Neo-clerodane Diterpenoids with Hypoglycemic Effects in Vivo from the Aerial Parts of Salvia hispanica L.

A new neo-clerodane diterpenoid, salvihispin H (1), and six known ones (2-7) were identified from the aerial parts of Salvia hispanica L. The structure and absolute configuration of 1 were elucidated by extensive analysis of spectroscopic (1 H, 13 C, and 2D NMR, and HR-ESI-MS) and single-crystal X-ray diffraction data. The anti-diabetic effects of salvihispin H (1) and salvifaricin (2) were evaluated in diabetic db/db mice. The data showed that 1 and 2 could significantly reduce fasting blood glucose level and improve insulin resistance, and compound 1 exerted glucose-lowering effect more quickly than metformin. In addition, 1 and 2 could also reduce serum TG level in db/db mice. These results demonstrated that compounds 1 and 2 could be considered as potent candidates for the therapy of type 2 diabetes mellitus (T2DM).

Development of FABP4/5 inhibitors with potential therapeutic effect on type 2 Diabetes Mellitus.

Fatty acid-binding protein 4 (FABP4) and fatty acid-binding protein 5 (FABP5) are promising therapeutic targets for the treatment of various metabolic diseases. However, the weak potency, low selectivity over FABP3, or poor pharmacokinetic profiles of currently reported dual FABP4/5 inhibitors impeded further research. Here, we described the characterization of a series of dual FABP4/5 inhibitors with improved metabolic stabilities and physicochemical properties based on our previous studies. Among the compounds, D9 and E1 exhibited good inhibitory activities against FABP4/5 and favorable selectivity over FABP3 in vitro. In cell-based assays, D9 and E1 exerted a decrease of FABP4 secretion, a strong anti-lipolytic effect in mature adipocytes, and suppression of MCP-1 expression in THP-1 macrophages. Moreover, D9 and E1 possessed good metabolic stabilities in mouse hepatic microsomes and acceptable pharmacokinetics profiles in ICR mice. Further in vivo experiments showed that D9 and E1 could potently decrease serum FABP4 levels and ameliorate glucose metabolism disorders in obese diabetic db/db mice. These results demonstrated that D9 and E1 could serve as lead compounds for the development of novel anti-diabetic drugs.

Combined treatment with FABP4 inhibitor ameliorates rosiglitazone-induced liver steatosis in obese diabetic db/db mice.

Rosiglitazone has been reported to exert dual effects on liver steatosis, and it could exacerbate liver steatosis in obese animal models, which was suggested to be closely related to the elevated hepatic expression of FABP4. This study aimed to investigate whether combined treatment with FABP4 inhibitor I-9 could alleviate rosiglitazone-induced liver steatosis in obese diabetic db/db mice. Male C57BL/KsJ-db/db mice were orally treated with rosiglitazone, rosiglitazone combined with I-9 daily for 8 weeks. The liver steatosis was evaluated by triglyceride content and H&E staining. The expression of hepatic lipogenic genes or proteins in liver tissue or in FFA-treated hepatocytes and PMA-stimulated macrophages were determined by real-time quantitative polymerase chain reaction (RT-qPCR) or western blotting. Results showed that combined treatment with I-9 decreased rosiglitazone-induced increase in serum FABP4 level and expression of lipogenic genes in liver, especially FABP4, and ameliorated liver steatosis in db/db mice. Rosiglitazone-induced intracellular TG accumulation and increased expression of FABP4 in the cultured hepatocytes and macrophages were also suppressed by combined treatment. We concluded that combined treatment with FABP4 inhibitor I-9 could ameliorate rosiglitazone-exacerbated elevated serum FABP4 level and ectopic liver fat accumulation in obese diabetic db/db mice without affecting its anti-diabetic efficacy.

A novel GPR120-selective agonist promotes insulin secretion and improves chronic inflammation.

