Akebia saponin D alleviates hepatic steatosis through BNip3 induced mitophagy

Combined effects of vitamin D3 and dioxopiperidinamide derivative on lipid homeostasis, inflammatory pathways, and redox imbalance in non-alcoholic fatty liver disease in vivo zebrafish model

Liver damage and metabolic dysfunctions, the defining features of non-alcoholic fatty liver disease (NAFLD), are marked by inflammation, oxidative stress, and excessive hepatic fat accumulation. The current therapeutic approaches for NAFLD are limited, necessitating exploring novel treatment strategies. Dioxopiperidinamide derivatives, particularly DOPA-33, have shown effective anti-inflammatory and antioxidant properties, potentially offering therapeutic benefits against NAFLD. This study investigated the combined potential of vitamin D3 (Vit D3) and DOPA-33 in treating NAFLD. The network pharmacology analysis identified key NAFLD targets modulated by Vit D3 and DOPA-33, emphasizing their potential mechanisms of action. In NAFLD-induced zebrafish models, Vit D3 and DOPA-33 significantly reduced hepatic lipid accumulation, oxidative stress, and apoptosis, demonstrating superior efficacy over individual treatments. The treatment also lowered reactive oxygen species (ROS) levels, decreased liver damage, and enhanced antioxidant defense mechanisms. Moreover, behavioral analyses showed improved locomotion and reduced weight gain in treated zebrafish. Biochemical analyses revealed lower triglycerides (TG) and glucose levels with improved oxidative markers. Furthermore, histological analyses indicated reduced hepatic steatosis and inflammation, with decreased expression of lipogenesis-related genes and inflammatory mediators. Finally, high-performance liquid chromatography (HPLC) confirmed a significant reduction in hepatic cholesterol levels, indicating the effectiveness of the combination therapy in addressing key NAFLD-related dyslipidemias. These findings suggest that Vit D3 + DOPA-33 targets pathways involved in lipid metabolism, inflammation, and oxidative stress by offering a promising therapeutic approach for NAFLD.

Sesamin alleviates lipid accumulation induced by oleic acid via PINK1/Parkin-mediated mitophagy in HepG2 cells

Sesamin, a special compound present in sesame and sesame oil, has been reported a role in regulating lipid metabolism, while the underlying mechanisms remain unclear. Autophagy has been reported associated with lipid metabolism and regarded as a key modulator in liver steatosis. The present work aimed to investigate whether sesamin could exert its protective effects against lipid accumulation via modulating autophagy in HepG2 cells stimulated with oleic acid (OA). Cell viability was evaluated using the CCK-8 method, and triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein, cholesterol (LDL-C), alanine aminotransferase (ALT), along with aspartate aminotransferase (AST) were assessed by oil red O staining, transmission electron microscopy (TEM), and biochemical kits to investigate the lipid-lowering effects of sesamin. Differentially expressed genes were screened by RNA sequencing and validated using real-time quantitative PCR and Western blot. Autophagy and mitophagy related molecules were analyzed employing TEM, Western blot, and immunofluorescence. The data shows that in HepG2 cells stimulated by OA, sesamin reduces levels of TG, TC, LDL-C, ALT, and AST while elevating HDL-C, alleviates the lipid accumulation and improves fatty acid metabolism through modulating the levels of fat metabolism related genes including PCSK9, FABP1, CD36, and SOX4. Sesamin restores the suppressed autophagy in HepG2 cells caused by OA, which could be blocked by autophagy inhibitors. This indicates that sesamin improves fatty acid metabolism by enhancing autophagy levels, thereby mitigating the intracellular lipid accumulation. Furthermore, sesamin significantly enhances the mitophagy and improves mitochondrial homeostasis via activating the PINK/Parkin pathway. These data suggest that sesamin alleviates the excessive lipid accumulation in HepG2 caused by OA by restoring the impaired mitophagy via the PINK1/Parkin pathway, probably playing a preventive or therapeutic role in hepatic steatosis.

Saponins as therapeutic candidates for atherosclerosis

Drug development for atherosclerosis, the underlying pathological state of ischemic cardiovascular diseases, has posed a longstanding challenge. Saponins, classified as steroid or triterpenoid glycosides, have shown promising therapeutic potential in the treatment of atherosclerosis. Through an exhaustive examination of scientific literature spanning from May 2013 to May 2023, we identified 82 references evaluating 37 types of saponins in terms of their prospective impacts on atherosclerosis. These studies suggest that saponins have the potential to ameliorate atherosclerosis by regulating lipid metabolism, inhibiting inflammation, suppressing apoptosis, reducing oxidative stress, and modulating smooth muscle cell proliferation and migration, as well as regulating gut microbiota, autophagy, endothelial senescence, and angiogenesis. Notably, ginsenosides exhibit significant potential and manifest essential pharmacological attributes, including lipid-lowering, anti-inflammatory, anti-apoptotic, and anti-oxidative stress effects. This review provides a comprehensive examination of the pharmacological attributes of saponins in atherosclerosis, with particular emphasis on their role in the regulation of lipid metabolism regulation and anti-inflammatory effects. Thus, saponins may warrant further investigation as a potential therapy for atherosclerosis. However, due to various reasons such as low oral bioavailability, the clinical application of saponins in the treatment of atherosclerosis still needs further exploration.

