Magnitude of dietary effects on plasma cholesterol concentration: role of sex and apolipoprotein E phenotype

Diet-induced atherosclerosis in mice heterozygous and homozygous for apolipoprotein E gene disruption

With the aim of establishing whether a genetically reduced capability of producing apolipoprotein E (apo E) can affect atherogenesis, we have compared the consequences of dietary stress on normal mice and on mice heterozygous or homozygous for a disrupted apo E gene. A dramatically accelerated development of lesions occurred in the vasculature of the homozygous mutants as a result of feeding an atherogenic diet for 12 wk, and extensive deposition of lipid-filled macrophages was found outside the cardiovascular system. In nine heterozygotes fed the atherogenic diet for 12 wk, the amount of apo E in their total plasma lipoproteins increased to a level comparable to normal, but all nine developed much larger foam cell lesions in their proximal aorta than those found in 3 of 9 normal mice fed the same diet. The other six normals had no lesions. Our study demonstrates that heterozygous mice with only one functional apo E gene are more susceptible to diet-induced atherosclerosis than are normal, two-copy mice. Genetically determined quantitative limitations of apo E could, therefore, have similar effects in humans when they are stressed by an atherogenic diet.

ApoA-IV phenotype affects diet-induced plasma LDL cholesterol lowering

The National Cholesterol Education Program (NCEP) recommends that dietary total fat, saturated fat, and cholesterol intake be reduced to < or = 30% of calories, < 10% of calories, and < 300 mg/d, respectively (step 1 diet), in the general population to reduce plasma low-density lipoprotein cholesterol (LDL-C) levels and heart disease risk. We examined the LDL-C-lowering response to such a diet (26% fat, 8% saturated fat, and 201 mg/d cholesterol) compared with an average American diet (39% fat, 15% saturated fat, and 435 mg cholesterol/d) in 153 subjects using diet periods of 4 through 24 weeks for each diet phase. The mean LDL-C reduction was 13% in men (n = 93) and 7% in postmenopausal women (n = 60). The effect of apolipoprotein (apo) A-IV phenotype on responsiveness was examined. LDL-C lowering in men was significantly (P < .005) less (7%) for 17 apoA-IV (1/2) subjects than for 76 apoA-IV (1/1) subjects (16%). In women, 7% lowering was observed in both 12 apoA-IV (1/2) subjects and 48 apoA-IV (1/1) subjects. ApoA-IV phenotype had a significant effect on plasma high-density lipoprotein cholesterol levels during both dietary periods; women carrying the apoA-IV-2 allele had higher levels than those homozygous for the apoA-IV-1 allele. The opposite was true for triglyceride levels, but only during the period when the subjects consumed the high-fat, high-cholesterol diet.(ABSTRACT TRUNCATED AT 250 WORDS)

A dose-response study of the effects of dietary cholesterol on fasting and postprandial lipid and lipoprotein metabolism in healthy young men

Despite many previous studies, controversy remains concerning the effects of dietary cholesterol on plasma cholesterol concentrations. In addition, the focus of previous studies has been fasting lipid and lipoprotein concentrations; there are no published studies with postprandial measurements. We studied the effects of four levels of dietary cholesterol intake on fasting lipid, lipoprotein, and apoprotein levels, as well as postprandial lipid levels, in a group of young, healthy men who were otherwise eating a low-fat, American Heart Association step 1 diet. Twenty young, healthy men completed a randomized, four-way crossover design study to test the effects of an American Heart Association step 1 diet containing 0, 1, 2, or 4 eggs per day. Dietary cholesterol ranged from 128 to 858 mg cholesterol per day. Each diet was eaten for 8 weeks, with a break between diets. Three fasting blood samples were obtained at the end of each diet period. In addition, blood samples were obtained just before and 2, 4, and 6 hours after ingestion of a standard lunch containing the various amounts of egg cholesterol. We also obtained blood 4 and 8 hours after the subjects ingested a standard, high-fat formula. Fasting plasma total cholesterol concentrations increased by 1.47 mg/dL (0.038 mmol/L) for every 100 mg dietary cholesterol added to the diet (P < .001). Low-density lipoprotein (LDL) cholesterol increased in parallel. Responsiveness varied but appeared to be normally distributed. Fasting plasma apoprotein B concentrations increased approximately 10% between the 0- and 4-egg diets and were correlated with changes in total and LDL cholesterol concentrations. Although there was a trend toward a greater response in men with an apoprotein E4 allele, this was not statistically significant. Fasting plasma cholesteryl ester transfer protein levels were higher only on the 4-egg diet, and changes in cholesteryl ester transfer protein levels between the 0- and 4-egg diets correlated with changes in total and LDL cholesterol. There were no differences in the postlunch or post-fat-formula responses of plasma lipids across the diets. Incubation of the 4-hour postlunch serum with J774 macrophages did not affect cell cholesteryl ester content at any level of dietary cholesterol. Cellular free cholesterol levels were slightly higher on each of the egg-containing diets versus the 0-egg diet. In summary, increases in dietary cholesterol resulted in linear increases in fasting total and LDL cholesterol in young, healthy men.(ABSTRACT TRUNCATED AT 400 WORDS)

