In vitro inhibitory effect of five natural sweeteners on α-glucosidase and α-amylase

A promising and efficacious approach to manage diabetes is inhibiting α-glucosidase and α-amylase activity. Therefore, the inhibitory activities of five natural sweeteners (mogrosides (Mog), stevioside (Ste), glycyrrhizinic acid (GA), crude trilobatin (CT), and crude rubusoside (CR)) against α-glucosidase and α-amylase and their interactions were evaluated in vitro using enzyme kinetics, fluorescence spectroscopy, Fourier infrared spectroscopy, and molecular docking. The inhibitor sequence was CT > GA > Ste, as GA competitively inhibited α-glycosidase activity while CT and Ste exhibited mixed inhibitory effects. Compared to a positive control acarbose, the inhibitory activity of CT was higher. For α-amylase, the mixed inhibitors CT, CR, and Mog and the competitive inhibitor Ste effectively inhibited the enzyme, with the following order: CT > CR > Ste > Mog; nevertheless, the inhibitors were slightly inferior to acarbose. Three-dimensional fluorescence spectra depicted that GA, CT, and CR bound to the hydrophobic cavity of α-glucosidase or α-amylase and changed the polarity of the hydrophobic amino acid-based microenvironment and structure of the polypeptide chain backbone. Infrared spectroscopy revealed that GA, CT, and CR could disrupt the secondary structure of α-glucosidase or α-amylase, which decreased enzyme activity. GA, trilobatin and rubusoside bound to amino acid residues through hydrogen bonds and hydrophobic interactions, changing the conformation of enzyme molecules to decrease the enzymatic activity. Thus, CT, CR and GA exhibit promising inhibitory effects against α-glucosidase and α-amylase.

Development of oral formulation of Lepidium seeds significantly decreases the high blood glucose levels in diabetic rats: in vitro formulation and in vivo antidiabetic performance

BACKGROUND

Lepidium sativum, Garden Cress (GC), seeds have a lot of natural molecules with a pronounced activity against different disorders. It was reported that GC seeds have the ability to lower the blood glucose level.

AIM

The aim of this work was to formulate GC seeds into oral tablets containing a fixed dose of the grounded seeds. Furthermore, the anti-diabetic performance of the prepared tablets was studied in the streptozotocin rats' model in comparison with positive control metformin.

METHODS

Micrometrics of GC grounded seeds with different excipients were investigated. Then, GC tablets were prepared via direct compression technique. GC tablets were characterized for their uniformity of dosage unit, friability, hardness, disintegration time, and in vitro release. The antidiabetic effect was studied in rats for a period of 28 days. Glycosylated hemoglobin, liver performance, and lipid levels include total cholesterol (TC), triglycerides (TGs), high-density lipoprotein (HDL), and low-density lipoprotein (LDL) were also estimated. In addition, histopathological study of liver and pancreas was also performed.

RESULTS

Prosolv®EasyTab produced tablets with higher hardness, lower disintegration time, and fast release. GC tablets significantly lower the elevated blood glucose level. In addition, they have antihyperlipidemic activity, hepatocellular protective role and restore the histology of the liver and pancreas.

CONCLUSION

GC tablets could be a promising alternative formulation to control the high blood glucose level in diabetic rats rather than chemically derivatized drugs.

Can Polyherbal Medicine be used for the Treatment of Diabetes? - A Review of Historical Classics, Research Evidence and Current Prevention Programs

Diabetes mellitus (DM), a chronic medical condition, has attained a global pandemic status over the last few decades affecting millions of people. Despite a variety of synthetic drugs available in the market, the use of herbal medicines for managing diabetes is gaining importance because of being comparatively safer. This article reviews the result of a substantial literature search on polyherbal formulations (PHFs) developed and evaluated with potential for DM. The accumulated data in the literature allowed us to enlist 76PHFs consisting of different parts of 147 plant species belonging to 58 botanical families. The documented plant species are laden with bioactive components with anti-diabetic properties and thus draw attention. The most favoured ingredient for PHFs was leaves of Gymnema sylvestre and seeds of Trigonella foenum-graecum used in 27 and 22 formulations, respectively. Apart from herbs, shilajit (exudates from high mountain rocks) formed an important component of 9 PHFs, whereas calcined Mytilus margaritiferus and goat pancreas were used in Dolabi, the most commonly used tablet form of PHF in Indian markets. The healing properties of PHFs against diabetes have been examined in both pre-clinical studies and clinical trials. However, the mechanism(s) of action of PHFs are still unclear and considered the pitfalls inherent in understanding the benefits of PHFs. From the information available based on experimental systems, it could be concluded that plant-derived medicines will have a considerable role to play in the control of diabetes provided the challenges related to their bioavailability, bioefficacy, optimal dose, lack of characterization, ambiguous mechanism of action, and clinical efficiency are addressed.

Anti-Glucotoxicity Effect of Phytoconstituents via Inhibiting MGO-AGEs Formation and Breaking MGO-AGEs

The therapeutic benefits of phytochemicals in the treatment of various illnesses and disorders are well documented. They show significant promise for the discovery and creation of novel medications for treating a variety of human diseases. Numerous phytoconstituents have shown antibiotic, antioxidant, and wound-healing effects in the conventional system. Traditional medicines based on alkaloids, phenolics, tannins, saponins, terpenes, steroids, flavonoids, glycosides, and phytosterols have been in use for a long time and are crucial as alternative treatments. These phytochemical elements are crucial for scavenging free radicals, capturing reactive carbonyl species, changing protein glycation sites, inactivating carbohydrate hydrolases, fighting pathological conditions, and accelerating the healing of wounds. In this review, 221 research papers have been reviewed. This research sought to provide an update on the types and methods of formation of methylglyoxal-advanced glycation end products (MGO-AGEs) and molecular pathways induced by AGEs during the progression of the chronic complications of diabetes and associated diseases as well as to discuss the role of phytoconstituents in MGO scavenging and AGEs breaking. The development and commercialization of functional foods using these natural compounds can provide potential health benefits.

Therapeutic role of kaempferol and myricetin in streptozotocin-induced diabetes synergistically via modulation in pancreatic amylase, glycogen storage and insulin secretion

Kaempferol and Myricetin alone have promising benefits on diabetes and related complications, yet the effectiveness of cotreating the two compounds on diabetes have not been studied. The existing investigation was to study the combined anti-diabetic effect of kaempferol and myricetin in Streptozotocin (STZ)-activated diabetes in rats. To evaluate the anti-diabetic activity, 36 Wistar rats were segregated into six groups; Normal, 50 mg/kg STZ-induced diabetes, and four (50 mg/kg kaempferol, 50 mg/kg myricetin, 25 mg/kg kaempferol + myricetin, and 5 mg/kg glibenclamide) compound-treated diabetic groups. The effects of co-treatment on parameters, glucose, insulin, lipid profile, liver enzymes, antioxidant biomarkers, and inflammatory cytokines were measured. The study revealed that combined treatment restored the assessed parameters including glucose levels, inflammatory cytokines, oxidative markers, and lipid and liver enzymes in diabetic rats. The results indicate that cotreatment of kaempferol and myricetin has a beneficial role against diabetes suggesting that cotreatment of these compounds can be used therapeutically in treating diabetes.

Biological Screening of Glycyrrhiza glabra L. from Different Origins for Antidiabetic and Anticancer Activity

BACKGROUND

Geographical variation may affect the phytochemistry as well as the biological activities of Glycyrrhiza glabra (licorice) root. Herein, a series of biological activities were performed to evaluate the impact of geographical origin on the biological potential of eight different licorice samples.

METHODOLOGY

Cell culture studies were performed for cytotoxicity (MCF7, HCT116, HepG2, and MRC5), glucose uptake assay (HepG2), and glutathione peroxidase activity (HepG2), whereas α-amylase inhibition activity was tested for antidiabetic potential.

