The role of dietary fiber in lipid metabolism

Antiobesity Effects of Sansa (Crataegi fructus) on 3T3-L1 Cells and on High-Fat-High-Cholesterol Diet-Induced Obese Rats

This study was performed to investigate the effects of Crataegi fructus ethanol extracts (CFEEs) on the differentiation of 3T3-L1 cells, and to evaluate the effects of C. fructus powder (CFP) on lipid metabolism and its antiobesity effect in rats fed a high-fat and high-cholesterol (HFC) diet. Both in vitro and in vivo studies were performed for physiological activity and antiobesity effects on the serum, liver, and adipose tissues in obesity-induced rats. CFEEs showed significant inhibitory action on differentiation and triglyceride (TG) accumulation in 3T3-L1 mature cells in a dose-dependent manner. Subcutaneous, mesenteric, epididymal, and total adipose tissue weights of HFC diet group were heavier than those of normal diet (N) group, whereas those of groups fed CFP were significantly decreased. Levels of serum TGs, total cholesterol (TC), and low-density lipoprotein cholesterol were significantly decreased in the CFP groups than in the HFC group, whereas the serum high-density lipoprotein cholesterol level decreased in the HFC group and markedly increased in the CFP groups. TC and TG levels in the liver and adipose tissues were significantly lower in CFP groups than in the HFC groups. In addition, feeding with CFP significantly reduced the occurrence of fatty liver deposits and steatosis, and inhibited an HFC diet-induced increase in adipocyte size. These results suggest that C. fructus may improve lipid metabolism in the serum, liver, and adipose tissue, and may potentially reduce lipid storage.

Effects of alfalfa hay and its physical form (chopped versus pelleted) on performance of Holstein calves

Inclusion of forage and its physical form in starter may affect rumen development, average daily gain (ADG), and dry matter intake (DMI) of dairy calves. To evaluate the effects of forage and its physical form (chopped vs. pelleted) on growth of calves under a high milk feeding regimen, 32 Holstein calves (38.8±1.1kg) were assigned at birth to 1 of 3 treatments in a completely randomized block design. Dietary treatments (% of dry matter) were (1) 100% semi-texturized starter (CON); (2) 90% semi-texturized starter + 10% chopped alfalfa hay (mean particle size=5.4mm) as a total mixed ration (TMR; CH); and (3) 90% semi-texturized starter + 10% pelleted alfalfa (mean=5.8mm) hay as a TMR (PH). Data were subjected to mixed model analysis with contrasts used to evaluate effect of forage inclusion. Calves were weaned at 76 d of age and the experiment finished 2 wk after weaning. Individual milk and solid feed consumption were recorded daily. Solid feed consumption and ADG increased as age increased (effect of week), but neither forage inclusion nor physical form of forage affected these variables pre- or postweaning. Plasma urea N was affected by treatments such that the CON group had a lower concentration than forage-fed groups. Forage inclusion, but not physical form, resulted in increased total protein in plasma. Although days with elevated rectal temperature, fecal score, and general appearance were not affected by dietary treatments, calves fed alfalfa hay during the first month of life had fewer days with respiratory issues, regardless of physical form of hay. We concluded that provision of forage does have some beneficial effects in calves fed large amounts of milk replacer, but pelleted alfalfa hay did not result in any improvement in calf performance or health.

Acetate and propionate potentiate the antiproliferative effect of butyrate on RBL-2H3 growth

1. The effect of acetate, propionate, and butyrate separately and combined on RBL-2H3 (a rat basophilic leukemic cell type) proliferation during 24, 48, and 72 hr was examined. Also, the effect of a mixture of the three volatile fatty acids on proliferation of HeLa-155 (a human adenocarcinoma), C57 B1/6J (a mouse melanoma), and MCF-7 (human breast tumor) during 8 days was investigated. 2. Acetate and propionate per se did not present any effect on RBL-2H3 growth during 72 hr, however, when acetate and propionate were added together a significant inhibition of this cell growth was found; 18% for 48 and 37% for 72 hr. The addition of butyrate to the culture medium caused a 75% decrease in the rate of this cell growth either after 48 and 72 hr. This effect of butyrate was pronounced by acetate (86% and 90% for 48 and 72 hr, respectively), propionate (87% for 48 and 93% for 72 hr), and acetate and propionate together (76% for 48 and 92% for 72 hr). 3. Daily addition of a mixture of the short-chain fatty acids (10 mM acetate, 2 mM propionate and 1.5 mM butyrate) markedly decreased the number of cells after 8 days: 58% for RBL-2H3, 42% for HeLa-155, 91% for C57 B1/6J and 55% for MCF-7. 4. These results support the proposition that a fiber-rich diet that leads to great production of butyrate but also of propionate and acetate would be more effective to prevent the occurrence of colorectal cancer than the administration of this short-chain fatty acid given alone.

