Oxidative stress and antioxidant status in rat blood, liver and muscle: effect of dietary lipid, carnitine and exercise

The purpose of this study was to determine the effect of dietary fat, carnitine supplementation, and exercise on oxidative damage and antioxidant status. Male Wistar rats (60 days old) were fed diets containing either hydrogenated fat (HF) or peanut oil (PO) with or without 0.5 mg % (of dry diet) carnitine. The rats were given exercise, i.e. swimming for 60 minutes, for 6 days/week for 6 months under each dietary condition. The blood malondialdehyde (MDA) level was higher in PO-fed rats, more so in exercising ones, while the same was not altered in carnitine-supplemented rats irrespective of the dietary fat or physical activity. The MDA level was significantly decreased in muscle, while increased in liver, of carnitine-fed rats. The blood glutathione (GSH) level also significantly increased in exercising rats as compared to sedentary ones, while carnitine supplementation elevated it in all the groups. Exercise and carnitine supplementation significantly lowered GSH levels in liver while increasing it in muscle. The glutathione peroxidase (GPX) activity was significantly increased in blood and muscle from PO-fed exercising rats as compared to sedentary ones, while carnitine supplementation elevated GPX activity in all the groups. The liver and muscle catalase (CAT) activities were significantly increased in PO-fed exercising rats, while carnitine did not have any effect. The pro-oxidative effect of the monounsaturated fatty acid (MUFA)-rich PO diet and prolonged regular exercise was less pronounced due to augmented antioxidant enzymes, GPX and CAT, induced by training to protect against the oxidative stress, while carnitine supplementation could help to counter lipid peroxidation due to exercise through redistribution of GSH from liver to blood and muscle.     

Regular exercise modulates muscle membrane phospholipid profile in rats.

We investigated the effect of regular exercise and changes in dietary fatty acid profile on skeletal muscle phospholipid fatty acid profile in rats. Rats were randomly divided into three groups and for 4 wk fed either a carbohydrate-rich diet (CHO, 10 percent of total energy (E%) fat, 20 E% protein, 70 E% CHO) or one of two fat-rich diets (65 E% fat, 20 E% protein, 15 E% CHO) containing predominantly either saturated or monounsaturated fatty acids. Each dietary group was randomly assigned to a trained (6 d/wk, progressive to 60 min, 28 m/min at a 10 degrees incline) or a sedentary group. The effect of training was apparent in the three hindlimb muscles analyzed: red quadriceps, white quadriceps and soleus. The unsaturation index was significantly lower in the trained than in the sedentary groups (206 +/- 2 vs. 215 +/- 2, P < 0. 01), which largely reflected a lower content of arachidonic acid [20:4(n-6): 14.5 +/- 0.5 vs. 16.6 +/- 0.4% of total fatty acids, P < 0.01] and docosahexaenoic acid [22:6(n-3): 11.1 +/- 0.2 vs. 11.7 +/- 0.3% of total fatty acids, P < 0.03] and a concomitant higher content of linoleic acid [18:2(n-6): 20.0 +/- 0.4 vs. 17.8 +/- 0.4% of total fatty acids, P < 0.01]. Training affected skeletal muscle membrane structural composition, and this occurred independently of dietary fatty acid changes. This change likely reflects an increased utilization of highly unsaturated fatty acids for energy, an effect which may have deleterious effects on insulin action.     

Dietary Carbohydrate as Glycemic Load,Not Fat,Coupled with Genetic Permissiveness Favoring Rapid Growth and Extra Calories,Dictate Metabolic Syndrome and Diabetes Induction in Nile Rats (Arvicanthis niloticus)

