Low serum cholesterol and mortality. Which is the cause and which is the effect?

Optimal low-density lipoprotein levels: evidence from epidemiology and clinical trials

Aggressive lipid lowering was initially controversial due to evidence from epidemiologic studies that implied an increase in total mortality with low cholesterol levels combined with equivocal results from early trials utilizing bile acid resins or fibric acid derivatives. The advent of statin therapy allowed significant reductions of circulating lipid levels and clearly reduced cardiovascular morbidity and mortality. Additionally, in adequately powered trials, total mortality was also reduced. The optimal level of circulating low-density lipoprotein (LDL) has not been definitely established. However, recent clinical trials with aggressive lipid goals have established that LDL cholesterol can be significantly lowered below 100 mg/dL with improvement in both surrogate measurements and hard clinical endpoints. Ongoing clinical trials have been initiated that will determine the optimal level of LDL cholesterol that will insure cardiovascular benefits and establish the risk-benefit relationship of aggressive pharmacologic lowering of circulating lipid levels.

Lipids for psychiatrists - an overview

Serum cholesterol is a major risk factor for cardiovascular disease. Total cholesterol, LDL cholesterol and triglycerides are positively related to cardiovascular disease, while HDL cholesterol has an inverse relationship. Measurement of lipids is essential in individuals with established cardiovascular disease or type 2 diabetes, and may also be carried out in healthy individuals as part of cardiovascular risk assessment. Lifestyle measures are important in cardiovascular disease prevention, but the mainstay of lipid lowering therapy is appropriate use of lipid lowering drugs. Total and LDL cholesterol are the primary targets for treatment, but consideration should also be given to raising HDL cholesterol and lowering triglycerides where appropriate. Statins are the most frequently used lipid lowering agents, but there is an important place for other drugs, including ezetimibe, fibrates and nicotinic acid.

Safety of high-dose atorvastatin therapy

This article reviews the safety of statins, with emphasis on high-dose atorvastatin (80 mg), the agent with the most efficacy data for clinical outcomes. Although elevated levels of hepatic enzymes were of concern when statins were first introduced, a review of data from large clinical trials shows that elevations in hepatic enzymes are rare and do not lead to clinically significant liver disease. Despite the withdrawal of cerivastatin because of fatal rhabdomyolysis, the risk of this complication with other statins is extremely low. Mild and often transient myalgia is more commonly reported. The safety of high-dose atorvastatin has been evaluated in >11,000 patients, and rates of clinically significant myopathy and elevated hepatic enzymes were extremely low. Simvastatin at doses up to 40 mg is also associated with low rates of elevated hepatic enzymes and myopathy. However, the 80-mg dose of simvastatin carries a risk of myopathy (muscle symptoms and creatine kinase levels >10,000 U/L) of approximately 1 in 250. The clinical benefits of preventing vascular events, myocardial infarction, stroke, and need for revascularization outweigh the low rates of adverse events associated with high-dose statin therapy in high- and intermediate-risk patients.

An ezetimibe-policosanol combination has the potential to be an OTC agent that could dramatically lower LDL cholesterol without side effects

Although many risk factors influence atherogenesis, LDL appears to play a primary role in this process. In prospective epidemiology, coronary risk increases as LDL cholesterol increases, throughout the entire range of concentrations encountered in healthy humans. Coronary risk is minimal in individuals and populations whose serum cholesterol remains quite low throughout life. Thus, practical strategies for achieving large reductions of LDL cholesterol in the general population could have a dramatic impact on coronary mortality rates. Dietary measures have limited potential in this regard; modest restriction of saturated fat has a rather trivial effect on LDL cholesterol, and the very-low-fat quasi-vegan diets that do have a notable effect in this regard currently have little appeal to the majority of the population. With respect to pharmacotherapy, most available hypolipidemic agents with reasonably potent activity entail side effects or compliance difficulties that would render their use too expensive or impractical for population-wide application. However, two agents may have great potential in this regard: policosanol and ezetimibe. The former, a mixture of long-chain alcohols derived from sugar cane wax, has effects on serum lipids comparable to those of statins, and may work by down-regulating expression of HMG-CoA reductase. However, unlike statins, policosanol appears to be devoid of side effects or risks. Ezetimibe is a newly approved drug that is a potent and highly specific inhibitor of an intestinal sterol permease; in daily doses as low as 10 mg, it suppresses intestinal absorption of cholesterol and decreases serum LDL cholesterol by approximately 18%. No side effects have been seen in clinical doses, and the fact that its hypolipidemic activity is additive to that of statins has generated considerable interest. Both policosanol and ezetimibe can be administered once daily. Future studies should determine whether policosanol, like statins, interacts additively with ezetimibe. If so, it may be feasible someday to produce a tablet combining policosanol and ezetimibe that could reduce LDL cholesterol by about 40%, without side effects, and that could be recommended to virtually anyone whose LDL cholesterol levels were not already ideal.

Thematic review series: brain Lipids. Cholesterol metabolism in the central nervous system during early development and in the mature animal

Unesterified cholesterol is an essential structural component of the plasma membrane of every cell. During evolution, this membrane came to play an additional, highly specialized role in the central nervous system (CNS) as the major architectural component of compact myelin. As a consequence, in the human the mean concentration of unesterified cholesterol in the CNS is higher than in any other tissue (approximately 23 mg/g). Furthermore, even though the CNS accounts for only 2.1% of body weight, it contains 23% of the sterol present in the whole body pool. In all animals, most growth and differentiation of the CNS occurs in the first few weeks or years after birth, and the cholesterol required for this growth apparently comes exclusively from de novo synthesis. Currently, there is no evidence for the net transfer of sterol from the blood into the brain or spinal cord. In adults, the rate of synthesis exceeds the need for new structural sterol, so that net movement of cholesterol out of the CNS must take place. At least two pathways are used for this excretory process, one of which involves the formation of 24(S)-hydroxycholesterol. Whether or not changes in the plasma cholesterol concentration alter sterol metabolism in the CNS or whether such changes affect cognitive function in the brain or the incidence of dementia remain uncertain at this time.

