Plasma cholesterol-lowering activity of dietary dihydrocholesterol in hypercholesterolemia hamsters

Effect of Gut Microbiota on Blood Cholesterol: A Review on Mechanisms

The gut microbiota serves as a pivotal mediator between diet and human health. Emerging evidence has shown that the gut microbiota may play an important role in cholesterol metabolism. In this review, we delve into five possible mechanisms by which the gut microbiota may influence cholesterol metabolism: (1) the gut microbiota changes the ratio of free bile acids to conjugated bile acids, with the former being eliminated into feces and the latter being reabsorbed back into the liver; (2) the gut microbiota can ferment dietary fiber to produce short-chain fatty acids (SCFAs) which are absorbed and reach the liver where SCFAs inhibit cholesterol synthesis; (3) the gut microbiota can regulate the expression of some genes related to cholesterol metabolism through their metabolites; (4) the gut microbiota can convert cholesterol to coprostanol, with the latter having a very low absorption rate; and (5) the gut microbiota could reduce blood cholesterol by inhibiting the production of lipopolysaccharides (LPS), which increases cholesterol synthesis and raises blood cholesterol. In addition, this review will explore the natural constituents in foods with potential roles in cholesterol regulation, mainly through their interactions with the gut microbiota. These include polysaccharides, polyphenolic entities, polyunsaturated fatty acids, phytosterols, and dicaffeoylquinic acid. These findings will provide a scientific foundation for targeting hypercholesterolemia and cardiovascular diseases through the modulation of the gut microbiota.

New insights into the effect of bisphenol AF exposure on maternal mammary glands at various stages of gestation in mice

Bisphenol AF (BPAF) is the most estrogenic compound among BPA analogs. Mammary glands (MDs) are special organs that undergo repeated cycles of structural development, metabolism, and functional differentiation. Gestation is a sensitive window for MDs. In the present study, plug-positive CD-1 mice were exposed to vehicle (Veh) or 300 μg/kg BPAF through oral gavage every second day during gestation, and maternal MDs were collected from different developmental windows at 9.5, 13.5, and 18.5 d of gestation (gestation day [GD]9.5, GD13.5 and GD18.5). The results showed that gestational BPAF exposure induced a significantly elevated MD density at GD18.5. Non-target metabolomics analysis was used to screen for tyrosine, valine, ornithine, proline, threonine, phenylalanine and asymmetrical dimethylarginine (ADMA) amino acids, which changed significantly at all time points. Furthermore, the mRNA expression levels of genes related to these amino acids also changed significantly. Additionally, amino acid levels in BPAF-treated MGs at GD18.5 were related to the serum ammonia concentration of the corresponding offspring. These results provide a comprehensive view of the adverse effects of BPAF exposure during gestation on the maternal MG structure and function, which may affect milk components during lactation. Moreover, higher amino acids content may lead to amino acid imbalance or hyperammonemia in newborns.

Deficiency of coiled-coil domain containing 80 increases plasma cholesterol by decreasing fecal sterols excretion in hypercholesterolemic mice

Disorders in cholesterol and bile acid metabolism have been acknowledged as critical in pathogenesis of hypercholesterolemia. Coiled-coil domain containing 80 (CCDC80) has been closely linked to lipid homeostasis in mice, with its role in cholesterol metabolism yet to be fully elucidated. This study aims to uncover the regulatory mechanisms of CCDC80 in diet-induced hypercholesterolemia. We generated a CCDC80 knockout (CCDC80^-/-) model in C57BL/6 mouse. The initial transcriptional and metabolic consequences of removing CCDC80 were accessed at baseline by gene expression microarrays and gas chromatography-mass spectrometry / ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry, respectively. The hepatic cholesterol was investigated in both CCDC80^+/+ and CCDC80^-/- male mice at baseline and after feeding a high-cholesterol diet for 12 weeks. The regulatory effects of CCDC80 on gene expressions and protein masses were measured by RT-qPCR and western blot, respectively. At baseline, the KEGG pathway enrichment analysis combining metabolomics, lipidomics and transcriptomics, revealed a down-regulation of hepatic bile acid biosynthesis by CCDC80-knockout, especially for primary bile acids. In the hypercholesterolemic models, our results showed that deficiency of CCDC80 increased plasma and liver cholesterol levels, but decreased fecal neutral and acidic sterols excretion in mice. Mechanistically, we found that such effects were partly mediated by attenuating the alternative pathway of bile acid synthesis catalyzed by oxysterol 7-alpha-hydroxylase (CYP7B1). In conclusion, our results suggest CCDC80 as a novel modulator of cholesterol homeostasis in male mice. Deficiency of CCDC80 could further impair fecal sterols excretion in diet-induced hypercholesterolemia.

