Phytochemicals as modulators of β-cells and immunity for the therapy of type 1 diabetes: Recent discoveries in pharmacological mechanisms and clinical potential

Formononetin, a bioactive isoflavonoid constituent from Astragalus membranaceus (Fisch.) Bunge, ameliorates type 1 diabetes mellitus via activation of Keap1/Nrf2 signaling pathway: An integrated study supported by network pharmacology and experimental validation

ETHNOPHARMACOLOGICAL RELEVANCE

Type 1 diabetes mellitus (T1DM) results from insulin deficiency due to the destruction of pancreatic β-cells. Previously, our studies showed that inhibition of Keap1/Nrf2 signaling pathway promoted the onset of T1DM, which suggests that finding drugs that can activate the Keap1/Nrf2 signaling may be a promising therapeutic strategy for the T1DM treatment. Astragalus membranaceus (Fisch.) Bunge is a common traditional Chinese medicine that has been frequently applied in Chinese clinics for the treatment of diabetes and other diseases. Formononetin (FMNT), one of the major isoflavonoid constituents isolated from this herbal medicine, possesses diverse pharmacological benefits and T1DM therapeutic potential. However, the exact molecular mechanisms underlying the action of FMNT in ameliorating T1DM have yet to be fully elucidated.

AIMS OF THE STUDY

This study is to investigate the regulation of FMNT on the Keap1/Nrf2 signaling pathway to ameliorate T1DM based on network pharmacology approach combined with experimental validation.

MATERIALS AND METHODS

A mouse-derived pancreatic islet β-cell line (MIN6) was used for the in vitro studies. An alloxan (ALX)-induced T1DM model in wild-type and Nrf2 knockout (Nrf2-/-) C57BL/6J mice were established for the in vivo experiments. The protective effects of FMNT against ALX-stimulated MIN6 cell injury were evaluated using MTT, EdU, apoptosis and comet assays. The levels of blood glucose in mice were measured by using a blood monitor and test strips. The protein expression was detected by Western blot analysis. Furthermore, the binding affinity of FMNT to Keap1 was evaluated using cellular thermal shift assay (CETSA), drug affinity responsive target stability (DARTS) assay, and solvent-induced protein precipitation (SIP) assay. The interaction pattern between FMNT and Keap1 was assessed by molecular docking and molecular dynamics simulation techniques.

RESULTS

Network pharmacology analysis revealed that FMNT exerted its therapeutic effect against T1DM by mainly regulating oxidative stress response-associated signaling molecules and pathways, such as Nrf2 regulating anti-oxidant/detoxification enzymes and Keap1-Nrf2 signaling pathway. The in vivo results showed that FMNT significantly deceased the ALX-induced high blood glucose levels and conversely increased the ALX-induced low insulin contents. In vitro, FMNT markedly protected MIN6 cells from ALX-induced cytotoxicity, proliferation inhibition and DNA damage and reduced the ALX-stimulated cell apoptosis. FMNT also inhibited ALX-induced overproduction of intracellular ROS to alleviate oxidative stress. In addition, FMNT could bind to Keap1 to notably activate the Keap1/Nrf2 signaling to upregulate Nrf2 expression and promote the Nrf2 translocation from the cytoplasm to the nucleus, resulting in enhancing the expression of antioxidant proteins HO-1 and NQO1. Inhibition of Keap1/Nrf2 signaling by ALX was also markedly abolished in the cells and mice exposed to FMNT. Moreover, these effects of FMNT in ameliorating T1DM were not observed in Nrf2-/- mice.

CONCLUSIONS

This study demonstrates that FMNT could bind to Keap1 to activate the Keap1/Nrf2 signaling to prevent intracellular ROS overproduction, thereby attenuating ALX-induced MIN6 cell injury and ameliorating ALX-stimulated T1DM. Results from this study might provide evidence and new insight into the therapeutic effect of FMNT and indicate that FMNT is a promising candidate agent for the treatment of T1DM in clinics.

