A New Possible Mechanism by Which Punicalagin Protects against Liver Injury Induced by Type 2 Diabetes Mellitus: Upregulation of Autophagy via the Akt/FoxO3a Signaling Pathway

Polyphenol-Rich Extracts from Agroindustrial Waste and Byproducts: Results and Perspectives According to the Green Chemistry and Circular Economy

Polyphenols are natural secondary metabolites found in plants endowed with multiple biological activities (antioxidant, anti-inflammatory, antimicrobial, cardioprotective, and anticancer). In view of these properties, they find many applications and are used as active ingredients in nutraceutical, food, pharmaceutical, and cosmetic formulations. In accordance with green chemistry and circular economy strategies, they can also be recovered from agroindustrial waste and reused in various sectors, promoting sustainable processes. This review described structural characteristics, methods for extraction, biological properties, and applications of polyphenolic extracts obtained from two selected plant materials of the Mediterranean area as olive (Olea europaea L.) and pomegranate (Punica granatum L.) based on recent literature, highlighting future research perspectives.

The role of autophagy in insulin resistance and glucolipid metabolism and potential use of autophagy modulating natural products in the treatment of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a severe, long-term condition characterised by disruptions in glucolipid and energy metabolism. Autophagy, a fundamental cellular process, serves as a guardian of cellular health by recycling and renewing cellular components. To gain a comprehensive understanding of the vital role that autophagy plays in T2DM, we conducted an extensive search for high-quality publications across databases such as Web of Science, PubMed, Google Scholar, and SciFinder and used keywords like 'autophagy', 'insulin resistance', and 'type 2 diabetes mellitus', both individually and in combinations. A large body of evidence underscores the significance of activating autophagy in alleviating T2DM symptoms. An enhanced autophagic activity, either by activating the adenosine monophosphate-activated protein kinase and sirtuin-1 signalling pathways or inhibiting the mechanistic target of rapamycin complex 1 signalling pathway, can effectively improve insulin resistance and balance glucolipid metabolism in key tissues like the hypothalamus, skeletal muscle, liver, and adipose tissue. Furthermore, autophagy can increase β-cell mass and functionality in the pancreas. This review provides a narrative summary of autophagy regulation with an emphasis on the intricate connection between autophagy and T2DM symptoms. It also discusses the therapeutic potentials of natural products with autophagy activation properties for the treatment of T2DM conditions. Our findings suggest that autophagy activation represents an innovative approach of treating T2DM.

Modulation Effects of Sargassum pallidum Extract on Hyperglycemia and Hyperlipidemia in Type 2 Diabetic Mice

The aim of this study was to investigate the antidiabetic effect of the extract from Sargassum pallidum (SPPE) on type 2 diabetes mellitus (T2DM) mice. SPPE treatment alleviated hyperglycemia, insulin resistance (IR), liver and pancreatic tissue damage, hyperlipidemia and hepatic oxidative stress resulting from T2DM. SPPE reversed phosphoenolpyruvate carboxylase (PEPCK) and hexokinase (HK) activities to improve gluconeogenesis and glycogen storage in the liver. Furthermore, SPPE modulated glucose metabolism by regulating the levels of mRNA expression involving the PI3K/Akt/FOXO1/G6pase/GLUT2 pathway and could inhibit fatty acid synthesis by reducing the gene expression levels of fatty acid synthase (FAS) and acetyl-CoA carboxylase-1 (ACC-1). A 16 sRNA analysis indicated that SPPE treatment also reversed gut dysbiosis by increasing the abundance of beneficial bacteria (Bacteroides and Lactobacillus) and suppressing the proliferation of harmful bacteria (Enterococcus and Helicobacter). Untargeted metabolomics results indicated that histidine metabolism, nicotinate and nicotinamide metabolism and fatty acid biosynthesis were significantly influenced by SPPE. Thus, SPPE may be applied as an effective dietary supplement or drug in the management of T2DM.

The Modulatory Bioeffects of Pomegranate (Punica granatum L.) Polyphenols on Metabolic Disorders: Understanding Their Preventive Role against Metabolic Syndrome

Modern research achievements support the health-promoting effects of natural products and diets rich in polyphenols. Pomegranate (PG) (Punica granatum L.) contains a considerable number of bioactive compounds that exert a broad spectrum of beneficial biological activities, including antimicrobial, antidiabetic, antiobesity, and atheroprotective properties. In this context, the reviewed literature shows that PG intake might reduce insulin resistance, cytokine levels, redox gene expression, blood pressure elevation, vascular injuries, and lipoprotein oxidative modifications. The lipid parameter corrective capabilities of PG-ellagitannins have also been extensively reported to be significantly effective in reducing hyperlipidemia (TC, LDL-C, VLDL-C, and TAGs), while increasing plasma HDL-C concentrations and improving the TC/HDL-C and LDL-C/HDL-C ratios. The health benefits of pomegranate consumption seem to be acheived through the amelioration of adipose tissue endocrine function, fatty acid utilization, GLUT receptor expression, paraoxonase activity enhancement, and the modulation of PPAR and NF-κB. While the results from animal experiments are promising, human findings published in this field are inconsistent and are still limited in several aspects. The present review aims to discuss and provide a critical analysis of PG's bioeffects on the components of metabolic syndrome, type-2 diabetes, obesity, and dyslipidemia, as well as on certain cardiovascular-related diseases. Additionally, a brief overview of the pharmacokinetic properties, safety, and bioavailability of PG-ellagitannins is included.