Akebia saponin D attenuates allergic airway inflammation through AMPK activation

Akebia saponin D (ASD) is a bioactive triterpenoid saponin extracted from Dipsacus asper Wall. ex DC.. This study aimed to investigate the effects of ASD on allergic airway inflammation. Human lung epithelial BEAS-2B cells and bone marrow-derived mast cells (BMMCs) were pretreated with ASD (50, 100 and 200 μΜ) and AMPK activator 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR) (1 mM), and then stimulated with lipopolysaccharide (LPS) or IL-33. Pretreatment with ASD and AICAR significantly inhibited TNF-α and IL-6 production from BEAS-2B cells, and IL-13 production from BMMCs. Moreover, pretreatment with ASD and AICAR significantly increased p-AMPK expression in BEAS-2B cells. Inhibition of AMPK by siRNA and compound C partly abrogated the suppression effect of ASD on TNF-α, IL-6, and IL-13 production. Asthma murine model was induced by ovalbumin (OVA) challenge and treated with ASD (150 and 300 mg/kg) or AICAR (100 mg/kg). Infiltration of eosinophils, neutrophils, monocytes, and lymphocytes, and production of TNF-α, IL-6, IL-4, and IL-13 were attenuated in ASD and AICAR treated mice. Lung histopathological changes were also ameliorated after ASD and AICAR treatment. Additionally, it showed that treatment with ASD and AICAR increased p-AMPK expression in the lung tissues. In conclusion, ASD exhibited protective effects on allergic airway inflammation through the induction of AMPK activation.

Mechanisms and therapeutic implications of selective autophagy in nonalcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease worldwide, whereas there is no approved drug therapy due to its complexity. Studies are emerging to discuss the role of selective autophagy in the pathogenesis of NAFLD, because the specificity among the features of selective autophagy makes it a crucial process in mitigating hepatocyte damage caused by aberrant accumulation of dysfunctional organelles, for which no other pathway can compensate.

AIM OF REVIEW

This review aims to summarize the types, functions, and dynamics of selective autophagy that are of particular importance in the initiation and progression of NAFLD. And on this basis, the review outlines the therapeutic strategies against NAFLD, in particular the medications and potential natural products that can modulate selective autophagy in the pathogenesis of this disease.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The critical roles of lipophagy and mitophagy in the pathogenesis of NAFLD are well established, while reticulophagy and pexophagy are still being identified in this disease due to the insufficient understanding of their molecular details. As gradual blockage of autophagic flux reveals the complexity of NAFLD, studies unraveling the underlying mechanisms have made it possible to successfully treat NAFLD with multiple pharmacological compounds that target associated pathways. Overall, it is convinced that the continued research into selective autophagy occurring in NAFLD will further enhance the understanding of the pathogenesis and uncover novel therapeutic targets.

Akebia saponin D from Dipsacus asper wall. Ex C.B. Clarke ameliorates skeletal muscle insulin resistance through activation of IGF1R/AMPK signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Dipsacus asper Wall. Ex C.B. Clarke (DA), a perennial herb, is one of the most commonly used herbs in Traditional Chinese Medicine for strengthening muscles and bones and regulating blood vessels. Akebia saponin D (ASD/AVI) is a triterpenoid saponin extracted from the root of DA, which has favorable pharmacological properties such as anti-osteoporosis, anti-apoptosis, liver protection and hypolipidemic.

AIM OF THE STUDY

To explore the underlying mechanisms and regulatory role of Akebia saponin D (ASD/AVI) on high-fat diet-induced insulin resistance in skeletal muscle.

MATERIALS AND METHODS

C2C12 cells were used to explore the best concentration in the skeletal muscle insulin resistance model in an in vitro experiment. The protective effect of AVI on insulin resistance and the corresponding signaling pathway were detected by glucose content measurement, quantitative PCR, and Western blot. A high-fat diet STZ-induced insulin resistance mice model was used to evaluate the protective function of AVI in vivo. After four weeks of treatment, ITT, OGTT, and treadmill tests were applied to examine insulin sensitivity and their serum and skeletal muscle tissues were collected for further analysis.

RESULTS

AVI effectively reduced body weight, blood glucose levels and calorie intake in insulin-resistant mice, and reduced lipid accumulation and in their muscle tissue. AVI also improved glucose uptake and insulin sensitivity in both in vivo and in vitro experiments. Following AVI administration, there was an increase in the expression of the AMPK signaling pathway. Our experiments further confirmed that AVI specifically targets the IGF1R, thereby more effectively regulating the insulin signaling pathway.

CONCLUSION

AVI improves type 2 diabetes-induced insulin resistance in skeletal muscle by activating the IGF1R-AMPK signaling pathway, promoting glucose uptake and energy metabolism in IR.

The emerging significance of mitochondrial targeted strategies in NAFLD treatment

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease worldwide, ranging from liver steatosis to nonalcoholic steatohepatitis, which ultimately progresses to fibrosis, cirrhosis, and hepatocellular carcinoma. Individuals with NAFLD have a higher risk of developing cardiovascular and extrahepatic cancers. Despite the great progress being made in understanding the pathogenesis and the introduction of new pharmacological targets for NAFLD, no drug or intervention has been accepted for its management. Recent evidence suggests that NAFLD may be a mitochondrial disease, as mitochondrial dysfunction is involved in the pathological processes that lead to NAFLD. In this review, we describe the recent advances in our understanding of the mechanisms associated with mitochondrial dysfunction in NAFLD progression. Moreover, we discuss recent advances in the efficacy of mitochondria-targeted compounds (e.g., Mito-Q, MitoVit-E, MitoTEMPO, SS-31, mitochondrial uncouplers, and mitochondrial pyruvate carrier inhibitors) for treating NAFLD. Furthermore, we present some medications currently being tested in clinical trials for NAFLD treatment, such as exercise, mesenchymal stem cells, bile acids and their analogs, and antidiabetic drugs, with a focus on their efficacy in improving mitochondrial function. Based on this evidence, further investigations into the development of mitochondria-based agents may provide new and promising alternatives for NAFLD management.

