, all of which have a role in the pathogenesis of MetS. Increasing evidence suggests that these natural chemicals may be useful in controlling metabolic syndrome as a complementary treatment to standard medication or lifestyle changes. This review article emphasizes the therapeutic potential of phytochemicals, illuminating their varied modes of action and their ability to alleviate the interconnected causes of metabolic syndrome. Phytochemical-based interventions show promise as a novel and sustainable approach to combating the rising global burden of metabolic syndrome, with the ultimate goal of bettering public health and quality of life.

Extract of Artemisia dracunculus L. Modulates Osteoblast Proliferation and Mineralization

Thiazolidinediones (TZD) significantly improve insulin sensitivity via action on adipocytes. Unfortunately, TZDs also degrade bone by inhibiting osteoblasts. An extract of Artemisia dracunculus L., termed PMI5011, improves blood glucose and insulin sensitivity via skeletal muscle, rather than fat, and may therefore spare bone. Here, we examine the effects of PMI5011 and an identified active compound within PMI5011 (2',4'-dihydroxy-4-methoxydihydrochalcone, DMC-2) on pre-osteoblasts. We hypothesized that PMI5011 and DMC-2 will not inhibit osteogenesis. To test our hypothesis, MC3T3-E1 cells were induced in osteogenic media with and without PMI5011 or DMC-2. Cell lysates were probed for osteogenic gene expression and protein content and were stained for osteogenic endpoints. Neither compound had an effect on early stain outcomes for alkaline phosphatase or collagen. Contrary to our hypothesis, PMI5011 at 30 µg/mL significantly increases osteogenic gene expression as early as day 1. Further, osteogenic proteins and cell culture mineralization trend higher for PMI5011-treated wells. Treatment with DMC-2 at 1 µg/mL similarly increased osteogenic gene expression and significantly increased mineralization, although protein content did not trend higher. Our data suggest that PMI5011 and DMC-2 have the potential to promote bone health via improved osteoblast maturation and activity.

Artemisia dracunculus L. Ethanolic Extract and an Isolated Component, DMC2, Ameliorate Inflammatory Signaling in Pancreatic β-Cells via Inhibition of p38 MAPK

Non-resolving pancreatic islet inflammation is widely viewed as a contributor to decreases in β-cell mass and function that occur in both Type 1 and Type 2 diabetes. Therefore, strategies aimed at reducing or eliminating pathological inflammation would be useful to protect islet β-cells. Herein, we described the use of 2′,4′-dihydroxy-4-methoxydihydrochalcone (DMC2), a bioactive molecule isolated from an ethanolic extract of Artemisia dracunculus L., as a novel anti-inflammatory agent. The ethanolic extract, termed PMI 5011, reduced IL-1β-mediated NF-κB activity. DMC2 retained this ability, indicating this compound as the likely source of anti-inflammatory activity within the overall PMI 5011 extract. We further examined NF-κB activity using promoter-luciferase reporter constructs, Western blots, mRNA abundance, and protein secretion. Specifically, we found that PMI 5011 and DMC2 each reduced the ability of IL-1β to promote increases in the expression of the Ccl2 and Ccl20 genes. These genes encode proteins that promote immune cell recruitment and are secreted by β-cells in response to IL-1β. Phosphorylation of IκBα and the p65 subunit of NF-κB were not reduced by either PMI 5011 or DMC2; however, phosphorylation of p38 MAPK was blunted in the presence of DMC2. Finally, we observed that while PMI 5011 impaired glucose-stimulated insulin secretion, insulin output was preserved in the presence of DMC2. In conclusion, PMI 5011 and DMC2 reduced inflammation, but only DMC2 did so with the preservation of glucose-stimulated insulin secretion.

