Assessing plasma pharmacokinetics of cholesterol following oral coadministration with a novel vegetable stanol mixture to fasting rats

A gut-derived hormone regulates cholesterol metabolism

The reciprocal coordination between cholesterol absorption in the intestine and de novo cholesterol synthesis in the liver is essential for maintaining cholesterol homeostasis, yet the mechanisms governing the opposing regulation of these processes remain poorly understood. Here, we identify a hormone, Cholesin, which is capable of inhibiting cholesterol synthesis in the liver, leading to a reduction in circulating cholesterol levels. Cholesin is encoded by a gene with a previously unknown function (C7orf50 in humans; 3110082I17Rik in mice). It is secreted from the intestine in response to cholesterol absorption and binds to GPR146, an orphan G-protein-coupled receptor, exerting antagonistic downstream effects by inhibiting PKA signaling and thereby suppressing SREBP2-controlled cholesterol synthesis in the liver. Therefore, our results demonstrate that the Cholesin-GPR146 axis mediates the inhibitory effect of intestinal cholesterol absorption on hepatic cholesterol synthesis. This discovered hormone, Cholesin, holds promise as an effective agent in combating hypercholesterolemia and atherosclerosis.

Evaluation of the effect of plant sterols on the intestinal processing of cholesterol using an in vitro lipolysis model

An in vitro lipolysis model was utilized to study the effect of stigmastanol (lipophilic phytosterol) and disodium ascorbyl phytostanol phosphate (DAPP) (modified hydrophilic phytostanol) on intestinal processing of cholesterol to gain further understanding of their cholesterol lowering mechanism. Lipolysis results showed that stigmastanol, if given in powder alone, had no effect on cholesterol processing probably due to its poor solubility. Stigmastanol suspension formulation re-distributed cholesterol from aqueous phase to oil and sediment phases. The water soluble DAPP has changed cholesterol distribution even more significantly by transferring cholesterol from aqueous phase to sediment phase. Moreover, the results provided evidence that DAPP inhibited triglyceride digestion in vitro. Considering DAPP as a surfactant with the same lipophilic sterol ring as bile salt, its ability to inhibit triglyceride lipolysis may be due to its competition with bile salt for the substrate surface, thereby hindering the lipolysis of triglyceride and inhibiting cholesterol solubilization with the lipolysis products. It can be speculated that the cholesterol lowering mechanism of DAPP during intestinal digestion is related to its ability to act as a surfactant closely resembling bile salt.

Cancer chemopreventive potential of volatile oil from black cumin seeds, Nigella sativa L., in a rat multi-organ carcinogenesis bioassay

Nigella sativa (N. sativa) is a herbal plant of the Ranunculaceae family that has been widely used for various medicinal and nutritional purposes. Volatile oil extracts along with its major constituents, such as thymoquinone, have recently attracted considerable attention for their antioxidant, immunoprotective and antitumor properties. The present study was conducted to assess the chemopreventive potential of crude oils in N. sativa on tumor formation using a well-established rat multi-organ carcinogenesis model featuring initial treatment with five different carcinogens. Post-initiation administration of 1000 or 4000 ppm N. sativa volatile oil in the diet of male Wistar rats for 30 weeks significantly reduced malignant and benign colon tumor sizes, incidences and multiplicities. The treatment also significantly decreased the incidences and multiplicities of tumors in the lungs and in different parts of the alimentary canal, particularly the esophagus and forestomach. Bromodeoxyuridine labeling indices, reflecting cell proliferation were significantly decreased in various organs and lesions after treatment with the two doses of N. sativa. The plasma levels of insulin growth factor, triglycerides and prostaglandin E2 were also altered. The findings show, for the first time, that N. sativa administration exerts potent inhibitory effects on rat tumor development and on cellular proliferation in multiple organ sites. In particular, the ability to significantly inhibit murine colon, lung, esophageal and forestomach tumors was demonstrated in the post-initiation phase, with no evidence of clinical side effects. The mechanisms are likely to be related to suppression of cell proliferation.

