Beneficial effects of β-sitosterol on type 1 cholecystokinin receptor dysfunction induced by elevated membrane cholesterol

Cholesterol-dependent dynamic changes in the conformation of the type 1 cholecystokinin receptor affect ligand binding and G protein coupling

Development of optimal therapeutics for disease states that can be associated with increased membrane cholesterol requires better molecular understanding of lipid modulation of the drug target. Type 1 cholecystokinin receptor (CCK1R) agonist actions are affected by increased membrane cholesterol, enhancing ligand binding and reducing calcium signaling, while agonist actions of the closely related CCK2R are not. In this work, we identified a set of chimeric human CCK1R/CCK2R mutations that exchange the cholesterol sensitivity of these 2 receptors, providing powerful tools when expressed in CHO and HEK-293 model cell lines to explore mechanisms. Static, low energy, high-resolution structures of the mutant CCK1R constructs, stabilized in complex with G protein, were not substantially different, suggesting that alterations to receptor dynamics were key to altered function. We reveal that cholesterol-dependent dynamic changes in the conformation of the helical bundle of CCK receptors affects both ligand binding at the extracellular surface and G protein coupling at the cytosolic surface, as well as their interrelationships involved in stimulus-response coupling. This provides an ideal setting for potential allosteric modulators to correct the negative impact of membrane cholesterol on CCK1R.

Unveiling the molecular mechanisms: dietary phytosterols as guardians against cardiovascular diseases

Until recently, the main pharmaceuticals used to control cholesterol and prevent cardiovascular disease (CVD) were statin-related drugs, known for their historical side effects. Therefore, there is growing interest in exploring alternatives, such as nutritional and dietary components, that could play a central role in CVD prevention. This review aims to provide a comprehensive understanding of how natural phytosterols found in various diets combat CVDs. We begin with a description of the overall approach, then we explore in detail the different direct and indirect mechanisms that contribute to reducing cardiovascular incidents. Phytosterols, including stigmasterol, β-sitosterol, ergosterol, and fucosterol, emerge as promising molecules within nutritional systems for protection against CVDs due to their beneficial effects at different levels through direct or indirect cellular, subcellular, and molecular mechanisms. Specifically, the mentioned phytosterols exhibit the ability to diminish the generation of various radicals, including hydroperoxides and hydrogen peroxide. They also promote the activation of antioxidant enzymes such as superoxide dismutase, catalase, and glutathione, while inhibiting lipid peroxidation through the activation of Nrf2 and Nrf2/heme oxygenase-1 (HO-1) signaling pathways. Additionally, they demonstrate a significant inhibitory capacity in the generation of pro-inflammatory cytokines, thus playing a crucial role in regulating the inflammatory/immune response by inhibiting the expression of proteins involved in cellular signaling pathways such as JAK3/STAT3 and NF-κB. Moreover, phytosterols play a key role in reducing cholesterol absorption and improving the lipid profile. These compounds can be used as dietary supplements or included in specific diets to aid control cholesterol levels, particularly in individuals suffering from hypercholesterolemia.

Mechanism of Yixishu lotion in the treatment of vaginitis based on network pharmacology combined with experimental validation: an experimental research study

Objective

Yixishu lotion (YXSL) originates from the summary of traditional Chinese medicine clinical experience and constantly improves in practice in clinical validation of the exact efficacy of traditional Chinese medicine prescription. To explore the mechanism of YXSL in treating vaginitis and the potential mechanisms based on network pharmacology and experimental verification.

Methods

The active components and drug-related targets of YXSL were retrieved from the TCMSP (Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform) database, and the target was predicted by the UniProt database. Searching for genes related to 'vaginitis' disease in the GeneCards database, a total of 2581 drug targets were obtained. The interaction between proteins (PPI - protein-protein interaction) relationship was obtained by STRING database and visualized by Cytoscape software. Finally, the 'Bioconductor' installation package in R software was used to analyze the GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways of the target.

Results

In this study, by the method of network pharmacology, the key active components of YXSL were flavonoids such as quercetin, apigenin, kaempferol, luteolin, β-sitosterol; the main core proteins included MAPK14, TP53, FGF2, ESR1, MAPK3, MAPK1, VEGFA, JUN, IL-6, and the KEGG pathway was mainly involved in MAPK pathway, Th17 pathway, Malaria, TNF pathway, and other signaling pathways. Animal experiments showed that the clinical symptoms and vaginal tissue lesions of the YXSL group and the fluconazole group were improved, and the levels of TNF-α (tumor necrosis factor alpha), IL-6 (interleukin-6), MDA (malondialdehyde), SOD (superoxide dismutase), IL-4, and IFN-γ (interferon-γ) in vaginal tissue and serum were better than the model group.