The role of autophagy in the treatment of type II diabetes and its complications: a review

Type II diabetes mellitus (T2DM) is a chronic metabolic disease characterized by prolonged hyperglycemia and insulin resistance (IR). Its incidence is increasing annually, posing a significant threat to human life and health. Consequently, there is an urgent requirement to discover effective drugs and investigate the pathogenesis of T2DM. Autophagy plays a crucial role in maintaining normal islet structure. However, in a state of high glucose, autophagy is inhibited, resulting in impaired islet function, insulin resistance, and complications. Studies have shown that modulating autophagy through activation or inhibition can have a positive impact on the treatment of T2DM and its complications. However, it is important to note that the specific regulatory mechanisms vary depending on the target organ. This review explores the role of autophagy in the pathogenesis of T2DM, taking into account both genetic and external factors. It also provides a summary of reported chemical drugs and traditional Chinese medicine that target the autophagic pathway for the treatment of T2DM and its complications.

FoxO3 and oxidative stress: a multifaceted role in cellular adaptation

Oxidative stress is a major cause of morbidity and mortality in human health and disease. In this review, we focus on the Forkhead Box (Fox) subclass O3 (FoxO3), an extensively studied transcription factor that plays a pleiotropic role in a wide range of physiological and pathological processes by regulating multiple gene regulatory networks involved in the modulation of numerous aspects of cellular metabolism, including fuel metabolism, cell death, and stress resistance. This review will also focus on regulatory mechanisms of FoxO3 expression and activity, such as crucial post-translational modifications and non-coding RNAs. Moreover, this work discusses and evidences some pathways to how this transcription factor and reactive oxygen species regulate each other, which may lead to the pathogenesis of various types of diseases. Therefore, in addition to being a promising therapeutic target, the FoxO3-regulated signaling pathways can also be used as reliable diagnostic and prognostic biomarkers and indicators for drug responsiveness.

Effects of high-fat diet-induced diabetes on autophagy in the murine liver: A systematic review and meta-analysis

AIMS

We conducted a meta-analysis to investigate whether diabetes induced by a high-fat diet (HFD) has the potential to alter the process of autophagy in the murine liver.

METHODS

A systematic literature search was performed with electronic databases (PubMed, EMBASE, Web of Science). Study design, population, intervention, outcome, and risk of bias were analyzed. Given the availability of studies, a quantitative meta-analysis including 23 studies was performed.

KEY FINDINGS

The search found 5754 articles, with 48 matching the eligibility criteria, comprising of 1033 animals. The meta-analysis showed that diabetic murines fed with HFD presented an absence of p62 degradation (SMD 4.63, 95 % CI 2.02 to 7.24, p = 0.0005; I² = 77 %), higher expression of p-mTOR/mTOR (SMD 5.20, 95 % CI 1.00 to 9.39, p = 0.01; I² = 78 %), and a decreased p-AMPK/AMPK ratio (SMD -2.02, 95 % CI -3.96 to -0.09, p = 0.04; I² = 85 %) when compared to nondiabetic murines. When associated with streptozotocin, the animals presented decreased ATG-7 and LC3-II. The meta-regression results showed a decrease in autophagy responses due to increased glycemic levels, fat content, and long-term exposure to HFD, and advanced animal age. The common and species-specific protein responses were also consistent with the inhibition of autophagy.

SIGNIFICANCE

The normal process of autophagy mechanisms in the liver is less competent after HFD consumption. The destabilization of (auto)phagolysosomes contributes to the perpetuation of diabetes, metabolic dysfunction-associated fatty liver disease, and cell death.

Exploring Active Ingredients, Beneficial Effects, and Potential Mechanism of Allium tenuissimum L. Flower for Treating T2DM Mice Based on Network Pharmacology and Gut Microbiota

Forty compounds were isolated and characterized from A. tenuissimum flower. Among them, twelve flavonoids showed higher α−glucosidase inhibition activities in vitro than acarbose, especially kaempferol. The molecular docking results showed that the binding of kaempferol to α−glucosidase (GAA) could reduce the hydrolysis of substrates by GAA and reduce the glucose produced by hydrolysis, thus exhibiting α−glucosidase inhibition activities. The in vivo experiment results showed that flavonoids−rich A. tenuissimum flower could decrease blood glucose and reduce lipid accumulation. The protein expression levels of RAC−alpha serine/threonine−protein kinase (AKT1), peroxisome proliferator activated receptor gamma (PPARG), and prostaglandin G/H synthase 2 (PTGS2) in liver tissue were increased. In addition, the Firmicutes/Bacteroidetes (F/B) ratio was increased, the level of gut probiotics Bifidobacterium was increased, and the levels of Enterobacteriaceae and Staphylococcus were decreased. The carbohydrate metabolism, lipid metabolism, and other pathways related to type 2 diabetes mellitus were activated. This study indicating flavonoids−rich A. tenuissimum flower could improve glycolipid metabolic disorders and inflammation in diabetic mice by modulating the protein expression and gut microbiota.