Relationship Between Plasma Lipids and All-Cause Mortality in Nondemented Elderly

OBJECTIVES

To investigate the relationship between plasma lipids and risk of death from all causes in nondemented elderly.

DESIGN

Prospective cohort study.

SETTING

Community-based sample of Medicare recipients, aged 65 years and older, residing in northern Manhattan.

PARTICIPANTS

Two thousand two hundred seventy-seven nondemented elderly, aged 65 to 98; 672 (29.5%) white/non-Hispanic, 699 (30.7%) black/non-Hispanic, 876 (38.5%) Hispanic, and 30 (1.3%) other.

MEASUREMENTS

Anthropometric measures: fasting plasma total cholesterol, triglyceride, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and non-HDL-C, body mass index, and apolipoprotein E (APOE) genotype. clinical measures: neuropsychological, neurological, medical, and functional assessments; medical history of diabetes mellitus, heart disease, hypertension, stroke, and treatment with lipid-lowering drugs. Vital status measure: National Death Index date of death. Survival methods were used to examine the relationship between plasma lipids and subsequent mortality in younger and older nondemented elderly, adjusting for potential confounders.

RESULTS

Nondemented elderly with levels of total cholesterol, non-HDL-C, and LDL-C in the lowest quartile were approximately twice as likely to die as those in the highest quartile (rate ratio (RR)=1.8, 95% confidence interval (CI)=1.3-2.4). These results did not vary when analyses were adjusted for body mass index, APOE genotype, diabetes mellitus, heart disease, hypertension, stroke, diagnosis of cancer, current smoking status, or demographic variables. The association between lipid levels and risk of death was attenuated when subjects with less than 1 year of follow-up were excluded (RR=1.4, 95% CI=1.0-2.1). The relationship between total cholesterol, non-HDL-C, HDL-C, and triglycerides and risk of death did not differ for older (>or=75) and younger participants (>75), whereas the relationship between LDL-C and risk of death was stronger in younger than older participants (RR=2.4, 95% CI=1.2-4.9 vs RR=1.6, 95% CI=1.02-2.6, respectively). Overall, women had higher mean lipid levels than men and lower mortality risk, but the risk of death was comparable for men and women with comparable low lipid levels.

CONCLUSION

Low cholesterol level is a robust predictor of mortality in the nondemented elderly and may be a surrogate of frailty or subclinical disease. More research is needed to understand these associations.

Total cholesterol and mortality in the elderly

OBJECTIVE

To evaluate, at a population level, whether total cholesterol (TC) is a risk factor of mortality. To verify whether or not this is true for both genders.

DESIGN

Population-based, long-lasting, prospective study.

SETTING

Institutional epidemiology in primary care.

SUBJECTS

A total of 3257 subjects aged 65-95 years, recruited from Italian general population.

INTERVENTION

None.

MAIN OUTCOME MEASURES

Total cholesterol was measured, analysed as a continuous variable and then divided into quintiles and re-analysed. For each quintile, the multivariate relative risk (RR) of mortality adjusted for confounders was calculated in both genders. Stratification of mortality risk by TC quintiles, body mass index and cigarette smoking was also performed in both genders.

RESULTS

Total cholesterol levels directly predicted coronary mortality in men [RR being in the fifth rather than in the first quintile: 2.40 (1.40-4.14)] and any other mortality in women. It also inversely predicted miscellaneous mortality in both genders. This trend was more evident when low cholesterol was associated with malnutrition or smoking.

CONCLUSIONS

High TC remains a strong risk factor for coronary mortality in elderly men. On the other hand, having a very low cholesterol level does not prolong survival in the elderly; on the contrary, low cholesterol predicts neoplastic mortality in women and any other noncardiovascular mortality in both genders.

Low total cholesterol and increased risk of dying: are low levels clinical warning signs in the elderly? Results from the Italian Longitudinal Study on Aging

OBJECTIVES

To analyze the relationship between serum total cholesterol (TC) and all-cause mortality, taking into account various potential confounders.

DESIGN

Population-based prospective cohort study.

SETTING

Older Italians residing in the general community.

PARTICIPANTS

Four thousand five hundred twenty-one men and women aged 65-84.

MEASUREMENTS

Vital status data were available for 1992-95. The hazard ratios of dying for subjects in the second, third, and fourth quartiles compared with the first quartile of TC were computed using Cox proportional hazards, adjusting for lifestyle factors, anthropomorphic and biochemical measures, preexisting medical conditions, and frailty indicators.

RESULTS

Blood samples were obtained from 3,295 (73%) of the participants, of whom 399 died during almost 3 years of follow-up. Low TC was associated with a higher risk of death. Those with TC in the second, third, and fourth quartiles (TC>189 mg/dL or 4.90 mmol/L) had lower hazard ratios (HRs) of death than subjects in the first quartile (0.57, 95% confidence interval (CI) = 0.38-0.87; 0.56, 95% CI = 0.36-0.88; and 0.53, 95% CI = 0.33-0.84, respectively). Few subjects taking lipid-lowering drugs (LLDs) were in the lowest quartile of cholesterol, suggesting that these individuals have low TC values for reasons other than LLD use.

CONCLUSION

Subjects with low TC levels (<189 mg/dL) are at higher risk of dying even when many related factors have been taken into account. Although more data are needed to clarify the association between TC and all-cause mortality in older individuals, physicians may want to regard very low levels of cholesterol as potential warning signs of occult disease or as signals of rapidly declining health.

What cause of mortality can we predict by cholesterol screening in the Japanese general population?

OBJECTIVE

In a population with a markedly lower coronary mortality such as in Japan, the benefit of cholesterol screening may be different from Western populations. We attempted to assess the importance of cholesterol screening in Japan.

DESIGN

A 13.2-year cohort study for cause-specific mortality.

SETTING

Three hundred randomly selected districts throughout Japan in which the National Survey on Circulatory Disorders 1980 was performed.

SUBJECTS

A total of 9216 community dwelling persons aged 30 years and over, with standardized serum cholesterol measurement and without a past history of cardiovascular disease.

