Search

Copyright of Journal of Chinese Institute of Food Science & Technology / Zhongguo Shipin Xuebao is the property of Journal of Chinese Institute of Food Science & Technology Periodical Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The acute liver disease is involved in aberrant release of high-mobility group box 1 (HMGB1). Glycyrrhizin (GL), a traditional Chinese medicine for liver disease, binds to HMGB1, thereby inhibits tissue injury. However the mode of action of GL for chronic liver disease remains unclear.We investigated the effects of glycyrrhizin (GL) and its derivatives on liver differentiation using human iPS cells by using a flow cytometric analysis.GL promoted hepatic differentiation at the hepatoblast formation stage. The GL derivatives, 3-O-mono-glucuronyl 18β-glycyrrhetinic acid (Mono) and 3-O-[glucosyl (1 → 2)-glucuronyl] 18β-glycyrrhetinic acid increased AFP+ cell counts and albumin+ cell counts. Glucuronate conjugation seemed to be a requirement for hepatic differentiation. Mono exhibited the most significant hepatic differentiation effect.We evaluated the effects of (±)-2-(2,4-dichlorophenoxy) propionic acid (DP), a T1R3 antagonist, and sucralose, a T1R3 agonist, on hepatic differentiation, and found that DP suppressed Mono-induced hepatic differentiation, while sucralose promoted hepatic differentiation. Thus, GL promoted hepatic differentiation via T1R3 signaling. In addition, Mono increased β-catenin+ cell count and decreased Hes5+ cell count suggesting the involvement of Wnt and Notch signaling in GL-induced hepatic differentiation.In conclusion, GL exerted a hepatic differentiation effect via sweet receptor (T1R3), canonical Wnt, and Notch signaling.

Sweet proteins are the sweetest natural molecules. This aspect prompted several proposals for their use as food additives, mainly because the amounts to be added to food would be very small and safe for people suffering from sucrose-linked diseases. During studies of sweet proteins as food additives we found that their sweetness is affected by water salinity, while there is no influence on protein’s structure. Parallel tasting of small size sweeteners revealed no influence of the water quality. This result is explained by the interference of ionic strength with the mechanism of action of sweet proteins and provides an experimental validation of the wedge model for the interaction of proteins with the sweet receptor.

Gynostemma pentaphyllum has been used as an herbal tea, vegetable, and dietary supplement for hundreds of years in East Asia. The sweet variety, grown in large areas in Fujian Province, China, is an essential source of "Jiaogulan" herbal tea. However, its sweet components are unknown. To investigate the sweet constituents of Fujian "Jiaogulan" and discover new natural high-potency sweeteners, phytochemical and sensory evaluations were combined to obtain 15 saponins, of which 11 ( 1 - 11 ) were sweet-tasting, including 2 new ones with sweetness intensities 20-200 times higher than that of sucrose, and four ( 12 - 15 ) were bitter-tasting. Their structures were elucidated using spectroscopic methods (NMR, MS, IR, UV), hydrolysis, and comparison with literature data. The contents of the 15 saponins were quantitatively analyzed using UPLC-MS/MS in multiple reaction monitoring mode. The contents of 1 and 2 sweet-tasting gypenosides were 9.913 ± 1.735 and 35.852 ± 1.739 mg/kg, respectively. The content of the sweetest compound ( 6 ) was 124.969 ± 0.961 mg/kg. Additionally, compound 4 was the most abundant sweet component (422.530 ± 3.702 mg/kg). Furthermore, molecular docking results suggested interactions of sweet saponins with sweet taste receptors. In general, this study revealed the material basis of the Fujian "Jiaogulan" taste.