Natural compounds in the regulation of proteostatic pathways: An invincible artillery against stress, ageing, and diseases

Cells have different sets of molecules for performing an array of physiological functions. Nucleic acids have stored and carried the information throughout evolution, whereas proteins have been attributed to performing most of the cellular functions. To perform these functions, proteins need to have a unique conformation and a definite lifespan. These attributes are achieved by a highly coordinated protein quality control (PQC) system comprising chaperones to fold the proteins in a proper three-dimensional structure, ubiquitin-proteasome system for selective degradation of proteins, and autophagy for bulk clearance of cell debris. Many kinds of stresses and perturbations may lead to the weakening of these protective cellular machinery, leading to the unfolding and aggregation of cellular proteins and the occurrence of numerous pathological conditions. However, modulating the expression and functional efficiency of molecular chaperones, E3 ubiquitin ligases, and autophagic proteins may diminish cellular proteotoxic load and mitigate various pathological effects. Natural medicine and small molecule-based therapies have been well-documented for their effectiveness in modulating these pathways and reestablishing the lost proteostasis inside the cells to combat disease conditions. The present article summarizes various similar reports and highlights the importance of the molecules obtained from natural sources in disease therapeutics.

Possible Synergistic Antidiabetic Effects of Quantified Artemisia judaica Extract and Glyburide in Streptozotocin-Induced Diabetic Rats via Restoration of PPAR-α mRNA Expression

Simple Summary

A considerable number of diabetic patients are in favour of using oral antidiabetic drugs in combination with certain herbs instead of using oral antidiabetic drugs alone. Artemisia judaica (AJ) is one of the herbs documented to have antidiabetic effects. This study examined the effect of using combination of A. judaica extract (AJE) and the oral hypoglycemic drug glyburide (GLB, 5 mg/kg) on diabetic rats. Fasting blood glucose (FBG), insulin levels, glycated hemoglobin (HbA1c) percentage, serum lipid profile, and oxidative stress biomarkers were estimated. The histopathological examination of the pancreas and the immunohistochemical analysis of anti-insulin, anti-glucagon, and anti-somatostatin protein expressions were also performed. The analysis of the hepatic mRNA expression of peroxisome proliferator-activated receptor α (PPAR-α) and nuclear factor erythroid 2-related factor-2 (Nrf2) genes was performed using quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Combination of GLB and 500 mg/kg of AJE highly improved FBG, insulin levels, HbA1c, and lipid profile in blood when compared with GLB monotherapy. Furthermore, GLB plus 500 mg/kg of AJE combination was the most successful in restoring insulin content in the β-cells and diminished the levels of glucagon and somatostatin of the α- and δ-endocrine cells in the pancreatic islets, restoring PPAR-α and Nrf2 mRNA expression in the liver. In conclusion, these data indicate that GLB plus 500 mg/kg of AJE combination gives greater glycemic improvement than GLB monotherapy.

Abstract

Several members of the genus Artemisia are used in both Western and African traditional medicine for the control of diabetes. A considerable number of diabetic patients switch to using oral antidiabetic drugs in combination with certain herbs instead of using oral antidiabetic drugs alone. This study examined the effect of Artemisia judaica extract (AJE) on the antidiabetic activity of glyburide (GLB) in streptozotocin (STZ)-induced diabetes. Forty-two male Wistar rats were divided into seven equal groups. Normal rats of the first group were treated with the vehicle. The diabetic rats in the second–fifth groups received vehicle, GLB (5 mg/kg), AJE low dose (250 mg/kg), and AJE high dose (500 mg/kg), respectively. Groups sixth–seventh were treated with combinations of GLB plus the lower dose of AJE and GLB plus the higher dose of AJE, respectively. All administrations were done orally for eight weeks. Fasting blood glucose (FBG) and insulin levels, glycated hemoglobin (HbA1c) percentage, serum lipid profile, and biomarkers of oxidative stress were estimated. The histopathological examination of the pancreas and the immunohistochemical analysis of anti-insulin, anti-glucagon, and anti-somatostatin protein expressions were also performed. The analysis of the hepatic mRNA expression of PPAR-α and Nrf2 genes were performed using quantitative RT-PCR. All treatments significantly lowered FBG levels when compared with the STZ-control group with the highest percentage reduction exhibited by the GLB plus AJE high dose combination. This combination highly improved insulin levels, HbA1c, and lipid profile in blood of diabetic rats compared to GLB monotherapy. In addition, all medicaments restored insulin content in the β-cells and diminished the levels of glucagon and somatostatin of the α- and δ-endocrine cells in the pancreatic islets. Furthermore, the GLB plus AJE high dose combination was the most successful in restoring PPAR-α and Nrf2 mRNA expression in the liver. In conclusion, these data indicate that the GLB plus AJE high dose combination gives greater glycemic improvement in male Wistar rats than GLB monotherapy.