Assessment of antidiabetic, anti-inflammatory, antioxidant and anticancer activity competence of methonolic extracts of Trianthema ortulacastrum and Andrographis paniculata

An in-vitro investigation was performed to evaluate and compare the phytochemical, antioxidant, antidiabetic, anti-inflammatory, and anti-lung cancer activities of methanol extracts of aerial parts of Andrographis paniculata and Trianthema portulacastrum. Furthermore studied major functional groups of phytochemicals present in the methanol extracts of these plants through Fourier transform infrared (FTIR) analysis. The results showed that the methanol extract of A. paniculata contain more number of pharmaceutically valuable phytochemicals such as alkaloids, flavonoids, terpenoids, saponin, glycoside, phytosterol, and tannin than T. portulacastrum. Similar way the methanol extract of A. paniculata showed considerable dose dependent antioxidant (DPPH: 63%), antidiabetic (α-amylase: 82.31% and α-glucosidase inhibitions: 72.34%), and anti-inflammatory (albumin-denaturation inhibition: 76.3% and anti-lipoxygenase: 61.2%) activities (at 900 μg mL-1 concentration) than T. portulacastrum. However, the anti-lung cancer activities of these test plants against A549 cells were not considerable. According to FTIR analysis, the A. paniculata methanol extract has a larger number of characteristic peaks attributed to the active functional groups of pharmaceutically valuable bioactive components that belong to different types of phytochemicals. These findings imply that A. paniculata methanol extracts can be used for additional research, such as bioactive compound screening and purification, as well as assessing their potential biomedical uses in various in-vitro and in-research settings.

Regeneration of Pancreatic Beta Cells by Modulation of Molecular Targets Using Plant-Derived Compounds: Pharmacological Mechanisms and Clinical Potential

Type 2 diabetes (T2D) is characterized by pancreatic beta-cell dysfunction, increased cell death and loss of beta-cell mass despite chronic treatment. Consequently, there has been growing interest in developing beta cell-centered therapies. Beta-cell regeneration is mediated by augmented beta-cell proliferation, transdifferentiation of other islet cell types to functional beta-like cells or the reprograming of beta-cell progenitors into fully differentiated beta cells. This mediation is orchestrated by beta-cell differentiation transcription factors and the regulation of the cell cycle machinery. This review investigates the beta-cell regenerative potential of antidiabetic plant extracts and phytochemicals. Various preclinical studies, including in vitro, in vivo and ex vivo studies, are highlighted. Further, the potential regenerative mechanisms and the intra and extracellular mediators that are of significance are discussed. Also, the potential of phytochemicals to translate into regenerative therapies for T2D patients is highlighted, and some suggestions regarding future perspectives are made.

Nutraceuticals as Modulators of Immune Function: A Review of Potential Therapeutic Effects

Dietary supplementation with nutraceuticals can promote optimal immune system activation, modulating different pathways that enhance immune defenses. Therefore, the immunity-boosting effects of nutraceuticals encompass not only immunomodulatory but also antioxidant, antitumor, antiviral, antibacterial, and antifungal properties, with therapeutic effects against diverse pathological conditions. However, the complexity of the pathways that regulate the immune system, numerous mechanisms of action, and heterogeneity of the immunodeficiencies, and subjects treated make their application in the clinical field difficult. Some nutraceuticals appear to safely improve immune system function, particularly by preventing viral and bacterial infections in specific groups, such as children, the elderly, and athletes, as well as in frail patients, such as those affected by autoimmune diseases, chronic diseases, or cancer. Several nutraceuticals, such as vitamins, mineral salts, polyunsaturated omega-3 fatty acids, many types of phytocompounds, and probiotic strains, have the most consolidated evidence in humans. In most cases, further large and long-term randomized clinical trials are needed to confirm the available preliminary positive data.