Conclusion

YXSL may achieve its therapeutic effect on vaginitis by reducing the inflammatory response, improving oxidative stress response, and improving body immunity, and it provides a theoretical basis for further research on its pharmacodynamic material basis and mechanism of action.

Bioactive components, pharmacological effects, and drug development of traditional herbal medicine Rubus chingii Hu (Fu-Pen-Zi)

Rubus chingii Hu (Chinese Raspberry), known as Fu-Pen-Zi in Chinese, a woody perennial plant of the genus Rubus in the Rosaceae family, has specific nutritional and medicinal values, which is considered food-medicine herb in China for thousands of years to treat impotence, premature ejaculation, enuresis, frequent urination, and other diseases. This review aims to summarize recent advances in the bioactive components, pharmacological effects, and drug development and utilization of Rubus chingii Hu, hoping to provide useful support for its further research and clinical application. The bioactive components in Rubus chingii Hu contain mainly terpenoids, flavonoids, alkaloids, phenolic acids, polysaccharides, and steroids. The main pharmacological effects are their anti-oxidant, anti-inflammatory, and anti-tumor capacity on human health. Rubus chingii Hu is a very valuable food-medicine herb. The development of Rubus chingii Hu-related drugs is relatively single, which is limited to traditional Chinese medicine and prescriptions. Therefore, it is vital to pay interest to Rubus chingii Hu and its bioactive components in the future and extend its scientific application.

β-sitosterol inhibits trimethylamine production by regulating the gut microbiota and attenuates atherosclerosis in ApoE-/- mice

The intestinal microbial metabolite trimethylamine (TMA), which is activated by flavin monooxygenase (FMO) to produce trimethylamine-N-oxide (TMAO), has been implicated in the pathogenesis of atherosclerosis (AS), leading to the development of therapeutic strategies for AS. This study aimed to investigate whether β-sitosterol can inhibit TMA production in ApoE^-/- mice by reshaping the gut microbial structure. 16S rRNA sequencing of the gut microbiota showed that β-sitosterol has beneficial effects on intestinal flora function, especially the inhibition of bacteria genera that contain the gene cholintrimethylamine lyase, which is responsible for the major pathway for TMA production. In parallel, β-sitosterol effectively reduced the TMA, FMO3, and TMAO levels while ameliorating the atherosclerotic plaques of AS mice. Moreover, β-sitosterol could alleviate cholesterol metabolism and the inflammatory response, and improve the antioxidant defense capacity. These studies offer new insights into the mechanisms responsible for the antiatherosclerotic effects of β-sitosterol, which targets the microbiota-metabolism-immunity axis as a possible therapy for AS.

Gender differences in the relationships between dietary phytosterols intake and prevalence of obesity in Chinese population

To investigate the associations between different phytosterols (PSs) intake and subtype of obesity in Chinese. Total 6073 adults aged ≥18 years was enrolled from China. General characteristics were completed by the validated dietary questionnaire. For total phytosterols intake, comparing Q4 with Q1 was inversely associated with the risks of overweight [odds ratio (OR) 95% confidence interval (CI), 0.82 (0.69, 0.96), p < .05]. The intake of stigmasterol, β-sitosterol, β-sitostanol and campestanol were associated with the lower risks of obesity, whereas no significant correlationss were found between campesterol intake and any subtype of obesity in the multivariable-adjusted model. Interestingly, the stigmasterol intake was inversely related with the prevalence of central obesity in female, while the β-sitostanol intake was found in male [OR 95% CI in Q3 of 0.78 (0.60-0.99) and 0.71 (0.56-0.91), respectively; p < .05]. The multiple linear regression models showed that fruits, vegetable-oil, nuts and seeds may be important diet sources of PSs. The intake of total PSs, β-sitosterol, stigmasterol, β-sitostanol and campestanol were inversely associated with the prevalence of obesity. Moreover, the lower obesity risk for total PSs and PSs subgroups differed for the gender. The firm results deserve to be further verified in cohort studies.

Structural and functional analysis of tomato sterol C22 desaturase

BACKGROUND

Sterols are structural and functional components of eukaryotic cell membranes. Plants produce a complex mixture of sterols, among which β-sitosterol, stigmasterol, campesterol, and cholesterol in some Solanaceae, are the most abundant species. Many reports have shown that the stigmasterol to β-sitosterol ratio changes during plant development and in response to stresses, suggesting that it may play a role in the regulation of these processes. In tomato (Solanum lycopersicum), changes in the stigmasterol to β-sitosterol ratio correlate with the induction of the only gene encoding sterol C22-desaturase (C22DES), the enzyme specifically involved in the conversion of β-sitosterol to stigmasterol. However, despite the biological interest of this enzyme, there is still a lack of knowledge about several relevant aspects related to its structure and function.