The mitophagy pathway and its implications in human diseases

Mitochondria are dynamic organelles with multiple functions. They participate in necrotic cell death and programmed apoptotic, and are crucial for cell metabolism and survival. Mitophagy serves as a cytoprotective mechanism to remove superfluous or dysfunctional mitochondria and maintain mitochondrial fine-tuning numbers to balance intracellular homeostasis. Growing evidences show that mitophagy, as an acute tissue stress response, plays an important role in maintaining the health of the mitochondrial network. Since the timely removal of abnormal mitochondria is essential for cell survival, cells have evolved a variety of mitophagy pathways to ensure that mitophagy can be activated in time under various environments. A better understanding of the mechanism of mitophagy in various diseases is crucial for the treatment of diseases and therapeutic target design. In this review, we summarize the molecular mechanisms of mitophagy-mediated mitochondrial elimination, how mitophagy maintains mitochondrial homeostasis at the system levels and organ, and what alterations in mitophagy are related to the development of diseases, including neurological, cardiovascular, pulmonary, hepatic, renal disease, etc., in recent advances. Finally, we summarize the potential clinical applications and outline the conditions for mitophagy regulators to enter clinical trials. Research advances in signaling transduction of mitophagy will have an important role in developing new therapeutic strategies for precision medicine.

Global trends in research of mitophagy in liver diseases over past two decades: A bibliometric analysis

Increasing evidence indicated that mitophagy might play a crucial role in the occurrence and progression of liver diseases. In order to enhance our understanding of the intricate relationship between mitophagy and liver diseases, a comprehensive bibliometric analysis of the existing literature in this field was conducted. This analysis aimed to identify key trends, potential areas of future research, and forecast the development of this specific field. We systematically searched the Web of Science Core Collection (WoSCC) for publications related to mitophagy in liver diseases from 2000 to 2022. We conducted the bibliometric analysis and data visualization through VOSviewer and CiteSpace. The analysis of publication growth revealed a substantial increase in articles published in this field over the past years, indicating mitophagy's growing interest and significance in liver diseases. China and USA emerged as the leading contributors in the number of papers, with 294 and 194 independent papers, respectively. Exploring the mechanism of mitophagy in the initiation and procession of liver diseases was the main content of studies in this field, and Parkin-independent mediated mitophagy has attracted much attention recently. "Lipid metabolism," "cell death," "liver fibrosis" and "oxidative stress" were the primary keywords clusters. Additionally, "nlrp3 inflammasome", "toxicity" and "nonalcoholic steatohepatitis" were emerging research hotspots in this area and have the potential to continue to be focal areas of investigation in the future. This study represents the first systematic bibliometric analysis of research on mitophagy in liver diseases conducted over the past 20 years. By providing an overview of the existing literature and identifying current research trends, this analysis sheds light on the critical areas of investigation and paves the way for future studies in this field.

Dipsacus and Scabiosa Species-The Source of Specialized Metabolites with High Biological Relevance: A Review

The genera Dipsacus L. and Scabiosa L. of the Caprifoliaceae family are widely distributed in Europe, Asia, and Africa. This work reviews the available literature on the phytochemical profiles, ethnomedicinal uses, and biological activities of the most popular species. These plants are rich sources of many valuable specialized metabolites with beneficial medicinal properties, such as triterpenoid derivatives, iridoids, phenolic acids, and flavonoids. They are also sources of essential oils. The genus Dipsacus has been used for centuries in Chinese and Korean folk medicines to treat bone (osteoporosis) and joint problems (rheumatic arthritis). The Korean Herbal Pharmacopoeia and Chinese Pharmacopoeia include Dipsaci radix, the dried roots of D. asperoides C.Y.Cheng & T.M.Ai. In addition, S. comosa Fisch. ex Roem & Schult. and S. tschiliiensis Grunning are used in traditional Mongolian medicine to treat liver diseases. The current scientific literature data indicate that these plants and their constituents have various biological properties, including inter alia antiarthritic, anti-neurodegenerative, anti-inflammatory, antioxidant, anticancer, and antimicrobial activities; they have also been found to strengthen tendon and bone tissue and protect the liver, heart, and kidney. The essential oils possess antibacterial, antifungal, and insecticidal properties. This paper reviews the key biological values of Dipsacus and Scabiosa species, as identified by in vitro and in vivo studies, and presents their potential pharmacological applications.

Roles of organelle-specific autophagy in hepatocytes in the development and treatment of non-alcoholic fatty liver disease

ABSTRACT

Non-alcoholic fatty liver disease (NAFLD) is a disorder of lipid metabolism. The lipotoxic intermediates of lipid metabolism cause mitochondrial dysfunction and endoplasmic reticulum stress. Organelle-specific autophagy is responsible for the removal of dysfunctional organelles to maintain intracellular homeostasis. Lipophagy contributes to lipid turnover by degrading lipid droplets. The level of autophagy changes during the course of NAFLD, and the activation of hepatocyte autophagy might represent a method of treating NAFLD.