Phytochemistry, Pharmacology and Mode of Action of the Anti-Bacterial Artemisia Plants

Over 70,000 people die of bacterial infections worldwide annually. Antibiotics have been liberally used to treat these diseases and, consequently, antibiotic resistance and drug ineffectiveness has been generated. In this environment, new anti-bacterial compounds are being urgently sought. Around 500 Artemisia species have been identified worldwide. Most species of this genus are aromatic and have multiple functions. Research into the Artemisia plants has expanded rapidly in recent years. Herein, we aim to update and summarize recent information about the phytochemistry, pharmacology and toxicology of the Artemisia plants. A literature search of articles published between 2003 to 2022 in PubMed, Google Scholar, Web of Science databases, and KNApSAcK metabolomics databases revealed that 20 Artemisia species and 75 compounds have been documented to possess anti-bacterial functions and multiple modes of action. We focus and discuss the progress in understanding the chemistry (structure and plant species source), anti-bacterial activities, and possible mechanisms of these phytochemicals. Mechanistic studies show that terpenoids, flavonoids, coumarins and others (miscellaneous group) were able to destroy cell walls and membranes in bacteria and interfere with DNA, proteins, enzymes and so on in bacteria. An overview of new anti-bacterial strategies using plant compounds and extracts is also provided.

Investigating the chemical profile of Rheum lhasaense and its main ingredient of piceatannol-3'-O-β-D-glucopyranoside on ameliorating cognitive impairment

Rheum lhasaense A. J. Li et P. K. Hsiao, a stout herb plant from the Polygonaceae, is a typical Tibetan folk herb with heat-clearing and detoxifying effects, but does not have the typical laxative effect compared with other rhubarb plants. Nevertheless, its chemical composition and pharmacological activities still lack in-depth research. The present study endeavored to analyze the possible phytochemical constituents in R. lhasaense and explore the main compound piceatannol-3'-O-β-D-glucopyranoside (PG) effect on cognitive impairment and its underlying mechanism. The chemical profile of R. lhasaense discovered 46 compounds, including 27 stilbenoids and 13 gallotannins using UPLC-Q-TOF-MS/MS. The UPLC determined the contents of 6 main stilbenoids, among which the content of PG was the highest, up to 61.06 mg/g. Moreover, behavioral tests showed that PG (40 mg/kg and 160 mg/kg) administration markedly ameliorated memory impairments of scopolamine-induced mice. Biochemical parameters showed that PG treatment alleviated the levels of Ach, AchE, and inflammatory factors while elevating the levels of antioxidants in mice. In addition, network pharmacology was performed to reveal PG exert an mild cognitive impairment effect by participating in neurodegenerative disease pathways, proliferation and apoptosis-, and inflammation-related pathways. Eventually, the results of molecular docking and the qRT-PCR revealed that PG down-regulated the mRNA expressions of MMP3, MMP9 and BACE1 in cognitive impairment mice brain tissue. In conclusion, our results demonstrated that PG mitigated scopolamine-induced cognitive dysfunction in mice by targeting the BACE1-MMP3/9 pathway, and PG might be a promising mild AD drug candidate.

"Multiomics" Analyses Combined with Systems Pharmacology Reveal the Renoprotection of Mangiferin Monosodium Salt in Rats with Diabetic Nephropathy: Focus on Improvements in Renal Ferroptosis, Renal Inflammation, and Podocyte Insulin Resistance

We explored the protection of mangiferin monosodium salt (MGM) on kidney injury in rats with streptozotocin (STZ)-induced diabetic nephropathy (DN) by "multiomics" analysis combined with systems pharmacology, with a specific focus on ferroptosis, inflammation, and podocyte insulin resistance (IR) signaling events in kidneys. MGM treatment afforded renoprotective effects on rats with STZ-induced DN by alleviating systemic IR-induced renal inflammation and podocyte IR. These mechanisms were correlated mainly with the MGM treatment-induced inhibition of the mitogen-activated protein kinase/nuclear factor-kappa B axis and activation of the phosphorylated insulin receptor substrate 1(Tyr608)/phosphorylated phosphatidylinositol 3-kinase/phosphorylated protein kinase B axis in the kidneys of DN rats. MGM had an ameliorative function in renal ferroptosis in rats with STZ-induced DN by upregulating mevalonate-mediated antioxidant capacities (glutathione peroxidase 4 and ferroptosis suppressor protein 1/coenzyme Q10 axis) and weakening acyl-CoA synthetase long-chain family member 4-mediated proferroptotic generation of lipid drivers in kidneys. MGM may be a promising alternative strategy for the treatment of DN.

