Ernst J. Schaefer

Gemfibrozil for the secondary prevention of coronary heart disease in men with low levels of high-density lipoprotein cholesterol

BACKGROUND Although it is generally accepted that lowering elevated serum levels of low-density lipoprotein (LDL) cholesterol in patients with coronary heart disease is beneficial, there are few data to guide decisions about therapy for patients whose primary lipid abnormality is a low level of high-density lipoprotein (HDL) cholesterol. METHODS We conducted a double-blind trial comparing gemfibrozil (1200 mg per day) with placebo in 2531 men with coronary heart disease, an HDL cholesterol level of 40 mg per deciliter (1.0 mmol per liter) or less, and an LDL cholesterol level of 140 mg per deciliter (3.6 mmol per liter) or less. The primary study outcome was nonfatal myocardial infarction or death from coronary causes. RESULTS The median follow-up was 5.1 years. At one year, the mean HDL cholesterol level was 6 percent higher, the mean triglyceride level was 31 percent lower, and the mean total cholesterol level was 4 percent lower in the gemfibrozil group than in the placebo group. LDL cholesterol levels did not differ significantly between the groups. A primary event occurred in 275 of the 1267 patients assigned to placebo (21.7 percent) and in 219 of the 1264 patients assigned to gemfibrozil (17.3 percent). The overall reduction in the risk of an event was 4.4 percentage points, and the reduction in relative risk was 22 percent (95 percent confidence interval, 7 to 35 percent; P=0.006). We observed a 24 percent reduction in the combined outcome of death from coronary heart disease, nonfatal myocardial infarction, and stroke (P< 0.001). There were no significant differences in the rates of coronary revascularization, hospitalization for unstable angina, death from any cause, and cancer. CONCLUSIONS Gemfibrozil therapy resulted in a significant reduction in the risk of major cardiovascular events in patients with coronary disease whose primary lipid abnormality was a low HDL cholesterol level. The findings suggest that the rate of coronary events is reduced by raising HDL cholesterol levels and lowering levels of triglycerides without lowering LDL cholesterol levels.

The Effect of Dietary Supplementation with n—3 Polyunsaturated Fatty Acids on the Synthesis of Interleukin-1 and Tumor Necrosis Factor by Mononuclear Cells

We examined whether the synthesis of interleukin-1 or tumor necrosis factor, two cytokines with potent inflammatory activities, is influenced by dietary supplementation with n-3 fatty acids. Nine healthy volunteers added 18 g of fish-oil concentrate per day to their normal Western diet for six weeks. We used a radioimmunoassay to measure interleukin-1 (IL-1 beta and IL-1 alpha) and tumor necrosis factor produced in vitro by stimulated peripheral-blood mononuclear cells. With endotoxin as a stimulus, the synthesis of IL-1 beta was suppressed from 7.4 +/- 0.9 ng per milliliter at base line to 4.2 +/- 0.5 ng per milliliter after six weeks of supplementation (43 percent decrease; P = 0.048). Ten weeks after the end of n-3 supplementation, we observed a further decrease to 2.9 +/- 0.5 ng per milliliter (61 percent decrease; P = 0.005). The production of IL-1 alpha and tumor necrosis factor responded in a similar manner. Twenty weeks after the end of supplementation, the production of IL-1 beta, IL-1 alpha, and tumor necrosis factor had returned to the presupplement level. The decreased production of interleukin-1 and tumor necrosis factor was accompanied by a decreased ratio of arachidonic acid to eicosapentaenoic acid in the membrane phospholipids of mononuclear cells. We conclude that the synthesis of IL-1 beta, IL-1 alpha, and tumor necrosis factor can be suppressed by dietary supplementation with long-chain n-3 fatty acids. The reported antiinflammatory effect of these n-3 fatty acids may be mediated in part by their inhibitory effect on the production of interleukin-1 and tumor necrosis factor.