Characterization of PMI-5011 on the Regulation of Deubiquitinating Enzyme Activity in Multiple Myeloma Cell Extracts

Deubiquitinating enzyme (DUB)-targeted therapeutics have shown promise in recent years as alternative cancer therapeutics, especially when coupled with proteasome-based inhibitors. While a majority of DUB-based therapeutics function by inhibiting DUB enzymes, studies show that positive regulation of these enzymes can stabilize levels of protein degradation. Unfortunately, there are currently no clinically available therapeutics for this purpose. The goal of this work was to understand the effect of a botanical extract from Artemisia dracunculus L called PMI-5011 on DUB activity in cancer cells. Through a series of kinetic analyses and mathematical modeling, it was found that PMI-5011 positively regulated DUB activity in two model multiple myeloma cells line (OPM2 and MM.1S). This suggests that PMI-5011 interacts with the active domains of DUBs to enhance their activity directly or indirectly, without apparently affecting cellular viability. Similar kinetic profiles of DUB activity were observed with three bioactive compounds in PMI-5011 (DMC-1, DMC-2, davidigenin). Interestingly, a differential cell line-independent trend was observed at higher concentrations which suggested variances in inherent gene expressions of UCHL1, UCHL5, USP7, USP15, USP14, and Rpn11 in OPM2 and MM.1S cell lines. These findings highlight the therapeutic potential of PMI-5011 and its selected bioactive compounds in cancer.

Imoxin prevents dexamethasone-induced promotion of muscle-specific E3 ubiquitin ligases and stimulates anabolic signaling in C2C12 myotubes

Muscle atrophy is the loss of skeletal muscle mass during several pathological conditions such as long-term fasting, aging, cancer, diabetes, sepsis and immune disorders. Glucocorticoids are known to trigger skeletal muscle atrophy. Dexamethasone (DEX), a synthetic glucocorticoid, induces skeletal muscle atrophy by suppression of protein synthesis and promotion of protein degradation. The double-stranded RNA (dsRNA)-activated protein kinase R (PKR) plays a significant role in mediating lipopolysaccharide-induced inflammation. However, pathological roles of PKR in muscle atrophy are not fully understood. The current study aimed to investigate the effect of imoxin, a PKR inhibitor, on DEX-induced muscle atrophy in C2C12 myotubes. Myotubes were incubated with imoxin at different concentrations with or without 5 μM DEX for 24 h. In the current study, imoxin treatment significantly reduced protein levels of MuRF1 and MAFbx induced by DEX by 88 ± 2% and MAFbx by 99 ± 0%, respectively. Moreover, 5 μM imoxin treatment reduced protein ubiquitination by 42 ± 4% and protein content of nuclear FoxO3α (77 ± 4%) in presence of DEX. Furthermore, 5 μM imoxin treatment stimulated Akt phosphorylation (195 ± 5%), mTOR phosphorylation (171 ± 21 %) and p70S6K1 phosphorylation (314 ± 31 %) under DEX-treated condition even though DEX treatment did not suppressed Akt/mTOR/p70S6K1 axis. These findings suggest that imoxin may protect against DEX-induced skeletal muscle atrophy by alleviating muscle specific E3 ubiquitin ligases and imoxin alone may promote protein synthesis via Akt/mTOR/S6K1 axis in muscle cells.

