The influence of dietary fat and protein on the aging hamster: Hemoglobin,glucose, triglycerides,and serum proteins

Hamsters were fed one of three levels of casein (9, 18, and 36 g/385 Kcal) combined with one of three levels of corn oil (4.5, 9.0, and 18.0 g/385 Kcal) from 8 weeks of age. Blood samples were collected 2, 5, 11, and 17 months after animals began to receive the various diets. Whole blood hemoglobin was highest in animals fed the high-protein diets at the 5-and 11-month measurements, but also high in animals fed the medium-protein diet at the 17-month measurement. The medium-and high-fat diets resulted in the highest hemoglobin values. Serum triglycerides and plasma glucose were elevated in hamsters fed high-fat or high-protein diets at nearly every collection period. Each serum protein fraction was influenced differently by the diets. Increasing dietary fat and/or protein increased serum albumin. Serum alpha one globulin was elevated in hamsters of both sexes fed high-fat diets. In contrast, low-protein diets reduced the concentration of this fraction in males only. Beta globulins were influenced by dietary fat. At 5 and 17 months, high-fat diets elevated this fraction, but at 11 months depressed it. Gamma globulins were elevated by feeding high-fat diets to female hamsters. The age and sex of hamsters are influential in determining their responses to different diets.     

Nutritional effects on the lifespan of Syrian hamsters

Syrian hamsters were fed one of nine semipurified diets composed of three casein levels (9, 18, and 36 g/385 Kcal), with each of three corn oil levels (4.5, 9.0, and 18.0 g/385 Kcal). These diets were given either for five weeks and were followed by control diet (18 g casein and 9 g corn oil/385 Kcal) or control diet was fed for the first five weeks and was followed by the nine diets. Calorie consumption, maximum body weight and length of growth period and of life are reported. Calorie consumption was directly related to dietary fat levels. Maximum body weights increased with increasing dietary fat and protein when the various diets were fed during weeks 1–5. This result was not due to a conditioning of the animals fed high-fat or high-protein levels during weeks 1–5 to consume more calories after week 5, since after this time consumption was the same in all groups fed the control diet. When diets were fed from week 6 body weight increased in both sexes with increased dietary fat; however, higher dietary protein increased female and decreased male maximum body weight. Males took longer to reach these maximum weights than females, and were not affected by receiving the various diets during weeks 1–5. However, when diets were fed from week 6 until death, the growth period increased with higher dietary fat or protein. Male hamsters survived longer than females with each experimental treatment. Animals fed low-fat, low-protein diet or high-fat, high-protein diet during the first 5 weeks of the study survived longest. When diets were fed from 6 weeks until death, survival increased as dietary fat rose for both sexes. In contrast, survival improved as dietary protein rose for females or decreased for males. These studies establish a basis for further investigations on the link between nutrition and longevity in the Syrian hamster.     

Metabolic and hormonal investigations in long-term streptozotocin diabetic rats on different dietary regimens

Summary Groups of diabetic rats (65 mg/kg streptozotocin SC) were fed ad lib on three different dietary regimens for 43 weeks: a standard control diet (68% of calories as carbohydrate, 20% as protein, and 12% as fat), a low carbohydrate high protein diet (6% carbohydrate, 63% protein, 31% fat) or a low carbohydrate-high fat diet (5% carbohydrate, 75% fat, 20% protein). The high fat diet resulted in a fall of blood glucose from 700 to 350 mg/100 ml. Rats fed the high protein diet showed a similar initial decrease in blood glucose concentration, and a further improvement was evident from the 28th week on. After 43 weeks blood glucose levels were below 180 mg/100 ml and glycosuria below 100 mg/24 h in all rats fed the high protein diet. When rats exhibiting blood glucose levels below 180 mg/dl were transferred temporarily to standard diet blood glucose levels increased and marked glycosuria was observed. Rats on the standard diet maintained blood glucose concentrations greater than 500 mg/100 ml and glycosuria of about 16 g/24 h throughout the experiment. The pancreatic insulin content at death of rats fed the standard diet or the high fat diet was 1% of normal rats, whereas the values for the rats on the high protein diet were increased to 9%. Animals fed the low carbohydrate diets showed greater weight gain. In the high fat diet group there was a marked rise after 43 weeks in plasma triglycerides, free fatty acids, 3-hydroxybutyrate and acetoacetate in the plasma. Urea excretion was raised in the animals on the high protein diet. Thus, treatment with low carbohydrate diets for 10 months regardless of fat and protein content markedly improved the diabetic state of rats.     