Inhibition of intestinal absorption of cholesterol by surface-modified nanostructured aluminosilicate compounds

The aim of this work was to assess the ability of aqueous suspensions of surface-modified nanostructured aluminosilicate (NSAS) compounds to reduce the intestinal absorption of cholesterol in a rat model. The rats were divided into 10 treatment groups which included several NSAS compounds at various doses, ezetimibe at 10 mg/kg, stigmastanol at 50 mg/kg, and normal saline. All compounds and controls were independently administered by oral gavage and then a mixture of [(3)H]cholesterol and cold cholesterol in 10% Intralipid(R) was immediately administered orally to the animals. Systemic blood was sampled and the concentration of cholesterol in plasma was determined by means of radioactivity. Protonation of NSAS using an ion-exchange column resulted in significant inhibition of cholesterol absorption relative to the control group (31.5% and 38.6% reduction in absorption of cholesterol for 50 and 100 mg/kg doses, respectively). Other surface-ion modifications of NSAS compounds did not show significant effect on intestinal cholesterol absorption. The inhibition of cholesterol absorption by ezetimibe was superior and by stigmastanol was equal to the effect of protonated NSAS in the doses investigated in this study. In conclusion, protonated NSAS material seems to inhibit significantly the intestinal absorption of dietary cholesterol in a rat model.

Reduced absorption of saturated fatty acids and resistance to diet-induced obesity and diabetes by ezetimibe-treated and Npc1l1-/- mice

The impact of NPC1L1 and ezetimibe on cholesterol absorption are well documented. However, their potential consequences relative to absorption and metabolism of other nutrients have been only minimally investigated. Thus studies were undertaken to investigate the possible effects of this protein and drug on fat absorption, weight gain, and glucose metabolism by using Npc1l1(-/-) and ezetimibe-treated mice fed control and high-fat, high-sucrose diets. Results show that lack of NPC1L1 or treatment with ezetimibe reduces weight gain when animals are fed a diabetogenic diet. This resistance to diet-induced obesity results, at least in part, from significantly reduced absorption of dietary saturated fatty acids, particularly stearate and palmitate, since food intake did not differ between groups. Expression analysis showed less fatty acid transport protein 4 (FATP4) in intestinal scrapings of Npc1l1(-/-) and ezetimibe-treated mice, suggesting an important role for FATP4 in intestinal absorption of long-chain fatty acids. Concomitant with resistance to weight gain, lack of NPC1L1 or treatment with ezetimibe also conferred protection against diet-induced hyperglycemia and insulin resistance. These unexpected beneficial results may be clinically important, given the focus on NPC1L1 as a target for the treatment of hypercholesterolemia.

Antiatherogenic effects of dietary plant sterols are associated with inhibition of proinflammatory cytokine production in Apo E-KO mice

Dietary phytosterols significantly reduce atherosclerosis in apo E-deficient mice. Because atherosclerosis is a chronic inflammatory disease, we investigated whether the antiatherogenic effects of phytosterols are associated with reductions in proinflammatory cytokine production as well as the effect of this diet on global immunocompetence. Apolipoprotein (apo) E-deficient mice were fed a cholesterol-supplemented diet in the presence or absence of 2% dietary phytosterols for 14 wk and then immunized with ovalbumin. The relations between plasma lipid concentrations, atherosclerotic lesions, and cytokine production and proinflammatory stimuli or foreign antigens were characterized. Phytosterol-enriched diets were strongly associated with reduced plasma cholesterol concentrations and atherosclerosis in conjunction with higher anti-inflammatory [interleukin (IL)-10] and lower proinflammatory cytokine [IL-6, tumor necrosis factor (TNF)-alpha] production. In contrast, development of cytokine and chemokine responses to ovalbumin was as strong as or even improved in the phytosterol-treated mice relative to controls. The antiatherogenic effects of dietary phytosterols in apo E-knockout mice were associated with beneficial alterations in both lipoprotein metabolism and inflammatory pathways. Decreased capacity to mount proinflammatory cytokine and chemokine responses to inflammatory stimuli did not interfere with the global immunocompetence of such mice. Thus, the desirable suppression of proinflammatory cytokine production that was associated with inhibition of atherogenesis did not impair the capacity to mount responses to foreign antigens.