Phytochemicals: Targeting Mitophagy to Treat Metabolic Disorders

Metabolic disorders include metabolic syndrome, obesity, type 2 diabetes mellitus, non-alcoholic fatty liver disease and cardiovascular diseases. Due to unhealthy lifestyles such as high-calorie diet, sedentary and physical inactivity, the prevalence of metabolic disorders poses a huge challenge to global human health, which is the leading cause of global human death. Mitochondrion is the major site of adenosine triphosphate synthesis, fatty acid β-oxidation and ROS production. Accumulating evidence suggests that mitochondrial dysfunction-related oxidative stress and inflammation is involved in the development of metabolic disorders. Mitophagy, a catabolic process, selectively degrades damaged or superfluous mitochondria to reverse mitochondrial dysfunction and preserve mitochondrial function. It is considered to be one of the major mechanisms responsible for mitochondrial quality control. Growing evidence shows that mitophagy can prevent and treat metabolic disorders through suppressing mitochondrial dysfunction-induced oxidative stress and inflammation. In the past decade, in order to expand the range of pharmaceutical options, more and more phytochemicals have been proven to have therapeutic effects on metabolic disorders. Many of these phytochemicals have been proved to activate mitophagy to ameliorate metabolic disorders. Given the ongoing epidemic of metabolic disorders, it is of great significance to explore the contribution and underlying mechanisms of mitophagy in metabolic disorders, and to understand the effects and molecular mechanisms of phytochemicals on the treatment of metabolic disorders. Here, we investigate the mechanism of mitochondrial dysfunction in metabolic disorders and discuss the potential of targeting mitophagy with phytochemicals for the treatment of metabolic disorders, with a view to providing a direction for finding phytochemicals that target mitophagy to prevent or treat metabolic disorders.

New Insights Into the Role of Autophagy in Liver Surgery in the Setting of Metabolic Syndrome and Related Diseases

Visceral obesity is an important component of metabolic syndrome, a cluster of diseases that also includes diabetes and insulin resistance. A combination of these metabolic disorders damages liver function, which manifests as non-alcoholic fatty liver disease (NAFLD). NAFLD is a common cause of abnormal liver function, and numerous studies have established the enormously deleterious role of hepatic steatosis in ischemia-reperfusion (I/R) injury that inevitably occurs in both liver resection and transplantation. Thus, steatotic livers exhibit a higher frequency of post-surgical complications after hepatectomy, and using liver grafts from donors with NAFLD is associated with an increased risk of post-surgical morbidity and mortality in the recipient. Diabetes, another MetS-related metabolic disorder, also worsens hepatic I/R injury, and similar to NAFLD, diabetes is associated with a poor prognosis after liver surgery. Due to the large increase in the prevalence of MetS, NAFLD, and diabetes, their association is frequent in the population and therefore, in patients requiring liver resection and in potential liver graft donors. This scenario requires advancement in therapies to improve postoperative results in patients suffering from metabolic diseases and undergoing liver surgery; and in this sense, the bases for designing therapeutic strategies are in-depth knowledge about the molecular signaling pathways underlying the effects of MetS-related diseases and I/R injury on liver tissue. A common denominator in all these diseases is autophagy. In fact, in the context of obesity, autophagy is profoundly diminished in hepatocytes and alters mitochondrial functions in the liver. In insulin resistance conditions, there is a suppression of autophagy in the liver, which is associated with the accumulation of lipids, being this is a risk factor for NAFLD. Also, oxidative stress occurring in hepatic I/R injury promotes autophagy. The present review aims to shed some light on the role of autophagy in livers undergoing surgery and also suffering from metabolic diseases, which may lead to the discovery of effective therapeutic targets that could be translated from laboratory to clinical practice, to improve postoperative results of liver surgeries when performed in the presence of one or more metabolic diseases.

Pharmacokinetics, Bioavailability, Excretion and Metabolism Studies of Akebia Saponin D in Rats: Causes of the Ultra-Low Oral Bioavailability and Metabolic Pathway

Background: Akebia saponin D (ASD) has a variety of biological activities and great medicinal potential, but its oral bioavailability is so low as to limit its development. Its pharmacokinetic profiles and excretion and metabolism in vivo have not been fully elucidated. This study was an attempt in this area.

Methods: A simple LC-MS/MS method to simultaneously quantify ASD and its metabolites M1∼M5 in rat plasma, feces, urine and bile was established with a negative ESI model using dexketoprofen as the internal standard. Meanwhile, the UPLC-HR/MS system was used to screen all possible metabolites in the urine, feces and bile of rats, as compared with blank samples collected before administration. Absolute quantitative analysis was for M0, M3, M4, and M5, while semi-quantitative analysis was for M1, M2, and Orbitrap data.