Fatty acid composition of lymphocytes and macrophages from rats fed fiber-rich diets: a comparison between oat bran- and wheat bran-enriched diets

The effect of oat bran- (OBD) and wheat bran-enriched diets (WBD) on fatty acid composition of neutral lipids and phospholipids of rat lymphocytes and macrophages was investigated. In neutral lipids of lymphocytes, OBD reduced the proportion of palmitoleic acid (48%), whereas WBD reduced by 43% palmitoleic acid and raised oleic (18%), linoleic (52%), and arachidonic (2.5-fold) acids. In neutral lipids of macrophages, OBD increased palmitic (16%) and linoleic (29%) acids and slightly decreased oleic acid (15%). The effect of WBD, however, was more pronounced: It reduced myristic (60%), stearic (24%) and arachidonic (63%) acids, and it raised palmitic (30%) and linoleic (2.3-fold) acids. Neither OBD nor WBD modified the composition of fatty acids in phospholipids of lymphocytes. In contrast, both diets had a marked effect on composition of fatty acids in macrophage phospholipids. OBD raised the proportion of myristic (42%) and linoleic (2.4-fold) acids and decreased that of lauric (31%), palmitoleic (43%), and arachidonic (29%) acids. WBD increased palmitic (18%) and stearic (23%) acids and lowered palmitoleic (35%) and arachidonic (78%) acids. Of both cells, macrophages were more responsive to the effect of the fiber-rich diets on fatty acid composition of phospholipids. The high turnover of fatty acids in macrophage membranes may explain the differences between both cells. The modifications observed due to the effects of both diets were similar in few cases: an increase in palmitic and linoleic acids of total neutral lipids occurred and a decrease in palmitoleic and arachidonic acids of phospholipid. Therefore, the mechanism involved in the effect of both diets might be different.

Propionate modifies lipid biosynthesis in rat peritoneal macrophages

1. This study examines the effect of propionate, normally produced in the gut, on lipid metabolism of resident macrophage. This cell is very abundant in the epithelial lining of the gut. 2. The activity of propionyl-CoA synthetase in macrophages was shown to be 0.39 nmol/min per mg protein, so this cell presents the ability to use propionate. Propionate at concentrations varying from 0.5 to 5 mM did not affect the activities of carnitine acetyltransferase, ATP-citrate lyase, acetoacetyl-CoA thiolase and 3-oxoacid-CoA transferase. 3. Thus this short chain fatty acid did not alter the capacity for transferring acetyl-CoA from mitochondria to cytosol and for ketone bodies formation and oxidation. However, propionate (40 mM) inhibited the incorporation of [1-14C]-palmitate into phospholipids, cholesterol, cholesterol ester and triacylglycerol and the incorporation of [3-14C]-pyruvate into phospholipids. 4. These findings suggest that fibre-rich diet by generating propionate may regulate macrophage lipid metabolism.

The effect of propionate on lipid synthesis in rat lymphocytes

1. The effect of propionate on lipid synthesis in lymphocytes cultured for 24 hr and incubated for 2 hr was investigated. 2. [1-14C]-propionate was incorporated mainly into phospholipids in both control and concanavalin A (Con A) stimulated cultured lymphocytes. 3. The content of free coenzyme A markedly decreased in 2 hr incubated lymphocytes when propionate was added to the medium at concentrations from 10 to 100 mmol/l. 4. Propionate at 40 mmol/l decreased the incorporation of [1-14C]-palmitate into phospholipids (86%), triacylglycerol (87%) and cholesterol ester (98%) and increased in cholesterol (133%) of cultured lymphocytes. 5. Addition of propionate into the culture medium at 2.5 and 5.0 mmol/l concentrations markedly increased the activity of hydrolases of various acylCoA derivatives. 6. The results suggest that propionate may reduce the content of acylCoA and so its esterification and this might be important for the regulation of lymphocytes proliferation.

Nutritional management of plasma lipid disorders

Prevention of vascular disease and acute pancreatitis is the goal of hyperlipidemia treatment. The risk of coronary heart disease (CHD) increases with increasing plasma cholesterol levels because low-density lipoprotein (LDL), the major carrier of cholesterol in the plasma, is atherogenic. High-density lipoprotein (HDL), especially the HDL2 subfraction, protects against CHD. Hypertriglyceridemia, although not an independent risk factor for CHD, is generally accompanied by low HDL cholesterol (HDLch), which may predispose to CHD. Reducing plasma LDL and raising HDL levels are thus goals in preventing CHD. Serum LDL levels may be lowered by reducing saturated fat and cholesterol intake; weight loss may decrease LDL but is more effective in lowering plasma triglycerides and raising HDLch. The percent of total calories from polyunsaturated, monounsaturated, and saturated fats should be less than 10%, up to 10-15%, and less than 10%, respectively. High cholesterol intake increases the flux of cholesterol, which may be harmful to arterial walls, but beyond a certain point does not increase plasma cholesterol levels. Some diets change the composition rather than the level of LDL and apoproteins. Weight reduction and maintenance are the most effective dietary measures to lower plasma triglycerides; omega-3 fatty acids (fish oils) have shown promise in reducing triglyceride but not cholesterol levels. Substitution of starch for sugar lowered triglyceride levels toward normal in hypertriglyceridemia patients. Fasting triglyceride levels rise in all individuals fed high-carbohydrate diets, but the high levels persist in hypertriglyceridemia patients. Weight loss, cessation of cigarette smoking, increased physical activity, good control of diabetes, and moderate alcohol use all raise HDLch levels. Vitamin E deficiency causes neurological sequelae in children with severe malabsorption problems due to abetalipoproteinemia or cholestatic liver disease.