Varied effects of dietary sucrose and cholesterol on serum lipids, lipoproteins and apolipoproteins in rhesus monkeys.

Serum lipid, lipoproteins, apolipoproteins and plasma insulin and glucose were studied in rhesus monkeys (Macaca mulatta) fed high sucrose diets (69%, w/w), with and without added cholesterol. When compared to basal diet, a high sucrose diet with no added cholesterol fed for 6 weeks increased serum total cholesterol and triglycerides by factors of 1.2 and 2.8, respectively. Cholesterol supplementation of sucrose diets increased the serum total cholesterol levels by a factor of 2.2 and decreased the serum triglycerides by 0.47. The serum cholesterol response to experimental diets was reflected predominantly in beta-lipoprotein and to a lesser extent in alpha-lipoprotein. Sucrose diets without cholesterol enriched the beta- and pre-beta-lipoproteins with triglycerides and protein at the expense of cholesterol. On the same diet, the protein content of alpha-lipoprotein increased at the expense of cholesterol and triglycerides. In contrast, dietary cholesterol decreased the triglyceride content and increased the cholesterol content of all the lipoprotein classes. Sucrose feeding seems to increase ApoB more than non-ApoB proteins. The proportion of ApoC-II relative to ApcoC-III increased in each animal on a sucrose diet; exogenous cholesterol further increased this trend. While sucrose diet decreased ApoA-I/ApoA-II ratios, cholesterol supplementation reversed this trend. Dietary sucrose increased the plasma glucose, insulin, and insulin-glucose ratios. The addition of cholesterol also tended to decrease plasma glucose and insulin levels. These observations indicate varied responses of serum lipoproteins and apoproteins to dietary sucrose with and without cholesterol supplementation.     

Experimental atherosclerosis in rabbits fed cholesterol-free diets. 13. Interaction of proteins and fat

The atherogenic and cholesterolemic effects of animal protein vis-a-vis plant protein are well documented. Virtually all the studies were carried out using diets high in saturated fat, such as coconut oil. In order to determine if the same effects were seen with less saturated fat, we have compared atherogenic effects of an animal protein (casein) with those of a plant protein (soybean protein isolate) fed with partially hydrogenated soybean oil (PHS) (iodine value 72) or soybean oil (iodine value 134) as part of a cholesterol-free semipurified diet. After 6 months only rabbits fed casein-PHS exhibited elevated levels of plasma and liver cholesterol and triglycerides and atherosclerosis. Rabbits fed soy protein-PHS had slightly higher plasma cholesterol and triglycerides than did those fed soy protein and soybean oil, but values in both groups were in the normal range. The different effects of animal and plant protein on lipidemia and atherosclerosis can be influenced by dietary fat and appear to be dependent on fat saturation.     

Mechanism of carbohydrate-induced hypertriglyceridemia: Plasma lipid metabolism in mice

A group of mice were fed on a basal diet for 2 wk and thereafter maintained on a fat free high sucrose or starch diet for 5–6 wk. Hypertriglyceridemia was induced in the mice on feeding the high carbohydrate diets. The triglyceride levels reached maximum in 12 and 14–18 days on high sucrose and starch diets, respectively. This was associated with increased pre-β-lipoproteins in plasma. Though males had higher levels of triglycerides than females on both the diets, this attained statistical significance only in the sucrose-fed group. Cholesterol and phospholipids recorded a significant increase only towards the end of the experimental period. The plasma lipid levels correlated well with their secretion rates from the liver following an injection of Triton WR 1339. Futhermore, the hypertriglyceridemia appeared to be due to defective plasma triglyceride removal as seen by the reduced postheparin lipolytic activity (PHLA) of plasma and decreased triglyceride removal (intravenous fat tolerance test) in these animals. The triglycerides returned to almost normal levels when feeding was continued on the diets. During this adaptation, PHLA and fat tolerance of animals increased significantly. Higher triglycerides in the sucrose group seem to be due to a higher rate of secretion as well as slower removal of triglycerides in this group. The sex difference noticed in the plasma triglycerides at peak hypertriglyceridemia appeared to be mainly due to sex difference in removal rates. Blood sugar raised significantly in the animals maintained on both the diets.     

