Novel approaches to drug discovery for the treatment of type 2 diabetes

Diabetes: a review of its pathophysiology, and advanced methods of mitigation

Diabetes mellitus (DM) is a long-lasting metabolic non-communicable disease often characterized by an increase in the level of glucose in the blood or hyperglycemia. Approximately, 415 million people between the ages of 20 and 79 years had DM in 2015 and this figure will rise by 200 million by 2040. In a study conducted by CARRS, it's been found that in Delhi the prevalence of diabetes is around 27% and for prediabetic cases, it is more than 46%. The disease DM can be both short-term and long-term and is often associated with one or more diseases like cardiovascular disease, liver disorder, or kidney malfunction. Early identification of diabetes may help avoid catastrophic repercussions because untreated DM can result in serious complications. Diabetes' primary symptoms are persistently high blood glucose levels, frequent urination, increased thirst, and increased hunger. Therefore, DM is classified into four major categories, namely, Type 1, Type 2, Gestational diabetes, and secondary diabetes. There are various oral and injectable formulations available in the market like insulin, biguanides, sulphonylureas, etc. for the treatment of DM. Recent attention can be given to the various nano approaches undertaken for the treatment, diagnosis, and management of diabetes mellitus. Various nanoparticles like Gold Nanoparticles, carbon nanomaterials, and metallic nanoparticles are some of the approaches mentioned in this review. Besides nanotechnology, artificial intelligence (AI) has also found its application in diabetes care. AI can be used for screening the disease, helping in decision-making, predictive population-level risk stratification, and patient self-management tools. Early detection and diagnosis of diabetes also help the patient avoid expensive treatments later in their life with the help of IoT (internet of medical things) and machine learning models. These tools will help healthcare physicians to predict the disease early. Therefore, the Nano drug delivery system along with AI tools holds a very bright future in diabetes care.

Multitargeted inhibition of key enzymes associated with diabetes and Alzheimer's disease by 1,3,4-oxadiazole derivatives: Synthesis, in vitro screening, and computational studies

A library of 22 derivatives of 1,3,4-oxadiazole-2-thiol was synthesized, structurally characterized, and assessed for its potential to inhibit α-amylase, α-glucosidase, acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and antioxidant activities. Most of the tested compounds demonstrated good to moderate inhibition potential; however, their activity was lower than that of the standard acarbose. Significantly, compound 3f exhibited the highest inhibition potential against α-glucosidase and α-amylase enzymes, with IC50 values of 18.52 ± 0.09 and 20.25 ± 1.05 µM, respectively, in comparison to the standard acarbose (12.29 ± 0.26; 15.98 ± 0.14 µM). Compounds also demonstrated varying degrees of inhibitory potential against AChE (IC50  = 9.25 ± 0.19 to 36.15 ± 0.12 µM) and BChE (IC50  = 10.06 ± 0.43 to 35.13 ± 0.12 µM) enzymes compared to the standard donepezil (IC50  = 2.01 ± 0.12; 3.12 ± 0.06 µM), as well as DPPH (IC50  = 20.98 ± 0.06 to 52.83 ± 0.12 µM) and ABTS radical scavenging activities (IC50  = 22.29 ± 0.18 to 47.98 ± 0.03 µM) in comparison to the standard ascorbic acid (IC50  = 18.12 ± 0.15; 19.19 ± 0.72). The kinetic investigations have demonstrated that the compounds exhibit competitive-type inhibition for α-amylase, noncompetitive-type inhibition for α-glucosidase and AChE, and mixed-type inhibition for BChE. Additionally, a molecular docking study was performed on all synthetic oxadiazoles to explore the interaction details of these compounds with the active sites of the enzymes.

Imidazopyridine-Based Thiazole Derivatives as Potential Antidiabetic Agents: Synthesis, In Vitro Bioactivity, and In Silico Molecular Modeling Approach

A new series of thiazole derivatives (4a-p) incorporating imidazopyridine moiety was synthesized and assessed for their in vitro potential α-glucosidase potency using acarbose as a reference drug. The obtained results suggested that compounds 4a (docking score = -13.45), 4g (docking score = -12.87), 4o (docking score = -12.15), and 4p (docking score = -11.25) remarkably showed superior activity against the targeted α-glucosidase enzyme, with IC50 values of 5.57 ± 3.45, 8.85 ± 2.18, 7.16 ± 1.40, and 10.48 ± 2.20, respectively. Upon further investigation of the binding mode of the interactions by the most active scaffolds with the α-glucosidase active sites, the docking analysis was accomplished in order to explore the active cavity of the α-glucosidase enzyme. The interpretation of the results showed clearly that scaffolds 4a and 4o emerged as the most potent α-glucosidase inhibitors, with promising excellent binding interactions with the active site of the α-glucosidase enzyme. Furthermore, utilizing a variety of spectroscopic methods, such as 1H-NMR, 13C-NMR, and HREI-MS, the precise structures of the synthesized scaffolds were determined.