Results: The AUC_0-t values after intravenous administration of 10 mg/kg and intragastrical administration of 100 mg/kg ASD were 19.05 ± 8.64 and 0.047 ± 0.030 h*μg/ml respectively. The oral bioavailability was determined to be extremely low (0.025%) in rats. The exposure of M4 and M5 in the oral group was higher than that of M0 in the terminal phase of the plasma concentration time profile, and ASD was stable in the liver microsome incubation system of rats, but metabolism was relatively rapid during anaerobic incubation of intestinal contents of rats, suggesting that the low bioavailability of ASD might have been attributed to the poor gastrointestinal permeability and extensive pre-absorption degradation rather than to the potent first pass metabolism. This assertion was further verified by a series of intervention studies, where improvement of lipid solubility and intestinal permeability as well as inhibition of intestinal flora increased the relative bioavailability to different extents without being changed by P-gp inhibition. After intravenous administration, the cumulative excretion rates of ASD in the urine and bile were 14.79 ± 1.87%, and 21.76 ± 17.61% respectively, but only 0.011% in feces, suggesting that the urine and bile were the main excretion pathways and that there was a large amount of biotransformation in the gastrointestinal tract. Fifteen possible metabolites were observed in the urine, feces and bile. The main metabolites were ASD deglycosylation, demethylation, dehydroxylation, decarbonylation, decarboxylation, hydroxylation, hydroxymethylation, hydroxyethylation and hydrolysis.

Conclusion: The pharmacokinetics, bioavailability, metabolism and excretion of ASD in rats were systematically evaluated for the first time in this study. It has been confirmed that the ultra-low oral bioavailability is due to poor gastrointestinal permeability, extensive pre-absorption degradation and biotransformation. ASD after iv administration is not only excreted by the urine and bile, but possibly undergoes complex metabolic elimination.

Akebia saponin D ameliorates metabolic syndrome (MetS) via remodeling gut microbiota and attenuating intestinal barrier injury

Metabolic syndrome (MetS) is a complex, multifactorial disease which lead to an increased risk of cardiovascular disease, type 2 diabetes, and stroke. However, selective, and potent drugs for the treatment of MetS are still lacking. Previous studies have found that Akebia saponin D (ASD) has beneficial effects on metabolic diseases such as obesity, atherosclerosis, and non-alcoholic fatty liver disease (NAFLD). Therefore, our study was designed to determine the effect and mechanism of action of ASD against MetS in a high-fat diet (HFD) induced mouse model. ASD significantly decreased plasma lipid and insulin resistance in these mice, and a targeted approach using metabolomic analyses of plasma and feces indicated that glucose and lipids in these mice crossed the damaged intestinal barrier into circulation. Furthermore, ASD was able to increase lipid excretion and inhibit intestinal epithelial lipid absorption. Results for gut microbiota composition showed that ASD significantly reduced HFD-associated Alistipes, Prevotella, and enhanced the proportions of Butyricimonas, Ruminococcus, and Bifidobacterium. After 14 weeks of ASD/fecal microbiota transplantation (FMT) interventions the developed gut barrier dysfunction was restored. Additionally, RNA-seq revealed that ASD reduced the lipid-induced tight junction (TJ) damage in intestinal epithelial cells via down-regulation of the PPAR-γ-FABP4 pathway in vitro and that use of the PPAR-γ inhibitor (T0070907) was able to partially block the effects of ASD, indicating that the PPAR-γ/FABP4 pathway is a critical mediator involved in the improvement of MetS. Our results demonstrated that ASD not only modifies the gut microbiome but also ameliorates the HFD-induced gut barrier disruption via down-regulation of the PPAR-γ-FABP4 pathway. These findings suggest a promising, and novel therapeutic strategy for gut protection against MetS.

KCa3.1 Mediates Dysregulation of Mitochondrial Quality Control in Diabetic Kidney Disease

Mitochondrial dysfunction is implicated in the pathogenesis of diabetic kidney disease. Mitochondrial quality control is primarily mediated by mitochondrial turnover and repair through mitochondrial fission/fusion and mitophagy. We have previously shown that blockade of the calcium-activated potassium channel KCa3.1 ameliorates diabetic renal fibrosis. However, the mechanistic link between KCa3.1 and mitochondrial quality control in diabetic kidney disease is not yet known. Transforming growth factor β1 (TGF-β1) plays a central role in diabetic kidney disease. Recent studies indicate an emerging role of TGF-β1 in the regulation of mitochondrial function. However, the molecular mechanism mediating mitochondrial quality control in response to TGF-β1 remains limited. In this study, mitochondrial function was assessed in TGF-β1-exposed renal proximal tubular epithelial cells (HK2 cells) transfected with scrambled siRNA or KCa3.1 siRNA. In vivo, diabetes was induced in KCa3.1+/+ and KCa3.1−/− mice by low-dose streptozotocin (STZ) injection. Mitochondrial fission/fusion-related proteins and mitophagy markers, as well as BCL2 interacting protein 3 (BNIP3) (a mitophagy regulator) were examined in HK2 cells and diabetic mice kidneys. The in vitro results showed that TGF-β1 significantly inhibited mitochondrial ATP production rate and increased mitochondrial ROS (mtROS) production when compared to control, which was normalized by KCa3.1 gene silencing. Increased fission and suppressed fusion were found in both TGF-β1-treated HK2 cells and diabetic mice, which were reversed by KCa3.1 deficiency. Furthermore, our results showed that mitophagy was inhibited in both in vitro and in vivo models of diabetic kidney disease. KCa3.1 deficiency restored abnormal mitophagy by inhibiting BNIP3 expression in TGF-β1-induced HK2 cells as well as in the diabetic mice. Collectively, these results indicate that KCa3.1 mediates the dysregulation of mitochondrial quality control in diabetic kidney disease.