Trilobatin alleviates non-alcoholic fatty liver disease in high-fat diet plus streptozotocin-induced diabetic mice by suppressing NLRP3 inflammasome activation

Diabetes mellitus (DM) is a factor with great risk in the course of non-alcoholic fatty liver disease (NAFLD) due to its high glucotoxicity and lipotoxicity. Trilobatin, a glycosylated dihydrochalcone derived from the leaves of the Chinese sweet tea Lithocarpus polystachyus Rehd, is reported to possess various pharmacological activities. Nevertheless, it is still unclear regarding if trilobatin can alleviate liver injury in diabetic mice with NAFLD and its mechanism. Our aim was to investigative the protective effects of trilobatin against DM with NAFLD and its mechanism of action. A DM mice model was established by high-fat diet (HFD) feeding with streptozocin (STZ) injections, and treated with trilobatin for 10 weeks. The biochemical results showed that trilobatin restored glucose metabolic disorder and liver function in diabetic mice. The histopathological evaluation revealed that trilobatin improved liver injury by alleviating lipid accumulation and liver fibrosis. Mechanistically, trilobatin decreased expression of NLRP3, p65 NF-κB, cleaved-Caspase-1 and N-GSDMD, as well as the release of IL-18 and IL-1β, leading to a alleviation of inflammation and pyroptosis. Taken together, we determined for the first time found that trilobatin could prevent liver injury in diabetic mice with NAFLD by suppressing NLRP3 inflammasome activation to reduce inflammation and pyroptosis.

Autophagy-nutrient sensing pathways in diabetic complications

The incidence of diabetes has been increasing in recent decades which is affecting the population of both, developed and developing countries. Diabetes is associated with micro and macrovascular complications which predominantly result from hyperglycemia and disrupted metabolic pathways. Persistent hyperglycemia leads to increased reactive oxygen species (ROS) generation, formation of misfolded and abnormal proteins, and disruption of normal cellular functioning. The inability to maintain metabolic homeostasis under excessive energy and nutrient input, which induces insulin resistance, is a crucial feature during the transition from obesity to diabetes. According to various study reports, redox alterations, intracellular stress and chronic inflammation responses have all been linked to dysregulated energy metabolism and insulin resistance. Autophagy has been considered a cleansing mechanism to prevent these anomalies and restore cellular homeostasis. However, disrupted autophagy has been linked to the pathogenesis of metabolic disorders such as obesity and diabetes. Recent studies have reported that the regulation of autophagy has a beneficial role against these conditions. When there is plenty of food, nutrient-sensing pathways activate anabolism and storage, but the shortage of food activates homeostatic mechanisms like autophagy, which mobilises internal stockpiles. These nutrient-sensing pathways are well conserved in eukaryotes and are involved in the regulation of autophagy which includes SIRT1, mTOR and AMPK. The current review focuses on the role of SIRT1, mTOR and AMPK in regulating autophagy and suggests autophagy along with these nutrient-sensing pathways as potential therapeutic targets in reducing the progression of various diabetic complications.

Punicalagin Protects against Diabetic Liver Injury by Upregulating Mitophagy and Antioxidant Enzyme Activities

Diabetic liver injury has received increasing attention as a serious complication of type 2 diabetes. Punicalagin (PU), a major component of pomegranate polyphenols, has various biological activities such as antioxidant, anti-inflammatory, and lipid metabolism regulation. In this study, we observed the protective effect of punicalagin on a high-fat diet (HFD) and streptozotocin (STZ)-induced diabetic liver injury in mice and revealed the underlying mechanism. The results showed that fasting blood glucose (FBG), fasting serum insulin (FINS), and homeostasis model assessment for insulin resistance (HOMA-IR) in diabetic liver injury mice were significantly decreased after punicalagin intervention. Simultaneously, the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), free fatty acids (FFA), malondialdehyde (MDA), and total superoxide dismutase (T-SOD) in the serum and liver were significantly decreased, with reductions in fat lesions and inflammatory cells. Mitophagy is a selective autophagy that maintains a balance between the quality and quantity of intracellular mitochondria. Studies have shown that mitophagy is closely related to the occurrence and development of diabetic liver injury. In our study, the mitochondrial membrane potential (MMP) was significantly increased in mice with diabetic liver injury after punicalagin intervention; the protein expression of Pink1, Parkin, Bnip3, LC3b, P62, manganese superoxide dismutase (MnSOD), and catalase (CAT) was significantly increased in the liver; and the activities of MnSOD and CAT in the serum and liver were significantly increased, which is consistent with the results of in vitro experiments. In summary, our study provided evidence that punicalagin could reduce the level of oxidative stress in the liver by upregulating mitophagy and the activities of antioxidant enzymes, thus having a certain protective effect against diabetic liver injury.