Transient B-cell depletion and regulatory T-cells mediation in combination with adenovirus mediated IGF-1 prevents and reverses autoimmune diabetes in NOD mice

Type 1 diabetes (T1D) is one of the T cells mediated autoimmune diseases, although B cells also play an important role in the development. Both T cell and B cell targeted immunotherapies exhibited efficacies in preventing and reversing the T1D. Current study was performed to investigate the protective effects of anti-CD20/CD3 bi-specific antibody (bsAb) in combination with adenovirus mediated mouse insulin-like growth factor 1 (Adv-mIGF-1) gene on T1D in non-obese diabetes (NOD) mice. To simultaneously restore the proportion of Th cells and block the interaction of B cells as well as mediate T cell populations, the NOD model mice were randomly assigned to four groups received the saline, anti-CD20/CD3 bsAb and Adv-mIGF-1 gene alone or combination, respectively. After 16-consecutive weeks intervention, the ELISA, RT-PCR, western blot and histopathological analysis were performed to assess the pancreatic tissues and serum samples to evaluate the treatment effects. Chronic treatment of combination therapy improved T1D morbidity by improving the compartment and function of the CD4⁺Foxp3⁺ Tregs, reversing the secretion of insulin, controlling the blood glucose levels (BGLs) and alleviating insulitis as well as cell apoptosis in the NOD model mice. Moreover, current combination therapy also accelerated the proliferation and differentiation of pancreatic β cells via suppressing the apoptosis-related factors, including caspase-3, caspase-8 and Fas, and activating the Bcl-2-related anti-apoptotic pathway. Furthermore, the cytokeratin-19 (CK-19) and pancreatic duodenal homoplasmic box-1 (PDX-1), as two important stem cell markers of pancreas were both significantly improved by treatment of combination therapy. On conclusions, chronic treatment of anti-CD20/CD3 bsAb in combination with Adv-mIGF-1 gene exerts synergistic protection on T1D in the NOD mice.

Current and future approaches for in vitro hit discovery in diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a serious public health problem. In this review, we discuss current and promising future drugs, targets, in vitro assays and emerging omics technologies in T2DM. Importantly, we open the perspective to image-based high-content screening (HCS), with the focus of combining it with metabolomics or lipidomics. HCS has become a strong technology in phenotypic screens because it allows comprehensive screening for the cell-modulatory activity of small molecules. Metabolomics and lipidomics screen for perturbations at the molecular level. The combination of these data-intensive comprehensive technologies is enabled by the rapid development of artificial intelligence. It promises a deep cellular and molecular phenotyping directly linked to chemical information about the applied drug candidates or complex mixtures.

Design, synthesis, and biological evaluation of novel dual FFA1 and PPARδ agonists possessing phenoxyacetic acid scaffold

The free fatty acid receptor 1 (FFA1/GPR40) and peroxisome proliferator-activated receptor δ (PPARδ) have been widely considered as promising targets for type 2 diabetes mellitus (T2DM) due to their respective roles in promoting insulin secretion and improving insulin sensitivity. Hence, the dual FFA1/PPARδ agonists may exert synergistic effects by simultaneously activating FFA1 and PPARδ. The present study performed systematic exploration around previously reported FFA1 agonist 2-(2-fluoro-4-((2'-methyl-4'-(3-(methylsulfonyl)propoxy)-[1,1'-biphenyl]-3-yl)methoxy)phenoxy)acetic acid (lead compound), leading to the identification of a novel dual FFA1/PPARδ agonist 2-(2-fluoro-4-((3-(6-methoxynaphthalen-2-yl)benzyl)oxy)phenoxy)acetic acid (the optimal compound), which displayed high selectivity over PPARα and PPARγ. In addition, the docking study provided us with detailed binding modes of the optimal compound in FFA1 and PPARδ. Furthermore, the optimal compound exhibited greater glucose-lowering effects than lead compound, which might attribute to its synergistic effects by simultaneously modulating insulin secretion and resistance. Moreover, the optimal compound has an acceptable safety profile in the acute toxicity study at a high dose of 500 mg/kg Therefore, our results provided a novel dual FFA1/PPARδ agonist with excellent glucose-lowering effects in vivo.

