Introducing a New Model of Sweet Taste Receptor, a Class C G-protein Coupled Receptor (C GPCR)

New Sweet-Tasting Gypenosides from "Jiaogulan" (Gynostemma pentaphyllum) and Their Interactions with the Homology Model of Sweet Taste Receptors

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.

Investigating mechanism of sweetness intensity differences through dynamic analysis of sweetener-T1R2-membrane systems

Knowing the mechanism of action of sweet taste receptors is important for the design of new, healthy sweeteners. However, little is known about the structures and recognition mechanisms of these receptors. 28 sweeteners were assessed by molecular docking, and 8 typical sweeteners were chosen to construct sweetener-T1R2-membrane systems to analyze interactions between receptor and sweeteners. Natural sweeteners with low-intensity sweetness, such as fructose and xylitol, were released from the Venus flytrap domain at ∼30 ns, with displacements greater than 50 Å. In contrast, artificial neotame and advantame bound stably to the receptor, within 5 Å. Van der Waals interactions were significant in high-intensity sweetener systems, imparting an energy difference of over 15 kcal/mol between neotame (artificial sweetener) and fructose (natural). These results provide a deeper understanding of the mechanisms of sweetener function and offer a new direction for the design of sweeteners.

Drinking Non-nutritive Sweetness Solution of Sodium Saccharin or Rebaudioside a for Guinea Pigs: Influence on Histologic Change and Expression of Sweet Taste Receptors in Testis and Epididymis

Saccharin sodium and rebaudioside A are extensively used as non-nutritive sweeteners (NNSs) in daily life. NNSs elicit a multitude of endocrine influences on animals, differing across species and chemically distinct sweeteners, whose exposure induce activation of sweet taste receptors in oral and extra-oral tissues with consequences of metabolic changes. To evaluate the influence of NNSs on histologic change and expression of sweet taste receptors in testis and epididymis of young male guinea pigs, thirty 4-week-old male guinea pigs with body weight 245.73 ± 6.02 g were randomly divided into five groups (n = 6) and received normal water (control group) and equivalent sweetness low dose or high dose of sodium saccharin (L-SS, 1.5 mM or H-SS, 7.5 mM) or rebaudioside A (L-RA, 0.5 mM or H-RA, 2.5 mM) solution for 28 consecutive days. The results showed that the relative testis weight in male guinea pig with age of 56 days represented no significant difference among all groups; in spite of heavier body weight in L-SS and H-RA, NNS contributes no significant influence on serum testosterone and estradiol level. Low-dose 0.5 mM rebaudioside A enhanced testicular and epididymal functions by elevating the expressions of taste receptor 1 subunit 2 (T1R2) and gustducin α-subunit (GNAT3), and high-dose 7.5 mM sodium saccharin exerted adverse morphologic influences on testis and epididymis with no effect on the expression of T1R2, taste receptor 1 subunit 2 (T1R3), and GNAT3. In conclusion, these findings suggest that a high dose of sodium saccharin has potential adverse biologic effects on the testes and epididymis, while rebaudioside A is a potential steroidogenic sweetener for enhancing reproductive functions.

Modeling and simulation in medical sciences: an overview of specific applications based on research experience in EMRI (Endocrinology and Metabolism Research Institute of Tehran University of Medical Sciences)

The concomitant use of various types of models (in silico, in vitro, and in vivo) has been exemplified here within the context of biomedical researches performed in the Endocrinology and Metabolism Research Institute (EMRI) of Tehran University of Medical Sciences. Two main research aeras have been discussed: the search for new small molecules as therapeutics for diabetes and related metabolic conditions, and diseases related to protein aggregation. Due to their multidisciplinary nature, the majority of these studies have needed the collaboration of different specialties. In both cases, a brief overview of the subject is provided through literature examples, and sequential use of these methods is described.

Miracle Berry as a Potential Supplement in the Control of Metabolic Risk Factors in Cancer

The increased incidence of chronic diseases related to altered metabolism has become a social and medical concern worldwide. Cancer is a chronic and multifactorial disease for which, together with genetic factors, environmental factors are crucial. According to the World Health Organization (WHO), up to one third of cancer-related deaths could be prevented by modifying risk factors associated with lifestyle, including diet and exercise. Obesity increases the risk of cancer due to the promotion of low-grade chronic inflammation and systemic metabolic oxidative stress. The effective control of metabolic parameters, for example, controlling glucose, lipid levels, and blood pressure, and maintaining a low grade of chronic inflammation and oxidative stress might represent a specific and mechanistic approach against cancer initiation and progression. Miracle berry (MB) (Synsepalum dulcificum) is an indigenous fruit whose small, ellipsoid, and bright red berries have been described to transform a sour taste into a sweet one. MB is rich in terpenoids, phenolic compounds, and flavonoids, which are responsible for their described antioxidant activities. Moreover, MB has been reported to ameliorate insulin resistance and inhibit cancer cell proliferation and malignant transformation in vitro. Herein, we briefly summarize the current knowledge of MB to provide a scientific basis for its potential use as a supplement in the management of chronic diseases related to altered metabolism, including obesity and insulin resistance, which are well-known risk factors in cancer. First, we introduce cancer as a metabolic disease, highlighting the impact of systemic metabolic alterations, such as obesity and insulin resistance, in cancer initiation and progression. Next, as oxidative stress is closely associated with metabolic stress, we also evaluate the effect of phytochemicals in managing oxidative stress and its relationship with cancer. Finally, we summarize the main biological activities described for MB-derived extracts with a special focus on the ability of miraculin to transform a sour taste into a sweet one through its interaction with the sweet taste receptors. The identification of sweet taste receptors at the gastrointestinal level, with effects on the secretion of enterohormones, may provide an additional tool for managing chronic diseases, including cancer.

An in-silico layer-by-layer adsorption study of the interaction between Rebaudioside A and the T1R2 human sweet taste receptor: modelling and biosensing perspectives

The human sweet taste receptor (T1R2) monomer-a member of the G-protein coupled receptor family that detects a wide variety of chemically and structurally diverse sweet tasting molecules, is known to pose a significant threat to human health. Protein that lack crystal structure is a challenge in structure-based protein design. This study focused on the interaction of the T1R2 monomer with rebaudioside A (Reb-A), a steviol glycoside with potential use as a natural sweetener using in-silico and biosensing methods. Herein, homology modelling, docking studies, and molecular dynamics simulations were applied to elucidate the interaction between Reb-A and the T1R2 monomer. In addition, the electrochemical sensing of the immobilised T1R2-Reb-A complex with zinc oxide nanoparticles (ZnONPs) and graphene oxide (GO) were assessed by testing the performance of multiwalled carbon nanotube (MWCNT) as an adsorbent experimentally. Results indicate a strong interaction between Reb-A and the T1R2 receptor, revealing the stabilizing interaction of the amino acids with the Reb-A by hydrogen bonds with the hydroxyl groups of the glucose moieties, along with a significant amount of hydrophobic interactions. Moreover, the presence of the MWCNT as an anchor confirms the adsorption strength of the T1R2-Reb-A complex onto the GO nanocomposite and supported with electrochemical measurements. Overall, this study could serve as a cornerstone in the development of electrochemical immunosensor for the detection of Reb-A, with applications in the food industry.