Sterol carrier protein 2 in lipid metabolism and non-alcoholic fatty liver disease: Pathophysiology, molecular biology, and potential clinical implications

Non-alcoholic fatty liver disease (NAFLD) is considered as the most common chronic liver disease and has become a rapidly global public health problem. Sterol carrier protein 2 (SCP-2), also called non-specific lipid-transfer protein, is predominantly expressed by the liver. SCP-2 plays a key role in intracellular lipid transport and metabolism. SCP-2 has been closely implicated in the development of NAFLD-related metabolic disorders, such as obesity, atherosclerosis, Type 2 diabetes mellitus (T2DM), and gallstones. Recent studies indicate that SCP-2 plays a beneficial role in NAFLD by regulating cholesterol-, endocannabinoid-, and fatty acid-related aspects of lipid metabolism. Hence, in this paper, we summarize the latest findings about the roles of SCP-2 in hepatic steatosis and further describe its molecular function in the pathogenesis of NAFLD.

Oral Supplement Containing Hydroxytyrosol and Punicalagin Improves Dyslipidemia in an Adult Population without Co-Adjuvant Treatment: A Randomized, Double-Blind, Controlled and Crossover Trial

Hydroxytyrosol (HT) and punicalagin (PC) exert cardioprotective and antiatherosclerotic effects. This study evaluated the effect of an oral supplement containing HT and PC (SAx) on dyslipidemia in an adult population. A randomized, double-blind, controlled, crossover trial was conducted over a 20-week period. SAx significantly reduced the plasma levels of triglycerides (TG) in subjects with hypertriglyceridemia (≥150 mg/dL) (from 200.67 ± 51.38 to 155.33 ± 42.44 mg/dL; p < 0.05), while no such effects were observed in these subjects after the placebo. SAx also significantly decreased the plasma levels of low-density lipoprotein cholesterol (LDL-C) in subjects with high plasma levels of LDL-C (≥160 mg/dL) (from 179.13 ± 16.18 to 162.93 ± 27.05 mg/dL; p < 0.01), while no such positive effect was observed with the placebo. In addition, the placebo significantly reduced the plasma levels of high-density lipoprotein cholesterol (HDL-C) in the total population (from 64.49 ± 12.65 to 62.55 ± 11.57 mg/dL; p < 0.05), while SAx significantly increased the plasma levels of HDL-C in subjects with low plasma levels of HDL-C (<50 mg/dL) (from 44.25 ± 3.99 to 48.00 ± 7.27 mg/dL; p < 0.05). In conclusion, the supplement containing HT and PC exerted antiatherosclerotic and cardio-protective effects by considerably improving dyslipidemia in an adult population, without co-adjuvant treatment or adverse effects.

Punicalagin Attenuates Neuronal Apoptosis by Upregulating 5-Hydroxymethylcytosine in the Diabetic Mouse Brain

Punicalagin exerts neuroprotective activity by improving AMP-activated kinase (AMPK) and mitochondrial Krebs cycle. AMPK and Krebs cycle metabolites regulate 5-hydroxymethylcytosine (5hmC) via acting on ten-eleven translocation (TET) enzymes. Therefore, we hypothesized that punicalagin inhibits diabetes-related neuronal apoptosis by upregulating 5hmC in the diabetic mouse brain. C57BL/6J mice aged 8 weeks were randomly separated into five groups (n = 10), normal control (NC), diabetes mellitus (DM), resveratrol (RES), low-dose punicalagin (LPU), and high-dose punicalagin (HPU). Compared with other groups, the neuronal apoptosis rate was significantly higher and the 5hmC level of the cerebral cortex was significantly lower in the DM group. The levels of TET2 and P-AMPKα/AMPKα were significantly lower in the DM group than in both LPU and HPU groups. The ratio of (succinic acid + fumaric acid)/α-ketoglutarate was significantly higher in the DM group than in other groups. The present results suggest that punicalagin upregulates 5hmC via activating AMPK and maintaining Krebs cycle homeostasis, thus inhibiting neuronal apoptosis in the diabetic mouse brain.

Sesamol Reverses Myofiber-Type Conversion in Obese States via Activating the SIRT1/AMPK Signal Pathway

Obesity can evoke changes of skeletal muscle structure and function, which are characterized by the conversion of myofiber from type I to type II, leading to a vicious cycle of metabolic disorders. Reversing the muscle fiber-type conversion in obese states is a novel strategy for treating those with obesity. Sesamol, a food ingredient compound isolated from sesame seeds, exerted potential antiobesity effects. The present research aimed to explore the therapeutic effects of sesamol on obesity-related skeletal muscle-fiber-type conversion and elucidate the underlying molecular mechanisms through utilizing a high-fat-diet-induced obese C57BL/6J mice model and palmitic acid-exposed C2C12 myotubes. The results showed that sesamol attenuated obesity-related metabolic disturbances, elevated exercise endurance of obese mice, and decreased lipid accumulation and insulin resistance in skeletal muscle. After the treatment with sesamol, the muscular mitochondrial content and biogenesis were increased, accompanied by the enzyme activities and myosin heavy-chain isoform changed from type II fiber to type I fiber. Mechanistic studies revealed that the effects of sesamol on reversing skeletal muscle-fiber-type conversion in obese states were associated with the stimulation of the muscular sirtuin 1 (SIRT1)/AMP-activated protein kinase (AMPK) signal pathway, and these effects could be inhibited by a specific inhibitor of SIRT1, EX-527. In conclusion, our research provided novel evidence that sesamol could regulate myofiber-type conversion to treat obesity and obesity-related metabolic disorders by stimulating the muscular SIRT1/AMPK signal pathway.