Objective: Whether dietary carbohydrate (CHO) or fat is more involved in type 2 diabetes (T2DM) induction uncomplicated by dietary fiber was addressed in a spontaneous diabetic model, the diurnal Nile rat that mimics the human condition. Methods: A total of 138 male Nile rats were fed plant-based and animal-based saturated fat where 10% energy as CHO and fat were exchanged across 5 diets keeping protein constant, from 70:10:20 to 20:60:20 as CHO:fat:protein %energy. Diabetes induction was analyzed by: 1. diet composition, i.e., CHO:fat ratio, to study the impact of diet; 2. quintiles of average caloric intake per day to study the impact of calories; 3. quintiles of diabetes severity to study the epigenetic impact on diabetes resistance. Results: High glycemic load (GLoad) was most problematic if coupled with high caloric consumption. Diabetes severity highlighted rapid growth and caloric intake as likely epigenetic factors distorting glucose metabolism. The largest weanling rats ate more, grew faster, and developed more diabetes when the dietary GLoad exceeded their gene-based metabolic capacity for glucose disposal. Diabetes risk increased for susceptible rats when energy intake exceeded 26 kcal/day and the GLoad was >175/2000 kcal of diet and when the diet provided >57% energy as CHO. Most resistant rats ate <25 kcal/day independent of the CHO:fat diet ratio or the GLoad adjusted to body size. Conclusion: Beyond the CHO:fat ratio and GLoad, neither the type of fat nor the dietary polyunsaturated/saturated fatty acid (P/S) ratio had a significant impact, suggesting genetic permissiveness affecting caloric and glucose intake and glucose disposition were key to modulating Nile rat diabetes. Fat became protective by limiting GLoad when it contributed >40% energy and displaced CHO to <50% energy, thereby decreasing the number of diabetic rats and diabetes severity.     

Effects of diets rich in monounsaturated fatty acids on plasma lipoproteins--the Jerusalem Nutrition Study. II. Monounsaturated fatty acids vs carbohydrates.

Seventeen male Yeshiva students were randomly allocated to a crossover study with two 12-wk dietary periods of monounsaturated fatty acids (MUFAs) vs a carbohydrate (CHO)-rich diet while concentrations of saturated (SFAs) and polyunsaturated (PUFAs) fatty acids were kept similar. Total plasma cholesterol (TC) decreased significantly by approximately 7.7% and low-density-lipoprotein cholesterol (LDL-C) by 14.4% on the MUFA diet, whereas on the CHO diet no significant change in cholesterol concentrations occurred, in contrast to that predicted by the equations of Keys and Hegsted. Concentrations of high-density-lipoprotein cholesterol (HDL-C) did not change significantly on either diet. On the MUFA diet there was a significantly lower proneness to peroxidation of plasma and LDL lipids and less extensive metabolism of conditioned LDL by peritoneal macrophages. We conclude that dietary MUFAs lower TC and LDL-C concentrations, independently of other dietary fatty acids and in addition may reduce the susceptibility of LDL to oxidative stress.     

High-fat diet versus habitual diet prior to carbohydrate loading: effects of exercise metabolism and cycling performance

We examined the effects of a high-fat diet (HFD-CHO) versus a habitual diet, prior to carbohydrate (CHO)-loading on fuel metabolism and cycling time-trial (TT) performance. Five endurance-trained cyclists participated in two 14-day randomized cross-over trials during which subjects consumed either a HFD (> 65% MJ from fat) or their habitual diet (CTL) (30 +/- 5% MJ from fat) for 10 day, before ingesting a high-CHO diet (CHO-loading, CHO > 70% MJ) for 3 days. Trials consisted of a 150-min cycle at 70% of peak oxygen uptake (VáO2peak), followed immediately by a 20-km TT. One hour before each trial, cyclists ingested 400 ml of a 3.44% medium-chain triacylglycerol (MCT) solution, and during the trial, ingested 600 ml/hour of a 10% 14C-glucose + 3.44% MCT solution. The dietary treatments did not alter the subjects' weight, body fat, or lipid profile. There were also no changes in circulating glucose, lactate, free fatty acid (FFA), and b-hydroxybutyrate concentrations during exercise. However, mean serum glycerol concentrations were significantly higher (p < .01) in the HFD-CHO trial. The HFD-CHO diet increased total fat oxidation and reduced total CHO oxidation but did not alter plasma glucose oxidation during exercise. By contrast, the estimated rates of muscle glycogen and lactate oxidation were lower after the HFD-CHO diet. The HFD-CHO treatment was also associated with improved TT times (29.5 +/- 2.9 min vs. 30.9 +/- 3.4 min for HFD-CHO and CTL-CHO, p <.05). High-fat feeding for 10 days prior to CHO-loading was associated with an increased reliance on fat, a decreased reliance on muscle glycogen, and improved time trial performance after prolonged exercise.     