Targeting autophagy using saponins as a therapeutic and preventive strategy against human diseases

Autophagy is a ubiquitous mechanism for maintaining cellular homeostasis through the degradation of long-lived proteins, insoluble protein aggregates, and superfluous or damaged organelles. Dysfunctional autophagy is observed in a variety of human diseases. With advanced research into the role that autophagy plays in physiological and pathological conditions, targeting autophagy is becoming a novel tactic for disease management. Saponins are naturally occurring glycosides containing triterpenoids or steroidal sapogenins as aglycones, and some saponins are reported to modulate autophagy. Research suggests that saponins may have therapeutic and preventive efficacy against many autophagy-related diseases. Therefore, this review comprehensively summarizes and discusses the reported saponins that exhibit autophagy regulating activities. In addition, the relevant signaling pathways that the mechanisms involved in regulating autophagy and the targeted diseases were also discussed. By regulating autophagy and related pathways, saponins exhibit bioactivities against cancer, neurodegenerative diseases, atherosclerosis and other cardiac diseases, kidney diseases, liver diseases, acute pancreatitis, and osteoporosis. This review provides an overview of the autophagy-regulating activity of saponins, the underlying mechanisms and potential applications for managing various diseases.

Traditional uses, processing methods, phytochemistry, pharmacology and quality control of Dipsacus asper Wall. ex C.B. Clarke: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Dipsacus asper Wall. ex C.B. Clarke, a traditional Chinese herbal medicine, has long been used in China for the therapy of bone diseases (e.g. bone fracture, osteoporosis, rheumatic arthritis), traumatic hematoma, uterine bleeding and those caused by the deficiency of liver and kidney.

AIM OF THE STUDY

This work aims to evaluate current research progress on chemical constituents, pharmacological activities, quality control, and pharmacokinetic of Dipsacus asper Wall. ex C.B. Clarke, pinpoint the shortcomings of existing studies, and provide meaningful guidelines for our future investigations.

METHODS

Extensive database retrieval, such as PubMed, SciFinder and CNKI, was carried out by using keywords such as "Dipsacus asper", "Radix Dipsaci", and "Xuduan". Furthermore, relevant textbooks, patents, reviews, and digital documents were consulted to collate all available scientific literature and to provide a complete science-based survey of the topic.

RESULTS

More than 100 compounds have been isolated and identified from Dipsacus asper Wall. ex C.B. Clarke, a substantial proportion of which were reported to be triterpenoids and iridoids. Biological effects such as protective effects against bone fracture, anti-osteoporosis, neuroprotective, cardioprotective, anti-aging and protection of reproductive system activities were also evaluated in vitro and in vivo.

CONCLUSIONS

Diaphoretic processing resulted in the drop in the content of asperosaponin VI, which was highly associated with bone protective effect of DA. Therefore, diaphoretic processing was not a suitable processing method for DA. Although Dipsacus asper Wall. ex C.B. Clarke was traditionally used for therapy of osteoarthritis, the in-depth study of the underlying mechanism was very rare. Much endeavor had been made on the effect of DA on bone fracture. Notably, high-dose of Dipsacus asper administration may cause adverse impacts in maternal healthy and embryo-fetal development. It's not suitable for further development in those bioactivities, such as anti-inflammatory and free radical scavenging, which are shared in many other plant species. Pharmacological effects of individual component of DA is not equivalent to its traditional usage. Attention should be paid to the traditional effect of extract of DA.

The role of Neu1 in the protective effect of dipsacoside B on acetaminophen-induced liver injury

Background

Pharmacological induction of autophagy can protect against acetaminophen (APAP) induced acute liver failure (ALF) by removing APAP adducts (APAP-AD), but its mechanism is not well understood. Hepatoprotective effect of saponins from traditional Chinese medicine has attracted widespread attention from all over the world. The content of saponins in Lonicerae Flos (Shanyinhua in Chinese) is up to 15–25%. Dipsacoside B (DB) is a common bioactive ingredient of different Shanyinhua, but its hepatoprotective effect and mechanism are still unknown. The present investigation aimed to study the benefit of DB in APAP-induced hepatotoxicity mouse model and different cell model.

Methods

Mice were treated with DB by intraperitoneal injection 1 h before treated with 500 mg/kg APAP, which caused ALF after 4 h. HepG2 cells were treated with DB for 1 h before treated with 10 mM APAP for 12 h. Hepatotoxicity was assessed via ALT and AST. Neuraminidase 1 (Neu1), lysosomal autophagy marker LC3 and P62 were examined by western blot. Neu1 activity was assayed using its substrate 2-(4-methylumbelliferyl)-D-N-acetylneuraminic acid. Apoptosis level was examined by TUNEL and caspase 3 activity. Molecular docking was used to predict the interaction between DB and protein Neu1.

Results

Our results demonstrated that pretreatment with 0.5 μM DB (in vitro) and 50 mg/kg DB (in vivo) respectively reversed increased level of AST and ALT induced by APAP. Histopathological examinations showed reduced necrosis and apoptosis in the liver of DB-treated APAP mice. DB promoted the removal of APAP-AD by lysosomal autophagy. These effects were associated with significant decrease in the level of Neuraminidase 1 (Neu1), a negative regulator of lysosomal exocytosis. Molecular docking results showed that DB could bind to Neu1 protein (binding energy =−7.86 kcal/mol). Akt/mTOR-mediated autophagy and inhibition of apoptosis may be the main mechanisms for the hepatoprotective effects of DB in acetaminophen-induced liver injury.

