Identification of a small molecular insulin receptor agonist with potent antidiabetes activity

Cynomorium songaricum: UHPLC/ESI-LTQ-Orbitrap-MS analysis and mechanistic study on insulin sensitivity of a flavonoid-enriched fraction

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized by elevated blood glucose levels, posing a significant global health concern due to its increasing prevalence. Insulin resistance (IR) plays a major role in the development of T2DM and is often linked to factors such as obesity, physical inactivity, and a sedentary lifestyle. Recently, there has been growing interest in exploring the potential of natural products for improving insulin sensitivity and glucose metabolism. Among these, Cynomorium songaricum Rupr., an edible parasitic plant, has shown promising antidiabetic effects. However, research on its beneficial effects on IR is still nascent. Therefore, this study aims to investigate the application of a Cynomorium songaricum flavonoid-enriched fraction (CSF) in the treatment of IR in T2DM, along with elucidating the chemical and biochemical mechanisms involved.

METHOD

First, UHPLC/ESI-LTQ-Orbitrap-MS was utilized to perform a chemical profiling of CSF. Subsequently, glycogen synthesis, gluconeogenesis and glucose consumption assays were conducted on HepG2 cells with a high glucose high insulin-induced IR model to illustrate the favorable impacts of CSF on IR. Then, an innovative network pharmacology analysis was executed to predict the potential chemical components and hub genes contributing to CSF's protective effect against IR. To further elucidate molecular interactions, molecular docking studies were performed, focusing on the binding interactions between active constituents of CSF and crucial targets. Additionally, an RNA-sequencing assay was employed to uncover the underlying biochemical signaling pathway responsible for CSF's beneficial effects. To validate these findings, western blot and qPCR assays were employed to verify the pathways related to IR and the potential signaling cascades leading to the amelioration of IR.

RESULTS

The UHPLC/ESI-LTQ-Orbitrap-MS analysis successfully identified a total of thirty-six flavonoids derived from CSF. Moreover, CSF was shown to significantly improve glycogen synthesis and glucose consumption as well as inhibit gluconeogenesis in HepG2 cells of IR. An innovative network pharmacology analysis unveiled key hub genes-AKT1 and PI3K-integral to metabolic syndrome-related signaling pathways, which contributed to the favorable impact of CSF against IR. Noteworthy active ingredients including quercetin, ellagic acid and naringenin were identified as potential contributors to these effects. The results of western blot and qPCR assays provided compelling evidence that CSF improved insulin sensitivity by modulating the PI3K-Akt signaling pathway. Subsequent RNA-sequencing analysis, in tandem with western blot assays, delved deeper into the potential mechanisms underlying CSF's advantageous effects against IR, potentially associated with the enhancement of endoplasmic reticulum (ER) proteostasis.

CONCLUSION

CSF exhibited a remarkable ability to enhance insulin sensitivity in the IR model of HepG2 cells. This was evident through enhancements in glycogen synthesis and glucose consumption, along with its inhibitory impact on gluconeogenesis. Furthermore, CSF demonstrated an improvement in the insulin-mediated PI3K-Akt signaling pathway. The potential active constituents were identified as quercetin, ellagic acid and naringenin. The underlying biochemical mechanisms responsible for CSF's beneficial effects against IR were closely linked to its capacity to mitigate ER stress, thereby offering a comprehensive understanding of its protective action.

Fishing the Targets of Bioactive Compounds from Psidium guajava L. Leaves in the Context of Diabetes

Psidium guajava L. (guava) leaves have demonstrated their in vitro and in vivo effect against diabetes mellitus (DM). However, there is a lack of literature concerning the effect of the individual phenolic compounds present in the leaves in DM disease. The aim of the present work was to identify the individual compounds in Spanish guava leaves and their potential contribution to the observed anti-diabetic effect. Seventy-three phenolic compounds were identified from an 80% ethanol extract of guava leaves by high performance liquid chromatography coupled to electrospray ionization and quadrupole time-of-flight mass spectrometry. The potential anti-diabetic activity of each compound was evaluated with the DIA-DB web server that uses a docking and molecular shape similarity approach. The DIA-DB web server revealed that aldose reductase was the target protein with heterogeneous affinity for compounds naringenin, avicularin, guaijaverin, quercetin, ellagic acid, morin, catechin and guavinoside C. Naringenin exhibited the highest number of interactions with target proteins dipeptidyl peptidase-4, hydroxysteroid 11-beta dehydrogenase 1, aldose reductase and peroxisome proliferator-activated receptor. Compounds catechin, quercetin and naringenin displayed similarities with the known antidiabetic drug tolrestat. In conclusion, the computational workflow showed that guava leaves contain several compounds acting in the DM mechanism by interacting with specific DM protein targets.