Proteomic examination of Cornus officinalis stimulated 1.1B4 human pancreatic cells reveals activation of autophagy and Keap1/Nrf2 pathway

Type 1 diabetes (T1D) is an autoimmune disease initiated by genetic predisposition and environmental influences culminating in the immunologically mediated destruction of pancreatic β-cells with eventual loss of insulin production. Although T1D can be accurately predicted via autoantibodies, therapies are lacking that can intercede autoimmunity and protect pancreatic β-cells. There are no approved interventional modalities established for this purpose. One such potential source for clinical agents of this use is from the frequently utilized Cornus officinalis (CO) in the field of ethnopharmacology. Studies by our lab and others have demonstrated that CO has robust proliferative, metabolic, and cytokine protective effects on pancreatic β-cells. To identify the molecular mechanism of the biological effects of CO, we performed a proteomic and phosphoproteomic analysis examining the cellular networks impacted by CO application on the 1.1B4 pancreatic β-cell line. Our label-free mass spectrometry approach has demonstrated significant increased phosphorylation of the selective autophagy receptor of p62 (Sequestosome-1/SQSTM1/p62) and predicted activation of the antioxidant Kelch-like ECH-associated protein 1 (Keap1)/Nuclear factor-erythroid factor 2-related factor 2 (Nrf2) pathway. Further validation by immunoblotting and immunofluorescence revealed markers of autophagy such as increased LC3-II and decreased total p62 along with nuclear localization of Nrf2. Both autophagy and the Keap1/Nrf2 pathways have been shown to be impaired in human and animal models of T1D and may serve as an excellent potential therapeutic target stimulated by CO.

Antidiabetic activity of Solanum torvum fruit extract in streptozotocin-induced diabetic rats

Background

Solanum torvum Swartz, a medicinal plant belonging to the family Solanaceae, is an important medicinal plant widely distributed throughout the world and used as medicine to treat diabetes, hypertension, tooth decay, and reproductive problems in traditional systems of medicine around the world including Malaysia. The objective of this study was to investigate hypoglycemic, antilipidemic, and hepatoprotective activities, histopathology of the pancreas, and specific glucose regulating gene expression of the ethanolic extract of S. torvum fruit in streptozotocin-induced diabetic Sprague–Dawley rats.

Materials and methods

Acute toxicity study was done according to OECD-423 guidelines. Diabetes was induced by intraperitoneal (i.p.) injection of streptozotocin (55 mg/kg) in male Sprague–Dawley rats. Experimental diabetic rats were divided into six different groups; normal, diabetic control, and glibenclamide at 6 mg/kg body weight, and the other three groups of animals were treated with oral administration of ethanolic extract of S. torvum fruit at 120, 160, and 200 mg/kg for 28 days. The effect of ethanolic extract of S. torvum fruit on body weight, blood glucose, lipid profile, liver enzymes, histopathology of pancreas, and gene expression of glucose transporter 2 (slc2a2), and phosphoenolpyruvate carboxykinase (PCK1) was determined by RT-PCR.

Results

Acute toxicity studies showed LD₅₀ of ethanolic extract of S. torvum fruit to be at the dose of 1600 mg/kg body weight. Blood glucose, total cholesterol, triglycerides, low-density lipoproteins, very low-density lipoproteins, serum alanine aminotransferase, and aspartate aminotransferase were significantly reduced, whereas high-density lipoproteins were significantly increased in S. torvum fruit (200 mg/kg)-treated rats. Histopathological study of the pancreas showed an increase in number, size, and regeneration of β-cell of islets of Langerhans. Gene expression studies revealed the lower expression of slc2a2 and PCK1 in treated animals when compared to diabetic control.