RESULTS

There were 1206 deaths, which included 462 deaths due to cardiovascular disease with 79 coronary heart diseases. Hypercholesterolemia (>6.21 mmol L-1) showed a significant positive relation to coronary mortality (relative risk; 2.93, 95% confidence interval; 1.52-5.63) but not to stroke. Although hypocholesterolemia (<4.14 mmol L-1) was significantly associated with an increased risk of liver cancer, noncardiovascular, noncancer disease and all-cause mortality, these associations, except for liver cancer, disappeared after excluding deaths in the first 5 years of the follow-up. The multivariate adjusted attributable risk of hypercholesterolaemia for coronary disease was 0.98 per 1000 person-years, which was threefold higher than that of hypocholesterolemia for liver cancer: 0.32 per 1000 person-years. The attributable risk percentage of hypercholesterolaemia was 66% for coronary heart disease.

CONCLUSION

Similar to Western populations, it is recommended to provide screening for hypercholesterolaemia in Japan, especially for males, although its attributable risk for coronary disease might be small.

Predictors of cardiac and noncardiac mortality among 14,697 patients with coronary heart disease

The decrease in mortality from ischemic heart disease during the last 25 years may partly reflect improvement in diagnosis and treatment of patients with coronary heart disease. These patients, therefore, are experiencing morbidity and mortality due to other causes. The aim of our study was to describe the incidence and causes of cardiac mortality (CM) and noncardiac mortality (NCM) and to identify predictive factors. A cohort of 14,697 patients with coronary heart disease was merged with the Central Population Registry to identify mortality records from 1990 to 1996. Among the 1,839 deaths, 1,055 (57.4%) were cardiac, 626 (34.0%) were noncardiac, and 158 deaths (8.6%) were due to unknown causes as classified in the International Classification of Diseases-Ninth Edition (ICD). The 3 most significant predictors were age for a 10-year increment (odds ratios 1.75 and 2.25 for CM and NCM, respectively), chronic obstructive pulmonary disease (odds ratios 1.67 and 1.71), and current smoking (odds ratios 1.29 and 1.66). A history of cancer was a predictor of NCM, but not of CM, whereas peripheral vascular disease predicted CM but not NCM. As the number of predictive factors increased from none to >or=5, the risk of NCM gradually increased from 1.9% to 15.5%. Similar predictors expose subjects with coronary disease to CM and NCM, but smoking plays a more pronounced role in the prediction of NCM, whereas past myocardial infarction, lower levels of high-density lipoprotein cholesterol, and peripheral vascular disease are mainly associated with CM. Because of the similarity of antecedent predictors, treatment of risk factors among patients with coronary heart disease should prove valuable for the prevention of all-cause mortality.

Does inflammation or undernutrition explain the low cholesterol-mortality association in high-functioning older persons? MacArthur studies of successful aging

OBJECTIVES

To explore the effect of inflammation and undernutrition on the association between hypocholesterolemia and higher overall mortality in high-functioning older persons.

DESIGN

Prospective cohort study.

SETTING

Three U.S. communities.

PARTICIPANTS

A cohort of 870 participants from the MacArthur Studies of Successful Aging.

MEASUREMENTS

Baseline information was obtained for serum levels of cholesterol, C-reactive protein, interleukin-6, and albumin; body mass index; prevalent medical conditions; health behaviors; and medications. Crude and multivariate logistic regression analyses were used to examine the association between serum total cholesterol levels and 7-year all-cause mortality, while adjusting for potential confounders.

RESULTS

In univariate analysis, the risk ratio of low serum total cholesterol level (<169 mg/dL) for 7-year total mortality was 1.90 (95% confidence interval (CI) = 1.18-3.07). The multiple adjusted risk ratios were 1.82 (95% CI = 1.10-3.00) after controlling for markers of inflammation and nutrition and 1.39 (95% CI = 0.80-2.40) after adjustment for additional cardiovascular risk factors. Sex was an important confounding variable that contributed to the observed inverse association between low serum cholesterol and overall mortality in univariate analysis.

CONCLUSIONS

Hypocholesterolemia is not an independent risk factor for increased overall mortality in high-functioning community-dwelling older men and women. The association between low total cholesterol and high mortality observed in crude analysis is mainly confounded by common cardiovascular risk factors, rather than underlying inflammation or undernutrition.

Reduction of serum LDL-C levels: a relationship to clinical benefits

The association between elevated serum cholesterol levels and cardiovascular risk was established several decades ago by studies such as the Framingham study and the Multiple Risk Factor Intervention Trial (MRFIT). Both primary and secondary prevention trials of cholesterol lowering, using HMG-CoA reductase inhibitors, have demonstrated clear benefits for lipid lowering in preventing both cardiovascular morbidity and mortality over a wide spectrum of coronary heart disease (CHD) risk. Even so, risk of events has been reduced by about 30% in these trials, leaving 70% of events occurring even in the presence of substantial cholesterol lowering. It is unknown whether further reduction of serum cholesterol levels will lower risk factors. The relationship between cholesterol lowering and cardiovascular risk, moreover, is not completely defined; it is unclear, at lower cholesterol levels, whether that relationship follows a threshold, a linear, or a curvilinear model. Early studies of low-density lipoprotein-cholesterol (LDL-C) lowering with HMG-CoA reductase inhibitors suggested that non-cardiovascular mortality might be increased at low serum LDL-C levels, however, these concerns have not been supported by subsequent clinical trials. Recent studies have shed further light on the potential benefits of lowering serum cholesterol levels beyond current guideline targets with HMG-CoA reductase inhibitors. More potent agents in development are likely to make such levels more readily achievable, as well as making guideline targets attainable for many of the large number of patients who currently fail to reach them.

Removing confounders from the relationship between mortality risk and systolic blood pressure at low and moderately increased systolic blood pressure

OBJECTIVE

To assess the relationship between mortality risk and systolic blood pressure (SBP) at low and moderately increased SBP (less than the 70th percentile) before and after correcting for the regression-dilution bias and J-curve effects.

DESIGN

Cohort study.

SETTING

The First National Health and Nutrition Examination Survey Epidemiologic Follow-Up Study.

PARTICIPANTS

The 6839 individuals who participated in the 1982-1984 survey for whom there were no missing data (age range 34-87 years).

MAIN OUTCOME MEASURE

Cardiovascular disease mortality (n = 678) during a 9-year follow-up.

