Effects of Dietary Oxidized Phytosterol on Lipid Metabolism in Rats.

Many in vitro studies have revealed the toxic effects of oxidized phytosterols (OPSs); however, their effects on lipid metabolism are not well understood in vitro. Therefore, we examined the bioavailability of OPS and compared the effects of dietary phytosterols (PSs) or OPS on lipid metabolism in rats. OPS was detected in the plasma and liver of rats administered 50 mg of OPS for 3 days. Rats were fed the AIN76 diet (C group), basal diet plus 0.25% PS (P group), or 0.25% OPS (O group) for 4 weeks. Dietary OPS but not PS reduced hepatic fatty acid synthase activity. Liver triacylglycerol (TG) levels tended to be lower in the P group than in the C group and were significantly lower in the O group. The mRNA expression level of HMG-CoA reductase in the liver was the lowest in the O group, whereas that of CYP27A1 was the highest in the O group. The mRNA expression levels of NPC1L1 in the intestinal mucosa were significantly lower in the P and O groups than in the C group. Consistent with these modulations, plasma total cholesterol (TC) and HDL-C levels were similar between the C and P groups but tended to be higher or significantly higher in the O group. Liver TC levels were significantly lower in the P and O groups than in the C group. Moreover, fecal neutral and acidic steroid levels were the highest in the O group. The mRNA expression level of Δ6 desaturase in the liver was significantly higher in both the P and the O groups than in the C group. The Δ6 desaturation indices of fatty acids in the total liver lipids were the highest in the O group. Thus, dietary OPS may modulate lipid metabolism in the liver.

Oligonol, a Low-molecular Weight Polyphenol Extracted from Lychee Fruit, Modulates Cholesterol Metabolism in Rats within a Short Period.

There is growing research interest in the hypocholesterolemic effect of various food components such as polyphenols. In this study, we examined the effects of oligonol-a low-molecular weight polyphenol extracted from lychee fruit-on cholesterol metabolism in rats under short-term administration. Administration of oligonol for 3 days significantly increased cecum weight and decreased cecal n-butyric acid concentrations in rats. Oligonol also significantly lowered the levels of hepatic cholesterol and increased the levels of total neutral steroids excreted in the feces. It also increased fecal ß-muricholic acid significantly, whereas the levels of total acidic steroids remained unchanged. Gene expression of hepatic CYP7A1 (cytochrome P450 family 7 subfamily A member 1) significantly increased following the administration of oligonol. This increase could be ascribed to changes in the expression of farnesoid X receptor, small heterodimer partner, and fibroblast growth factor 15 in ileum. Our data suggest that oligonol induces hypocholesterolemic effects through the inhibition of biliary cholesterol absorption from the intestine and the upregulation of cholesterol catabolism in rats even following short-term administration. Therefore, oligonol may be an important food component for reducing cholesterol level.

Effects of eicosapentaenoic acid and docosahexaenoic acid on anxiety-like behavior in socially isolated rats.

The effects of fish oil for improving mental health have been reported. The present study was undertaken to compare the effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on anxiety-like behavior using a rat model. Experimental diets enriched in EPA or DHA as glycerides were prepared. Rats were exposed to social isolation stress and fed the experimental diet for 14 days. The results of behavioral tests revealed that rats fed the EPA-enriched diet exhibited less anxiety-like behavior than rats fed the control or DHA-enriched diets. Furthermore, EPA suppressed anxiety-like behavior only in socially isolated rats. The increase in EPA contents in the brain phospholipid fraction by feeding EPA-enriched diet was more significant than that of DHA by feeding DHA-enriched diet. These results suggest that dietary EPA is more anxiolytic than DHA in rats exposed to social isolation stress and is effective in increasing EPA content in brain membranes.

Effect of Dietary Purified Xanthohumol from Hop (Humulus lupulus L.) Pomace on Adipose Tissue Mass, Fasting Blood Glucose Level, and Lipid Metabolism in KK-Ay Mice.

We previously showed that xanthohumol-rich hop extract (XRHE, ~18% xanthohumol) exerts anti-obesity effects in rats fed a high-fat diet through regulation of fatty acid metabolism. In this study, we examined the effects of dietary purified xanthohumol from XRHE (PX, ~91.9% xanthohumol) in KK-Ay mice in order to understand the anti-obesity effects of xanthohumol alone because XRHE contains 82% unknown compounds. Dietary consumption of PX significantly inhibited an increase in the visceral fat weight of mice compared to those fed control diet without PX. Plasma leptin level was significantly lower in the PX-fed group than in the control group. Dietary PX lowered hepatic fatty acid synthesis by down-regulation of SREBP1c mRNA expression in the liver. On the other hand, fatty acid ß-oxidation in the liver was promoted by dietary PX through the up-regulation of PPARα mRNA expression. Moreover, the fecal levels of fatty acids and carbohydrates increased by dietary PX. PX inhibited lipase or α-amylase activity in vitro. Thus, we found that PX may exert anti-obesity effects through the regulation of lipid metabolism and inhibition of intestinal fat and carbohydrate absorption, and that xanthohumol alone may exert anti-obesity effects.