Development and characterization of liposomal disodium ascorbyl phytostanyl phosphates (FM-VP4)

The specific objectives of this project were (1) to develop liposomal disodium ascorbyl phytostanyl phosphate (FM-VP4) formulations, (2) to develop a liquid chromatography/mass spectrometry/mass spectrometry (LC/MS/MS) assay for quantification of FM-VP4 in liposomal formulations and plasma sample, and (3) to characterize liposomal FM-VP4 formulations by finding optimal drug-to-lipid ratios and determining the degradation of FM-VP4 in liposomes. Section 2 describes an LC/MS/MS assay developed for the identification and quantification of FM-VP4 in liposomal formulations to provide estimates of drug concentrations and encapsulation efficiency. The extra step of removing plasma proteins prior to LC/MS/MS assay yields an analysis of FM-VP4 in plasma samples. Section 3 describes experiments designed to find the optimal drug-to-lipid ratio for liposomal FM-VP4 formulations by comparing encapsulation efficiencies and varying the lipid compositions. Additionally, this section details our degradation studies to determine if liposomes have any protective effects on FM-VP4; these studies tested various lipid compositions at 37 degrees C in rabbit plasma. The mechanism of how FM-VP4 lowers low-density lipoprotein (LDL) cholesterol and total cholesterol levels in various animal models is presently unknown. However, before the mechanism of action could be studied, FM-VP4 first had to be delivered efficiently into plasma or cultured cell. The low systemic bioavailability and cellular uptake of FM-VP4 further suggested the importance of finding an efficient delivery vehicle for this drug. This project proposed a framework for such delivery and paves the way for further investigation into how FM-VP4 works in vivo and in vitro.

Disodium ascorbyl phytostanyl phosphate reduces plasma cholesterol concentrations and atherosclerotic lesion formation in apolipoprotein E-deficient mice

Disodium ascorbyl phytostanyl phosphate (FM-VP4) consists of ascorbic acid covalently bound to phytostanols by a phosphodiester linkage and is derived as the disodium salt. The purpose of this study was to evaluate the lipid-lowering and antiatherosclerotic properties of FM-VP4 following administration to apolipoprotein E (ApoE)-deficient mice. Four-week-old male C57BL/6J mice with a homozygous deletion of the ApoE gene (apolipoprotein E knock-out) were administered 0 (control), 0.1%, 0.5%, 1.0%, and 2.0% (wt/vol) FM-VP4 in their drinking water or 2.0% FM-VP4 (wt/wt) in their diet for 12 consecutive weeks. All animals received a standard mouse chow diet consisting of 9.0% (wt/wt) fat and 0.2% (wt/wt) cholesterol. Plasma cholesterol and triglyceride levels were determined at baseline and at 4-week intervals (4, 8, and 12 weeks) throughout the term of the study. At the end of the study, mice were killed using CO(2) gas, and blood was taken from the heart. The heart and aorta were removed and sections of the aortic roots were stained with oil red O (ORO) and Movat's stain. The lesions found in this area were measured using a computer-assisted image analysis. Consumption of FM-VP4 by either food or drinking water routes was associated with an approximately 75% reduction in total plasma cholesterol levels and a 75% decrease in aortic atherosclerotic lesion area in ApoE-deficient mice over 12 weeks compared to controls. A trend in decreasing plasma triglyceride levels was also observed. Taken together these data suggest that FM-VP4 has both lipid-lowering and antiatherosclerotic properties following 12-week administration to ApoE-deficient mice.