Consuming fructose-sweetened, not glucose-sweetened, beverages increases visceral adiposity and lipids and decreases insulin sensitivity in overweight/obese humans

Studies in animals have documented that, compared with glucose, dietary fructose induces dyslipidemia and insulin resistance. To assess the relative effects of these dietary sugars during sustained consumption in humans, overweight and obese subjects consumed glucose- or fructose-sweetened beverages providing 25% of energy requirements for 10 weeks. Although both groups exhibited similar weight gain during the intervention, visceral adipose volume was significantly increased only in subjects consuming fructose. Fasting plasma triglyceride concentrations increased by approximately 10% during 10 weeks of glucose consumption but not after fructose consumption. In contrast, hepatic de novo lipogenesis (DNL) and the 23-hour postprandial triglyceride AUC were increased specifically during fructose consumption. Similarly, markers of altered lipid metabolism and lipoprotein remodeling, including fasting apoB, LDL, small dense LDL, oxidized LDL, and postprandial concentrations of remnant-like particle-triglyceride and -cholesterol significantly increased during fructose but not glucose consumption. In addition, fasting plasma glucose and insulin levels increased and insulin sensitivity decreased in subjects consuming fructose but not in those consuming glucose. These data suggest that dietary fructose specifically increases DNL, promotes dyslipidemia, decreases insulin sensitivity, and increases visceral adiposity in overweight/obese adults.

Familial lipoprotein disorders in patients with premature coronary artery disease.

BackgroundGenetic lipoprotein disorders have been associated with premature coronary artery disease (CAD). Methods and ResultsThe prevalence of such disorders was determined in 102 kindreds (n=603 subjects) in whom the proband had significant CAD documented by angiography before the age of 60 years. Fasting plasma cholesterol, triglyceride, low density lipoprotein (LDL) cholesterol, apolipoprotein (apo) B, and lipoprotein (a) [Lp(a)] values above the 90th percentile and high density lipoprotein (HDL) cholesterol and apo A-I below the 10th percentile of age- and sex-specific norms were defined as abnormal. An abnormality was noted in 73.5% of probands compared with 38.2% in age-matched controls (p<0.001), with a low HDL cholesterol level (hypoalphalipoproteinemia) being the most common abnormality (39.2% of cases). In these kindreds, 54% had a defined phenotypic familial lipoprotein or apolipoprotein disorder. The following frequencies were observed: Lp(a) excess, 18.6% (includes 12.7% with no other dyslipidemias); hypertriglyceridemia with hypoalphalipoproteinemia, 14.7%; combined hyperlipidemia, 13.7% (11.7% with and 2.0% without hypoalphalipoproteinemia); hyperapobetalipoproteinemia (elevated apo B only), 5%; hypoalphalipoproteinemia, 4%; hypercholesterolemia (elevated LDL only), 3%; hypertriglyceridemia, 1%; decreased apo A-I only, 1%. Overall, 54% of the probands had a familial dyslipidemia; unclassifiable lipid disorders (spouse also affected) were found in 3%. No identifiable familial dyslipidemia was noted in 43% of kindreds of those; nearly half (45%) had a sporadic lipid disorder. Parent-offspring and proband-spouse correlations for these biochemical variables revealed that lipoprotein and apolipoprotein levels are in part genetically determined, with Lp(a) showing the highest degree of parent-offspring correlation. ConclusionsOur data indicate that more than half of patients with premature CAD have a familial lipoprotein disorder, with Lp(a) excess, hypertriglyceridemia with hypoalphalipoproteinemia, and combined hyperlipidemia with hypoalphalipoproteinemia being the most common abnormalities.

Evidence for Association and Genetic Linkage of the Angiotensin-Converting Enzyme Locus With Hypertension and Blood Pressure in Men but Not Women in the Framingham Heart Study

