Psoralea corylifolia L. Seed Extract Attenuates Methylglyoxal-Induced Insulin Resistance by Inhibition of Advanced Glycation End Product Formation

Bakuchiol, a natural constituent and its pharmacological benefits

Background and aims

Natural compounds extracted from medicinal plants have recently gained attention in therapeutics as they are considered to have lower Toxicity and higher tolerability relative to chemically synthesized compounds. Bakuchiol from Psoralea corylifolia L. is one such compound; it is a type of meroterpene derived from the leaves and seeds of Psoralea corylifolia plants. Natural sources of bakuchiol have been used in traditional Chinese and Indian medicine for centuries due to its preventive benefits against tumors and inflammation. It plays a strong potential role as an antioxidant with impressive abilities to remove Reactive Oxygen Species (ROS). This review has focused on bakuchiol's extraction, therapeutic applications, and pharmacological benefits.

Methods

A search strategy has been followed to retrieve the relevant newly published literature on the pharmacological benefits of bakuchiol. After an extensive study of the retrieved articles and maintaining the inclusion and exclusion criteria, 110 articles were finally selected for this review.

Results

Strong support of primary research on the protective effects via antitumorigenic, anti-inflammatory, antioxidative, antimicrobial, and antiviral activities are delineated.

Conclusions

From ancient to modern life, medicinal plants have always been drawing the attention of human beings to alleviate ailments for a healthy and balanced lifestyle. This review is a comprehensive approach to highlighting bona fide essential pharmacological benefits and mechanisms underlying their therapeutic applications.

Glyoxalase I Assay as a Possible Tool for Evaluation of Biological Activity of Antioxidant-Rich Plant Extracts

The health-promoting properties of natural plant bioactive compounds are mainly attributable to their ability to counteract oxidative stress. This is considered a major causative factor in aging and aging-related human diseases, in which a causal role is also ascribed to dicarbonyl stress. This is due to accumulation of methylglyoxal (MG) and other reactive dicarbonyl species, leading to macromolecule glycation and cell/tissue dysfunction. The glyoxalase (GLYI) enzyme, catalyzing the rate-limiting step of the GSH-dependent MG detoxification pathway, plays a key role in cell defense against dicarbonyl stress. Therefore, the study of GLYI regulation is of relevant interest. In particular, GLYI inducers are important for pharmacological interventions to sustain healthy aging and to improve dicarbonyl-related diseases; GLYI inhibitors, allowing increased MG levels to act as proapoptotic agents in tumor cells, are of special interest in cancer treatment. In this study, we performed a new in vitro exploration of biological activity of plant bioactive compounds by associating the measurement of their antioxidant capacity (AC) with the evaluation of their potential impact on dicarbonyl stress measured as capability to modulate GLYI activity. AC was evaluated using TEAC, ORAC, and LOX-FL methods. The GLYI assay was performed using a human recombinant isoform, in comparison with the recently characterized GLYI activity of durum wheat mitochondria. Different plant extracts were tested, obtained from plant sources with very high phytochemical content ('Sun Black' and wildtype tomatoes, black and 'Polignano' carrots, and durum wheat grain). Results showed high antioxidant properties of the tested extracts, associated with different modes (no effect, activation, and inhibition) and effectiveness in modulating both GLYI activity sources. Overall, results indicate the GLYI assay as an advisable and promising tool for researching plant foods as a source of natural antioxidant compounds acting as GLYI enzymatic regulators to be used for dietary management associated the treatment of oxidative/dicarbonyl-promoted diseases.

Salvianolic Acid B Alleviates Myocardial Ischemia Injury by Suppressing NLRP3 Inflammasome Activation via SIRT1-AMPK-PGC-1α Signaling Pathway

Salvianolic acid B (SalB) has been extensively investigated in our laboratory for myocardial ischemia (MI) disease. This study mainly aimed to illustrate the relationship between SIRT1 and the therapeutic effect of SalB on MI in rats and hypoxia damage in H9c2 cells. Furthermore, whether the antagonism of NLRP3 by SalB in the injuries mentioned above is related to SIRT1-AMPK-PGC-1α pathway-mediated mitochondrial biogenesis was further investigated. In vivo, 24 h after MI surgery, we found that SalB effectively reduced ST-segment elevation, myocardial infarct size enlargement, cardiac injury markers, myocardial structural abnormalities, and myocardial apoptotic cells in MI injury rats. In vitro, after 4 h of hypoxia exposure, SalB alleviated cell injury, inhibited the production of ROS and IL-1β, and prevented the loss of mitochondrial membrane potential (MMP). Besides, SalB downregulated the critical components of the NLRP3 inflammasome and upregulated the SIRT1-AMPK-PGC-1α signaling pathway-related molecules in myocardial tissues and H9c2 cells. However, all the above protective effects of SalB on MI could be offset by EX527. Taken together, our findings indicated that SalB could attenuate MI injury by targeting NLRP3, which is at least partially dependent on the SIRT1/AMPK/PGC-1α signaling pathway.