α-glucosidase immobilization on magnetic core-shell metal-organic frameworks for inhibitor screening from traditional Chinese medicines

In this work, a simple and rapid screening strategy was developed combining capillary electrophoresis analysis with enzymatic assay based on immobilized α-glucosidase. For α-glucosidase immobilization, magnetic core-shell metal-organic frameworks composite (Fe₃O₄@CS@ZIF-8) was fabricated by a step-by-step assembly method, and α-glucosidase was in situ encapsulated in crystal lattice of ZIF-8. The composite was characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and vibrating sample magnetometer. After immobilization, α-glucosidase exhibited enhanced tolerance to temperature and pH, and its reusability was greatly improved with 74 % of initial enzyme activity after being recycled 10 times. The Michaelis-Menten constant of immobilized enzyme was calculated to be 0.47 mM and its inhibition constant and IC₅₀ for acarbose were 0.57 μM and 0.18 μM, respectively. The immobilized enzyme was subsequently applied to inhibitor screening from 14 TCMs, and Rhei Radix et Rhizoma was screened out. Among the commercially available 10 components presented in Rhei Radix et Rhizoma, gallic acid, (+)-catechin and epicatechin exhibited the strongest inhibitory effect on α-glucosidase. Their binding sites and modes with α-glucosidase were simulated via molecular docking to further verify the inhibition screening assay results. The positive results indicated that the Fe₃O₄@CS@ZIF-8-based screening strategy may provide a new avenue for discovering enzyme inhibitors from TCMs.

Fighting Diabetes Mellitus: Pharmacological and Non-pharmacological Approaches

BACKGROUND

The increasing worldwide prevalence of diabetes mellitus confers heavy public health issues and points to a large medical need for effective and novel anti-diabetic approaches with negligible adverse effects. Developing effective and novel anti-diabetic approaches to curb diabetes is one of the most foremost scientific challenges.

OBJECTIVES

This article aims to provide an overview of current pharmacological and non-pharmacological approaches available for the management of diabetes mellitus.

METHODS

Research articles that focused on pharmacological and non-pharmacological interventions for diabetes were collected from various search engines such as Science Direct and Scopus, using keywords like diabetes, glucagon-like peptide-1, glucose homeostasis, etc. Results: We review in detail several key pathways and pharmacological targets (e.g., the G protein-coupled receptors- cyclic adenosine monophosphate, 5'-adenosine monophosphate-activated protein kinase, sodium-glucose cotransporters 2, and peroxisome proliferator activated-receptor gamma signaling pathways) that are vital in the regulation of glucose homeostasis. The currently approved diabetes medications, the pharmacological potentials of naturally occurring compounds as promising interventions for diabetes, and the non-pharmacological methods designed to mitigate diabetes are summarized and discussed.

CONCLUSION

Pharmacological-based approaches such as insulin, metformin, sodium-glucose cotransporters 2 inhibitor, sulfonylureas, glucagon-like peptide-1 receptor agonists, and dipeptidyl peptidase IV inhibitors represent the most important strategies in diabetes management. These approved diabetes medications work via targeting the central signaling pathways related to the etiology of diabetes. Non-pharmacological approaches, including dietary modification, increased physical activity, and microbiota-based therapy are the other cornerstones for diabetes treatment. Pharmacological-based approaches may be incorporated when lifestyle modification alone is insufficient to achieve positive outcomes.

Modeling and simulation in medical sciences: an overview of specific applications based on research experience in EMRI (Endocrinology and Metabolism Research Institute of Tehran University of Medical Sciences)

The concomitant use of various types of models (in silico, in vitro, and in vivo) has been exemplified here within the context of biomedical researches performed in the Endocrinology and Metabolism Research Institute (EMRI) of Tehran University of Medical Sciences. Two main research aeras have been discussed: the search for new small molecules as therapeutics for diabetes and related metabolic conditions, and diseases related to protein aggregation. Due to their multidisciplinary nature, the majority of these studies have needed the collaboration of different specialties. In both cases, a brief overview of the subject is provided through literature examples, and sequential use of these methods is described.

Rapid selection of a novel GLP-1/GIP dual receptor agonist with prolonged glycemic control and weight loss in rodent animals

BACKGROUND

Glucagon-like peptide-1 receptor (GLP-1R) and glucose-dependent insulinotropic polypeptide receptor (GIPR) co-agonists have emerged as treatment options for reversing diabetes and obesity. Here, we screened the high potency receptor-biased GLP-1R agonists via a newly designed high-throughput GLP-1R extracellular domain (ECD)-based system and demonstrated its in vitro and in vivo therapeutic characters.

METHODS

Twelve 9-mer peptides (named XEL1-XEL12) which were screened from a large phage-displayed peptide library were fused to the N-terminus of GIP (3-30) to generate another twelve fusion peptides, termed XEL13-24. Using the six lysine-altered XEL17 as leading sequences, eighteen fatty chain modified fusion peptides were further assessed via in vitro GLP-1R/GIPR-based cell assay. Moreover, the acute and long-acting in vivo effects of selected candidate on diabetic db/db mice and diet-induced obesity (DIO) rats were both carefully evaluated.