RESULTS

In this study we report the subcellular localization of tomato C22DES in the endoplasmic reticulum (ER) based on confocal fluorescence microscopy and cell fractionation analyses. Modeling studies have also revealed that C22DES consists of two well-differentiated domains: a single N-terminal transmembrane-helix domain (TMH) anchored in the ER-membrane and a globular (or catalytic) domain that is oriented towards the cytosol. Although TMH is sufficient for the targeting and retention of the enzyme in the ER, the globular domain may also interact and be retained in the ER in the absence of the N-terminal transmembrane domain. The observation that a truncated version of C22DES lacking the TMH is enzymatically inactive revealed that the N-terminal membrane domain is essential for enzyme activity. The in silico analysis of the TMH region of plant C22DES revealed several structural features that could be involved in substrate recognition and binding.

CONCLUSIONS

Overall, this study contributes to expand the current knowledge on the structure and function of plant C22DES and to unveil novel aspects related to plant sterol metabolism.

Roles of Cholecystokinin in the Nutritional Continuum. Physiology and Potential Therapeutics

Cholecystokinin is a gastrointestinal peptide hormone with important roles in metabolic physiology and the maintenance of normal nutritional status, as well as potential roles in the prevention and management of obesity, currently one of the dominant causes of direct or indirect morbidity and mortality. In this review, we discuss the roles of this hormone and its receptors in maintaining nutritional homeostasis, with a particular focus on appetite control. Targeting this action led to the development of full agonists of the type 1 cholecystokinin receptor that have so far failed in clinical trials for obesity. The possible reasons for clinical failure are discussed, along with alternative pharmacologic strategies to target this receptor for prevention and management of obesity, including development of biased agonists and allosteric modulators. Cellular cholesterol is a natural modulator of the type 1 cholecystokinin receptor, with elevated levels disrupting normal stimulus-activity coupling. The molecular basis for this is discussed, along with strategies to overcome this challenge with a corrective positive allosteric modulator. There remains substantial scope for development of drugs to target the type 1 cholecystokinin receptor with these new pharmacologic strategies and such drugs may provide new approaches for treatment of obesity.

Functional marriage in plasma membrane: Critical cholesterol level-optimal protein activity

In physiology, homeostasis refers to the condition where a system exhibits an optimum functional level. In contrast, any variation from this optimum is considered as a dysfunctional or pathological state. In this review, we address the proposal that a critical cholesterol level in the plasma membrane is required for the proper functioning of transmembrane proteins. Thus, membrane cholesterol depletion or enrichment produces a loss or gain of direct cholesterol-protein interaction and/or changes in the physical properties of the plasma membrane, which affect the basal or optimum activity of transmembrane proteins. Whether or not this functional switching is a generalized mechanism exhibited for all transmembrane proteins, or if it works just for an exclusive group of them, is an open question and an attractive subject to explore at a basic, pharmacological and clinical level.

Sapucaia nut (Lecythis pisonis Cambess) and its by-products: A promising and underutilized source of bioactive compounds. Part I: Nutritional composition and lipid profile

The nutritional composition of the sapucaia nut, cake and shell, the nut and cake minerals content and the lipid profile of the nut oil (fatty acids, tocopherols, phytosterols and triacylglycerols) were determined. The nuts and cake exhibited a high content of lipid (47.9 to 60.8 mg 100 g^-1), protein (15.8 to 19.5 mg 100 g^-1), dietary fiber (16.5 to 22.6 mg 100 g^-1) and provided an excellent source of selenium (26.4 to 46.94 μg g^-1). The oil contained a high amount of unsaturated fatty acids (39.7 to 45.4% of oleic and 32.2 to 46.6% of linoleic acids) and presented a high Oxidative Stability Index (8.57-12.95 h) indicating the presence of antioxidant compounds in the oil. The major triacylglycerols in the sapucaia oil were LLO, PLO, LOO, POO, OOO, PLL and LLL. The main bioactive lipids identified in the oil were γ-tocopherol (19.2 to 28.5 mg 100 g^-1) and β-sitosterol (92.8 to 194 mg 100 g^-1). The results showed that the sapucaia nut and its by-products are a promising natural source of bioactive and nutritional compounds and when present in the diet can contribute to the maintenance of human health. In addition, the nut and by-product represents a promising raw material for the food industry.