Therapeutic Potential of Pomegranate in Metabolic Disorders

Metabolic syndrome and associated disorders have become one of the major challenging health problems over the last decades. Considerable attention has been paid to natural products and herbal medicines for the management of metabolic disorders in recent years. Many studies have investigated the therapeutic effects of different parts (arils, peels, seeds, and flowers) of pomegranate (Punica granatum L.) for the prevention and treatment of this syndrome. This study aims to provide an updated review on the in vitro and in vivo studies as well as clinical trials investigating the effects of pomegranate and its active compounds on different components of metabolic problems such as hyperglycemia, hyperlipidemia, hypertension, as well as obesity over the last two decades. Besides, the key mechanisms by which pomegranate affects these pathogenic conditions are also discussed. The studies show that although pomegranate has promising beneficial effects on diabetes, hypertension, hyperlipidemia, and obesity in various cellular, animal, and clinical models of studies, there are some conflicting results, particularly for hyperglycemic conditions. The main mechanisms include influencing oxidative stress and anti-inflammatory responses. Overall, pomegranate seems to have positive effects on the pathogenic conditions of metabolic syndrome according to the reviewed studies. Although pomegranate is not suggested as the first line of therapy or monotherapy, it could be only used as an adjunctive therapy. Nevertheless, further large and long-term clinical studies are still required.

Omnifarious fruit polyphenols: an omnipotent strategy to prevent and intervene diabetes and related complication?

Diabetes mellitus is a metabolic syndrome which cannot be cured. Recently, considerable interest has been focused on food ingredients to prevent and intervene in complications of diabetes. Polyphenolic compounds are one of the bioactive phytochemical constituents with various biological activities, which have drawn increasing interest in human health. Fruits are part of the polyphenol sources in daily food consumption. Fruit-derived polyphenols possess the anti-diabetic activity that has already been proved either from in vitro studies or in vivo studies. The mechanisms of fruit polyphenols in treating diabetes and related complications are under discussion. This is a comprehensive review on polyphenols from the edible parts of fruits, including those from citrus, berries, apples, cherries, mangoes, mangosteens, pomegranates, and other fruits regarding their potential benefits in preventing and treating diabetes mellitus. The signal pathways of characteristic polyphenols derived from fruits in reducing high blood glucose and intervening hyperglycemia-induced diabetic complications were summarized.

Plant Polyphenols for Aging Health: Implication from Their Autophagy Modulating Properties in Age-Associated Diseases

Polyphenols are a family of naturally occurring organic compounds, majorly present in fruits, vegetables, and cereals, characterised by multiple phenol units, including flavonoids, tannic acid, and ellagitannin. Some well-known polyphenols include resveratrol, quercetin, curcumin, epigallocatechin gallate, catechin, hesperetin, cyanidin, procyanidin, caffeic acid, and genistein. They can modulate different pathways inside the host, thereby inducing various health benefits. Autophagy is a conserved process that maintains cellular homeostasis by clearing the damaged cellular components and balancing cellular survival and overall health. Polyphenols could maintain autophagic equilibrium, thereby providing various health benefits in mediating neuroprotection and exhibiting anticancer and antidiabetic properties. They could limit brain damage by dismantling misfolded proteins and dysfunctional mitochondria, thereby activating autophagy and eliciting neuroprotection. An anticarcinogenic mechanism is stimulated by modulating canonical and non-canonical signalling pathways. Polyphenols could also decrease insulin resistance and inhibit loss of pancreatic islet β-cell mass and function from inducing antidiabetic activity. Polyphenols are usually included in the diet and may not cause significant side effects that could be effectively used to prevent and treat major diseases and ailments.

Natural Polyphenols in Metabolic Syndrome: Protective Mechanisms and Clinical Applications

Metabolic syndrome (MetS) is a chronic disease, including abdominal obesity, dyslipidemia, hyperglycemia, and hypertension. It should be noted that the occurrence of MetS is closely related to oxidative stress-induced mitochondrial dysfunction, ectopic fat accumulation, and the impairment of the antioxidant system, which in turn further aggravates the intracellular oxidative imbalance and inflammatory response. As enriched anti-inflammatory and antioxidant components in plants, natural polyphenols exhibit beneficial effects, including improving liver fat accumulation and dyslipidemia, reducing blood pressure. Hence, they are expected to be useful in the prevention and management of MetS. At present, epidemiological studies indicate a negative correlation between polyphenol intake and MetS incidence. In this review, we summarized and discussed the most promising natural polyphenols (including flavonoid and non-flavonoid drugs) in the precaution and treatment of MetS, including their anti-inflammatory and antioxidant properties, as well as their regulatory functions involved in glycolipid homeostasis.