RESULTS

XEL17 exhibited balanced activation potency on GLP-1R/GIPR in stable cell lines, and further assessment was performed to evaluate the XEL32, a fatty chain modified XEL17 derivative. Preclinical pharmacodynamic results in diabetic db/db mice demonstrated that XEL32 held outstanding insulinotropic and glucose-lowering activities. In addition, protracted antidiabetic effects of XEL32 were also proved by the hypoglycemic test and multiple oral glucose tolerance test. Furthermore, chronic treatment of XEL32 in DIO rats exhibited outstanding beneficial effects on body weight control, fat loss, food intake control, hemoglobin A1C (HbA1C) reduction as well as the glucose tolerance.

CONCLUSIONS

XEL32, as a novel GLP-1/GIP dual receptor agonist, may supply efficient glycemic control and weight loss.

HWL-088, a new potent free fatty acid receptor 1 (FFAR1) agonist, improves glucolipid metabolism and acts additively with metformin in ob/ob diabetic mice

BACKGROUND AND PURPOSE

The free fatty acid receptor 1 (FFAR1) plays an important role in glucose-stimulated insulin secretion making it an attractive anti-diabetic target. This study characterizes the pharmacological profile of HWL-088 (2-(2-fluoro-4-((2'-methyl-[1,1'- biphenyl]-3-yl)methoxy)phenoxy)acetic acid), a novel highly potent FFAR1 agonist in vitro and in vivo. Moreover, we investigated the long-term effects of HWL-088 alone and in combination with metformin in diabetic mice.

EXPERIMENTAL APPROACH

In vitro effects of HWL-088 on FFAR1 and PPARα/γ/δ were studied in cell-based assays. Glucose-dependent insulinotropic effects were evaluated in MIN6 cell line and in rats. Long-term effects on glucose and lipid metabolism were investigated in ob/ob mice.

KEY RESULTS

HWL-088 is a highly potent FFAR1 agonist (EC50 = 18.9 nM) with moderate PPARδ activity (EC50 = 570.9 nM) and promotes glucose-dependent insulin secretion in vitro and in vivo. Long-term administration of HWL-088 exhibited better glucose control and plasma lipid profiles than those of another FFAR1 agonist, TAK-875, and synergistic improvements were observed when combined with metformin. Moreover, HWL-088 and combination therapy improved β-cell function by up-regulation of pancreas duodenum homeobox-1, reduced fat accumulation in adipose tissue and alleviated fatty liver in ob/ob mice. The effect of HWL-088 involves a reduction in hepatic lipogenesis and oxidative stress, increased lipoprotein lipolysis, glucose uptake, mitochondrial function and fatty acid β-oxidation.

CONCLUSION AND IMPLICATIONS

These data indicate that long-term treatment with HWL-088, a highly potent FFAR1 agonist, improves glucose and lipid metabolism and may be useful for the treatment of diabetes mellitus by mono-therapy or combination with metformin.

Novel fatty chain-modified GLP-1R G-protein biased agonist exerts prolonged anti-diabetic effects through targeting receptor binding sites

Here, we design and evaluate novel long-lasting GLP-1R G-protein-biased agonists with promising pharmacological virtues. Firstly, six GLP-1R G-protein-biased peptides (named PX01-PX06), screened by using a previous reported high-throughput autocrine-based method, were fused to the N-terminus of GLP-1(9-37) to generate six fusion peptides (PX07-PX012). In vitro surface plasmon resonance (SPR) measurements showed that PX09 exerts the highest binding affinity for both human and mouse GLP-1R extracellular domains (ECD). We further used the PX09 as a starting point to conduct site-specific modifications yielding twelve lysine-modified conjugates, termed PX13-PX24. Of these conjugates, PX17 retained relatively better in vitro GLP-1R activation potency and plasma stability compared with other ones. Preclinical studies in db/db mice demonstrated that acute treatment of PX17 exerts enhanced hypoglycemic and insulinotropic activities in a dosage dependent model within the range of 0.1-0.9 mg kg-1. Similarly, prolonged glucose-lowering abilities were exhibited in modified multiple oral glucose tolerance tests (OGTTs) and a hypoglycemic duration test. Apparently prolonged in vivo half-lives of ∼96 and ∼141 h were observed after a single subcutaneous administration of PX17 at 0.1 and 0.3 mg kg-1, respectively, in healthy cynomolgus monkeys. In addition, twice-weekly treatment of PX17 in db/db mice for 8 weeks obviously improved the hemoglobin A1C (HbA1C), and was more effective at improving the insulin resistance, glucose tolerance as well as function of pancreatic beta cells compared with Semaglutide. Furthermore, subcutaneously dosed PX17 in diet induced obese (DIO) mice achieved long-term beneficial effects on food intake and body weight control, HbA1C and inflammation-related factor level lowering. The above results indicate that PX17, as a novel GLP-1R G-protein-biased agonist, may be a promising candidate for antidiabetic therapies.