METHODS

Corrections were made for the regression-dilution bias by using average SBP during the decade before baseline as the mortality predictor, and for J-curve effects by excluding individuals who exhibited high age-stratified mortality rates and a decrease in SBP. Cox's regression was used to analyse the follow-up relationship between mortality risk and SBP.

RESULTS

The corrected relative cardiovascular disease mortality risk was 1.23 (95% confidence interval (CI), 1.16 to 1.31) for a 10 mmHg increase in SBP. The relationship was monotonically positive starting at the lowest SBP category in the analysis (< 115 mmHg), and robustly so above about the 32nd percentile (120 mmHg). The equivalent uncorrected result was 1.08 (95% CI, 1.05 to 1.13), and the relationship was J-shaped and became positive above about the 68th percentile (135 mmHg). Below the 70th percentile of SBP, individuals in the corrected analysis were 89% of all individuals.

CONCLUSION

These two corrections transformed the relationship between mortality risk and SBP at low and moderately increased SBP from no association to a robustly positive association starting at 120 mmHg, for the majority of individuals.

Hypothesis - the J-shaped follow-up relation between mortality risk and disease risk-factor is due to statistical confounding

There is currently conflicting evidence from longitudinal follow-up studies concerning the relation between mortality risk and disease risk factor at low levels or the risk factor. This applies to risk factors such as blood pressure, cholesterol, and body-mass index. In some studies, this relation was found to be positive. In others it was negative. This is an issue of importance to clinical and public-health policy, because a negative relation between mortality risk and blood pressure, for instance, implies that anithypertensive medication which lowers blood pressure below a critical threshold could be dangerous. It seemed likely that the conflict could be due to statistical confounding that artifactually elevates mortality risk at low risk-factor levels in survival analyses of longitudinal data. The present paper describes a crude analysis using data from the Framingham Offspring Study to test the idea that such statistical confounding could be caused by the decrease in risk factor with age among subjects near the end of the lifespan (referred to as late-life subjects). The analysis yielded evidence supporting this idea. on the basis of the findings it is hypothesized that: (1). the decrease in risk factor with age during late life causes the late-life bias. This bias distorts a positive relation between mortality risk and risk factor to appear U- or J-shaped in mixed-age adult follow-up cohorts; and (2). removal of the late-life and reverse-causation biases will show that this relation is monotonically positive.

The value of serum albumin and high-density lipoprotein cholesterol in defining mortality risk in older persons with low serum cholesterol

OBJECTIVES

To investigate the relationship between low cholesterol and mortality in older persons to identify, using information collected at a single point in time, subgroups of persons with low and high mortality risk.

DESIGN

Prospective cohort study with a median follow-up period of 4.9 years.

SETTINGS

East Boston, Massachusetts; New Haven, Connecticut; and Iowa and Washington counties, Iowa.

PARTICIPANTS

Four thousand one hundred twenty-eight participants (64% women) age 70 and older at baseline (mean 78.7 years, range 70-103); 393 (9.5%) had low cholesterol, defined as < or =160 mg/dl.

MEASUREMENTS

All-cause mortality and mortality not related to coronary heart disease and ischemic stroke.

RESULTS

During the follow-up period there were 1,117 deaths. After adjustment for age and gender, persons with low cholesterol had significantly higher mortality than those with normal and high cholesterol. Among subjects with low cholesterol, those with albumin> 38 g/L had a significant risk reduction compared with those with albumin < or =38 g/L (relative risk (RR) = 0.57; 95% confidence interval (CI) = 0.41-0.79). Within the higher albumin group, high-density lipoprotein cholesterol (HDL-C) level further identified two subgroups of subjects with different risks; participants with HDL-C <47 mg/dl had a 32% risk reduction (RR = 0.68; 95% CI = 0.47-0.99) and those with HDL-C > or =47 mg/dl had a 62% risk reduction (RR = 0.38; 95% CI = 0.20-0.68), compared with the reference category; those with albumin < or =38 g/L and HDL-C <47 mg/dl.

CONCLUSIONS

Older persons with low cholesterol constitute a heterogeneous group with regard to health characteristics and mortality risk. Serum albumin and HDL-C can be routinely used in older patients with low cholesterol to distinguish three subgroups with different prognoses: (1) high risk (low albumin), (2) intermediate risk (high albumin and low HDL-C), and (3) low risk (high albumin and high HDL-C).

Cholesterol and all-cause mortality in elderly people from the Honolulu Heart Program: a cohort study

BACKGROUND

A generally held belief is that cholesterol concentrations should be kept low to lessen the risk of cardiovascular disease. However, studies of the relation between serum cholesterol and all-cause mortality in elderly people have shown contrasting results. To investigate these discrepancies, we did a longitudinal assessment of changes in both lipid and serum cholesterol concentrations over 20 years, and compared them with mortality.

METHODS

Lipid and serum cholesterol concentrations were measured in 3572 Japanese/American men (aged 71-93 years) as part of the Honolulu Heart Program. We compared changes in these concentrations over 20 years with all-cause mortality using three different Cox proportional hazards models.

FINDINGS

Mean cholesterol fell significantly with increasing age. Age-adjusted mortality rates were 68.3, 48.9, 41.1, and 43.3 for the first to fourth quartiles of cholesterol concentrations, respectively. Relative risks for mortality were 0.72 (95% CI 0.60-0.87), 0.60 (0.49-0.74), and 0.65 (0.53-0.80), in the second, third, and fourth quartiles, respectively, with quartile 1 as reference. A Cox proportional hazard model assessed changes in cholesterol concentrations between examinations three and four. Only the group with low cholesterol concentration at both examinations had a significant association with mortality (risk ratio 1.64, 95% CI 1.13-2.36).

INTERPRETATION

We have been unable to explain our results. These data cast doubt on the scientific justification for lowering cholesterol to very low concentrations (<4.65 mmol/L) in elderly people.