Azoxymethane Alters the Plasma Metabolome to a Greater Extent in Mice Fed a High-Fat Diet Compared to an AIN-93 Diet

Consumption of a high-fat diet (HFD) links obesity to colon cancer in humans. Our data show that a HFD (45% energy fat versus 16% energy fat in an AIN-93 diet (AIN)) promotes azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) formation in a mouse cancer model. However, the underlying metabolic basis remains to be determined. In the present study, we hypothesize that AOM treatment results in different plasma metabolomic responses in diet-induced obese mice. An untargeted metabolomic analysis was performed on the plasma samples by gas chromatography time-of-flight mass spectrometry (GC-TOF-MS). We found that 53 of 144 identified metabolites were different between the 4 groups of mice (AIN, AIN + AOM, HFD, HFD + AOM), and sparse partial least-squares discriminant analysis showed a separation between the HFD and HFD + AOM groups but not the AIN and AIN + AOM groups. Moreover, the concentrations of dihydrocholesterol and cholesterol were inversely associated with AOM-induced colonic ACF formation. Functional pathway analyses indicated that diets and AOM-induced colonic ACF modulated five metabolic pathways. Collectively, in addition to differential plasma metabolomic responses, AOM treatment decreases dihydrocholesterol and cholesterol levels and alters the composition of plasma metabolome to a greater extent in mice fed a HFD compared to the AIN.

Rutin and Quercetin Decrease Cholesterol in HepG2 Cells but Not Plasma Cholesterol in Hamsters by Oral Administration

Rutin (R) and quercetin (Q) are two widespread dietary flavonoids. Previous studies regarding the plasma cholesterol-lowering activity of R and Q generated inconsistent results. The present study was therefore carried out to investigate the effects of R and Q on cholesterol metabolism in both HepG2 cells and hypercholesterolemia hamsters. Results from HepG2 cell experiments demonstrate that both R and Q decreased cholesterol at doses of 5 and 10 µM. R and Q up-regulated both the mRNA and protein expression of sterol regulatory element binding protein 2 (SREBP2), low-density lipoprotein receptor (LDLR), and liver X receptor alpha (LXRα). The immunofluorescence study revealed that R and Q increased the LDLR expression, while only Q improved LDL-C uptake in HepG2 cells. Results from hypercholesterolemia hamsters fed diets containing R (5.5 g/kg diet) and Q (2.5 g/kg diet) for 8 weeks demonstrate that both R and Q had no effect on plasma total cholesterol. In the liver, only Q reduced cholesterol significantly. The discrepancy between the in vitro and in vivo studies was probably due to a poor bioavailability of flavonoids in the intestine. It was therefore concluded that R and Q were effective in reducing cholesterol in HepG2 cells in vitro, whereas in vivo, the oral administration of the two flavonoids had little effect on plasma cholesterol in hamsters.

Vinegars but not acetic acid are effective in reducing plasma cholesterol in hamsters fed a high-cholesterol diet

The present study compares the effect of two types of vinegars, Balsamic vinegar of Modena (BV) and Chinese Shanxi vinegar (SV), with acetic acid on plasma cholesterol using hamsters as a model. Hamsters (n = 40) were divided into five groups (n = 8 each) with two control groups being fed a low-cholesterol diet (LCD) or a high-cholesterol diet containing 0.2% cholesterol (HCD). The three experimental groups were given a HCD diet and gavaged with 8 ml of BV, SV, and acetic acid solution (AC) per kg body weight, respectively. Acetic acid in BV, SV, and AC solutions was adjusted with water to be 20 mg ml-1. The whole experiment lasted for 9 weeks. Plasma total cholesterol (TC) in BV and SV groups but not in the AC group was reduced by 17% and 20%, respectively, compared with that in HCD hamsters. BV and SV significantly reduced cholesterol in the liver and increased the fecal excretion of neutral sterols and bile acids. Real-time PCR analysis demonstrated that BV and SV significantly up-regulated the mRNA of cholesterol 7 alpha-hydroxylase (CYP7A1) in the liver. In conclusion, BV and SV but not AC were effective in reducing plasma TC and non-HDL-C concentrations at least in hypercholesterolemic hamsters.