Conclusions

These data indicate that DB alleviated hepatotoxicity caused by APAP at least in part via Neu1 inhibition, Akt/mTOR pathway is involved in the detoxification effect of DB on acetaminophen-induced hepatotoxicity.

Mitophagy and Its Contribution to Metabolic and Aging-Associated Disorders

Significance: Mitochondria are the cellular powerhouses for ATP synthesis through oxidative phosphorylation, and the centers for fatty acid β-oxidation, metabolite synthesis, reactive oxygen species production, innate immunity, and apoptosis. To fulfill these critical functions, mitochondrial quality and homeostasis must be well maintained. Abnormal mitochondrial quality contributes to aging and age-related disorders, such as metabolic syndrome, cancers, and neurodegenerative diseases. Recent Advances: Mitophagy is a cellular process that selectively removes damaged or superfluous mitochondria by autolysosomal degradation and is regarded as one of the major mechanisms responsible for mitochondrial quality control. Critical Issues: To date, distinct mitophagy pathways have been discovered, including receptor-mediated mitophagy and ubiquitin-dependent mitophagy. Emerging knowledge of these pathways shows that they play important roles in sensing mitochondrial stress and signaling for metabolic adaptations. Future Directions: Here, we provide a review on the molecular mechanisms for mitophagy and its interplay with cellular metabolism, with a particular focus on its role in metabolic and age-related disorders.

Fatty liver diseases, mechanisms, and potential therapeutic plant medicines

The liver is an important metabolic organ and controls lipid, glucose and energy metabolism. Dysruption of hepatic lipid metabolism is often associated with fatty liver diseases, including nonalcoholic fatty liver disease (NAFLD), alcoholic fatty liver diseases (AFLD) and hyperlipidemia. Recent studies have uncovered the contribution of hormones, transcription factors, and inflammatory cytokines to the pathogenesis of dyslipidemia and fatty liver diseases. Moreover, a significant amount of effort has been put to examine the mechanisms underlying the potential therapeutic effects of many natural plant products on fatty liver diseases and metabolic diseases. We review the current understanding of insulin, thyroid hormone and inflammatory cytokines in regulating hepatic lipid metabolism, focusing on several essential transcription regulators, such as Sirtuins (SIRTs), Forkhead box O (FoxO), Sterol-regulatory element-binding proteins (SREBPs). We also discuss a few representative natural products with promising thereapeutic effects on fatty liver disease and dyslipidemia.

Role and Mechanisms of Mitophagy in Liver Diseases

The mitochondrion is an organelle that plays a vital role in the regulation of hepatic cellular redox, lipid metabolism, and cell death. Mitochondrial dysfunction is associated with both acute and chronic liver diseases with emerging evidence indicating that mitophagy, a selective form of autophagy for damaged/excessive mitochondria, plays a key role in the liver’s physiology and pathophysiology. This review will focus on mitochondrial dynamics, mitophagy regulation, and their roles in various liver diseases (alcoholic liver disease, non-alcoholic fatty liver disease, drug-induced liver injury, hepatic ischemia-reperfusion injury, viral hepatitis, and cancer) with the hope that a better understanding of the molecular events and signaling pathways in mitophagy regulation will help identify promising targets for the future treatment of liver diseases.

Bnip3 in mitophagy: Novel insights and potential therapeutic target for diseases of secondary mitochondrial dysfunction

The present review is a summary of the recent literature concerning Bnip3 expression, function, and regulation, along with its implications in mitochondrial dysfunction, disorders of mitophagy homeostasis, and development of diseases of secondary mitochondrial dysfunction. As a member of the Bcl-2 family of cell death-regulating factors, Bnip3 mediates mPTP opening, mitochondrial potential, oxidative stress, calcium overload, mitochondrial respiratory collapse, and ATP shortage of mitochondria from multiple cells. Recent studies have discovered that Bnip3 regulates mitochondrial dysfunction, mitochondrial fragmentation, mitophagy, cell apoptosis, and the development of lipid disorder diseases via numerous cellular signaling pathways. In addition, Bnip3 promotes the development of cardiac hypertrophy by mediating inflammatory response or the related signaling pathways of cardiomyocytes and is also responsible for raising abnormal mitophagy and apoptosis progression through multiple molecular signaling pathways, inducing the pathogenesis and progress of hepatocellular carcinoma (HCC). Different molecules regulate Bnip3 expression at both the transcriptional and post-transcriptional level, leading to mitochondrial dysfunction and unbalance of mitophagy in hepatocytes, which promotes the development of non-alcoholic fatty liver disease (NAFLD). Thus, Bnip3 plays an important role in mitochondrial dysfunction and mitophagy homeostasis and has emerged as a promising therapeutic target for diseases of secondary mitochondrial dysfunction.