BACKGROUND There is controversy regarding the association of the angiotensin-converting enzyme deletion-insertion (ACE D/I) polymorphism with systemic hypertension and with blood pressure. We investigated these relations in a large population-based sample of men and women by using association and linkage analyses. METHODS AND RESULTS The study sample consisted of 3095 participants in the Framingham Heart Study. Blood pressure measurements were obtained at regular examinations. The ACE D/I polymorphism was identified by using a polymerase chain reaction assay. In logistic regression analysis, the adjusted odds ratios for hypertension among men for the DD and DI genotypes were 1.59 (95% confidence interval [CI], 1.13 to 2.23) and 1.18 (95% CI, 0.87 to 1.62), respectively, versus II (chi2 P=.02). In women, adjusted odds ratios for the DD and DI genotypes were 1.00 (95% CI, 0.70 to 1.44) and 0.78 (95% CI, 0.56 to 1.09), respectively (P=.14). In linear regression analysis, there was an association of the ACE DD genotype with increased diastolic blood pressure in men (age-adjusted P=.03, multivariate-adjusted P=.14) but not women. Quantitative trait linkage analyses in 1044 pairs of siblings, by using both ACE D/I and a nearby microsatellite polymorphism of the human growth hormone gene, supported a role of the ACE locus in influencing blood pressure in men but not in women. CONCLUSIONS In our large, population-based sample, there is evidence for association and genetic linkage of the ACE locus with hypertension and with diastolic blood pressure in men but not women. Our data support the hypothesis that ACE, or a nearby gene, is a sex-specific candidate gene for hypertension. Confirmatory studies in other large population-based samples are warranted.

Apolipoprotein E Alleles and Risk of Coronary Disease: A Meta-analysis

A meta-analysis was undertaken to assess the impact of apolipoprotein E (apo E) alleles (epsilon 2, epsilon 3, and epsilon 4) on coronary disease in 14 published observational studies (9 clinical coronary disease and 5 coronary angiography). In comparison with epsilon 3, the epsilon 4 allele was associated with greater odds for coronary heart disease, and summary estimates of the odds ratios (ORs) and (95% confidence intervals) for both sexes combined were OR = 0.98 (0.85-1.14) for epsilon 2 and OR = 1.26 (1.13-1.41) for epsilon 4. Separate analyses for men and women showed similar associations. In angiographic studies the relative odds for significant coronary artery disease among both sexes combined was OR = 0.76 (0.55-1.05) for epsilon 2 and OR = 1.11 (0.88-1.40) for epsilon 4. The overall impression is that epsilon 4 is associated with clinical and coronary disease and that results are similar in men and women.

Low-Density Lipoprotein and High-Density Lipoprotein Particle Subclasses Predict Coronary Events and Are Favorably Changed by Gemfibrozil Therapy in the Veterans Affairs High-Density Lipoprotein Intervention Trial

Background— Changes in conventional lipid risk factors with gemfibrozil treatment only partially explain the reductions in coronary heart disease (CHD) events experienced by men in the Veterans Affairs High-Density Lipoprotein Intervention Trial (VA-HIT). We examined whether measurement of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) particle subclasses provides additional information relative to CHD risk reduction. Methods and Results— This is a prospective nested case-control study of 364 men with a new CHD event (nonfatal myocardial infarction or cardiac death) during a 5.1-year (median) follow-up and 697 age-matched controls. Nuclear magnetic resonance (NMR) spectroscopy was used to quantify levels of LDL and HDL particle subclasses and mean particle sizes in plasma obtained at baseline and after 7 months of treatment with gemfibrozil or placebo. Odds ratios for a 1-SD increment of each lipoprotein variable were calculated with adjusted logistic regression models. Gemfibrozil treatment increased LDL size and lowered numbers of LDL particles (−5%) while raising numbers of HDL particles (10%) and small HDL subclass particles (21%). Concentrations of these LDL and HDL particles achieved with gemfibrozil were significant, independent predictors of new CHD events. For total LDL and HDL particles, odds ratios predicting CHD benefit were 1.28 (95% CI, 1.12 to 1.47) and 0.71 (95% CI, 0.61 to 0.81), respectively. Mean LDL and HDL particle sizes were not associated with CHD events. Conclusions— The effects of gemfibrozil on NMR-measured LDL and HDL particle subclasses, which are not reflected by conventional lipoprotein cholesterol measures, help to explain the demonstrated benefit of this therapy in patients with low HDL cholesterol.

Low density lipoprotein particle size and coronary artery disease.

