Divergent responses of serum lipoproteins to changes in dietary carbohydrate and cholesterol in cynomolgus monkeys

The metabolic effects of dietary carbohydrates (simple versus complex) on lipogenesis, glucose, and insulin responses are well known, but information is lacking on the effect of carbohydrate types on different serum lipoprotein fractions. We therefore studied the differences in responses of serum lipids, lipoproteins, apoproteins, and plasma glucose and insulin to changes in dietary carbohydrates and cholesterol in 12 male cynomolgus monkeys (Macaca fascicularis). For 6 weeks, each monkey was fed one of four semipurified, high-carbohydrate (76.5% cal) diets that provided sucrose or starch with and without 1 mg/kcal cholesterol. Sucrose diet without added cholesterol resulted in consistently higher serum total cholesterol than with a similar starch diet. In contrast, cholesterol-enriched starch diet caused marked increase in serum total cholesterol when compared to similar sucrose diet. Neither starch nor sucrose diets elicited a VLDL-triglyceride response. Observations on apoB, VLDL- and LDL-cholesterol levels essentially reflected serum total cholesterol changes by diet. Changes in HDL-subfractions to dietary carbohydrates were seen mainly in HDL₂, with starch producing lower values than sucrose (p < 0.01). Among the four diets, cholesterol, triglyceride and phospholipid contents of HDL₂, as well as apoA-I and apoA-II contents of serum total lipoproteins were lowest with cholesterol-enriched starch diet feeding. High cholesterol diets increased the cholesterol to triglyceride ratios of LDL, irrespective of type of carbohydrate (p < 0.01), whereas the ratios of cholesterol to phospholipids showed significant carbohydrate effect (starch > sucrose) and cholesterol effect for HDL₂. Neither plasma glucose nor insulin showed any diet-related differences. Thus, a high level of dietary carbohydrate with and without added cholesterol provoked divergent responses of serum lipids and lipoproteins between sucrose and starch. Although reasons for the paradoxical responses are not readily apparent, the experiment provides a useful model for further metabolic studies.     

The effect of sucrose content in high and low carbohydrate diets on plasma glucose, insulin, and lipid responses in hypertriglyceridemic humans

To further understand the effect of high carbohydrate (CHO)-low fat diets and the role of variations in dietary sucrose on CHO and lipid metabolism, 10 patients with hypertriglyceridemia were fed 2 isocaloric, typical American diets, containing 40% and 60% CHO, for 15 days in random sequence. Each patient was their own control, and they were divided into 2 groups of 5 patients each. In one group, sucrose was held constant at 13% of total calories (40-13% and 60-13%), whereas the sucrose content was 9% of the total calories on a 40% CHO diet (40-9%), and 15% of total calories on a 60% CHO diet (60-15%) in the other group. Fasting and postprandial blood samples were analyzed for plasma glucose, insulin, cholesterol (Chol), and triglycerides (TG), as well as for Chol and TG in chylomicrons, very low density, low density, and high density lipoproteins (HDL). Fasting plasma TG levels were significantly increased in both groups on the 60% CHO diet, primarily due to increases in very low density-TG concentration. The magnitude of the elevation was attenuated when sucrose content was kept constant. Postprandial TG responses were qualitatively similar. There were no significant changes in plasma Chol concentrations, except for a modest fall in plasma HDL-Chol level after the 60-13% diet period (P less than 0.05). No significant differences were found in fasting plasma glucose or insulin concentration. However, postprandial glucose and insulin responses were increased on both high CHO diets. The results of these studies demonstrate that high CHO-low fat diets, in general, tend to elevate plasma glucose, insulin, and TG concentrations and reduce HDL-Chol concentration in patients with endogenous hypertriglyceridemia. In addition, these data illustrate the important role that small variations in dietary sucrose can play in modulation of CHO and lipid metabolism.     

