Design and synthesis of 2-substituted benzoxazoles as novel PTP1B inhibitors

A series of benzoxazole compounds containing oxamic acid were synthesized and screened for the PTP1B inhibition. Compound 31d showed best biochemical potency (K_i) of 6.7 μM. Structure–activity relationship were explained with the help of molecular modeling approach.     

Flaxseed (Linum usitatissimum L.) extract as well as (+)-secoisolariciresinol diglucoside and its mammalian derivatives are potent inhibitors of α-amylase activity

Type 2 diabetes mellitus (T2DM) is one of the common global diseases. Flaxseed is by far the richest source of the dietary lignans (i.e., secoisolariciresinol diglucoside) which have been shown to delay the development of T2DM in animal models. Herein, we propose the first evidences for a mechanism of action involving the inhibition of the pancreatic α-amylase (EC 3.2.1.1) by flaxseed-derived lignans that could therefore constitute a promising nutraceutical for the prevention and the treatment of T2DM.     

Metformin restores the correlation between serum-oxidized LDL and leptin levels in type 2 diabetic patients

Abstract

Introduction

Leptin has lipid peroxidation properties in healthy individuals. Here we aimed to study the correlation between serum-oxidized low-density lipoprotein (ox-LDL) and leptin levels in patients with type 2 diabetes. We also studied the effect of metformin therapy on the correlation between serum ox-LDL and leptin levels in patients with newly diagnosed diabetes.

Methods

We performed a cross-sectional study on two groups of patients with type 2 diabetes stratified according to (1) patients with newly diagnosed diabetes and (2) patients with long-standing diabetes plus healthy controls. Patients with newly diagnosed diabetes were followed for 3 months after the initiation of metformin therapy.

Results

Patients with type 2 diabetes had a higher serum ox-LDL, ox-LDL/LDL ratio, waist circumference, fasting blood sugars (FBSs), hemoglobin A1C (HbA1C), triglyceride, homeostatic model assessment of insulin resistance (HOMA-IR) and a lower serum leptin levels than controls. Serum ox-LDL, ox-LDL/LDL ratio (0.08 (0.08–0.12) vs. 0.06 (0.05–0.08), P < 0.001) and HOMA-IR (3.26 ± 0.23 vs. 2.93 ± 0.32; P < 0.01) were decreased when serum leptin levels (15.9 ± 1.6 vs. 21.4 ± 2.5, P < 0.01) were increased after 3 months of metformin therapy. This remained significant after multiple adjustments for age, body mass index, FBS, HbA1c, and HOMA-IR. Leptin was significantly correlated with ox-LDL/LDL ratio in controls (r = 0.78, P < 0.01), and in patients with newly diagnosed diabetes (r = 0.4, P < 0.05), after metformin therapy. There were not any correlation between leptin and ox-LDL/LDL ratio in patients with long-standing diabetes and patients with newly diagnosed diabetes before treatment.

Discussion

Metformin restores the positive correlation between serum ox-LDL and leptin levels in patients with type 2 diabetes.     

Characterization of oxidative stress in blood from diabetic vs. hypercholesterolaemic patients,using a novel synthesized marker

In the present study, we extend our novel concept of designing and using exogenous markers for the characterization of oxidative stress (OS) and OS-associated diseases. The aim was to use such a synthetic compound as a tool for studying OS in blood from diabetic and hypercholesterolaemic (Hc) patients. The marker used N-linoleoyl tyrosine (LT) was constructed from tyrosine and linoleic acid (LA); both components are known to be easily oxidized upon exposure to different types of reactive oxygen/nitrogen species (ROS/RNS), and to generate specific oxidized products, depending on the type of oxidants present in vivo. Using the LT probe, we showed that the ratios of oxidized LT to total LT (Ox-LT/LT) is significantly higher in blood samples obtained from diabetic patients, than in Hc patients or healthy control subjects. LC/MS analysis revealed that blood from diabetic patients oxidizes the marker with predominant formation of Ox-LT hydroperoxide (LT-OOH) and epoxide (epoxy-LT), where the LA moiety is oxidized to hydroperoxide and to epoxide, respectively. Analysis of oxysterol levels in these samples (GC/MS) revealed that the blood of both diabetic and Hc patients contained significantly more oxysterols than blood of control subjects. Consumption of pomegranate juice by diabetic patients for 3 months suppressed their blood capacity to oxidize the LT and similarly also reduced their blood oxysterol/total cholesterol ratio by 93%. The use of an exogenous marker to characterize OS in blood samples yields important information on the extent of OS, and can provide a fingerprint for the early identification of different pathological conditions associated with OS.     

