The effect of dietary fibre on bile acid metabolism in rats

1. Forty-eight male rats were fed sequentially for 14 d periods on diets containing different fibre contents. 2. One of the high-fibre diets was a commercial pelleted diet. The other was a low-fibre diet supplemented with 200 g wheat bran/kg. 3. At the end of each feeding period eight rats were killed. Liver microsomal cholesterol 7 alpha-hydroxylase (EC 1.14.1.-) activity and bile acid content of small intestine and colon were determined. 4. The different diets did not significantly alter the total intestinal bile acids, but affected the distribution and qualitative pattern in the colon and small intestine. 5. On the high-fibre diets deoxycholate, and hyodeoxycholate tended to be increased. 6. On the low-fibre diets the alpha, beta- and omega-muricholic acids tended to be increased. 7. Liver microsomal cholesterol 7 alpha-hydroxylase activity was lower in rats on the low-fibre and bran-supplemented low-fibre diets compared with that in rats fed on the commercial pelleted diet.     

Hormones regulating lipid and carbohydrate metabolism in premenopausal women: modulation by dietary lipids

The effect of high- and low-fat diets with different levels of fatty acid unsaturation on plasma hormones involved in lipid metabolism was studied during different phases of the menstrual cycle in 31 premenopausal women. Subjects were divided into two groups and were fed controlled diets containing 39% fat with a ratio of polyunsaturated to saturated fatty acids (P:S) of either 0.3 or 1.0 for four menstrual cycles and then switched to a 19% fat diet with the same P:S for another four cycles. Blood samples were analyzed during both the follicular and luteal phases. A significant direct effect of level of dietary fat was observed on plasma cortisol and dehydroepiandrosterone-sulphate whereas an inverse relationship was seen for plasma insulin. Both plasma insulin and growth hormone levels were higher during the luteal compared with the follicular phase of the menstrual cycle. None of the hormones was affected by the level of unsaturation of dietary fats.     

Impact of dietary protein on lipid metabolism in hamsters is source-dependent and associated with changes in hepatic gene expression

This study tested the hypothesis that protein source is a factor determining the impact of the diet on lipid metabolism in hamsters. Twenty-eight hamsters of similar body weight were assigned for a period of 8 weeks to one of the following four diets (seven per group) containing either 20 % (w/w) casein (CAS), beef protein (BF), wheat gluten (WG) or soya protein (SOY). The fat composition of the diet was the same (15.5 % w/w) in all groups and provided SFA, MUFA and PUFA representative of the average Canadian diet. After an overnight fast, blood and liver were collected for the measurement of serum lipids, fatty acid composition of liver phospholipids and mRNA levels of selected genes involved in lipid metabolism. WG resulted in lower total cholesterol, HDL-cholesterol and non-HDL-cholesterol but, along with SOY, in higher mRNA levels of cholesterol 7 alpha-hydroxylase and LDL receptor. Furthermore, both WG and SOY resulted in lower 18 : 3n-3, 20 : 4n-6, total n-6 PUFA, 18 : 1n-9 and total MUFA, but higher 22 : 6n-3, total n-3 PUFA, 22 : 6n-3/18 : 3n-3 and 22 : 5n-3/18 : 3n-3 ratios in liver phospholipids, and higher hepatic Delta6-desaturase mRNA levels. These results show that the impact of dietary protein on lipid metabolism is source-dependent and associated with changes in mRNA abundances of key hepatic enzymes and receptors.     

Prevention of brain protein and lipid oxidation elicited by a water-soluble oryzanol enzymatic extract derived from rice bran

Summary. Background: The antioxidant capacity of rice bran (RB) (due mainly to its -oryzanol content) is very well known. We have recently developed a water-soluble oryzanol enzymatic extract (WSOEE), which shows a greatly increased functionality. Aim of the study: The aim of our study is the evaluation of the antioxidant potential of WSOEE in an ex vivo model to compare its protective capacity against oxidative damage by active-oxygen substances and free radicals (mainly the peroxyl radical) to biomolecules (such as proteins and lipids) with that of antioxidants, such as Trolox (a water-soluble derivative of vitamin E), melatonin, and folic acid. Methods: WSOEE -oryzanol content and composition were determined by HPLC. Free-radical-scavenging capacity was evaluated using the assay based on phycoerythrin fluorescence. Antioxidant capacity against hydroperoxide-caused oxidative injury to proteins and lipids was evaluated using an ex vivo model: a rat brain homogenate. The effectiveness was determined by assessing protein damage (measured as carbonyl group content by Western blot immunoassay) and lipid peroxidation (measured as malondialdehyde content). Results: The WSOEE -oryzanol composition profile was similar to that of RB (cycloartenyl, 24-methylene cycloartenyl, campesteryl, and sitosteryl ferulates), but with two major differences: WSOEE -oryzanol concentration was five times higher than that of RB, and WSOEE was water soluble. WSOEE total antioxidant capacity to trap the peroxyl radical was high, and similar to that of Trolox. The capacity to inhibit lipid peroxidation induced by cumene hydroperoxide in rat brain homogenate yielded a protection similar to that of Trolox. WSOEE also showed the capacity to protect protein from oxidation phenomena in rat brain homogenate, with a behavior similar to that of melatonin. This is of particular importance, since the loss of protein function caused by oxidative modification may affect the activity of enzymes, receptors, and membrane transporters, among other functions. Conclusion: WSOEE is a new potential antioxidant agent from rice bran that shows a high free-radical-scavenging capacity and prevents protein oxidation and lipid peroxidation when cells ex vivo are exposed to free radicals.     