Aortic antioxidant defense and lipid peroxidation in rabbits fed diets supplemented with different animal and plant fats.

To test the hypothesis that dietary fats, depending on the fat source, may modulate aortic lipid peroxidation and antioxidant protection.

Rabbits were fed a low fat (LF, 2 g/100 g corn oil) diet or LF enriched with 16 g/100 g (w/w) of corn oil (CO), corn oil plus cholesterol (23.5 mg/100 g diet, CO + C), bovine milk fat (MF), chicken fat (CF), beef tallow (BT) or lard (L). After a 30-day feeding period, aortic lipid peroxidation, as well as antioxidant enzymes and vitamin E were measured.

In rabbits fed CO or L, aortic TBARS (a marker of lipid peroxidation) and total glutathione concentrations were greater but vitamin E levels were lower compared with the LF treatment. Moreover, in rabbits fed CO, elevated activities of glutathione peroxidase and glutathione reductase but lowered activity of superoxide dismutase were observed. In rabbits fed the remaining high fat diets, including the CO + C diet, aortic lipid peroxidation and antioxidant activities/levels did not differ from those fed LF. Feeding rabbits high-fat diets for 30 days did not induce aortic lipid deposition.

The present results indicate CO, and possibly L, as the fat sources which significantly increase aortic oxidative stress. Because long-term disturbances in redox status may be implicated in atherogenesis, excessive dietary intake of CO or L may significantly contribute to the injury of the vessel wall.     

Dietary fat,calories, and the risk of breast cancer in postmenopausal women: a prospective population-based study.

We tested the hypothesis that a high-fat diet increases the risk of breast cancer in a population-based study of 590 women aged 40-79 years who were without known breast cancer when they provided a quantitative 24-hour diet recall. Fifteen postmenopausal women were diagnosed with incident breast cancer during the next 15 years (approximately 7600 person-years of follow-up). These women had significantly higher age-adjusted intake of all fats (monounsaturated, polyunsaturated, and saturated), and oleic, linoleic, and linolenic acids, with a stepwise increase in risk across tertiles of intake. Fat intake was associated with total calories, protein, and carbohydrates, and women with incident breast cancer consumed more calories, protein, and carbohydrates than did other subjects. When each nutrient variable (calories, fats, protein, and carbohydrates) was adjusted for age, body mass index, age at menopause, parity, and alcohol consumption, the strongest risks for incident breast cancer were associated with total calories (relative risk per standard deviation = 2.72, 95% confidence interval = 1.51-4.89, p = 0.002) and total fats (relative risk per standard deviation = 2.01, 95% confidence interval = 1.19-3.41, p = 0.01). Fat composition of the diet, expressed either as percent of energy or as fat intake adjusted for calories by regression analysis, was not significantly associated with risk of breast cancer. These results support the hypothesis that total calorie consumption, as well as dietary fat consumption, is a risk factor for breast cancer in postmenopausal women, and parallel observations in animal models.     

Comparison of monounsaturated fat with carbohydrates as a replacement for saturated fat in subjects with a high metabolic risk profile: studies in the fasting and postprandial states

