A study on the inhibitory mechanism for cholesterol absorption by α-cyclodextrin administration

Cyclodextrin-induced release of drug-entrapping liposomes associated with the solation of liposome gels

In this work, we demonstrate that liposome gels in which liposomes are connected by polyethylene glycol terminated by cholesterol groups at both ends can store hydrophilic and hydrophobic drugs in the gel interiors, inner aqueous phases, and lipid membranes. The addition of cyclodextrins (CDxs) as extrinsic stimuli led to the release of drug-entrapping liposomes due to the interactions between CDxs and cholesteryl groups and/or the alkyl chains of lipids. The addition of aqueous solutions of β-CDx, dimethyl-β-CDx, trimethyl-β-CDx, and γ-CDx (final concentration: 7.5 mM) induced the solation of liposome gels and the release of liposomes accompanying the solation. Furthermore, the addition of β-CDx led to the partial release of hydrophilic drugs encapsulated in the liposomes, although the drug release was scarcely observed in other CDxs. In particular, the addition of trimethyl-β-CDx, which has low cytotoxicity, accelerated solation, and cationic liposomes released from the gels were effectively taken up by murine colon cancer (Colon26) cells. Thus, we propose that liposomes released from liposome gels can function as drug carriers.

The solation of liposome gels owing to the addition of trimethyl-β-cyclodextrin (TMe-β-CDx) and the uptake of cationic liposomes released from liposome gels by Colon26 cells are demonstrated.

Lecithin Inclusion by α-Cyclodextrin Activates SREBP2 Signaling in the Gut and Ameliorates Postprandial Hyperglycemia

BACKGROUND

α-cyclodextrin (α-CD) is one of the dietary fibers that may have a beneficial effect on cholesterol and/or glucose metabolism, but its efficacy and mode of action remain unclear.

METHODS

In the present study, we examined the anti-hyperglycemic effect of α-CD after oral loading of glucose and liquid meal in mice.

RESULTS

Administration of 2 g/kg α-CD suppressed hyperglycemia after glucose loading, which was associated with increased glucagon-like peptide 1 (GLP-1) secretion and enhanced hepatic glucose sequestration. By contrast, 1 g/kg α-CD similarly suppressed hyperglycemia, but without increasing secretions of GLP-1 and insulin. Furthermore, oral α-CD administration disrupts lipid micelle formation through its inclusion of lecithin in the gut luminal fluid. Importantly, prior inclusion of α-CD with lecithin in vitro nullified the anti-hyperglycemic effect of α-CD in vivo, which was associated with increased intestinal mRNA expressions of SREBP2-target genes (Ldlr, Hmgcr, Pcsk9, and Srebp2).

CONCLUSIONS

α-CD elicits its anti-hyperglycemic effect after glucose loading by inducing lecithin inclusion in the gut lumen and activating SREBP2, which is known to induce cholecystokinin secretion to suppress hepatic glucose production via a gut/brain/liver axis.

Effect of Roasting Degree, Extraction Time, and Temperature of Coffee Beans on Anti-Hyperglycaemic and Anti-Hyperlipidaemic Activities Using Ultrasound-Assisted Extraction

Coffee consumption has been linked to a low risk of metabolic syndrome. However, evidence supporting its anti-hyperglycaemic and anti-hyperlipidaemic activities remain poorly defined. The ultrasound-assisted extraction (UAE) technique has been shown to achieve high yields of bioactive compounds in coffee, with preserved functionality. The goal of the present study was to determine the effect of various coffee roasting extracts using UAE on their anti-hyperglycaemic and anti-hyperlipidaemic properties. We examined α-amylase and α-glucosidase, micelle size, micelle solubility, and pancreatic lipase activities. Coffee roasting degrees were classified as light coffee (LC), medium coffee (MC), and dark coffee (DC). We showed that DC at 80°C for 10 min, 40°C for 20 min, and 20°C for 20 min has a high potency to inhibit α-amylase, α-glucosidase, and pancreatic lipase activities by 33.79±3.25%, 19.68±1.43%, and 36.63±1.58%, respectively. LC enhanced cholesterol micelle size and suppressed cholesterol micelle solubility, which suggests that coffee roasting may enhance anti-hyperglycaemic and anti-hyperlipidaemic activities.

