A novel strategy for production of liraglutide precursor peptide and development of a new long-acting incretin mimic.

Nowadays, a small number of incretin mimics are used to treat type 2 diabetes mellitus (T2DM) due to their longer half-life. The present study aimed to introduce a novel method for producing the liraglutide precursor peptide (LPP) and developing a potentially new incretin mimic. Here, human αB-crystallin (αB-Cry) was ligated to the LPP at the gene level, and the gene construct was expressed in Escherichia coli with a relatively good efficiency. The hybrid protein (αB-lir) was then purified by a precipitation method followed by anion exchange chromatography. After that, the peptide was released from the carrier protein by a chemical cleavage method yielding about 70%. The LPP was then purified by gel filtration chromatography, and HPLC estimated its purity to be about 98%. Also, the molecular mass of the purified peptide was finally confirmed by mass spectroscopy analysis. Assessment of the secondary structures suggested a dominant α-helical structure for the LPP and a ß-sheet rich structure for the hybrid protein. The subcutaneous injection of the LPP and the αB-lir hybrid protein significantly reduced the blood sugar levels in healthy and diabetic mice and stimulated insulin secretion. Also, the hybrid protein exerts its bioactivities more effectively than the LPP over a relatively longer period of time. The results of this study suggested a novel method for the easy and cost-effective production of the LPP and introduced a new long-acting incretin mimic that can be potentially used for the treatment of T2DM patients.

The biochemical association between R157H mutation in human αB-crystallin and development of cardiomyopathy: Structural and functional analyses of the mutant protein.

In human αB-crystallin or HspB5, the substitution of arginine residue at position 157 with histidine has been reported to cause cardiomyopathy. In this study, the impact of R157H mutation on the structure, stability and functional properties of human αB-crystallin was investigated using a variety of spectroscopic techniques and microscopic analyses. Our spectroscopic analyses revealed that this mutation has a negligible impact on the secondary and tertiary structures of HspB5 but its quaternary structure underwent fundamental changes. Although the chemical stability of the mutant protein remained largely unchanged, the differential scanning calorimetry (DSC) measurement suggested that its thermal stability was reduced. As examined with transmission electron microscopy, αB-crystallin and its mutant indicated a similar tendency for the amyloid fibril formation under thermochemical stress. Dynamic light scattering (DLS) analysis suggested important changes in the quaternary (oligomeric) structures of the mutant protein as compared with the native protein counterpart. Also, the mutant protein indicated an improved chaperone-like activity under in vitro assessment. In a pH-dependent manner, the side chains of arginine and histidine have different capabilities for establishing hydrogen bonds and electrostatic interaction (salt bridge) and this variation may be sufficient to produce the larger changes that ultimately alter the interaction of this protein with other target proteins. Overall, the pathogenic contribution of this mutation in cardiomyopathy can be explained by its role in quaternary structure/stability alteration of the mutated protein.

The assessment of antidiabetic properties of novel synthetic curcumin analogues: α-amylase and α-glucosidase as the target enzymes.

Diabetes mellitus is a metabolic disorder characterized by high blood glucose levels and instability in carbohydrate metabolism. For treating diabetes, one important therapeutic approach is reducing the postprandial hyperglycemia which can be managed by delaying the absorption of glucose through inhibition of the carbohydrate-hydrolyzing enzymes, α-amylase (α-Amy) and α-glucosidase (α-Gls) in the digestive tract. In this work, a new class of curcumin derivatives incorporating pyrano[2,3-d]pyrimidine heterocycles was synthesized using a multicomponent reaction between curcumin, aldehydes, and barbituric acid. Using UV-Vis spectroscopic method, the synthetic compounds were assessed for their inhibitory properties against α-Amy and α-Gls enzymes. Also, the antioxidant potential of these compounds was measured spectroscopically and compared with Trolox which is known as a gold standard to measure antioxidant capacity. The results of present study suggest that the curcumin derivatives were able to efficiently inhibit both yeast and mammalian α-Gls. In comparison with the antidiabetic medicine acarbose, the synthetic curcumin derivatives were also capable to inhibit more effectively the yeast α-Gls. The partial inhibitory effects of these compounds against pancreatic α-Amy were also important in the terms of avoiding development of the possible gastrointestinal side effects. Moreover, some of the curcumin derivatives indicated stronger antioxidant activity than Trolox. Overall, these synthetic curcumin analogues might be considered as novel molecular templates for development of efficient antidiabetic compounds with promising inhibitory activities against α-Amy and α-Gls enzymes. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40200-020-00685-z.