RESULTS

The Indian sample was observed to be more cytotoxic against MCF7 (22%) and HCT116 (43%) with an IC₅₀ value of 56.10 (±2.38) μg/mL against the MCF7 cell line. The glucose uptake was seen with a mean value of 96 (±2.82) and a range of 92-101%. For glutathione peroxidase activity (GPx), the Syrian (0.31 ± 0.11) and Pakistani samples (0.21 ± 0.08) revealed a significant activity, whereas the Palestinian (70 ± 0.09) and Indian samples (68±0.06) effectively inhibited the α-amylase activity, with the lowest IC₅₀ value (67.11 ± 0.97) μg/mL for the Palestinian sample. The statistical models of PCA (principal component analysis) and K-mean cluster analysis were performed to correlate the geographical origin, extract yield, and biological activities for the eight licorice samples of different origins.

CONCLUSION

The licorice samples exhibited significant cytotoxic, GPx, and α-amylase inhibitory activity. The samples with higher extract yield showed more potential in these biological activities.

Analysis of the network pharmacology and the structure-activity relationship of glycyrrhizic acid and glycyrrhetinic acid

Licorice, a herbal product derived from the root of Glycyrrhiza species, has been used as a sweetening agent and traditional herbal medicine for hundreds of years. Glycyrrhizic acid (GL) and glycyrrhetinic acid (GA) are the most important active ingredients in licorice. Both GL and GA have pharmacological effects against tumors, inflammation, viral infection, liver diseases, neurological diseases, and metabolic diseases. However, they also exhibit differences. KEGG analysis indicated that licorice is involved in neuroactive ligand‒receptor interactions, while 18β-GA is mostly involved in arrhythmogenic right ventricular cardiomyopathy. In this article, we comprehensively review the therapeutic potential of GL and GA by focusing on their pharmacological effects and working mechanisms. We systemically examine the structure-activity relationship of GL, GA and their isomers. Based on the various pharmacological activities of GL, GA and their isomers, we propose further development of structural derivatives of GA after chemical structure modification, with less cytotoxicity but higher targeting specificity. More research is needed on the clinical applications of licorice and its active ingredients.

An Overview of Herbal-Based Antidiabetic Drug Delivery Systems: Focus on Lipid- and Inorganic-Based Nanoformulations

Diabetes is a metabolic pathology with chronic high blood glucose levels that occurs when the pancreas does not produce enough insulin or the body does not properly use the insulin it produces. Diabetes management is a puzzle and focuses on a healthy lifestyle, physical exercise, and medication. Thus far, the condition remains incurable; management just helps to control it. Its medical treatment is expensive and is to be followed for the long term, which is why people, especially from low-income countries, resort to herbal medicines. However, many active compounds isolated from plants (phytocompounds) are poorly bioavailable due to their low solubility, low permeability, or rapid elimination. To overcome these impediments and to alleviate the cost burden on disadvantaged populations, plant nanomedicines are being studied. Nanoparticulate formulations containing antidiabetic plant extracts or phytocompounds have shown promising results. We herein aimed to provide an overview of the use of lipid- and inorganic-based nanoparticulate delivery systems with plant extracts or phytocompounds for the treatment of diabetes while highlighting their advantages and limitations for clinical application. The findings from the reviewed works showed that these nanoparticulate formulations resulted in high antidiabetic activity at low doses compared to the corresponding plant extracts or phytocompounds alone. Moreover, it was shown that nanoparticulate systems address the poor bioavailability of herbal medicines, but the lack of enough preclinical and clinical pharmacokinetic and/or pharmacodynamic trials still delays their use in diabetic patients.

BChE inhibitors from marine organisms - A review

Acetylcholine is a key neurotransmitter for brain and muscle function, that has its levels decreased in the brain of people with Alzheimer's Disease (AD). Cholinesterase inhibitors are medicines that decrease the breakdown of acetylcholine, through the inhibition of acetyl- and butyrylcholinesterase enzymes. Despite the fact that butyrylcholinesterase activity rises with the disease, while acetylcholinesterase activity declines, the cholinesterase inhibitors that are currently commercialized inhibit either acetylcholinesterase or both enzymes. The development of selective butyrylcholinesterase inhibitors is a promising strategy in the search for new drugs acting against AD. The marine environment is a rich source of molecules with therapeutic potential, which can provide compounds more easily than traditional methods, with reduced toxicity risks compared to synthetic molecules. This review comprises articles from 2003 to 2020, that assessed the butyrylcholinesterase inhibitory activities from marine organisms, considering their crude extracts and isolated compounds. Part of the articles reported a multi-target activity, inhibiting also other AD-related enzymes. Some of the marine compounds reported here have shown an excellent potential for butyrylcholinesterase inhibition compared to standard inhibitors. Further studies of some compounds reported here may lead to the development of a new treatment for AD.

Glycyrrhizin ameliorates vascular endothelial cell senescence by inhibiting HMGB1 in HFD/STZ-induced diabetic rats and human umbilical vein endothelial cells

The senescence and dysfunction of vascular endothelial cells are important features of diabetic vascular disease. High mobility group box-1(HMGB1) may be involved in vascular injury in response to high glucose. Glycyrrhizin (GL) is an HMGB1 inhibitor that significantly reduces HMGB1. However, the relationship between HMGB1 and vascular ageing in diabetes is not clear, the protective mechanism of GL against vascular injury in type 2 diabetes mellitus (T2DM) is unclear too. This study aims to examine the role of HMGB1 in vascular endothelial cell senescence and the protective effects of GL on vascular aging in high fat diet/streptozotocin (HFD/STZ) induce type 2 diabetic rats.After induction of diabetes, GL (150 mg/kg/d) was treated by gavage for 4 weeks. Results showed that compared with the Control group, the serum level of HMGB1 was increased in rats with type 2 diabetes, while the expression of HMGB1 mRNA and protein in the thoracic aorta was upregulated, with a decrease in endothelium-dependent vasodilation function and an increase in aging degree in the thoracic aorta. However, the above indicators were significantly improved after GL treatment. In HUVECs, we found that treated with HMGB1 (50, 100 and 200 ng/ml) for 48 h induced cells senescence and GL (50, 100 mg/L) significantly inhibited high-glucose-induced endothelial cell senescence, meanwhile GL (50, 100 mg/L) significantly inhibited the high-glucose-induced HMGB1 release and upregulated p53 expression. In conclusion, GL as an HMGB1 inhibitor, attenuates endothelium-dependent relaxation impairment and vascular ageing in an animal model of diabetes and high-glucose-induced endothelial cell senescence.

Effects of licorice root supplementation on liver enzymes, hepatic steatosis, metabolic and oxidative stress parameters in women with nonalcoholic fatty liver disease: A randomized double-blind clinical trial

This study aimed to evaluate the effects of licorice root supplementation on liver enzymes, hepatic steatosis, metabolic and oxidative stress parameters in women with nonalcoholic fatty liver disease (NAFLD). In this randomized double-blind, placebo-controlled trial, 60 women with NAFLD were selected and randomly assigned into 2 groups to take 1,000 mg/day powder of licorice root extract or placebo for 12 weeks. In addition, all the patients were advised to follow a weight loss diet and healthy lifestyle. The plasma levels of liver enzymes, glycemic indices, lipid profile, oxidative stress parameters, as well as hepatic steatosis were measured at the beginning and end of the study. Through the 12-weeks period of supplementation, women who received powder of licorice root experienced a statistically significant improvement in alanine aminotransferase (p < .001), insulin (p = .002), insulin resistance (p = .003), malondialdehyde (p < .001) serum levels, and ultrasonographic findings of liver steatosis (p < .001), compared to the placebo group. In conclusion, licorice root supplementation in addition to gradual weight loss and lifestyle modification is superior to lifestyle modification alone for the treatment of NAFLD.

