Lowering blood cholesterol to reduce coronary heart disease risk

Key recent findings provide definitive evidence that lowering blood cholesterol in humans reduces coronary heart disease risk. These research advances serve as the basis for national guidelines concerning the medical and public health implications of lowering blood cholesterol to prevent heart disease.     

Insulin resistance--a risk factor for coronary heart disease?

Fasting insulin secretion was assessed by measuring fasting serum C-peptide levels in 529 women and 399 men aged 18-90 years, to study the relationship between insulin secretion, insulin resistance and risk factors for coronary heart disease. Subjects with low serum high density lipoprotein (HDL) cholesterol levels showed higher mean serum insulin and C-peptide levels than subjects with normal HDL cholesterol levels. In male subjects these differences were significant for both serum insulin and serum C-peptide results (P less than 0.005). In female subjects serum insulin results differed significantly (P less than 0.0005) but for the difference in mean serum C-peptide levels P was equal to 0.012. Fasting serum C-peptide correlated negatively with serum HDL cholesterol. However, serum C-peptide also correlated with serum triglyceride and serum triglyceride correlated negatively with serum HDL cholesterol. Each correlation was statistically significant (P less than 0.001). Multiple regression analysis suggested that the apparent association of C-peptide with HDL cholesterol was a consequence of the interrelated association between C-peptide, triglyceride and HDL cholesterol. The analysis was consistent with the hypothesis that obesity and increased insulin resistance were associated with increased insulin secretion and in turn with high serum triglyceride levels and consequentially low levels of serum HDL cholesterol. The data were compatible with the suggestion that insulin resistance rather than fasting insulin concentration per se could be a risk factor for coronary heart disease.     

总胆固醇/高密度脂蛋白胆固醇比值预测冠心病危险程度的评价

目的 评价总胆固醇/高密度脂蛋白胆固醇(TC/HDL-C)比值预测冠心病危险程度的价值.方法回顾性分析250例冠心病患者的临床资料分为:稳定型心绞痛组(SA组),不稳定型心绞痛组(UA组),并另选125例健康者为对照组,测定两组的TC/HDL-C、总胆固醇(TC)、甘油三酯(TG)、低密度脂蛋白胆固醇(LDL-C)和HDL-C并比较其差异性和异常率.结果SA组及UA组TC、TG、LDL-C及TC/HDL-C均高于对照组(P<0.01),HDL-C低于对照组(P<0.01),HDL-C分别为(1.08±0.36)mmol/L、(1.03±0.29)mmol/L vs(1.66±0.67)mmol/L,SA组、UA组HDL-C、LDL-C及TC/HDL-C异常率与对照组比较差异有统计学意义(P<0.05),分别为36.9%、39.1%Vs 20.0%,32.0%、32.8%Vs 16.0%,65.6%、72.7%vs 38.6%.结论TC/HDL-C作为冠心病危险因素的预测价值和灵敏度高于单项血脂指标.     

非高密度脂蛋白胆固醇在冠心病危险性评估中的作用

目的探讨非高密度脂蛋白胆固醇(non-HDL-C)在冠心病危险性评估中的作用。方法对453例冠心病患者和336例健康对照血脂资料进行分析,比较non-HDL-C与其他血脂数据两组间差异的显著性,以及non-HDL-C和低密度脂蛋白胆固醇(LDL-C)的相关性。结果冠心病组non-HDL-C值[(4.02±1.20)mmol/L]明显高于健康对照组[(3.30±0.58)mmol/L],差异有统计学意义(t=10.132,P<0.001)。non-HDL-C在冠心病组和健康对照组间差异的显著性高于LDL-C和总胆固醇(TC)及三酰甘油(TG)。随着TG水平增高,non-HDL-C与LDL-C相关性下降。结论non-HDL-C对冠心病危险性评估作用优于LDL-C,而且方法简便易行,适合临床推广应用。     

The status of hypertriglyceridemia as a risk factor for coronary heart disease

The three-decade long controversy surrounding the status of triglycerides as an independent risk factor for coronary heart disease is presented. The studies that reported an association and the clinical trials of cholesterol-lowering medications are examined. Because of the inconsistency between the observational findings and the consistently negative clinical trial findings, treatment of isolated hypertriglyceridemia cannot be recommended at present.     

Lp(a) lipoprotein--an independent risk factor for coronary heart disease after menopause.

Lp(a) is an independent risk factor for recurrent atherosclerotic heart disease in men and women after menopause. Excess levels of Lp(a) are seen in both males and females, more common in Africans, African Americans, and Asian populations than in whites. Since the standard lipid profile does not report Lp(a), it has to be ordered separately. Screening for Lp(a) should be considered under the following circumstances: (a) patient or family history of premature atherosclerotic heart disease, (b) familial history of hyperlipidemia, (c) established atherosclerotic heart disease with a normal routine lipid profile, (d) hyperlipidemia refractory to therapy, and (e) history of recurrent arterial stenosis. Treatment options are (a) a new extended-release form of niacin 3 to 4 g daily (although most effective in lowering Lp(a) and in reducing atherosclerotic heart disease mortality rates, its use may be limited because of side effects); (b) estrogen replacement after menopause, (however, concomitant progesterone therapy dilutes the effectiveness of estrogens); (c) lowering LDL with statins (generally effective in atherosclerotic heart disease but has no effect on Lp(a) levels), (d) aspirin and antibiotics (may be effective when C-reactive protein levels are high); and (e) folic acid (reduces homocysteine levels). The general measures that halt the progression of CAD should always be adhered to, namely, maintaining normal weight, a daily exercise program, blood pressure control, a low-cholesterol-forming diet, and daily aspirin.     