Epitope mapping of a blood-brain barrier crossing antibody targeting the cysteine-rich region of IGF1R using hydrogen-exchange mass spectrometry enabled by electrochemical reduction

Pathologies of the central nervous system impact a significant portion of our population, and the delivery of therapeutics for effective treatment is challenging. The insulin-like growth factor-1 receptor (IGF1R) has emerged as a target for receptor-mediated transcytosis, a process by which antibodies are shuttled across the blood-brain barrier (BBB). Here, we describe the biophysical characterization of VHH-IR4, a BBB-crossing single-domain antibody (sdAb). Binding was confirmed by isothermal titration calorimetry and an epitope was highlighted by surface plasmon resonance that does not overlap with the IGF-1 binding site or other known BBB-crossing sdAbs. The epitope was mapped with a combination of linear peptide scanning and hydrogen-deuterium exchange mass spectrometry (HDX-MS). IGF1R is large and heavily disulphide bonded, and comprehensive HDX analysis was achieved only through the use of online electrochemical reduction coupled with a multiprotease approach, which identified an epitope for VHH-IR4 within the cysteine-rich region (CRR) of IGF1R spanning residues W244-G265. This is the first report of an sdAb binding the CRR. We show that VHH-IR4 inhibits ligand induced auto-phosphorylation of IGF1R and that this effect is mediated by downstream conformational effects. Our results will guide the selection of antibodies with improved trafficking and optimized IGF1R binding characteristics.

Regulation of Podocyte Injury by CircHIPK3/FUS Complex in Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a major microvascular complication of diabetes mellitus and is one of the leading causes of end-stage kidney disease. Circular RNAs (circRNAs) are a class of endogenous non-coding RNAs that play important roles in various diseases, yet their roles in DKD are poorly understood. CircRNA HIPK3 (circHIPK3), a highly conserved circRNA, is closely related to various cellular functions, including cell proliferation and apoptosis. The association between circHIPK3 and diabetic complications has been well demonstrated in multiple previous studies. However, the role of circHIPK3 in podocyte injury in DKD remains unclear. Herein, we discovered that circHIPK3 expression is markedly elevated in cultured podocytes under high-glucose (HG) conditions and glomeruli of diabetic mice, which is closely associated with podocyte injury in DKD. Functionally, lentivirus-mediated knockdown of circHIPK3 dramatically suppresses HG-induced podocyte apoptosis in vitro. Therapeutically, silencing circHIPK3 by adeno-associated virus-mediated RNA interference ameliorates podocyte injury and albuminuria in STZ-induced diabetic mice. Mechanistically, circHIPK3 facilitates the enrichment of fused in sarcoma (FUS) on the ectodysplasin A2 receptor (EDA2R) promoter, resulting in the upregulation of EDA2R expression and activation of apoptotic signaling. Taken together, these results indicate circHIPK3/FUS/EDA2R axis as a therapeutic target for podocyte injury and DKD progression.

The Insulin Receptor: An Important Target for the Development of Novel Medicines and Pesticides

The insulin receptor (IR) is a transmembrane protein that is activated by ligands in insulin signaling pathways. The IR has been considered as a novel therapeutic target for clinical intervention, considering the overexpression of its protein and A-isoform in multiple cancers, Alzheimer's disease, and Type 2 diabetes mellitus in humans. Meanwhile, it may also serve as a potential target in pest management due to its multiple physiological influences in insects. In this review, we provide an overview of the structural and molecular biology of the IR, functions of IRs in humans and insects, physiological and nonpeptide small molecule modulators of the IR, and the regulating mechanisms of the IR. Xenobiotic compounds and the corresponding insecticidal chemicals functioning on the IR are also discussed. This review is expected to provide useful information for a better understanding of human IR-related diseases, as well as to facilitate the development of novel small-molecule activators and inhibitors of the IR for use as medicines or pesticides.

Hirsutine ameliorates hepatic and cardiac insulin resistance in high-fat diet-induced diabetic mice and in vitro models

Closely associated with type 2 diabetes mellitus (T2DM), hepatic steatosis and cardiac hypertrophy resulting from chronic excess intake can exacerbate insulin resistance (IR). The current study aims to investigate the pharmacological effects of hirsutine, one indole alkaloid isolated from Uncaria rhynchophylla, on improving hepatic and cardiac IR, and elucidate the underlying mechanism. T2DM and IR in vivo were established by high-fat diet (HFD) feeding for 3 months in C57BL/6 J mice. In vitro IR models were induced by high-glucose and high-insulin (HGHI) incubation in HepG2 and H9c2 cells. Hirsutine administration for 8 weeks improved HFD-induced peripheral hyperglycemia, glucose tolerance and IR by OGTT and ITT assays, and simultaneously attenuated hepatic steatosis and cardiac hypertrophy by pathological observation. The impaired p-Akt expression was activated by hirsutine in liver and heart tissues of HFD mice, and also in the models in vitro. Hirsutine exhibited the effects on enhancing glucose consumption and uptake in IR cell models via activating phosphatidylinositol 3-kinase (PI3K)/Akt pathway, which was blocked by PI3K inhibitor LY294002. Moreover, the effect of hirsutine on promoting glucose uptake and GLUT4 expression in HGHI H9c2 cells was also prevented by Compound C, an inhibitor of AMP-activated protein kinase (AMPK). Enhancement of glycolysis might be another factor of hirsutine showing its effects on glycemic control. Collectively, it was uncovered that hirsutine might exert beneficial effects on regulating glucose homeostasis, thus improving hepatic and cardiac IR, and could be a promising compound for treating diet-induced T2DM.