Licorice Extract Supplementation Affects Antioxidant Activity, Growth-Related Genes, Lipid Metabolism, and Immune Markers in Broiler Chickens

The objective of this study was to evaluate the Glycyrrhiza glabra effect on growth performance, blood parameters, antioxidant and lysosomal activity, histology and immunohistochemistry of liver and intestine, and the gene expression profile of broiler chickens. A total of 180 Cobb500 broiler chicks (one-week-old) were used in this study. Chicks were distributed randomly into three treatment groups; the first group received drinking water without any supplementation (control group). In contrast, birds in groups 2 and 3 received licorice supplementation in drinking water with 0.4 and 0.8 g licorice/liter, respectively. Results revealed that licorice at a 0.4 g/L of water level improved body weight, weight gain, feed intake, and FCR. Licorice also exhibits a broad range of biological activities such as hypolipidemic, hypoglycemic, hepatoprotective, immunostimulant, and antioxidant effects. The morphometric analysis of different parameters of the intestine revealed a significant increase in the intestinal villi length, width, and villi length/crypt depth in the group supplemented with licorice 0.4 gm/L compared to other groups. The number of CD3 positive in both duodenum and ileum was increased in the licorice 0.4 gm/L group compared to other groups. The expression of growth-related genes was significantly increased with licorice supplementation and modulation of the lipid metabolism genes in the liver and upregulated to the mRNA expression of both superoxide dismutase (SOD1) and Catalase (CAT). Our results revealed that licorice supplementation increased the growth performance of broiler chickens and impacted the birds' antioxidant activity through modulation of the growth-related genes, lipid metabolic markers, and antioxidant-related pathways.

Type 2 diabetes mellitus-associated cognitive dysfunction: Advances in potential mechanisms and therapies

Type 2 diabetes (T2D) and its target organ injuries cause distressing impacts on personal health and put an enormous burden on the healthcare system, and increasing attention has been paid to T2D-associated cognitive dysfunction (TDACD). TDACD is characterized by cognitive dysfunction, delayed executive ability, and impeded information-processing speed. Brain imaging data suggest that extensive brain regions are affected in patients with T2D. Based on current findings, a wide spectrum of non-specific neurodegenerative mechanisms that partially overlap with the mechanisms of neurodegenerative diseases is hypothesized to be associated with TDACD. However, it remains unclear whether TDACD is a consequence of T2D or a complication that co-occurs with T2D. Theoretically, anti-diabetes methods are promising neuromodulatory approaches to reduce brain injury in patients with T2D. In this review, we summarize potential mechanisms underlying TDACD and promising neurotropic effects of anti-diabetes methods and some neuroprotective natural compounds. Constructing screening or diagnostic tools and developing targeted treatment and preventive strategies would be expected to reduce the burden of TDACD.

Paracrine signal emanating from stressed cardiomyocytes aggravates inflammatory microenvironment in diabetic cardiomyopathy

Myocardial inflammation contributes to cardiomyopathy in diabetic patients through incompletely defined underlying mechanisms. In both human and time-course experimental samples, diabetic hearts exhibited abnormal ER, with a maladaptive shift over time in rodents. Furthermore, as a cardiac ER dysfunction model, mice with cardiac-specific p21-activated kinase 2 (PAK2) deletion exhibited heightened myocardial inflammatory response in diabetes. Mechanistically, maladaptive ER stress-induced CCAAT/enhancer-binding protein homologous protein (CHOP) is a novel transcriptional regulator of cardiac high-mobility group box-1 (HMGB1). Cardiac stress-induced release of HMGB1 facilitates M1 macrophage polarization, aggravating myocardial inflammation. Therapeutically, sequestering the extracellular HMGB1 using glycyrrhizin conferred cardioprotection through its anti-inflammatory action. Our findings also indicated that an intact cardiac ER function and protective effects of the antidiabetic drug interdependently attenuated the cardiac inflammation-induced dysfunction. Collectively, we introduce an ER stress-mediated cardiomyocyte-macrophage link, altering the macrophage response, thereby providing insight into therapeutic prospects for diabetes-associated cardiac dysfunction.

Liposome-encapsulated glycyrrhizin alleviates hyperglycemia and glycation-induced iron-catalyzed oxidative reactions in streptozotocin-induced diabetic rats

Glycyrrhizin, a bioactive constituent of Glycyrrhiza glabra has been reported to ameliorate diabetes. Here, the effects of liposome-encapsulated glycyrrhizin on STZ-induced diabetes and associated oxidative stress were investigated. Wistar rats were grouped as control (NC, received placebo), diabetic (DC, STZ-induced), diabetic treated with free glycyrrhizin (DTG, 3 i.v. doses, 1.6 mg/0.5 ml), empty liposomes (DTl, 3 i.v. doses), and liposome-encapsulated glycyrrhizin (DTbd, 3 i.v. doses, 1.6 mg/0.5 ml). Serum glucose, insulin, intraperitoneal glucose tolerance test and glycohemoglobin were estimated. Free iron and iron-mediated oxidative stress were examined. Histological examinations of the kidney and liver were performed. Liposomal-glycyrrhizin treatment caused significant improvement of hyperglycemia (DC vs. DTbd p < .05), glucose intolerance (DC vs. DTG p < .01 and DC vs. DTbd p < .05), insulin (DC vs. DTG p < .1, DTbd vs. DC p < .05 and DTbd vs. DTG p < .1) and glycohemoglobin (DC vs. DTG p < .1 and DC vs. DTbd p < .05) levels in the DTbd group. Alleviation of free iron release (DC vs. DTbd p < .05), lipid peroxidation (DC + H₂O₂ vs. DTbd + H₂O₂ p < .05), deoxyribose (DC + H₂O₂ vs. DTbd + H₂O₂, p < .05), and DNA degradation occurred in the DTbd group. The abnormalities of the kidney and liver were abolished in the DTbd group. The inhibitory effects were more pronounced compared to free glycyrrhizin. Liposome-encapsulated glycyrrhizin treatment caused inhibition of diabetic complications through its antioxidant effects and can be exploited for effective treatment of diabetes.

Antiproliferative and apoptotic potential of Glycyrrhizin against HPV16+ Caski cervical cancer cells: A plausible association with downreguation of HPV E6 and E7 oncogenes and Notch signaling pathway

Cervical cancer (CCa) is the second most frequent carcinoma in females and human papilloma virus (HPV) oncoproteins are regarded as one of the critical etiological agent. Despite recent advances in screening and management of CCa, still it remains the deadliest carcinoma as advanced and metastatic stages are mostly incurable. This urges for the development of newer therapeutic interventions. The current was aimed to investigate the antiproliferative and apoptotic potential of glycyrrhizin (Gly) against HPV16⁺ CaSki CCa cells. Our findings substantiated that Gly exerted antiproliferative effects on the CaSki cells by obstructing their proliferation rate. Gly substantially enhanced apoptosis in Caski cells in a dose-dependent manner via augmenting the generation of ROS, DNA fragmentation and disruption of the mitochondrial membrane potential. Gly mediated apoptosis in CaSki cells was found to be due to activation of caspase-8 and capsase-9 along with the modulation of pro-and anti-apoptotic gene expression. Moreover, Gly halts the progression of CaSki cells at G₀/G₁ phase which was found to be due to reduced expression of cyclin D1 and cyclin-dependent kinase 4 (CDK4) along with the enhanced expression of CDK inhibitor p21^Cip1. Further, Gly downregulates the expression of HPV oncoproteins (E6 & E7) along with the inhibition of Notch signaling pathway. Taken together, Gly represents as a potential therapeutic modality for CCa which could rapidly be translated for clinical studies.

