Astragalus polysaccharides lowers plasma cholesterol through mechanisms distinct from statins

To determine the efficacy and underlying mechanism of Astragalus polysaccharides (APS) on plasma lipids in hypercholesterolemia hamsters. The effect of APS (0.25 g/kg/d) on plasma and liver lipids, fecal bile acids and neutral sterol, cholesterol absorption and synthesis, HMG-CoA reductase activity, and gene and protein expressions in the liver and small intestine was investigated in twenty-four hypercholesterolemia hamsters. Treatment periods lasted for three months. APS significantly lowered plasma total cholesterol by 45.8%, triglycerides by 30%, and low-density lipoprotein-cholesterol by 47.4%, comparable to simvastatin. Further examinations revealed that APS reduced total cholesterol and triglycerides in the liver, increased fecal bile acid and neutral sterol excretion, inhibited cholesterol absorption, and by contrast, increased hepatic cholesterol synthesis and HMG-CoA reductase activity. Plasma total cholesterol or low-density lipoprotein-cholesterol levels were significantly correlated with cholesterol absorption rates. APS up-regulated cholesterol-7α-hydroxylase and LDL-receptor gene expressions. These new findings identify APS as a potential natural cholesterol lowering agent, working through mechanisms distinct from statins.     

Effects of soybean beta-conglycinin on hepatic lipid metabolism and fecal lipid excretion in normal adult rats

beta-Conglycinin decreased blood triacylglycerol (TAG) levels in male Wistar adult rats. Liver mitochondrial carnitine palmitoyltransferase activity in the beta-conglycinin-fed group significantly increased as against the casein-fed group. Hepatic fatty acid synthase activity in the beta-conglycinin group significantly decreased as against that of the casein-fed group. Fecal fatty acid excretion in the beta-conglycinin group was significantly higher than in the casein group.     

Effect of blood high density lipoprotein cholesterol concentration on fecal steroid excretion in humans

Daily excretion of fecal total bile acids and neutral steroids were compared in five controls and two patients with extremely low concentrations of plasma high density lipoprotein (3 to 11 mg/dl) and severe atherosclerosis. There was no significant difference in steroid excretion rates in the groups. The predominant bile acid excreted in control feces was deoxycholic acid; lithocholic acid was predominant in the patients. The patients showed no signs of significant liver disease.     

Dietary cholesterol lowers liver copper in rabbits

Atherosclerosis and hypercholesterolemia have been produced in rabbits since 1913 by feeding them cholesterol. These experiments have a great influence on current thinking about the etiology and possible prevention of ischemic heart disease. Male, New Zealand White rabbits were fed 0.5% dietary cholesterol. Cholesterol and copper in plasma increased sixty-fold and 50%, respectively. Liver copper decreased 74% and hematocrit decreased 25%. Iron was unchanged in heart and liver, but was increased in kidney. Zinc was decreased in heart, but was unchanged in liver or kidney. Changes in organ iron and zinc were smaller than the decrease in liver copper. Similar experiments with higher doses of dietary cholesterol may have resulted in copper deficiency. It may be appropriate to revise interpretations of data from these experiments and to reformulate hypothesis based on the data. Results are consonant with the theoretical implication of copper metabolism and copper deficiency in the etiology and pathogenesis of ischemic heart disease.     

Effects of dietary fibre on serum lipid levels and fecal bile acid excretion.

Epidemiologic studies have suggested that dietary fibre protects humans against coronary heart disease, but interpretation of the data is confounded by coexisting differences in both dietary and environmental variables. The hypocholesterolemic action of dietary fibre varies: in general mucilaginous fibres such as pectin and oat bran are more effective than particulate fibres such as wheat bran. Although the mechanism of action of mucilaginous fibres is not completely understood, there is evidence that they induce small increases in the fecal excretion of bile acids and neutral steroids that are not fully compensated for by de novo cholesterol synthesis.     

Effects of green tea consumption on human fecal microbiota with special reference to Bifidobacterium species

Green tea is one of the most popular beverages in the world. Its beneficial health effects and components have been extensively reviewed. However, little is known about the influence of green tea consumption on the human intestinal microbiota (HIM), which plays a crucial role in human health. Ten volunteers who did not usually consume green tea, drank it for 10 days and then stopped drinking it for 7 days. Their fecal samples were collected at three time points: before beginning the 10‐day green‐tea regime, at the conclusion of that 10 days, and 7 days after stopping the regime. Their fecal samples were analyzed by terminal restriction fragment length polymorphism with specific primer‐restriction enzyme systems for HIM and by using a real‐time PCR method for the Bifidobacterium species. Although the HIM of each subject was relatively stable, the proportion of Bifidobacterium species played an important role in the classification of their fecal microbiota. Although there were inter‐individual differences in the Bifidobacterium species, an overall tendency for the proportion of bifidobacteria to increase because of green tea consumption was noted. However, little change was observed in the composition of Bifidobacterium species in each sample. This suggests that the change in proportion was induced, not by an inter‐species transition, but by an intra‐species increase and/or decrease. In conclusion, green tea consumption might act as a prebiotic and improve the colon environment by increasing the proportion of the Bifidobacterium species.     

Effects of Lactobacillus acidophilus 43121 and a mixture of Lactobacillus casei and Bifidobacterium longum on the serum cholesterol level and fecal sterol excretion in hypercholesterolemia-induced pigs

The hypocholesterolemic effects of Lactobacillus acidophilus 43121 (43121) and a mixture of Lactobacillus casei and Bifidobacterium longum (MIX) were studied in hypercholesterolemia-induced pigs. Serum total cholesterol was decreased by supplementation of either 43121 or MIX, although, high-density lipoprotein cholesterol was not changed. The hypocholesterolemic effect of 43121 and MIX was mainly due to bile acid dehydroxylation, this effect being supplementation-time dependent.     