Plasma Cholesterol-Lowering Activity of Soybean Germ Phytosterols

Soybean germ phytosterols (SGP) largely exist in soybean germ oil. Our previous study demonstrated that soybean germ oil was effective in reducing plasma cholesterol. However, it remains unknown if its phytosterols are the active ingredients responsible for the plasma cholesterol-lowering activity. The present study aimed to test the effect of SGP on plasma cholesterol and to investigate its associated underlying mechanisms using hamsters as animal model. Male hamsters (n = 40) were randomly divided into five groups (n = 8/group) and fed one of the five diets: a non-cholesterol diet (NCD), a high cholesterol diet (HCD), a HCD diet containing 0.5% cholestyramine (PC), and two HCD diets containing 0.1% (LP) and 0.2% (HP) SGP, respectively, for six weeks. Results showed that SPG reduced plasma cholesterol level in a dose-dependent manner, whereas it dose-dependently increased the excretion of both fecal neutral and acidic sterols. SGP was also effective in displacing cholesterol from micelles. It was concluded that SGP possessed hypocholesterolemic activity, likely by inhibiting cholesterol absorption in the intestine and promoting fecal sterol excretion.

Isoflavones enhance the plasma cholesterol-lowering activity of 7S protein in hypercholesterolemic hamsters

Previous studies have shown that 7S protein is the active ingredient responsible for the plasma cholesterol-lowering activity of soybean. It is hypothesized that isoflavones in soybean could enhance the blood cholesterol-lowering activity of 7S protein. Forty-eight hamsters were divided into six groups and fed a non-cholesterol diet or one of the five high-cholesterol diets containing 12.1% 7S protein with 0-15.62 mg g-1 isoflavones. The results showed that addition of isoflavones in diets dose-dependently enhanced the plasma total cholesterol-lowering activity of 7S protein. Addition of isoflavones in 7S protein-based diets significantly reduced hepatic cholesterol accumulation by 12.6-26.1%, compared with the high cholesterol control diet. Isoflavones could also facilitate excretion of neutral sterols in a dose-dependent manner. Supplementation of isoflavones in diets favourably modulated mRNA expression and the protein mass of HMG-CoA reductase. It was concluded that the enhancing effect of isoflavones on the blood cholesterol-lowering activity of 7S protein was mediated by inhibiting the cholesterol absorption and de novo cholesterol synthesis in hypercholesterolemic hamsters.

Pinto Beans (Phaseolus vulgaris L.) Lower Non-HDL Cholesterol in Hamsters Fed a Diet Rich in Saturated Fat and Act on Genes Involved in Cholesterol Homeostasis

BACKGROUND

Pinto beans contain multiple active agents such as polyphenols, flavonoids, and saponins, and have been shown to lower cholesterol, but the mechanisms involved in this effect have not been explored.

OBJECTIVE

This study was to investigate the changes in cholesterol metabolism in response to whole pinto beans (wPB) and their hulls (hPB) supplemented into a diet rich in saturated fat and the molecular mechanisms potentially responsible for these effects in hamsters.

METHODS

Forty-four 9-wk-old male Golden Syrian hamsters were randomly assigned to 4 diet groups (n = 11), including a 5% (wt:wt) fat diet [normal-fat diet (NF)], a 15% (wt:wt) fat diet [diet rich in saturated fat (HSF), saturated fatty acids accounted for 70% of total fatty acids], or HSF supplemented with 5% (wt:wt) wPB or 0.5% (wt:wt) hPB for 4 wk. Plasma, liver, intestinal, and fecal samples were collected to evaluate multiple cholesterol markers and gene targets.