The effect of dietary cellulose on life span and biochemical variables of male mice

Sixteen month old C57BL/6J male mice were fed either a nutritionally adequate diet or this diet diluted with either 33% or 50% cellulose. The life span of the animals fed the latter two diets was longer than that of the controls, but only statistically significant in the animals fed the diet diluted with 50% cellulose. The rates of cellular protein synthesis were estimated in liver by determining: 1) the half lives of proteins by the rate of disappearance of radioactivity following the intraperitoneal injection of C¹⁴ labeled sodium bicarbonate, and 2) the cellular protein levels estimated by the concentration of proteins and DNA of the tissue. The rates of disappearance of radioactivity from the liver proteins of mice were not statistically significantly affected by these dietary regimens. However, there was a 27% decrease in the cellular protein synthesis of liver in the animals fed the diets containing cellulose.     

Metabolic effects induced by long-term feeding of medium-chain triglycerides in the rat

Energy intake, weight gain, carcass composition, plasma hormones and fuels, hepatic metabolites and the activities of phosphoenolpyruvate carboxykinase (PEPCK), malic enzyme, and glucose 6-phosphate dehydrogenase (G6P-DH) were examined in adult rats during a 44-day period of low fat, high carbohydrate (LF) feeding or of consumption of one or two high (70% metabolizable energy) fat diets composed of 63% (metabolizable energy) long-chain (LCT) or medium-chain (MCT) triglycerides. Energy intake was similar in the LCT and MCT groups but was less than that of LF group. The weight gain of rats fed MCT diet was 30% less than that of rats fed LF or LCT diets. Energy retention was less when the diet provided MCT than LCT or LF, and that resulted in a 60% decrease in the daily lipids deposition. Plasma glucose, free fatty acids, glycerol, and insulin/glucagon ratio were similar in the three groups. Blood ketone body (KB) concentrations in rats fed the high fat diets were extremely elevated, particularly in the MCT group, but declined throughout the experiment and by the 44th day hyperketonemia decreased by 50% but remained higher than in the LF diet. The blood beta-hydroxybutyrate/acetoacetate (B/A) ratio remained slightly elevated in rats fed the high fat diets. Similar changes were observed in liver KB concentration and in the B/A ratio. Liver lactate/pyruvate ratio elevated in the LCT and MCT groups at the initiation of the diets decreased by 50% at the end of the experiment. The consumption of high fat diets led to a 1.5-fold increase in liver PEPCK activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

High-monounsaturated fat, olive oil-rich diet has effects similar to a high-carbohydrate diet on fasting and postprandial state and metabolic profiles of patients with type 2 diabetes

Whether metabolic control in type 2 diabetes mellitus (DM) is best achieved with the traditional high-carbohydrate (CHO), low-fat diet or a low-CHO, high-fat diet is still controversial. In a randomized crossover study, we compared the effects of a low-fat (30% of daily energy) diet and a high-fat (40% of daily energy), high-monounsaturated-fat diet for 6 weeks each on fasting and postprandial glucose, insulin, and lipoprotein concentrations in 12 patients with well-controlled type 2 DM (fasting blood glucose, 176 +/- 54 mg/dL; hemoglobin A1c, 6.4% +/- 0.7%) and no overt dyslipidemia (serum total cholesterol, 235 +/- 43 mg/dL; triglycerides, 180 +/- 63 mg/dL). Home-prepared foods were used and olive oil was the main edible fat, accounting for 8% and 25% of daily energy requirements in the low-fat and high-fat diets, respectively. For postprandial studies, the same mixed meal containing 36% fat was used in both dietary periods. Body weight and fasting and 6-hour postprandial blood glucose, insulin, and lipoprotein levels were similar after the two diets. The mean incremental area under the curve of serum triglycerides 0 to 6 hours after the challenge meal, adjusted for baseline levels, did not change significantly after the high-fat diet compared with the low-fat diet (1,484 +/- 546 v 1,714 +/- 709 mg x 6 h/dL, respectively, P = .099). Mean postprandial triglyceride levels at 6 hours were increased about 2 times over fasting levels and were still greater than 300 mg/dL after either diet. A diet high in total and monounsaturated fat at the expense of olive oil is a good alternative diet to the traditional low-fat diet for patients with type 2 DM. However, ongoing postprandial hypertriglyceridemia with either diet points to the need for other therapies to decrease triglyceride-rich lipoproteins (TRL) and the inherent atherogenic risk in type 2 diabetics.     