Influence of phytostanol phosphoryl ascorbate (FM-VP4) on insulin resistance, hyperglycemia, plasma lipid levels, and gastrointestinal absorption of exogenous cholesterol in Zucker (fa/fa) fatty and lean rats

The purpose of this investigation was to determine the effects of Phytostanol Phosphoryl Ascorbate (FM-VP4) on insulin resistance, hyperglycemia, plasma lipid levels, body weight, and gastrointestinal absorption of exogenous cholesterol in Zucker (fa/fa) fatty and lean rats. A group of 12 age-matched male obese (n = 6) and lean (n = 6) Zucker rats were administered 250 mg/kg twice a day (as 2% FM-VP4 in drinking water) for 30 consecutive days. Fasted blood samples prior to and following treatment were taken from all rats for glucose, lipid, insulin, and leptin determination. An oral glucose tolerance test was also carried out at the end of the treatment protocol. In addition, male obese (n = 7) and lean (n = 8) Zucker rats were coadministered a single oral gavage of [(3)H]cholesterol plus cold cholesterol with or without FM-VP4 (20 mg/kg) dissolved in Intralipid and the plasma concentration of the radiolabel was determined 10 h following the dose. FM-VP4 30-day treatment did not alter body weight, morning glucose, insulin, lipids, and leptin concentrations. There was no alteration in glucose tolerance in the nondiabetic, normoglycemic lean group; however, there was a highly significant improvement in glucose tolerance in the fatty group following FM-VP4 treatment. In addition, the insulin response to oral glucose showed no significant change in nondiabetic lean rats, whereas there was a change in the insulin secretory profile in the fatty group following FM-VP4 treatment. Furthermore, following a single oral gavage of FM-VP4 resulted in a significant decrease in the percentage of radiolabeled cholesterol absorbed. These findings suggest that FM-VP4 treatment to fatty Zucker rats could result in increased glucose responsiveness of the insulin secreting pancreatic beta cells. Furthermore, our findings suggest that FM-VP4 may only be effective presystemically. Systemic administration of FM-VP4 is warranted to determine the therapeutic potential of this effect.

Effects of a novel hydrophilic phytostanol analog on plasma lipid concentrations in gerbils

This study was designed to determine the effects of a novel hydrophilic phytostanol analog, FM-VP4, on total plasma cholesterol, total plasma triglyceride, low-density lipoprotein (LDL) cholesterol, and high-density lipoprotein (HDL) cholesterol concentrations after acute oral administration to gerbils. Gerbils were administered a standard gerbil diet for 4 continuous weeks, and daily water and food intake was monitored and replaced. The diet contained either no FM-VP4 (control) or FM-VP4 at the following concentrations: 0.25, 0.50, 1.0, or 2.0% w/w; six gerbils were fed each diet formulation. After 4 weeks of receiving a single diet formulation, blood was obtained from each gerbil by cardiac puncture and the animals were sacrificed humanely. Plasma obtained from this blood was analyzed for total cholesterol, total triglyceride, and HDL cholesterol levels by standard enzymatic and precipitation techniques. LDL cholesterol levels were calculated using the Friedewald equation. Administration of dietary FM-VP4 resulted in significant decreases in total plasma cholesterol and LDL cholesterol concentrations compared with controls. Dietary FM-VP4 at concentrations of 1% and 2% (w/w) decreased total plasma cholesterol by 3.4 mmol/L compared with controls. This decrease was entirely due to the loss of cholesterol from the LDL pool because LDL cholesterol was decreased by 3.3 and 3.2 mmol/L after 1% and 2% (w/w) FM-VP4, respectively. There were no significant changes in plasma triglyceride or HDL cholesterol concentrations after the administration of FM-VP4. Animals administered 1% or 2% (w/w) FM-VP4 also had significantly lower body weight after 4 weeks of treatment compared with the other groups. However, no unusual behavior was observed in these animals. No major differences in daily water or food intake were observed throughout the study. These findings indicate that FM-VP4 decreases total and LDL cholesterol concentrations.