Suppression of avian hepatic lipid metabolism by solvent extracts of garlic: impact on serum lipids

The effects of garlic on lipid metabolism were examined in White Leghorn pullets that had been fed for 4 weeks either a control diet based on corn and soybean meal or an experimental diet containing either 3.8% garlic paste, a solvent extract (petroleum ether, methanol and water in sequence) of garlic paste, the residue or commercial garlic oil. Significant decreases in hepatic 3-hydroxy-3-methylglutaryl-CoA reductase (79-83%), cholesterol 7 alpha-hydroxylase (43-51%), fatty acid synthetase (17-29%) and in representative pentose-phosphate pathway (23-39%) activities accompanied the feeding of the petroleum ether-, methanol- and water-soluble fractions of garlic. Garlic paste and oil also suppressed these activities. Significant decreases in serum lipids occurred in response to the feeding of these garlic fractions: serum total cholesterol by 20-25%, low density lipoprotein cholesterol by 28-41% and triglycerides by 10-26%; but high density lipoprotein cholesterol failed to respond to these treatments. The residue remaining after solvent fractionation had little influence on these parameters. These findings were substantiated by a second study in which pullets of a commercial broiler line were fed the garlic fractions. The results confirm that garlic oil and odorous components of garlic lower cholesterol levels. An odorless water-soluble component of garlic also has this effect. The mechanism of the hypocholesterolemic action is at the level of the suppression of cholesterol biosynthesis.     

Interaction of dietary protein, cholesterol and age on lipid metabolism of the rat

1. Male rats at 1 (young) and 9 months (adult) of age were fed on purified diets, supplemented with or without cholesterol, containing 200 g protein/kg (casein (CAS), whey protein (WHY) or soya-bean protein (SOY] for 4 weeks. 2. SOY exerted a hypocholesterolaemic effect in young rats regardless of dietary cholesterol, whereas in adult rats it was observed only when a cholesterol-enriched diet was given. WHY was also hypocholesterolaemic in rats of both ages given cholesterol. SOY tended to reduce the liver cholesterol both in young and adult rats. 3. The liver hydroxymethylglutaryl-CoA reductase (NADPH) (EC 1.1.1.34) activity tended to be lower in the vegetable-protein groups than in the animal-protein groups in young rats, but the age-related reduction was observed only in the latter groups. 4. There was no significant age-related difference in the activity of liver cholesterol 7 alpha-monooxygenase (EC 1.14.13.17) in response to diets. However, when cholesterol was given, activity tended to decrease with age. Rats given SOY excreted more faecal steroids than those given casein, particularly adult rats. 5. The fatty acid profile of phosphatidylcholine and the delta 6-desaturase activity of liver microsomes indicated the reduced desaturation of linoleate in the SOY and WHY groups compared with the CAS groups. 6. The results thus showed a complex interaction of protein type, cholesterol and age on cholesterol homeostasis.     

Effects of dietary genistein on hepatic lipid metabolism and mitochondrial function in mice fed high-fat diets