Effect of Elevated CO2 on Seed Yield, Essential Oil Metabolism, Nutritive Value, and Biological Activity of Pimpinella anisum L. Accessions at Different Seed Maturity Stages

Simple Summary

This study was conducted to investigate whether the positive impact of elevated CO₂ (eCO₂) on the chemical composition of aniseed (Pimpinella anisum L.) seeds is dependent on seed developmental stages and origin. To this end, we investigated the biochemical changes in eCO₂-treated aniseed accessions from Tunisia, Syria, Turkey, Morocco, Yemen, and Egypt during three developmental stages (immature, premature, and mature). The highest dry weight percentages and seed yields were recorded for the Egypt and Morocco accessions. eCO₂ has inducing properties on the nutritive and biological values of aniseeds, yet its effectiveness is related to seed maturity and provenances. For instance, seed maturation increased the nutrients and antioxidant metabolites in most eCO₂-treated accessions. Conversely, essential oil metabolism was decreased by seed maturation but this effect was significantly reduced by the use of eCO₂. The enhanced accumulation of bioactive compounds in eCO₂-treated seeds was accompanied by improved health benefits. In this regard, eCO₂ induces the antioxidant and hypocholesterolemic activities of aniseeds, particularly at mature stages. Thus, the present study confirms that there are significant interactions between eCO₂ exposure, aniseed maturity, and origin on the chemical composition and pharmaceutical properties of aniseed.

Abstract

Besides the lack of studies regarding applying elevated CO₂ (eCO₂) as a strategy to improve the chemical composition of anise (Pimpinella anisum L.) seeds, studies on its interaction with seed developmental stages and origin are very limited. The seed yield, chemical composition, and biological activity of 6 aniseed accessions (Egypt, Tunisia, Syria, Turkey, Yemen, and Morocco) were investigated during three developmental stages (immature, premature, and mature) under control and elevated CO₂ conditions. Mature seeds from all aniseed accessions had significantly higher (p < 0.05) dry weight (DW) percentages than premature and immature seeds. The highest DW percentages were recorded in Egypt and Morocco accessions. Seed maturation increased nutrients and antioxidant metabolites in most eCO₂-treated accessions. In contrast, essential oils were decreased by seed maturation, while eCO₂ reversed this effect. Essential oil-related precursors (e.g., phenylalanine) and enzyme activities (3-Deoxy-d-arabino-heptulosonate-7-phosphate synthase (DAHPS) and O–methyltransferase) decreased with seed maturity. However, high CO₂ reduced this impact and further induced the other essential oil-related precursors (shikimic and cinnamic acids). Consequently, eCO₂ provoked changes in the antioxidant and hypocholesterolemic activities of aniseeds, particularly at mature stages. Overall, eCO₂ application, as an efficient way to improve aniseed growth, essential oil metabolism, and chemical composition, was affected by seed maturation and origin. Future studies of eCO₂-treated aniseeds as a nutraceutical and pharmaceutical product are suggested.

Effect of Laser Light on Growth, Physiology, Accumulation of Phytochemicals, and Biological Activities of Sprouts of Three Brassica Cultivars

Brassica sprouts are known as a good source of antimicrobial bioactive compounds such as phenolics and glucosinolates (GLs). We aim at understanding how He-Ne laser light treatment (632 nm, 5 mW) improves sprout growth and physiology and stimulates the accumulation of bioactive metabolites in three Brassica spp., i.e., mustard, cauliflower, and turnip. Moreover, how these changes consequently promote their biological activities. Laser light improved growth, photosynthesis, and respiration, which induced the accumulation of primary and secondary metabolites. Laser light boosted the levels of pigments, phenolics, and indole and aromatic precursors of GLs, which resulted in increased total GLs and glucoraphanin contents. Moreover, laser light induced the myrosinase activity to provoke GLs hydrolysis to bioactive sulforaphane. Interestingly, laser light also reduced the anti-nutrient content and enhanced the overall biological activities of treated sprouts including antioxidant, antibacterial, anti-inflammatory, and anticancer activities. Accordingly, laser light is a promising approach for boosting the accumulation of beneficial metabolites in Brassica sprouts and, subsequently, their biological activities.