AIMS: The present study aimed to disclose a potent and selective GPR120 agonist LXT34 and its anti-diabetic effects. MAIN METHODS: Calcium mobilization assay was used to measure the agonistic potency and selectivity of LXT34 in GPR120 or GPR40-overexpression Chinese hamster ovary (CHO) cells. Glucagon-like peptide-1 (GLP-1) release and glucose-stimulated insulin secretion (GSIS) were evaluated in human colonic epithelial cell line NCI-H716 and mouse insulinoma cell line MIN6 by enzyme-linked immunosorbent assay (ELISA), respectively. The anti-inflammatory effect was determined in lipopolysaccharide (LPS)-induced murine macrophage cell line RAW264.7. Oral glucose tolerance test (OGTT) and insulin tolerance test (ITT) were performed to assess the anti-diabetic effects of LXT34 in db/db mice, and chronic inflammation in liver and adipose tissues were investigated using histomorphology, immunoblot and gene expression analysis. KEY FINDINGS: LXT34 was a potent GPR120 agonist with negligible activity toward human and mouse GPR40. LXT34 could potentiate GSIS and suppress LPS-induced inflammation in macrophages. LXT34 not only markedly improved glucose tolerance and insulin resistance, but also distinctly reduced macrophages infiltration, pro-inflammatory cytokines expression and JNK phosphorylation of both liver and adipose tissues in db/db mice. SIGNIFICANCE: LXT34, a novel and potent GPR120-selective agonist, showed beneficial effects on improving glucose homeostasis in obesity-related type 2 diabetes.

A novel low systemic diacylglycerol acyltransferase 1 inhibitor, Yhhu2407, improves lipid metabolism.

Diacylglycerol acyltransferase 1 (DGAT1) plays a pivotal role in lipid metabolism by catalyzing the committed step in triglyceride (TG) synthesis and has been considered as a potential therapeutic target of multiple metabolic diseases, including dyslipidemia, obesity and type 2 diabetes. Here we report a novel DGAT1 inhibitor, Yhhu2407, which showed a stronger DGAT1 inhibitory activity (IC50 = 18.24 ± 4.72 nM) than LCQ908 (IC50 = 78.24 ± 8.16 nM) in an enzymatic assay and led to a significant reduction in plasma TG after an acute lipid challenge in mice. Pharmacokinetic studies illustrated that Yhhu2407 displayed a low systemic, liver- and intestine-targeted distribution pattern, which is consistent with the preferential tissue expression pattern of DGAT1 and therefore might help to maximize the beneficial pharmacological effects and prevent the occurrence of side effects. Cell-based investigations demonstrated that Yhhu2407 inhibited free fatty acid (FFA)-induced TG accumulation and apolipoprotein B (ApoB)-100 secretion in HepG2 cells. In vivo study also disclosed that Yhhu2407 exerted a beneficial effect on regulating plasma TG and lipoprotein levels in rats, and effectively ameliorated high-fat diet (HFD)-induced dyslipidemia in hamsters. In conclusion, we identified Yhhu2407 as a novel DGAT1 inhibitor with potent efficacy on improving lipid metabolism in rats and HFD-fed hamsters without causing obvious adverse effects.

DGAT1 inhibitors protect pancreatic ß-cells from palmitic acid-induced apoptosis.

Previous studies demonstrated that prolonged exposure to elevated levels of free fatty acids (FFA), especially saturated fatty acids, could lead to pancreatic ß-cell apoptosis, which plays an important role in the progression of type 2 diabetes (T2D). Diacylglycerol acyltransferase 1 (DGAT1), an enzyme that catalyzes the final step of triglyceride (TG) synthesis, has been reported as a novel target for the treatment of multiple metabolic diseases. In this study we evaluated the potential beneficial effects of DGAT1 inhibitors on pancreatic ß-cells, and further verified their antidiabetic effects in db/db mice. We showed that DGAT1 inhibitors (4a and LCQ908) at the concentration of 1 µM significantly ameliorated palmitic acid (PA)-induced apoptosis in MIN6 pancreatic ß-cells and primary cultured mouse islets; oral administration of a DGAT1 inhibitor (4a) (100 mg/kg) for 4 weeks significantly reduced the apoptosis of pancreatic islets in db/db mice. Meanwhile, 4a administration significantly decreased fasting blood glucose and TG levels, and improved glucose tolerance and insulin tolerance in db/db mice. Furthermore, we revealed that pretreatment with 4a (1 µM) significantly alleviated PA-induced intracellular lipid accumulation, endoplasmic reticulum (ER) stress, and proinflammatory responses in MIN6 cells, which might contribute to the protective effects of DGAT1 inhibitors on pancreatic ß-cells. These findings provided a better understanding of the antidiabetic effects of DGAT1 inhibitors.