The effects of saccharin, as a type of sweetener additive, on the metabolism and development of mammals are still controversial. Our previous research revealed that saccharin sodium (SS) promoted the feed intake and growth of guinea pigs. In this experiment, we used the guinea pig model to study the physiological effect of SS in the microbiota-gut-hypothalamus axis. Adding 1.5 mM SS to drinking water increased the serum level of glucose, followed by the improvement in the morphology and barrier function of the ileal villus, such as SS supplementation which increased the villus height and villus height/crypt depth ratio. Saccharin sodium (SS) treatment activated the sweet receptor signaling in the ileum and altered GHRP hormone secretion. In the hypothalamus of SS and control (CN) group, RNA-seq identified 1370 differently expressed genes (796 upregulated, 574 downregulated), enriching into the taste signaling transduction, and neuroactive ligand–receptor interaction. LEfSe analysis suggested that Lactobacillaceae-Lactobacillus was the microbe with significantly increased abundance of ileum microorganisms in the SS-treated group, while Brevinema-Andersonii and Erysipelotrichaceae-Ilebacterium were the microbes with significantly increased abundance of the control. Furthermore, SS treatment significantly enhanced the functions of chemoheterotrophy and fermentation of ileal microflora compared to the CN group. Accordingly, SS treatment increased levels of lactic acid and short-chain fatty acids (acetic acid, propionic acid and N-valeric acid) in the ileal digesta. In summary, drinking water with 1.5 mM SS activated sweet receptor signaling in the gut and altered GHRP hormone secretion, followed by the taste signaling transduction in the hypothalamus.

Abstract The sweet protein monellin has an intensely sweet potency but limited stability. We have identified a double-sites mutant (E2N/E23A) of the single-chain monellin (MNEI) with both improved sweetness (about 3-fold) and thermostability (10 °C). However, the structural basis of its superior properties remains elusive until now. Herein we report its crystal structure at a resolution 1.90 Å. Similar to the wild-type, E2N/E23A adopts a wedge-shaped structure consisting of a five-strand β -sheet partially "wrapped" around an α -helix. However, distinguishing parts were present in the loops region, including a remarkable conformation shift from β -strand to loop around residue R39. Molecular docking revealed the persistence of conserved protein-receptor interface and formation of new intermolecular ionic bonds in the E2N/E23A-receptor complex involving the taste-active residue R39 of the sweet protein, which could account for its significant improvement of sweetness. On the other hand, a rearrangement of intramolecular interaction network including the C-H ... π bond between A23 and F89 that led to enhanced hydrophobicity in the protein core, could be correlated with its improved thermostability. Furthermore, two new sweeter mutants of MNEI were created. These findings highlight the critical roles of key sweetness determinant residue R39 and hydrophobicity at the protein core for the sweetness and thermostability of the protein, respectively, which thus provide a deeper insight for understanding the structure-function relationship of the sweet protein as well as guidance for rational design of this unique biomacromolecule. Highlights • The crystal structure of a unique sweet protein monellin mutant E2N/E23A was solved. • Intermolecular ionic bonds involving residue R39 account for the improved sweetness. • Intramolecular interaction and hydrophobicity at protein core mediate the stability. [ABSTRACT FROM AUTHOR]

Cystatins are small proteins, typically composed of 100–120 amino acids, which together with similar proteins devoid of inhibitory properties, belong to a cystatin ‘superfamily’. Cystatins can do more than just inhibit proteases: two important aspects described here are aggregation properties linked to misfolding diseases and the unique ability of monellin, a plant cystatin, to elicit sweet taste. The explanation of the puzzling phenomenon of ‘sweet proteins’ required an in-depth structural study of monellin, also regarding the causes of the high thermal stability of its single chain structure. The detailed mechanisms by which cystatins aggregate could be relevant in the study of misfolding diseases involving cystatins. They are reviewed here with emphasis on 3D domain swapping, typical of aggregating cystatins. While studying monellin, we noticed that it aggregates in a conventional way, probably through the cross-β spine mechanism. However, several cystatins derived from oryzacystatin_I to emulate the taste behavior of monellin aggregate via different mechanisms.

Recent studies indicate that the processes mediated by the (T1R2/T1R3) glucose/sugar receptor of gustatory cells in the tongue, and hormones like leptin and ghrelin contribute to the regulation of glucose homeostasis. Altered plasma levels of leptin and ghrelin are associated with obesity both in humans and rodents. In the present study, we evaluated the ultrastructure of the mucosa, and the expression of molecules implicated in the regulation of glucose homeostasis (GLUT2, SGLT1, T1R3, ghrelin and its receptor) in the trachea of an animal model of obesity (Zucker rats). We found that the tracheal epithelium of obese animals was characterized by the presence of poorly differentiated cells. Ciliated and secretory cells were the cell lineages with greatest loss of differentiation. Severe epithelial alterations were associated with marked deposit of extracellular matrix in the lamina propria. The expression pattern of GLUT2 and SGLT1 glucose transporters was similar in the trachea of both the Zucker rat genotypes, whereas that of T1R3 was reduced in ciliated cells of obese rats. A different immunolocalization for ghrelin was also found in the trachea of obese rats. In conclusion, the tracheal morphological alterations in obese animals seem to compromise the expression of molecules involved in the homeostasis of glucose.