Recombinant lipoproteins: lipoprotein-like lipid particles for drug targeting

Lipoproteins are endogenous particles that transport lipids through the blood to various cell types, where they are recognised and taken up via specific receptors. These particles are, therefore, excellent candidates for the targeted delivery of drugs to various tissues. For example, the remnant receptor and the asialoglycoprotein receptor (ASGPr), which are uniquely localised on hepatocytes, recognise chylomicrons and lactosylated high density lipopoteins (HDL), respectively. In addition, tumour cells of various origins overexpress the low density lipoprotein (LDL) receptor that recognises apolipoprotein E (apoE) on small triglyceride-rich particles and apoB-100 on LDL. Being endogenous, lipoproteins are biodegradable, do not trigger immune reactions, and are not recognised by the reticuloendothelial system (RES). However, their endogenous nature also hampers large-scale pharmaceutical application. In the past two decades, various research groups have successfully synthesised recombinant lipoproteins from commercially available natural and synthetic lipids and serum-derived or recombinant apolipoproteins, which closely mimic the metabolic behaviour of their native counterparts in animal models as well as humans. In this paper, we will summarise the studies that led to the development of these recombinant lipoproteins, and we will address the possibility of using these lipidic particles to selectively deliver a wide range of lipophilic, amphiphilic, and polyanionic compounds to hepatocytes and tumour cells. In addition, the intrinsic therapeutic activities of recombinant chylomicrons and HDL in sepsis and atherosclerosis will be discussed.

Comparative tolerability of the HMG-CoA reductase inhibitors

The availability of the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors has revolutionised the treatment of lipid abnormalities in patients at risk for the development of coronary atherosclerosis. The relatively widespread experience with HMG-CoA therapy has allowed a clear picture to emerge concerning the relative tolerability of these agents. While HMG-CoA reductase inhibitors have been shown to decrease complications from atherosclerosis and to improve total mortality, concern has been raised as to the long term safety of these agents. They came under close scrutiny in early trials because ocular complications had been seen with older inhibitors of cholesterol synthesis. However, extensive evaluation demonstrated no significant adverse alteration of ophthalmological function by the HMG-CoA reductase inhibitors. Extensive experience with the potential adverse effect of the HMG-CoA reductase inhibitors on hepatic function has accumulated. The effect on hepatic function for the various HMG-CoA reductase inhibitors is roughly dose-related and 1 to 3% of patients experience an increase in hepatic enzyme levels. The majority of liver abnormalities occur within the first 3 months of therapy and require monitoring. Rhabdomyolysis is an uncommon syndrome and occurs in approximately 0.1% of patients who receive HMG-CoA reductase inhibitor monotherapy. However, the incidence is increased when HMG-CoA reductase inhibitors are used in combination with agents that share a common metabolic path. The role of the cytochrome P450 (CYP) enzyme system in drug-drug interactions involving HMG-CoA reductase inhibitors has been extensively studied. Atorvastatin, cerivastatin, lovastatin and simvastatin are predominantly metabolised by the CYP3A4 isozyme. Fluvastatin has several metabolic pathways which involve the CYP enzyme system. Pravastatin is not significantly metabolised by this enzyme and thus has theoretical advantage in combination therapy. The major interactions with HMG-CoA reductase inhibitors in combination therapy involving rhabdomyolysis include fibric acid derivatives, erythromycin, cyclosporin and fluconazole. Additional concern has been raised relative to overzealous lowering of cholesterol which could occur due to the potency of therapy with these agents. Currently, there is no evidence from clinical trials of an increase in cardiovascular or total mortality associated with potent low density lipoprotein reduction. However, a threshold effect had been inferred by retrospective analysis of the Cholesterol and Recurrent Events study utilising pravastatin and the role of aggressive lipid therapy is currently being addressed in several large scale trials.

[The risk of colorectal adenomatous polyp in relation to serum total cholesterol levels in Japanese men classified by age group]

In order to investigate the relationship between the risk of colorectal cancer and serum total cholesterol (TC) levels, we studied the relationship between the risk of colorectal adenomatous polyp and high TC levels in Japanese men aged from 40 to 59 at a manufacturing company. We first diagnosed 283 subjects as having adenomatous polyp (AD) or normal (C), identified by means of an immunological fecal occult blood detection test and total colonofiberscopic examination (TCF), and then selected 94 subjects after excluding the patients with diseases possibly influencing TC. We classified the subjects into two age groups (40-49 and 50-59) and conducted a statistical analysis of AD and C groups by means of a two tailed t-test. The mean values for TC (DTC), which had been obtained within 3 months before TCF, were significantly different (p < 0.001 95% CI 15.79-48.49) for those in their 40s, but were not different for those in their 50s. In order to check the stability of the data, we analyzed the mean values for DTC and BTC, which had been obtained within 15 months. The results showed the same trend for those in their 40s (p = 0.001 95% CI 10.76-40.87). The mean DTC and BTC values were again not significantly different for those in their 50s. We further divided the subjects into the lower (-181 mg/dl) and higher (209 mg/dl-) DTC values and conducted further statistical analysis with Fisher's exact test. The results were significant in the 40-49 age group (p = 0.004), in the odds ratio (13.75 95% CI 2.32-81.49), but showed no significant difference in the 50-59 age group. The mean LDL-cholesterol values within 3 months before TCF were significantly different in the 40-49 age group (p < 0.001 95% CI 15.22-47.70) and were not different in the 50-59 age group. There was no statistical difference in the mean values for HDL-cholesterol, triglyceride and body mass index in either age group. From these results, it can be concluded that the risk of colorectal adenomatous polyp was associated with a higher serum total cholesterol level in the 40s, and seemed to indicate a close relationship with the risk of colorectal cancer.

Association of low plasma cholesterol with mortality for cancer at various sites in men: 17-y follow-up of the prospective Basel study

BACKGROUND

Low serum cholesterol has been associated with an increased risk of cancer mortality in various studies, which has led to uncertainty regarding the benefit of lower blood cholesterol.

OBJECTIVE

The aim of our study was to evaluate the association between low blood cholesterol (<5.16 mmol/L) and cancer at sites that have rarely been evaluated. We placed special emphasis on the potential confounding effect of antioxidant vitamins.

DESIGN

Plasma concentrations of cholesterol and antioxidant vitamins were measured in 1971-1973 in 2974 men working in Basel, Switzerland. In 1990, the vital status of all participants was assessed.