Synthesis of new curcumin derivatives as influential antidiabetic α-glucosidase and α-amylase inhibitors with anti-oxidant activity.

In this study, a new class of curcumin derivatives was synthesized using a multicomponent reaction containing curcumin, aldehydes, and malononitrile. This new protocol afforded a novel class of 4H-pyran heterocycles incorporating curcumin moiety. The products were obtained in the presence of p-toluenesulfonic acid (PTSA) as a catalyst in ethanol solvent in good to excellent yields. The synthetic compounds indicated a notable inhibitory activity against α-glucosidase (α-Gls) and revealed a weak inhibitory property against α-amylase (α-Amy). Also, these synthetic compounds indicated significant antioxidant activity. The new curcumin derivatives were also discovered to display no significant effect against the growth of two bacterial microflora in the human intestine. A molecular docking study was done to realize the binding interaction of the synthetic curcumin derivatives with the α-Gls enzyme. The results of our study introduced new synthetic curcumin derivatives as potential antidiabetic drugs.

Correction to "Synthesis and Antioxidant Activity Evaluation of Some Novel Aminocarbonitrile Derivatives Incorporating Carbohydrate Moieties".

[This corrects the article DOI: 10.1021/acsomega.8b01124.].

Structure, chaperone-like activity and allergenicity profile of bovine caseins upon peroxynitrite modification: New evidences underlying mastitis pathomechanisms.

Mastitis, an inflammatory reaction frequently develops in response to intra-mammary bacterial infection||, may induce the generation of peroxynitrite (PON)| which is a highly potent reactive oxygen and nitrogen species. Caseins as the intrinsically unfolded proteins seem feasible substrates to react with PON. Therefore, in the current study, structural and functional aspects of both ß-casein (ß-CN) and whole casein fraction (WCF) were evaluated after PON modification, using a variety of techniques. Modification of the bovine caseins with PON results in an important enhancement in the carbonyl, nitrotryptophan, nitrotyrosine and dityrosine content of these proteins|. The results of fluorescence and far UV-CD assessments suggested significant structural alteration of caseins upon PON-modification. The chaperone-like activity of ß-casein was significantly altered after PON modification. The results of scanning electron microscopy suggest that bovine caseins display unique morphological features after treatment with PON. Also, the PON-modified caseins preserved their allergenicity profile and displayed partial resistance against digestion by the pancreatic proteases. Ascorbic acid, an important antioxidant component of milk, was also capable to significantly prevent the PON-induced structural damages in bovine milk caseins. In conclusion, our results suggest that PON may have significant role in the structural and functional alteration of milk caseins. Also, the PON-induced structural damaging effects of caseins might be effectively prevented by a sufficient level of milk antioxidant components particularly by ascorbic acid.

Synthesis and Antioxidant Activity Evaluation of Some Novel Aminocarbonitrile Derivatives Incorporating Carbohydrate Moieties.