ABSTRACT L-Aspartyl-L-phenylalanine methyl ester, better known as aspartame, is not only one of the most used artificial sweeteners, but also a very interesting molecule with respect to the correlation between molecular structure and taste. The extreme conformational flexibility of this dipeptide posed a huge difficulty when researchers tried to use it as a lead compound to design new sweeteners. In particular, it was difficult to take advantage of its molecular model as a mold to infer the shape of the, then unknown, active site of the sweet taste receptor. Here, we follow the story of the 3D structural aspects of aspartame from early conformational studies to recent docking into homology models of the receptor. © 2016 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 376-384, 2016. [ABSTRACT FROM AUTHOR]

5-Nitro-2-propoxyaniline is one of the strongest artificial sweeteners. However, little is known about the detailed relationship of the structure and biological activity between 5-nitro-2-propoxyaniline and its sweet receptor. Photoaffinity labeling is a useful method for revealing interactions of a small bioactive compound with molecules. Therefore, we synthesized photoreactive 2-propoxyaniline derivatives as useful tools for revealing the interactions by photoaffinity labeling. [ABSTRACT FROM AUTHOR]

We report the total synthesis of NP-011694, a previously unreported fungal fermentation product from Analyticon Gmbh. The convergent synthesis employs Turbo Grignard and lithiation strategies, along with novel conditions for the simultaneous removal of multiple phenolic MOM groups. [ABSTRACT FROM AUTHOR]

Abstract: Thaumatin, a sweet-tasting plant protein, elicits a sweet taste sensation at 50 nM in humans but not rodents. Although it was shown that the cysteine-rich domain (CRD) of human T1R3 (hT1R3) is important for the response to thaumatin, the amino acid residues within CRD critical for response are still unknown. A comparison of the amino acid sequence (69 amino acid residues) of CRD between hT1R3 and mouse T1R3 (mT1R3) revealed sixteen amino acids that differ. In the present study, we converted each of these sixteen amino acids in hT1R3 to their mouse counterpart and examined the response to thaumatin and sucralose using a cell-based assay. No significant decrease in the response to sucralose was seen among any of the sixteen mutants. However, five mutants (Q504K, A537T, R556P, S559P, and R560K) exhibited a significantly diminished response to thaumatin. The five critical residues involved in the response to thaumatin were dispersed in the CRD of hT1R3 and widely distributed when compared to brazzein. The unique intense sweet-taste of thaumatin might be attributed to the different receptor activation mechanism compared to the small molecule sweetener sucralose. [Copyright &y& Elsevier]

Abstract: Thaumatin is an intensely sweet-tasting protein perceived by humans but not rodents. Its threshold value of sweetness in humans is 50nM, the lowest of any sweet-tasting protein. In the present study, the sites where sweet receptors interact with thaumatin were investigated using human embryonic kidney 293 (HEK293) cells expressing the sweet receptors T1R2–T1R3. Chimeric human– mouse sweet receptors were constructed and their responses to sweeteners were investigated. The human (h) T1R2– mouse (m) T1R3 combination responded to sucralose but not to thaumatin, clearly indicating that a T1R3 subunit from humans is necessary for the interaction with thaumatin. Furthermore, results obtained from using chimeric T1R3s showed that the cysteine-rich domain (CRD) of human T1R3 is important for the interaction with thaumatin. The CRD of T1R3 would be a prominent target for designing new sweeteners. [Copyright &y& Elsevier]