RESULTS

Two hundred ninety of the participants had died from cancer, 87 from lung, 30 from prostate, 28 from stomach, and 22 from colon cancer. Group means for plasma cholesterol concentrations did not differ significantly between survivors and those who died from cancer at any of the studied sites. With plasma cholesterol, vitamins C and E, retinol, carotene, smoking, and age accounted for in a Cox model, an increase in total cancer mortality in lung, prostate, and colon but not in stomach cancer mortality was observed in men >60 y of age with low plasma cholesterol. When data from the first 2 y of follow-up were excluded from the analysis, the relative risk estimates remained practically unchanged with regard to lung cancer but decreased for colon, prostate, and overall cancer.

CONCLUSIONS

Increased cancer mortality risks associated with low plasma cholesterol were not explained by the confounding effect of antioxidant vitamins, but were attributed in part to the effect of preexisting cancer.

Vegan proteins may reduce risk of cancer, obesity, and cardiovascular disease by promoting increased glucagon activity

Amino acids modulate the secretion of both insulin and glucagon; the composition of dietary protein therefore has the potential to influence the balance of glucagon and insulin activity. Soy protein, as well as many other vegan proteins, are higher in non-essential amino acids than most animal-derived food proteins, and as a result should preferentially favor glucagon production. Acting on hepatocytes, glucagon promotes (and insulin inhibits) cAMP-dependent mechanisms that down-regulate lipogenic enzymes and cholesterol synthesis, while up-regulating hepatic LDL receptors and production of the IGF-I antagonist IGFBP-1. The insulin-sensitizing properties of many vegan diets--high in fiber, low in saturated fat--should amplify these effects by down-regulating insulin secretion. Additionally, the relatively low essential amino acid content of some vegan diets may decrease hepatic IGF-I synthesis. Thus, diets featuring vegan proteins can be expected to lower elevated serum lipid levels, promote weight loss, and decrease circulating IGF-I activity. The latter effect should impede cancer induction (as is seen in animal studies with soy protein), lessen neutrophil-mediated inflammatory damage, and slow growth and maturation in children. In fact, vegans tend to have low serum lipids, lean physiques, shorter stature, later puberty, and decreased risk for certain prominent 'Western' cancers; a vegan diet has documented clinical efficacy in rheumatoid arthritis. Low-fat vegan diets may be especially protective in regard to cancers linked to insulin resistance--namely, breast and colon cancer--as well as prostate cancer; conversely, the high IGF-I activity associated with heavy ingestion of animal products may be largely responsible for the epidemic of 'Western' cancers in wealthy societies. Increased phytochemical intake is also likely to contribute to the reduction of cancer risk in vegans. Regression of coronary stenoses has been documented during low-fat vegan diets coupled with exercise training; such regimens also tend to markedly improve diabetic control and lower elevated blood pressure. Risk of many other degenerative disorders may be decreased in vegans, although reduced growth factor activity may be responsible for an increased risk of hemorrhagic stroke. By altering the glucagon/insulin balance, it is conceivable that supplemental intakes of key non-essential amino acids could enable omnivores to enjoy some of the health advantages of a vegan diet. An unnecessarily high intake of essential amino acids--either in the absolute sense or relative to total dietary protein--may prove to be as grave a risk factor for 'Western' degenerative diseases as is excessive fat intake.

New concepts and paradigms in cardiovascular medicine: the noninvasive management of coronary artery disease

Coronary atherosclerosis is a diffuse heterogeneous process that occurs throughout the length of epicardial coronary arteries. Myocardial infarction and unstable coronary syndromes are caused most commonly by plaque rupture of lipid rich, less severe coronary artery stenoses. Vigorous cholesterol lowering by low fat food and lipid active drugs, control of hypertension, and smoking abstinence stabilize plaque and markedly reduce coronary events and angina pectoris with greater improvement in survival than reported for elective invasive revascularization procedures. The term "regression" or "reversal" of coronary artery disease (CAD) as used clinically incorporates the spectrum of beneficial changes in plaque composition and pathology, modest improvement in anatomic severity, endothelial healing, increased coronary flow and flow capacity, decreased symptoms, and improved survival. Standard coronary arteriography and standard noninvasive diagnostic tests (as commonly used) are inadequate for identifying or assessing severity of diffuse CAD. Newer technology or approaches using noninvasive positron emission tomography (PET), invasive intravascular ultrasound or pressure or flow velocity guide wires provide important new insights into the presence and severity of both segmental and diffuse CAD. Revascularization procedures may be beneficial in selected, restricted circumstances, primarily for 3-vessel disease and reduced left ventricular function and for "hibernating" or "stunned" myocardium. However, the benefits of revascularization procedures on survival in patients with good left ventricular function have not been convincingly documented, with substantive evidence that adverse outcomes outweigh the potential benefits. This collective new knowledge provides the basis for a shift in the management of CAD from an invasive, procedure-oriented viewpoint currently dominant in cardiology toward a noninvasive orientation that views the problem as a graded, continuous, heterogeneously diffuse disease process for which reversal treatment is optimal. Noninvasive management of CAD based on reversal treatment is a valid, safe, effective primary step, but it requires patient and physician knowledge. CAD should be treated immediately at the time of a firm diagnosis by simultaneous, vigorous risk factor management, low fat diet and a statin class drug. For control of high-density lipoprotein and triglycerides, other lipid active drugs should be added or substituted for statins if side effects prevent their use. Low fat food and weight control by appropriate caloric carbohydrate restriction are essential for reducing the highly atherogenic postprandial lipid surge that is not affected by statins. This vigorous reversal treatment, with aggressive anti-anginal and anti-platelet management as needed, should be used in every patient with diagnosed CAD before elective revascularization procedures are considered. In the author's experience, the majority of patients will pursue an effective reversal regimen when it is presented and managed appropriately with strong support by a knowledgeable participating physician providing sustained, intense guidance and pharmacologic control. For the minority of patients not responding to vigorous medical treatment or demonstrating progression, coronary arteriography and revascularization procedures are then appropriate.