Dietary protein, fat, and minerals in nephrocalcinosis in female rats.

Young female rats fed semipurified diets containing casein or a soy protein isolate had extensive nephrocalcinosis at the junction between the outer and inner stripe of the outer medullary zone after 5 wk on the diets, whereas rats fed a diet containing a lactalbumin concentrate did not. Although the percentages of actual protein and of total ash were similar in all three diets, the concentrations of individual minerals were not, owing to methods used in isolating the proteins. Comparison of the individual mineral contents of these diets with those in other laboratories as compiled from the literature suggested that factors other than minerals, including protein, are also implicated. Dietary fat appeared to be another such factor in a series of experiments in which saturated medium-chain triglycerides and corn oil were included in diets containing soy protein isolate. Although these diets had identical mineral compositions, the rats fed medium-chain triglycerides had less severe lesions.     

Effects of dietary fish oil and butterfat on serum lipids and monocyte and platelet interactions with aortic endothelial cells

We studied effects of dietary lipids on some of the initial events in atherogenesis. Adult swine were fed low fat/low cholesterol diets, then challenged with a high cholesterol (1%, w/w) diet supplemented with 11.5% (w/w) butterfat (BF) or MaxEPA^TM fish oil (FO). Serum lipids and monocyte and platelet adhesion to porcine aortic endothelial cells in vitro were measured during feeding of the low fat diet and at 1, 2, and 5 weeks after the dietary challenge. Total cholesterol increased significantly in animals fed the BF and FO diets, but there was no difference between the groups. Animals fed FO had total cholesterol/high-density lipoprotein cholesterol values twice those fed BF ( ). After 2 weeks on the hypercholesterolemic diet, monocyte adhesion to endothelial cells increased in swine fed FO by 123% above those fed a low fat diet, and adhesion values remained elevated (56% above baseline value) after 5 weeks. Monocytes from swine fed BF showed increased adhesion by 87, 53, and 14% above those fed the low fat diet at 1, 2, and 5 weeks respectively. Platelet adhesion to endothelial cells decreased (P < 0.05) after diet change and remained low. Adhesion of platelets from swine fed FO was significantly lower than those fed BF at 1 and 2 weeks but higher at 5 weeks. The FO diet, compared to the BF diet, produced a more atherogenic cholesterol profile and greater monocyte adhesion to endothelial cells, conditions which in vivo may promote lesion initiation.     

Should we recommend low‐fat diets for obesity?

Dietary fat intake has been blamed for the increase in adiposity and has led to a worldwide effort to decrease the amount of fat in the diet. However, the comparative efficacy of this approach is debatable. Whilst short‐term dietary intervention studies show that low‐fat diets lead to weight loss in both healthy and overweight individuals, it is less clear if a reduction in fat intake is more efficacious than other dietary restrictions in the long term. The purpose of this systematic review was to determine the effectiveness of low‐fat diets in achieving sustained weight loss when used for the express purpose of weight loss in obese or overweight people. A comprehensive search identified six studies that fulfilled our criteria for inclusion (randomized controlled trial, participants either overweight or obese, comparison of a low‐fat diet with another type of weight‐reducing diet, follow‐up period that was at least 6 months in duration and inclusion of participants 18 years or older without serious disease). There were a total of 594 participants in the six trials. The duration of the intervention varied from 3 to 18 months with follow‐up from 6 to 18 months. There were no significant differences between low‐fat diets and other weight‐reducing diets in terms of sustained weight loss. Furthermore, the overall weight loss at the 12–18‐month follow‐up in all studies was very small (2–4 kg). In overweight or obese individuals who are dieting for the purpose of weight reduction, low‐fat diets are as efficacious as other weight‐reducing diets for achieving sustained weight loss, but not more so.     