Synthesis, Structural Studies, and α-Glucosidase Inhibitory, Antidiabetic, and Antioxidant Activities of 2,3-Dihydroquinazolin-4(1H)-ones Derived from Pyrazol-4-carbaldehyde and Anilines

A series of new quinazoline derivatives were designed and synthesized via a one-pot condensation reaction between isatoic anhydride and aromatic aldehydes with anilines using aluminum sulfate as a catalyst in refluxing ethanol. Their structures were confirmed by their physical, IR, 1H NMR, 13C NMR, and mass spectroscopy data and evaluated for some biological effects, including the antioxidant and α-glucosidase inhibitory activities as well as some in vivo hematological parameters. The ability of synthesized compounds in the inhibition of α-glucosidase was also investigated through the in silico study. The significant and important changes in some hematological tests were perceived. Notably, compound 4h showed more reducing effects on cholesterol and triglyceride levels. This molecule certainly has the potential to be developed as the antihyperlipemic compound. The tested compounds, in particular, compounds 4j and 4l, were found to be uniquely reducing blood sugar levels. The entire synthesized compounds showed the potent α-glucosidase inhibitory activity compared with acarbose as a standard material. Amongst, the compounds 4h and 4i showed the strongest enzyme inhibitory potentials than the standard drug acarbose. There was a good correlation between in vitro and in silico studies for ligands 4i and 4l. The majority of compounds presented a good radical scavenging activity, though the compound 4j exhibited the strongest activity, even to the standard of ascorbic acid. Further studies are required to determine whether these main compounds could be a potential treatment for diabetes and hyperlipidemia diseases.

The effect of SGLT-2 inhibitors on blood pressure: a pleiotropic action favoring cardio- and nephroprotection

Strict blood pressure (BP) control in patients with diabetes is associated with reductions in cardiovascular and renal risk. SGLT-2 inhibitors act in the proximal tubule to reduce glucose reabsorption. They also have mild natriuretic and diuretic effects, combining properties of proximal tubule diuretics and osmotic diuretics, which are expected to reduce BP. Several lines of evidence suggests that SGLT-2 inhibitors produce mild but meaningful reductions in BP and also decrease the incidence of renal outcomes, cardiovascular events and mortality. Thus, recent guidelines for type 2 diabetes suggest that among oral agents to use together with metformin, SGLT-2 inhibitors should be preferred in patients at increased cardiovascular risk, kidney disease or heart failure. This review summarizes current literature on the effect of SGLT-2 inhibitors on BP, and its potential relationships with cardio- and nephroprotection.

Synthesis and biological evaluation of novel potent FFA1 agonists containing 2,3-dihydrobenzo[b][1,4]dioxine

FFA1 (free fatty acid receptor 1) has emerged as an attractive antidiabetic target due to its role in mediating the enhancement of glucose-stimulated insulin secretion in pancreatic β cells with a low risk of hypoglycemia. Many reported FFA1 agonists possessed somewhat pharmacokinetic and/or safety issues. Herein, we describe the identification of 2,3-dihydrobenzo[b][1,4]dioxine as a novel scaffold for FFA1 agonists. Comprehensive structure-activity relationship study based on this scaffold led to the discovery of (S)-3-(4-(((S)-7-(4-methoxyphenyl)-2,3-dihydrobenzo [b][1,4]dioxin-2-yl)methoxy) phenyl)hex-4-ynoic acid (26k), which displayed a potent FFA1 agonistic activity and good pharmacokinetic profiles. Subsequent in vivo studies demonstrated that compound 26k significantly improved the glucose tolerance in ICR mice. In summary, compound 26k is a promising drug candidate for further investigation.

Design, synthesis, and evaluation of a series of novel phenylpropanoic acid derivatives agonists for the FFA1

Free fatty acid 1 (FFA1/GPR40) has attracted extensive attention as a novel target for the treatment of type 2 diabetes for its role in the enhancement of insulin secretion with glucose dependency. Aiming to develop novel potent FFA1 agonists, a new series of phenylpropionic acid derivatives were designed and synthesized on the basis of the modification of chemical cement of TAK-875, AMG-837, and LY2881835. Among them, most promising compounds 7, 14, and 15 were obtained with EC₅₀ values of 82, 79, and 88 nM, exhibiting a powerful agonistic activity compared to TAK-875 (95.1 nM). During Oral glucose tolerance test in normal mice, compound 7, 14, and 15 had significant glucose-lowering effect at the dose of 50 mg/kg. Furthermore, compound 15 (50 mg/kg) also significantly improved in glucose tolerance in type 2 diabetic mice. Herein, we reported the discovery and optimization of a series of potent FFA1 agonists. The discovery supported further exploration surrounding this scaffold.