BACKGROUND: In subjects with a high prevalence of metabolic risk abnormalities, the preferred replacement for saturated fat is unresolved. OBJECTIVE: The objective was to study whether carbohydrate or monounsaturated fat is a preferred replacement for saturated fat. DESIGN: Fifty-two men and 33 women, selected to have any combination of HDL cholesterol < or = 30th percentile, triacylglycerol > or = 70th percentile, or insulin > or = 70th percentile, were enrolled in a 3-period, 7-wk randomized crossover study. The subjects consumed an average American diet (AAD; 36% of energy from fat) and 2 additional diets in which 7% of energy from saturated fat was replaced with either carbohydrate (CHO diet) or monounsaturated fatty acids (MUFA diet). RESULTS: Relative to the AAD, LDL cholesterol was lower with both the CHO (-7.0%) and MUFA (-6.3%) diets, whereas the difference in HDL cholesterol was smaller during the MUFA diet (-4.3%) than during the CHO diet (-7.2%). Plasma triacylglycerols tended to be lower with the MUFA diet, but were significantly higher with the CHO diet. Although dietary lipid responses varied on the basis of baseline lipid profiles, the response to diet did not differ between subjects with or without the metabolic syndrome or with or without insulin resistance. Postprandial triacylglycerol concentrations did not differ significantly between the diets. Lipoprotein(a) concentrations increased with both the CHO (20%) and MUFA (11%) diets relative to the AAD. CONCLUSIONS: In the study population, who were at increased risk of coronary artery disease, MUFA provided a greater reduction in risk as a replacement for saturated fat than did carbohydrate.     

Dietary composition influences short-term endurance training-induced adaptations of substrate partitioning during exercise

The purpose of the current study was to examine the influence of dietary composition on short-term endurance training-induced adaptations of substrate partitioning and time trial exercise performance. Eight untrained males cycled for 90 min at approximately 54% aerobic capacity while being infused with [6,6(2)H]glucose before and after two 10-d experimental phases separated by a 2-week washout period. Time trial performance was measured after the 90-min exercise trials before and after the 2nd experimental phase. During the first 10-d phase, subjects were randomly assigned to consume either a high carbohydrate or high fat diet while remaining inactive (CHO or FAT). During the second 10-d phase, subjects consumed the opposite diet, and both groups performed identical daily supervised endurance training (CHO+T or FAT+T). CHO and CHO+T did not affect exercise metabolism. FAT reduced glucose flux at the end of exercise, while FAT+T substantially increased whole body lipid oxidation during exercise and reduced glucose flux at the end of exercise. Despite these differences in adaptation of substrate use, training resulted in similar improvements in time trial performance for both groups. We conclude that (a) 10-d high fat diets result in substantial increases in whole body lipid oxidation during exercise when combined with daily aerobic training, and (b) diet does not affect short-term training-induced improvements in high-intensity time trial performance.     

Effect of dietary fat intake and exercise on inflammatory mediators of the immune system in sedentary men and women

OBJECTIVE: Dietary fat intake and exercise affect the immune system. This study determined the changes in inflammatory components of the immune system in response to maximal exercise with three levels of dietary fat intake: 19%, 30%, and 50% of total calories. METHODS: Five men and six women were randomly assigned to consume diets with 19% and 50% calories from fat for three weeks each, with a one-week washout. The habitual and washout diets were 30% calories from fat. At the beginning and the end of each diet, body composition and maximal exercise tests were performed. Blood samples were collected before and after exercise to determine the immunological parameters. RESULTS: The subject's energy intake was balanced to expenditure on the 30% and 50% diets, but was in negative balance on the 19% diet. Exercise led to significant increases in the concentrations of leukocytes, neutrophils, lymphocytes, monocytes, plasma tumour necrosis factor (TNF)-alpha, plasma interleukin (IL)-2, plasma soluble vascular cell adhesion molecule (sVCAM)-1, and the production of IL-1beta and IL-6 by peripheral blood mononuclear (PBMN) cells stimulated with lipopolysaccharide (LPS), irrespective of diets (p < 0.05). The 19% fat diet resulted in increased plasma soluble intercellular adhesion molecule (sICAM)-1 after exercise. Leukotriene (LT) B4 concentration released by neutrophils stimulated with LPS was higher in the 50% fat diet, compared to the lower fat diets, and the sICAM-1 production of neutrophils stimulated with LPS was significantly increased after exercise only with 30% fat diet. CONCLUSION: While a short, intense bout of exercise increased pro-inflammatory mediators of the immune system, decreasing fat intake to 19% on a caloric deficient diet caused a greater increase in plasma TNF-alpha, sVCAM-1 and sICAM-1 concentration than the 30% and 50% fat diets in male and female subjects. Increasing fat calories to 50% with caloric balance did not exacerbate pro-inflammatory mediators compared to a 30% fat diet.     