Functionally selective signaling and broad metabolic benefits by novel insulin receptor partial agonists

Insulin analogs have been developed to treat diabetes with focus primarily on improving the time action profile without affecting ligand-receptor interaction or functional selectivity. As a result, inherent liabilities (e.g. hypoglycemia) of injectable insulin continue to limit the true therapeutic potential of related agents. Insulin dimers were synthesized to investigate whether partial agonism of the insulin receptor (IR) tyrosine kinase is achievable, and to explore the potential for tissue-selective systemic insulin pharmacology. The insulin dimers induced distinct IR conformational changes compared to native monomeric insulin and substrate phosphorylation assays demonstrated partial agonism. Structurally distinct dimers with differences in conjugation sites and linkers were prepared to deliver desirable IR partial agonist (IRPA). Systemic infusions of a B29-B29 dimer in vivo revealed sharp differences compared to native insulin. Suppression of hepatic glucose production and lipolysis were like that attained with regular insulin, albeit with a distinctly shallower dose-response. In contrast, there was highly attenuated stimulation of glucose uptake into muscle. Mechanistic studies indicated that IRPAs exploit tissue differences in receptor density and have additional distinctions pertaining to drug clearance and distribution. The hepato-adipose selective action of IRPAs is a potentially safer approach for treatment of diabetes.

Structure-based survey of ligand binding in the human insulin receptor

The insulin receptor is a membrane protein responsible for regulation of nutrient balance and therefore an attractive target in the treatment of diabetes and metabolic syndrome. Pharmacology of the insulin receptor involves two distinct mechanisms, (1) activation of the receptor by insulin mimetics that bind in the extracellular domain and (2) inhibition of the receptor tyrosine kinase enzymatic activity in the cytoplasmic domain. While a complete structural picture of the full-length receptor comprising the entire sequence covering extracellular, transmembrane, juxtamembrane and cytoplasmic domains is still elusive, recent progress through cryoelectron microscopy has made it possible to describe the initial insulin ligand binding events at atomistic detail. We utilize this opportunity to obtain structural insights into the pharmacology of the insulin receptor. To this end, we conducted a comprehensive docking study of known ligands to the new structures of the receptor. Through this approach, we provide an in-depth, structure-based review of human insulin receptor pharmacology in light of the new structures.

Molecular Docking and Simulation Studies of Antidiabetic Agents Devised from Hypoglycemic Polypeptide-P of Momordica charantia

Diabetes mellitus termed as metabolic disorder is a collection of interlinked diseases and mainly body's inability to manage glucose level which leads to cardiovascular diseases, renal failure, neurological disorders, and many others. The drugs contemporarily used for diabetes have many inevitable side effects, and many of them have become less responsive to this multifactorial disorder. Momordica charantia commonly known as bitter gourd has many bioactive compounds with antidiabetic properties. The current study was designed to use computational methods to discover the best antidiabetic peptides devised from hypoglycemic polypeptide-P of M. charantia. The binding affinity and interaction patterns of peptides were evaluated against four receptor proteins (i.e., as agonists of insulin receptor and inhibitors of sodium-glucose cotransporter 1, dipeptidyl peptidase-IV, and glucose transporter 2) using molecular docking approach. A total of thirty-seven peptides were docked against these receptors. Out of which, top five peptides against each receptor were shortlisted based on their S-scores and binding affinities. Finally, the eight best ligands (i.e., LIVA, TSEP, EKAI, LKHA, EALF, VAEK, DFGAS, and EPGGGG) were selected as these ligands strictly followed Lipinski's rule of five and exhibited good ADMET profiling. One peptide EPGGGG showed activity towards insulin and SGLT1 receptor proteins. The top complex for both these targets was subjected to 50 ns of molecular dynamics simulations and MM-GBSA binding energy test that concluded both complexes as highly stable, and the intermolecular interactions were dominated by van der Waals and electrostatic energies. Overall, the selected ligands strongly fulfilled the drug-like evaluation criterion and proved to have good antidiabetic properties.

Dimeric Drugs

This review intends to summarize the structures of an extensive number of symmetrical-dimeric drugs, having two monomers linked via a bridging entity while emphasizing the large versatility of biologically active substances reported to possess dimeric structures. The largest number of classes of these compounds consist of anticancer agents, antibiotics/antimicrobials, and anti-AIDS drugs. Other symmetrical-dimeric drugs include antidiabetics, antidepressants, analgesics, anti-inflammatories, drugs for the treatment of Alzheimer's disease, anticholesterolemics, estrogenics, antioxidants, enzyme inhibitors, anti-Parkisonians, laxatives, antiallergy compounds, cannabinoids, etc. Most of the articles reviewed do not compare the activity/potency of the dimers to that of their corresponding monomers. Only in limited cases, various suggestions have been made to justify unexpected higher activity of the dimers vs. the corresponding monomers. These suggestions include statistical effects, the presence of dimeric receptors, binding of a dimer to two receptors simultaneously, and others. It is virtually impossible to predict which dimers will be preferable to their respective monomers, or which linking bridges will lead to the most active compounds. It is expected that the extensive number of articles summarized, and the large variety of substances mentioned, which display various biological activities, should be of interest to many academic and industrial medicinal chemists.