Cinnamtannin D1 Protects Pancreatic ß-Cells from Glucolipotoxicity-Induced Apoptosis by Enhancement of Autophagy In Vitro and In Vivo.

In our previous study, cinnamtannin D1 (CD-1), one of the A-type procyanidin oligomers isolated from Cinnamomum tamala, was reported to have the activity of antiapoptosis in palmitic acid-treated pancreatic ß cells via alleviating oxidative stress in vitro. In this study, the aim was to further disclose its protective effect and underlying mechanisms against glucolipotoxicity-induced ß-cells apoptosis in vitro and in vivo. We found that CD-1 was able to dose-dependently and time-dependently activate autophagy in INS-1 pancreatic ß-cells. High glucose and palmitic acid (HG/PA)-induced apoptosis and autophagy impairment could be attenuated by CD-1 in INS-1 cells as well as primary cultured murine islets. We also demonstrated that CD-1-induced autophagy was through AMPK/mTOR/ULK1 pathway. Moreover, it was shown that the effects of CD-1 on activation of Keap1/Nrf2 antioxidant signaling pathway and the amelioration of inflammation, endoplasmic reticulum stress, and apoptosis were through autophagy induction in HG/PA-treated INS-1 cells. These protective effects in vivo and hypoglycemic activity of CD-1 were also observed in diabetic db/db mice. These findings have great significance in revealing the antidiabetic mechanisms of procyanidin oligomers and paving the way for their application in the treatment of diabetes.

Exogenous FABP4 interferes with differentiation, promotes lipolysis and inflammation in adipocytes.

PURPOSE: Fatty acid binding protein 4 (FABP4) has been demonstrated to be secreted from adipocytes in an unconventional pathway associated with lipolysis. Circulating FABP4 is elevated in metabolic disorders and has been shown to affect various peripheral cells such as pancreatic ß-cells, hepatocytes and macrophages, but its effects on adipocytes remains unclear. The aim of this study was to investigate the effects of exogenous FABP4 (eFABP4) on adipocyte differentiation and function. METHODS: 3T3-L1 pre-adipocytes or mature adipocytes were treated with recombinant FABP4 in the absence or presence of FABP4 inhibitor I-9/p38 MAPK inhibitor SB203580; Meanwhile male C57BL/6J mice were subcutaneously injected twice a day with recombinant FABP4 (0.35 mg/kg) with or without I-9 (50 mg/kg) for 2 weeks. The effects of eFABP4 on differentiation, lipolysis and inflammation were determined by triglyceride measurement or lipolysis assay, western blotting, or RT-qPCR analysis. RESULTS: eFABP4 treatment significantly reduced intracellular triglyceride content and decreased expression of adipogenic markers peroxisome proliferator-activated receptor gamma (PPARγ), CCAAT/enhancer binding protein alpha (C/EBPα), intracellular FABP4, and adiponectin in 3T3-L1 cells. Besides, eFABP4 promoted lipolysis and inflammation in differentiated 3T3-L1 adipocytes as well as in adipose tissue of eFABP4-treated C57BL/6J mice, with elevated gene expression of monocyte chemoattractant protein (MCP)-1, tumor necrosis factor (TNF)-α, and elevated protein expression of adipose triglyceride lipase (ATGL), phosphorylation of hormone-sensitive lipase (HSL) (Ser-660), p38, and nuclear factor-kappa B (NF-κB). The pro-inflammatory and pro-lipolytic effects of eFABP4 could be reversed by SB203580/I-9. CONCLUSIONS: These findings indicate that eFABP4 interferes with adipocyte differentiation, induces p38/HSL mediated lipolysis and p38/NF-κB mediated inflammation in adipocytes in vitro and in vivo.

Procyanidin C1, a Component of Cinnamon Extracts, Is a Potential Insulin Sensitizer That Targets Adipocytes.