Selection and validation of reference genes for quantitative real-time PCR normalization in Psoralea corylifolia (Babchi) under various abiotic stress

Psoralea corylifolia L. is a popular herb and has long been used in traditional Ayurvedic and Chinese medicine owing to its extensive pharmacological activities, especially in the treatment of various shin diseases. To date, the systematic evaluation and selection of the optimum reference genes for gene expression analysis of P. corylifolia were not reported. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) is a method for gene expression quantification. Selecting appropriate reference genes is the prerequisite for accurate normalization of RT-qPCR results. This study assessed the expression stability of 10 candidate reference genes under different abiotic stresses. First, amplification primers for RT-qPCR were designed and received testing and optimization. Then, expression data from each candidate gene were evaluated based on three statistical algorithms, and their results were further integrated into a comprehensive ranking based on the geometric mean. Additionally, one target gene, i.e., 1-aminocyclopropane-1-carboxylate oxidase (ACO), was used to validate the effectiveness of the selected reference. Our analysis suggested that thioredoxin-like protein YLS8 (YLS8), TIP41-like family protein (TIP41), and cyclophilin 2 (CYP2) genes provided superior expression normalization under different abiotic stresses. Overall, this work constitutes the first effort to select optimal endogenous controls for RT-qPCR studies of gene expression in P. corylifolia. It also provides a reasonable normalization standard and basis for further analysis of the gene expression of bioactive components in P. corylifolia.

Crocin ameliorates MicroRNAs-associated ER stress in type 2 diabetes induced by methylglyoxal

OBJECTIVES

Methylglyoxal (MG) provokes endoplasmic reticulum (ER) stress in β-cells and triggers pancreatic β-cell dysfunction. Crocin has anti-diabetic properties. The present study investigated whether crocin prevented pancreas damages induced by MG.

MATERIALS AND METHODS

Diabetes was induced by MG administration (600 mg/kg/day, PO). On the fourteenth day, after proving hyperglycemia, crocin (15, 30, and 60 mg/kg) and metformin (MT) (150 mg/kg) were used for detoxification of MG until the end of the experiment. The animals were divided into 6 groups: 1) control, 2) diabetic by MG, 3) MG + crocin 15 mg/kg, 4) MG + crocin 30 mg/kg, 5) MG + crocin 60 mg/kg, and 6) MG + MT. The data were analyzed by one-way analysis of variance and significant differences were compared by Tukey and Bonferroni tests (P<0.05). Biochemical assays, antioxidant evaluation, and microRNAs expression associated with ER stress were assessed.

RESULTS

MG induced hyperglycemia, insulin resistance, and dyslipidemia (P<0.001). Crocin and MT significantly ameliorated β-cell function through reduction of fasting blood glucose, malondialdehyde levels (P<0.001), and significant elevation of anti-oxidant enzyme activity accompanied by regulation of glutathione and glyoxalase1-Nrf2 in MG induced diabetic mice. Crocin and MT significantly down-regulated microRNAs 204, 216b, 192, and 29a expression (P<0.001). Crocin (60 mg/kg) (P<0.01) and MT (P<0.001) could improve diameter of pancreatic islets in MG treated mice.

CONCLUSION

Crocin prevents the progression of diabetes through modulating ER stress-associated microRNAs and GLO1 activity with the helpful effects of glutathione and Nrf2.