Decreased plasma low density lipoprotein (LDL) particle size has been associated with premature coronary artery disease (CAD). We examined LDL particle size by 2-16% gradient gel electrophoresis in 275 men with CAD (greater than 75% cross-sectional-area stenosis) and 822 controls. Seven major LDL size bands (with LDL-1 [d = 1.025-1.033 g/ml] being the largest and LDL-7 [d = 1.050-1.063 g/ml, the smallest]) were identified. Because most subjects had two or more adjacent LDL bands, an LDL score was calculated for each subject, with the relative area in each band taken into consideration. Four major LDL particle size groups were classified in the present studies: large LDL, intermediate LDL, small LDL, and very small LDL. The use of beta-blockers was significantly associated with smaller LDL particles. After adjusting for use of this medication, small LDL particles were still more prevalent in CAD patients (39%) compared with controls (27%). The prevalence of large LDL particles was lower in CAD patients (3%) than in controls (24%). Intermediate LDL particles were the most prevalent in both groups, 49% in CAD patients and 46% in controls. The difference in LDL particle size between CAD patients and controls was not independent but was highly associated (p less than 0.0001) with elevated triglyceride levels and decreased high density lipoprotein (HDL) cholesterol levels. Significantly higher LDL cholesterol levels were found in subjects with intermediate and small LDL particles than in those with large or very small LDL particles.(ABSTRACT TRUNCATED AT 250 WORDS)

Automated enzymatic standardized lipid analyses for plasma and lipoprotein fractions

Excellent normal ranges for plasma lipid and lipoprotein cholesterol levels have been developed by the Lipid Research Clinics program, standardized by the Centers for Disease Control (CDC). However these values were generated by methods not currently in use in most clinical chemistry laboratories. Automated enzymatic methods for cholesterol, triglycerides and free glycerol determinations, as well as a dextran sulfate-Mg2+ procedure for separation of high density lipoproteins (HDL) with standardization are described. Similar methods for the measurement of unesterified cholesterol and phospholipids are also given. Serum pools for total cholesterol with values ranging from 1220-3490 mg/l produced coefficients of variation (CV) less than or equal to 2.85%; reference values for low total cholesterol samples in a range of 280-727 mg/l gave CV of 4.35% or less; HDL cholesterol reference values of 265-640 mg/l yielded CV less than or equal to 3.70%; and values for triglycerides between 0.74 and 3.05 mmol/l gave CV of 4.22% or less through three to eight testing cycles (9-24 mth). These data indicate that long term CDC standardization of total cholesterol, triglycerides, and HDL cholesterol can be obtained with automated enzymatic methods utilizing commercially available reagents.

Association of Cholesteryl Ester Transfer Protein–TaqIB Polymorphism With Variations in Lipoprotein Subclasses and Coronary Heart Disease Risk : The Framingham Study

Cholesteryl ester transfer protein (CETP) facilitates the exchange of triglycerides and cholesteryl esters between lipoprotein particles, a key step in reverse cholesterol transport in humans. Variations at the CETP locus have been shown to be determinants of the levels and activity of CETP and high density lipoprotein (HDL) plasma concentration. The associations of the common CETP polymorphism, TaqIB in intron 1, with lipoprotein levels and particle size distribution, CETP activity, and coronary heart disease (CHD) risk were examined in a population-based sample of 1411 men and 1505 women from the Framingham Offspring Study. The B2 allele frequency was 0.444 in men and 0.433 in women, and its presence was significantly (P<0.05) associated with decreased CETP activity. B1B1 men had lower HDL cholesterol (HDL-C) levels (1.07 mmol/L) compared with B1B2 (1.14 mmol/L) and B2B2 (1.18 mmol/L) men (P<0.001). Likewise, B1B1 women had lower HDL-C levels (1.40 mmol/L) compared with B1B2 (1.46 mmol/L) and B2B2 (1.53 mmol/L) women (P<0.001). In men, the B2 allele was associated with increased particle size for HDL and low density lipoprotein. In women, a similar effect was demonstrated only for HDL particle size. The odds ratio for prevalent CHD associated with the B2 allele was 0.696 (P=0.035) in men. After adjusting for age, body mass index, systolic blood pressure, diabetes, smoking, alcohol consumption, beta-blocker use, total cholesterol, and HDL-C, this odds ratio was 0.735 (P=0.187), suggesting that the protective effect of the B2 allele was due in part to its association with HDL-C levels. No significant protective effects were observed in women. These data demonstrate that variation at the CETP gene locus is a significant determinant of HDL-C levels, CETP activity, and lipoprotein size in this population. Moreover, these effects appear to translate into a lower CHD risk among those men with the B2 allele.