The influence of blood glucose on neutrophil function in individuals without diabetes

We assessed the association of neutrophil function with glycated hemoglobin (HbA1c) levels in a Japanese general population. Participants were 809 males and females who were over 20 years old living in the Iwaki region in Aomori Prefecture located in northern Japan. Lifestyle parameters (smoking, alcohol consumption, and exercise habits), HbA1c and neutrophil function such as reactive oxygen species (ROS) production capability and phagocytic activity (PA) were measured. ROS production capability was measured before and after phagocytic stimulus to obtain basal ROS production and stimulated ROS production. Level of HbA1c had a positive correlation with basal ROS production (p=0.053), a negative correlation with stimulated ROS production (p=0.072) and PA (p=0.059) only in post‐menopausal groups, and not in pre‐menopausal groups. However, there were no correlations between levels of HbA1c and neutrophil functions in male. In conclusion, in the present study, despite the presence of diabetes, chronic hyperglycemia was found to cause an increase in daily basal ROS production of neutrophils, and increased susceptibility to infection caused by reduced neutrophilic reaction in females in their menopause. Therefore, from the oxidative point of view, strict glycemic control is necessary to prevent post‐menopausal females from developing diabetic complications in spite of the presence of diabetes.     

Near Infrared Optical Projection Tomography for Assessments of β-cell Mass Distribution in Diabetes Research

By adapting OPT to include the capability of imaging in the near infrared (NIR) spectrum, we here illustrate the possibility to image larger bodies of pancreatic tissue, such as the rat pancreas, and to increase the number of channels (cell types) that may be studied in a single specimen. We further describe the implementation of a number of computational tools that provide: 1/ accurate positioning of a specimen''s (in our case the pancreas) centre of mass (COM) at the axis of rotation (AR)²; 2/ improved algorithms for post-alignment tuning which prevents geometric distortions during the tomographic reconstruction² and 3/ a protocol for intensity equalization to increase signal to noise ratios in OPT-based BCM determinations³. In addition, we describe a sample holder that minimizes the risk for unintentional movements of the specimen during image acquisition. Together, these protocols enable assessments of BCM distribution and other features, to be performed throughout the volume of intact pancreata or other organs (e.g. in studies of islet transplantation), with a resolution down to the level of individual islets of Langerhans.     

Effect of bis[curcumino]oxovanadium complex on non-diabetic and streptozotocin-induced diabetic rats

The effect of the vanadium complex bis[curcumino]oxovanadium (BCOV) on blood glucose level, serum lipid levels, blood pressure and vascular reactivity were studied in non-diabetic and streptozotocin-induced diabetic (STZ-diabetic) rats and compared to that of vanadyl sulfate. Blood glucose level, serum lipid levels, and blood pressure were significantly increased in STZ-diabetic rats. Vascular reactivity to various agonists such as noradrenaline and acetylcholine were significantly increased in STZ-diabetic rats. Blood glucose and serum lipid levels were restored to normal in STZ-diabetic animals treated with vanadyl sulfate at a concentration of 0.5 mmol/kg/day (p.o.). However, vanadyl sulfate at a concentration of 0.2 mmol/kg/day (p.o.) did not produce any significant change in blood glucose and lipid levels. There was no significant effect of vanadyl sulfate (0.2 or 0.5 mmol/kg/day) treatment on blood pressure and vascular reactivity in STZ-diabetic rats. Vanadyl sulfate significantly reduced the body weight of non-diabetic and STZ-diabetic rats. Moreover, it also caused severe diarrhea in both groups of animals. Treatment with BCOV (0.05, 0.1 and 0.2mmol/kg/day, p.o.) significantly decreased blood glucose level and serum lipids in STZ-diabetic rats. Furthermore, administration of BCOV to STZ-diabetic rats restored the blood pressure and vascular reactivity to agonists to normal. There was no significant change in the body weight of BCOV treated non-diabetic and STZ-diabetic rats. Diarrhea was not observed in both BCOV treated groups. In conclusion, the present study shows that the vanadium complex BCOV has antidiabetic and hypolipedimic effects. In addition, it improves the cardiovascular complications associated with diabetes.     

