Fatty Acid-rich Diet Research Articles

Effect of excess cholesterol on the protective effect of polyunsaturated fatty acid rich diets during myocardial infarction in conscious rats

Effect of excess cholesterol on the protective effect of polyunsaturated fatty acid rich diets during myocardial infarction in conscious rats

Effects of dietary fats on cardiac performance and substrate utilization in isolated perfused rat hearts

Male rats were fed semi-liquid diets differing by their fatty acids (FA) profiles for 7 days. Hearts were perfused by atrial channel for 45 min. At the end of the perfusion, myocardial levels of glycogen, triglycerides (TG) and phospholipids (PL) were quantified and compared to these of non perfused hearts. The data indicated that a sunflower seed oilrich diet resulted in a marked enhancement of the cardiac performance whereas a (n−3) FA rich diet did not. A poor polyunsaturated FA diet led to a decrease of both aortic flow and cardiac output. Depletions of cardiac glycogen and TG after the perfusion period was the same in all dietary groups. The levels of PL were not affected, except in hearts from rats fed a poor polyunsaturated FA diet. It is therefore concluded that a (n−6) PUFA rich diet promotes the cardiac function. A poor PUFA diet decrease the cardiac performance and could disturb the membrane function.

Influence of dietary linseed oil and sunflower seed oil on some mechanical and metabolic parameters of isolated working rat hearts

The role played by membrane lipid environment on cardiac function remains poorly defined. The polyunsaturated fatty acid profile of myocardial phospholipids could be of utmost importance in the regulation of key-enzyme activities. This study was undertaken to determine whether selective incorporation of n-6 or n-3 fatty acids in membrane phospholipids might influence cardiac mechanical performances and metabolism. For 8 wk, male weaning Wistar rats were fed a semi-purified diet containing either 10% sunflower seed oil (72% C18:2 n-6) or 10% linseed oil (54% C18:3 n-3) as the sole source of lipids. The hearts were then removed and perfused according to working mode with a Krebs-Henseleit buffer containing glucose (11 mM) and insulin (10 Ul/l). Cardiac rate, coronary and aortic flows and ejection fraction were monitored after 30 min of perfusion. Myocardial metabolism was estimated by evaluating the intracellular fate of 1-14C palmitate. Sunflower seed oil and linseed oil feeding did not modify either coronary or aortic flow, which suggests that cardiac mechanical work was not affected by the diets. Conversely, cardiac rate was significantly decreased (-18%; P less than 0.01) when rats were fed the n-3 polyunsaturated fatty acid rich diet. Radioanalysis of the myocardial metabolism suggested that replacing n-6 polyunsaturated fatty acids by n-3 polyunsaturated fatty acids: i) did not alter palmitate uptake; ii) prolonged palmitate incorporation into cardiac triglycerides; iii) reduced beta-oxidation of palmitic acid. These results support the assumption that dietary fatty acids, particularly n-6 and n-3 fatty acids, play an important role in the regulation of cardiac mechanical and metabolic activity.

Effect of excess dietary calcium on colon mucosal membranes and fecal lipids

The objective of the present studies was to examine the biochemical alterations in colon apical membranes upon feeding excess calcium to animals on a saturated fatty acid-rich diet. It has been suggested recently that excess dietary calcium may offer a protection to colon membranes as judged by histologic examination. Sprague-Dawley weanling male rats were fed a semisynthetic diet containing 14% beef fat plus 2% corn oil and either the calcium requirement or excess calcium in the form of calcium carbonate. Animals were fed the diets for 4 weeks. Feces were collected in the last 3 days. The results indicate that excess dietary calcium resulted in alteration in the density of 4 protein bands of colon apical membranes upon examination on SDS-gel electrophoresis. These bands contain 20% of membrane proteins. The diet had no effect on either the lipid content or fatty acid composition of the membranes. Excess dietary calcium resulted in a 54% reduction in fecal water bile acids and a 44% reduction in fecal water free fatty acids. The reduction in fecal water lipids was due to alterations in the solubility of these lipids. This was not mediated through alterations in the pH of fecal water. The observed alterations in protein patterns of these membranes may be due to either the reduction of fecal water bile acids and free fatty acids or may be a direct effect of dietary calcium on membrane proteins.

Dietary fish oil and ischaemic arrhythmias.