Defining the epitope of a blood-brain barrier crossing single domain antibody specific for the type 1 insulin-like growth factor receptor

Ligand-activated signaling through the type 1 insulin-like growth factor receptor (IGF1R) is implicated in many physiological processes ranging from normal human growth to cancer proliferation and metastasis. IGF1R has also emerged as a target for receptor-mediated transcytosis, a transport phenomenon that can be exploited to shuttle biotherapeutics across the blood–brain barrier (BBB). We employed differential hydrogen–deuterium exchange mass spectrometry (HDX-MS) and nuclear magnetic resonance (NMR) to characterize the interactions of the IGF1R ectodomain with a recently discovered BBB-crossing single-domain antibody (sdAb), VHH-IR5, in comparison with IGF-1 binding. HDX-MS confirmed that IGF-1 induced global conformational shifts in the L1/FnIII-1/-2 domains and α-CT helix of IGF1R. In contrast, the VHH-IR5 sdAb-mediated changes in conformational dynamics were limited to the α-CT helix and its immediate vicinity (L1 domain). High-resolution NMR spectroscopy titration data and linear peptide scanning demonstrated that VHH-IR5 has high-affinity binding interactions with a peptide sequence around the C-terminal region of the α-CT helix. Taken together, these results define a core linear epitope for VHH-IR5 within the α-CT helix, overlapping the IGF-1 binding site, and suggest a potential role for the α-CT helix in sdAb-mediated transcytosis.

Natural Compound α-PGG and Its Synthetic Derivative 6Cl-TGQ Alter Insulin Secretion: Evidence for Diminishing Glucose Uptake as a Mechanism

PURPOSE

Previously we showed that natural compound α-penta-galloyl-glucose (α-PGG) and its synthetic derivative 6-chloro-6-deoxy-1,2,3,4-tetra-O-galloyl-α-D-glucopyranose (6Cl-TGQ) act to improve insulin signaling in adipocytes by increasing glucose transport. In this study, we investigated the mechanism of actions of α-PGG and 6Cl-TGQ on insulin secretion.

METHODS

Mouse islets and/or INS-1832/13 beta-cells were used to test the effects of our compounds on glucose-stimulated insulin secretion (GSIS), intracellular calcium [Ca²⁺]_i using fura-2AM, glucose transport activity via a radioactive glucose uptake assay, intracellular ATP/ADP, and extracellular acidification (ECAR) and mitochondrial oxygen consumption rates (OCAR) using Seahorse metabolic analysis.

RESULTS

Both compounds reduced GSIS in beta-cells without negatively affecting cell viability. The compounds primarily diminished glucose uptake into islets and beta-cells. Despite insulin-like effects in the peripheral tissues, these compounds do not act through the insulin receptor in islets. Further interrogation of the stimulus-secretion pathway showed that all the key metabolic factors involved in GSIS including ECAR, OCAR, ATP/ADP ratios, and [Ca²⁺]_i of INS-1832/13 cells were diminished after the compound treatment.

CONCLUSION

The compounds suppress glucose uptake of the beta-cells, which consequently slows down the rates of glycolysis and ATP synthesis, leading to decrease in [Ca²⁺]_i and GSIS. The difference between adipocytes and beta-cells in effects on glucose uptake is of great interest. Further structural and functional modifications could produce new compounds with optimized therapeutic potentials for different target cells. The higher potency of synthetic 6Cl-TGQ in enhancing insulin signaling in adipocytes but lower potency in reducing glucose uptake in beta-cells compared to α-PGG suggests the feasibility of such an approach.

Effect of the interaction between ribosomal protein L10a and insulin receptor on carbohydrate metabolism

The number of patients with insulin-resistant diabetes has significantly increased. Thus, alternative insulin mimetics are required for such patients. Some evidences indicate that ribosomal protein L10a (RpL10a) is involved in the insulin pathway. In addition, we previously demonstrated that recombinant RpL10a from Fenneropenaeus merguiensis (Fm-RpL10a) could stimulate cell proliferation and trehalose metabolism in RpL10a–over-expressing flies by inducing insulin receptor (InR) expression and some insulin signaling mediators phosphorylation. In this study, we investigated the in silico binding between Fm-RpL10a and InR. The results indicated that Fm-RpL10a bound to InR at residues 635–640 and 697–702 of the FnIII2 domain. This binding was confirmed using a pull-down and immunofluorescence assay. Further analysis indicated that Fm-RpL10a could stimulate glucose utilisation by insulin-resistant cells (IRCs) and healthy cells. Additionally, Fm-RpL10a at a low concentration (1 μg/ml) altered some glucose metabolism-related genes expression in Fm-RpL10a treated IRCs. The qRT-PCR result revealed the up-regulation of Hk1, which encode key enzymes in glycolysis. Conversely, the expression of G6pc3, which participates in gluconeogenesis, was down-regulated. Overall, the results suggest that Fm-RpL10a can alleviate insulin resistance by stimulating insulin signaling via the FnIII2 domain of InR and activate glycolysis. Therefore, Fm-RpL10a may be a candidate insulin mimetic for the treatment of diabetes.

Discovery of Prenyltransferase Inhibitors with In Vitro and In Vivo Antibacterial Activity

Cis-prenyltransferases such as undecaprenyl diphosphate synthase (UPPS) and decaprenyl diphosphate synthase (DPPS) are essential enzymes in bacteria and are involved in cell wall biosynthesis. UPPS and DPPS are absent in the human genome, so they are of interest as targets for antibiotic development. Here, we screened a library of 750 compounds from National Cancer Institute Diversity Set V for the inhibition of Mycobacterium tuberculosis DPPS and found 17 hits, and then IC₅₀s were determined using dose-response curves. Compounds were tested for growth inhibition against a panel of bacteria, for in vivo activity in a Staphylococcus aureus/Caenorhabditis elegans model, and for mammalian cell toxicity. The most active DPPS inhibitor was the dicarboxylic acid redoxal (compound 10), which also inhibited undecaprenyl diphosphate synthase (UPPS) as well as farnesyl diphosphate synthase. 10 was active against S. aureus, Clostridiodes difficile, Bacillus anthracis Sterne, and Bacillus subtilis, and there was a 3.4-fold increase in IC₅₀ on addition of a rescue agent, undecaprenyl monophosphate. We found that 10 was also a weak protonophore uncoupler, leading to the idea that it targets both isoprenoid biosynthesis and the proton motive force. In an S. aureus/C. elegans in vivo model, 10 reduced the S. aureus burden 3 times more effectively than did ampicillin.