OBJECTIVE: Genistein has been suggested to prevent insulin resistance and its related diseases. We investigated the effects of dietary genistein at different levels on hepatic lipid levels and mitochondrial functions in mice fed high-fat diets. METHODS: C57BL/6J mice were randomly divided into four groups and fed a high-fat diet containing genistein at levels of 0%, 0.1%, 0.2%, and 0.4% (HF, HF + 0.1G, HF + 0.2G, and HF + 0.4G) for 12 wk. We measured lipid levels in the blood and liver. We also observed messenger RNA (mRNA) expression of genes encoding proteins related to lipid and energy metabolism and antioxidant defense system and mitochondrial enzyme activities in the liver. RESULTS: The induction of fatty liver by HF was substantially decreased in the HF + 0.2G and HF + 0.4G groups. Peroxisome proliferator-activated receptorgamma coactivator mRNA was increased by HF + 0.4G. Although genistein did not affect peroxisomal acyl-CoA oxidase mRNA expression, it increased medium-chain acyl-CoA dehydrogenase mRNA expression in a dose-dependent manner and HF + 0.2G increased uncoupling protein-2 mRNA expression two-fold relative to HF mice. Genistein decreased malondialdehyde levels and increased glutathione levels in liver homogenates, regardless of dose. The HF + 0.1G diet increased mitochondrial glutathione peroxidase activity and mitochondrial succinate dehydrogenase activity. CONCLUSIONS: Although genistein at higher levels decreased hepatic fat accumulation possibly by increasing fatty acid oxidation and uncoupling protein, low-dose genistein increased mitochondrial enzyme activities in mice with fatty liver and obesity induced by high-fat diets.     

Effects of dietary protein on renal function and lipid metabolism in five-sixths nephrectomized rats

The objective of the present experiment was to examine the effect of substituting different quantities of soyabean protein for casein on renal function and lipid metabolism in rats with chronic renal failure induced by a five-sixths nephrectomy. Experimental animals were subjected to a nephrectomy and fed either casein or soyabean protein (200 or 100 g/kg diet). The diets were isoenergetic with identical fat, Na, K and P contents. Rats ingesting 200 g casein/kg diet showed a significantly (P<0.05) accelerated course of chronic renal failure, while the soyabean-protein groups showed retarded progression of the experimentally induced renal disease and hypercholesterolaemic effects. Rats in the low-soyabean-protein diet (100 g/kg) also demonstrated increased serum albumin and decreased serum triacylglycerol, total cholesterol concentrations and blood urea-N; however, the low-casein diet significantly (P<0.05) increased serum triacylglycerol. Results of the present study show that the replacement of casein by soyabean protein was related to the rate of progression of renal failure and improvement in lipid profiles in serum of five-sixths nephrectomized rats.     

The effect of dietary supplementation using isomeric blends of conjugated linoleic acid on lipid metabolism in healthy human subjects

Conjugated linoleic acid (CLA) refers to a group of positional and geometric isomers of linoleic acid. Studies using animal models have shown that CLA reduces adiposity, improves plasma lipoprotein metabolism and insulin sensitivity and reduces arteriosclerosis. Whilst CLA may have therapeutic potential with regard to coronary artery disease risk factors in human subjects, there has been little investigation into its effects in human subjects. This current study investigated the effects of dietary supplementation using two isomeric blends of CLA on triacylglycerol (TAG)-rich lipoprotein metabolism and reverse cholesterol transport in human subjects and evaluates whether CLA modulated cardiovascular disease risk factors. Fifty-one normolipidaemic subjects participated in this randomised double-blind placebo-controlled intervention trial. Subjects were randomly assigned to receive 3 g cis-9,trans-11-trans-10,cis-12 isomeric blend (50 : 50) or a cis-9,trans-11-trans-10,cis-12 isomeric blend (80 : 20) CLA or linoleic acid (control)/d for 8 weeks. The 50 : 50 CLA isomer blend significantly reduced (P相似文献   

Long-term effects of inadequate and excessive dietary ascorbate on bile acid metabolism in the guinea pig

The effects of long-term chronic ascorbic acid deficiency and excessive ascorbic acid consumption on bile acid metabolism and biliary lipid composition were studied in guinea pigs. Male, weanling guinea pigs were fed a cereal-based scorbutigenic diet for 19 or 21 weeks. Ascorbic acid was administered either orally at 0.15 (group A) or 2.0 (group B) mg/100 g body weight, or it was mixed in the diet at levels of 500 (group C), 16-22 (group D), or 20,000 mg/kg (group E). Chronic ascorbic acid deficiency (groups A and D) caused depression of hepatic cytochrome P-450 levels and elevation of plasma cholesterol. Excessive ascorbate consumption did not alter these parameters relative to control levels. In contrast to results obtained in guinea pigs fed low or high amounts of ascorbate for 7-9 weeks, prolonged consumption of inadequate or excessive ascorbate resulted in little or no change in bile acid metabolism and biliary lipid composition except that bile acid pool size was increased 12% as a result of excessive ascorbate ingestion. Results of the present study suggest that there may be important differences in the guinea pig's metabolic response to ascorbic acid deficiency and ascorbic acid excess, depending on the length of the experimental period.     