Glycyrrhiza glabra alcoholic root extract ameliorates hyperglycemia, hyperlipidemia, and glycation-induced free iron-mediated oxidative reactions

Hyperglycemia-associated oxidative stress leads to various pathophysiological complications in diabetes mellitus. Here, the effects of Glycyrrhiza glabra (G. glabra) root extract of streptozotocin (STZ)-induced diabetic changes and the associated free iron-mediated oxidative reactions were investigated. The animals were divided into five group, Group 1: Control (NC received buffer); Group 2: STZ-induced (DC); Group 3: Control treated with G. glabra root extract (NT, 60 mg/Kg b.w daily for 1 month); Group 4: Diabetic treated with the extract (60 mg/Kg b.w daily for 1 month); Group 5: Diabetic treated with glibenclamide (DTG, 8.6 mg/Kg b.w for 1 month). STZ (i) induced hyperglycemia, abnormal intraperitoneal glucose tolerance test (IPGTT), increased HbA_1c and decreased plasma insulin levels (ii) hyperlipidemia (iii) lowered antioxidant enzyme activities (iv) diminished RBC membrane fluidity (v) enhanced hemoglobin glycation-induced iron release and associated free radical reactions. Treatment with the extract resulted in significant reversal of hyperglycemia (DC: 205.0 ± 7.0 mg/dl vs. DT: 87.5 ± 4.5 mg/dl, p < .05); HbA_1c (DC: 11.5 ± 2.0 vs. DT: 7.5 ± 0.8 vs. DT: 7.5 ± 0.8, p < .05); insulin (DC: 0.3 ± 0.06 vs. DT: 1.25 ± 0.15 μgm/L, p < .05); free iron (DC: 150.4 ± 7.07 vs. DT: 98.8 ± 7.7 μgm/gm of Hb, p < .05); TBARS (DC + H₂ O₂ : 24.62 ± 11.30 vs. DC + H₂ O₂ : 9.82 ± 2.56 mmoles/h, p < .05); carbonyl (DC: 40.40 ± 1.57 vs. DT: 25.50 ± 1.12 mmoles/g of Hb, p < .05) levels and β-cell count/pancreatic islet (DC: 85 ± 15 vs. DT: 125 ± 20, p < .05). Thus, G. glabra extract is quite effective against hyperglycemia and the associated free iron-mediated oxidative stress. PRACTICAL APPLICATIONS: Chronic use of oral hypoglycemic synthetic drugs may produce side effects and drug resistance. Recently, various plant extracts are being researched to explore their antihyperglycemic potential. Here, the effects of this alcoholic powdered root extract on STZ-induced diabetic changes and associated oxidative stress, including hemoglobin-induced free iron-mediated oxidative reactions were examined. The STZ-induced diabetic changes and hemoglobin-glycation-induced free iron-mediated oxidative reactions were alleviated in the Wistar rats after 1-month of treatment with the extract. We have also reported previously that glycyrrhizin, a bioactive constituent of Glycyrrhiza glabra root inhibits peroxidase, esterase activities of hemoglobin and hemoglobin-mediated oxidative damage without affecting oxygen-binding capacity of the protein. This preclinical work further substantiates the potential therapeutic use of the G. glabra whole root extract in the treatment of diabetes mellitus.

Indole- and Pyrazole-Glycyrrhetinic Acid Derivatives as PTP1B Inhibitors: Synthesis, In Vitro and In Silico Studies

Regulating insulin and leptin levels using a protein tyrosine phosphatase 1B (PTP1B) inhibitor is an attractive strategy to treat diabetes and obesity. Glycyrrhetinic acid (GA), a triterpenoid, may weakly inhibit this enzyme. Nonetheless, semisynthetic derivatives of GA have not been developed as PTP1B inhibitors to date. Herein we describe the synthesis and evaluation of two series of indole- and N-phenylpyrazole-GA derivatives (4a-f and 5a-f). We measured their inhibitory activity and enzyme kinetics against PTP1B using p-nitrophenylphosphate (pNPP) assay. GA derivatives bearing substituted indoles or N-phenylpyrazoles fused to their A-ring showed a 50% inhibitory concentration for PTP1B in a range from 2.5 to 10.1 µM. The trifluoromethyl derivative of indole-GA (4f) exhibited non-competitive inhibition of PTP1B as well as higher potency (IC₅₀ = 2.5 µM) than that of positive controls ursolic acid (IC₅₀ = 5.6 µM), claramine (IC₅₀ = 13.7 µM) and suramin (IC₅₀ = 4.1 µM). Finally, docking and molecular dynamics simulations provided the theoretical basis for the favorable activity of the designed compounds.

Methylglyoxal-derived hemoglobin advanced glycation end products induce apoptosis and oxidative stress in human umbilical vein endothelial cells

The presence of excess glucose promotes hemoglobin glycation via the biochemical modification of hemoglobin by dicarbonyl products. However, the precise effects of Hb-AGEs in human umbilical vein endothelial cells (HUVECs) are not known to date. Therefore, we investigated the tentative effects of Hb-AGEs in HUVECs. Initially, we used the AGE formation assay to examine the selectivity of MGO toward various proteins. Among all proteins, MGO-Hb-AGEs formation was higher compared to the formation of other dicarbonyl-mediated AGEs. Our next data demonstrated that treatment with 0.5 mg/mL of Hb-AGEs-4w significantly reduced cell viability in HUVECs. Further, we evaluated the role of MGO in conformational and structural changes in Hb. The results showed that Hb demonstrated a highly altered conformation upon incubation with MGO. Moreover, Hb-AGEs-4w treatment strongly increased ROS production, and decreased mitochondrial membrane potential in HUVECs, and moderately reduced the expression of phosphorylated forms of p-38 and JNK. We observed that Hb-AGEs-4w treatment increased the number of apoptotic cells and the Bax/Bcl-2 ratio and cleaved the nuclear enzyme PARP in HUVECs. Finally, Hb-AGEs also inhibited migration and proliferation of HUVECs, thus be physiologically significant in endothelial dysfunction. Taken together, our data suggest that Hb-AGEs may play a critical role in inducing vascular endothelial cell damage. Therefore, this study may provide a plausible explanation for the potential Hb-AGEs in human endothelial cell dysfunction of diabetic patients.

Glycyrrhizic Acid: A Natural Plant Ingredient as a Drug Candidate to Treat COVID-19

The total number of cumulative cases and deaths from the COVID-19 pandemic caused by SARS-CoV-2 is still increasing worldwide. Although many countries have actively implemented vaccination strategies to curb the epidemic, there is no specific efficient therapeutic drug for this virus to effectively reduce deaths. Therefore, the underappreciated macromolecular compounds have become the spotlight of research. Furthermore, the medicinal compounds in plants that provide myriad possibilities to treat human diseases have become of utmost importance. Experience indicates that Traditional Chinese medicine effectively treats SARS and has been used for treating patients with COVID-19 in China. As one of the world's oldest herbal remedies, licorice is used for treating patients with all stages of COVID-19. Glycyrrhizic acid (GA), the main active compound in licorice, has been proven effective in killing the SARS virus. Meanwhile, as a natural plant molecule, GA can also directly target important protein structures of the SARS-CoV-2 virus and inhibit the replication of SARS-CoV-2. In this review, we summarized the immune synergy of GA and its potential role in treating COVID-19 complications. Besides, we reviewed its anti-inflammatory effects on the immune system and its positive effects in cooperation with various drugs to fight against COVID-19 and its comorbidities. The purpose of this review is to elucidate and suggest that GA can be used as a potential drug during COVID-19 treatment.

Cytotoxicity, Anti-diabetic, and hepato-protective potential of Ajuga bracteosa-conjugated silver nanoparticles in Balb/c mice

BACKGROUND

Ajuga bracteosa is a traditional herb used against various diseases.

OBJECTIVE

Current research aimed to investigate the anti-diabetic and hepato-protective effect of green synthesized silver nanoparticles (ABAgNPs) using Ajuga bracteosa aqueous extract (ABaqu).

METHODS

In vitro anti-diabetic and cytotoxic effects were carried out via α- glucosidase inhibition, brine shrimp lethality, and protein kinase inhibition assays. For in vivo screening of 200 mg/kg and 400 mg/kg of both ABAgNPs and ABaqu in alloxan-induced and CCl4-induced Swiss albino mice were used. Liver and kidney functional markers, hematology, and histopathological studies were carried out after 14 days of administration.

RESULTS

In vivo antidiabetic and anti-cancerous effects showed valuable anti-hyperglycemic and hepato-protective potential when mice were treated with ABaqu and ABAgNPs. A significant reduction in the blood glucose level was recorded when ABaqu and ABAgNPs were administrated orally compared to Glibenclamide treated group. Significant reduction in ALT, AST, ALP, urea, uric acid, and creatinine was recorded in ABaqu and ABAgNPs treated diabetic mice. The hepato-protective findings indicated that ALT, ALP, AST were elevated in CCl4-induced mice while declined in both ABAgNPs and ABaqu treated CCl4-induced mice. Histopathological examination revealed that ABAgNPs have hepato-protective activity.