The effect of insulin on hyperlipoproteinemia induced by a semi-synthetic diet rich in saturated fats in a rabbit

The influence of insulin therapy on changes in the lipoprotein profile induced by a semi-synthetic saturated-fat diet was studied in the rabbit. Hypercholesterolemia, observed after two months diet, corresponded to an increase in all lipoprotein fractions as well as an enrichment in cholesterol esters of VLDL and LDL. Treatment with insulin had only a slight effect on the increase in the lipoproteins, but completely prevented the appearance of abnormal LDL. Changes in the lipoprotein profile were markedly aggravated, without an additional increase in plasma cholesterol, when the semi-synthetic diet was continued for six months. All lipoprotein fractions showed increases in cholesterol esters and in free cholesterol at the expense of triglycerides and proteins. The animals receiving the semi-synthetic diet and treated with insulin showed decreased glucose tolerance but no additional modifications in the lipoprotein profile or in the composition of aortic tissue. Therefore, insulin initially prevents alterations in LDL, induced by the semi-synthetic diet, prevention which is not maintained in the long term.     

Effects of casein and soy protein on hepatic and serum lipids and lipoprotein lipid distributions in the rat

Rats fed a semipurified diet containing casein developed higher levels of circulating triglycerides and cholesterol than animals fed a soy protein-containing diet. The increased serum lipid levels in non-fasted rats were associated largely with the d less than 1.006 g/ml lipoprotein particles (e.g. chylomicrons or very low density-like lipoproteins). In addition, casein-fed rats exhibited higher levels of circulating insulin and depressed hepatic 7 alpha-hydroxylase levels compared to soy-fed rats. Supplementation of the casein diet with arginine, to give an arginine/lysine ratio comparable to that in the soy diet, resulted in a reduction of d less than 1.006 g/ml lipids, a reduction in serum insulin levels and an elevation in hepatic 7 alpha-hydroxylase activity. Supplementation of the soy diet with lysine also resulted in modification of these parameters toward those observed with casein diets, albeit the effects were less dramatic. The results suggest that the hyperlipidemia associated with feeding casein-based diet is associated with decreased rates of clearance of chylomicron-like lipoproteins and their component triglycerides and cholesterol. Furthermore, this is largely prevented by addition of arginine to diets containing casein as the sole protein source.     

Effect of lactose content of nonfat milk diets on male rat serum lipids and lipoproteins

The lactose content of a semisynthetic diet containing 45% of calories as nonfat milk powder was modified by enzymatic hydrolysis with beta-galactosidase or bacterial fermentation with yogurt cultures. Three milk-based diets and a stock diet were fed for 28 days to male rats derived from the Sprague-Dawley strain. Energy consumption, growth rate, feed efficiency, liver weight, liver cholesterol and liver triglyceride concentrations were not significantly different between the four diets. At day 28 serum cholesterol and serum triglyceride concentrations were not different between the milk-based diets. No hypocholesterolemic effect of the milk-based diets was seen at any time compared to the stock diet. Two of four electrophoretic lipoprotein fractions varied with the lactose content of the milk-based diet. The faster alpha lipoprotein decreased while the slower alpha lipoprotein increased with decreasing content of dietary lactose. These data indicate that lactose differs from its constituent monosaccharides, galactose and glucose, in its effect on lipoprotein levels, even though total serum cholesterol and triglycerides do not differ.     

Metabolic changes in healthy men using fat-modified diets. I. Disposition of serum cholesterol

The effect of typical fat-modified diets on serum lipids, lipoproteins and apolipoproteins, on the intravenous fat-tolerance test and on fecal sterol excretion were observed in a group of men living at home and compared to that of their normal diets. Two 4-week-long diet periods alternated with four periods of 6 weeks' duration during which the men followed their normal dietary habits and accustomed life-styles. According to a randomized cross-over design sunflower oil and corn oil were used as the main fat sources for the fat-modified diets. Both diets lowered total cholesterol considerably acting mainly on LDL cholesterol, without affecting plasma triglycerides significantly. Apolipoprotein A-I and A-II concentrations in serum remained constant, and clearance of triglyceride-rich lipoproteins, as measured by an intravenous fat-tolerance test (Intralipid test), was not significantly affected. While changes of all measured parameters pointed in the same direction, serum total and LDL cholesterol levels were significantly lower with corn oil than with the sunflower oil. Excretion of endogenous sterols (fecal sterol balance) was higher with the fat-modified than with the normal diet. This increase in sterol excretion closely corresponded to the extent of serum cholesterol lowering.     