Abstract: The sweet receptor is a member of the G-protein coupled receptor family C that detects a wide variety of chemically and structurally diverse sweet-tasting molecules. We recently used saturation transfer difference spectroscopy (STD) to monitor the direct binding of a set of sweet agonists and antagonists to the human taste receptor in membranes prepared from human embryonic kidney (HEK293) cells transfected with and expressing the sweet receptor [F.M. Assadi-Porter, M. Tonelli, E. Maillet, K. Hallenga, O. Benard, M. Max, J.L. Markley, J. Am. Chem. Soc. 130 (2008) 7212–7213]. Here we review this work and related studies, discuss the procedures involved, and expand on their potential for identifying specific binding interactions of ligands to the membrane spanning and extracellular regions of the full heterodimeric sweet taste receptor. Whereas activity assays are unable to distinguish mutations that alter ligand-binding sites from those that alter signal transduction downstream of the binding site, STD NMR now allows us to make this distinction. [Copyright &y& Elsevier]

The extent to which taste receptor specificity correlates with, or even predicts, diet choice is not known. We recently reported that the insensitivity to sweeteners shown by species of Felidae can be explained by their lacking of a functional Tas1r2 gene. To broaden our understanding of the relationship between the structure of the sweet receptors and preference for sugars and artificial sweeteners, we measured responses to 12 sweeteners in 6 species of Carnivora and sequenced the coding regions of Tas1r2 in these same or closely related species. The lion showed no preference for any of the 12 sweet compounds tested, and it possesses the pseudogenized Tas1r2. All other species preferred some of the natural sugars, and their Tas1r2 sequences, having complete open reading frames, predict functional sweet receptors. in addition to preferring natural sugars, the lesser panda also preferred 3 (neotame, sucralose, and aspartame) of the 6 artificial sweeteners. Heretofore, it had been reported that among vertebrates, only Old World simians could taste aspartame. The observation that the lesser panda highly preferred aspartame could be an example of evolutionary convergence in the identification of sweet stimuli. [ABSTRACT FROM AUTHOR]

Abstract: The crystal structure of a sweet protein Mabinlin II (Mab II) isolated from the mature seeds of Capparis masaikai Levl. grown in Southern China has been determined at 1.7Å resolution by the SIRAS method. The Mab II 3D structure features in an “all alpha” fold mode consisting of A- and B-chains crosslinked by four disulfide bridges, which is distinct from all known sweet protein structures. The Mabinlin II molecule shows an amphiphilic surface, a cationic face (Face A) and a neutral face (Face B). A unique structural motif consisting of B54–B64 was found in Face B, which adopts a special sequence, NL–P–NI–C–NI–P–NI, featuring four [Asn-Leu/Ile] units connected by three conformational-constrained residues, thus is called the [NL/I] tetralet motif. The experiments for testing the possible interactions of separated A-chain and B-chain and the native Mabinlin II to the sweet-taste receptor were performed through the calcium imaging experiments with the HEK293E cells coexpressed hT1R2/T1R3. The result shows that hT1R2/T1R3 responds to both the integrated Mabinlin II and the individual B-chain in the same scale, but not to A-chain. The sweetness evaluation further identified that the separated B-chain can elicit the sweetness alone, but A-chain does not. All data in combination revealed that the sweet protein Mabinlin II can interact with the sweet-taste receptor hT1R2/T1R3 to elicit its sweet taste, and the B-chain with a unique [NL/I] tetralet motif is the essential structural element for the interaction with sweet-taste receptor to elicit the sweetness, while the A-chain may play a role in gaining a long aftertaste for the integrate Mabinlin II. The findings reported in this paper will be advantage for understanding the diversity of sweet proteins and engineering research for development of a unique sweetener for the food and agriculture based on the Mabinlin II structure as a native model. [Copyright &y& Elsevier]

Sweet tasting proteins interact with the same receptor that binds small molecular weight sweeteners, the T1R2–T1R3 G-protein coupled receptor, but the key groups on the protein surface responsible for the biological activity have not yet been identified. I propose that sweet proteins, contrary to small ligands, do not bind to the ‘glutamate-like’ pocket but stabilize the free form II of the T1R2–T1R3 receptor by attachment to a secondary binding site. Docking of brazzein, monellin and thaumatin with a model of the T1R2–T1R3 sweet taste receptor shows that the most likely complexes can indeed stabilize the active form of the receptor. [Copyright &y& Elsevier]