Conclusion

Ethanolic extract of S. torvum fruits showed hypoglycemic, hypolipidemic, and hepatoprotective activity in streptozocin-induced diabetic rats. Histopathological studies revealed regeneration of β cells of islets of Langerhans. Gene expression studies indicated lower expression of slc2a2 and PCK1 in treated animals when compared to diabetic control, indicating that the treated animals prefer the gluconeogenesis pathway.

The management of diabetes mellitus by mangiferin: advances and prospects

Diabetes mellitus has become one of the most challenging public health problems today. There are still various deficiencies that remain in existing therapeutic drugs. With increasing prevalence and mortality rates, more effective therapeutic agents are required for treatment clinically. As a kind of polyphenol and as a natural product, mangiferin has numerous pharmacological and excellent effects. In this review, the underlying mechanisms of mangiferin on diabetes mellitus and complications will be summarized. Moreover, mangiferin belongs to the BSC IV class and the clinical application and development of mangiferin are limited due to its poor aqueous solubility and fat solubility as well as low bioavailability. Our review also elaborated on improving the solubility of mangiferin by changing the dosage form and introduced the existing results, which hope to provide useful reference for mangiferin for further treating diabetes. In conclusion, mangiferin might be a potential adjuvant therapy for the treatment of diabetes mellitus and complications in the future.

Trans-differentiation of mouse mesenchymal stem cells into pancreatic β-like cells by a traditional anti-diabetic medicinal herb Medicago sativa L

Background and aim

Medicago sativa L. is a medicinal herb first cultivated in ancient Iran. Traditionally, it has been utilized for the treatment of several disorders. The plant has been in the human diet for at least 1500 years. Although the hypoglycaemic and anti-diabetic effects of the plant have been approved in traditional medicine, further investigations are needed to support the rational use of M. sativa by humans. This project aimed to evaluate the trans-differentiation potential of bone marrow mesenchymal stem cells (MSCs) to pancreatic β-like cells (insulin-producing cells; IPCs) under the influence of M. sativa extract.

Experimental procedure

Bone marrow MSCs isolated, characterized, and then treated by flower or leaf extract of M. sativa. Beta-cell characteristics of the differentiated cells were evaluated by several techniques, including specific staining, QPCR, immunofluorescence, and ELISA.

Results

The results showed that the differentiated cells were able to express some specific pancreatic genes (PDX-1, insulin1, and insulin2) and proteins (insulin receptor beta, insulin, proinsulin, and C peptide). Furthermore, ELISA analysis indicated the ability of these cells in the production and secretion of insulin, after exposure to glucose.

Conclusion

Overall, both the flower and leaf extract of M. sativa had the potential of differentiation induction of MSCs into IPCs with the characteristics of pancreatic β–like cells. Therefore, M. sativa, as an herbal drug, may be beneficial for the treatment of diseases including diabetes.

Future Directions for the Discovery of Natural Product-Derived Immunomodulating Drugs

Drug discovery from natural sources is going through a renaissance, having spent many decades in the shadow of synthetic molecule drug discovery, despite the fact that natural product-derived compounds occupy a much greater chemical space than those created through synthetic chemistry methods. With this new era comes new possibilities, not least the novel targets that have emerged in recent times and the development of state-of-the-art technologies that can be applied to drug discovery from natural sources. Although progress has been made with some immunomodulating drugs, there remains a pressing need for new agents that can be used to treat the wide variety of conditions that arise from disruption, or over-activation, of the immune system; natural products may therefore be key in filling this gap. Recognising that, at present, there is no authoritative article that details the current state-of-the-art of the immunomodulatory activity of natural products, this in-depth review has arisen from a joint effort between the International Union of Basic and Clinical Pharmacology (IUPHAR) Natural Products and Immunopharmacology, with contributions from a Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation number of world-leading researchers in the field of natural product drug discovery, to provide a "position statement" on what natural products has to offer in the search for new immunomodulatory argents. To this end, we provide a historical look at previous discoveries of naturally occurring immunomodulators, present a picture of the current status of the field and provide insight into the future opportunities and challenges for the discovery of new drugs to treat immune-related diseases.