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.     

Effect of stanol ester on postabsorptive squalene and retinyl palmitate

Stanol ester dissolved in margarine inhibits cholesterol absorption in general and, despite increasing cholesterol synthesis, decreases serum total and low-density lipoprotein (LDL) cholesterol levels, but its effects on postprandial lipid metabolism are unknown. We performed fat tolerance tests in 11 men at baseline and during short-term stanol ester consumption without and with stanol esters added to the test meal also containing retinol and squalene. Cholesterol, triglycerides, retinyl palmitate, and squalene were analyzed in plasma, chylomicrons, and very-low-density lipoprotein (VLDL) at baseline and 3, 4, 6, 9, 12, and 24 hours after the test meal. Serum total and LDL cholesterol only tended to diminish after the 2-week stanol ester consumption. However, the proportion of plasma plant sterol and cholesterol-precursor sterol to cholesterol was significantly altered, suggesting that cholesterol absorption was diminished and cholesterol synthesis was increased. Postprandial peak times of squalene and retinyl palmitate in plasma, chylomicrons, and VLDL were significantly reduced by stanol esters, but their concentrations in chylomicrons were unchanged. Stanol esters reduced the VLDL squalene peak concentration by 23% (P < .05) and the incremental area under the curve (AUIC) in plasma and VLDL by 22% and 32% (P < .01 for both). Chylomicron remnant metabolism measured with triglycerides only tended to diminish. The effects of stanol esters in the diet only and both in the diet and with supplementation did not differ significantly. We conclude that dietary stanol esters reduce postprandial lipoproteins measured with dietary retinyl palmitate and especially squalene, and the reduction is observed even though serum total and LDL cholesterol are only inconsistently decreased after short-term stanol ester consumption.     

Diets realistic for westernized people significantly effect lipoproteins, calcium, zinc, vitamins C, E, B6 and haematology in vervet monkeys

This report describes measurements of 50 variables in adult, female, reproductively inactive Vervet monkeys during prolonged nutrition realistic for westernized people. Dietary treatments consisted of an atherogenic Western diet (WD) and a prudent Western diet (PD). Ingredients were normal foods for man and no extra cholesterol was added. Fortification of both diets with vitamin C after cooking was necessary to prevent deficiency. Randomised groups of Vervet monkeys received either the PD or WD for 47 months, while a third group was fed WD for 20 months and then PD for 27 months (WD-PD). Before the dietary treatments nourishment was by a high carbohydrate diet (HCD) and baseline and reference values (RV) apply to this nutritional status. Plasma total cholesterol (mg/dl) was increased from 147 (HCD) to 174 (PD) and 376 (WD). Individual cholesterolaemio response ranged from mild to severe and was stable (PD and WD). Dietary reversal (WD-PD) reduced cholesterolaemia promptly. Statistically significant increases in calcium, zinc and vitamin E and decreased vitamin B6 were associated with the WD relative to the PD (in serum and plasma). Two cholesterol metabolising microsomal enzymes in liver were notably increased and one unchanged (WD). There were no dietary effects on triglycerides, vitamin A and glucose in plasma; insulin, glucagon, electrolytes, copper, magnesium or enzymes reflecting liver, muscle or brain cell damage in serum. Red blood cells, platelets and directly associated parameters increased (WD), haemoglobin was the same and haemoglobin per red cell decreased. Bleeding time was not affected. Bivariate correlations across the diets confirmed that Western nutrition promoted inherent individual susceptibility to cholesterolaemia. There were notable differences from RVs in total cholesterol, calcium, packed cell volume and haemoglobin, which emphasise excesses and deficiencies of the WD and PD.     