The DESIGNER Approach Helps Decipher the Hypoglycemic Bioactive Principles of Artemisia dracunculus (Russian Tarragon)

Complementing classical drug discovery, phytochemicals act on multiple pharmacological targets, especially in botanical extracts, where they form complex bioactive mixtures. The reductionist approach used in bioactivity-guided fractionation to identify single bioactive phytochemicals is inadequate for capturing the full therapeutic potential of the (bio)chemical interactions present in such complex mixtures. This study used a DESIGNER (Deplete and Enrich Select Ingredients to Generate Normalized Extract Resources) approach to selectively remove the known bioactives, 4'-O-methyldavidigenin (1; 4,2'-dihydroxy-4'-methoxydihydrochalcone, syn. DMC-1) and its isomer 4-O-methyldavidigenin (2; syn. DMC-2), from the mixture of phytochemicals in an ethanol extract from Artemisia dracunculus to determine to what degree the more abundant 2 accounts for the established antidiabetic effect of the A. dracunculus extract. Using an otherwise chemically intact "knock-out extract" depleted in 2 and its regioisomer, 1, in vitro and in vivo outcomes confirmed that 2 (and likely 1) acts as major bioactive(s) that enhance(s) insulin signaling in skeletal muscle, but also revealed that 2 does not account for the breadth of detectable biological activity of the extract. This is the first report of generating, at a sufficiently large preparative scale, a "knock-out extract" used as a pharmacological tool for in vitro and in vivo studies to dissect the biological impact of a designated bioactive in a complex phytochemical mixture.

An Extract of Artemisia dracunculus L. Promotes Psychological Resilience in a Mouse Model of Depression

Stress-induced peripheral inflammation contributes to depression-like behaviors in both human and experimental models. PMI 5011, a botanical extract of Artemisia dracunculus L., was previously shown to have multiple bioactivities, including anti-inflammatory activity. In this work, using a repeated social defeat stress (RSDS) model of depression, we demonstrate that oral administration of the botanical extract PMI 5011 promotes resilience to RSDS-mediated depression-like phenotypes. We also show that the behavioral improvements are associated with attenuation of stress-mediated induction of inflammatory cytokines in the periphery and alteration of synaptic plasticity in the nucleus accumbens (NAc). Our studies provide experimental evidence that botanical extracts such as PMI 5011, which target pathological mechanisms (i.e., peripheral inflammation) not addressed by currently available antidepressants, could be further developed as novel therapeutics for the treatment of stress disorders and anxiety in humans.

The role of E3 ubiquitin-ligases MuRF-1 and MAFbx in loss of skeletal muscle mass

The ubiquitin-proteasome system (UPS) is the main regulatory mechanism of protein degradation in skeletal muscle. The ubiquitin-ligase enzymes (E3s) have a central role in determining the selectivity and specificity of the UPS. Since their identification in 2001, the muscle specific E3s, muscle RING finger-1 (MuRF-1) and muscle atrophy F-box (MAFbx), have been shown to be implicated in the regulation of skeletal muscle atrophy in various pathological and physiological conditions. This review aims to explore the involvement of MuRF-1 and MAFbx in catabolism of skeletal muscle during various pathologies, such as cancer cachexia, sarcopenia of aging, chronic kidney disease (CKD), diabetes, and chronic obstructive pulmonary disease (COPD). In addition, the effects of various lifestyle and modifiable factors (e.g. nutrition, exercise, cigarette smoking, and alcohol) on MuRF-1 and MAFbx regulation will be discussed. Finally, evidence of potential strategies to protect against skeletal muscle wasting through inhibition of MuRF-1 and MAFbx expression will be explored.