Diazepam binding inhibitor and total cholesterol plasma levels in cirrhosis and hepatocellular carcinoma

Cholesterol is used by cells for biosynthetic processes and for steroid synthesis. Although the role of cholesterol in tumorigenesis is not clear it is known that steroids are important factors in human carcinogenesis. A polypeptide, diazepam binding inhibitor (DBI), which is an endogenous ligand for peripheral benzodiazepine receptors enhances steroidigenesis by promoting cholesterol delivery to the inner mitochondrial membrane which represents the rate-limiting step of steroid biosynthesis. We have assayed the total cholesterol (TC) and the DBI plasma concentrations in patients with liver cirrhosis complicated by hepatocellular carcinoma (HCC) in comparison with those of uncomplicated liver cirrhosis. TC and DBI levels have been studied in 73 cirrhotic patients and in 23 patients with HCC. Both TC and DBI levels were higher in HCC patients when compared with age, sex and Child-Pugh class matched cirrhotic controls. The values (mean+/-S.D.) in patients in Child-Pugh class B and C with and without HCC were respectively 128+/-30 mg/dl vs. 106+/-27 mg/dl (P < 0.01) and 2.05+/-0.78 pmol/ml vs. 0.78+/-0.84 pmol/ml (P < 0.0001). The data may be the result of the metabolic influence of tumors that enhances steroid biosynthesis during tumor proliferation.

Serum cholesterol levels as a measure of frailty in elderly patients

The authors evaluated the association between serum cholesterol levels and social, clinical, and functional characteristics in 637 elderly hospitalized patients (mean age = 79.1 years, range = 65-97) from the Geriatric Evaluation and Rehabilitation Unit (GERU) at P. Richiedei Hospital in Gussago, Brescia (Italy). Patients consecutively admitted to the GERU during an 18-month period underwent a multidimensional evaluation including information on demographics, cognitive status, physical health (number of chronic diseases and administered drugs), functional disability, and nutritional status. Mean cholesterol levels were significantly lower in men; persons living with others; older individuals; and individuals with cognitive impairment, poorer somatic health, higher disability, and a higher level of malnutrition. Lower serum cholesterol levels may be considered an independent hematologic marker of frailty in elderly hospitalized patients.

[Cholesterolemia and pathology: update]

The relationship between plasma cholesterol levels and disease is more complex than presumed. If the pathogenic role of hypercholesterolemia in ischemic myocardial disease is now undoubted, the deleterious effect of hypocholesterolemia induced by diet or drugs, mainly on cancer mortality and violent death, is still controversial. In a prognostic point of view it seems that the degree of diminution of cholesterol levels is more important than hypocholesterolemia itself. Several hypothesis were formulated; however, hypocholesterolemia does not appear as a causal factor. A prudent approach of hypercholesterolemia remains desirable but without special alterations of the recent recommendations concerning the management of hypercholesterolemia.

The soluble interleukin-2 receptor predicts mortality in older hospitalized men

BACKGROUND

There is an inverse relationship between the soluble interleukin-2 receptor (sIL-2R) and serum albumin, cholesterol, transferrin, prealbumin, and hemoglobin. Inasmuch as low serum albumin and cholesterol have been associated with excess mortality, we hypothesized that elevated sIL-2R would predict mortality in older adults.

OBJECTIVE

To determine if elevated sIL-2R predicts mortality in patients on a geriatric rehabilitation unit.

DESIGN

Prospective cohort.

SETTING

University-affiliated VA medical center.

PARTICIPANTS

Seventy-two male patients aged greater than 60 years admitted to a geriatric rehabilitation unit. Patients with severe hepatic or renal disease were excluded.

MEASUREMENTS

We measured serum albumin, prealbumin, cholesterol, transferrin, hemoglobin, body mass index (BMI), C-reactive protein (CRP), and sIL-2R upon admission. Subjects were followed for 1 year.

RESULTS

Low serum albumin, prealbumin, and hemoglobin and high sIL-2R and CRP predicted 1-year mortality on univariate analysis. When these predictors were included as covariates in a Cox regression model, only sIL-2R was a significant independent predictor of mortality (P = .043). Multiple linear regression with the above covariates revealed that only sIL-2R predicted time to death at (P = .003).

CONCLUSIONS

High sIL-2R and CRP and low albumin, prealbumin, and hemoglobin predicted mortality using univariate analysis on a rehabilitation unit. However, with multivariate analysis, sIL-2R was the sole predictor of mortality.

Human recombinant apolipoprotein E-enriched liposomes can mimic low-density lipoproteins as carriers for the site-specific delivery of antitumor agents

Progressive hypocholesterolemia is a feature associated with a number of cancers of different origin, and it is caused by the high expression of low-density lipoprotein (LDL) receptors (LDLrs) on many tumor cell types. Selective delivery of chemotherapeutics using LDL as a carrier has therefore been proposed, but the endogenous nature of LDL hampers its pharmaceutical application. In the current study, we explored the possibility of synthesizing liposomes that mimic LDL from commercially available lipids and proteins. Small unilamellar liposomes were created (28.9 +/- 0.9 nm) and complexed with 5.8 +/- 0.7 molecules of human recombinant apolipoprotein E (apoE). On intravenous injection into rats, the liposomes retained their aqueous core, structural integrity, and the majority of the preassociated apoE. [3H]Cholesteryl oleate-labeled apoE-enriched liposomes showed a relatively long serum half-life (>5 hr), and a low uptake by cells of the reticuloendothelial system was observed (<0.8% of the injected dose at 30 min after injection). Pretreatment of rats with 17alpha-ethinyl estradiol, which induces the expression of the LDLr on the liver and adrenals, led to a 2.5-fold accelerated serum clearance (t1/2 = 123 +/- 10 min) and a selectively increased uptake of liposomes by the liver (2.0-fold) and adrenals (3.8-fold). The liver association of the liposomes was coupled to the lysosomal uptake route, similarly as for LDL. In vitro studies using B16 melanoma cells showed that the liposomes bound exclusively to the LDLr via their apoE moiety (90,000 liposomes/cell), with a 14-fold higher affinity (Kd = 0.77 +/- 0.09 nM) than LDL itself. Because of their favorable properties, we anticipate that these apoE-enriched liposomes are advantageous compared with native LDL in the development of a selective LDLr-targeted antitumor therapy.