CONCLUSION

It was concluded that ABAgNPs and ABaqu possessed strong anti-diabetic and hepato-protective phytoconstituents which could be used in the prevention of diseases.

Hypoglycemic activity of the ethyl acetate extract from Smilax glabra Roxb in mice: Biochemical and histopathological studies

Objectives

This research was carried out to investigate the hypoglycemic activity of the ethyl acetate (EtOAc) extract from the roots of Smilax glabra Roxb, which strongly exhibit inhibitory activity against α-glucosidase and α-amylase on in vivo type 2 diabetic model.

Materials and Methods

Column chromatography combined with crystallization was used to isolate the active fraction and compounds. Chemical structures of the compounds were determined based on the analysis of the spectroscopic data and comparison with the literature data. The α-glucosidase inhibitory activity (AGI) and the α-amylase inhibitory activity (AAI) were determined quantitatively spectrophotometrically using p-nitrophenyl α-D-glucopyranoside and soluble starch as substrates, respectively. The hypoglycemic activity was examined by evaluating its effects on glucose and insulin levels, insulin resistance, and histopathology of the pancreatic islets and livers in diabetic induced mice administrated with nicotinamide-streptozotocin.

Results

The EtOAc extract and the bioactive compounds astilbin and 5-O-caffeoylshikimic acid in the extract were isolated and confirmed in structures, AGI, and AAI. The treatment at the doses of 500 and 1000 µg/kg of body weight reduced blood glucose levels down to the physiological level of the physical controls in the diabetic mice after two weeks (P<0.05). Moreover, the treatment improved insulin sensitivity. Histopathology analysis showed recovering effects in the size of the pancreatic islets and no damaging effects on the liver after treatment compared with the control group.

Conclusion

Our data suggest that the EtOAc extract possesses hypoglycemic activity and has an antidiabetic potential for therapeutic applications.

Advances in Pharmacological Activities and Mechanisms of Glycyrrhizic Acid

Licorice (Glycyrrhiza glabra L.) is widely regarded as an important medicinal plant and has been used for centuries in traditional medicine because of its therapeutic properties. Studies have shown that metabolites isolated from licorice have many pharmacological activities, such as antiinflammatory, anti-viral, participation in immune regulation, anti-tumor and other activities. This article gives an overview of the pharmacological activities and mechanisms of licorice metabolites and the adverse reactions that need attention. This review helps to further investigate the possibility of licorice as a potential drug for various diseases. It is hoped that this review can provide a relevant theoretical basis for relevant scholars' research and their own learning.

The anti-diabetic activity of licorice, a widely used Chinese herb

ETHNOPHARMACOLOGICAL RELEVANCE

A great deal of valuable experience has been accumulated in the traditional Chinese medicine (TCM) system for the treatment of "Xiaoke" disease which is known as diabetes mellitus now. As the most-commonly used Chinese herb, licorice has been used in TCM for more than two thousand years. It is often used in combination with other herbs to treat metabolic disorders, especially diabetes mellitus.

AIM OF THE STUDY

To summarize the characteristics, mechanisms, and clinical use of licorice and its active components for treating diabetes mellitus.

METHODS

PubMed, Web of Science, Research Gate, Science Direct, Google Scholar, and Academic Journals were used as information sources by the inclusion of the search terms 'diabetes', 'licorice', 'licorice extracts', 'flavonoids', 'triterpenoids', and their combinations, mainly from 2005 to 2019.

RESULTS

Licorice extracts, five flavonoids and three triterpenoids isolated from licorice possess great antidiabetic activities in vivo and in vitro. This was done by several mechanisms such as increasing the appetency and sensitivity of insulin receptor site to insulin, enhancing the use of glucose in different tissues and organs, clearing away the free radicals and resist peroxidation, correcting the metabolic disorder of lipid and protein, and improving microcirculation in the body. Multiple signaling pathways, including the PI3K/Akt, AMPK, AGE-RAGE, MAPK, NF-кB, and NLRP3 signaling pathways, are targets of the licorice compounds.

CONCLUSION

Licorice and its metabolites have a great therapeutic potential for the treatment of diabetes mellitus. However, a better understanding of their pharmacological mechanisms is needed for evaluating its efficacy and safety.

The renoprotective effect of glycyrrhizic acid in insulin-resistant rats exposed to aluminum involves the inhibition of TLR4/NF-κB signaling pathway

Aluminum is well recognized as a nephrotoxic agent. Its hazardous effects arise from the high risk of daily exposure. The consumption of fructose also represents a critical health issue that might negatively impact different organs, including the kidneys. To pursue our previous work, this study aimed to investigate the potential renoprotective effects of glycyrrhizic acid (GLYA) on aluminum-induced nephrotoxicity in insulin-resistant rats. Insulin resistance (IR) was induced by adding fructose (10%) in drinking water for 18 weeks. Male Wistar rats were divided into five groups: control (CTRL), aluminum chloride (ALM, 34 mg/kg/day), fructose (FRCT), aluminum plus fructose (AL/FR), and GLYA (rats received AL/FR and treated with 40 mg/kg GLYA daily). AL/FR resulted in abnormal renal function tests and renal tissue injury. This was associated with increased oxidative stress and inflammation in the renal tissue. Moreover, the expressions of the toll-like receptor 4 (TLR4) and its adaptor proteins were increased in AL/FR group. The administration of GLYA mollified AL/FR-induced renal injury, oxidative stress, activation of the TLR4 signaling pathway, and inflammation. In conclusion, we provide evidence for the promising renoprotective effect of GLYA against AL/FR-induced kidney damage in rats. The renoprotection is attributed to the suppression of oxidative stress and inhibition of the TLR4/NF-κB signaling pathway in the kidneys.

Dacryodes edulis (G. Don) H.J. Lam modulates glucose metabolism, cholinergic activities and Nrf2 expression, while suppressing oxidative stress and dyslipidemia in diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Dacryodes edulis L. is an evergreen tree indigenous to western and eastern Africa which is utilized for nutritional and medicinal purposes. Folklorically, different parts of the tree are used in treating and managing diabetes and its complications.

AIMS

The antidiabetic effect of the butanol fraction of D. edulis ethanol extract (BFDE) was studied in fructose-streptozotocin induced type 2 diabetic rats.

METHODS

The ethanol extract was fractionated to yield the hexane, dichloromethane, ethyl acetate, butanol and aqueous fractions. The in vitro antidiabetic activities of the fractions were determined by their ability to inhibit α-glucosidase activity. BDFE was the most active and showed no cytotoxic effect while stimulating glucose uptake in 3T3-L1 adipocytes. Thus, selected for in vivo study. Diabetic rats were grouped into 4. The negative control group was administered water only, another group was treated with metformin (200 mg/kg bodyweight), while the other groups were administered BDFE at 150 and 300 mg/kg bodyweight respectively. Two other groups consisting of normal rats were given water and BFDE (300 mg/kg bodyweight) respectively, with the former serving as normal control. After 6 weeks of intervention, the rats were humanely sacrificed using appropriate anaesthesia.

RESULTS

Treatment with the fraction significantly (p < 0.05) reduced the blood glucose level of the diabetic rats, with concomitant increase in serum insulin secretion. It also caused significant (p < 0.05) elevation of reduced glutathione level, superoxide dismutase, catalase, α-amylase, and ATPase activities, with concomitant depletion in myeloperoxidase activity, NO and MDA levels of the serum and pancreas. The pancreatic morphology and β-cell function were significantly improved in BFDE-treated rats, with restoration of the pancreatic capillary networks. Treatment with BFDE significantly (p < 0.05) inhibited the activities of glycogen phosphorylase, fructose 1,6 biphosphatase, glucose 6 phosphatase, and acetylcholinesterase, while suppressing the expression of Nrf2. HPLC analysis revealed the presence of gallic acid, vanillic acid, vanillin, and (-)-epicatechin in the fraction.

CONCLUSION

These results portray the antidiabetic and antioxidative properties of BFDE, which may be a synergistic consequence of the identified phenolics.