Antioxidant enzyme response to selenium deficiency in rat myocardium.

Influences of dietary selenium (Se) deficiency, physical training and an acute bout of exercise on myocardial antioxidant enzyme activity, lipid peroxidation and related biochemical properties were investigated in post-weanling male Sprague-Dawley rats. An experimental group was fed a diet containing less than 0.01 mg Se/kg and had free access to distilled water (Se-D), whereas control rats were supplemented with 0.5 mg Se/l in drinking water (Se-A). Se deficiency depleted heart mitochondrial and cytosolic Se-dependent glutathione peroxidase activity to 24 and 3%, respectively, of those in Se-A rats. Heart mitochondrial superoxide dismutase (Mn SOD) activity was 24% higher (p less than 0.05) in Se-D than in Se-A rats. Cytosolic (copper-zinc) SOD and catalase activities were not altered, whereas glutathione S-transferase activity was significantly decreased in Se-D (p less than 0.01). Myocardial antioxidant enzyme activities were not affected by either training or an acute exercise bout. Heart lipid peroxidation and activities of several enzymes in substrate metabolism were also unaffected by Se or exercise. It is concluded that rat heart has sufficient reserve of antioxidant enzyme capacity in coping with oxidative stress imposed by Se deficiency or exercise. The adaptation of Mn SOD may reveal its potential role in myocardial antioxidant defense.     

Changes in lipid metabolism and antioxidant defense status in spontaneously hypertensive rats and Wistar rats fed a diet enriched with fructose and saturated fatty acids

OBJECTIVE: Larger doses of fructose and saturated fat have been associated with oxidative stress and development of hypertension. The effects of modest amounts of fructose and saturated fatty acids on oxidative stress are unknown. METHODS: To increase knowledge on this question, 10-wk-old spontaneously hypertensive rats and Wistar rats were fed for 8 wk with a control diet or an experimental diet enriched with fructose (18%) and saturated fatty acids (11%; FS diet). The total antioxidant status of organs and red blood cells was assayed by monitoring the rate of free radical-induced red blood cell hemolysis. Sensitivity of very low-density lipoprotein and low-density lipoprotein (VLDL-LDL) to copper-induced lipid peroxidation was determined as the production of thiobarbituric acid-reactive substances. Antioxidant enzymes and vitamins were also measured to establish the oxidative stress effect. RESULTS: The FS diet did not affect blood pressure in either strain, but it increased plasma insulin concentrations only in Wistar rats without affecting those of glucose of either strain. The FS diet significantly enhanced plasma and VLDL-LDL triacylglycerol concentrations without affecting concentrations of VLDL-LDL thiobarbituric acid-reactive substances. The decreased content of arachidonic acid and total polyunsaturated fatty acids in VLDL-LDL by the FS diet may have prevented lipid peroxidation in this fraction. Moreover, FS consumption by both strains was accompanied by a significant increase in total antioxidant capacity of adipose tissue, muscle, heart, and liver. This may have resulted from increased tissue ascorbic acid levels and glutathione peroxidase and glutathione reductase activities in tissues. CONCLUSIONS: These findings clearly indicate that the FS diet did not alter blood pressure of spontaneously hypertensive rats and Wistar rats. The FS diet resulted in hypertriglyceridemia but increased the total antioxidant status, which may prevent lipid peroxidation in these rats.     