Cross-sectional and longitudinal changes in total and high-density-lipoprotein cholesterol levels over a 20-year period in elderly men: the Honolulu Heart Program

PURPOSE

The purpose of this report is to describe levels of total cholesterol and high-density-lipoprotein cholesterol (HDL-C) in a group of elderly men and to compare these levels to those that were observed 20 years earlier.

METHODS

From 1965-1968, the Honolulu Heart Program began following 8006 men of Japanese ancestry living on the island of Oahu, Hawaii, in a prospective study of coronary heart disease and stroke. This report presents data for 971 men who participated in a separate fasting study of lipids and lipoproteins that first occurred from 1970-1972 and in those who received repeat examinations 10 and 20 years later. Men were aged 71-93 years at the last examination.

RESULTS

Over the 20-year period, total cholesterol declined by 1.6-1.8 mg/dL per year (P < 0.001), from average baseline values of 219-222 mg/dL. Levels of HDL-C rose 0.2-0.3 mg/dL per year (P < 0.001), from average baseline values of 44-46 mg/dL. After adjustment for baseline cholesterol levels, men with prevalent coronary heart disease at the end of the 20-year follow-up experienced significantly greater reductions in total cholesterol levels than men without disease (P < 0.001). Men who developed coronary heart disease within the first 10 years of follow-up had the greatest yearly decline in total cholesterol (1.9 mg/dL), followed by men who developed heart disease later (1.8 mg/dL) and men who remained disease free (1.5 mg/dL). Differences between men with recent and earlier disease were not statistically significant, although men without coronary disease experienced a significantly smaller decrease in total cholesterol than either of these groups (P < 0.05).

CONCLUSIONS

Changes in total cholesterol and HDL-C levels with advancing age may be part of a natural aging process. Some changes, however, such as large reductions in total cholesterol, may signal occult disease or declines in overall health. Selective survival may contribute to these findings since improvements in lipid and lipoprotein levels that are beneficial in younger ages were common in this long-lived cohort of men.

Epidemiology of low total plasma cholesterol concentration among young adults: the CARDIA study. Coronary Artery Risk Development in Young Adults

BACKGROUND

Data on stability of plasma total cholesterol levels and its determinants among young adults are lacking. Knowledge of factors associated with low levels of plasma total cholesterol during young adulthood may help clarify the nature of associations between hypocholesterolemia and health or illness.

METHODS

Tracking of plasma total cholesterol was investigated using data from the baseline (1985-1986), Year 5 (1990-1991), and Year 7 (1992-1993) examinations of the Coronary Artery Risk Development in Young Adults Study. Lifestyle (including dietary), physiological, medical, and psychological correlates of plasma total cholesterol were examined cross-sectionally at baseline using ANCOVA and multivariate logistic regression. The attributes of participants with persistently low plasma total cholesterol level after 7 years (i.e., remaining below the 10th percentile of sex- and race-specific distributions) were also examined.

RESULTS

The cohort in this analysis comprised 720 black men, 922 white men, 899 black women, and 944 white women who were between the ages of 18 and 30 years at baseline. Between 44 and 52% of those with plasma total cholesterol levels below the 10th percentile remained below the same percentile 7 years later. Among black men, a difference of 1 SD in age [3.7 years; odds ratio (OR) = 0.69; 95% CI = 0.52-0.91] and a difference of 1 SD in systolic blood pressure (10.5 mm Hg; OR = 0.73; 95% CI = 0.54-0.97) were independently associated with lower odds, respectively, of being in the lowest 10th percentile of the plasma total cholesterol distribution. Also among black men, current smoking and more calories from carbohydrates were associated with nonsignificantly higher odds of low total cholesterol level. Among white men, a 1 SD older age (3.4 years; OR = 0.78; 95% CI = 0.61-1.00) and a 1 SD higher physical fitness (118 sec; OR = 1.41; 95% CI = 1.09-1.82) predicted lower and higher odds, respectively, of low plasma total cholesterol. Among black women, a 1 SD difference in albumin (0.3 g/dL; OR = 0.80; 95% CI = 0.63-1.03) was related to lower odds of low plasma total cholesterol. Among white women, the factors independently associated with low plasma total cholesterol were body mass index (OR for a difference in 4.0 kg/m2 = 0.73; 95% CI = 0.54-1.00) and gamma-glutamyl transferase (OR for an increase in 9.6 IU/L = 0.41; 95% CI = 0.18-0.93). The independent predictive factors of stably low total cholesterol levels were age and uric acid among black men (both inversely related) and age, Framingham Type A Behavior (inversely), and calories from carbohydrates (positively related) among white men.

CONCLUSION

Young adults with low plasma total cholesterol level have characteristics generally associated with good cardiovascular health. However, adverse attributes such as current cigarette smoking (notably among black men) may confound future associations between low total cholesterol and disease.

Randomised placebo controlled trial of effect on mood of lowering cholesterol concentration. Oxford Cholesterol Study Group

OBJECTIVE

To evaluate the effects on mood of a substantial and prolonged reduction in total cholesterol concentration.

DESIGN

Randomised placebo controlled comparison of patients who had been allocated to receive simvastatin 20 mg or 40 mg daily versus those allocated matching placebo in a ratio of 2:1. Follow up at an average of 152 weeks after randomisation.

SUBJECTS

Men and women aged between 40 and 75 years at entry with blood total cholesterol of 3.5 mmol/l or greater, who were considered to be at higher than average risk of coronary heart disease based on medical history.

MAIN OUTCOME MEASURES

The shortened profile of mood states questionnaire, reported use of psychotropic medication, and symptoms possibly related to mood.

RESULTS

Simvastatin reduced total cholesterol by 1.9 mmol/l (26.7%) at the time of follow up. Among all 621 patients randomised to simvastatin (414 patients) or placebo (207 patients) there were no significant differences in the use of psychotropic medication or in reports of symptoms possibly related to mood. Of these patients, 491 (334 simvastatin, 157 placebo) completed the mood questionnaire, and there were no significant differences between the treatment groups in total or subscale scores, even when patients with low baseline cholesterol concentrations or elderly subjects were considered separately.

CONCLUSION

These results do not support the hypothesis that treatment to lower cholesterol concentration causes mood disturbance.