Serum lecithin:cholesterol acyltransferase activities of cynomolgus monkeys fed different carbohydrate diets

Although serum lecithin:cholesterol acyltransferase (LCAT) activity is known to be modulated by nutritional factors, little is known about the effects of dietary carbohydrate on this enzyme. Therefore, LCAT activities were assessed in cynomolgus monkeys fed diets for 6 weeks on 4 diets containing 77% of calories as sucrose or starch and cholesterol at 0 and 1 mg/kcal. Three different assay conditions were used in order to measure the overall LCAT activity and to differentiate enzyme activity from the effect of serum substrate and end-product lipoprotein alterations by diet on this enzyme. Molar rate of serum total LCAT activity was higher in sucrose than starch diets (P less than 0.01). Use of sera from sucrose-fed animals, either as substrate or enzyme source, increased the fractional rate of cholesterol esterification (P less than 0.01). Exogenous cholesterol lowered serum total LCAT activity only in sucrose diet (P less than 0.01). Use of sera from sucrose + cholesterol-fed animals as substrate significantly lowered the fractional rate of cholesterol esterification (P less than 0.01); whereas no such alterations were noted when this serum was used as enzyme source. The differential effect of starch and sucrose diets on LCAT activity suggests that the nature of dietary carbohydrates may affect LCAT activity in association with triglyceride metabolism by altering the amount of enzyme in terms of its activity and/or the nature of substrate and cholesterol ester acceptor lipoproteins.     

JTT-130, a novel intestine-specific inhibitor of microsomal triglyceride transfer protein, ameliorates impaired glucose and lipid metabolism in Zucker diabetic fatty rats

Aim: Microsomal triglyceride transfer protein (MTP) takes part in the mobilization of triglyceride‐rich lipoproteins from enterocytes and hepatocytes. We investigated the effects of JTT‐130, a novel intestine‐specific MTP inhibitor, on impaired glucose and lipid metabolism in Zucker diabetic fatty (ZDF) rats. Methods: Male ZDF rats were fed a regular powdered diet with or without JTT‐130 as a food admixture (0.01–0.02%) for 6 weeks. Food intake, body weight, blood biochemical parameters, fecal lipid contents, hepatic lipid contents, tissue mRNA levels and glucose utilization in adipose tissues were assessed. An intraperitoneal glucose tolerance test (IPGTT) and histological analysis of the pancreas were performed. Results: JTT‐130 treatment decreased food intake, glycated hemoglobin, plasma levels of glucose, triglycerides and total cholesterol, hepatic levels of triglycerides and cholesterol and hepatic mRNA levels of glucose‐6‐phosphatase, phosphoenolpyruvate carboxykinase and fructose‐1,6‐bisphosphatase. JTT‐130 treatment increased fecal levels of free fatty acids and cholesterol, plasma levels of glucagon‐like peptide‐1 and peptide YY, mRNA levels of glucose transporter 4 (GLUT4) and lipoprotein lipase in adipose tissues and GLUT4 in muscle and glucose utilization in adipose tissues. Plasma insulin decreased after 2 weeks and increased after 4 weeks of JTT‐130 treatment. Plasma glucose in the JTT‐130‐treated rats was lower with higher plasma insulin than in the control rats during the IPGTT. The islets of the JTT‐130‐treated rats were larger and contained more insulin than those of the control rats. Conclusions: JTT‐130 ameliorates impaired glucose and lipid metabolism in the ZDF rats thereby suggesting that JTT‐130 could be useful for prevention and treatment of type 2 diabetes.     

Comparison of the effects on insulin sensitivity of high carbohydrate and high fat diets in normal subjects.