Phenethyl ester of rosmarinic acid attenuates autoimmune responses during type 1 diabetes development in mice

AIMS

Rosmarinic acid (RA) is a polyphenol that occurs in plants of the Lamiaceae family. Phenethyl ester of RA (PERA), a novel RA derivative, has been developed and evaluated in vivo in an animal model of type 1 diabetes (T1D).

METHODS

T1D was induced in male C57BL/6 mice using multiple low doses of streptozotocin (STZ) administered intraperitoneally for 5 consecutive days. Intraperitoneal administration of PERA (2.5 mg/kg bw) began from the first STZ injection and continued for 20 days.

KEY FINDINGS

PERA-treated mice exhibited lower incidence of T1D (monitored up to 38 days from the disease induction), and fluorescent histochemical analysis showed that their pancreatic islets expressed more insulin. PERA treatment significantly down-regulated the proportions of CD11b+ and CD11c+ myeloid cells in the immune cell infiltrates in the pancreatic islets early during T1D pathogenesis (on day 9 after T1D induction), while on day 15, PERA significantly reduced the proportions of CD11c+, CD8+, Th1 and Th17 cells. Simultaneously, it was found that the cells from the pancreatic infiltrates of PERA-treated mice produced significantly less reactive oxygen species than cells from the control group.

SIGNIFICANCE

These findings suggest that PERA efficiently prevented T1D development in mice. Interestingly, PERA attenuated the inflammatory process in the islets through temporally specific interference with the innate and adaptive immune response and therefore shows great promise for further clinical evaluation as a novel T1D therapeutic.

New Developments in T Cell Immunometabolism and Therapeutic Implications for Type 1 Diabetes

Type 1 diabetes (T1D) is an autoimmune disease mediated by T cells and is becoming a serious public health threat. Despite the increasing incidence rate of T1D worldwide, our understanding of why T1D develops and how T cells lose their self-tolerance in this process remain limited. Recent advances in immunometabolism have shown that cellular metabolism plays a fundamental role in shaping T cell responses. T cell activation and proliferation are supported by metabolic reprogramming to meet the increased energy and biomass demand, and deregulation in immune metabolism can lead to autoimmune disorders. Specific metabolic pathways and factors have been investigated to rectify known deficiencies in several autoimmune diseases, including T1D. Most therapeutic strategies have concentrated on aerobic glycolysis to limit T cell responses, whereas glycolysis is the main metabolic pathway for T cell activation and proliferation. The use of metabolic inhibitors, especially glycolysis inhibitors may largely leave T cell function intact but primarily target those autoreactive T cells with hyperactivated metabolism. In this review, we provide an overview of metabolic reprogramming used by T cells, summarize the recent findings of key metabolic pathways and regulators modulating T cell homeostasis, differentiation, and function in the context of T1D, and discuss the opportunities for metabolic intervention to be employed to suppress autoreactive T cells and limit the progression of β-cell destruction.

Potential antidiabetic phytochemicals in plant roots: a review of in vivo studies

Background

Medicinal plants are used to treat various disorders, including diabetes, globally in a range of formulations. While attention has mainly been on the aerial plant parts, there are only a few review studies to date that are focused on the natural constituents present in the plant roots with health benefits. Thus, the present study was performed to review in vivo studies investigating the antidiabetic potential of the natural compounds in plant roots.

Methods

We sorted relevant data in 2001-2019 from scientific databases and search engines, including Web of Knowledge, PubMed, ScienceDirect, Medline, Reaxys, and Google Scholar. The class of phytochemicals, plant families, major compounds, active constituents, effective dosages, type of extracts, time of experiments, and type of diabetic induction were described.