Changes in the plasma membrane in metabolic disease: impact of the membrane environment on G protein-coupled receptor structure and function

Drug development targeting GPCRs often utilizes model heterologous cell expression systems, reflecting an implicit assumption that the membrane environment has little functional impact on these receptors or on their responsiveness to drugs. However, much recent data have illustrated that membrane components can have an important functional impact on intrinsic membrane proteins. This review is directed toward gaining a better understanding of the structure of the plasma membrane in health and disease, and how this organelle can influence GPCR structure, function and regulation. It is important to recognize that the membrane provides a potential mode of lateral allosteric regulation of GPCRs and can affect the effectiveness of drugs and their biological responses in various disease states, which can even vary among individuals across the population. The type 1 cholecystokinin receptor is reviewed as an exemplar of a class A GPCR that is affected in this way by changes in the plasma membrane.

LINKED ARTICLES

This article is part of a themed section on Molecular Pharmacology of GPCRs. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.21/issuetoc.

Cholecystokinin responsiveness varies across the population dependent on metabolic phenotype

Background: Cholecystokinin (CCK) is an important satiety factor, acting at type 1 receptors (CCK1Rs) on vagal afferent neurons; however, CCK agonists have failed clinical trials for obesity. We postulated that CCK1R function might be defective in such patients due to abnormal membrane composition, such as that observed in cholesterol gallstone disease.Objective: Due to the challenges in directly studying CCK1Rs relevant to appetite control, our goal was to develop and apply a method to determine the impact of a patient's own cellular environment on CCK stimulus-activity coupling and to determine whether CCK sensitivity correlated with the metabolic phenotype of a high-risk population.Design: Wild-type CCK1Rs were expressed on leukocytes from 112 Hispanic patients by using adenoviral transduction and 24-h culture, with quantitation of cholesterol composition and intracellular calcium responses to CCK. Results were correlated with clinical, biochemical, and morphometric characteristics.Results: Broad ranges of cellular cholesterol and CCK responsiveness were observed, with elevated cholesterol correlated with reduced CCK sensitivity. This was prominent with increasing degrees of obesity and the presence of diabetes, particularly when poorly controlled. No single standard clinical metric correlated directly with CCK responsiveness. Reduced CCK sensitivity best correlated with elevated serum triglycerides in normal-weight participants and with low HDL concentrations and elevated glycated hemoglobin in obese and diabetic patients.Conclusions: CCK responsiveness varies widely across the population, with reduced signaling in patients with obesity and diabetes. This could explain the failure of CCK agonists in previous clinical trials and supports the rationale to develop corrective modulators to reverse this defective servomechanism for appetite control. This trial was registered at www.clinicaltrials.gov as NCT03121755.

The Importance of the Gastrointestinal Tract in Controlling Food Intake and Regulating Energy Balance

The gastrointestinal tract, the key interface between ingested nutrients and the body, plays a critical role in regulating energy homeostasis. Gut-derived signals convey information regarding incoming nutrients to the brain, initiating changes in eating behavior and energy expenditure, to maintain energy balance. Here we review hormonal, neural, and nutrient signals emanating from the gastrointestinal tract and evidence for their role in controlling feeding behavior. Mechanistic studies that have utilized pharmacologic and/or transgenic approaches targeting an individual hormone/mediator have yielded somewhat disappointing body weight changes, often leading to the hormone/mediator in question being dismissed as a potential obesity therapy. However, the recent finding of sustained weight reduction in response to systemic administration of a long-acting analog of the gut-hormone glucagon-like peptide-1 highlights the therapeutic potential of gut-derived signals acting via nonphysiologic mechanisms. Thus, we also review therapeutics strategies being utilized or developed to leverage gastrointestinal signals in order to treat obesity.

Metabolic Actions of the Type 1 Cholecystokinin Receptor: Its Potential as a Therapeutic Target

Cholecystokinin (CCK) regulates appetite and reduces food intake by activating the type 1 CCK receptor (CCK1R). Attempts to develop CCK1R agonists for obesity have yielded active agents that have not reached clinical practice. Here we discuss why, along with new strategies to target CCK1R more effectively. We examine signaling events and the possibility of developing agents that exhibit ligand-directed bias, to dissociate satiety activity from undesirable side effects. Potential allosteric sites of modulation are also discussed, along with desired properties of a positive allosteric modulator (PAM) without intrinsic agonist action as another strategy to treat obesity. These new types of CCK1R-active drugs could be useful as standalone agents or as part of a rational drug combination for management of obesity.