To examine whether achievable dietary changes influence insulin sensitivity, we performed euglycemic hyperinsulinemic glucose clamps in eight normal subjects who were prescribed high carbohydrate and high fat diets. The high carbohydrate diet was more than 50% (of energy intake) carbohydrate and less than 30% fat; the high fat diet was more than 45% fat (predominantly saturated) and less than 40% carbohydrate. The diets were consumed over consecutive 3-week periods in random sequence. The mean whole body glucose uptake during the glucose clamps was similar after the high carbohydrate (48.3 mumol/kg.min) and high fat diets (47.0 mumol/kg.min; P = 0.5; 95% confidence interval for the difference, -3.4 to 5.9 mumol/kg.min). Fasting blood glucose and serum insulin concentrations were also unchanged. In contrast, there were substantial effects on lipoprotein metabolism. During the high carbohydrate diet, fasting serum cholesterol decreased by 17% (P = 0.06), low density lipoprotein cholesterol decreased by 20% (P = 0.05), high density lipoprotein cholesterol decreased by 24% (P less than 0.005), and triglyceride increased by 33% (P = 0.06) compared with levels during the high fat diet. These results suggest that practically achievable high carbohydrate diets do not enhance insulin sensitivity in nondiabetic subjects and have net effects on lipoprotein metabolism that may be unfavorable.     

Treatment of hypertriglyceridemia by two diets rich either in unsaturated fatty acids or in carbohydrates: effects on lipoprotein subclasses, lipolytic enzymes, lipid transfer proteins, insulin and leptin

BACKGROUND: There is lack of agreement on which dietary regimen is most suitable for treatment of hypertriglyceridemia, especially if high triglyceride concentrations are not due to obesity or alcohol abuse. We compared the effects on blood lipids of a diet high in total and unsaturated fat with a low-fat diet in patients with triglyceride concentrations of > 2.3 mmol/l. METHODS: Nineteen non-obese male outpatients with triglycerides ranging from 2.30 to 9.94 mmol/l received two consecutive diets for 3 weeks each: first a modified high-fat diet (39% total fat, 8% SFA, 15% monounsaturated fatty acids, 1.6% marine n-3 polyunsaturated fatty acids), and then a low-fat diet (total fat 28%, carbohydrates 54%). RESULTS: The high-fat diet significantly decreased triglycerides (-63%), total cholesterol (-22%), VLDL cholesterol (-54%), LDL cholesterol ( 16%), total apoC-III (-27%), apoC-III in apoB containing lipoproteins (apoC-III LpB; -31%) and in HDL (apoC-III nonLpB; -29%), apoE in serum (-33%) and apoB-containing lipoproteins (nonHDL-E; -42%), LpA-I (-16%), insulin (-36%), and leptin (-26%) and significantly increased the means of HDL cholesterol (+8%), LDL size (+6%), lipoprotein lipase (LPL, +11%), hepatic lipase (+13%), and lecithin: cholesterol acyltransferase (LCAT, +2%). The subsequent low-fat diet increased triglycerides (+63%), VLDL cholesterol (+19%), apoC-III (+23%), apoC-III LpB (+44%) apoC-III nonLpB (+17%), apoE (+29%) and nonHDL-E (+43%), and decreased HDL cholesterol (-12%), LPL (-3%), and LCAT (-3%). Changes in triglycerides correlated with changes in LPL activity and insulin levels. CONCLUSIONS: In hypertriglyceridemic patients, a modified diet rich in mono- and n-3 polyunsaturated fatty acids is more effective than a carbohydrate-rich low-fat diet in correcting the atherogenic lipoprotein phenotype.     

Short-term effects of moderate alcohol consumption on lipid metabolism and energy balance in normal men

The short-term effects of moderate alcohol consumption on energy balance, serum lipids, and lipoproteins were studied in eight healthy middle-aged men (age 30 to 47 years and body mass index 23.1 to 27.7 w/h2). A crossover dietary trial included two isocaloric periods without (20% protein, 50% carbohydrate, 30% fat) or with alcohol (12% protein, 29% carbohydrate, 25% fat, 75 g of alcohol as red wine). Each period lasted 2 weeks. The body weight of the subjects remained stable over the study. Fasting blood glucose, serum insulin, total cholesterol, and LDL cholesterol were similar at the end of both dietary periods. Mean values of serum total triglyceride (108 +/- 18 v 85 +/- 24 mg/dL, P less than 0.05), VLDL-Tg (88 +/- 24 v 73 +/- 16 mg/dL, NS), and total HDL cholesterol (49.4 +/- 6.0 v 43.4 +/- 5.5 mg/dL, P less than 0.05) were higher after the diet with alcohol than without alcohol. The increase of HDL cholesterol was primarily due to that of HDL2 cholesterol (10.4 +/- 5.1 v 5.7 +/- 3.9 mg/dL, P less than 0.05). The concentration of apoprotein A-I, A-II, and B averaged 104 +/- 17 v 89 +/- 16 mg/dL, 33 +/- 4 v 28 +/- 8 mg/dL, P less than 0.02, and 111 +/- 24 v 105 +/- 33 mg/dL after the diets with and without alcohol, respectively. Adipose tissue LPL activity increased in six of the eight volunteers during the diet with alcohol. Resting metabolic rate, postprandial energy expenditure, and postprandial responses of blood glucose, serum insulin, triglyceride, and plasma FFA were similar after the both diets.(ABSTRACT TRUNCATED AT 250 WORDS)     