Mitophagy in Hepatic Insulin Resistance: Therapeutic Potential and Concerns

Metabolic syndrome, characterized by central obesity, hypertension, and hyperlipidemia, increases the morbidity and mortality of cardiovascular disease, type 2 diabetes, nonalcoholic fatty liver disease, and other metabolic diseases. It is well known that insulin resistance, especially hepatic insulin resistance, is a risk factor for metabolic syndrome. Current research has shown that hepatic fatty acid accumulation can cause hepatic insulin resistance through increased gluconeogenesis, lipogenesis, chronic inflammation, oxidative stress and endoplasmic reticulum stress, and impaired insulin signal pathway. Mitochondria are the major sites of fatty acid β-oxidation, which is the major degradation mechanism of fatty acids. Mitochondrial dysfunction has been shown to be involved in the development of hepatic fatty acid–induced hepatic insulin resistance. Mitochondrial autophagy (mitophagy), a catabolic process, selectively degrades damaged mitochondria to reverse mitochondrial dysfunction and preserve mitochondrial dynamics and function. Therefore, mitophagy can promote mitochondrial fatty acid oxidation to inhibit hepatic fatty acid accumulation and improve hepatic insulin resistance. Here, we review advances in our understanding of the relationship between mitophagy and hepatic insulin resistance. Additionally, we also highlight the potential value of mitophagy in the treatment of hepatic insulin resistance and metabolic syndrome.

Insufficient radiofrequency ablation-induced autophagy contributes to the rapid progression of residual hepatocellular carcinoma through the HIF-1α/BNIP3 signaling pathway

Currently speaking, it is noted that radiofrequency ablation (RFA) has been the most widely used treatment for hepatocellular carcinoma (HCC) occurring in patients. However, accumulating evidence has demonstrated that the incidence of insufficient RFA (IRFA) may result in the identified rapid progression of residual HCC in the patient, which can greatly hinder the effectiveness and patient reported benefits of utilizing this technique. Although many efforts have been proposed, the underlying mechanisms triggering the rapid progression of residual HCC after IRFA have not yet been fully clarified through current research literature reviews. It was shown in this study that cell proliferation, migration and invasion of residual HepG2 and SMMC7721 cells were significantly increased after the IRFA was simulated in vitro. In other words, it is noted that IRFA could do this by enhancing the image of autophagy of the residual HCC cell via the HIF-1α/BNIP3 pathway. Consequently, the down-regulation of BNIP3 may result in the inhibition of the residual HCC cell progression and autophagy after IRFA. Our present study results suggest that IRFA could promote residual HCC cell progression in vitro by enhancing autophagy via the HIF-1α/BNIP3 pathway. For this reason, it is noted that the targeting of the BNIP3 may be useful in preventing the rapid growth and metastasis of residual HCC after IRFA.

Akebia Saponin D Regulates the Metabolome and Intestinal Microbiota in High Fat Diet-Induced Hyperlipidemic Rats

Hyperlipidemia is a major component of metabolic syndrome, and regarded as one of the main risk factors causing metabolic diseases. We have developed a therapeutic drug, akebia saponin D (ASD), and determined its anti-hyperlipidemia activity and the potential mechanism(s) of action by analyzing the metabolome and intestinal microbiota. Male Sprague-Dawley rats were fed a high fat diet to induce hyperlipidemia, and then given ASD orally for 8 weeks. Lipid levels in serum were determined biochemically. Metabolites in serum, urine and feces were analyzed by UPLC-Q/TOF-MS, and the structure of the intestinal microbiota was determined by 16S rRNA sequencing. The ASD treatment significantly decreased the levels of TC, TG and LDL-c and increased the serum level of HDL-c. Metabolomics analysis indicated that the ASD treatment mainly impacted seven differential metabolites in the serum, sixteen differential metabolites in the urine and four differential metabolites in feces compared to the model group. The ASD treatment significantly changed eight bacteria at the genus level compared to the model group. In conclusion, ASD treatment can significantly alleviate HFD-induced hyperlipidemia and the hypolipidemic effect of ASD treatment is certainly associated with a systematic change in the metabolism, as well as dynamic changes in the structure of the intestinal microbiota.

Anti-nociceptive and anti-inflammatory potentials of Akebia saponin D

Akebia saponin D, which is originates from Dipsacus asper Wall, has been used as a tonic, an analgesic and anti-inflammatory agent for the therapy of low back pain, rheumatic arthritis, traumatic hematoma, habitual abortion and bone fractures in traditional Chinese medicine. However, the anti-nociceptive and anti-inflammatory activity and mechanism of Akebia saponin D has been rarely reported. The aim of this study was to investigate the anti-nociceptive and anti-inflammatory activity of Akebia saponin D and to assess its possible mechanism. The anti-nociceptive effect was measured by formalin test, hot plate, and acetic acid-induced writhing in mice while the anti-inflammatory effect was measured by carrageenan induced paw edema test, xylene-induced ear swelling and acetic acid-induced vascular permeability in mice and rats. Furthermore, anti-inflammatory effect was also measured in vitro using LPS-induced RAW 264.7 cells. Our results demonstrated that Akebia saponin D dose-dependently decreased the licking time in the formalin test, delayed the reaction time of mice to the hot plate, and inhibited acetic acid-induced writhing. Treatment of Akebia saponin D attenuated the carrageenan induced paw edema in rats, inhibited the mouse ear swelling, and decreased Evans blue concentration in acetic acid induced vascular permeability test, revealing its strong anti-inflammatory effect. Akebia saponin D significantly decreased NO production and iNOS expression. Our results indicate that Akebia saponin D has anti-nociceptive and anti-inflammatory effects. It will provide experimental evidences for the use of Akebia saponin D and can be used to develop a therapeutic drug against pain and inflammation related diseases.