A Novel Approach Based on Metabolomics Coupled With Intestinal Flora Analysis and Network Pharmacology to Explain the Mechanisms of Action of Bekhogainsam Decoction in the Improvement of Symptoms of Streptozotocin-Induced Diabetic Nephropathy in Mice

Bekhogainsam decoction (BHID), a representative prescription for the treatment of diabetes mellitus (DM) and diabetic complications in both traditional Korean and Chinese medicine, was examined for its ability to ameliorate diabetic nephropathy (DN), and its mechanism of action was evaluated by metabolomics, gut microbiota, and network pharmacology. In this study, male specific pathogen-free C57BL/6 mice were intraperitoneally injected with streptozotocin (STZ, 100 mg/kg) once per day for 3 days consecutively, and were then orally administered BHID at 100 and 500 mg/kg, and metformin at 250 mg/kg once per day for 4 weeks. Our results showed that the administration of BHID to mice with STZ-induced DN prevented physiological and serological changes, structural damage, and kidney dysfunction. Based on a metabolomics test with serum, the profoundly altered metabolites in the BHID treatment group were identified. Thirty-six BHID-related proteins and four signaling pathways, including valine, leucine, and isoleucine biosynthesis, nicotinate and nicotinamide metabolism, tryptophan metabolism, and alanine, aspartate, and glutamate metabolism pathways, were explored. Principal coordinates analysis (PCoA) of the gut microbiota revealed that BHID treatment significantly affected the flora composition. In addition, the network pharmacology analysis revealed that BHID acted through phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt) and MAPK-related protein targets. Our findings on the anti-DN effects of BHID and its mechanism of action, from the perspective of systems biology, have provided scientific evidence to support the clinical treatment of patients with diabetes, and implied that BHID has the potential to prevent the progression of DN.

18β-Glycyrrhetinic acid acts through hepatocyte nuclear factor 4 alpha to modulate lipid and carbohydrate metabolism

Hepatocyte nuclear factor 4 alpha (HNF4α) regulates the expression of essential genes involved in very-low-density lipoprotein (VLDL) homeostasis and gluconeogenesis.　18β-glycyrrhetinic acid (GA) is an active ingredient of Glycyrrhiza uralensis an herbal medicine used for treating liver aliments. In this study, we established that GA functions as a partial antagonist of HNF4α through HNF4α-driven reporter luciferase assay and co-immunoprecipitation experiments with co-activator PGC1α. By virtual docking and site-directed mutagenesis analysis, we confirmed that serine 190 and arginine 235 of HNF4α are both essential for GA to exert its antagonistic action on HNF4α. Importantly, GA suppressed the expression of HNF4α target genes such as apolipoprotein B (ApoB), microsomal triglyceride transfer protein (MTP) and phospholipase A₂ G12B (PLA2G12B) modulating hepatic VLDL secretion in mice fed on a high fat diet. In addition, GA also suppressed gluconeogenesis and ameliorated glucose intolerance via down-regulating the expression of HNF4α target genes glucose-6-phosphatase (G6pc) and phosphoenolpyruvate carboxykinase (Pepck). Furthermore, GA significantly lowered blood glucose and improved insulin resistance in db/db mice. In all, we established that GA acts as a partial HNF4α antagonist modulating lipid and carbohydrate metabolism.

Abdel-Daim M, Prasad Devkota H. Traditional Uses, Bioactive Chemical Constituents, and Pharmacological and Toxicological Activities of Glycyrrhiza glabra L. (Fabaceae)

Traditional herbal remedies have been attracting attention as prospective alternative resources of therapy for diverse diseases across many nations. In recent decades, medicinal plants have been gaining wider acceptance due to the perception that these plants, as natural products, have fewer side effects and improved efficacy compared to their synthetic counterparts. Glycyrrhiza glabra L. (Licorice) is a small perennial herb that has been traditionally used to treat many diseases, such as respiratory disorders, hyperdipsia, epilepsy, fever, sexual debility, paralysis, stomach ulcers, rheumatism, skin diseases, hemorrhagic diseases, and jaundice. Moreover, chemical analysis of the G. glabra extracts revealed the presence of several organic acids, liquirtin, rhamnoliquirilin, liquiritigenin, prenyllicoflavone A, glucoliquiritin apioside, 1-metho-xyphaseolin, shinpterocarpin, shinflavanone, licopyranocoumarin, glisoflavone, licoarylcoumarin, glycyrrhizin, isoangustone A, semilicoisoflavone B, licoriphenone, and 1-methoxyficifolinol, kanzonol R and several volatile components. Pharmacological activities of G. glabra have been evaluated against various microorganisms and parasites, including pathogenic bacteria, viruses, and Plasmodium falciparum, and completely eradicated P. yoelii parasites. Additionally, it shows antioxidant, antifungal, anticarcinogenic, anti-inflammatory, and cytotoxic activities. The current review examined the phytochemical composition, pharmacological activities, pharmacokinetics, and toxic activities of G. glabra extracts as well as its phytoconstituents.

Inhibition of HMGB1 Promotes Osseointegration under Hyperglycemic Condition through Improvement of BMSC Dysfunction

High mobility group box 1 (HMGB1) participates actively in oxidative stress damage and the latter relates closely to diabetic complications, including poor implant osseointegration. This article is aimed at investigating the effects of HMGB1 on dysfunction of bone marrow stromal cells (BMSCs) and impaired osseointegration under diabetic environment. In vitro, BMSCs were treated with normal glucose (NG), high glucose (HG), and HG+glycyrrhizin (HMGB1 inhibitor, HG+GL). Cell proliferation, osteogenic behaviors, and oxidative stress were determined. In vivo, 8-week-old Sprague-Dawley rats were categorized to control, streptozotocin-induced diabetic, and diabetic-GL groups. Rats received GL (50 mg/kg, i.p.) or vehicle treatment daily after titanium implants were planted into the tibiae. After 4 and 8 weeks, plasma lipoperoxide detection, μCT analysis, and histomorphometric evaluation were conducted. By these approaches, we demonstrated that inhibiting HMGB1 by GL significantly attenuated HG-induced upregulation of HMGB1, HMGB1 ligand receptor for advanced glycation end products (RAGE) and their interaction, relieved oxidative stress, and reversed the downregulation of osteogenic markers, resulting in improved osteogenic differentiation. In diabetic rats, GL administration suppressed the upregulation of HMGB1, attenuated the lipoperoxide, and ameliorated the impaired trabecular structure and osseointegration. Taken together, inhibiting HMGB1 can be an effective approach to relieve BMSC dysfunction and enhance osseointegration under diabetic environment.

Evaluation of the Anti-Diabetic Activity of Some Common Herbs and Spices: Providing New Insights with Inverse Virtual Screening

Culinary herbs and spices are widely used as a traditional medicine in the treatment of diabetes and its complications, and there are several scientific studies in the literature supporting the use of these medicinal plants. However, there is often a lack of knowledge on the bioactive compounds of these herbs and spices and their mechanisms of action. The aim of this study was to use inverse virtual screening to provide insights into the bioactive compounds of common herbs and spices, and their potential molecular mechanisms of action in the treatment of diabetes. In this study, a library of over 2300 compounds derived from 30 common herbs and spices were screened in silico with the DIA-DB web server against 18 known diabetes drug targets. Over 900 compounds from the herbs and spices library were observed to have potential anti-diabetic activity and liquorice, hops, fennel, rosemary, and fenugreek were observed to be particularly enriched with potential anti-diabetic compounds. A large percentage of the compounds were observed to be potential polypharmacological agents regulating three or more anti-diabetic drug targets and included compounds such as achillin B from yarrow, asparasaponin I from fenugreek, bisdemethoxycurcumin from turmeric, carlinoside from lemongrass, cinnamtannin B1 from cinnamon, crocin from saffron and glabridin from liquorice. The major targets identified for the herbs and spices compounds were dipeptidyl peptidase-4 (DPP4), intestinal maltase-glucoamylase (MGAM), liver receptor homolog-1 (NR5A2), pancreatic alpha-amylase (AM2A), peroxisome proliferator-activated receptor alpha (PPARA), protein tyrosine phosphatase non-receptor type 9 (PTPN9), and retinol binding protein-4 (RBP4) with over 250 compounds observed to be potential inhibitors of these particular protein targets. Only bay leaves, liquorice and thyme were found to contain compounds that could potentially regulate all 18 protein targets followed by black pepper, cumin, dill, hops and marjoram with 17 protein targets. In most cases more than one compound within a given plant could potentially regulate a particular protein target. It was observed that through this multi-compound-multi target regulation of these specific protein targets that the major anti-diabetic effects of reduced hyperglycemia and hyperlipidemia of the herbs and spices could be explained. The results of this study, taken together with the known scientific literature, indicated that the anti-diabetic potential of common culinary herbs and spices was the result of the collective action of more than one bioactive compound regulating and restoring several dysregulated and interconnected diabetic biological processes.