Natural products are one of the main sources for discovering new lead compounds. We previously reported that cinnamon extract has a promising effect in regulating lipid tissue volume and insulin sensitivity in vivo. However, its effective component and the underlying mechanism are not known. In the present study, we analyzed the effect of different components of cinnamon on regulating insulin sensitivity in 3T3-L1 adipocytes. Functional assay revealed that, of the six major components of cinnamon extracts, the B-type procyanidin, procyanidin C1, improves the differentiation of 3T3-L1 cells (TG content: 1.10 ± 0.09 mM at a dosage of 25 µM vs 0.67 ± 0.02 mM in vehicle group, p < 0.001) and promotes insulin-induced glucose uptake (8.58 ± 1.43 at a dosage of 25 µM vs 3.05 ± 1.24 in vehicle group, p < 0.001). Mechanism studies further suggested that procyanidin C1 activates the AKT-eNOS pathway, thus up-regulating glucose uptake and enhancing insulin sensitivity in mature adipocytes. Taken together, our study identified B-type procyanidin C1, a component of cinnamon extract, that stimulates preadipocyte differentiation and acts as a potential insulin action enhancer through the AKT-eNOS pathway in mature adipocytes.

From hit to lead: Structure-based discovery of naphthalene-1-sulfonamide derivatives as potent and selective inhibitors of fatty acid binding protein 4.

Fatty acid binding protein 4 (FABP4) plays a critical role in metabolism and inflammatory processes and therefore is a potential therapeutic target for immunometabolic diseases such as diabetes and atherosclerosis. Herein, we reported the identification of naphthalene-1-sulfonamide derivatives as novel, potent and selective FABP4 inhibitors by applying a structure-based design strategy. The binding affinities of compounds 16dk, 16do and 16du to FABP4, at the molecular level, are equivalent to or even better than that of BMS309403. The X-ray crystallography complemented by the isothermal titration calorimetry studies revealed the binding mode of this series of inhibitors and the pivotal network of ordered water molecules in the binding pocket of FABP4. Moreover, compounds 16dk and 16do showed good metabolic stabilities in liver microsomes. Further extensive in vivo study demonstrated that 16dk and 16do exhibited a dramatic improvement in glucose and lipid metabolism, by decreasing fasting blood glucose and serum lipid levels, enhancing insulin sensitivity, and ameliorating hepatic steatosis in obese diabetic (db/db) mice.

Benzbromarone aggravates hepatic steatosis in obese individuals.

As a widely used anti-gout drug, benzbromarone has been found to induce hepatic toxicity in patients during clinical treatment. Previous studies have reported that benzbromarone is metabolized via cytochrome P450, thus causing mitochondrial toxicity in hepatocytes. In this study, we found that benzbromarone significantly aggravated hepatic steatosis in both obese db/db mice and high fat diet (HFD)-induced obese (DIO) mouse models. However, benzbromarone had less effect on the liver of lean mice. It was found that the expression of mRNAs encoding lipid metabolism and some liver-specific genes were obviously disturbed in benzbromarone-treated DIO mice compared to the control group. The inflammatory and oxidative stress factors were also activated in the liver of benzbromarone-treated DIO mice. In accordance with the in vivo results, an in vitro experiment using human hepatoma HepG2 cells also confirmed that benzbromarone promoted intracellular lipid accumulation under high free fatty acids (FFAs) conditions by regulating the expression of lipid metabolism genes. Importantly, prolonged treatment of benzbromarone significantly increased cell apoptosis in HepG2 cells in the presence of high FFAs. In addition, in benzbromarone-treated hyperuricemic patients, serum transaminase levels were positively correlated with patients' obesity level. CONCLUSION: This study demonstrated that benzbromarone aggravated hepatic steatosis in obese individuals, which could subsequently contribute to hepatic cell injury, suggesting a novel toxicological mechanism in benzbromarone-induced hepatotoxicity.

Isolation, identification and bioactivities of abietane diterpenoids from Premna szemaoensis.