Update of the Healthy Eating Index: HEI-2010

The Healthy Eating Index (HEI) is a measure of diet quality in terms of conformance with federal dietary guidance. Publication of the 2010 Dietary Guidelines for Americans prompted an interagency working group to update the HEI. The HEI-2010 retains several features of the 2005 version: (a) it has 12 components, many unchanged, including nine adequacy and three moderation components; (b) it uses a density approach to set standards, eg, per 1,000 calories or as a percentage of calories; and (c) it employs least-restrictive standards; ie, those that are easiest to achieve among recommendations that vary by energy level, sex, and/or age. Changes to the index include: (a) the Greens and Beans component replaces Dark Green and Orange Vegetables and Legumes; (b) Seafood and Plant Proteins has been added to capture specific choices from the protein group; (c) Fatty Acids, a ratio of polyunsaturated and monounsaturated to saturated fatty acids, replaces Oils and Saturated Fat to acknowledge the recommendation to replace saturated fat with monounsaturated and polyunsaturated fatty acids; and (d) a moderation component, Refined Grains, replaces the adequacy component, Total Grains, to assess overconsumption. The HEI-2010 captures the key recommendations of the 2010 Dietary Guidelines and, like earlier versions, will be used to assess the diet quality of the US population and subpopulations, evaluate interventions, research dietary patterns, and evaluate various aspects of the food environment.     

Effect of a rapeseed oil substituting diet on serum lipids and lipoproteins in children and adolescents with familial hypercholesterolemia

OBJECTIVE: Familial hypercholesterolemia (FH) is a predominantly inherited disorder, which contributes to a defect of the LDL-cholesterol receptor. For adults with familial hypercholesterolemia (FH), it is known that a supplementary diet of monounsaturated fatty acids reduces elevated levels of total cholesterol and LDL-cholesterol and may further increase HDL-cholesterol. In particular the reduced intake of dietary fat reduces total serum cholesterol and LDL-cholesterol in the range of 10% to 15% and inhibits LDL-oxidation. Once the diagnosis of familial hypercholesterolemia is made in early childhood a supplementary diet with rapeseed oil should be started as early as possible to prevent development of atherosclerosis and subsequent complications. So far there are no reports of a lipid lowering diet enriched with rapeseed oil in children and adolescents. METHODS: Seventeen children and young adolescents (male = 6, female = 11, ages 4 to 19 years) diagnosed with FH were enrolled in this study. They received dietary training and a classical low fat/low cholesterol diet enriched with rapeseed oil over five months. In the first two months they received orally mean 15 g/day (8-23 g/day), for the remaining three months mean 22 g/day (15-30 g/day) rapeseed oil. The calculation of the three-days dietary protocols showed the following characteristics: 29.5% calories from fat, 14.3% calories from protein and 54.6% calories from carbohydrates. The subjects had six sessions of dietary counseling, and serum lipids levels and lipoprotein(a) were estimated; each month's diet adherence was controlled by a dietitian and discussed with the patients and their families during this five-month study. RESULTS: During five months of rapeseed oil diet serum triglycerides decreased by 29% (119.2+/-62.8 mg/dL vs. 84.9 mean +/- 39.7 mg/dL), VLDL-cholesterol by 27% (23+/-12 mg/dL vs. 17+/-8 mg/dL), total cholesterol by 10% (233+/-35 mg/dL vs. 213+/-36 mg/dL), LDL-cholesterol by 7% (151+/-31 mg/dL vs. 142+/-31 mg/dL). HDL-cholesterol (59+/-15 mg/dL vs. 57+/-11 mg/dL) and Lp(a) (29.8+/-36.3 mg/dL vs. 32.6+/-40.7 mg/dL) were not changed significantly. The diet was well accepted; in most families a sustained change was reported. CONCLUSIONS: Our results indicate that in children and adolescents with FH a lipid-lowering diet with rapeseed oil has a similar effect on total serum cholesterol and LDL-cholesterol compared to classical cholesterol reduction diets (step I). However, an additional pronounced effect on lowering of triglycerides and VLDL-cholesterol can be observed.     

Role of vitamin E and oxidative stress in exercise.

Reactive oxygen species (ROS) play an important role as mediators of skeletal muscle damage and inflammation after strenuous exercise. These ROS arise largely from increases in mitochondrial oxygen consumption and electron transport flux. Bouts of intense exercise are associated with increases in lipid peroxidation, generating malondialdehyde and F(2alpha)-isoprostanes, and the release of muscle enzymes like lactate dehydrogenase and creatine kinase. Dietary and enzymatic antioxidant defenses appear to play a protective role in muscle cells by reducing associated oxidative damage to lipids, nucleic acids, and protein. However, studies of the use of dietary antioxidants like vitamin E to reduce exercise-induced muscle injury have met with mixed success. The equivocal nature of these results appear to reflect a diversity of factors including the antioxidant(s) tested, the nature and timing of the exercise, the age and fitness of the subjects, and the methodology for assessing oxidative stress.     