Recent advances of BINOL-based sensors for enantioselective fluorescence recognition

Enantioselective fluorescent sensors show large potential for fast, real-time, and highly sensitive measurement of the concentration and enantiomeric composition of chiral molecules. Among all of the sensors, BINOL-based sensors have been actively investigated and extensively used to carry out highly enantioselective, sensitive recognition of chiral α-hydroxycarboxylic acids, amino acids, amino acid derivatives, amino alcohols and amines. In this manuscript, the recent progress of chiral BINOL-based sensors for enantioselective fluorescence recognition of different substrates is reviewed and discussed. The structure of BINOL is tuned by introducing various groups or molecules which systematically changed its fluorescence properties and offered potential for rapid assays of chiral organic molecules. From the development of this area, we gain fresh insight into the challenges and chances of BINOL-based sensors.

Selection of Small Molecules that Bind to and Activate the Insulin Receptor from a DNA-Encoded Library of Natural Products

Although insulin is a life-saving medicine, administration by daily injection remains problematic. Our goal was to exploit the power of DNA-encoded libraries to identify molecules with insulin-like activity but with the potential to be developed as oral drugs. Our strategy involved using a 10⁴-member DNA-encoded library containing 160 Traditional Chinese Medicines (nDEL) to identify molecules that bind to and activate the insulin receptor. Importantly, we used the natural ligand, insulin, to liberate bound molecules. Using this selection method on our relatively small, but highly diverse, nDEL yielded a molecule capable of both binding to and activating the insulin receptor. Chemical analysis showed this molecule to be a polycyclic analog of the guanidine metformin, a known drug used to treat diabetes. By using our protocol with other, even larger, DELs we can expect to identify additional organic molecules capable of binding to and activating the insulin receptor.

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Annotation of natural products via complementary bifunctional linkers

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Function-guided DEL selection using the natural ligand for competitive elution

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Identification of Rutaecarpine as a binder and activator of insulin receptor

Non-peptidyl small molecule, adenosine, 5'-Se-methyl-5'-seleno-, 2',3'-diacetate, activates insulin receptor and attenuates hyperglycemia in type 2 diabetic Leprdb/db mice

The pathophysiology of type 2 diabetes mellitus (T2D) is characterized by reduced or absent insulin receptor (INSR) responsiveness to its ligand, elevated hepatic glucose output and impaired glucose uptake in peripheral tissues, particularly skeletal muscle. Treatments to reduce hyperglycemia and reestablish normal insulin signaling are much sought after. Any agent which could be orally administered to restore INSR function, in an insulin-independent manner, would have major implications for the management of this global disease. We have discovered a non-peptidyl small molecule, adenosine, 5'-Se-methyl-5'-seleno-, 2',3'-diacetate [referred to as non-peptidyl compound #43 (NPC43)], which restores INSR signaling in the complete absence of insulin. Initial screening of numerous compounds in human HepG2 liver cells revealed that NPC43 significantly inhibited glucose production. The compound was potently anti-hyperglycemic and anti-hyperinsulinemic in vivo, in insulin-resistant T2D Leprdb/db mice, following either acute or chronic treatment by oral gavage and intraperitoneal injection, respectively. The compound acted at the level of INSR and activated it in both liver and skeletal muscle of Leprdb/db mice. In cell culture, the compound activated INSR in both liver and skeletal muscle cells; furthermore, it cooperated with insulin to depress glucose-6-phosphatase catalytic subunit (G6pc) expression and stimulate glucose uptake, respectively. Our results indicated that the compound directly interacted with INSRα, triggering appropriate phosphorylation and activation of the receptor and its downstream targets. Unlike insulin, NPC43 did not activate insulin-like growth factor 1 receptor in either liver or skeletal muscle. We believe this compound represents a potential oral and/or injectable insulin replacement therapy for diabetes and diseases associated with insulin resistance.

Developing Insulin and BDNF Mimetics for Diabetes Therapy

Diabetes is a global public health concern nowadays. The majority of diabetes mellitus (DM) patients belong to type 2 diabetes mellitus (T2DM), which is highly associated with obesity. The general principle of current therapeutic strategies for patients with T2DM mainly focuses on restoring cellular insulin response by potentiating the insulin-induced signaling pathway. In late-stage T2DM, impaired insulin production requires the patients to receive insulin replacement therapy for maintaining their glucose homeostasis. T2DM patients also demonstrate a drop of brain-derived neurotrophic factor (BDNF) in their circulation, which suggests that replenishing BDNF or enhancing its downstream signaling pathway may be beneficial. Because of their protein nature, recombinant insulin or BDNF possess several limitations that hinder their clinical application in T2DM treatment. Thus, developing orally active "insulin pill" or "BDNF pill" is essential to provide a more convenient and effective therapy. This article reviews the current development of non-peptidyl chemicals that mimic insulin or BDNF and their potential as anti-diabetic agents.