Development of compensatory thermogenesis in response to overfeeding in hypothyroid rats.

Intact or surgically thyroidectomized (Tx) adult male Wistar rats, weighing 150-200 g, were fed a standard chow diet (approximately 1.8 Cal/g) or a high calorie (approximately 3.8 Cal/g) diet (cafeteria diet) for up to 30 days. Daily energy intake was about 5-fold higher in the rats fed the cafeteria diet regardless of their thyroid status. The cafeteria diet caused the retroperitoneal white fat pad to increase by approximately 2-fold, the volume of isolated white adipocytes to increase by 2-fold, and the total body fat to increase by a factor of approximately 3, again regardless of thyroid status. It also increased basal metabolic rate by about 20% in intact rats and by about 50% in Tx rats. The brown fat thermal response to norepinephrine (NE) infusion was approximately 2-fold increased in the intact rats fed the cafeteria diet. However, in the Tx rats, the brown fat thermal response to NE was blunted regardless of the dietary regimen adopted. In both intact and Tx rats, the cafeteria diet increased total brown fat mitochondria, uncoupling protein percentage, and total brown fat uncoupling protein by about 3-, 2-, and 5-fold, respectively. Serum leptin levels also increased approximately 4-fold in intact rats fed the cafeteria diet. However, in Tx rats, leptin levels did not change significantly during overfeeding. In conclusion, hypothyroidism caused the brown fat to become unresponsive to NE, even after 1 month on the cafeteria diet. However, these rats were able to increase basal metabolic rate and, as assessed by several different parameters, did not gain fat beyond that observed in intact controls kept on a similar overfeeding schedule.     

Effects of different levels of dietary fat on methyl-nitrosourea-induced mammary carcinogenesis in correlation with parameters of fat metabolism in female Sprague-Dawley rats

The aim of this study was to elucidate the effects of different levels of dietary fat on methyl-nitrosourea-induced rat mammary carcinogenesis in correlation with parameters of the fat metabolism. 90 female Sprague-Dawley rats were initiated i.v. with 25 mg MNU/kg on day 50 of life. For a period of 6 months, beginning after the day of initiation, the animals received either a control diet (12% of total energy as fat, Group I) or one of the fat-enriched semisynthetic diets (25 en% of fat, Group II, or 45 en%, Group III, respectively) at an isocaloric level of 50 kcal/rat/day. The principal observations of this experiment were: (1) The fat content of diet did not significantly influence mammary carcinogenesis. (2) The values of plasma total lipids, cholesterol and triglycerides and their density separated VLDL and LDL-fractions showed a significant time-dependent increase. (3) HDL-values of cholesterol and triglycerides showed no changes in dependence to time and fat content of the diet. (4) The liver lipid concentrations of groups increased significantly with dietary fat content.     

Compositional changes in serum lipoproteins during developing hypercholesterolemia induced in rabbits by cholesterol-free, semipurified diets

Changes in the concentration and composition of serum very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL) were studied in rabbits transferred from chow diet to cholesterol-free, semipurified diets containing casein or isolated soy protein. The fat and fibre content of these diets was similar to that of chow but a higher protein level was used to enhance the hypercholesterolemia. During the first week on the casein diet, there was a marked increased in LDL-cholesterol, protein and phospholipids, and these higher levels were maintained during the subsequent 3 weeks of the study. Similar but less marked changes were obtained with the soy protein diet. The components of VLDL showed relatively little change after introduction of the diets to the animals. In both VLDL and LDL, the proportion of cholesterol increased and that of triglycerides decreased after 1 week on the casein diet and a similar trend was seen in HDL. The concentration of HDL-cholesterol showed little change but triglycerides, protein and phospholipids all tended to decline on both casein and soy protein diets.     