Apolipoprotein E and B polymorphisms--longevity factors assessed in nonagenarians

To test if the prevalence of genetic risk factors for coronary heart disease (CHD) is low in individuals who have reached an extremely old age, the allele frequencies of apolipoprotein E (apo E) and B (apo B) polymorphisms and plasma lipoprotein(a) levels were investigated in nonagenarians and in younger control groups. The frequency of the epsilon 4 allele of apo E was significantly lower in the nonagenarians than in the middle-aged and young adults (P < 0.05). Also, the frequency of EcoRI allele R- of apo B was low in the nonagenarians, whereas the allele frequency for the XbaI polymorphism of apo B and plasma lipoprotein(a) concentrations did not differ between the nonagenarians and the younger groups. These findings strongly suggest that the presence of these potential genetic risk factors for CHD, namely the epsilon 4 allele of apo E and the R- allele of apo B, decreases the probability of an individual reaching an extremely old age.

Long-term effects of three fat-modified diets in hypercholesterolemic subjects

Altogether 160 free living subjects (aged 30-60 years) most of whom had moderate hypercholesterolemia were randomised into the following diet groups to find out long-term effects of different fat-modified diets: (1) control diet 35/14:10:4 (energy percents from fat/saturated:monounsaturated:polyunsaturated fatty acids in actual diets); (2) AHA type diet 32/10:8:8; (3) monoene-enriched diet 34/11:11:5; (4) reduced-fat diet 30/12:8:3. LDL cholesterol fell equally with the AHA type diet (4.54 +/- 0.97 vs. 4.21 +/- 0.89 mmol/l (mean +/- S.D., 0 vs. 6 months), P = 0.001) and with the monoene-enriched diet (4.55 +/- 0.95 vs. 4.25 +/- 0.95 mmol/l, P = 0.004) during the 6-month study. Moderate amounts of polyenes or monoenes as part of natural diets did not decrease HDL cholesterol level in the long term. Serum lipid values remained unchanged with the reduced-fat diet. Analysis by apolipoprotein E phenotypes showed a decrease in LDL cholesterol only in subjects with phenotype 3/3 in the monoene-enriched group (-8.6 +/- 8.7 vs. +1.3 +/- 15.4, percent change in LDL cholesterol E 3/3 vs. E 4/3 + 4/4), but in the AHA type group LDL cholesterol decreased similarly in phenotypes E 3/3 and E 4/3 + 4/4 (-6.9 +/- 10.1 vs -6.9 +/- 16.5).

Metabolism of cholesterol and apolipoprotein B in celiac disease

To test the association of cholesterol malabsorption with cholesterol and lipoprotein metabolism, we determined low-density lipoprotein (LDL) apolipoprotein (apo) B kinetics simultaneously with measurements of cholesterol absorption and synthesis in six patients with celiac disease (CD) before and during the gluten-free diet (GFD). The basal condition was characterized by low cholesterol absorption, enhanced cholesterol synthesis, and high removal and transport rate of LDL apo B. The GFD markedly improved cholesterol absorption and decreased intestinal influx of cholesterol, fecal neutral steroids, and cholesterol synthesis. Of plasma total and lipoprotein cholesterol levels, only plasma high-density lipoprotein (HDL) was enhanced by the GFD proportionately to cholesterol absorption. The plasma LDL apo B level remained unchanged because of simultaneous decreases in the fractional catabolic rate (FCR) and transport rate of LDL apo B. In fact, the more cholesterol absorption was improved by the GFD, the more the FCR and transport rate for LDL apo B were decreased, and their reductions were closely related to the decrease in cholesterol synthesis. The present results show that cholesterol absorption, cholesterol synthesis, hepatic B/E receptor activity, and LDL apo B transport rate are closely associated with each other and that their levels can change markedly with no detectable change in serum levels of LDL cholesterol or apo B.