Ezetimibe reduced hepatic steatosis induced by dietary oxysterols in nonhuman primates.

Oxidized cholesterol (oxysterols) plays an important and multifaceted role in lipid metabolism. Here we examined whether dietary oxysterols accelerate hepatic lipid accumulation and inflammation in nonhuman primates. We also examined the effect of the Niemann-Pick C1-like1 inhibitor, ezetimibe (Ez). Macaca fascicularis (5-year-old males) were fed either regular cholesterol + high-fat diet (control-HFD) or oxysterols + high-fat diet (ox-HFD; with 0.015% of oxysterols cholesterol) for 24 weeks. Compared with control-HFD, ox-HFD did not affect plasma lipid levels, but it did affect hepatic lipid levels [total cholesterol, 40.9 mg·g-1 (ox-HFD) versus 3.2 (control-HFD) mg·g-1; triglycerides, 28.0 (ox-HFD) versus 5.7 (control-HFD) mg·g-1]. Ox-HFD increased lipid accumulation as well as recruitment of inflammatory cells when compared to control-HFD. We then examined the effects of Ez, 0.2 mg·kg-1·day-1 for 12 weeks. In addition to a significant reduction in dyslipidemia, Ez alleviated biochemical and pathological aspects of steatosis. Dietary oxysterols aggravate steatosis in nonhuman primates. Treatment with Ez may be a novel therapeutic approach to NAFLD by alleviating dyslipidemia.

Effects of xanthohumol-rich hop extract on the differentiation of preadipocytes.

Xanthohumol is a major prenylated, hydrophobic flavonoid found in the female inflorescences of the hop plant (Humulus lupulus L.). In this study, we examined the effects of xanthohumol-rich hop extract containing 17.8% xanthohumol and 12.4% isoxanthohumol on the differentiation and adipogenesis of 3T3L1 cells. We observed that the extract inhibited the differentiation of 3T3L1 cells and intracellular fat droplets via the regulation of adipogenic factors such as the peroxisome proliferator-activated receptor gamma, CCAAT/enhancer binding protein alpha, and adipocyte fatty acid-binding protein.

Effects of xanthohumol-rich extract from the hop on fatty acid metabolism in rats fed a high-fat diet.

Xanthohumol is the major prenylated flavonoid of female inflorescences of the hop plant (Humulus lupulus L.) and is a hydrophobic flavonoid. We examined the effects of dietary xanthohumol-rich hop extract in obese rats that was induced by feeding a high-fat diet. Dietary xanthohumol-rich hop extract significantly lowered the body weight gain of these rats compared to rats fed a high-fat diet without the extract. The increase of body weight, liver weight, and triacylglycerol levels in the plasma and liver of the rats fed a high-fat diet was ameliorated by dietary xanthohumol-rich hop extract. Dietary xanthohumol-rich hop extract tended to reduce hepatic fatty acid synthesis through the reduction of hepatic SREBP1c mRNA expression in the rats fed a high-fat diet. The excreted of triacylglycerol into feces also was promoted by dietary xanthohumol-rich hop extract. Plasma adiponectin levels in the rats fed a high-fat diet also tended to be elevated by dietary xanthohumol-rich hop extract. Thus, xanthohumol-rich hop extract may inhibit the increase of body weight, liver weight, and triacylglycerol in the plasma and liver induced by feeding high-fat diet through the regulation of hepatic fatty acid metabolism and inhibition of intestinal fat absorption. Therefore, xanthohumol-rich hop extract may exert preventive function on the increase of body weight and tissue triacylglycerol levels by overnutrition.

Effect of dietary polyphenols from hop (Humulus lupulus L.) pomace on adipose tissue mass, fasting blood glucose, hemoglobin A1c, and plasma monocyte chemotactic protein-1 levels in OLETF rats.