Raffia palm (Raphia hookeri G. Mann & H. Wendl) wine modulates glucose homeostasis by enhancing insulin secretion and inhibiting redox imbalance in a rat model of diabetes induced by high fructose diet and streptozotocin

ETHNOPHARMACOLOGICAL RELEVANCE

Raffia palm (Raphia hookeri) wine (RPW) is amongst the natural products from plants, utilized singly or in combination with other medicinal plants for the treatment of several ailments including Diabetes Mellitus (DM). However, there is a scientific dearth on its antidiabetic activity.

AIM

The antidiabetic effect of RPW and its possible mechanism of actions were investigated in diabetic rats.

METHODS

Four groups of male SD rats were first supplied with 10% fructose solution ad libitum for 2 weeks instead of drinking water followed by an intraperitonial injection of streptozotocin (40 mg/kg) to induce diabetes. Two diabetic groups were administered RPW at 150 and 300 mg/kg bodyweight (BW) respectively; a group was administered with metformin, while the other one was served as a negative control. Two groups of normal rats were administered with water and RPW (300 mg/kg BW) and served as normal control and normal toxicology group, respectively.

RESULTS

Five weeks treatment of RPW led to significant (p < 0.05) increase in serum insulin and HDL-c levels with concomitant reduction in blood glucose, fructosamine, ALT, uric acid, triglycerides and LDL-c levels in diabetic rats. Rats treated with RPW had elevated levels of GSH, SOD, catalase, ATPase and α-amylase activities, while reduced NO level and myeloperoxidase activity was observed in their serum and pancreatic tissues. RPW also improved pancreatic β-cell function and restored β- and acinar cells morphology, and capillary networks. The activities of glycogen phosphorylase, fructose 1,6 biphosphatase, glucose-6-phosphatase, and acetylcholinesterase were also inhibited in RPW-treated diabetic rats, with concomitant down regulation of Nrf2 gene expression.

CONCLUSION

The data of this study suggest that RPW modulates glucose homeostasis by enhancing insulin secretion as well as inhibiting redox imbalance in diabetic rats, which may be attributed to the synergetic effects of its phytochemical constituents as identified by GC-MS analysis.

Protective effect of Glycyrrhiza glabra roots extract on bone mineral density of ovariectomized rats

Objective: The aim of this study was to evaluate the potential effect of the methanolic extract of plant Glycyrrhiza glabra roots on bone mineral density and femoral bone strength of ovariectomized rats.

Methods: Thirty 10-month-old Wistar rats were randomly separated into three groups of ten, Control, Ovariectomy and Ovariectomy-plus-Glycyrrhiza in their drinking water. Total and proximal tibial bone mineral density was measured in all groups before ovariectomy (baseline) and after 3 and 6 months post ovariectomy. Three-point-bending of the femurs and uterine weight and histology were examined at the end of the study.

Results: No significant difference was noted in bone density percentage change of total tibia from baseline to 3 months between Control and Ovariectomy-plus-Glycyrrhiza groups (+5.31% ± 4.75 and +3.30% ± 6.31 respectively, P = non significant), and of proximal tibia accordingly (+5.58% ± 6.92 and +2.61% ± 13.62, P = non significant) demonstrating a strong osteoprotective effect. There was notable difference in percentage change of total tibia from baseline to 6 months between groups Ovariectomy and Ovariectomy-plus-Glycyrrhiza (−13.03% ± 5.11 and −0.84% ± 7.63 respectively, P < 0.005), and of proximal tibia accordingly (−27.9% ± 3.69 and −0.81% ± 14.85 respectively, P < 0.001), confirming the protective effect of Glycyrrhiza glabra extract in preserving bone density of the Ovariectomy-plus-Glycyrrhiza group. Three-point-bending did not reveal any statistically significant difference between Ovariectomy and Ovariectomy-plus-Glycyrrhiza groups. Uterine weights of the Ovariectomy-plus-Glycyrrhiza group ranged between the other two groups with no statistically significant difference to each.

Conclusions: Glycyrrhiza glabra root extract notably protected tibial bone mineral density loss in Ovariectomy-plus-Glycyrrhiza rats in comparison with ovariectomized rats, but did not improve biomechanical strength.

Effect of Olea europaea leaves extract on streptozotocin induced diabetes in male albino rats

The present study was aimed to evaluate the effect of olive (Olea europaea) leaves extract on streptozotocin (STZ)-induced diabetic male rats. The experimental rats were divided into six groups. Rats of the first group were served as normal controls. Rats of the second group were diabetic control. The third and fourth groups were diabetic rats, treated with olive leaves extract at low and high doses respectively. The fifth and sixth groups were non diabetic rats, subjected to olive leaves extract at the same doses given to the third and fourth groups respectively. The minimum of body weigh gain was noted in diabetic rats of the second group. the levels of serum glucose, insulin, total protein, albumin, triglycerides, cholesterol, low density lipoprotein cholesterol (LDL-C), very low density lipoprotein cholesterol (VLDL-C), creatine kinase (CK), lactate dehydrogenase (LDH) and malondialdehyde (MDA) were significantly increased, while the levels of high density lipoprotein cholesterol (HDL-C), superoxide dismutase, (SOD) glutathione (GSH) and catalase (CAT) were statistically decreased in diabetic rats of the second group. The levels of liver insulin receptor substrate 1 (IRS1) and insulin receptor A (IRA) were significantly declined in diabetic rats of the second group. The diabetic pancreatic sections from diabetic rats of the second group showed several histopathological changes. Administration of low and high doses of olive leaves extract improved the observed physiological, molecular and histopathological alterations. Collectively, the obtained results confirmed that the protective effects of olive leaves extract are attributed to the antioxidant activities of olive leaves extract and its active constituents.

Protective effect of triterpenes against diabetes-induced β-cell damage: An overview of in vitro and in vivo studies

Accumulative evidence shows that chronic hyperglycaemia is a major factor implicated in the development of pancreatic β-cell dysfunction in diabetic patients. Furthermore, most of these patients display impaired insulin signalling that is responsible for accelerated pancreatic β-cell damage. Indeed, prominent pathways involved in glucose metabolism such as phosphatidylinositol 3-kinase/ protein kinase B (PI3-K/AKT) and 5' AMP-activated protein kinase (AMPK) are impaired in an insulin resistant state. The impairment of this pathway is associated with over production of reactive oxygen species and pro-inflammatory factors that supersede pancreatic β-cell damage. Although several antidiabetic drugs can improve β-cell function by modulating key regulators such as PI3-K/AKT and AMPK, evidence of their β-cell regenerative and protective effect is scanty. As a result, there has been continued exploration of novel antidiabetic therapeutics with abundant antioxidant and antiinflammatory properties that are essential in protecting against β-cell damage. Such therapies include triterpenes, which have displayed robust effects to improve glycaemic tolerance, insulin secretion, and pancreatic β-cell function. This review summarises most relevant effects of various triterpenes on improving pancreatic β-cell function in both in vitro and in vivo experimental models. A special focus falls on studies reporting on the ameliorative properties of these compounds against insulin resistance, oxidative stress and inflammation, the well-known factors involved in hyperglycaemia associated tissue damage.