Results

In our literature review, we found 104 plants with determined antidiabetic activity in their root extracts. The biosynthesis pathways and mechanism of actions of the most frequent class of compounds were also proposed. The results of this review indicated that flavonoids, phenolic compounds, alkaloids, and phytosteroids are the most abundant natural compounds in plant roots with antidiabetic activity. Phytochemicals in plant roots possess different mechanisms of action to control diabetes, including inhibition of α-amylase and α-glucosidase enzymes, oxidative stress reduction, secretion of insulin, improvement of diabetic retinopathy/nephropathy, slow the starch digestion, and contribution against hyperglycemia.

Conclusion

This review concludes that plant roots are a promising source of bioactive compounds which can be explored to develop against diabetes and diabetes-related complications.

Graphical abstract

LncRNA GAS5 activates the HIF1A/VEGF pathway by binding to TAF15 to promote wound healing in diabetic foot ulcers

A diabetic foot ulcer (DFU) is one of the most devastating complications of diabetes. It has been reported that lncRNA GAS5 plays a vital role in wound healing in DFUs. However, the specific mechanism remains unclear. In this research, we aimed to investigate the role of GAS5 in wound healing in DFUs as well as the underlying mechanism. qPCR or western blotting was performed to measure the expression levels of GAS5, HIF1A, VEGF and TAF15. CCK-8 or EdU assays, flow cytometry, wound healing assays and tube formation assays were carried out to assess the proliferation, apoptosis, wound healing and in vitro angiogenesis of HUVECs, respectively. RNA pull-down and RIP assays were performed to verify the interaction between GAS5 and TAF15. ChIP and luciferase assays were conducted to verify the binding of TAF15 to the HIF1A promoter. In the DFU mouse model, H&E and Masson staining were used to determine epidermal and dermal thickness and collagen formation. GAS5 and HIF1A were downregulated in the skin tissues of DFU patients, and GAS5 overexpression promoted cell proliferation, wound healing and tubule formation in HG-treated HUVECs. In addition, GAS5 facilitated HIF1A expression by interacting with TAF15. Rescue assays demonstrated that the suppression of HIF1A/VEGF pathway activation partially reversed the functional roles of GAS5 in HUVECs. Furthermore, GAS5 accelerated wound healing by activating the HIF1A/VEGF pathway in mice with DFUs. GAS5 activates the HIF1A/VEGF pathway by binding to TAF15, resulting in accelerated wound healing in DFUs. Our findings may provide a theoretical basis for the clinical treatment of DFUs.

Potential therapeutic applications of phytoconstituents as immunomodulators: Pre-clinical and clinical evidences

Autoimmune and infectious diseases are the major public health issues and have gained great attention in the last few years for the search of new agents with therapeutic benefits on the host immune functions. In recent years, natural products (NPs) have been studied broadly for their multi-targeted activities under pathological conditions. Interestingly, several attempts have been made to outline the immunomodulatory properties of NPs. Research on in-vitro and in-vivo models have shown the immunomodulatory activity of NPs, is due to their antiinflammatory property, induction of phagocytosis and immune cells stimulation activity. Moreover, studies on humans have suggested that phytomedicines reduce inflammation and could provide appropriate benefits either in single form or complex combinations with other agents preventing disease progression, subsequently enhancing the efficacy of treatment to combat multiple malignancies. However, the exact mechanism of immunomodulation is far from clear, warranting more detailed investigations on their effectiveness. Nevertheless, the reduction of inflammatory cascades is considered as a prime protective mechanism in a number of inflammation regulated autoimmune diseases. Altogether, this review will discuss the biological activities of plant-derived secondary metabolites, such as polyphenols, alkaloids, saponins, polysaccharides and so forth, against various diseases and their potential use as an immunomodulatory agent under pathological conditions.

