Baowei Yang

Structure–activity relationships of a snake cathelicidin-related peptide, BF-15

Cathelicidin-BF15 (BF-15) is a 15-mer peptide derived from Cathelicidin-BF (BF-30), which is found in the venom of the snake Bungarus fasciatus and exhibits broad antimicrobial activity. Since BF-15 retains most part of the antimicrobial activity of BF-30 but has significantly reduced haemolytic activity and a much shorter sequence length (and less cost), it is a particularly attractive template around which to design novel antimicrobial peptides. However, the structure-activity relationship of it is still unknown. We designed and synthesized a series of C-terminal amidated analogs of BF-15 based on its amphipathic α-helix structure. And we characterized their antimicrobial potency and haemolytic activity. We identified the amidated BF-15 (analog B1) with potent antimicrobial activity against several antibiotic-resistant bacteria (MICs between 1 and 64 μg/mL, 2-16-folds higher than BF-30) and much lower haemolytic activity. The subsequent circular dichroism study results showed a typical α-helix pattern of analog B1 and the content of the α-helix structure of it increased significantly comparing with BF-30, which indicates the peptide sequence of BF-15 may provide a major contribution to the α-helix content of the whole BF-30 sequence. The peptide induced chaotic membrane morphology and cell debris as determined by electron microscopy. This suggests that the antimicrobial activity of B1 is based on cytoplasmic membrane permeability. Taken together, our results suggested that peptide B1 should be considered as an excellent candidate for developing therapeutic drugs.

Synthesis and biological evaluation of phenoxyacetic acid derivatives as novel free fatty acid receptor 1 agonists

Free fatty acid receptor 1 (FFA1) is a new potential drug target for the treatment of type 2 diabetes because of its role in amplifying glucose-stimulated insulin secretion in pancreatic β-cell. In the present studies, we identified phenoxyacetic acid derivative (18b) as a potent FFA1 agonist (EC50=62.3 nM) based on the structure of phenylpropanoic acid derivative 4p. Moreover, compound 18b could significantly improve oral glucose tolerance in ICR mice and dose-dependently reduced glucose levels in type 2 diabetic C57BL/6 mice without observation of hypoglycemic side effect. Additionally, compound 18b exhibited acceptable PK profiles. In summary, compound 18b with ideal PK profiles exhibited good activity in vitro and in vivo, and might be a promising drug candidate for the treatment of diabetes mellitus.

Evaluation of hypoglycemic and antioxidative effects of synthesized peptide MC62.

Diabetes mellitus has been considered as a major health problem in the world today. This study aimed to investigate the hypoglycemic and antioxidative effects of peptide MC62 which was synthesized by solid‐phase peptide synthesis method against diabetes induced by streptozotocin. MC62 was administered daily and injected intraperitoneally to the diabetic mice at a dose of 1 μmol/kg body weight for 20 days. The levels of fasting blood glucose and HbA1C, pancreatic islet damage, and associated changes in antioxidative activities were evaluated in streptozotocin‐induced diabetic mice used the exenatide as positive control. After the administration of MC62 together with exenatide for 20 days, the elevated fasting blood glucose and HbA1C levels were reduced, and antioxidative activities were restored. It was confirmed with the histological finding that MC62 prevented the islet from damage in diabetic mice. This indicated that MC62 can prevent mice from hyperglycemia which may be associated with oxidative stress. It also suggested that MC62 could be used as a safe alternative hypoglycemic candidate for treatment of diabetes.

Design, synthesis and biological evaluation of novel peptides with anti-cancer and drug resistance-reversing activities.

Chemotherapy is an important approach used to treat cancer, but severe side effects and emerging drug resistance restrict its clinical application. In this present study, we found that peptide B1 showed specific cytotoxicity to tumor cells. Moreover, a helix-wheel plot predicted that the Ser14 in this peptide is located at the interface of the hydrophobic and hydrophilic faces of B1. Subsequently, we wondered whether replacing Ser14 would alter the activity of B1, and so a series of B1 analogs were synthesized where the Ser14 was replaced by amino acids with distinct physicochemical properties. Amongst them, peptides where Ser14 was substituted by a nonpolar and basic amino acid had improved anti-cancer activity. Further investigations revealed that B1 and its analogs were capable of penetrating into cytoplasm and triggering cytochrome C release from mitochondria, which ultimately resulted in apoptosis. Meanwhile, B1 and its analogs inhibited the migration of cancer cells. The peptides also acted against drug-resistant cells and had drug resistance-reversing effects. In conclusion, these peptides might be promising candidates for oncotherapy.

A specific pharmacophore model of sodium-dependent glucose co-transporter 2 (SGLT2) inhibitors

Sodium-dependent glucose co-transporter 2 (SGLT2) plays a pivotal role in maintaining glucose equilibrium in the human body, emerging as one of the most promising targets for the treatment of diabetes mellitus type 2. Pharmacophore models of SGLT2 inhibitors have been generated with a training set of 25 SGLT2 inhibitors using Discovery Studio V2.1. The best hypothesis (Hypo1SGLT2) contains one hydrogen bond donor, five excluded volumes, one ring aromatic and three hydrophobic features, and has a correlation coefficient of 0.955, cost difference of 68.76, RMSD of 0.85. This model was validated by test set, Fischer randomization test and decoy set methods. The specificity of Hypo1SGLT2 was evaluated. The pharmacophore features of Hypo1SGLT2 were different from the best pharmacophore model (Hypo1SGLT1) of SGLT1 inhibitors we developed. Moreover, Hypo1SGLT2 could effectively distinguish selective inhibitors of SGLT2 from those of SGLT1. These results indicate that a highly predictive and specific pharmacophore model of SGLT2 inhibitors has been successfully obtained. Then Hypo1SGLT2 was used as a 3D query to screen databases including NCI and Maybridge for identifying new inhibitors of SGLT2. The hit compounds were subsequently subjected to filtering by Lipinski’s rule of five. And several compounds selected from the top ranked hits have been suggested for further experimental assay studies.