Effect of Ethanol on Maternal and Offspring Characteristics: Comparison of Three Liquid Diet Formulations Fed during Gestation

Maternal blood alcohol levels, weight gain during pregnancy, parturition time, perinatal mortality, and postnatal growth of offspring were compared in groups of pregnant rats fed one of three ethanol-containing liquid diets (Kahn's formula = BSA diet, Revised Wiener's = RA6 diet, and Lieber-DeCarli's high protein 82C diet = LDA diet). The three ethanol diets all contained the same amount of ethanol-derived energy (36% of total energy), but differed in the amount of energy contributed by protein (17, 30, and 25%), fat (36, 24, and 13%), and carbohydrate (12, 10, and 27%), respectively. The experimental design also included dams that were pair-fed isocaloric ethanol-free versions of the three ethanol diets (designated BSP, RP6, and LDA, respectively) and a group of dams fed a pelleted casein-based solid diet (PC diet). All experimental diets were fed ad libitum from gestational day 7 to delivery. The effect of ethanol exposure in utero was most severe in mothers and offspring fed the BSA diet. The feed efficiency ratio (maternal weight gain/total dietary energy consumed) of this low-protein ethanol diet was less than that of RA6 or LDA diets. The feed efficiency ratio calculated for RA6 and LDA diets was not different from that of PC diet. Compared with rats fed RA6 and LDA diets, the rats that were fed BSA diet exhibited deficient maternal weight gain, greater parturition delay, impaired fetal growth, and increased perinatal mortality among the offspring. BSA dams had the highest blood ethanol levels of all groups fed ethanol diets, and exhibited the least difference in blood ethanol concentrations between the day (2 PM) and night (9 PM) periods of the diurnal cycle.(ABSTRACT TRUNCATED AT 250 WORDS)     

Early growth restriction, membrane phospholipid fatty acid composition, and insulin sensitivity

An animal model of protein restriction during pregnancy and lactation with subsequent dietary fatty acid manipulation was used to investigate the association between poor early growth, defective unsaturated fatty acid handling, and later disease. Both control and early growth-restricted animals fed a diet rich in saturated fatty acids showed a doubling of the plasma insulin levels as well as a reduced degree of unsaturation in liver and skeletal muscle membrane phospholipids compared with animals fed diets rich in unsaturated fatty acids. The skeletal muscle of early growth-restricted animals weaned onto a saturated fat diet had reduced proportions of 22:6n-3 and increased proportions of 18:1n-9. This reduction in 22:6n-3 is similar to that observed in Pima Indians, a population with a high prevalence of type 2 diabetes.     

Dietary antioxidants preserve endothelium dependent vasorelaxation in overfed rats

OBJECTIVE: A high fat diet contributes to obesity and acutely impairs endothelium dependent vasorelaxation. While a high cholesterol diet chronically impairs endothelium dependent vasorelaxation in rabbits, this model is associated with severe hypercholesterolemia. The effect of chronic high fat feeding on endothelial function in the setting of more normal lipid levels has not been studied. Our aim was to study vascular function in rats overfed for 6 months and to determine the role of oxidative stress in the alteration of vascular function associated with this diet. METHODS: Forty-five male Sprague-Dawley rats were placed on the following diets for 6 months, control diet, high fat diet or high fat diet supplemented with vitamins A, E and selenium. Six months later blood samples were collected and vascular function was assessed in the aorta. RESULTS: The rats fed a high fat diet were heavier than controls (608.4 +/- 41.8 vs. 700.3 +/- 50.1 vs. 699.5 +/- 52.6 g, P<0.05 for control vs. high fat and high fat plus antioxidant groups) but lipid levels were similar in each group (cholesterol, 145.9 +/- 53.4 vs. 140.5 +/- 44.0 vs. 152.7 +/- 36.1 mg/dl and triglycerides, 173.2 +/- 106.7 vs. 197.4 +/- 131.3 vs. 166.1 +/- 65.3 mg/dl, P, NS). Relaxations to acetylcholine and calcium were significantly impaired in the high fat diet group compared with controls (EC(50), 6.90 +/- 0.22, 7.12 +/- 0.32; AUC, 96.9 +/- 51.6, 155.5 +/ - 73.7) but were not different between the antioxidant supplemented group and controls (EC(50), 7.06 +/- 0.37; AUC, 151.9 +/- 67.4). Relaxations to DEA NONOate were similar in each group. CONCLUSIONS: Dietary antioxidants preserved endothelium dependent vasorelaxation in rats fed a high fat diet for 6 months.     