In this study, a multicomponent reaction involving carbohydrates, ß-dicarbonyl compounds, and malononitrile was disclosed to synthesize a new class of polyhydroxy compounds incorporating pyrano[2,3-d]pyrimidine, pyrido[2,3-d]pyrimidine and chromene heterocycles under mild conditions. For the synthesis of this class of compounds, glucose, galactose, arabinose, maltose, and lactose were used as aldehyde component in the reaction with barbituric acid and malononitrile to produce pyrano[2,3-d]pyrimidine derivatives. By use of 1,3-cyclohexanedione instead of barbituric acid, chromene derivatives incorporating carbohydrate moieties were obtained. Also, the four-component condensation reaction between d-glucosamine, aldehyde, malononitrile, and barbituric acid was efficiently provided polyhydroxy-substituted pyrido[2,3-d]pyrimidine derivatives. This new combinatorial approach gave a range of carbohydrate-derived heterocycles in good to excellent yields with high potential biological applications. The antioxidant activities were evaluated using 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) antioxidant measuring system, and the data were expressed as Trolox equivalent antioxidant capacity. All of these compounds display significant antioxidant activity. The maximum and minimum antioxidant activities were observed for 4j and 6b, respectively. Our results indicated encouraging perspectives for the improvement and usage of this type of synthetic compounds, indicating significant levels of antioxidant activity.

Evaluation of Structure, Chaperone-Like Activity and Allergenicity of Reduced Glycated Adduct of Bovine ß-casein.

Milk has a potent reducing environment with an important quantity of sugar levels. In the current study ß-casein was glycated in the presence of D-glucose and sodium cyanoborohydride as a reducing agent. Then, the reduced glucitol adduct of ß-casein was used for the structural and functional analyses using different spectroscopic techniques. The results of fluorescence and far ultraviolet circular dichroism assessments suggest important structural alteration upon non-enzymatic glycation of ß-casein. In addition, the chaperone activity, micellization properties and antioxidant activity of this protein were altered upon glucose modification. Also, as a result of reduced glycation, the allergenicity profile of this protein remained largely unchanged. Additional to its energetic and nutritional values, ß-casein has important functional properties. The native structure of this protein is important to perform accurately its biological functions. Non-enzymatic glycation under reducing state was capable to alter both structural and functional aspects of ß-casein. Due to effective reducing environment and significant quantity of reducing sugar of human milk, similar structural and functional alterations are most likely to occur upon reducing glycation of ß-casein in vivo. Also, these changes might be even intensified during chronic hyperglycemia in diabetic mothers.

The anticancer activity and HSA binding properties of the structurally related platinum (II) complexes.

The development of resistance and unwanted harmful interaction with other biomolecules instead of DNA are the major drawbacks for application of platinum (Pt) complexes in cancer chemotherapy. To conquer these problems, much works have been done so far to discover innovative Pt complexes. The objective of the current study was to evaluate the anti cancer activities of a series of four and five-coordinated Pt(II) complexes, having deprotonated 2-phenyl pyridine (abbreviated as C^N), biphosphine moieties, i.e., dppm = bis(diphenylphosphino) methane (Ph(2)PCH(2)PPh(2)) and dppa = bis(diphenylphosphino)amine (Ph(2)PNHPPh(2)), as the non-leaving carrier groups. The growth inhibitory effect of the Pt complexes [Pt(C^N)(dppm)]PF(6): C(1), [Pt(C^N)(dppa)]PF(6): C(2), and [Pt(C^N)I(dppa)]: C(3), toward the cancer cell lines was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. In addition, the florescence quenching experiments of the interaction between human serum albumin (HSA) and the Pt complexes were performed in order to obtain the binding parameters and to evaluate the denaturing properties of these complexes upon binding to the general carrier protein of blood stream. The structure-activity relationship studies reveal that four-coordinated Pt complexes C(1) and C(2) with both significant hydrophobic and charge characteristics, not only exhibit strong antiproliferation activity toward the cancer cell lines, but also they display lower denaturing effect against carrier protein HSA. On the other hand, five-coordinated C(3) complex with the unusual intermolecular NH…Pt hydrogen binding and the intrinsic ability for oligomerization, exhibits poor anticancer activity and strong denaturing property. The current study reveals that the balance between charge and hydrophobicity of the Pt complexes, also their hydrogen binding abilities and coordination mode are important for their anticancer activities. Moreover, this study may suggest C(1) and C(2) as the potential template structures for synthesis of new generation of four-coordinated Pt complexes with strong anticancer activities and weak denaturing effects against proteins.