Metabolic effects of added dietary sucrose in individuals with noninsulin-dependent diabetes mellitus (NIDDM)

This study addresses the metabolic effects of sucrose in the diets of 11 individuals with noninsulin-dependent diabetes mellitus (NIDDM). Each of two dietary periods were 15 days in length, and contained 50% of the calories as carbohydrate, 30% as fat, and 20% as protein. The only variable between the two periods was the percentage of total calories as sucrose, 16% v 1%. Fasting blood samples were analyzed for plasma glucose and insulin as well as total plasma VLDL-, LDL- and HDL-cholesterol and triglyceride concentrations. In addition, postprandial blood samples were obtained for the measurement of plasma glucose, insulin and triglyceride concentrations. Fasting plasma glucose, insulin, and day-long insulin concentrations were similar between the two diets. However, the addition of sucrose in amounts comparable to those typically consumed by the general population resulted in significantly elevated day-long glucose (P less than 0.05) and triglyceride (P less than 0.05) responses, as well as elevated fasting total plasma cholesterol (P less than 0.001), triglyceride (P less than 0.05), VLDL-cholesterol (P less than 0.01), and VLDL-triglyceride (P less than 0.05) concentrations. LDL-cholesterol and HDL-cholesterol concentrations were unchanged during the added sucrose diet. It is clear that the consumption of diets containing moderate amounts of sucrose resulted in changes to plasma lipid and postprandial glucose concentrations that have been identified as risk factors for coronary artery disease. Therefore, it seems prudent at this time to advise patients with NIDDM to avoid added dietary sucrose.     

Serum lipids, lipoprotein composition and liver cholesterol in genetically obese Zucker rats fed semipurified diets containing either casein or soy protein

The effect of semipurified diets containing either casein or soy protein on serum lipids, lipoprotein composition and liver cholesterol was studied in genetically obese Zucker rats. The ingestion of a cholesterol-enriched semipurified diet containing casein resulted in elevated levels of serum cholesterol and phospholipids compared to the feeding of a soy protein diet. No differences in serum triglycerides were observed. Differences in serum cholesterol and phospholipids were mainly reflected in the very low density lipoproteins and low density lipoproteins and to a minor extent in the high density lipoproteins. Liver cholesterol paralleled the levels of cholesterol in the serum, the rats fed casein exhibited markedly higher levels of liver cholesterol than those fed soy protein. Furthermore, the rats fed casein also had enlarged livers. Thus, this study clearly shows the differential cholesterolemic effect of dietary casein and soy protein in genetically obese Zucker rats.     

Plasma glucose, insulin and lipid responses to high-carbohydrate low-fat diets in normal humans

Two levels of dietary carbohydrate (40% and 60% of calories) were incorporated into typical U.S. diets and fed for 10 days each to 11 healthy volunteers. Fasting blood samples were drawn on days 8, 9, and 10 of each dietary period and analyzed for glucose, insulin, cholesterol, triglyceride (TG) and high density lipoprotein (HDL)-cholesterol concentrations. In addition, plasma glucose, insulin and TG concentrations were determined before, and for 3 hr after the noon meal on days 8 and 10. No differences were observed in fasting plasma glucose, insulin or cholesterol concentrations. However, fasting plasma TG levels were significantly elevated on the 60% carbohydrate diet, and HDL-cholesterol concentrations were significantly decreased. Furthermore, the plasma insulin and triglyceride responses to the meal tolerance test during the 60% carbohydrate dietary period were significantly elevated. These results indicate that high-carbohydrate diets lead to changes in insulin, TG, and HDL-cholesterol concentrations which have been associated with an increase in incidence of coronary artery disease.     