Ventricular fibrillation (VF), a serious arrhythmia, is an important cause of death from ischaemic heart disease. There is substantial evidence that experimental diets with a high polyunsaturated (linoleic acid) to saturated fatty acid ratio offer protection against VF. In this article the effects of large amounts of dietary fish oil (up to 30% cal) are reviewed. It is concluded that in all recently published studies marked increases in the incorporation of n-3 fatty acids in membranes was achieved. Two studies were too small, however, to demonstrate any statistically significant difference in VF. The results from a third, a long term feeding study, show a reduction in VF when compared with a highly saturated fat diet, but not when compared to a polyunsaturated fatty acid (n-6) rich diet. Using a more realistic fish oil supplement (0.4% cal) for 8 weeks, we observed a small but nonsignificant reduction in the incidence of VF during acute myocardial ischaemia in the isolated perfused rat heart. The need for further work on the effect of dose, dietary period and confounding influences of saturated fatty acids and linoleic acid are discussed.

Effect of dietary omega-3 and omega-6 fatty acids on development of azaserine-induced preneoplastic lesions in rat pancreas.

We examined the effect of varying the ratio of dietary omega-3 (omega 3) to omega-6 (omega 6) on the development of pancreatic preneoplastic lesions in male Wistar rats given azaserine at 14 days of age. As the ratio of dietary omega 3 to omega 6 fatty acids increased in a diet totaling 20% by weight of fat, the development of preneoplastic atypical acinar cell nodules (AACNs) at 4 months after dosing with azaserine decreased significantly. In addition, serum levels of prostaglandin thromboxane B2, prostaglandin E2, and 6-keto-prostaglandin F1 alpha decreased significantly. The fatty acid composition of the rbc membrane was also significantly influenced by the ratio of dietary omega 3 to omega 6 fatty acids. In a second experiment, we examined the effect of dietary intervention with a different type of fat (corn oil or menhaden oil) 2 months into the 4-month postdosing period on AACN development at the end of the post-dosing period. Intervention of the omega 6 fatty acid-rich diet with the omega 3 fatty acid-rich diet significantly decreased focal development. The opposite was true when intervention involved substituting the omega 3 fatty acid-rich diet with the omega 6 fatty acid-rich diet.

Effects of eicosatetraynoic acid on membrane lipids of trout liver and intestine.

After two months feeding either an (n-3) or an (n-6) fatty acid-rich diet, two groups of trout were switched to the (n-6) or the (n-3) fatty acid-rich diet, respectively. Half of each group was treated with 0.03% 5,8,11,14-eicosatetraynoic acid (ETYA) in the diet. Liver and intestinal brush border membrane lipids were analyzed. No effect was observed on their cholesterol content. ETYA induced an accumulation of 18:2(n-6), and it did not affect the 20:4(n-6) content but decreased the 22:5(n-6) content. ETYA induced an increase of 18:3(n-3) content in the brush border membrane and a decrease of the 22:6(n-3) content in the liver. Those results suggest that ETYA blocks mainly the delta 6-desaturase, which should have two different sites in the liver and one in the intestine.

Dietary Modifications of Phospholipid Composition and Biophysical Properties of the Brush Border Membrane Along the Trout Intestine

Brush border membranes (BBM) are isolated from middle and posterior intestine of trout fed either an essential fatty acid-rich diet or a saturated one. The different phospholipid classes are separated, and their fatty acid composition is determined. Fluorescence anisotropy studies are performed using two lipid fluorophores, namely diphenylhexatriene (DPH) and trimethylamino-diphenylhexatriene (TMA-DPH). The results indicate that the usual parameters affecting the lipid fluidity such as the phospholipid:protein (PL:PROT), cholesterol:phospholipid (CHOL:PL), and sphingomyelin:phosphatidylcholine (SP:PC) ratios and the unsaturation of the acyl chains are sufficient to explain the fluidity values determined using DPH, but not those obtained with TMA-DPH as a probe. This fluorophore is assessed to be localized only in the external leaflet of the membrane. Hence, it will be affected by the composition of the major phospholipids of this leaflet, sphingomyelin and phosphatidylcholine.

Effects of a Polyunsaturated Fatty Acid-Rich Diet on Serum Lipids in Patients with Chronic Renal Failure

An abnormal level of serum lipids may be one of the major risk factors for the development of atherosclerosis in patients with chronic renal failure (CRF). In the present study, the effect of polyunsaturated fatty acid-rich and low carbohydrate diet on serum lipids and HDL-cholesterol was studied in 6 nonnephrotic and nondialyzed patients with CRF on an isocaloric basis. Serum triglycerides decreased significantly from 2.08 +/- 0.93 mmol/l (183 +/- 82 mg/dl) to 1.49 +/- 0.83 mmol/l (131 +/- 73 mg/dl) by consumption of polyunsaturated diet (p less than 0.01). The 'HDL-cholesterol ratio' increased significantly and LCAT decreased on a polyunsaturated diet. In conclusion, the consumption of a polyunsaturated fatty acid-rich diet tends to normalise increased serum triglycerides and lowered 'HDL-cholesterol ratio' in patients with CRF and may be effective for prevention of atherosclerotic vascular sequellae.