Identification of Eupatilin from Artemisia argyi as a Selective PPARα Agonist Using Affinity Selection Ultrafiltration LC-MS

Peroxisome proliferator-activated receptors (PPARs) are key nuclear receptors and therapeutic targets for the treatment of metabolic diseases through the regulation of insulin resistance, diabetes, and dyslipidemia. Although a few drugs that target PPARs have been approved, more diverse and novel PPAR ligands are necessary to improve the safety and efficacy of available drugs. To expedite the search for new natural agonists of PPARs, we developed a screening assay based on ultrafiltration liquid chromatography-mass spectrometry (LC-MS) that is compatible with complex samples such as dietary foods or botanical extracts. The known PPARα and/or PPARγ ligands resveratrol and rosiglitazone were used as positive controls to validate the developed method. When applied to the screening of an Artemisia argyi extract, eupatilin was identified as a selective PPARα ligand. A PPAR competitive binding assay based on FRET detection also confirmed eupatilin as a selective PPARα agonist exhibiting a binding affinity of 1.18 μM (IC50). Furthermore, eupatilin activation of the transcriptional activity of PPARα was confirmed using a cell-based transactivation assay. Thus, ultrafiltration LC-MS is a suitable assay for the identification of PPAR ligands in complex matrixes such as extracts of dietary foods and botanicals.

Artemisia dracunculus L. extract ameliorates insulin sensitivity by attenuating inflammatory signalling in human skeletal muscle culture

AIMS

Bioactives of Artemisia dracunculus L. (termed PMI 5011) have been shown to improve insulin action by increasing insulin signalling in skeletal muscle. However, it was not known if PMI 5011's effects are retained during an inflammatory condition. We examined the attenuation of insulin action and whether PMI 5011 enhances insulin signalling in the inflammatory environment with elevated cytokines.

METHODS

Muscle cell cultures derived from lean, overweight and diabetic-obese subjects were used. Expression of pro-inflammatory genes and inflammatory response of human myotubes were evaluated by real-time polymerase chain reaction (RT-PCR). Insulin signalling and activation of inflammatory pathways in human myotubes were evaluated by multiplex protein assays.

RESULTS

We found increased gene expression of monocyte chemoattractant protein 1 (MCP1) and TNFα (tumour necrosis factor alpha), and basal activity of the NFkB (nuclear factor kappa-light-chain-enhancer of activated B cells) pathway in myotubes derived from diabetic-obese subjects as compared with myotubes derived from normal-lean subjects. In line with this, basal Akt phosphorylation (Ser473) was significantly higher, while insulin-stimulated phosphorylation of Akt (Ser473) was lower in myotubes from normal-overweight and diabetic-obese subjects compared with normal-lean subjects. PMI 5011 treatment reduced basal phosphorylation of Akt and enhanced insulin-stimulated phosphorylation of Akt in the presence of cytokines in human myotubes. PMI 5011 treatment led to an inhibition of cytokine-induced activation of inflammatory signalling pathways such as Erk1/2 and IkBα (nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha)-NFkB and moreover, NFkB target gene expression, possibly by preventing further propagation of the inflammatory response within muscle tissue.

CONCLUSIONS

PMI 5011 improved insulin sensitivity in diabetic-obese myotubes to the level of normal-lean myotubes despite the presence of pro-inflammatory cytokines.

An ethanolic extract of Artemisia dracunculus L. regulates gene expression of ubiquitin-proteasome system enzymes in skeletal muscle: potential role in the treatment of sarcopenic obesity

OBJECTIVE

Obesity is linked to insulin resistance, a primary component of metabolic syndrome and type 2 diabetes. The problem of obesity-related insulin resistance is compounded when age-related skeletal muscle loss, called sarcopenia, occurs with obesity. Skeletal muscle loss results from elevated levels of protein degradation and prevention of obesity-related sarcopenic muscle loss will depend on strategies that target pathways involved in protein degradation. An extract from Artemisia dracunculus, termed PMI 5011, improves insulin signaling and increases skeletal muscle myofiber size in a rodent model of obesity-related insulin resistance. The aim of this study was to examine the effect of PMI 5011 on the ubiquitin-proteasome system, a central regulator of muscle protein degradation.

METHODS

Gastrocnemius and vastus lateralis skeletal muscle was obtained from KK-A(y) obese diabetic mice fed a control or 1% (w/w) PMI 5011-supplemented diet. Regulation of genes encoding enzymes of the ubiquitin-proteasome system was determined using real-time quantitative reverse transcriptase polymerase chain reaction.