Antidiabetic Effects of the Ethanolic Root Extract of Uvaria chamae P. Beauv (Annonaceae) in Alloxan-Induced Diabetic Rats: A Potential Alternative Treatment for Diabetes Mellitus

Diabetes mellitus has been a menace to mankind from time immemorial. However, a natural product such as U. chamae P. Beauv (Annonaceae) offers alternative treatment for diabetes mellitus. The study aimed at evaluating antidiabetic activity of the ethanolic root extract of U. chamae in alloxan-induced diabetic rats. Diabetes was induced in Sprague Dawley rats after overnight fast with 150 mg/kg alloxan intraperitoneally. After 72 h, those with plasma glucose levels >200 mg/dl were classified as diabetic. Five diabetic rats in each group were treated daily for 14 days orally with 100, 250, and 400 mg/kg of the extract, glibenclamide (71 µg/kg) and pioglitazone (429 µg/kg), respectively, while another group was untreated. Control received 0.5 ml of Acacia senegal. Effects of extract on glucose, other biochemical, and hematological parameters were evaluated. α-amylase and α-glucosidase inhibitory activities of extract and its fractions were also evaluated. Percentage inhibition and IC₅₀ values were determined. Diabetic control was achieved on the 7th day of the study with 100, 250, and 400 mg/kg of the extract showing glucose reduction of 72.14%, 78.75%, and 87.71%, respectively. The HDL-cholesterol levels of diabetic rats treated with extracts were significantly increased. Extract and its fractions caused α-amylase and α-glucosidase inhibition. Histologically, pancreas of diabetic rats treated with extract showed regenerated islet cells which were not seen in rats treated with glibenclamide and pioglitazone. This study showed that U. chamae has antidiabetic activity which may be through α-amylase and α-glucosidase inhibition and regeneration of pancreatic beta cells. Also, it may reduce the risk of cardiovascular disease by increasing HDL-cholesterol levels.

ETA as a novel Kv2.1 inhibitor ameliorates β-cell dysfunction and hyperglycaemia

The Kv2.1 channel plays an important role in the regulation against pancreatic β-cell dysfunctions. Therefore, it is regarded as a promising target for drug discovery against type 2 diabetes. In the present study, we found that the small molecule 4-ethoxy-N-{[6-(2-thienyl)-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazin-3-yl]methyl}aniline (ETA), a novel Kv2.1 inhibitor, may be capable of promoting glucose-stimulated insulin secretion and protecting from apoptosis in pancreatic INS-832/13 cells. The assay of ETA on type 2 diabetic mice induced by high-fat diet (HFD)/streptozocin (STZ) confirmed its potency in ameliorating glucose homeostasis. ETA administration reduced fasting blood glucose and glycated haemoglobin levels, improved oral glucose tolerance, and increased serum insulin levels in HFD/STZ mice. Mechanism study demonstrated that ETA protected INS-832/13 cells involving the regulation against protein kinase B and extracellular-regulated protein kinase 1/2 signalling pathways. Our study has confirmed the underlying regulation of Kv2.1 against β-cell function and also addressed the potential of ETA as a lead compound in the treatment of type 2 diabetes mellitus.

A preclinical overview of metformin for the treatment of type 2 diabetes

Type 2 diabetes (T2D) is the most common type of diabetes mellitus and is mainly characterized by insulin resistance, β-cell dysfunction, and elevated hepatic glucose output. Metformin is a first-line antihyperglycemic agent that works mainly by regulating hepatic glucose production and peripheral insulin sensitivity. Metformin has been clinically applied for more than half a century, although the underlying pharmacological mechanisms remain elusive. This current review mainly focused on the development history of metformin and related preclinical studies on structural modification, pharmacological mechanisms for treatment of T2D, toxicology, pharmacokinetics, and pharmaceutics. The pharmacological function of metformin in lowering hyperglycemia suggests that multi-targeting could be an effective strategy for the discovery of new anti-diabetic drugs. A number of discoveries have revealed the pharmacologic mechanisms of metformin; however, precise mechanisms remain unclear. Deeper investigations on the biological features of metformin are expected to provide more rational applications and indications of this evergreen anti-T2D agent, which will in turn help to better understand the complicated pathogenesis of T2D.

Structure-based design of free fatty acid receptor 1 agonists bearing non-biphenyl scaffold

The free fatty acid receptor 1 (FFA1) enhances the glucose-stimulated insulin secretion without the risk of hypoglycemia. However, most of FFA1 agonists have a common biphenyl moiety, leading to a relative deprivation in structure types. Herein, we describe the exploration of non-biphenyl scaffold based on the co-crystal structure of FFA1 to increase additional interactions with the lateral residues, which led to the identification of lead compounds 3 and 9. In induced-fit docking study, compound 3 forms an edge-on interaction with Trp150 by slightly rotating the indole ring of Trp150, and compound 9 has additional hydrogen bond and δ-π interactions with Leu135, which demonstrated the feasibility of our design strategy. Moreover, lead compounds 3 and 9 revealed improved polar surface area compared to GW9508, and have considerable hypoglycemic effects in mice. This structure-based study might inspire us to design more promising FFA1 agonists by increasing additional interactions with the residues outside of binding pocket.