Overview of key molecular and pharmacological targets for diabetes and associated diseases

Diabetes epidemiological quantities are demonstrating one of the most important communities' health worries. The essential diabetic difficulties are including cardiomyopathy, nephropathy, inflammation, and retinopathy. Despite developments in glucose decreasing treatments and drugs, these diabetic complications are still ineffectively reversed or prohibited. Several signaling and molecular pathways are vital targets in the new therapies of diabetes. This review assesses the newest researches about the key molecules and signaling pathways as targets of molecular pharmacology in diabetes and diseases related to it for better treatment based on molecular sciences. The disease is not cured by current pharmacological strategies for type 2 diabetes. While several drug combinations are accessible that can efficiently modulate glycemia and mitigate long-term complications, these agents do not reverse pathogenesis, and in practice, they are not established to modify the patient's specific molecular profiling. Therapeutic companies have benefited from human genetics. Genome exploration, which is agnostic to the information that exists, has revealed tens of loci that impact glycemic modulation. The physiological report has begun to examine subtypes of diseases, illustrate heterogeneity and propose biochemical therapeutic pathways.

Punicalagin improves hepatic lipid metabolism via modulation of oxidative stress and mitochondrial biogenesis in hyperlipidemic mice

Hyperlipidemia is closely associated with various liver diseases, and effective intervention for prevention and treatment is in great need. Here, we aim to explore the protective effects of punicalagin (PU), a major ellagitannin in pomegranate, on acute hyperlipidemia-induced hepatic lipid metabolic disorders. Male C57bl/6J mice were pretreated with 50 or 200 mg kg-1 day-1 PU for 9 days before the injection of poloxamer 407 to induce acute hyperlipidemia. PU significantly lowered lipids and liver damage markers in serum, reduced excessive lipid accumulation in the liver, attenuated hepatic oxidative stress by activating the NF-E2 related factor 2 (Nrf2)-mediated antioxidant pathway, and enhanced hepatic mitochondrial complex activities and mitochondrial DNA copy number by promoting the peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α)-mediated mitochondrial biogenesis pathway. Moreover, the decreased mitochondrial fusion-related proteins were also restored by PU treatment. In vitro, PU effectively decreased triglycerides and total cholesterol levels, up-regulated Nrf2 and mitochondrial biogenesis pathways and partially restored the mitochondrial morphology in palmitic acid-treated HepG2 cells. These results suggest that PU could improve acute hyperlipidemia-induced hepatic lipid metabolic abnormalities via decreasing oxidative stress and improving mitochondrial function both in vivo and in vitro, indicating that PU might be a potential intervention for hyperlipidemia-related liver diseases.

Astragaloside IV alleviates liver injury in type 2 diabetes due to promotion of AMPK/mTOR‑mediated autophagy

Diabetic liver injury is a serious complication of type 2 diabetes mellitus (T2DM), which is often irreversible in the later stage, and affects the quality of life. Autophagy serves an important role in the occurrence and development of diabetic liver injury. For example, it can improve insulin resistance (IR), dyslipidaemia, oxidative stress and inflammation. Astragaloside IV (AS-IV) is a natural saponin isolated from the plant Astragalus membranaceus, which has comprehensive pharmacological effects, such as anti-oxidation, anti-inflammation and anti-apoptosis properties, as well as can enhance immunity. However, whether AS-IV can alleviate diabetic liver injury in T2DM and its underlying mechanisms remain unknown. The present study used high-fat diets combined with low-dose streptozotocin to induce a diabetic liver injury model in T2DM rats to investigate whether AS-IV could alleviate diabetic liver injury and to identify its underlying mechanisms. The results demonstrated that AS-IV treatment could restore changes in food intake, water intake, urine volume and body weight, as well as improve liver function and glucose homeostasis in T2DM rats. Moreover, AS-IV treatment promoted suppressed autophagy in the liver of T2DM rats and improved IR, dyslipidaemia, oxidative stress and inflammation. In addition, AS-IV activated adenosine monophosphate-activated protein kinase (AMPK), which inhibited mTOR. Taken together, the present study suggested that AS-IV alleviated diabetic liver injury in T2DM rats, and its mechanism may be associated with the promotion of AMPK/mTOR-mediated autophagy, which further improved IR, dyslipidaemia, oxidative stress and inflammation. Thus, the regulation of autophagy may be an effective strategy to treat diabetic liver injury in T2DM.

Morus alba leaves ethanol extract protects pancreatic islet cells against dysfunction and death by inducing autophagy in type 2 diabetes

BACKGROUND

Protection of pancreatic islet cells against dysfunction or death by regulating autophagy is considered to be an effective method for treatment of type 2 diabetes mellitus (T2DM). Morus alba leaves (mulberry leaves), a popular herbal medicine, have been used for prevention of T2DM since ancient times.

PURPOSE

This study aimed to clarify whether Morus alba leaves ethanol extract (MLE) could protect islet cells in vivo and in vitro by regulating autophagy in T2DM, and explore the possible mechanism of action.