RESULTS

Although MuRF-1 ubiquitin ligase gene expression is consistently down-regulated in skeletal muscle, atrogin-1, Fbxo40, and Traf6 expression is differentially regulated by PMI 5011. Genes encoding other enzymes of the ubiquitin-proteasome system ranging from ubiquitin to ubiquitin-specific proteases are also regulated by PMI 5011. Additionally, expression of the gene encoding the microtubule-associated protein-1 light chain 3 (LC3), a ubiquitin-like protein pivotal to autophagy-mediated protein degradation, is down-regulated by PMI 5011 in the vastus lateralis.

CONCLUSION

PMI 5011 alters the gene expression of ubiquitin-proteasome system enzymes that are essential regulators of skeletal muscle mass. This suggests that PMI 5011 has therapeutic potential in the treatment of obesity-linked sarcopenia by regulating ubiquitin-proteasome-mediated protein degradation.

Artemisia supplementation differentially affects the mucosal and luminal ileal microbiota of diet-induced obese mice

OBJECTIVE

The gut microbiome has been implicated in obesity and metabolic syndrome; however, most studies have focused on fecal or colonic samples. Several species of Artemisia have been reported to ameliorate insulin signaling both in vitro and in vivo. The aim of this study was to characterize the mucosal and luminal bacterial populations in the terminal ileum with or without supplementation with Artemisia extracts.

METHODS

Following 4 wk of supplementation with different Artemisia extracts (PMI 5011, Santa or Scopa), diet-induced obese mice were sacrificed and luminal and mucosal samples of terminal ileum were used to evaluate microbial community composition by pyrosequencing of 16 S rDNA hypervariable regions.

RESULTS

Significant differences in community structure and membership were observed between luminal and mucosal samples, irrespective of diet group. All Artemisia extracts increased the Bacteroidetes to Firmicutes ratio in mucosal samples. This effect was not observed in the luminal compartment. There was high interindividual variability in the phylogenetic assessments of the ileal microbiota, limiting the statistical power of this pilot investigation.

CONCLUSIONS

Marked differences in bacterial communities exist depending on the biogeographic compartment in the terminal ileum. Future studies testing the effects of Artemisia or other botanical supplements require larger sample sizes for adequate statistical power.

Liraglutide Exerts Antidiabetic Effect via PTP1B and PI3K/Akt2 Signaling Pathway in Skeletal Muscle of KKAy Mice

Background. Liraglutide (a glucagon-like peptide 1 analog) was used for the treatment of type 2 diabetes (T2DM) which could produce glucose-dependent insulin secretion. Aim. The aim was to investigate whether liraglutide could improve myofibril and mitochondria injury in skeletal muscle and the mechanisms in diabetic KKAy mice. Method. We divided the male KKAy mice into 2 groups: liraglutide group (250 μg/kg/day liraglutide subcutaneous injection) and model group; meanwhile, the male C57BL/6J mice were considered as the control. After 6 weeks, the ultrastructure of skeletal muscle was observed by electron microscope. The gene expressions of protein tyrosine phosphatase 1B (PTP1B), phosphatidylinositol 3-kinase (PI3K), and glucose transporter type 4 (GLUT4) were determined by real-time PCR. The protein levels of the above molecules and phospho-Akt2 (p-Akt2) were measured by Western blot. Results. Liraglutide significantly ameliorated the injury of mitochondria by increasing the number (+441%) and the area (+113%) of mitochondria and mitochondrial area/100 µm(2) (+396%) in skeletal muscle of KKAy mice. The results of real-time PCR and Western blot showed that liraglutide downregulated PTP1B while it upregulated PI3K and GLUT4 (P < 0.01). The protein level of p-Akt2/Akt2 was also increased (P < 0.01). Conclusion. These results revealed that liraglutide could improve myofibril and mitochondria injury in skeletal muscle against T2DM via PTP1B and PI3K/Akt2 signaling pathway.