Elevated CO2 improves the nutritive value, antibacterial, anti-inflammatory, antioxidant and hypocholestecolemic activities of lemongrass sprouts

Sprouts have been regarded as a big store for bioactive compounds with a wide range of biological activities. Elevated CO2 (eCO2, 620 μmol mol-1)was employed to enhance the nutritive and health promoting values of sprouts of two species of lemongrass, i.e. Cymbopogon citratus and Cymbopogon proximus. eCO2 improved the biomass production of sprouts, and their levels of primary metabolites e.g., amino acids and oils and active secondary metabolites e.g., phenolic compounds. As a result, eCO2 increased total antioxidant capacity, cytotoxicity against several human cancer cell lines, and antibacterial activities of Cymbopogon sprouts. We also recorded a significant increase in hypocholesterolaemic potential and anti-inflammatory activities of eCO2-treated sprouts, as indicated by inhibition of cholesterol micellar solubility and pancreatic lipase activity, as well as lipoxygenase and cyclooxygenase activities, respectively. Thus, the present investigation supports the use of eCO2 as a promising approach to produce lemongrass sprouts with effective phytochemicals and enhanced biological activities.

Solubility of Piperine and Its Inclusion Complexes in Biorelevant Media and Their Effect on Attenuating Mouse Ileum Contractions

This study evaluated the solubility of piperine (PP) in biorelevant media and the effect of its ground mixtures (GMs) and coprecipitates (CPs) on intestinal contractions when presented in inclusion complexes with α-, β-, and γ-cyclodextrins (CDs). In the powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC) measurements, CP (PP/αCD) and CP (PP/γCD) suggest the formation of inclusion complexes. The ¹H-nuclear magnetic resonance (NMR) analysis showed the integrated intensity ratios of CP (PP/αCD) and CP (PP/γCD) protons to be 1/2 and 1/1, the same as the respective molar ratios in the respective GM inclusion complexes. The intestinal contraction test confirmed that the intestinal contraction rate of carbachol (CCh) in the presence of 2.0 × 10^-5 M PP was comparable to that in the absence of PP. On the other hand, CP (PP/αCD), GM (PP/αCD = 1/2), and GM (PP/βCD = 1/1) formed inclusion complexes that significantly suppressed the intestinal contractility at PP 1.0 × 10^-8 M. No significant differences were observed between CP and GM. The solubility of the PP/αCD inclusion complex was 6-7 times higher than that of PP in the fasted-state-simulated intestinal fluid (FaSSIF, pH 6.5). PP functioned to suppress intestinal contraction by forming an inclusion complex. Based on this result, PP/αCD might be expected to be effective as an antidiarrheal.

CO2 treatment improves the hypocholesterolemic and antioxidant properties of fenugreek seeds

A high level of serum cholesterol is a major cause of atherosclerosis. Fenugreek is a well-known hypocholesterolaemic agent with amazing phytochemical composition. Due to its impact on plant metabolism, CO₂ enrichment was tested as a strategy to support functional values in fenugreek seeds. Phytochemical composition and biological activities of three fenugreek cultivars (G2, G6 and G30) grown under ambient (aCO₂, 400 μmol mol^-1) and elevated CO₂ (eCO₂, 620 μmol mol^-1) were assessed. Applying eCO₂ improved physical parameters of fenugreek seeds, and enhanced their biological activities. A significant increase in hypocholesterolaemic potential, as indicated by inhibition of cholesterol micellar solubility and pancreatic lipase activity, was recorded. In addition, antioxidant, anti-lipid peroxidation and antibacterial activities were improved. These enhanced biological activities were accompanied by improved seed chemical composition at the primary and secondary metabolic levels. Therefore, eCO₂ treatment represents an efficient strategy to increase the hypocholesterolaemic, antioxidant and antibacterial activities of fenugreek seeds.