METHODS

The main chemical constituents in MLE were analyzed by HPLC. The T2DM rat model was induced via high-fat diet combined with peritoneal injection of low-dose streptozotocin, and MLE was administered by oral gavage. Fasting blood glucose (FBG) and plasma insulin were measured, and homeostatic model assessment of β cell function (HOMA-β) and insulin resistance (HOMA-IR) were determined. The histomorphology of pancreas islets was evaluated by haematoxylin and eosin staining. In palmitic acid (PA)-stressed INS-1 rat insulinoma cells, cell viability was assayed by an MTT method. Expression of the autophagy-related proteins LC3 I/II, p62, p-AMPK and p-mTOR in islet tissues and INS-1 cells was evaluated by western blotting or immunohistochemistry analysis.

RESULTS

The four main chemical constituents in MLE were identified as chlorogenic acid, rutin, isoquercitrin and quercitrin. MLE ameliorated hyperglycemia, insulin resistance and dyslipidemia of T2DM rats with prominent therapeutic effect. Further study indicated that MLE observably improved islet function, alleviated islet injury of T2DM rats, and inhibited PA-induced INS-1 cell death. On the other hand, MLE significantly induced autophagy in islet cells both in vivo and in vitro, and autophagy inhibitors abolished its therapeutic effect on T2DM rats and protective effect on islet cells. Apart from this, MLE markedly activated the AMPK/mTOR pathway in INS-1 cells, and the AMPK inhibitor prevented the autophagy induction ability of MLE.

CONCLUSION

Together, MLE could protect islet cells against dysfunction and death by inducing AMPK/mTOR-mediated autophagy in T2DM, and these findings provide a new perspective for understanding the treatment mechanism of Morus alba leaves against T2DM.

Qiliqiangxin alleviates Ang II-induced CMECs apoptosis by downregulating autophagy via the ErbB2-AKT-FoxO3a axis

Our previous work revealed the protective effect of Qiliqiangxin (QLQX) on cardiac microvascular endothelial cells (CMECs), but the underlying mechanisms remain unclear. We aimed to investigate whether QLQX exerts its protective effect against high-concentration angiotensin II (Ang II)-induced CMEC apoptosis through the autophagy machinery. CMECs were cultured in high-concentration Ang II (1 μM) medium in the presence or absence of QLQX for 48 h. We found that QLQX obviously inhibited Ang II-triggered autophagosome synthesis and apoptosis in cultured CMECs. QLQX-mediated protection against Ang II-induced CMEC apoptosis was reversed by the autophagy activator rapamycin. Specifically, deletion of ATG7 in cultured CMECs indicated a detrimental role of autophagy in Ang II-induced CMEC apoptosis. QLQX reversed Ang II-mediated ErbB2 phosphorylation impairment. Furthermore, inhibition of ErbB2 phosphorylation with lapatinib in CMECs revealed that QLQX-induced downregulation of Ang II-activated autophagy and apoptosis was ErbB2 phosphorylation-dependent via the AKT-FoxO3a axis. Activation of ErbB2 phosphorylation by Neuregulin-1β achieved a similar CMEC-protective effect as QLQX in high-concentration Ang II medium, and this effect was also abolished by autophagy activation. These results show that the CMEC-protective effect of QLQX under high-concentration Ang II conditions could be partly attributable to QLQX-mediated ErbB2 phosphorylation-dependent downregulation of autophagy via the AKT-FoxO3a axis.

Dietary Polyphenols in Metabolic and Neurodegenerative Diseases: Molecular Targets in Autophagy and Biological Effects

Polyphenols represent a group of secondary metabolites of plants which have been analyzed as potent regulators of multiple biological processes, including cell proliferation, apoptosis, and autophagy, among others. These natural compounds exhibit beneficial effects and protection against inflammation, oxidative stress, and related injuries including metabolic diseases, such as cardiovascular damage, obesity and diabetes, and neurodegeneration. This review aims to summarize the mechanisms of action of polyphenols in relation to the activation of autophagy, stimulation of mitochondrial function and antioxidant defenses, attenuation of oxidative stress, and reduction in cell apoptosis, which may be responsible of the health promoting properties of these compounds.

Punicalagin Inhibits Tert-Butyl Hydroperoxide-Induced Apoptosis and Extracellular Matrix Degradation in Chondrocytes by Activating Autophagy and Ameliorates Murine Osteoarthritis

Background

Osteoarthritis (OA) is a prevalent articular disorder and has no entirely satisfactory treatment. Punicalagin (PUG) is a polyphenol which has shown multiple pharmacological effects on various diseases. However, the role of PUG in the treatment of OA has not been well defined.

Methods

The effects of PUG on anti-oxidative stress, anti-apoptosis, extracellular matrix (ECM) degradation and autophagy were evaluated in chondrocytes through Western blot and immunofluorescence (IF) staining. Meanwhile, the effects of PUG on destabilization of the medial meniscus (DMM) model were also assessed in vivo by performing histopathologic analysis and IF staining.