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.

Regulation of glucose and lipid metabolism in health and disease

Glucose and fatty acids are the major sources of energy for human body. Cholesterol, the most abundant sterol in mammals, is a key component of cell membranes although it does not generate ATP. The metabolisms of glucose, fatty acids and cholesterol are often intertwined and regulated. For example, glucose can be converted to fatty acids and cholesterol through de novo lipid biosynthesis pathways. Excessive lipids are secreted in lipoproteins or stored in lipid droplets. The metabolites of glucose and lipids are dynamically transported intercellularly and intracellularly, and then converted to other molecules in specific compartments. The disorders of glucose and lipid metabolism result in severe diseases including cardiovascular disease, diabetes and fatty liver. This review summarizes the major metabolic aspects of glucose and lipid, and their regulations in the context of physiology and diseases.

Activation of Insulin Signaling in Adipocytes and Myotubes by Sarcopoterium Spinosum Extract

Sarcopoterium spinosum (S. spinosum) is a medicinal plant, traditionally used as an antidiabetic remedy. Previous studies demonstrated its beneficial properties in the treatment of insulin resistance. The aim of this study was to further clarify the effect of S. spinosum extract (SSE) on insulin signaling. Phosphoproteomic analysis, performed in 3T3-L1 adipocytes treated with SSE, revealed the activation of insulin receptor pathways. SSE increased Glut4-facilitated glucose uptake in adipocytes, with an additive effect between SSE and insulin. While the maximal effect of insulin on glucose uptake was found at days 15–16 of differentiation, SSE-induced glucose uptake was found at an earlier stage of differentiation. Inhibition of PI3K and Akt blocked SSE-dependent glucose uptake. Western blot analysis, performed on 3T3-L1 adipocytes and L6 myotubes, showed that in contrast to insulin action, Akt was only marginally phosphorylated by SSE. Furthermore, GSK3β and PRAS40 phosphorylation as well as glucose uptake were increased by the extract. SSE also induced the phosphorylation of ERK similar to insulin. In conclusion, SSE activates insulin signaling, although the upstream event mediating its effects should be further clarified. Identifying the active molecules in SSE may lead to the development of new agents for the treatment of insulin resistance.

Ellagic Acid, Kaempferol, and Quercetin from Acacia nilotica: Promising Combined Drug With Multiple Mechanisms of Action

The pharmacological activity of Acacia nilotica's phytochemical constituents was confirmed with evidence-based studies, but the determination of exact targets that they bind and the mechanism of action were not done; consequently, we aim to identify the exact targets that are responsible for the pharmacological activity via the computational methods. Furthermore, we aim to predict the pharmacokinetics (ADME) properties and the safety profile in order to identify the best drug candidates. To achieve those goals, various computational methods were used including the ligand-based virtual screening and molecular docking. Moreover, pkCSM and SwissADME web servers were used for the prediction of pharmacokinetics and safety. The total number of the investigated compounds and targets was 25 and 61, respectively. According to the results, the pharmacological activity was attributed to the interaction with essential targets. Ellagic acid, Kaempferol, and Quercetin were the best A. nilotica's phytochemical constituents that contribute to the therapeutic activities, were non-toxic as well as non-carcinogen. The administration of Ellagic acid, Kaempferol, and Quercetin as combined drug via the novel drug delivery systems will be a valuable therapeutic choice for the treatment of recent diseases attacking the public health including cancer, multidrug-resistant bacterial infections, diabetes mellitus, and chronic inflammatory systemic disease.

Comprehensive review on the interaction between natural compounds and brain receptors: Benefits and toxicity

Given their therapeutic activity, natural products have been used in traditional medicines throughout the centuries. The growing interest of the scientific community in phytopharmaceuticals, and more recently in marine products, has resulted in a significant number of research efforts towards understanding their effect in the treatment of neurodegenerative diseases, such as Alzheimer's (AD), Parkinson (PD) and Huntington (HD). Several studies have shown that many of the primary and secondary metabolites of plants, marine organisms and others, have high affinities for various brain receptors and may play a crucial role in the treatment of diseases affecting the central nervous system (CNS) in mammalians. Actually, such compounds may act on the brain receptors either by agonism, antagonism, allosteric modulation or other type of activity aimed at enhancing a certain effect. The current manuscript comprehensively reviews the state of the art on the interactions between natural compounds and brain receptors. This information is of foremost importance when it is intended to investigate and develop cutting-edge drugs, more effective and with alternative mechanisms of action to the conventional drugs presently used for the treatment of neurodegenerative diseases. Thus, we reviewed the effect of 173 natural products on neurotransmitter receptors, diabetes related receptors, neurotrophic factor related receptors, immune system related receptors, oxidative stress related receptors, transcription factors regulating gene expression related receptors and blood-brain barrier receptors.