Metabolic effects of dietary stearic acid in mice: changes in the fatty acid composition of triglycerides and phospholipids in various tissues.

The fatty acid patterns of triglycerides and phospholipids extracted from adipose tissue, liver, heart, kidney, spleen, and lung of 3 groups of C57BL/6 mice were determined after feeding diets rich in palmitic acid (16:0) (high palmitic: 16:0 = 45.1% of total fatty acids), stearic acid (18:0) (high stearic: 18:0 = 42.9% of total fatty acids) and oleic acid (18:1) (high oleic: 18:1 = 79.7% of total fatty acids) for 9 months. Triglyceride content of adipose, liver, heart, kidney, lung and spleen tissues was significantly enriched in palmitic acid in mice fed the high palmitic diet (range among all tissues: 19.9% +/- 0.2% to 29.0% +/- 1.9% of total fatty acids) and in oleic acid in mice fed the high oleic diet (range 56.0% +/- 1.9% to 71.6% +/- 1.2%). The stearic acid content of organ triglycerides in mice fed the high stearic diet ranged from 3.7% +/- 0.3% to 10.8% +/- 1.2%; however, the content of oleic acid on this diet (range: 57.0% +/- 1.8% to 71.4% +/- 1.7%) was similar to the one observed in mice fed the high oleic diet. In all organs, phospholipids had a significantly higher percentage of stearic acid (range: 23.5% +/- 0.9% to 51.5% +/- 6.6%) than triglycerides, regardless of diet. To evaluate the production of oleate from stearate and palmitate, 2 groups of mice were fed the high palmitic and the high stearic diets for 1 week and then injected intravenously with [1-14C]palmitate and [1-14C]stearate and the amount of labelled oleate in liver triglycerides was measured.(ABSTRACT TRUNCATED AT 250 WORDS)     

An unsaturated fat diet prevents the increased angiotensin II vascular responses in renal artery stenosis.

OBJECTIVE: The aim was to characterise angiotensin II constrictor responses in two kidney, one clip (2K1C) renal hypertensive rats fed a diet with a high unsaturated fatty acid content. METHODS: Two diets with the same total fat (37% by energy; 17% by weight) but different unsaturated fat contents were fed to rats for a three month period. Thirty four Sprague Dawley rats were used per diet group. After one month on the diets, a group of 19 rats in each diet group was operated upon to induce 2K1C hypertension. A separate group of 15 rats within each diet group received sham operations. Systolic blood pressure was measured weekly from prior to surgery to the end of the three month feeding period. At three months, angiotensin II constrictor responses were evaluated in the isolated kidney vascular preparation and in intact anaesthetised rats fed the different diets. Phenylephrine constrictor responses were also evaluated in intact anaesthetised rats in order to exclude structural vascular changes accounting for differences in angiotensin II constrictor responses. RESULTS: The diet high in unsaturated fats prevented the development of hypertension in 2K1C rats [systolic pressure 134(7) mm Hg at eight weeks] compared to their own preoperative blood pressures [124(3) mm Hg], and to the 2K1C rats fed the control diet [163(7) mm Hg at eight weeks]. The diet high in unsaturated fats did not alter blood pressures in sham operated rats. In isolated perfused kidneys and in anaesthetised 2K1C rats fed the control diet, angiotensin II caused a greater vascular response compared to the sham operated groups. The unsaturated fat diet prevented this effect. No differences were found in blood pressure responses to phenylephrine. CONCLUSIONS: These data suggest that the antihypertensive effect of a high unsaturated fat diet may in part be due to a depressed responsiveness of vascular smooth muscle to endogenous angiotensin II. The effect is likely to be due to modulation of angiotensin II vascular responses by local vascular changes that cannot be accounted for by structural vascular differences.