Synthesis of β‐Ketoamide Curcumin Analogs for Anti‐Diabetic and AGEs Inhibitory Activities

Two different series of novel β‐ketoamide curcumin analogs enriched in biological activities have been synthesized. The synthesized compounds were screened for their in vitro anti‐diabetic and AGEs inhibitory activities and exhibited potent to good anti‐diabetic and AGEs inhibitory activities. The molecular docking study was also performed with the α‐amylase enzyme.     

Nonenzymatic glycation of guanosine 5'-triphosphate by glyceraldehyde: an in vitro study of AGE formation

Guanosine 5'-triphosphate (GTP) plays a significant role in the bioenergetics, metabolism, and signaling of cells; consequently, any modifications to the structure of the molecule can have profound effects on a cell's survival and function. Previous studies in our laboratory demonstrated that like proteins, purines, and pyrimidines can nonenzymatically react with sugars to generate advanced glycation endproducts (AGEs) and that these AGEs can form in vitro under physiological conditions. The objective of this investigation was twofold. First, it was to evaluate the susceptibility of ATP, GTP, CTP, and TTP to nonenzymatic modification by D-glucose and DL-glyceraldehyde, and second to assess the effect of various factors such as temperature, pH and incubation time, and sugar concentration on the rate and extent of nucleotide triphosphate AGE formation. Of the four nucleotide triphosphates that were studied, only GTP was significantly reactive forming a heterogeneous group of compounds with DL-glyceraldehyde. D-Glucose exhibited no significant reactivity with any of the nucleotide triphosphates, a finding that was supported by UV and fluorescence spectroscopy. Capillary electrophoresis, high-performance liquid chromatography and mass spectrometry allowed for a thorough analysis of the glycated GTP products and demonstrated that the modification of GTP by dl-glyceraldehyde occurred via the classical Amadori pathway.     

Polyphenols from flowers of Magnolia coco and their anti-glycation effects

We investigated the inhibitory effects of several plant extracts on advanced glycation end-products (AGEs) formation. Among tested samples, the flower extract of Magnolia coco showed significant inhibition of AGE formation. We isolated and characterized procyanidin oligomer and four other compounds from the flowers, and evaluated their inhibitory effects on AGE formation and the AGE-derived crosslink-cleaving activity of the isolated compounds.     

3-Arylcoumarin inhibits vascular calcification by inhibiting the generation of AGEs and anti-oxidative stress

ObjectiveThis work aims to screen drugs for preventing and treating vascular calcification. Method: We screened a series of 3-arylcoumarins for the detection of vascular calcification-associated factors using human aortic vascular smooth muscle cells.ResultsWe found that compounds 14 and 32 significantly inhibited alkaline phosphatase (ALP) activity similar to aminoguanidine hydrochloride (AGH) in a cellular model of AGEs-induced calcification. We also found that compounds 14 and 32 could significantly decrease the levels of factors such as AGEs, intracellular calcium ions, and total ROS in the calcified cell model. Further study indicates that compound 14 could significantly inhibit the expression of P-ERK1/2, PKC, NF-κB, RAGE and OPN proteins and increased the expression of SM22-α and PPAR-γ proteins in the calcified cells.ConclusionWe speculate that compound 14 inhibits vascular calcification by inhibiting oxidative stress and inhibiting AGEs production, suggesting that 3-arylcoumarin derivatives are potential candidates for the treatment of vascular calcification.     

葡萄糖修饰人血浆载脂蛋白的肽类标志物

目的:研究葡萄糖对血浆中载脂蛋白的修饰作用,寻找标志性肽段,作为临床诊断糖尿病以及衰老相关疾病的生物标志物。方法:将蛋白质组学和生物信息学相结合,采用LC/MS联用技术寻找差异肽段。结果:载脂蛋白(APOA1)与葡萄糖发生糖基化反应,导致正常肽段的含量发生变化,并生成早期糖基化产物果糖胺。而糖尿病人体内的APOA1也同样会发生这种非酶糖基化修饰,其中的一些肽段也出现类似的变化情况。结论:筛选出五个肽段,将有可能作为临床诊断糖尿病以及与衰老相关疾病的生物标志物。     

吡哆胺-一种天然的AGEs/ALEs抑制剂

衰老及老年相关疾病,如：糖尿病、动脉粥状硬化、各种神经退行性疾病等,与组织蛋白氧化修饰密切相关．在造成蛋白质氧化修饰的反应中,非酶糖基化和脂质过氧化是最重要的两类,它们最终形成非酶糖基化终产物(AGEs)和脂过氧化终产物(ALEs)．基于羰基毒害衰老理论,具有强烈反应活性的羰基类化合物是非酶糖基化和脂质过氧化的共同中间产物,它们是造成蛋白修饰的直接原因之一．吡哆胺是维生素B6的一种天然成分;由于它能直接清除羰基类化合物,从而抑制AGEs／ALEs的生成;又因为吡哆胺对人体副作用很小．因此吡哆胺有望成为一种新型的防治多种老年相关疾病的药物．     