TSPA as a novel ATF6α translocation inducer efficiently ameliorates insulin sensitivity restoration and glucose homeostasis in db/db mice

Activating transcription factor 6α (ATF6α) as a transducer in unfolded protein response (UPR), plays an important role in liver glucose metabolism and insulin resistance. Thus, targeting ATF6α activation has been proposed to be a potential strategy for anti-T2DM drug discovery. Here, we determined that small molecule 2-[5-[1-(4-chlorophenoxy)ethyl]-4-phenyl-4H-1,2,4-triazol-3-yl]sulfanyl-N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)acetamide (TSPA) functioned as an ATF6α translocation inducer effectively promoting ATF6α translocation into nucleus and ameliorating glucose homeostasis on db/db mice. TSPA promoted ATF6α translocation into nucleus without incresing C/EBP-homologous protein (CHOP) expression. TSPA restored the tunicamycin (TM)-stimulated insulin receptor (IR) desensitization through ATF6α activation, inhibited gluconeogenesis and efficiently improved glucose homeostasis on db/db mice. Furthermore, TSPA protected insulin pathway involving p38/X-box binding protein 1s (Xbp1s)/ER chaperones signaling pathway. Our current study has determined that ATF6α was a promising therapeutic target and also highlighted the potential of TSPA in the treatment of type 2 diabetes mellitus (T2DM).

Structure-based optimization of free fatty acid receptor 1 agonists bearing thiazole scaffold

The free fatty acid receptor 1 (FFA1) plays an important role in amplifying insulin secretion in a glucose dependent manner. We have previously reported a series of FFA1 agonists with thiazole scaffold exemplified by compound 1, and identified a small hydrophobic subpocket partially occupied by the methyl group of compound 1. Herein, we describe further structure optimization to better fit the small hydrophobic subpocket by replacing the small methyl group with other hydrophobic substituents. All of these efforts resulted in the identification of compound 6, a potent FFA1 agonist (EC₅₀ = 39.7 nM) with desired ligand efficiency (0.24) and ligand lipophilicity efficiency (4.7). Moreover, lead compound 6 exhibited a greater potential for decreasing the hyperglycemia levels than compound 1 during an oral glucose tolerance test. In summary, compound 6 is a promising FFA1 agonist for further investigation, and the structure-based study promoted our understanding for the binding pocket of FFA1.

DMT efficiently inhibits hepatic gluconeogenesis by regulating the Gαq signaling pathway

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease with complicated pathogenesis and targeting gluconeogenesis inhibition is a promising strategy for anti-diabetic drug discovery. G protein-coupled receptors (GPCRs) are classified as distinct families by heterotrimeric G proteins, primarily including Gαs, Gαi and Gαq. Gαs-coupled GPCRs function potently in the regulation of hepatic gluconeogenesis by activating cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) pathway and Gαi-coupled GPCRs exhibit inhibitory effect on adenylyl cyclase and reduce intracellular cAMP level. However, little is known about the regulation of Gαq-coupled GPCRs in hepatic gluconeogenesis. Here, small-molecule 2-(2,4-dimethoxy-3-methylphenyl)-7-(thiophen-2-yl)-9-(trifluoromethyl)-2,3-dihydropyrido[3',2':4,5]thieno[3,2-d]pyrimidin-4(1H)-one (DMT) was determined to suppress hepatic glucose production and reduce mRNA levels of gluconeogenic genes. Treatment of DMT in db/db mice decreased fasting blood glucose and hemoglobin A1C (HbA1c) levels, while improved glucose tolerance and pyruvate tolerance. Mechanism study demonstrated that DMT-inhibited gluconeogenesis by regulating the Gαq/phospholipase C (PLC)/inositol-1,4,5-triphosphate receptor (IP3R)-mediated calcium (Ca²⁺)/calmodulin (CaM)/phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/protein kinase B (AKT)/forkhead box protein O1 (FOXO1) signaling pathway. To our knowledge, DMT might be the first reported small molecule able to suppress hepatic gluconeogenesis by regulating Gαq signaling, and our current work has also highlighted the potential of DMT in the treatment of T2DM.