Dietary phytoestrogens and plasma lipids in Dutch postmenopausal women; a cross-sectional study

OBJECTIVE: Isoflavone supplementation in high doses is associated with plasma lipid, glucose and insulin levels. Little is known about the effects of intake within the range of western diets on these endpoints. Design: We conducted a population-based cross-sectional study in 301 women aged 60-75 years. METHODS: Dietary isoflavone and lignan intake was assessed with a food frequency questionnaire covering habitual diet during the year preceding enrollment. The outcome measures were total cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides, Lp(a), fasting glucose and insulin levels. Data were analysed using linear regression and logistic regression models. In the analyses we adjusted for a wide range of potential confounders. RESULTS: High intake of isoflavones was associated with lower Lp(a) levels (tertile three versus tertile one: odds ratio 0.36, 95% CI 0.16; 0.80). No relation was found between blood levels and the other plasma lipids, glucose or insulin was found. CONCLUSION: The results of this study suggest that an effect of dietary phytoestrogen intake at low levels on plasma lipid levels is of limited magnitude. It is premature to advise postmenopausal women with low phytoestrogen intake to change their diet towards a phytoestrogen rich diet with the sole aim to prevent cardiovascular disease.     

Type and amount of dietary fat affect relative concentration of cholesterol in blood and other tissues of rats

The effects of diet on tissue cholesterol disposition in the rat were studied. Growing rats were fed a nonfat dry milk supplemented with two levels of soy-bean oil (SBO) and tallow (T) such that either 30% or 50% of total dietary calories came from fat. Two of four groups of rats fed the diets with 50% of calories from fat were supplemented with 20% ground whole oats. Considering all diets, rats fed SBO had higher blood and kidney cholesterol than did rats fed T; supplementation of the diet with oats increased the plasma cholesterol of the "50%" SBO rats and , conversely, decreased plasma cholesterol of the "50%" T rats. Muscle cholesterol content was not affected by variations in dietary fat and oats. In all treatments, cholesterol concentration of epididymal fat and liver were greater in the SBO-fed than in the T-fed rats.     

Cholesteremia in Japanese quail: response to a mixture of vitamins C and E and choline chloride

Five-week old, male, Japanese quail (Coturnix coturnix japonica) were given ad libitum access to glucose- soybean meal-10% fat diets containing 0, 0.25, 0.5, or 1% cholesterol, with or without the addition of a vitamin supplement (vitamin C--1 g/kg of diet, vitamin E--30 I.U./kg of diet and choline chloride--5.5 g/kg of diet). After 12 weeks, 9 quail from the 24 quail fed each diet were killed and the total cholesterol concentration of serum, liver, kidney, and aorta was determined. Cholesterol concentrations of these organs increased with increasing levels of dietary cholesterol. The vitamin supplementation enhanced the increase in the cholesterol concentration of serum and kidney, lessened the elevation of the liver cholesterol concentration and had no effect on the aorta cholesterol concentration. The remaining quail were fed the same diets, for a subsequent 12 week period, except that cholesterol was deleted. At the termination of the experiment, the total cholesterol concentration of serum, liver, and kidney returned to control level for all treatments in which organ cholesterol concentrations had been increased previously. Aortic cholesterol concentration decreased during the second 12 week period (0.5 and 1% cholesterol diets fed for the first 12 weeks), however, the aortic cholesterol concentration remained higher than those of the control at 24 weeks. No significant effect of vitamin supplementation on organ cholesterol concentration was noted at 24 weeks although serum cholesterol concentration was significantly lower for the vitamin- fed groups at all levels of dietary cholesterol. Aortic ahteromata were observed at both 12 and 24 weeks in all groups fed 0.5 and 1% cholesterol.