Apolipoprotein B gene DNA polymorphisms are associated with macro- and microangiopathy in non-insulin-dependent diabetes mellitus

The relationship between diabetic macroangiopathy or microangiopathy and apolipoprotein B (apoB) polymorphism was studied in 139 male and 129 female patients with non-insulin-dependent diabetes (NIDDM) mellitus, comprising consecutive patients with poor diabetic control (HBA1 13.2% +/- 2.7 (SD)) referred to our hospital. Plasma cholesterol and triglyceride concentrations were higher in the patients who were homozygous for the X2 allele (presence of XbaI cleavage site). Patients with the X1 allele (absence of XbaI cleavage site) tended to have a higher frequency of macroangiopathy, although the differences were not statistically significant. There was no difference in the prevalence of microangiopathy between the groups. In subjects with only an R1 allele (= R+; homozygous for the presence of EcoRI cleavage site) the prevalence of coronary heart disease (CHD) was observed to be high (61.9%) as compared to the subjects possessing an R2 allele (= R-; homozygous or heterozygous for the absence of the EcoRI cleavage site) (46.7%; p < 0.02). When the polymorphisms XbaI (subjects homozygous for the absence of the cutting site = X+; subjects homozygous or heterozygous for the presence of the cutting site = X-) and EcoRI were combined, the prevalence of macroangiopathy was observed to be high in X+R+ (80.0%) as compared with X+R- (44.2%), X-R+ (56.8%) and X-R- (50.0%) (p < 0.03). The prevalence of macroangiopathy tended to be particularly high in patients with the apoprotein E4 allele (phenotype E4/4 or E4/3), combined with either X+ or R+.(ABSTRACT TRUNCATED AT 250 WORDS)

Gallstone cholesterol content is related to apolipoprotein E polymorphism

BACKGROUND

The genetically determined phenotypes of apolipoprotein E are related to variations in lipoprotein levels and in the enterohepatic metabolism of cholesterol and bile acids. The present study was designed to elucidate the role of apolipoprotein E polymorphism in gallstone formation.

METHODS

Apolipoprotein E phenotype was determined in 169 consecutive cholecystectomy patients and in 200 controls. The cholesterol content of the gallstones (n = 169), the presence of cholesterol monohydrate crystals of fresh gallbladder bile (n = 142), and the nucleation time (n = 35) were also analyzed.

RESULTS

The median cholesterol content of the gallstones was higher in the apolipoprotein E4 category (phenotypes E4/4 and E4/3, 97%) than in the E3 (E3/3, 78%) and E2 patients (E2/2 and E2/3, 76%, P = 0.0003). In E4 patients, cholesterol crystals were found immediately after surgery in 27 of 40 (68%), whereas in E3 and E2 groups in 36 of 88 (41%), and 4 of 14 (29%) of the patients (P = 0.0001). The median nucleation time in E4 patients (2.5 days) was shorter than in patients with E3 (5.5 days) or E2 (6.0 days) (P = 0.0016).

CONCLUSIONS

These data indicate that apolipoprotein E polymorphism affects cholesterol content of cholelithiasis. We suggest that this phenomenon is mediated by the altered formation of cholesterol monohydrate crystals in different apolipoprotein E phenotypes.

Apolipoprotein E phenotype is related to macro- and microangiopathy in patients with non-insulin-dependent diabetes mellitus

The role of apoliprotein E (apo E) in modulating the susceptibility of individuals with non-insulin-dependent diabetes mellitus (NIDDM) to atherosclerotic vascular disease was studied in 143 male and 128 female patients with NIDDM. The data show that the apolipoprotein phenotype E2 somehow protects from macrovascular complications in NIDDM both in men and women. E2 also tends to protect from microvascular complications. In contrast, apo E phenotypes E4/4 and E4/3 tend to increase the risk for macroangiopathy in NIDDM patients. The lower prevalence of macroangiopathy in the subjects with E2 was associated with lower plasma total and LDL cholesterol concentrations and low plasma lipoprotein(a) levels. Overall, this study demonstrates the role of the apo E phenotype to modulate the risk for diabetic complications in patients with NIDDM. The confirmation of the association of apo E polymorphism with diabetic complications warrants, however, long-term follow-up studies.