Chromone as a Privileged Scaffold in Drug Discovery: Recent Advances

The use of privileged structures in drug discovery has proven to be an effective strategy, allowing the generation of innovative hits/leads and successful optimization processes. Chromone is recognized as a privileged structure and a useful template for the design of novel compounds with potential pharmacological interest, particularly in the field of neurodegenerative, inflammatory, and infectious diseases as well as diabetes and cancer. This perspective provides the reader with an update of an earlier article entitled "Chromone: A Valid Scaffold in Medicinal Chemistry" ( Chem. Rev. 2014 , 114 , 4960 - 4992 ) and is mainly focused on chromones of biological interest, including those isolated from natural sources. Moreover, as drug repurposing is becoming an attractive drug discovery approach, recent repurposing studies of chromone-based drugs are also reported.

Free fatty acid receptor agonists for the treatment of type 2 diabetes: drugs in preclinical to phase II clinical development

INTRODUCTION

The alarming prevalence of type 2 diabetes mellitus (T2DM) stimulated the exploitation of new antidiabetic drugs with extended durability and enhanced safety. In this regard, the free fatty acid receptor 1 (FFA1) and FFA4 have emerged as attractive targets in the last decade. FFA1 has prominent advantages in promoting insulin and incretin secretion while FFA4 shows great potential in incretin secretion, insulin sensitization and anti-inflammatory effects.

AREA COVERED

Herein, the authors focus specifically on FFA1 and FFA4 agonists in clinical trials and preclinical development. LY2922470, P11187 and SHR0534 are currently active in clinical trials while the CNX-011-67, SAR1, DS-1558 and BMS-986118 are in preclinical phase. The information for this review is retrieved from Integrity, Scifinder, Espacenet and clinicaltrials.gov databases.

EXPERT OPINION

Current proof-of-concept in clinical trials suggests that FFA1 agonists have a significant improvement for T2DM without the risk of hypoglycemia. However, there are still several challenging problems including the mechanism of the receptor and the efficacy and safety of the ligands.

SP6616 as a new Kv2.1 channel inhibitor efficiently promotes β-cell survival involving both PKC/Erk1/2 and CaM/PI3K/Akt signaling pathways

Kv2.1 as a voltage-gated potassium (Kv) channel subunit has a pivotal role in the regulation of glucose-stimulated insulin secretion (GSIS) and pancreatic β-cell apoptosis, and is believed to be a promising target for anti-diabetic drug discovery, although the mechanism underlying the Kv2.1-mediated β-cell apoptosis is obscure. Here, the small molecular compound, ethyl 5-(3-ethoxy-4-methoxyphenyl)-2-(4-hydroxy-3-methoxybenzylidene)-7-methyl-3-oxo-2,3-dihydro-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate (SP6616) was discovered to be a new Kv2.1 inhibitor. It was effective in both promoting GSIS and protecting β cells from apoptosis. Evaluation of SP6616 on either high-fat diet combined with streptozocin-induced type 2 diabetic mice or db/db mice further verified its efficacy in the amelioration of β-cell dysfunction and glucose homeostasis. SP6616 treatment efficiently increased serum insulin level, restored β-cell mass, decreased fasting blood glucose and glycated hemoglobin levels, and improved oral glucose tolerance. Mechanism study indicated that the promotion of SP6616 on β-cell survival was tightly linked to its regulation against both protein kinases C (PKC)/extracellular-regulated protein kinases 1/2 (Erk1/2) and calmodulin(CaM)/phosphatidylinositol 3-kinase(PI3K)/serine/threonine-specific protein kinase (Akt) signaling pathways. To our knowledge, this may be the first report on the underlying pathway responsible for the Kv2.1-mediated β-cell protection. In addition, our study has also highlighted the potential of SP6616 in the treatment of type 2 diabetes.

Discovery of a novel oxime ether scaffold as potent and orally bioavailable free fatty acid receptor 1 agonists

The free fatty acid receptor 1 (FFA1) plays a key role in amplifying glucose-stimulated insulin secretion in pancreatic β-cells.

Alternative Medicine in Diabetes - Role of Angiogenesis, Oxidative Stress, and Chronic Inflammation

Diabetes is a chronic metabolic disorder that is characterized by hyperglycemia due to lack of or resistance to insulin. Patients with diabetes are frequently afflicted with ischemic vascular disease and impaired wound healing. Type 2 diabetes is known to accelerate atherosclerotic processes, endothelial cell dysfunction, glycosylation of extracellular matrix proteins, and vascular denervation. Herbal medicines and naturally occurring substances may positively affect diabetes management, and could thus be utilized as cost-effective means of supporting treatment in developing countries. Natural treatments have been used in these countries for a long time to treat diabetes. The present review analyses the features of aberrant angiogenesis, abnormalities in growth factors, oxidative stress, and metabolic derangements relevant to diabetes, and how herbal substances and their active chemical constituents may counteract these events. Evidence for possible biochemical effectiveness and limitations of herbal medicines are given, as well as details regarding the role of cytokines and nitric oxide.