Hop (Humulus lupulus L.) pomace contains procyanidin-rich polyphenols, which are large oligomeric compounds of catechin. We studied the effect of high dose (1%) of dietary hop pomace polyphenols (HPs) in Otsuka Long-EvansTokushima Fatty (OLETF) rats, an animal model of type 2 diabetes. By 70 days, the rats fed HPs tended to have a lower body weight and reduced mesenteric white adipose tissue weight than the rats fed a control diet. Triglyceride levels in both plasma and liver tended to be lower in the HPs-fed group than in the control group. Dietary HPs substantially suppressed the activities of hepatic fatty acid synthetase, glucose-6-phosphate dehydrogenase, and malic enzyme, through the suppression of SREBP1c mRNA expression in OLETF rats. Moreover, in the HPs-fed group, monocyte chemotactic protein-1 (MCP-1) expression and fasting blood glucose levels at 40 days, and hemoglobin A1c (HbA1c) levels at 70 days were significantly lower than those in the control group. Thus, dietary HPs may exert an ameliorative function on hepatic fatty acid metabolism, glucose metabolism, and inflammatory response accompanying the increase of the adipose tissue mass in OLETF rats.

Ezetimibe impairs uptake of dietary cholesterol oxidation products and reduces alterations in hepatic cholesterol metabolism and antioxidant function in rats.

Dietary cholesterol oxidation products (COP) induce various adverse effects, including development of atherosclerosis, modulation of lipid metabolism, and unfavorable changes in the antioxidant system. Therefore, we examined the effects of ezetimibe, a cholesterol absorption inhibitor on hepatic cholesterol metabolism and down-regulation of the antioxidant system in rats fed COP. Rats were fed a purified diet containing 0.3 % COP with or without ezetimibe (0.07 mg/100 g body weight) for 27 days. Levels of COP in both the plasma and liver were lowered by ezetimibe through promotion of COP excretion into the feces. Reflecting this effect, an increase in the arteriosclerotic index and a reduction in the mRNA expression of hepatic cholesterol biosynthesis transcripts by dietary COP were observed. Moreover, the ferric reducing ability of the plasma also was significantly higher in rats fed COP plus ezetimibe than in those fed COP alone. Finally, we also observed that ezetimibe enhanced the down-regulation of hepatic fatty acid synthesis in rats fed COP. Thus, ezetimibe, which inhibits the absorption of dietary COP from the small intestine, may exert preventive effects on dietary COP-induced disruption of cholesterol and fatty acid metabolism in the liver and down-regulation of the antioxidant system.

Dietary cholesterol oxidation products accelerate plaque destabilization and rupture associated with monocyte infiltration/activation via the MCP-1-CCR2 pathway in mouse brachiocephalic arteries: therapeutic effects of ezetimibe.

AIM: No prior studies have investigated the effects of dietary cholesterol oxidation products (oxysterols) on atherosclerotic plaque destabilization and rupture. We used an atherosclerotic mouse model with histological features similar to those seen in ruptured human plaques to test the hypothesis that (1) dietary oxysterols accelerate plaque destabilization and rupture and (2) a NPC1L1 inhibitor, ezetimibe, has therapeutic effects on these processes. METHODS AND RESULTS: Advanced atherosclerotic plaques were examined in innominate arteries of ApoE(-/-) mice that were fed either a regular high-fat diet (HFD) or HFD containing oxysterols (oxysterol-HFD; 6.8% of added cholesterol was oxidized) and infused with angiotensin II. Compared with HFD, oxysterol-HFD did not affect plasma lipid levels but did accelerate plaque destabilization and rupture, which was associated with increased monocyte infiltration/activation, monocyte chemoattractant protein-1 (MCP-1) expression, and matrix metalloproteinase (MMP) activity. Dietary oxysterol-induced plaque destabilization and rupture were blunted in ApoE(-/-) CCR2(-/-) mice. Oral treatment with ezetimibe, significantly decreased plasma lipid levels and prevented the acceleration of plaque destabilization and rupture induced by dietary oxysterol. These data indicate a primary role for monocyte-mediated inflammation via the MCP-1-CCR2 pathway and the resultant increase in MMP activity in plaque destabilization and rupture induced by dietary oxysterols in ApoE(-/-) mice. These data also provide a mechanism by which dietary oxysterols are connected with the pathogenesis of plaque destabilization and rupture. CONCLUSIONS: These data suggest that inhibition of the absorption of oxysterols by ezetimibe may be useful for the treatment of high-risk patients with high oxysterol intake.

Hepatic function and lipid metabolism are modulated by short-term feeding of cholesterol oxidation products in rats.