XbaI polymorphism of the apolipoprotein B gene and plasma lipid and lipoprotein response to dietary fat and cholesterol: a clinical trial

A dietary trial was carried out on a group of offspring whose parents were hospitalized for an acute myocardial infarction. The XbaI Restriction Fragment Length Polymorphism (RFLP) was used to examine the genetic contribution of variation at this apo B locus to the response of lipids and lipoproteins to dietary manipulations. Twenty participants were homozygotes for the 8.0 kb fragment (X1X1), two were homozygotes for the 5.0 kb fragment (X2X2), and 15 were heterozygotes (X1X2). Subjects were randomized to a 5-week crossover study. Half began on a low SFA--cholesterol (LSC) diet for 5 weeks and, after a washout period of 4 weeks, they were placed on a high SFA--cholesterol (HSC) diet for a second period of 5 weeks. This order was reversed in the second group of participants. Significant changes in total cholesterol, LDL-C, and apo B were observed when subjects were moved from the LSC to the HSF diet. The corresponding average change induced by the dietary manipulations in X1X1 subjects compared with subjects with X2 allele were: 18.1 +/- 17.6 mg/dl and 9.5 +/- 19.6 mg/dl for total cholesterol and 15.8 +/- 15.3 mg/dl and 4.8 +/- 20.9 mg/dl for LDL-C, respectively. Our observation indicated that variation at the apo B XbaI locus may interact with baseline levels to determine individual dietary response in LDL-C level. However, the differences between the genotypic classes were not statistically significant, suggesting that the apo B XbaI locus is not a major determinant of interindividual differences in lipid and lipoprotein response to diet in this population.

A controlled study on the effect of beta-glucan-rich oat bran on serum lipids in hypercholesterolemic subjects: relation to apolipoprotein E phenotype

The effects of beta-glucan-rich oat bran on serum lipids and lipoproteins were examined in a randomized 8-week study. After a 4-week run-in phase, subjects with mild to moderate hypercholesterolemia [serum total cholesterol (TC) 5.5-8.5 mmol/l] on cholesterol-lowering diets were randomly allocated to an oat bran (10.3 g beta-glucan/day) or wheat bran group. Thirty-six subjects (20 in the oat bran group, 16 in the wheat bran group) completed the study. The diet was identical in both groups during the trial and no significant changes in body weight were found. Serum TC and low-density lipoprotein cholesterol (LDL-C) significantly declined in the oat bran group during the first 4 weeks from 7.03 +/- 0.81 to 6.72 +/- 0.97 (p = 0.028) and from 4.90 +/- 0.69 to 4.61 +/- 0.89 mmol/l (p = 0.038), respectively, but at 8 weeks the values were not significantly different from baseline. Changes in serum TC were mainly confined to those who ate at least two-thirds of the planned daily dose of oat bran. In wheat bran group no changes were observed in serum TC or LDL-C levels. Apolipoprotein A1 and B did not change significantly in either group. Only subjects with apolipoprotein E 3/3 phenotype (n = 12) had hypocholesterolemic response to oat bran at 4 weeks, but no change was found in those with apolipoprotein E 4/4 or 4/3 (n = 7).(ABSTRACT TRUNCATED AT 250 WORDS)

Cholesterol absorption, elimination, and synthesis related to LDL kinetics during varying fat intake in men with different apoprotein E phenotypes