Investigation of the leaves and stems of Premna szemaoensis resulted in the isolation of twelve new abietane diterpenoids, szemaoenoids A-L (1-12), together with four known abietane diterpenoids (13-16). The structures involved two rearranged-abietane skeletons: 17(15 → 16)-abeo-abietane (7, 10-12, 14 and 15) and 17(15 → 16),18(4 → 3)-diabeo-abietane (1-6, 13 and 16). The structures of the new compounds were established mainly by analyzing NMR and HRESIMS data. The absolute configurations of 1, 3 and 10 were confirmed by single crystal X-ray diffraction analysis. In bioactivity assays, compounds 11, 12, 14 and 15 were active against two human colon cancer cell lines (HCT-116 and HT-29) with IC50 values ranging from 8.8 to 34.3 µM, and compounds 10, 13 and 14 exhibited effective free radical scavenging activity with IC50 values ranging from 35.6 to 41.5 µM by DPPH experiment.

Isoprenylated phenolic compounds with tyrosinase inhibition from Morus nigra.

A new isoprenylated sanggenon-type flavanone, nigrasin K (1), together with three known analogs (2-4) and five known Diels-Alder adducts (5-9), were isolated from the twigs of Morus nigra. Their structures were elucidated by spectroscopic methods. Sanggenon M (2), chalcomoracin (5), sorocein H (6), kuwanon J (7), sanggenon C (8), and sanggenon O (9) showed significant inhibitory effects on mushroom tyrosinase.

5,4'-Dihydroxy-7,8-dimethoxyflavanone and Aliarin from Dodonaea viscosa Are Activators of PPARγ.

PPARγ agonists are widely used medications in diabetes mellitus therapy. Their role in improving adipose tissue function contributes to antidiabetic effects. The extracts of Dodonaea viscosa have been reported to exert antidiabetic activity. However, the effective mediators and the underlying mechanisms were largely unknown. In this study, we investigated the action on PPARγ transactivation and adipocyte modulation of two typical flavonoid constituents from D. viscosa, 5,4'-dihydroxy-7,8-dimethoxyflavanone and aliarin. Our results showed that 5,4'-dihydroxy-7,8-dimethoxyflavanone and aliarin were potential partial PPARγ agonists. The compounds induced adipogenesis in 3T3-L1 cells, with an upregulated adiponectin mRNA level and enhanced insulin sensitivity. The favorable effects of 5,4'-dihydroxy-7,8-dimethoxyflavanone, aliarin, and other flavonoid constituents on adipocytes might contribute to the antidiabetic efficacy of D. viscosa.

Combined Virtual Screening and Substructure Search for Discovery of Novel FABP4 Inhibitors.

Fatty acid-binding protein 4 (FABP4, AFABP) is a potential drug target for diabetes and atherosclerosis. In this study, a series of novel FABP4 inhibitors were discovered through combining virtual screening and substructure search. Seventeen compounds exhibited FABP4 inhibitory activities with IC50 < 10 µM, among which 11 compounds showed high selectivity against FABP3. The best compound 36b displayed an IC50 value of 1.5 µM. Molecular docking and point mutation studies revealed that Gln95, Arg126, and Tyr128 play key roles for these compounds binding with FABP4. Interestingly, Gln95 seems to be essential for conformation stability of FABP4. The new scaffolds of these compounds and their interaction mechanisms binding with FABP4 should provide an important clue for the further development of novel FABP4 inhibitors.

Ginsenoside Rb2 Alleviates Hepatic Lipid Accumulation by Restoring Autophagy via Induction of Sirt1 and Activation of AMPK.

Although Panax ginseng is a famous traditional Chinese medicine and has been widely used to treat a variety of metabolic diseases including hyperglycemia, hyperlipidemia, and hepatosteatosis, the effective mediators and molecular mechanisms remain largely unknown. In this study we found that ginsenoside Rb2, one of the major ginsenosides in Panax ginseng, was able to prevent hepatic lipid accumulation through autophagy induction both in vivo and in vitro. Treatment of male db/db mice with Rb2 significantly improved glucose tolerance, decreased hepatic lipid accumulation, and restored hepatic autophagy. In vitro, Rb2 (50 µmol/L) obviously increased autophagic flux in HepG2 cells and primary mouse hepatocytes, and consequently reduced the lipid accumulation induced by oleic acid in combination with high glucose. Western blotting analysis showed that Rb2 partly reversed the high fatty acid in combination with high glucose (OA)-induced repression of autophagic pathways including AMP-activated protein kinase (AMPK) and silent information regulator 1 (sirt1). Furthermore, pharmacological inhibition of the sirt1 or AMPK pathways attenuated these beneficial effects of Rb2 on hepatic autophagy and lipid accumulation. Taken together, these results suggested that Rb2 alleviated hepatic lipid accumulation by restoring autophagy via the induction of sirt1 and activation of AMPK, and resulted in improved nonalcoholic fatty liver disease (NAFLD) and glucose tolerance.