Stability and Bioactivity Studies on Dipeptidyl Peptidase IV Resistant Glucogan-like Peptide-1 Analogues

Glucagon-like peptide-1 (GLP-1) was once considered as an ideal anti-diabetic candidate for its important role in maintaining glucose homeostasis through the regulation of islet hormone secretion, as well as hepatic and gastric function. However, the major therapeutic obstacle for using native GLP-1 as a therapeutic agent is its very short half-life primarily due to their degradation by the enzyme dipeptidyl peptidase IV (DPP-IV). In this study, GLP-1 analogues with modifications in amino acid site 8, 22 and 23 were synthesized using solid phase peptide synthesis. Resistance of these analogues to DPP-IV cleavage was investigated in vitro by incubation of the peptides with DPP-IV or human plasma. Glucoregulating efficacy of the analogues was evaluated in normal Kunming mice using intraperitoneal glucose tolerance model. Glucose lowering effect of combination therapy (analogue plus Vildagliptin) has also been studied. In vitro studies showed that the modified analogues were much more stable than native GLP-1 (nearly 100% of the peptide keep intact after 4 h incubation). In vivo biological activity evaluation revealed that His8-EEE (the most potent GLP-1 analogues in this study) exhibited significantly improved glycemic control potency (approximately 4.1-fold over saline and 2.5-fold over GLP-1) and longer time of active duration (at least 5 h). Combination therapy also showed the trend of its superiority over mono-therapy. Modified analogues showed increased potency and biological half-time compared with the native GLP-1, which may help to understand the structure-activity relationship of GLP-1 analogues.

3D QSAR Pharmacophore Modeling for c-Met Kinase Inhibitors

The receptor tyrosine kinase c-Met has multiple roles during cancer development and is currently considered as a promising target for cancer therapies. Pharmacophore models of c-Met kinase inhibitors have been developed based on 22 diverse compounds by using HypoGen algorithm implemented in Discovery studio program package. The best quantitative pharmacophore model, Hypo 1, which had the highest correlation coefficient (0.9623), consists of two hydrogen bond acceptors, one hydrophobic feature and two excluded volumes. Then best model was validated by test set prediction, Fischer randomization and decoy set. Besides, the features of Hypo1 were verified to correctly reflect the interactions between kinase active site and its ligands by comparison and superimposition of Hypo 1 in active site of c-Met kinase. The results shows that Hypo 1 has strong capability to identify c-Met kinase inhibitors and to predict the activities of structurally diverse molecules. Therefore, our pharmacophore models were considered as valuable tools for the discovery and development of specific c-Met kinase inhibitors.

C-Aryl Glucosides with Substituents at the Distal Aryl Ring as Sodium-Dependent Glucose Cotransporter Inhibitors for the Treatment of Diabetes Mellitus.

A series of novel C‐aryl glucosides with various substituents at the distal aryl ring have been synthesized and evaluated for hypoglycemic effect in normal and diabetic mice and in type 2 diabetic rats. The results indicated that introduction of electron‐donating group at the distal aryl ring could improve glucose tolerance in normal mice, whereas introduction of electron‐withdrawing group at this position could deteriorate. The urinary glucose excretion was significantly increased after glucose (3 g/kg) administration in normal mice with the treatment of 13c. Moreover, compound 13c could reduce fed blood glucose levels in a dose‐dependent manner in type 2 diabetic rats, showed a remarkable antihyperglycemic effect with 2 weeks of treatment in diabetic mice, and might be a promising drug candidate for the treatment of diabetes mellitus.

Design, Synthesis, and Biological Evaluation of Novel Peptide Gly3‐MC62 Analogues as Potential Antidiabetic Agents

Two series of conformationally constrained analogues from Gly3‐MC62 were designed by scanning the residues Lys1, Thr2, Met4, Lys5, Met7, and Ala8 with an i‐(i + 2) lactam bridge consisting of a Glutamic acid–xaa–lysine (Glu–Xaa–Lys) scaffold and a diproline fragment. They were synthesized and evaluated for their antihyperglycemic effects. Through screening in normal and mice with diabetes mellitus, peptides II‐5, III‐3, III‐4, and III‐5 showed significant improvement in antihyperglycemic and antioxidative activities compared with Gly3‐MC62, especially the compound III‐4. The primary mechanism of the compounds (II‐5, III‐3, III‐4, and III‐5) underlying this effect is the islet β‐cells against oxidative damage induced by STZ, and III‐4‐treated mice showed considerable improvement in the preservation of beta cells in the pancreatic islets of DM mice. These data suggested that III‐4 could be candidate for the future treatment of diabetes mellitus.