Methylglyoxal reduces molecular responsiveness to 4 weeks of endurance exercise in mouse plantaris muscle

Endurance exercise triggers skeletal muscle adaptations, including enhanced insulin signaling, glucose metabolism, and mitochondrial biogenesis. However, exercise-induced skeletal muscle adaptations may not occur in some cases, a condition known as exercise-resistance. Methylglyoxal (MG) is a highly reactive dicarbonyl metabolite and has detrimental effects on the body such as causing diabetic complications, mitochondrial dysfunction, and inflammation. This study aimed to clarify the effect of methylglyoxal on skeletal muscle molecular adaptations following endurance exercise. Mice were randomly divided into 4 groups (n = 12 per group): sedentary control group, voluntary exercise group, MG-treated group, and MG-treated with voluntary exercise group. Mice in the voluntary exercise group were housed in a cage with a running wheel, while mice in the MG-treated groups received drinking water containing 1% MG. Four weeks of voluntary exercise induced several molecular adaptations in the plantaris muscle, including increased expression of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC1α), mitochondria complex proteins, toll-like receptor 4 (TLR4), 72-kDa heat shock protein (HSP72), hexokinase II, and glyoxalase 1; this also enhanced insulin-stimulated Akt Ser⁴⁷³ phosphorylation and citrate synthase activity. However, these adaptations were suppressed with MG treatment. In the soleus muscle, the exercise-induced increases in the expression of TLR4, HSP72, and advanced glycation end products receptor 1 were inhibited with MG treatment. These findings suggest that MG is a factor that inhibits endurance exercise-induced molecular responses including mitochondrial adaptations, insulin signaling activation, and the upregulation of several proteins related to mitochondrial biogenesis, glucose handling, and glycation in primarily fast-twitch skeletal muscle.

Urolithin A alleviates advanced glycation end-product formation by altering protein structures, trapping methylglyoxal and forming complexes

Urolithin A (UroA) is a first-in-class natural compound derived from the gut microbiota-derived metabolites of ellagitannins. This research for the first time evaluates the mechanisms of UroA inhibiting advanced glycation end-product (AGE) formation by fluorescence spectroscopy, molecular docking, liquid chromatography (LC) and LC-Oribitrap tandem mass spectrometry. The results indicated that UroA exhibited a good suppression effect on the formation of AGEs in human serum albumin (HSA)-fructose and HSA-methylglyoxal (MGO) systems. Further mechanism analysis revealed that UroA alleviated AGE formation by changing the conformational structure of HSA, trapping reactive MGO to form mono-MGO-UroA complexes, promoting the exposure of chromophores to a more hydrophobic micro-environment, and forming stable UroA-HSA complexes. UroA bound with HSA in an equimolar manner, the binding was an exothermic spontaneous process, subdomain IIIA was the preferred binding pocket, and hydrogen bonding, hydrophobic interactions and van der Waals forces were the major interaction forces. The number of glycation sites detected in glycated HSA was reduced by 1 and 2, respectively, when 181.82 and 363.64 μM UroA was added. These could provide an insight into the mechanism of UroA inhibiting HSA glycation, and highlight its value as a promising glycation inhibitor in the prevention of diabetic complications.

The benzofuran glycosides from the fruits of Psoralea corylifolia L

Six new glucosides of benzofuran (1-6), together with three known glucosides of benzofuran (8, 9, 14), nine flavonoids (12, 13, 15, 18, 19, 20, 21, 22 and 24), three coumarins (16, 17, 23) and four other-typic compounds (7, 10, 11 and 25) were isolated from the fruits of Psoralia corylifolia L. Their structures were elucidated by extensive spectroscopic methods. The biosynthesis pathway of benzofuran system was discussed. Besides, all isolated compounds and additional ring-opening derivatives of psoralen/isopsoralen (P-1, P-2, IP-1 and IP-2) were assayed for inhibition of nitric oxide (NO) production on lipopolysaccharides-induced RAW 264.7 macrophage cells. The results of the assay showed that the glycosides showed weaker or no effects, while most isolated non-glycoside compounds showed moderate or high activities. And the structure-activity relationships of non-glycoside compounds were discussed.