Immunomodulatory Effects of Dietary Polyphenols

Functional and nutraceutical foods provide an alternative way to improve immune function to aid in the management of various diseases. Traditionally, many medicinal products have been derived from natural compounds with healing properties. With the development of research into nutraceuticals, it is becoming apparent that many of the beneficial properties of these compounds are at least partly due to the presence of polyphenols. There is evidence that dietary polyphenols can influence dendritic cells, have an immunomodulatory effect on macrophages, increase proliferation of B cells, T cells and suppress Type 1 T helper (Th1), Th2, Th17 and Th9 cells. Polyphenols reduce inflammation by suppressing the pro-inflammatory cytokines in inflammatory bowel disease by inducing Treg cells in the intestine, inhibition of tumor necrosis factor-alpha (TNF-α) and induction of apoptosis, decreasing DNA damage. Polyphenols have a potential role in prevention/treatment of auto-immune diseases like type 1 diabetes, rheumatoid arthritis and multiple sclerosis by regulating signaling pathways, suppressing inflammation and limiting demyelination. In addition, polyphenols cause immunomodulatory effects against allergic reaction and autoimmune disease by inhibition of autoimmune T cell proliferation and downregulation of pro-inflammatory cytokines (interleukin-6 (IL-6), IL-1, interferon-γ (IFN-γ)). Herein, we summarize the immunomodulatory effects of polyphenols and the underlying mechanisms involved in the stimulation of immune responses.

Whey protein enriched with Stevia rebaudiana fraction restores the pancreatic function of streptozotocin induced diabetic rats

The study aims to analyse the treatment of whey protein enriched with Stevia rebaudiana fraction in insulin secretion and its role mitigating streptozotocin-induced hyperglycemia in rats. Thus, diabetic animals were treated with whey protein enriched with S. rebaudiana fraction or with only the protein isolate or only the Stevia fraction. Insulin level in plasma was measured by radioimmunoassay and the viability of β cells was detected by immunohistochemistry. The results showed that diabetic animals treated with whey protein enriched with S. rebaudiana fraction had a greater recovery from insulinemia, with plasma levels similar to non-diabetic animals (~ 0.13 ng/mL). In addition, the same group showed a higher number of insulin-positive pancreatic B cells (~ 66%) in immunohistochemistry analysis, while the diabetic groups treated with only the fraction of stevia or whey protein showed 38 and 59% of positive cells, respectively. These results show that the treatment may have restored the viability of streptozotocin-injured pancreatic B cells, and consequently increased insulin secretion, suggesting whey protein enriched with S. rebaudiana fraction can be used an adjunct/supplement in diabetic treatment.

The use of South African botanical species for the control of blood sugar

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetes mellitus (DM) is one of the most prevalent diseases globally and is of considerable concern to global health. Approximately 425 million people are estimated to have DM globally and this is predicted to increase to >642 million by 2040. Whilst the prevalence of DM in South Africa is slightly lower than the global average, it is expected to rise rapidly in future years as more South Africans adopt a high calorie "westernised" diet. Traditional medicines offer an alternative for the development of new medicines to treat DM and the usage of South African plants is relatively well documented.

AIM OF THE STUDY

To critically review the literature on the anti-diabetic properties of South African plants and to document plant species used for the treatment of DM. Thereafter, a thorough examination of the related research will highlight where research is lacking in the field.

MATERIALS AND METHODS

A review of published ethnobotanical books, reviews and primary scientific studies was undertaken to identify plants used to treat DM in traditional South African healing systems and to identify gaps in the published research. The study was non-biased, without taxonomic preference and included both native and introduced species. To be included, species must be recorded in the pharmacopeia of at least one South African ethnic group for the treatment of DM.

RESULTS

One hundred and thirty-seven species are recorded as therapies for DM, with leaves and roots most commonly used. The activity of only 43 of these species have been verified by rigorous testing, and relatively few studies have examined the mechanism of action.

CONCLUSION

Despite relatively extensive ethnobotanical records and a diverse flora, the anti-diabetic properties of South African medicinal plants is relatively poorly explored. The efficacy of most plants used traditionally to treat DM are yet to be verified and few mechanistic studies are available. Further research is required in this field.