Black and green tea improves lipid profile and lipid peroxidation parameters in Wistar rats fed a high-cholesterol diet

In the present study, the efficacy of black tea (BT) and green tea (GT) was studied in relation to serum and hepatic oxidative abnormalities in hypercholesterolemic rats. Hypercholesterolemia was induced in male Wistar rats (8 week old) by feeding them with a high-cholesterol diet (HCD) for 35 days. The experimental rats were given BT and GT as a supplement (7 g/L) via drinking water. Increased hepatic and serum lipid profile along with abnormalities in oxidative marker, with a concomitant increase in the body weight, food intake, and food efficiency, were seen in hypercholesterolemic rats. Following the supplementation of BT and GT to rats fed with HCD, significantly lower levels of serum and hepatic cholesterol, triglycerides, serum low-density lipoprotein cholesterol, and increased high-density lipoprotein cholesterol levels were observed, when compared with hypercholesterolemic group. Further, significantly lower levels in the serum and hepatic lipid peroxidation, body weight gain, and food efficiency were observed in BT and GT group when compared with control and HCD fed group. However, no such significant changes were observed in the food intake upon supplementation with BT and GT. These results suggest that supplementation of BT and GT may protect against the serum and hepatic abnormalities in hypercholesterolemic rats.     

Temperature-dependent effects of cholesterol on sodium transport through lipid membranes by an ionizable mobile carrier

Temperature-jump relaxation experiments on Na⁺ transport by (221)C₁₀-cryptand were carried out in order to study the influence of cholesterol and its temperature-dependence on ion transport through thin lipid membranes. The experiments were performed on large, negatively charged unilamellar vesicles (LUV) prepared from mixtures of dioleoylphosphatidylcholine, phosphatidic acid and cholesterol (mole fractions 0–0.43), at various temperatures and carrier concentrations. The initial rates of Na⁺ transport and the apparent rate constants of its translocation by (221)C₁₀ increased with the carrier concentration and the temperature. The incorporation of cholesterol into the membranes significantly reduced the carrier concentration- and temperature-dependence of these two parameters. The apparent energy required to activate the transport decreased significantly with increasing carrier concentrations at any given cholesterol molar fraction, and increased significantly with the cholesterol molar fraction at any given carrier concentration. Our interpretation of the action of cholesterol on this transport system is based on the assumption that the binding cavity of cryptands is likely to be located towards the aqueous side of the dipole layer. The results are discussed in terms of the structural, physico-chemical and electrical characteristics of carriers and complexes, and of the interactions occurring between an ionizable mobile carrier and the membrane.     

Effect of green tea on hepatic lipid metabolism in mice fed a high-fat diet

Green tea (GT) is a widely consumed beverage with health benefits, including antiobesity effects; however, the efficacy of GT on lipid levels associated with obesity is not clearly understood. Here, we examined the impact of GT consumption on lipid metabolism in the livers of high-fat diet (HFD)-induced obese mice. We performed lipid profiling using ultraperformance liquid chromatography quadrupole time-of-flight mass spectrometry in C57BL/6J mice fed a normal diet (ND), HFD and HFD with GT for 12 weeks. The partial least squares discriminant analysis score plot showed a difference among the groups and revealed that the levels of several lipid metabolites were altered in mice fed HFD with GT. The decreased levels of lysophospholipids (LPLs), such as lysophosphatidylcholine, lysophosphatidylethanolamine and lysophosphatidylserine, in HFD mice compared to those of the ND group were recovered by supplementation of GT. In agreement with these lipid metabolites changes, hepatic lysophosphatidylcholine acyltransferase 2/4 was significantly increased in HFD mice. This study showed abnormal changes in lipid species associated with obesity, and these levels were attenuated by GT intake, suggesting a relationship between the reduction of hepatic LPL levels and inflammation in obesity.     

Dietary lysine restriction induces lipid accumulation in skeletal muscle through an increase in serum threonine levels in rats

We previously reported that dietary amino acid restriction induces the accumulation of triglycerides (TAG) in the liver of growing rats. However, differences in TAG accumulation in individual cell types or other tissues were not examined. In this study, we show that TAG also accumulates in the muscle and adipose tissues of rats fed a low amino acid (low-AA) diet. In addition, dietary lysine restriction (low-Lys) induces lipid accumulation in muscle and adipose tissues. In adjusting the nitrogen content to that of the control diet, we found that glutamic acid supplementation to the low-AA diet blocked lipid accumulation, but supplementation with the low-Lys diet did not, suggesting that a shortage of nitrogen caused lipids to accumulate in the skeletal muscle in the rats fed a low-AA diet. Serum amino acid measurement revealed that, in rats fed a low-Lys diet, serum lysine levels were decreased, while serum threonine levels were significantly increased compared with the control rats. When the threonine content was restricted in the low-Lys diet, TAG accumulation induced by the low-Lys diet was completely abolished in skeletal muscle. Moreover, in L6 myotubes cultured in medium containing high threonine and low lysine, fatty acid uptake was enhanced compared with that in cells cultured in control medium. These findings suggest that the increased serum threonine in rats fed a low-Lys diet resulted in lipid incorporation into skeletal muscle, leading to the formation of fatty muscle tissue. Collectively, we propose conceptual hypothesis that “amino-acid signal” based on lysine and threonine regulates lipid metabolism.