A high-throughput chemical-genetics screen in murine adipocytes identifies insulin-regulatory pathways

Pathways linking activation of the insulin receptor to downstream targets of insulin have traditionally been studied using a candidate gene approach. To elucidate additional pathways regulating insulin activity, we performed a forward chemical-genetics screen based on translocation of a glucose transporter 4 (Glut4) reporter expressed in murine 3T3-L1 adipocytes. To identify compounds with known targets, we screened drug-repurposing and natural product libraries. We identified, confirmed, and validated 64 activators and 65 inhibitors that acutely increase or rapidly decrease cell-surface Glut4 in adipocytes stimulated with submaximal insulin concentrations. These agents were grouped by target, chemical class, and mechanism of action. All groups contained multiple hits from a single drug class, and several comprised multiple structurally unrelated hits for a single target. Targets include the β-adrenergic and adenosine receptors. Agonists of these receptors increased and inverse agonists/antagonists decreased cell-surface Glut4 independently of insulin. Additional activators include insulin sensitizers (thiazolidinediones), insulin mimetics, dis-inhibitors (the mTORC1 inhibitor rapamycin), cardiotonic steroids (the Na⁺/K⁺-ATPase inhibitor ouabain), and corticosteroids (dexamethasone). Inhibitors include heterocyclic amines (tricyclic antidepressants) and 21 natural product supplements and herbal extracts. Mechanisms of action include effects on Glut4 trafficking, signal transduction, inhibition of protein synthesis, and dissipation of proton gradients. Two pathways that acutely regulate Glut4 translocation were discovered: de novo protein synthesis and endocytic acidification. The mechanism of action of additional classes of activators (tanshinones, dalbergiones, and coumarins) and inhibitors (flavonoids and resveratrol) remains to be determined. These tools are among the most sensitive, responsive, and reproducible insulin-activity assays described to date.

Treatment of type 2 diabetes: future approaches

INTRODUCTION OR BACKGROUND

Type 2 diabetes, which accounts for ~90% of all diabetes, is a heterogeneous and progressive disease with a variety of causative and potentiating factors. The hyperglycaemia of type 2 diabetes is often inadequately controlled, hence the need for a wider selection of glucose-lowering treatments.

SOURCES OF DATA

Medline, PubMed, Web of Science and Google Scholar.

AREAS OF AGREEMENT

Early, effective and sustained control of blood glucose defers the onset and reduces the severity of microvascular and neuropathic complications of type 2 diabetes and helps to reduce the risk of cardiovascular (CV) complications.

AREAS OF CONTROVERSY

Newer glucose-lowering agents require extensive long-term studies to confirm CV safety. The positioning of newer agents within therapeutic algorithms varies.

GROWING POINTS

In addition to their glucose-lowering efficacy, some new glucose-lowering agents may act independently to reduce CV and renal complications.

AREAS TIMELY FOR DEVELOPING RESEARCH

Studies of potential new glucose-lowering agents offer the opportunity to safely improve glycaemic control with prolonged efficacy and greater opportunity for therapeutic individualisation.

Pathophysiology of cardiovascular disease in diabetes mellitus

Diabetes mellitus elicits cellular, epigenetic, and post-translational changes that directly or indirectly affect the biology of the vasculature and other metabolic systems resulting in the apparition of cardiovascular disease. In this review, we provide a current perspective on the most recent discoveries in this field, with particular focus on hyperglycemia- induced pathology in the cardiovascular system. We also provide perspective on the clinical importance of molecular targeting of cardiovascular and diabetes mellitus therapies to treat hyperglycemia, inflammation, thrombosis, dyslipidemia, atherosclerosis, and hypertension.

Glucose-lowering therapies in type 2 diabetes: Opportunities and challenges for peptides

This overview considers the opportunities and challenges that face the use of gluco-regulatory peptides to treat type 2 diabetes. New insulin analogues and formulations are being developed with pharmacokinetic properties to speed-up or prolong transfer from a subcutaneous injection site to the target tissues, or to selectively favour effects on the liver. Alternative routes of insulin administration continue to attract attention, and advances in the integration of glucose monitoring with insulin pump devices are improving miniaturised 'closed loop' artificial pancreas systems. Proof of concept has been established for non-cellular glucose-responsive insulin delivery ('smart insulins') to release insulin from implants or circulating depots in proportion to circulating glucose. The many peptides involved in blood glucose control offer diverse therapeutic opportunities. Exploitation of multiple selected receptor targets using constructs of hybrid and chimeric peptides, especially those based on glucagon and gastrointestinal hormones, has gained much credence from initial preclinical studies. Peptide templates identified from comparative endocrine studies have also provided valuable insights in this respect and indicated novel approaches to address associated conditions such as obesity and infections at the same time. Nevertheless, there are many challenges to the use of therapeutic peptides that impose on every step in the complex pathway from design and testing through to making a fully characterised therapeutic product, and optimising administration, tissue targeting and degradation. Stability of peptides and immunological uncertainties of novel structures require particular consideration as well as the need to avoid over-reduction of blood glucose into hypoglycaemia.

BINOL derivatives with aggression-induced emission

A new series of BINOL derivatives were synthesized which could be turned from ACQ to AIE fluorophores by changing the electron withdrawing group.

Structure and dynamics of the insulin receptor: implications for receptor activation and drug discovery

Recently, major progress has been made in uncovering the mechanisms of how insulin engages its receptor and modulates downstream signal transduction. Here, we present in detail the current structural knowledge surrounding the individual components of the complex, binding sites, and dynamics during the activation process. A novel kinase triggering mechanism, the 'bow-arrow model', is proposed based on current knowledge and computational simulations of this system, in which insulin, after its initial interaction with binding site 1, engages with site 2 between the fibronectin type III (FnIII)-1 and -2 domains, which changes the conformation of FnIII-3 and eventually translates into structural changes across the membrane. This model provides a new perspective on the process of insulin binding to its receptor and, thus, could lead to future novel drug discovery efforts.