Dietary cholesterol oxidation products (COPs) modulate various metabolic processes, particularly lipid metabolism. In this study, we observed that dietary COPs perturbed hepatic function, linoleic acid desaturation, and cholesterol catabolism in rats that were fed with diets containing 0.5% COPs for a short duration (7 days). The rats (age, 8 weeks) were fed American Institute of Nutrition (AIN)-purified diets containing 0.5% cholesterol or 0.5% COPs for 7 days. The glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), and lactate dehydrogenase (LDH) levels were significantly high in rats fed with dietary COPs, but no such increase was observed in rats fed with dietary cholesterol, thereby indicating that dietary COPs may impair the hepatic function. The mRNA expression levels of Delta6 desaturase in the liver were significantly increased by dietary COPs, while these levels were significantly decreased by dietary cholesterol. However, the mRNA expression level of cholesterol 7alpha-hydroxylase (CYP7A1) in the liver was significantly decreased by dietary COPs and significantly increased by dietary cholesterol. Therefore, dietary COPs may modulate lipid metabolic processes such as linoleic acid desaturation and cholesterol catabolism even when they are consumed for a short duration. Hence, processed animal foods containing COPs should be consumed with caution.

Detection and changes in levels of testosterone during spermatogenesis in the freshwater planarian Bdellocephala brunnea.

It was reported recently that vertebrate-type steroids exist and control reproduction in several groups of invertebrates, including molluscs. Sexually reproductive freshwater planarians of the species Bdellocephala brunnea have a limited breeding season in their natural habitat. This phenomenon suggests that some endogenous reproductive hormones might play a role in vivo. However, to date, sex steroids such as androgen, estrogen, and progesterone have not been found in planarians. The goal of the present study was to determine whether androgen is present in sexual planarians such as B. brunnea. The presence of testosterone was detected by high-pressure liquid chromatography and, in sexually reproductive individuals in which no seminal vesicles were visible, the level of testosterone was about twice than that in individuals with visible seminal vesicles. An enzyme-linked immunosorbent assay revealed that the levels of testosterone during terminal spermatogenesis were three times higher than during the spermatocyte-building phase. Our results indicate that sexually reproductive freshwater planarians such as B. brunnea might have vertebrate-type steroids and show variation in testosterone levels during spermatogenesis.

Absorption of dietary cholesterol oxidation products and their downstream metabolic effects are reduced by dietary apple polyphenols.

Exogenous and endogenous cholesterol oxidation products (COPs) perturb various metabolic processes, and thereby they may induce various homeostasis-related disorders. Here, we observed that procyanidin-rich dietary apple polyphenol (APP) from unripe apples alleviates the perturbation of lipid metabolism by decreasing the exogenous COP levels in rats. Dietary COPs may be the greatest source of COPs found in the human body. Rats (4 weeks of age) were fed AIN-purified diets containing 0.3% COPs supplemented with 0.5 or 2.5% APP for 3 weeks. Dietary APP alleviated the growth inhibition action of the exogenous COPs. The modulations of the liver lipid profile by COPs remained unchanged. However, serum total cholesterol, high-density lipoprotein cholesterol, and triglyceride levels increased following the intake of dietary APP. Further, dietary APP inhibited the increase in lipid peroxide levels in the liver and serum by COPs. The activity of hepatic Delta6 desaturase was lowered by dietary APP in a dose-dependent manner, although exogenous COPs generally increased the activity of this enzyme. In keeping with this observation, Delta6 desaturation indices in the phospholipids and cholesteryl esters of the liver and serum lipids were lower in the APP-fed groups than those in the control group. Dietary APP also promoted the excretion of exogenous COPs, cholesterol, and acidic steroids in feces. Therefore, the inhibition of intestinal absorption of COPs may partly contribute to the alleviation of the perturbation of lipid metabolism and lipid peroxidation levels. Thus, APP may be an important removal agent of exogenous toxic material such as COPs contained in processed or fast foods.

Dose-dependent hypocholesterolemic actions of dietary apple polyphenol in rats fed cholesterol.

The dose-dependent hypocholesterolemic and antiatherogenic effects of dietary apple polyphenol (AP) from unripe apple, which contains approximately 85% catechin oligomers (procyanidins), were examined in male Sprague-Dawley rats (4 wk of age) given a purified diet containing 0.5% cholesterol. Dietary AP at 0.5 and 1.0% levels significantly decreased the liver cholesterol level compared with that in the control (AP-free diet-fed) group. Dietary AP also significantly lowered the serum cholesterol level compared with that in the control group. However, the HDL cholesterol level was significantly higher in the 1.0% AP-fed group than in the control group. Accordingly, the ratio of HDL-cholesterol/total cholesterol was significantly higher in the 0.5% AP-fed group and 1.0% AP-fed group than in the control group. Moreover, the atherogenic indices in the 0.5 and 1.0% AP-fed groups were significantly lower than those in the control group. The activity of hepatic cholesterol 7alpha-hydroxylase tended to be increased by dietary AP in a dose-dependent manner. In accord with this observation, dietary AP increased the excretion of acidic steroids in feces. Dietary AP also significantly promoted the fecal excretion of neutral steroids in a dose-dependent manner. These observations suggest that dietary AP at a 0.5 or 1.0% level exerts hypocholesterolemic and antiatherogenic effects through the promotion of cholesterol catabolism and inhibition of intestinal absorption of cholesterol.