Glycation end-products specific auto-antibodies in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease, which is highly inflammatory. Compared to a healthy control group, SLE patients exhibit a higher concentration of advanced glycation end products (AGEs) and a lower concentration of receptors for AGEs (RAGE) in serum, however, the exact aetiology is still unclear. In the present study, non-enzymatic glycation induced modification of human serum albumin (HSA) has been studied by biophysical techniques. Glycated HSA (G-HSA) was used as an antigen, and serum autoantibody levels were estimated in SLE and normal humans (NH) against it, using direct binding ELISA and competitive inhibition ELISA. Compared to N-HSA, remarkable structural modifications were observed in G-HSA. Modified HSA also showed increased pentosidine fluorescence (213.7 ± 13.4 AU). Glycation of HSA induced a conversion of α-helix and random coil to β-sheet and β-turns. Serum immuno assays results exhibited significantly (p < 0.001) higher binding of G-HSA with serum autoantibodies from SLE patients when compared with native HSA (N-HSA). Furthermore, competitive ELISA results showed significantly (p < 0.001) high percent inhibition of serum IgG from SLE patients with modified antigen. Chronic inflammation with excessive oxidative stress in SLE patients could be a possible reason for structural alterations in blood proteins, generating highly immunogenic unique new-epitopes. These in turn induce the generation of specific autoantibodies against G-HSA that may serve as a potential biomarker for SLE pathogenesis.     

Nε-carboxymethyllysine-mediated endoplasmic reticulum stress promotes endothelial cell injury through Nox4/MKP-3 interaction

N^ε-carboxymethyllysine (CML) is an important driver of diabetic vascular complications and endothelial cell dysfunction. However, how CML dictates specific cellular responses and the roles of protein tyrosine phosphatases and ERK phosphorylation remain unclear. We examined whether endoplasmic reticulum (ER) localization of MAPK phosphatase-3 (MKP-3) is critical in regulating ERK inactivation and promoting NADPH oxidase-4 (Nox4) activation in CML-induced endothelial cell injury. We demonstrated that serum CML levels were significantly increased in type 2 diabetes patients and diabetic animals. CML induced ER stress and apoptosis, reduced ERK activation, and increased MKP-3 protein activity in HUVECs and SVECs. MKP-3 siRNA transfection, but not that of MKP-1 or MKP-2, abolished the effects of CML on HUVECs. Nox4-mediated activation of MKP-3 regulated the switch to ERK dephosphorylation. CML also increased the integration of MKP-3 with ERK, which was blocked by silencing MKP-3. Exposure of antioxidants abolished CML-increased MKP-3 activity and protein expression. Furthermore, immunohistochemical staining of both MKP-3 and CML was increased, but phospho-ERK staining was decreased in the aortic endothelium of streptozotocin-induced and high-fat diet-induced diabetic mice. Our results indicate that an MKP-3 pathway might regulate ERK dephosphorylation through Nox4 during CML-triggered endothelial cell dysfunction/injury, suggesting that therapeutic strategies targeting the Nox4/MKP-3 interaction or MKP-3 activation may have clinical implications for diabetic vascular complications.     

Direct inhibitory and indirect stimulatory effects of RAGE ligand S100 on sRANKL‐induced osteoclastogenesis

Diabetes results in increased fracture risk, and advance glycation endproducts (AGEs) have been implicated in this pathophysiology. S100 proteins are ligands for the receptor of AGEs (RAGE). An intracellular role of the S100 family member S100A4 (Mts1) to suppress mineralization has been described in pre‐osteoblastic MC3T3‐E1 cells. However, S100 proteins could have additional effects on bone. The goal of the current study was to determine effects of increased extracellular S100 on osteoclastogenesis. We first determined the direct effects of S100 on pre‐osteoclast proliferation and osteoclastic differentiation. RANKL‐treated RAW 264.7 cell proliferation and TRAP activity were significantly inhibited by S100, and the number and size of TRAP‐positive multinucleated cells were decreased. We then determined whether S100 could affect osteoclastogenesis by an indirect process by examining effects of conditioned media from S100‐treated MC3T3‐E1 cells on osteoclastogenesis. In contrast to the direct inhibitory effect of S100, the conditioned media promoted RAW 264.7 cell proliferation and TRAP activity, with a trend toward increased TRAP‐positive multinucleated cells. S100 treatment of the MC3T3‐E1 cells for 14 days did not significantly affect alkaline phosphatase, M‐CSF, or OPG gene expression. RANKL was undetectable in both untreated and treated cells. The treatment slightly decreased MC3T3‐E1 cell proliferation. Interestingly, S100 treatment increased expression of RAGE by the MC3T3‐E1 cells. This suggested the possibility that S100 could increase soluble RAGE, which acts as a decoy receptor for S100. This decrease in availability of S100, an inhibitor of pre‐osteoclast proliferation, could contribute to osteoclastogenesis, ultimately resulting in increased bone resorption. J. Cell. Biochem. 107: 917–925, 2009. © 2009 Wiley‐Liss, Inc.     

Proanthocyanidin and anthocyanins from the hulls and beards of red-kerneled rice and their antiglycation properties

In the current study, we isolated a proanthocyanidin oligomer from the hulls of red-kerneled rice. The structure of the oligomer was characterized based on spectral data and chemical reaction. Furthermore, two anthocyanins were isolated from the beards of the same source. The proanthocyanidins and beard extract showed more potent inhibitory and cleaving activities than those of positive controls, respectively.