New Bicyclic Cembranoids from the South China Sea Soft Coral Sarcophyton trocheliophorum.

Nine new bicyclic cembranoids, sarcophytrols M-U(1-9), were isolated from the South China Sea soft coral Sarcophyton trocheliophorum as minor components, along with one known related cembranoid 10. Their structures were elucidated by detailed spectroscopic analysis and chemical conversion. The chemical structures of these metabolites are characterized by the different patterns of the additional cyclization within the 14-member skeleton, which leading to the formation of furan, pyran, oxepane, and peroxyl rings, respectively. Among them, sarcophytrols R and S(6 and 7) share a rare decaryiol skeleton with an unusual C12/C15 cyclization. In addition, the absolute configurations of sarcophytrols M and T(1 and 8) were determined by the modified Mosher's method. The research of these new secondary metabolites provided a further understanding of the diversity of cyclized cembranoids from the title species.

Docking-based structural splicing and reassembly strategy to develop novel deazapurine derivatives as potent B-RafV600E inhibitors.

The mutation of B-RafV600E is widespread in a variety of human cancers. Its inhibitors vemurafenib and dabrafenib have been launched as drugs for treating unresectable melanoma, demonstrating that B-RafV600E is an ideal drug target. This study focused on developing novel B-RafV600E inhibitors as drug leads against various cancers with B-RafV600E mutation. Using molecular modeling approaches, 200 blockbuster drugs were spliced to generate 283 fragments followed by molecular docking to identify potent fragments. Molecular structures of potential inhibitors of B-RafV600E were then obtained by fragment reassembly followed by docking to predict the bioactivity of the reassembled molecules. The structures with high predicted bioactivity were synthesized, followed by in vitro study to identify potent B-RafV600E inhibitors. A highly potent fragment binding to the hinge area of B-RafV600E was identified via a docking-based structural splicing approach. Using the fragment, 14 novel structures were designed by structural reassembly, two of which were predicted to be as strong as marketed B-RafV600E inhibitors. Biological evaluation revealed that compound 1m is a potent B-RafV600E inhibitor with an IC50 value of 0.05 µmol/L, which was lower than that of vemurafenib (0.13 µmol/L). Moreover, the selectivity of 1m against B-RafWT was enhanced compared with vemurafenib. In addition, 1m exhibits desirable solubility, bioavailability and metabolic stability in in vitro assays. Thus, a highly potent and selective B-RafV600E inhibitor was designed via a docking-based structural splicing and reassembly strategy and was validated by medicinal synthesis and biological evaluation.

Discovery of Potent and Orally Bioavailable GPR40 Full Agonists Bearing Thiophen-2-ylpropanoic Acid Scaffold.

The free fatty acid receptor GPR40 is predominantly expressed in pancreatic ß-cells and enhances insulin secretion in a glucose dependent manner. Therefore, GPR40 agonists are possible novel insulin secretagogues with reduced or no risk of hypoglycemia for the treatment of type 2 diabetes mellitus (T2DM). Chemically and structurally diverse GPR40 agonists with high safety are pursued for the clinical development of GPR40-based pharmacotherapeutics. Herein we report our design and discovery of a new chemotype of GPR40 agonists free of the typical phenylpropanoic acid scaffold. The thiophen-2-ylpropanoic acid containing GPR40 modulators functioned as full agonists with high-efficacy response (Emax) and reduced lipophilicity. Significantly, the lead compound in this series, (R)-7k, exhibited more potent in vitro glucose-stimulated insulin secretion and in vivo glucose-lowering effects (10 mg/kg, po) than the GPR40 partial agonist TAK-875, which was once in phase III clinical trials, and high selectivity over the relevant receptors GPR120 and PPARγ.