Regulation of lipogenic enzymes by dietary unsaturated fatty acids in Ceratitis capitata larvae

1. 1. Enzyme activities of acetyl-CoA carboxylase, fatty acid synthetase, fatty acid chain desaturation and elongation activities as well as the fatty acid incorporation activities into acylglycerols and phosphoglycerides, have been investigated after feeding diets high in either oleic acid or linoleic acid to larvae of the Dipterous Ceratitis capitata. 2. 2. Acetyl-CoA carboxylase and fatty acid synthetase activities were depressed in the larvae fed on the unsaturated fatty acid-rich diets; these enzyme activities were mostly influenced by either linoleic acid or oleic acid, respectively. 3. 3. Both unsaturated fatty acids, mainly linoleic acid, influenced both the desaturation and the elongation of palmitoyl-CoA. Microsomal and mitochondrial desaturation decreased markedly in both nutritional status; microsomal elongation was also decreased in both dietary conditions. 4. 4. The fatty acid incorporation into acylglycerols and phosphoglycerides was mainly modified in the microsomal fraction by the unsaturated fatty acids. The diminution of the incorporation was mainly carried out by the linoleic acid-rich diet.

Changes in cholesterol metabolism In infants in response to dietary cholesterol and fat

The regulation of the serum cholesterol level in infancy is not understood but it has been suggested that it is less precise than in adulthood. Ten infants, ages 3 to 16 months, were studied during two periods of 1 month each, first consuming a low-cholesterol, polyunsaturated fatty acid-rich diet and later a cholesterol containing, polyunsaturated fatty acid-poor diet. Changes in serum cholesterol, bile acid excretion, and net sterol balance (sterol excretion minus cholesterol intake) were measured at the end of each period. The serum cholesterol level rose with the second diet in all infants by from 30 to 111 mg/100 ml. The theoretical response that might be expected in adults to a similar change in cholesterol and fat intake either resembled that, or was not less than that, shown by seven of the infants, while three infants showed a larger than predicted difference in serum cholesterol between the diets. The mean observed and predicted differences in the serum cholesterol level were, respectively, 56 and 58 mg/100 ml suggesting that the magnitude of the response becomes established in early life. Bile acid excretion was significantly higher with dietary polyunsaturated fatty acids, probably explaining some of the effect on the serum cholesterol. The sterol balance data showed that the net sterol balance fell substantially during the consumption of cholesterol in seven of the 10 infants. Although a steady state for cholesterol metabolism is not being claimed for growing infants, the fall in the net sterol balance is strongly suggestive of lessened endogenous cholesterol synthesis as reported in adults.

Membrane lipid fluidity and its effect on the activation energy of membrane-associated enzymes

1. 1. The fatty acid composition of mitochondrial membranes from sheep and rats was altered by feeding these animals diets which were rich in unsaturated fatty acids. Changes in membrane lipid fluidity resulting from the altered membrane lipid composition were assessed by determining the upper temperature limit of the disorder-order transition ( T f ) and the Arrhenius activation energy ( E a ) of succinate oxidase. 2. 2. After feeding the unsaturated fatty acid-rich diet to sheep the E a , in the temperature range above T f , increased from 8 to 63 kJ · mol −1 while T f decreased from 32 to 15°C. Rats fed an unsaturated fatty acid-rich diet exhibited an increase in E a from 17 to 63 kJ · mol −1 and a decrease in T f from 23 to 4°C. 3. 3. This decrease in T f was related to an increase in the ratio of linoleic acid to stearic acid in the membrane lipid. T f was not related to the proportion of unsaturated fatty acids in the membrane lipids, although an increase in unsaturation usually led to a decrease in T f . 4. 4. The results show that membrane lipid fluidity has a direct influence on the conformation of the active site of some membrane-associated enzymes, with the result that such enzymes display a higher E a when the membrane lipids are comparatively more fluid. The increase in E a of membrane-associated enzymes which accompanies changes in the physical state of membranes suggests that some proteins may phase separate with the more fluid lipids at low temperatures.