Cholesterol absorption, fecal elimination, and synthesis and low density lipoprotein (LDL) metabolism were measured in 29 middle-aged men while on their normal diet and a diet low in fat and cholesterol, and the obtained values were related to apoprotein (apo) E phenotypes. Basal cholesterol absorption efficiency was positively related to production rate (PR) for LDL apo B and negatively to cholesterol synthesis (measured by fecal steroids and dietary cholesterol), which in turn was negatively associated with the LDL level and positively with the fractional removal (FCR) of LDL apo B. The apo E subscript (e.g., E2/2 = 1, E2/3 = 2, etc.) was positively associated with cholesterol absorption and the LDL apo B and cholesterol levels and negatively with cholesterol synthesis and FCR for LDL apo B. Effective bile acid and cholesterol synthesis, fecal elimination of cholesterol, removal of LDL apo B, and low cholesterol absorption characterized men with the epsilon 2 allele. Reduction of dietary fat and cholesterol intakes lowered LDL cholesterol levels and cholesterol absorption but increased cholesterol synthesis proportionally to the apo E subscript; the FCR and PR for LDL apo B were significantly increased and decreased, respectively. The decrease in absorption was related to enhanced removal of LDL apo B and synthesis of cholesterol. During the modified diet, cholesterol metabolism was poorly related to LDL, apo E phenotypes, and LDL apo B kinetics. A positive correlation of cholesterol absorption with dietary fat intake in combined studies suggests that a dietary fat reduction-associated decrease in LDL cholesterol is at least partly caused by reduced cholesterol absorption.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of gender, body mass index, and age on response of plasma lipids to dietary fat plus cholesterol

We have conducted a crossover, randomized, double-blind dietary trial that tested the hypothesis that gender influences the response of plasma lipids, in particular high density lipoprotein (HDL) cholesterol, to dietary fat plus cholesterol. Twenty-six men and 25 women were matched for age, low density lipoprotein (LDL) cholesterol, triglyceride, and body mass index (BMI). After a 2-week baseline low-fat (27% of calories), low-cholesterol period, subjects were given two isocaloric liquid supplements for 3 weeks each, one containing 31 g fat (56% saturated) and 650 mg cholesterol, and the other fat free. The baseline HDL2 cholesterol level was significantly higher in women: 0.41 versus 0.26 mmol/l (p less than 0.01). Importantly, women also showed a greater rise in HDL2 cholesterol concentration with the fat/cholesterol supplement: 0.09 versus 0.03 mmol/l (p less than 0.01). The greater increment in women was related to their higher baseline HDL2 cholesterol levels. With the fat and cholesterol supplement, LDL cholesterol values rose from 3.76 to 4.04 mmol/l in women and from 3.77 to 4.13 mmol/l in men. The baseline LDL cholesterol value was found to account for about 35% of the variance in the rise in LDL cholesterol level with fat and cholesterol supplementation in both men and women less than 50 years. In men only, there was a significant effect of age: the change in LDL cholesterol with the fat/cholesterol supplement was 0.16 mmol/l in those less than 50 and 0.54 mmol/l in those greater than 50 years old (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Cholesterol-rich diet induced changes in plasma lipids in relation to apolipoprotein E phenotype in healthy students

The hypothesis that apolipoprotein E (apoE) polymorphism modulates an individual's response to cholesterol-rich diet was tested in 36 healthy normolipidaemic students with apoE phenotypes E3/2 (n = 9), E3/3 (n = 11), E4/3 (n = 13) and E4/4 (n = 3). The subjects were instructed to eat their usual diets, omitting eggs, for three weeks (baseline). This was followed by a diet high in cholesterol (750 mg/day, from egg yolks) for three weeks (intervention) after which they returned to their normal diet (without eggs for three weeks). Concentrations of plasma lipids and apolipoprotein B, and the composition of total fatty acids were monitored. At baseline, there were no statistically significant differences in lipid concentrations between the phenotype groups. The cholesterol-rich diet induced significant increases in total cholesterol, LDL cholesterol, and apoB in all apoE groups (P less than 0.001). The magnitudes of these increases were similar in groups E3/2, E3/3, and E4/3, in which total cholesterol concentration rose by 13%, 18%, and 12%, respectively. Stronger responses were observed in the small group of E4/4 subjects, in whom the increases in total cholesterol, LDL cholesterol, and apoB were 2.3-fold (P = 0.054), 2.25-fold (P = 0.02) and 2.3-fold (P = 0.004), respectively, compared with all the other phenotypes studied.

Mechanisms of low density lipoprotein lowering by hypolipidemic agents

Most hypolipidemic agents have been developed to reduce to normal high plasma concentrations of low density lipoprotein (LDL), the most atherogenic substance in human plasma. Various agents work with many different mechanisms, some of which are not understood. Mechanistic studies are helpful--e.g., for understanding of the various effects of treatment, elucidating regulatory disturbances in different hyperlipidemias and selecting treatment for patients' specific problems. This paper assesses some of the agents that reduce the concentration of LDL focusing on various mechanistic pathways.