Divergent Sequence Tunes Ligand Sensitivity in Phospholipid-regulated Hormone Receptors

The members of the NR5A subfamily of nuclear receptors (NRs) are important regulators of pluripotency, lipid and glucose homeostasis, and steroidogenesis. Liver receptor homologue 1 (LRH-1; NR5A2) and steroidogenic factor 1 (SF-1; NR5A1) have therapeutic potential for the treatment of metabolic and neoplastic disease; however, a poor understanding of their ligand regulation has hampered the pursuit of these proteins as pharmaceutical targets. In this study, we dissect how sequence variation among LRH-1 orthologs affects phospholipid (PL) binding and regulation. Both human LRH-1 (hLRH-1) and mouse LRH-1 (mLRH-1) respond to newly discovered medium chain PL agonists to modulate lipid and glucose homeostasis. These PLs activate hLRH-1 by altering receptor dynamics in a newly identified alternate activation function region. Mouse and Drosophila orthologs contain divergent sequences in this region potentially altering PL-driven activation. Structural evidence suggests that these sequence differences in mLRH-1 and Drosophila FTZ-f1 (dmFTZ-f1) confer at least partial ligand independence, making them poor models for hLRH-1 studies; however, the mechanisms of ligand independence remain untested. We show using structural and biochemical methods that the recent evolutionary divergence of the mLRH-1 stabilizes the active conformation in the absence of ligand, yet does not abrogate PL-dependent activation. We also show by mass spectrometry and biochemical assays that FTZ-f1 is incapable of PL binding. This work provides a structural mechanism for the differential tuning of PL sensitivity in NR5A orthologs and supports the use of mice as viable therapeutic models for LRH-1-dependent diseases.     

Derivation of Human Induced Pluripotent Stem Cells from Patients with Maturity Onset Diabetes of the Young

Maturity onset diabetes of the young (MODY) is an autosomal dominant disease. Despite extensive research, the mechanism by which a mutant MODY gene results in monogenic diabetes is not yet clear due to the inaccessibility of patient samples. Induced pluripotency and directed differentiation toward the pancreatic lineage are now viable and attractive methods to uncover the molecular mechanisms underlying MODY. Here we report, for the first time, the derivation of human induced pluripotent stem cells (hiPSCs) from patients with five types of MODY: MODY1 (HNF4A), MODY2 (GCK), MODY3 (HNF1A), MODY5 (HNF1B), and MODY8 (CEL) with a polycistronic lentiviral vector expressing a Cre-excisable human “stem cell cassette” containing the four reprogramming factors OCT4, KLF4, SOX2, and CMYC. These MODY-hiPSCs morphologically resemble human pluripotent stem cells (hPSCs), express pluripotency markers OCT4, SOX2, NANOG, SSEA-4, and TRA-1–60, give rise to derivatives of the three germ layers in a teratoma assay, and are karyotypically normal. Overall, our MODY-hiPSCs serve as invaluable tools to dissect the role of MODY genes in the development of pancreas and islet cells and to evaluate their significance in regulating beta cell function. This knowledge will aid future attempts aimed at deriving functional mature beta cells from hPSCs.     

FOG2 Protein Down-regulation by Transforming Growth Factor-β1-induced MicroRNA-200b/c Leads to Akt Kinase Activation and Glomerular Mesangial Hypertrophy Related to Diabetic Nephropathy

Glomerular hypertrophy is a hallmark of diabetic nephropathy. Akt kinase activated by transforming growth factor-β1 (TGF-β) plays an important role in glomerular mesangial hypertrophy. However, the mechanisms of Akt activation by TGF-β are not fully understood. Recently, miR-200 and its target FOG2 were reported to regulate the activity of phosphatidylinositol 3-kinase (the upstream activator of Akt) in insulin signaling. Here, we show that TGF-β activates Akt in glomerular mesangial cells by inducing miR-200b and miR-200c, both of which target FOG2, an inhibitor of phosphatidylinositol 3-kinase activation. FOG2 expression was reduced in the glomeruli of diabetic mice as well as TGF-β-treated mouse mesangial cells (MMC). FOG2 knockdown by siRNAs in MMC activated Akt and increased the protein content/cell ratio suggesting hypertrophy. A significant increase of miR-200b/c levels was detected in diabetic mouse glomeruli and TGF-β-treated MMC. Transfection of MMC with miR-200b/c mimics significantly decreased the expression of FOG2. Conversely, miR-200b/c inhibitors attenuated TGF-β-induced decrease in FOG2 expression. Furthermore, miR-200b/c mimics increased the protein content/cell ratio, whereas miR-200b/c inhibitors abrogated the TGF-β-induced increase in protein content/cell. In addition, down-regulation of FOG2 by miR-200b/c could activate not only Akt but also ERK, which was also through PI3K activation. These data suggest a new mechanism for TGF-β-induced Akt activation through FOG2 down-regulation by miR-200b/c, which can lead to glomerular mesangial hypertrophy in the progression of diabetic nephropathy.