Grape skin improves antioxidant capacity in rats fed a high fat diet

This study was conducted to investigate the effect of dietary grape skin on lipid peroxidation and antioxidant defense system in rats fed high fat diet. The Sprague-Dawley rats were fed either control (5% fat) diet or high fat (25% fat) diet which was based on AIN-93 diet for 2 weeks, and then they were grouped as control group (C), control + 5% grape skin group (CS), high-fat group (HF), high fat + 5% grape skin group (HFS) with 10 rats each and fed corresponding diets for 4 weeks. The hepatic thiobarbituric acid reacting substances (TBARS) were increased in high fat group as compared with control group, but reduced by grape skin. The serum total antioxidant status, and activities of hepatic catalase and superoxide dismutase, xanthine oxidase and glucose-6-phosphatase were increased by supplementation of grape skin. Glutathione peroxidase activity was significantly higher in CS group than in C group. Grape skin feeding tended to increase the concentration of total glutathione, especially in control group. The ratio of reduced glutathione to oxidized glutathione was lower in high fat groups than in control groups. The ratio was increased by dietary supplementation of grape skin in control group. These results suggest that dietary supplementation of grape skin would be effective on protection of oxidative damage by lipid peroxidation through improvement of antioxidant defense system in rats fed high fat diet as well as rats with low fat diet.     

Effects of saturated, monounsaturated, and omega-6 polyunsaturated fatty acids on plasma lipids, lipoproteins, and apoproteins in humans

The effects of dietary fats on plasma cholesterol, serum lipoproteins, and apoproteins (Apo), A-1, B, and CIII were studied. Twelve men consumed three different cholesterol-free formula diets in which polyunsaturated and saturated fats were partially substituted (20% of calories) for monoenoic fats with a constant of 40% of calories from fat. Total cholesterol and low-density lipoprotein cholesterol dropped from base-line values of 166 and 103 to 133 and 81 mg/dl (sat), 127 and 71 mg/dl (mono), and 123 and 65 mg/dl (poly), respectively. High-density lipoprotein cholesterol changed very little from base-line values of 46 to 40 mg/dl (sat), 45 mg/dl (poly), and 43 mg/dl (mono). The plasma concentrations of ApoB declined from base-line values of 80.3 mg/dl to 54.6 mg (mono), 51.8 mg (poly), and 59.6 mg (sat) while Apo CIII and Apo AI did not show any changes. This study demonstrates that: 1) changes in dietary fat affect serum lipids, lipoproteins, and apoproteins even when consumed on a cholesterol-free diet, and 2) omega-6 polyunsaturated fat lowers low-density lipoprotein cholesterol, total cholesterol, and ApoB to a greater extent than monounsaturated or saturated fat, 3) consumption of a cholesterol-free formula diet results in significant decreases in the concentrations of total and low-density lipoprotein cholesterol in plasma when compared to values obtained on a mixed food home diet containing approximately 300 mg cholesterol/day.     

A rice diet is associated with less fat synthesis/accumulation than a bread diet before exercise therapy

For effective exercise therapy after waking up, we focused on the staple food in diet therapy, and compared rice and bread diets. The subjects were 10 healthy college male students. After fasting for 12 h or more from the previous day, the subjects had breakfast consisting of rice (protein, 6.3 g; fat, 0.9 g: CHO, 79.3 g; energy, 368 kcal) or bread (protein, 15.7 g; fat, 5.8 g; CHO, 79.2 g; and energy, 450 kcal) containing the same amount of carbohydrates and the same side dishes (protein, 7.0 g; fat, 9.5 g; CHO, 21.3 g; energy, 199 kcal) in the morning 30 min before the initiation of exercise on a bicycle ergometer at an intensity of about 50% VO2max for 60 min. Measurements of the heart rate and expired gas were initiated 15 min before the start of exercise and continued until 10 min after exercise. Blood was collected before the meal, immediately before and 15, 30, and 45 min after the initiation of exercise, and immediately, 15, and 30 min after its termination. After breakfast containing carbohydrates, decreases were observed in the levels of free fatty acid and noradrenalin. Blood insulin (mealxtime, p<0.05 ANOVA) and triglyceride (meal x time, p<0.01, ANOVA) changed at higher levels in the bread diet than in the rice diet. Blood triglyceride is a resource of fat synthesis/accumulation, and insulin promotes its action. Therefore, the bread diet may promote fat synthesis/accumulation compared with the rice diet.     