Anti-obesity effects of α-cyclodextrin-stabilized 4-methylthio-3-butenyl isothiocyanate from daikon (Raphanus sativus var. longipinnatus) in mice

4-Methylthio-3-butenyl isothiocyanate (MTBI) is a pungent bioactive constituent found in daikon. However, MTBI is immediately hydrolyzed to 3-hydroxy-methylene-2-thioxopyrrolidine in grated daikon. In this study, we evaluated whether MTBI in grated daikon complexed with α-cyclodextrin (αCD) has anti-obesity effects in mice. C57BL/6J mice were fed a normal diet (normal group), high-fat diet (HFD, control group), HFD with αCD (αCD group), or HFD with MTBI-αCD (MTBI-αCD group) for 16 weeks. The results showed that the final body weight, epididymal white adipose tissue weight, and plasma triglyceride and total cholesterol levels were significantly lower in the MTBI-αCD group than in the control group. The cell size in epididymal adipose tissue was significantly smaller and the accumulation of lipids in the liver was significantly lower in the MTBI-αCD group than in the control group. Furthermore, real-time polymerase chain reaction showed that the mRNA expression level of tumor necrosis factor-alpha was suppressed in the MTBI-αCD group. We also observed low superoxide dismutase activity in the MTBI-αCD group, possibly because MTBI-αCD has the potential to resist HFD-induced oxidative injury. In conclusion, MTBI-αCD exerted anti-inflammation and antioxidant effects to suppress lipid accumulation in epididymal adipose tissue and the liver. These effects then prevented HFD-induced obesity in mice.

Low amounts of dietary fibre increase in vitro production of short-chain fatty acids without changing human colonic microbiota structure

This study investigated the effect of various prebiotics (indigestible dextrin, α-cyclodextrin, and dextran) on human colonic microbiota at a dosage corresponding to a daily intake of 6 g of prebiotics per person (0.2% of dietary intake). We used an in vitro human colonic microbiota model based on batch fermentation starting from a faecal inoculum. Bacterial 16S rRNA gene sequence analysis showed that addition of 0.2% prebiotics did not change the diversity and composition of colonic microbiota. This finding coincided with results from a clinical study showing that the microbiota composition of human faecal samples remained unchanged following administration of 6 g of prebiotics over seven days. However, compared to absence of prebiotics, their addition reduced the pH and increased the generation of acetate and propionate in the in vitro system. Thus, even at such relatively low amounts, prebiotics appear capable of activating the metabolism of colonic microbiota.

Food Ingredients That Inhibit Cholesterol Absorption

Cholesterol is a vital component of the human body. It stabilizes cell membranes and is the precursor of bile acids, vitamin D and steroid hormones. However, cholesterol accumulation in the bloodstream (hypercholesterolemia) can cause atherosclerotic plaques within artery walls, leading to heart attacks and strokes. The efficiency of cholesterol absorption in the small intestine is of great interest because human and animal studies have linked cholesterol absorption with plasma concentration of total and low density lipoprotein cholesterol. Cholesterol absorption is highly regulated and influenced by particular compounds in the food supply. Therefore, it is desirable to learn more about natural food components that inhibit cholesterol absorption so that food ingredients and dietary supplements can be developed for consumers who wish to manage their plasma cholesterol levels by non-pharmacological means. Food components thus far identified as inhibitors of cholesterol absorption include phytosterols, soluble fibers, phospholipids, and stearic acid.

Development and Application of Cyclodextrin Hydrolyzing Mutant Enzyme Which Hydrolyzes β- and γ-CD Selectively

Cyclodextrins (CDs) are produced from starch by cyclodextrin glucanotransferase (CGTase), which has cyclization activity. Specifically, α-CD is an important biomolecule, as it is a molecular carrier and soluble dietary fiber used in the food industry. Upon inspection of the conserved regions of the glycoside hydrolase (GH) 13 family amylases, the amino acids K232 and H233 of CGTase were identified as playing an important role in enzyme reaction specificity. A novel CD hydrolyzing enzyme, cyclodextrin glycosyl transferase (CGTase)-alpha, was developed using site-directed mutagenesis at these positions. Action pattern analysis using various substrates revealed that CGTase-alpha was able to hydrolyze β- and γ-CD, but not α-CD. This selective CD hydrolyzing property was employed to purify α-CD from a CD mixture solution. The α-CD that remained after treatment with CGTase-alpha and exotype glucoamylase was purified using hydrophobic interaction chromatography with 99% purity.