Renoprotective Effect of a Chinese Herbal Formula, Qidan Dihuang Decoction, on Streptozotocin-Induced Diabetes in Rat

Qidan Dihuang decoction (QDD) is the latest development of Chinese medicine compound and mainly provides renal protection. The study presented was designed to evaluate the renoprotective effects of QDD on streptozotocin-induced diabetes and to explore the possible mechanisms of this action. We established a diabetes rat model. The condition of the rats was observed. The biochemistry indexes for diabetic rats were examined. Renal tissues were stained with HE, PAS, and Masson and we performed immunohistochemical staining for α-SMA and TGF-β. The proteins expressions of α-SMA, TGF-β, renin, and AT1 were detected by western blot. After treatment for 8 weeks, serum creatinine and 24 h proteinuria were significantly reduced in the rats which received losartan and Qidan Dihuang decoction while blood glucose, urine volume, blood urea nitrogen, and KW/BW did not improve. The pathology of renal tissue of rats treated with losartan and Qidan Dihuang decoction was inhibited. In addition, western blot showed that the expression of α-SMA, TGF-β, renin, and AT1 proteins was significantly decreased after receiving Qidan Dihuang decoction and losartan. Taken together, the results indicate that Qidan Dihuang decoction can improve the renal function and inhibit renal fibrosis of DN rat via modulating RAS system.

Comparative study of selective in vitro and in silico BACE1 inhibitory potential of glycyrrhizin together with its metabolites, 18α- and 18β-glycyrrhetinic acid, isolated from Hizikia fusiformis

Hizikia fusiformis (Harvey) Okamura is a brown seaweed widely used in Korea and Japan, and it contains different therapeutically active constituents. In the present study, we investigated the activities of glycyrrhizin isolated from H. fusiformis, including its metabolites, 18α- and 18β-glycyrrhetinic acid against Alzheimer's disease (AD) via acetyl and butyrylcholinesterase and β-site amyloid precursor protein cleaving enzyme 1 (BACE1) inhibition. Among these three compounds, 18β-glycyrrhetinic acid (IC₅₀ = 8.93 ± 0.69 µM) demonstrated two fold potent activity against BACE1 compared to the positive control, quercetin (IC₅₀ = 20.18 ± 0.79 µM). Additionally, glycyrrhizin with an IC₅₀ value of 20.12 ± 1.87 µM showed similarity to quercetin, while 18α-glycyrrhetinic acid showed moderate activity (IC₅₀ = 104.35 ± 2.84 µM). A kinetic study revealed that glycyrrhizin and 18β-glycyrrhetinic acid were non-competitive and competitive inhibitiors of BACE1, demonstrated via K _i values of 16.92 and 10.91 µM, respectively. Molecular docking simulation studies evidently revealed strong binding energy of these compounds for BACE1, indicating their high affinity and capacity for tighter binding to the active site of the enzyme. These data suggest that glycyrrhizin isolated from the edible seaweed, H. fusiformis and its metabolite, 18β-glycyrrhetinic acid demonstrated selective inhibitory activity against BACE1 to alleviate AD.

Attenuation of glycation-induced multiple protein modifications by Indian antidiabetic plant extracts

CONTEXT

Protein glycation is the major contributing factor in the development of diabetic complications. The antiglycation potential of medicinal plants provides a promising opportunity as complementary interventions for complications.

OBJECTIVE

To investigate the antiglycation potential of 19 medicinal plants extracts using albumin by estimating different indicators: (1) glycation (early and late), (2) albumin oxidation, and (3) amyloid aggregation.

MATERIALS AND METHODS

The effect of aqueous plant extracts (1% w/v) on protein glycation was assessed by incubating albumin (10 mg/mL) with fructose (250 mM) for 4 days. Degree of protein glycation in the absence and presence of plant extracts was assessed by estimating fructosamine, advanced glycation end products (AGEs), carbonyls, free thiol group and β-amyloid aggregation.

RESULTS

Petroselinum crispum, Boerhavia diffusa, Terminalia chebula, Swertia chirayita and Glycyrrhiza glabra showed significant antiglycating activity. P. crispum and A. barbadensis inhibited the carbonyl stress and protected the thiol group from oxidative damage. There was significant correlation between protein thiols and amyloid inhibition (R = -.69, p < .001).

CONCLUSION

P. crispum, B. diffusa and T. chebula had the most potent antiglycation activity. These plant exerted noticeable antiglycation activity at different glycation modifications of albumin. These findings are important for identifying plants with potential to combat diabetic complications.

A Mechanistic Review on Medicinal Plants Used for Diabetes Mellitus in Traditional Persian Medicine

Diabetes mellitus is the most common endocrine disorder and a major cause of morbidity and mortality. Traditional medicines worldwide suggest a wide range of natural remedies for the prevention and treatment of chronic disorders, including diabetes mellitus. This mechanistic review aims to highlight the significance of medicinal plants traditionally used as dietary supplements in Persian medicine in adjunct with restricted conventional drugs for the prevention and treatment of diabetes mellitus. Mounting evidence suggests that these natural agents perform their protective and therapeutic effect on diabetes mellitus via several cellular mechanisms, including regeneration of pancreatic β cell, limitation of glycogen degradation and gluconeogenesis, anti-inflammatory, immunoregulatory, antiapoptosis, antioxidative stress, as well as modulation of intracellular signaling transduction pathways. In conclusion, traditional medicinal plants used in Persian medicine can be considered as dietary supplements with therapeutic potential for diabetes mellitus and maybe potential sources of new orally active agent(s).

Glycyrrhizic acid increases glucagon like peptide-1 secretion via TGR5 activation in type 1-like diabetic rats

Glycyrrhizic acid (GA) is belonged to triterpenoid saponin that is contained in the root of licorice and is known to affect metabolic regulation. Recently, glucagon like peptide-1 (GLP-1) has widely been applied in diabetes therapeutics. However, the role of GLP-1 in GA-induced anti-diabetic effects is still unknown. Therefore, we are interested in understanding the association of GLP-1 with GA-induced effects. In type 1-like diabetic rats induced by streptozotocin (STZ-treated rats), GA increased the level of plasma GLP-1, which was blocked by triamterene at a dose sufficient to inhibit Takeda G-protein-coupled receptor 5 (TGR5). The direct effect of GA on TGR5 has been identified using the cultured Chinese hamster ovary cells (CHO-K1 cells) transfected TGR5 gene. Moreover, in intestinal NCI-H716 cells that secreted GLP-1, GA promoted GLP-1 secretion with a marked elevation of calcium levels. However, both effects of GA were reduced by ablation of TGR5 with siRNA in NCI-H716 cells. Therefore, we demonstrated that GA can enhance GLP-1 secretion through TGR5 activation.

Glyoxal-induced modification enhances stability of hemoglobin and lowers iron-mediated oxidation reactions of the heme protein: An in vitro study

Glyoxal, a reactive α-oxoaldehyde, increases in diabetic condition. It reacts with different proteins to form advanced glycation end products (AGEs) following Maillard-like reaction. Considering the significance of AGE-mediated protein modification by glyoxal, here we have investigated the in vitro effect of the reactive α-oxoaldehyde (10, 20μM) on the heme protein hemoglobin (HbA₀) (100μM) after incubation for one week at 25°C. In comparison with HbA₀, glyoxal-treated HbA₀ exhibited decreased absorbance around 280nm, reduced intrinsic fluorescence and lower surface hydrophobicity. Glyoxal treatment was found to increase the stability of HbA₀ without significant perturbation of the secondary structure of the heme protein. In addition, H₂O₂-mediated iron release and subsequent iron-mediated oxidative (Fenton) reactions were found to be lower in presence of glyoxal-treated HbA₀ compared to HbA₀. Mass spectrometric studies revealed modification of arginine residues of HbA₀ (Arg-31α, Arg-40β) to hydroimidazolone adducts. AGE-induced modifications thus appear to be associated with the observed changes of the heme protein. Considering the increased level of glyoxal in diabetes mellitus as well as its high reactivity, glyoxal-derived AGE adducts might thus be associated with modifications of the protein including physiological significance.