RESULTS

The plasma non-high-density lipoprotein (non-HDL) concentration was significantly reduced in the wPB- and hPB-supplemented groups by 31.9 ± 3.5% and 53.6 ± 3.2%, respectively, compared with the HSF group (P < 0.01), to concentrations comparable with the NF group. The wPB-supplemented hamsters had significantly lower liver cholesterol (45.1%, P < 0.001) and higher fecal cholesterol concentrations (94.8%, P = 0.001) than those fed the HSF. The expressions of hepatic 3-hydroxy-3-methylglutaryl CoA reductase (Hmgcr) and small intestinal acyl-coenzyme A: cholesterol acyltransferase 2 (Acat2) were significantly decreased in animals administered wPB (by 89.1% and 63.8%, respectively) and hPB (by 72.9% and 47.7%, respectively) compared with their HSF-fed counterparts (P < 0.05). The wPB normalized the expression of Acat2 to the level of the NF group.

CONCLUSION

Pinto beans remediated high cholesterol induced by HSF in male hamsters by decreasing hepatic cholesterol synthesis and intestinal cholesterol absorption, effects which were partially exerted by the hulls.

Dietary wood pulp-derived sterols modulation of cholesterol metabolism and gut microbiota in high-fat-diet-fed hamsters

Wood pulp-derived sterols (WS) supplementation ameliorated HFD-associated metabolic disorder; WS supplementation increased the amounts of fecal sterols excretion and SCFAs content; WS supplementation modulated gut microbiota composition.

Soybean germ oil reduces blood cholesterol by inhibiting cholesterol absorption and enhancing bile acid excretion

Soybean germ oil is beneficial in management of hypercholesterolemia in hamsters fed a high cholesterol diet.

Dose-Dependent Increases in Liver Cholesterol but Not Plasma Cholesterol from Consumption of One to Five Whole Eggs and No Effects from Egg Whites on Liver or Plasma Cholesterol in Hamsters

The dose-dependent effect of egg consumption on plasma cholesterol in humans remains inconclusive. It is unknown if egg white consumed in a normal amount can reduce plasma cholesterol. We used hamsters as a model to (i) investigate the dose-dependent effect of consuming zero to five whole eggs on plasma total cholesterol (TC) and (ii) examine if egg white, equivalent to one to five eggs, possessed any reducing effects on plasma TC. In experiment 1, hamsters were divided into six groups ( n = 8 each) and fed either a control diet or one of five experimental diets supplemented with whole-egg powder equivalent to one to five eggs per 2000 kcal. Results showed that supplementation with one egg increased plasma TC by 25% compared with that of the control (226 ± 16 versus 282 ± 56 mg/dL, p < 0.05), whereas supplementation with two to five eggs did not significantly produce any additional effects on plasma cholesterol. However, supplementation with one to five eggs in diets caused a dose-dependent accumulation of cholesterol in the liver from 21.5 ± 4.4 to 71.3 ± 7.3 mg/g ( p < 0.01). In the second experiment, hamsters were divided into six groups and fed either a high-cholesterol control diet or one of five experimental diets supplemented with egg-white powder from one to five eggs. Results showed that egg-white powder affected neither plasma nor liver cholesterol levels. The egg-white powder did not affect fecal sterol excretion, suggesting it had no effect on cholesterol absorption. It was therefore concluded that consumption of two to five eggs did not significantly produce any additional effects on plasma cholesterol, whereas egg white did not possess a plasma-cholesterol-lowering activity if it was consumed at amounts similar to those in a normal human diet.