Results

In vitro, PUG treatment not only increased the level of HO-1 and SOD1 against oxidative stress but also suppressed the expression of apoptotic proteins and inhibited ECM degradation. Meanwhile, PUG treatment activated autophagy and restores autophagic flux in chondrocytes after tert-butyl hydroperoxide (TBHP) insult, inhibition of autophagy by 3-methyladenine (3-MA) partly abrogated the protective effects of PUG on chondrocytes. In vivo, degeneration of the articular cartilage following DMM was also ameliorated by PUG treatment.

Conclusion

PUG prevents the progression of OA through inhibition of apoptosis, oxidative stress and ECM degradation in chondrocytes, which mediated by the activation of autophagy.

An Overview of the Mechanism of Penthorum chinense Pursh on Alcoholic Fatty Liver

Alcohol liver disease (ALD) caused by excessive alcohol consumption is a progressive disease, and alcohol fatty liver disease is the primary stage. Currently, there is no approved drug for its treatment. Abstinence is the best way to heal, but patients' compliance is poor. Unlike other chronic diseases, alcohol fatty liver disease is not caused by nutritional deficiencies; it is caused by the molecular action of ingested alcohol and its metabolites. More and more studies have shown the potential of Penthorum chinense Pursh (PCP) in the clinical use of alcohol fatty liver treatment. The purpose of this paper is to reveal from the essence of PCP treatment of alcohol liver mechanism mainly by the ethanol dehydrogenase (ADH) and microsomal ethanol oxidation system-dependent cytochrome P4502E1 (CYP2E1) to exert antilipogenesis, antioxidant, anti-inflammatory, antiapoptotic, and autophagy effects, with special emphasis on its mechanisms related to SIRT1/AMPK, KEAP-1/Nrf2, and TLR4/NF-κB. Overall, data from the literature shows that PCP appears to be a promising hepatoprotective traditional Chinese medicine (TCM).

Punicalagin Protects Human Retinal Pigment Epithelium Cells from Ultraviolet Radiation-Induced Oxidative Damage by Activating Nrf2/HO-1 Signaling Pathway and Reducing Apoptosis

The oxidative damage of the retinal pigment epithelium (RPE) is the early event that underlies the pathogenesis of maculopathies. Numerous studies have shown that punicalagin (PUN), a polyphenol present in pomegranate, can protect several cell types from oxidative stress. Our study aims to establish if PUN protects RPE from UV radiation-induced oxidative damage. We used an experimental model which involves the use of a human-RPE cell line (ARPE-19) exposed to UV-A radiation for 1, 3, and 5 h. ARPE-19 cells were pre-treated with PUN (24 h) followed by UV-A irradiation; controls were treated identically, except for UV-A. Effects of pre-treatment with PUN on cell viability, intracellular reactive oxygen species ROS levels, modulation of Nrf2 and its antioxidant target genes, and finally apoptosis were examined. We found that pre-treatment with PUN: (1) antagonized the decrease in cell viability and reduced high levels of ROS associated with UV-A-induced oxidative stress; (2) activated Nrf2 signaling pathway by promoting Nrf2 nuclear translocation and upregulating its downstream antioxidant target genes (HO-1 and NQO1); (3) induced an anti-apoptotic effect by decreasing Bax/Bcl-2 ratio. These findings provide the first evidence that PUN can prevent UV-A-induced oxidative damage in RPE, offering itself as a possible antioxidant agent capable of contrasting degenerative eye diseases.

Punicalagin Protects Diabetic Nephropathy by Inhibiting Pyroptosis Based on TXNIP/NLRP3 Pathway

Diabetic nephropathy is a diabetic complication caused by chronic inflammation. As the primary polyphenol in pomegranate, punicalagin is believed to have significant anti-inflammatory properties. In this study, we established a mice model for diabetes induced by high-fat diet (HFD)/ streptozotocin (STZ) to verify the protective effect of punicalagin in vivo. The results show that the blood urea nitrogen (BUN), serum creatinine (CREA), and the urine albumin to creatinine ratio (UACR) were significantly decreased in diabetic mice after punicalagin intervention, and the symptoms of glomerular interstitial hyperplasia and glomerular hypertrophy were alleviated. Pyroptosis is an essential manner of programmed cell death in the inflammatory response; the expression of pyroptosis-related proteins such as interleukin-1 (IL-1β), cysteinyl aspartate-specific protease-1 (caspase-1), gasdermin D (GSDMD), and nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain containing protein 3 (NLRP3) was decreased in our study, which proved that the administration of punicalagin for eight weeks can significantly inhibit pyroptosis in mice. In addition, punicalagin reduced high glucose-mediated protein expressions of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4) and alleviated mitochondria damage. Low expression of NOX4 inhibits the dissociation of thioredoxin (Trx) and thioredoxin-interacting protein (TXNIP) and the suppression of NLRP3 inflammasome activation. To summarize, our study provided evidence that punicalagin can alleviate diabetic nephropathy, and the effect is associated with downregulating the expression of NOX4, inhibiting TXNIP/NLRP3 pathway-mediated pyroptosis, suggesting its therapeutic implications for complications of diabetes.