Effect of dietary protein status on urea metabolism and hepatic arginase activity of the pig

Experiments were conducted with cross-bred pigs to determine the effect of dietary protein concentration on liver arginase activity. In Exp. 1, pigs were fed diets containing 12, 18 or 24% protein. In Exp. 2, pigs were fed diets containing 12 or 24% protein. Pigs used in Exp. 1 were slaughtered after reaching a wt of 50 kg and after reaching 30, 60 and 90 kg wt in Exp. 2. Aliquots of a 50,000 x g liver supernatant were used for determination of arginase activity as well as endogenous activation kinetics. In addition, aliquots of the supernatants were fractionated by gel chromatography to determine the molecular species of swine liver arginase. Hepatic arginase activity was similar in pigs fed diets containing either 12 or 18% protein but greater in pigs fed the 24% protein diet. The data also indicate that greater than 70% of the hypatic cytosolic manganese is associated with arginase and that arginase activation may be regulated by manganese.     

全氟辛酸污染现状及对脂质代谢异常的影响

目的 综述全氟辛酸（PFOA）的环境污染状况和人体中的暴露数据,以及对脂质代谢异常的影响。方法 以“全氟辛酸”、“环境污染”、“脂质代谢异常”作为关键词在CNKI数据库中检索,以“Perfluorooctanoic Acid”、“PFOA”、“environmental pollution”、“abnormal lipid metabolism”作为检索词在PubMed数据库中检索相关文献。结果 几乎所有环境介质都能检测到PFOA的存在并且全世界范围内都存在PFOA残留于人体内的现象,PFOA主要通过代谢组学、固醇调节元件结合蛋白通路及对过氧化物酶增殖体激活受体-α作用导致脂质代谢异常。结论 PFOA对自然环境和人体的健康造成巨大威胁,未来仍需对其导致相关毒理后果展开进一步研究。     

Enteral nutrition with structured lipid: effect on protein metabolism in thermal injury

The effect of total enteral nutrition with structured and conventional lipids on protein and energy metabolism was assessed in gastrostomy-fed burned rats (30% body surface area) by measuring nitrogen balance, serum albumin, energy expenditure, and rectus muscle and liver fractional synthetic rates of protein (FSRs). Male Sprague-Dawley rats weighing 200 +/- 10 g received isovolemic diets that provided 50 kcal/d, 2 g/d amino acids, and 40% nonprotein calories as lipid for 3 d. The lipid source was either long-chain triglycerides (LCTs), medium-chain triglycerides (MCTs), structured lipid (SL), or a physical mix (PM) of the oils used in SL. Burned rats enterally fed either SL (p less than 0.01) or PM (p less than 0.05) yielded significantly higher daily and cumulative nitrogen balances and rectus muscle and liver FSRs than those fed either LCTs or MCTs. Rats fed SL or MCTs maintained higher serum albumin concentrations than rats fed either PM or LCTs. This study shows that the enteral administration of a mixed fuel system containing SL or its PM improves protein anabolism and attenuates net protein catabolism after thermal injury.     

Effects of changes in hydration on protein, glucose and lipid metabolism in man: impact on health

Alterations of cell volume induced by changes of extracellular osmolality have been reported to regulate intracellular metabolic pathways. Hypo-osmotic cell swelling counteracts proteolysis and glycogen breakdown in the liver, whereas hyperosmotic cell shrinkage promotes protein breakdown, glycolysis and glycogenolysis. To investigate the effect of acute changes of extracellular osmolality on whole-body protein, glucose and lipid metabolism in vivo, we studied 10 male subjects during three conditions: (i) hyperosmolality was induced by fluid restriction and intravenous infusion of hypertonic NaCl (2-5%, wt/vol) during 17 h; (ii) hypo-osmolality was produced by intravenous administration of desmopressin, liberal water drinking and infusion of hypotonic saline (0.4%); and (iii) the iso-osmolality study comprised oral water intake ad libitum. Plasma osmolality increased from 285+/-1 to 296+/-1 mosm/kg (P<0.001 during hyperosmolality, and decreased from 286+/-1 to 265+/-1 mosm/kg during hypo-osmolality (P<0.001). Total body leucine flux ([1-(13)C]leucine infusion technique), reflecting whole-body protein breakdown, as well as whole-body leucine oxidation rate (irreversible loss of amino acids) decreased significantly during hypo-osmolality. The glucose metabolic clearance rate during hyperinsulinaemic-euglycemic clamping increased significantly less during hypo-osmolality than iso-osmolality, indicating diminished peripheral insulin sensitivity. Glycerol turnover (2-[(13)C]glycerol infusion technique), reflecting whole-body lipolysis, increased significantly during hypo-osmolar conditions. The results demonstrate that the metabolic adaptation to acute hypo-osmolality resembles that of acute fasting, that is, it results in protein sparing associated with increased lipolysis, ketogenesis and lipid oxidation and impaired insulin sensitivity of glucose metabolism.