Sunlight, cholesterol and coronary heart disease

We investigated the relationship between geography and incidence of coronary heart disease, looking at deficiency of sunlight and thus of vitamin D as a factor that might influence susceptibility and thus disease incidence. Sunlight deficiency could increase blood cholesterol by allowing squalene metabolism to progress to cholesterol synthesis rather than to vitamin D synthesis as would occur with greater amounts of sunlight exposure, and the increased concentration of blood cholesterol during the winter months, confirmed in this study, may well be due to reduced sunlight exposure. We show evidence that outdoor activity (gardening) is associated with a lower concentration of blood cholesterol in summer but not in the winter. We suggest that the geographical variation of coronary heart disease is not specific, but is seen in other diseases and sunlight influences susceptibility to a number of chronic diseases, of which coronary heart disease is one.      

Small,dense low-density lipoprotein as a risk factor for coronary heart disease

Summary Data from case-control and cross-sectional studies uniformly demonstrate an association between small, dense low-density lipoprotein and risk of coronary heart disease. This relationship may be attributable to the association of small, dense low-density lipoprotein with other atherogenic lipoproteins, the presence of the insulin resistance syndrome in subjects with small low-density lipoprotein, and/or the increased oxidative susceptibility of small, dense low-density lipoprotein particles. Furthermore, because small low-density lipoprotein appears to be a common trait in the general population, more than one of these atherogenic mechanisms may be operating simulataneously to increase risk of coronary heart disease.     

Erectile dysfunction as a risk factor for coronary heart disease: implications for prevention

There is now mounting evidence that erectile dysfunction (ED) is an early predictor of coronary heart disease (CHD). Men presenting with ED but no other cardiovascular symptoms provide an opportunity for the treating physician to test for asymptomatic CHD and to reduce CHD risk factors.     

血清总胆固醇与高密度脂蛋白胆固醇比值作为冠心病危险标志的意义

目的分析冠心病(CHD)患者的血脂水平,探讨血清总胆固醇(TC)与高密度脂蛋白胆固醇(HDL-C)比值作为CHD危险标志的临床意义。方法测定295例CHD患者的血清TC、三酰甘油(TG)、HDL-C及低密度脂蛋白胆固醇(LDL-C)水平,并计算TC/HDL-C比值。结果依据《中国成人血脂异常防治指南》颁布的血脂水平合适范围,CHD患者血清TC、TG及LDLC高于合适范围百分率分别为32.20%、34.24%及37.63%,血清HDL-C低于合适范围百分率为39.32%。血清TC/HDL-C比值高于合适范围百分率为57.29%。血清TC/HDL-C比值异常率显著高于血清TC、TG、HDL-C及LDL-C(χ2=37.540、31.576、19.066、22.866,P0.01)。结论与任一单项血脂检测相比,血清TC/HDL-C比值作为CHD危险标志可能更有临床意义,临床血脂检测报告单应增加TC/HDL-C比值。     

Analytical bias for cholesterol and the percent of the population deemed at risk for coronary heart disease

The effect of methodological bias on the population at risk is dependent on the location of the reference value in the distribution of the population. We fitted the cumulative distribution for cholesterol to a rational function and calculated the apparent reference values for four biased methods: Technicon SMAC (2.6%), DuPont aca (4.0 to 4.8%), Kodak DT-60 (-2.0 to -5.5%), and BMD Reflotron (-7.4 to -7.8%). With the true and apparent reference values for cholesterol and the rational function, we determined the percentage increase or decrease in the population deemed at risk for coronary heart disease. The population at risk increased by as much as 48% for methods with positive bias, and decreased by as much as 54% for methods with negative bias. If we restrict the percentage of the population incorrectly diagnosed to 3% and use reference values (cut points) recommended by the National Cholesterol Education Program, the maximum allowable methodological bias would be 1.6% for positive bias and -1.55% for negative bias. Therefore, an absolute methodological bias of 3% (as recommended by the Laboratory Standardization Panel) may be too liberal.     