A Small Insulinomimetic Molecule Also Improves Insulin Sensitivity in Diabetic Mice

Dramatic increase of diabetes over the globe is in tandem with the increase in insulin requirement. This is because destruction and dysfunction of pancreatic β-cells are of common occurrence in both Type1 diabetes and Type2 diabetes, and insulin injection becomes a compulsion. Because of several problems associated with insulin injection, orally active insulin mimetic compounds would be ideal substitute. Here we report a small molecule, a peroxyvanadate compound i.e. DmpzH[VO(O2)2(dmpz)], henceforth referred as dmp, which specifically binds to insulin receptor with considerable affinity (KD-1.17μM) thus activating insulin receptor tyrosine kinase and its downstream signaling molecules resulting increased uptake of [14C] 2 Deoxy-glucose. Oral administration of dmp to streptozotocin treated BALB/c mice lowers blood glucose level and markedly stimulates glucose and fatty acid uptake by skeletal muscle and adipose tissue respectively. In db/db mice, it greatly improves insulin sensitivity through excess expression of PPARγ and its target genes i.e. adiponectin, CD36 and aP2. Study on the underlying mechanism demonstrated that excess expression of Wnt3a decreased PPARγ whereas dmp suppression of Wnt3a gene increased PPARγ expression which subsequently augmented adiponectin. Increased production of adiponectin in db/db mice due to dmp effected lowering of circulatory TG and FFA levels, activates AMPK in skeletal muscle and this stimulates mitochondrial biogenesis and bioenergetics. Decrease of lipid load along with increased mitochondrial activity greatly improves energy homeostasis which has been found to be correlated with the increased insulin sensitivity. The results obtained with dmp, therefore, strongly indicate that dmp could be a potential candidate for insulin replacement therapy.

Prediction of a novel internal rearrangement of the insulin receptor

The insulin receptor (IR) plays critical roles in metabolism and growth, directed by the binding of insulin. Decades of research to understand the mechanism of insulin binding and activation of the IR have identified a region of the receptor, the C-terminal (CT) peptide, to be crucial for insulin binding. In particular, a truncated IR consisting of the first three domains fused to the CT peptide was found to bind insulin with nanomolar affinity, with undetectable binding in the absence of fused or soluble CT peptide. Problematically, all current crystal structures of the IR indicate the fusion point of the CT peptide to the three domains is located far from the position of the CT peptide as resolved in such structures. We have attempted to address this problem using molecular modelling and dynamics simulations. The results led to the identification of a potential inter-domain interaction between the L2 domain and the CT peptide that is not observed in any of the crystal structures of the IR. Investigations into this new interaction found a conformational change that could potentially be in response to insulin binding. Additionally, further simulation work with the new conformation demonstrated its compatibility with the position and orientation of insulin from the latest insulin-bound IR crystal structure.

Pursuit of a perfect insulin

Insulin remains indispensable in the treatment of diabetes, but its use is hampered by its narrow therapeutic index. Although advances in peptide chemistry and recombinant DNA-based macromolecule synthesis have enabled the synthesis of structurally optimized insulin analogues, the growing epidemics of obesity and diabetes have emphasized the need for diabetes therapies that are more efficacious, safe and convenient. Accordingly, a broad set of drug candidates, targeting hyperglycaemia plus other disease abnormalities, is now progressing through the clinic. The development of an insulin therapy that is responsive to glucose concentration remains an ultimate goal, with initial prototypes now reaching the proof-of-concept stage. Simultaneously, the first alternatives to injectable delivery have progressed to registration.

Higher-Resolution Structure of the Human Insulin Receptor Ectodomain: Multi-Modal Inclusion of the Insert Domain

Insulin receptor (IR) signaling is critical to controlling nutrient uptake and metabolism. However, only a low-resolution (3.8 Å) structure currently exists for the IR ectodomain, with some segments ill-defined or unmodeled due to disorder. Here, we revise this structure using new diffraction data to 3.3 Å resolution that allow improved modeling of the N-linked glycans, the first and third fibronectin type III domains, and the insert domain. A novel haptic interactive molecular dynamics strategy was used to aid fitting to low-resolution electron density maps. The resulting model provides a foundation for investigation of structural transitions in IR upon ligand binding.

Patent Highlight

A snapshot of noteworthy recent developments in the patent literature of relevance to pharmaceutical and medical research and development.

HDX-MS guided drug discovery: small molecules and biopharmaceuticals

Hydrogen/deuterium exchange coupled with mass spectrometry (HDX-MS or DXMS) has emerged as an important tool for the development of small molecule therapeutics and biopharmaceuticals. Central to these advances have been improvements to automated HDX-MS platforms and software that allow for the rapid acquisition and processing of experimental data. Correlating the HDX-MS profile of large numbers of ligands with their functional outputs has enabled the development of structure activity relationships (SAR) and delineation of ligand classes based on functional selectivity. HDX-MS has also been applied to address many of the unique challenges posed by the continued emergence of biopharmaceuticals. Here we review the latest applications of HDX-MS to drug discovery, recent advances in technology and software, and provide perspective on future outlook.