Evaluation of a high-fiber diet in hyperlipidemia: a review

Epidemiologic studies of cardiovascular mortality rates in different countries have suggested that dietary fiber may play a protective role. Within a similar population, a large intake of fiber is associated with a lower relative risk of death from coronary heart disease. Dietary fiber may be separated into at least two types: insoluble, which includes cellulose, hemicellulose, and lignin; and soluble, including pectin and gums. Laxative effects appear to predominate with insoluble fibers such as wheat bran, with little change in plasma lipid levels in most studies. Pectin, guar gum, and oat bran (soluble fibers) have been reported to have hypocholesterolemic effects in both animals and man, with the effect being proportional to the degree of cholesterol elevation. Other gums, specifically those from locust bean and karaya, have a similar effect, with the decrease in total cholesterol due primarily to a decrease in the low-density lipoprotein cholesterol fraction. While some studies have shown continued improvement over a period of months, this has not been uniformly found. Both normal and elevated triglyceride levels appear to be more resistant to change with dietary fiber. An increase of dietary carbohydrate as a source of fiber may be associated with an increase in triglyceride levels. Fiber may, however, offer some protection against an increase in cholesterol and triglyceride levels in subjects fed diets containing large amounts of sucrose. Although rats fed oat bran, guar gum, or pectin had lower levels of hepatic and blood triglycerides, humans with hypercholesterolemia fed oat bran or guar showed no effect on their triglycerides.(ABSTRACT TRUNCATED AT 250 WORDS)

A randomized controlled trial of low carbohydrate and low fat/high fiber diets for weight loss

Among 135 overweight subjects, we conducted a three-month randomized controlled trial of two sets of dietary advice, each providing approximately 1,000 calories per day but differing in fiber, carbohydrate, and fat content. Information on weight and eating habits, as well as measures of lipoprotein and glucose metabolism were obtained at entry and one and three months later. We found that dieters given low carbohydrate/low fiber dietary advice tended to lose more weight than those given a higher carbohydrate/higher fiber regimen (5.0 vs 3.7 kg on average at three months). This pattern was particularly marked among women, and among participants who were under age 40 or of lower social class. There were no differences between the diet groups in the proportion complaining of hunger but, in general, members of the low carbohydrate group complained of more problems in dieting. There were only minor differences in the serum lipoprotein patterns during the diet period. In view of these results, we believe previous claims of the benefits of fiber for weight loss may have been overstated.

Cholesterol binding capacity of fiber from tropical fruits and vegetables

The cholesterol binding capacity of 28 fiber samples from a variety of the more common tropical fruits and vegetables was determined. The binding capacity of cholestyramine, cellulose, lignin, guar gum and citrus pectin were also determined. Capacities were evaluated by an in vitro method that simulates the effect of the human digestive system on fiber using a series of enzymatic treatments before the binding was determined. Binding values varied from 3% for a soluble fraction of cassava to 84% for cholestyramine. Values for most fruit and vegetable fiber samples were less than or ca. equal to cellulose or lignin (20% and 16%, respectively). Apart from cholestyramine, sweet potato was the most effective binder (30%). Citrus pectin, at 8%, was a relatively poor binder. The capacity of guar gum (17%) was slightly less than cellulose. These data do not support the conclusion from in vivo studies that the hypocholesteremic effects observed for citrus pectin and guar gum are the result of the direct binding of cholesterol or bile acids in the large intestine.

Cancerostatic effect of vegetarian diets

A cancerostatic effect of vegetarian diets is proposed on the basis of a selective alteration of the metabolic pathways of fatty acids in neoplastic cells. Most vegetables lack the enzyme 6-desaturase (6D), which converts linoleic to arachidonic acid. Human cells have 6D, and therefore humans do not need to eat the higher polyunsaturated fatty acids found in animal tissues. Many neoplastic cells have lost the activity of 6D. A vegetarian diet would deprive neoplastic cells of higher-chain fatty acids and inhibit the activity of 6D. Without higher-carbon fatty acids, neoplastic cell membranes would have altered fluidity and thus altered transport properties, receptor activity, sensitivity to external molecules, ability to reproduce, resistance to external agents (drugs, radiation, immune defenses, temperature), and overall survival. These alterations would make the cells easier prey for the self-defense of the body or for attack with therapeutic agents. Thus, a vegetarian diet would alter the tumor cell lipid membranes and decrease neoplastic cell survival.