Effects of Psoralea corylifolia L. seed extract on AGEs-induced cell proliferation and fibrotic factor expression in mesangial cells

Diabetic nephropathy is a microvascular complication of diabetes that is characterized by mesangial expansion and thickening of the glomerular basement membrane. The production of advanced glycation end products (AGEs) increases in diabetic patients. Activation of the receptor of AGE (RAGE) signaling pathway induces mesangial expansion via the reactive oxygen species (ROS)-mediated production of pro-inflammatory and extracellular matrix molecules. The Psoralea corylifolia L. seed (PCS) is a widely used herbal medicine with various biological activities. The current study investigated the effect of PCS extract on mesangial cell proliferation and the RAGE signaling pathway in SV40 MES 13 cells. SV40 MES 13 cells were harvested after treatment with various concentrations of PCS extract at 10 µg/ml AGEs for 24 h. The results revealed that the PCS extract inhibited AGEs-induced mesangial cell proliferation and cyclin protein expression in a concentration-dependent manner. In addition, the AGEs-induced expression of fibrotic factors, such as transforming growth factor β, fibronectin and collagen, was reduced in mesangial cells after exposure to the PCS extract. The PCS extract also reduced RAGE expression and inhibited the expression of its downstream signaling pathways, such as NADPH oxidase, intracellular ROS and phospho-NF-κB. In conclusion, the data suggested that the PCS extract attenuated AGEs-induced renal mesangial cell proliferation and fibrosis via the suppression of oxidative stress and the downregulation of inflammatory and fibrotic factor expression.

Effects of crocin and metformin on methylglyoxal-induced reproductive system dysfunction in diabetic male mice

Objective

This study investigated the effect of crocin in methylglyoxal (MGO)-induced diabetic male mice.

Methods

Seventy 1-month-old male NMRI mice weighing 20–25 g were divided into seven groups (n=10): sham, MGO (600 mg/kg/day), MGO+crocin (15, 30, and 60 mg/kg/day), MGO+metformin (150 mg/kg/day), and crocin (60 mg/kg/day). MGO was administered orally for 30 days. Starting on day 14, after confirming hyperglycemia, metformin and crocin were administered orally. On day 31, plasma and tissue samples were prepared for experimental assessments.

Results

Blood glucose and insulin levels in the MGO group were higher than those in the sham group (p<0.001), and decreased in response to metformin (p<0.001) and crocin treatment (not at all doses). Testis width and volume decreased in the MGO mice and improved in the crocin-treated mice (p<0.05), but not in the metformin group. Superoxide dismutase levels decreased in diabetic mice (p<0.05) and malondialdehyde levels increased (p<0.001). Crocin and metformin improved malondialdehyde and superoxide dismutase. Testosterone (p<0.001) and sperm count (p<0.05) decreased in the diabetic mice, and treatment with metformin and crocin recovered these variables. Luteinizing hormone levels increased in diabetic mice (p<0.001) and crocin treatment (but not metformin) attenuated this increase. Seminiferous diameter and height decreased in the diabetic mice and increased in the treatment groups. Vacuoles and ruptures were seen in diabetic testicular tissue, and crocin improved testicular morphology (p<0.01).

Conclusion

MGO increased oxidative stress, reduced sex hormones, and induced histological problems in male reproductive organs. Crocin and metformin improved the reproductive damage caused by MGO-induced diabetes.

The Glyoxalase System in Age-Related Diseases: Nutritional Intervention as Anti-Ageing Strategy

The glyoxalase system is critical for the detoxification of advanced glycation end-products (AGEs). AGEs are toxic compounds resulting from the non-enzymatic modification of biomolecules by sugars or their metabolites through a process called glycation. AGEs have adverse effects on many tissues, playing a pathogenic role in the progression of molecular and cellular aging. Due to the age-related decline in different anti-AGE mechanisms, including detoxifying mechanisms and proteolytic capacities, glycated biomolecules are accumulated during normal aging in our body in a tissue-dependent manner. Viewed in this way, anti-AGE detoxifying systems are proposed as therapeutic targets to fight pathological dysfunction associated with AGE accumulation and cytotoxicity. Here, we summarize the current state of knowledge related to the protective mechanisms against glycative stress, with a special emphasis on the glyoxalase system as the primary mechanism for detoxifying the reactive intermediates of glycation. This review focuses on glyoxalase 1 (GLO1), the first enzyme of the glyoxalase system, and the rate-limiting enzyme of this catalytic process. Although GLO1 is ubiquitously expressed, protein levels and activities are regulated in a tissue-dependent manner. We provide a comparative analysis of GLO1 protein in different tissues. Our findings indicate a role for the glyoxalase system in homeostasis in the eye retina, a highly oxygenated tissue with rapid protein turnover. We also describe modulation of the glyoxalase system as a therapeutic target to delay the development of age-related diseases and summarize the literature that describes the current knowledge about nutritional compounds with properties to modulate the glyoxalase system.