Comparison of regulative functions between dietary soy isoflavones aglycone and glucoside on lipid metabolism in rats fed cholesterol.

The effects of dietary soy isoflavones aglycone and glucoside on lipid metabolism were compared in male Sprague-Dawley rats (4 weeks old) given purified diets containing 0.3% cholesterol. The rats were fed a diet supplemented with either isoflavone aglycone-rich powder (IF-A group) or isoflavone glucoside-rich powder (IF-G group) or isoflavone-free diet (control group) for 40 days. The additional level of isoflavone aglycone moiety in the diet was prepared to the same level (approximately 0.096 g/100 g: approximately 0.1% in diet). The activity of hepatic cholesterol 7alpha-hydroxylase tended to be slightly higher in the rats fed isoflavones than in those fed the isoflavone-free diet. On the other hand, the activity of hepatic Delta6 desaturase in the IF-A group was lower than that of the control group. Reflecting this effect, the Delta6 desaturation indices [(20:3n-6+20:4n-6)/18:2n-6] in liver phospholipids of the IF-A group were lower than those in the control group. Liver and serum total cholesterol levels and liver TG level were also reduced by consumption of isoflavone aglycone. Moreover, serum TG level was lowered by consumption of both isoflavones aglycone and glucoside. The level of serum total isoflavones in the IF-A group was significantly higher than that in the IF-G group. Therefore, we speculate that the absorption speed of isoflavone aglycones might be faster than that of isoflavone glucosides in rats. This study suggests that dietary soy isoflavones, particularly their aglycone form, may exert a beneficial effect on lipid metabolism in rats fed cholesterol.

Effects of dietary protein of Korean foxtail millet on plasma adiponectin, HDL-cholesterol, and insulin levels in genetically type 2 diabetic mice.

We examined the effects of intake of Korean foxtail millet protein (FMP) on plasma levels of lipid, glucose, insulin, and adiponectin in genetically type 2 diabetic KK-Ay mice. When mice were fed a normal FMP diet or a high-fat-high-sucrose diet containing FMP for 3 weeks, in both experiments plasma concentrations of high-density lipoprotein cholesterol (HDL-cholesterol) and adiponectin increased remarkably in comparison with a casein diet group, whereas concentrations of insulin decreased greatly and that of plasma glucose was comparable to that in the casein diet group. Considering the role of adiponectin, insulin, and HDL-cholesterol in diabetes, atherosclerosis, and obesity, it appears likely that FMP may improve insulin sensitivity and cholesterol metabolism through an increase in adiponectin concentration. Therefore, FMP would serve as another beneficial food component in obesity-related diseases such as type 2 diabetes and cardiovascular diseases.

Regulative actions of dietary soy isoflavone on biological antioxidative system and lipid metabolism in rats.

Male Sprague-Dawley rats, 4 weeks of age, were fed purified diets either with or without 0.2% soy isoflavones rich powder for 5 weeks to elucidate their direct functions such as antioxidative action and regulation of lipid metabolism. Dietary soy isoflavones decreased serum lipid peroxide level in rats. Levels of liver and serum alpha-tocopherol were higher in the rats fed isoflavone than in those fed isoflavones-free diet. Thus, dietary soy isoflavones exhibited mild antioxidative function in this animal experiment. Isoflavone metabolites from diet may act as scavengers of reactive oxygen species. Dietary soy isoflavones lowered hepatic 3-hydroxy-3-methylglutaryl CoA reductase activity, although liver cholesterol level was not modulated. However, the levels of serum cholesterol and triglyceride decreased by consumption of soy isoflavones. Therefore, dietary soy isoflavones may exhibit hypocholesterolemic and hypolipidemic functions. Moreover, dietary soy isoflavones lowered hepatic Delta6 desaturase activity. Reflecting this observation, Delta6 desaturation indices ((18:2(n = 6) + 18:3(n = 6))/20:4(n = 6)) of tissue lipids tended to be lower in rats fed isoflavones than in those fed isoflavones-free diet. This action may contribute to the prevention of inflammatory response by imbalance of eicosanoids. These observations suggest that the positive intake of soy isoflavones may reduce the risk of some cardiovasucular diseases through their radical scavenging function and hypocholesterolemic action.