Simple Summary: Saccharin sodium (SS) is one of the commonly used artificial sweeteners (AS) in the food industry, but the mechanisms mediating the physiological effects of sweeteners in the gut-brain axis is still unclear. The aim of this study was to explore the regulatory effect of SS on the microbiota-gut-hypothalamus axis on guinea pigs. We found that SS treatment may alter the growth and glucose metabolism of guinea pigs by activating sweet receptor signaling in the gut and growth hormone-releasing peptide (GHRP) hormone secretion. Besides, SS treatment increased the abundance of Firmicutes and Lactobacillasceae-Lactobacillus in the ileum, and subsequently increased levels of lactic acid and short-chain fatty acids (SCFAs). Adding 1.5 mM SS to drinking water alters the growth of guinea pigs by regulating the microbiota-hypothalamus-gut axis. This conclusion has theoretical implications for the comprehensive assessment of the biological effects of appropriate SS in the food industry. The effects of saccharin, as a type of sweetener additive, on the metabolism and development of mammals are still controversial. Our previous research revealed that saccharin sodium (SS) promoted the feed intake and growth of guinea pigs. In this experiment, we used the guinea pig model to study the physiological effect of SS in the microbiota-gut-hypothalamus axis. Adding 1.5 mM SS to drinking water increased the serum level of glucose, followed by the improvement in the morphology and barrier function of the ileal villus, such as SS supplementation which increased the villus height and villus height/crypt depth ratio. Saccharin sodium (SS) treatment activated the sweet receptor signaling in the ileum and altered GHRP hormone secretion. In the hypothalamus of SS and control (CN) group, RNA-seq identified 1370 differently expressed genes (796 upregulated, 574 downregulated), enriching into the taste signaling transduction, and neuroactive ligand–receptor interaction. LEfSe analysis suggested that Lactobacillaceae-Lactobacillus was the microbe with significantly increased abundance of ileum microorganisms in the SS-treated group, while Brevinema-Andersonii and Erysipelotrichaceae-Ilebacterium were the microbes with significantly increased abundance of the control. Furthermore, SS treatment significantly enhanced the functions of chemoheterotrophy and fermentation of ileal microflora compared to the CN group. Accordingly, SS treatment increased levels of lactic acid and short-chain fatty acids (acetic acid, propionic acid and N-valeric acid) in the ileal digesta. In summary, drinking water with 1.5 mM SS activated sweet receptor signaling in the gut and altered GHRP hormone secretion, followed by the taste signaling transduction in the hypothalamus. [ABSTRACT FROM AUTHOR]

The article focuses on the exception of an ability of a cat to taste sweet stimuli and identifies the DNA sequences and examined the structures of the genes, Tas1r2 and Tas1r3, of domestic animals that identifies the sweet receptor heteromer TIR2/TIR3 in other animals. Cat circumvallate and fungiform papillae were exposed to polyclonal antibodies against T1R3 and T1R2. It shows that T1R3 was present in the taste buds of circumvallate and fungiform papillae. It was concluded that cats fail to respond to sweet stimuli and it provides on the development of carnivorous behavior in Felidae.

Sweet taste is mediated by a dimeric receptor composed of two distinct subunits, T1R2 and T1R3, whereas the T1R1/T1R3 receptor is involved in umami taste perception. The T1R1, T1R2, and T1R3 subunits are members of the small family of class C G protein-coupled receptors (GPCRs). The members of this family are characterized by a large N-terminal domain (NTD), which is structurally similar to bacterial periplasmic-binding proteins and contains the primary ligand-binding site. In a recent study, we described a strategy to produce a functional dimeric human T1R3-NTD. Although the protein was expressed as inclusion bodies (IBs) using the Escherichia coli system, the conditions for the refolding of functional hT1R3-NTD were determined using a fractional factorial screen coupled to a binding assay. Here, we report that this refolding strategy can be used to produce T1R1- and T1R2-NTDs in large quantities. We also discuss that our findings could be more generally applicable to other class C GPCR-NTDs, including the γ-aminobutyric acid type B receptor (GABABR), the extracellular calcium-sensing receptor (CaSR) and the large family of pheromone (V2R) orphan receptors.