Cudrania tricuspidata Root Extract Prevents Methylglyoxal-Induced Inflammation and Oxidative Stress via Regulation of the PKC-NOX4 Pathway in Human Kidney Cells

Diabetic nephropathy is a microvascular complication induced by diabetes, and methylglyoxal (MGO) is a reactive carbonyl species causing oxidative stress that contributes to the induction of inflammatory response in kidney cells. Cudrania tricuspidata (CT), cultivated in Northeast Asia, has been used as traditional medicine for treating various diseases, including neuritis, liver damage, and cancer. In this study, we determined whether a CT root extract (CTRE) can prevent MGO-induced reactive oxygen species (ROS) production and inflammation and assessed underlying mechanisms using a kidney epithelial cell line, HK-2. We observed that CTRE inhibited MGO-induced ROS production. Additionally, CTRE ameliorated the activation of MGO-induced inflammatory signaling pathways such as p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), and c-JUN N-terminal kinase (JNK). Consistent with these results, expressions of p-nuclear factor-kappa B (NFκB) and inflammatory cytokines, tumor necrosis factor-α, interleukin- (IL-) 1β, and IL-6, were decreased when compared with MGO-only exposed HK-2 cells. CTRE alleviated the MGO-induced decrease in nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and antioxidant enzyme mRNA expressions. MGO induced the expression of NADPH oxidase 4 (NOX4); CTRE pretreatment inhibited this induction. Further studies revealed that the NOX4 expression was inhibited owing to the suppression of MGO-induced protein kinase C (PKC) activation following CTRE treatment. Collectively, our data suggest that CTRE attenuates MGO-induced inflammation and oxidative stress via inhibition of PKC activation and NOX4 expression, as well as upregulating the Nrf2-antioxidant enzyme pathway in HK-2 cells.

Isobavachalcone ameliorates diabetic nephropathy in rats by inhibiting the NF-κB pathway

Isobavachalcone (ISO) exhibits good anti-inflammatory activity. We evaluated the renoprotective effects of ISO against diabetic nephropathy (DN). Diabetic rats established by the single injection of streptozotocin (STZ) were orally treated with ISO. The levels of serum creatinine (Scr), blood urea nitrogen (BUN), and 24 hr urinary protein were measured. In this study, ISO effectively ameliorated renal damage by reducing BUN, Scr, and 24 hr urinary protein and also improved kidney pathological appearances. ISO prevented STZ-caused apoptosis in the glomerular tissue in vivo and blocked the high glucose (HG)-induced growth inhibitory effect in human renal glomerular endothelial cells in vitro. Moreover, ISO reduced pro-inflammatory mediator production and blocked the NF-κB pathway in the damaged renal tissues and HG-treated HRGEC cells. Taken together, the results of this study indicate that ISO consumption might have significant beneficial effects on the DN and this action might be correlated with the modulation of the NF-κB pathway. PRACTICAL APPLICATIONS: ISO is an active compound from the dried ripe fruit of Psoralea corylifolia L. seed, which is traditionally served as a food ingredient in Asia. In this investigation, we observed the beneficial effects of ISO on a murine model with DN. Further research revealed that the protective action of ISO might be connected with its weak hypoglycaemic and notable anti-inflammatory effects. Our research data suggest that ISO-enriched food might be a good choice for people suffering from DN.

Effects and Mechanisms of Five Psoralea Prenylflavonoids on Aging-Related Diseases

During the aging process, senescent cells gradually accumulate in the organs; they secrete proinflammatory cytokines and other factors, collectively known as the senescence-associated secretory phenotype (SASP). SASP secretions contribute to “inflammaging,” which is a state of chronic, systemic, sterility, low-grade inflammatory microenvironment and a key risk factor in the development of aging-related diseases. Fructus psoraleae is a traditional Chinese medical herb best known for delaying aging and treating osteoporosis. Prenylflavonoids from fructus psoraleae are the main bioactive compounds responsible for its pharmacological applications, such as beaching, bavachinin, bavachalcone, isobavachalcone, and neobavaisoflavone. In previous decades, there have been some promising studies on the pharmacology of fructus psoraleae. Here, we focus on the anti-inflammatory and antiaging diseases of five psoralea prenylflavonoids, such as cardiovascular protection, diabetes and obesity intervention, neuroprotection, and osteoporosis, and discuss the mechanism of these active ingredients for better understanding the material basis and drug application of fructus psoraleae in Chinese medicine.