Coronary vasomotor and blood flow responses to isoflavone-intact soya protein in subjects with coronary heart disease or risk factors for coronary heart disease

Results in animals suggest favourable coronary vasomotor actions of isoflavones; however, the effects of isoflavones on the human coronary circulation have not been determined. In the present study, we therefore investigated the effects of short-term isoflavone-intact soya protein ingestion on basal coronary arterial tone and stimulated vasoreactivity and blood flow in patients with CHD (coronary heart disease) or risk factors for CHD. Seventy-one subjects were randomized, double-blind, to isoflavone-intact soya protein [active; n=33, aged 58+/-8 years (mean+/-S.D.)] or isoflavone-free placebo (n=38, aged 61+/-8 years) for 5 days prior to coronary angiography. In 25 of these subjects, stimulated coronary blood flow was calculated from flow velocity, measured using intracoronary Doppler and coronary luminal diameter before and after intracoronary adenosine, ACh (acetylcholine) and ISDN (isosorbide dinitrate) infusions. Basal and stimulated coronary artery luminal diameters were measured using quantitative coronary angiography. Serum concentrations of the isoflavones genistein, daidzein and equol were increased by active treatment (P<0.001, P<0.001 and P=0.03 respectively). Basal mean luminal diameter was not significantly different between groups (active compared with placebo: 2.9+/-0.7 compared with 2.73+/-0.44 mm, P=0.31). There was no difference in luminal diameter, flow velocity and volume flow responses to adenosine, ACh or ISDN between groups. Active supplement had no effect on basal coronary artery tone or stimulated coronary vasoreactivity or blood flow compared with placebo. Our results suggest that short-term consumption of isoflavone-intact soya protein is neither harmful nor beneficial to the coronary circulation of humans with CHD or risk factors for CHD. These results are consistent with recent cautions placed on the purported health benefits of plant sterols.     

人巨细胞病毒感染作为冠心病独立危险因子的可能性探讨

背景目前对人巨细胞病毒( human cytomegalovirus, HCMV)感染与冠心病的关系及 HCMV感染可否作为冠心病的独立危险因子还存在争议.目的进一步探讨 HCMV感染与冠心病的关系及 HCMV感染可否作为冠心病的独立危险因子.设计单盲非随机的对照试验.地点、对象和方法选择广东医学院附属医院和第二附属医院住院患者 98例为冠心病组 (年龄 42～ 72岁 ),广东医学院健康志愿者 50例为对照组 (年龄 40～ 69岁 ,已经临床及实验室检查排除了心脏疾患 ),采用间接酶联免疫吸附测定( ELISA)检测两组的 HCMV-IgG, HCMV-IgM和 HCMV-IgA抗体阳性率和标本 450 nm吸光度值 /阴性对照 450 nm吸光度值( S/N值),聚合酶链反应( PCR)检测两组的 HCMV-DNA阳性率.主要观察指标两组患者 HCMV-IgG, HCMV-IgM和 HCMV-IgA抗体阳性率、 S/N值和 HCMV-DNA阳性率比较.结果冠心病组的 HCMV-IgG, HCMV-IgM, HCMV-IgA抗体阳性率分别为 91.8%, 15.3%和 16.3%,均明显高于对照组 (P《 0.01);冠心病组的 S/N值分别为 3.57± 1.29, 1.98± 0.35和 1.99± 0.31,均明显高于对照组 (P《 0.01); HCMV-DNA阳性率为 60.2%,明显高于对照组 (P《 0.01).HCMV抗体和 HCMV-DNA阳性率不受血清胆固醇、三酰甘油水平及是否伴有高血压和 /或糖尿病的影响(除 HCMV-IgM抗体阳性率在是否伴有高血压和 /或糖尿病两组间比较 P《 0.05外 ,余均为 P 》0.05).结论 HCMV感染可能与冠心病有关, HCMV感染可能可作为冠心病的独立危险因子.     

Asessing coronary heart disease risk and managing lipids.

Elevated low-density lipoprotein (LDL) and below normal high-density lipoprotein (HDL) cholesterol are risk factors for coronary heart disease (CHD). According to clinical guidelines, LDL cholesterol is the primary target for lipid-altering therapy. Many patients who develop CHD have LDL and HDL cholesterol levels that fall within the desirable or low-risk category; consequently, conventional measurements of plasma lipids may not accurately detect high-risk patients. This article discusses the clinical significance of lipoprotein subclasses and methods of measurement. Assessing lipoprotein subclasses provides a more comprehensive and efficacious therapeutic approach compared with the standard lipid profile.     

Diet and coronary heart disease. Helping patients reduce serum cholesterol level

Although coronary heart disease (CHD) remains the No. 1 cause of death in the United States, the CHD mortality rate has shown a recent decline. This has been attributed to lower fat consumption in the general population, with associated lower serum cholesterol levels. Thus, diet seems to be an important factor in controlling cholesterol level. Acting on this hypothesis, primary care physicians can help patients make appropriate dietary changes. We believe that persons at risk of hypercholesterolemia need to be identified in adolescence by measurement of total serum cholesterol level and that testing should be done every two years after age 25. The American Heart Association's prudent diet is recommended for all patients, especially those with a serum cholesterol level above 240 mg/dl. When dietary restriction does not bring the level within this limit, use of cholesterol-lowering agents is considered. To be lasting, dietary change must be gradual; realistic immediate and long-term goals should be established. In addition, the diet must be nutritionally sound and the patient must receive support from family members.