Cholesterol-Lowering Activity of Tartary Buckwheat Protein

Previous research has shown that Tartary buckwheat flour is capable of reducing plasma cholesterol. The present study was to examine the effect of rutin and Tartary buckwheat protein on plasma total cholesterol (TC) in hypercholesterolemia hamsters. In the first animal experiment, 40 male hamsters were divided into four groups fed either the control diet or one of the three experimental diets containing 8.2 mmol rutin, 8.2 mmol quercetin, or 2.5 g kg^-1 cholestyramine, respectively. Results showed that only cholestyramine but not rutin and its aglycone quercetin decreased plasma TC, which suggested that rutin was not the active ingredient responsible for plasma TC-lowering activity of Tartary buckwheat flour. In the second animal experiment, 45 male hamsters were divided into five groups fed either the control diet or one of the four experimental diets containing 24% Tartary buckwheat protein, 24% rice protein, 24% wheat protein, or 5 g kg^-1 cholestyramine, respectively. Tartary buckwheat protein reduced plasma TC more effectively than cholestyramine (45% versus 37%), while rice and wheat proteins only reduced plasma TC by 10-13%. Tartary buckwheat protein caused 108% increase in the fecal excretion of total neutral sterols and 263% increase in the fecal excretion of total acidic sterols. real-time polymerase chain reaction and Western blotting analyses showed that Tartary buckwheat protein affected the gene expression of intestinal Niemann-Pick C1-like protein 1 (NPC1L1), acyl CoA:cholesterol acyltransferase 2 (ACAT2), and ATP binding cassette transporters 5 and 8 (ABCG5/8) in a down trend, whereas it increased the gene expression of hepatic cholesterol-7α -hydroxylase (CYP7A1). It was concluded that Tartary buckwheat protein was at least one of the active ingredients in Tartary buckwheat flour to lower plasma TC, mainly mediated by enhancing the excretion of bile acids via up-regulation of hepatic CYP7A1 and also by inhibiting the absorption of dietary cholesterol via down-regulation on intestinal NPC1L1, ACAT2 and ABCG5/8.

Mannose Receptor Mediates the Immune Response to Ganoderma atrum Polysaccharides in Macrophages

The ability of mannose receptor (MR) to recognize the carbohydrate structures is well-established. Here, we reported that MR was crucial for the immune response to a Ganoderma atrum polysaccharide (PSG-1), as evidenced by elevation of MR in association with increase of phagocytosis and concentrations of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in normal macrophages. Elevation of MR triggered by PSG-1 also led to control lipopolysaccharide (LPS)-triggered inflammatory response via the increase of interleukin-10 (IL-10) and inhibition of phagocytosis and IL-1β. Anti-MR antibody partly attenuated PSG-1-mediated anti-inflammatory responses, while it could not affect TNF-α secretion, suggesting that another receptor was involved in PSG-1-triggered immunomodulatory effects. MR and toll-like receptor (TLR)4 coordinated the influences on the TLR4-mediated signaling cascade by the nuclear factor-κB (NF-κB) pathway in LPS-stimulated macrophages subjected to PSG-1. Collectively, immune response to PSG-1 required recognition by MR in macrophages. The NF-κB pathway served as a central role for the coordination of MR and TLR4 to elicit immune response to PSG-1.

Inhibitory effects on the HMG-CoA Reductase in the chemical constituents of the Cassia mimosoides Linn

Cassia mimosoides Linn has been used from ancient times and used for treating hepatitis for its supposedly medically beneficial properties. In this study, different constituents of the Cassia mimosoides Linn (β-Sitosterol, Oleanolic Acid, Emodin, Carotene, Resorcinol, Luteolin, and α-L-Rhamnose) were evaluated for potential anti-HMG-CoA reductase effect. The inhibitory effects of HMG-CoA reductase of Cassia mimosoides Linn extracts and Pravastatin inhibitor at different concentrations (at doses of 1, 5, 25 or 125 μg/mL, respectively) in reaction system (70 mmol/L phosphate buffer, 200mmol/L NADPH, 5 μg HMG-CoA reductase, 2 mmol/L EDTA, 2 mmol/L cysteamine, 0.06% BSA) into 37°C preheat HMG-CoA for initiating this reaction, and then determined the change of HMG-CoA reductase activity (ΔAΔt) at 340 nm, the inhibition ratio of HMG-CoA reductase activity and its dynamic change of inhibitory effect within 15 min and the descent rate of NADPH. Emodin, Luteolin, β-Sitosterol, Oleanolic Acid, α-L-Rhamnose and Carotene showed good inhibition of HMG-CoA reductase activity. Among them, only the Emodin (1 and 5 μg/mL) groups showed a significant decrease of HMG-CoA reductase activity compared to the Pravastatin (1 and 5 μg/mL) groups respectively. In addition, the HMG-CoA reductase activity in the Emodin and Luteolin (25 and 125 μg/mL) groups was clearly lower than the Pravastatin (25 and 125 μg/mL) groups respectively. And the Emodin and Luteolin (1, 5, 25 or 125 μg/mL) groups exhibited a stable effect on inhibiting the HMG-CoA reductase within 15 min. These findings further support the exploration of Cassia mimosoides Linn as a potential agent for the treatment of hepatitis in future studies.