Diets high and low in glycemic index versus high monounsaturated fat diets: effects on glucose and lipid metabolism in NIDDM.

OBJECTIVE: To examine the relative effects of high and low glycemic index (GI) carbohydrates, and monounsaturated fats on blood glucose and lipid metabolism in NIDDM subjects. SUBJECTS: Fourteen male and seven female variably controlled NIDDM subjects recruited by advertisement. SETTING: Free living outpatients. RESEARCH DESIGN: A repeated measures, within-subject design was used such that each subject consumed three diets: (a) a high-GI diet (53% CHO -21% fat, 63 GI units (glucose= 100)); (b) a low-GI diet (51% CHO -23% fat, 43 GI units); and (c) a high-mono high-GI diet (42% CHO -35% fat, 59 GI units) in random order and cross-over fashion for four weeks. Approximately 45% energy was provided as key foods which differed in published GI values and specifically excluded legumes. Dietary fibre intake was > 30 g/d on each diet. At the end of each dietary intervention, we measured fasting plasma lipids, glucose, insulin, total glycated plasma protein, fructosamine, LDL and HDL particle size as well as 24 h urinary excretion of glucose and C-peptide. RESULTS: HDL-cholesterol was higher on the low-GI and high-mono high-GI diets compared to the high-GI diet (P < 0.05 for overall diet effect). There were no other significant differences in metabolic control between diets, even when adjusted for BMI, glucose control or gender. Body weight and saturated fat intake remained stable between dietary interventions. CONCLUSION: High-mono high-GI and high-CHO, low-GI diets are superior to high-CHO, high-GI diets with respect to HDL metabolism but no effect was noted on glucose metabolism in variably controlled NIDDM subjects.     

The effect of dietary fat on LDL size is influenced by apolipoprotein E genotype in healthy subjects

LDL particle size is dependent on both genetic factors and environmental factors such as dietary fat composition. The apolipoprotein E (apoE) genotype is a major genetic determinant of LDL size. Thus, the aim of this work was to study whether the apoE genotype interacts with the quantity and quality of dietary fat, modifying LDL size in young healthy subjects. Healthy subjects (n = 84; 66 apoE 3/3, 8 apoE 4/3, 10 apoE 3/2) were subjected to 3 dietary periods, each lasting 4 wk. The first was an SFA-enriched diet (38% fat, 20% SFA), which was followed by a carbohydrate (CHO)-rich diet (30% fat, < 10% SFA, 55% carbohydrate) or a monounsaturated fatty acid (MUFA) olive oil-rich diet (38% fat, 22% MUFA) following a randomized crossover design. At the end of each diet period, LDL particle size and plasma levels of total cholesterol, LDL cholesterol (LDL-C), HDL-C, apoB, apoA-I, and triacylglycerols were determined. LDL particle size was significantly higher (P < 0.04) in subjects with the apoE 4/3 genotype compared with those with apoE 3/3 and apoE 3/2 in the basal state. LDL size was smaller (P < 0.02) after the CHO diet than after the MUFA or SFA diets. After the CHO diet, a significant increase in LDL particle size (P < 0.035) was noted with respect to the MUFA diet in apoE 4/3 subjects, whereas a significant decrease was observed in the apoE 3/3 individuals (P < 0.043). In conclusion, a Mediterranean diet, high in MUFA-fat increases LDL particle size compared with a CHO diet, and this effect is dependent of apoE genotypes.