LDL particle size in subjects with previously unsuspected coronary heart disease: relationship with other cardiovascular risk markers

Bariatric surgery, through beneficial effects on underlying mechanisms, improves cardiorenal and liver metabolic risk over an average of ten years of observation: A longitudinal and a case-control study

BACKGROUND

Bariatric surgery has long-term beneficial effects on body weight and metabolic status, but there is an apparent lack of comprehensive cardiometabolic, renal, liver, and metabolomic/lipidomic panels, whereas the underlying mechanisms driving the observed postoperative ameliorations are still poorly investigated. We aimed to study the long-term effects of bariatric surgery on metabolic profile, cardiorenal and liver outcomes in association with underlying postoperative gut hormone adaptations.

METHODS

28 individuals who underwent bariatric surgery [17 sleeve gastrectomy (SG), 11 Roux-en-Y gastric bypass (RYGB)] were followed up 3, 6 and 12 and at 10 years following surgery. Participants at 10 years were cross-sectionally compared with an age-, sex- and adiposity-matched group of non-operated individuals (n = 9) and an age-matched pilot group of normal-weight individuals (n = 4).

RESULTS

There were durable effects of surgery on body weight and composition, with an increase of lean mass percentage persisting despite some weight regain 10 years postoperatively. The improvements in metabolic and lipoprotein profiles, cardiometabolic risk markers, echocardiographic and cardiorenal outcomes persisted over the ten-year observation period. The robust improvements in insulin resistance, adipokines, activin/follistatin components and postprandial gastrointestinal peptide levels persisted 10 years postoperatively. These effects were largely independent of surgery type, except for a lasting reduction of ghrelin in the SG subgroup, and more pronounced increases in proglucagon products, mainly glicentin and oxyntomodulin, and in the cardiovascular risk marker Trimethylamine-N-oxide (TMAO) within the RYGB subgroup. Despite similar demographic and clinical features, participants 10 years after surgery showed a more favorable metabolic profile compared with the control group, in conjunction with a dramatic increase of postprandial proglucagon product secretion.

CONCLUSIONS

We demonstrate that cardiorenal and metabolic benefits of bariatric surgery remain robust and largely unchanged ten years postoperatively and are associated with durable effects on gastrointestinal- muscle- and adipose tissue-secreted hormones.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT04170010.

Association of low-density lipoprotein pattern with mortality after myocardial infarction: Insights from the TRIUMPH study

BACKGROUND

Studies of incident coronary heart disease risk within low-density lipoprotein (LDL) subclass (small, dense vs large, buoyant) have shown mixed results. No prospective cohort study has examined the association of small, dense, or large, buoyant LDL with mortality after myocardial infarction (MI).

OBJECTIVE

The objective of the study was to examine association of LDL pattern after MI and death.

METHODS

In 2476 patients hospitalized for MI, LDL pattern (A [large, buoyant], A/B [mixed], and B [small, dense]) was established by ultracentrifugation using Vertical Auto Profile. Using time-to-event analysis, we examined the association with 5-year mortality within LDL patterns, after adjusting for important patient and treatment characteristics. We additionally adjusted for LDL cholesterol (LDL-C) and triglyceride levels and used directly measured LDL-C and non-high-density lipoprotein cholesterol as exposures.

RESULTS

Patterns A, A/B, and B were present in 39%, 28%, and 33% of patients, respectively, with incident rates (per 1000 patient-years) of 50, 34, and 24 for all-cause and 24, 19, and 10 for CV mortality. The hazard ratios (95% confidence interval) with LDL patterns A/B and B compared with pattern A were 0.77 (0.61, 0.99) and 0.67 (0.51, 0.88) for all-cause, 0.94 (0.67, 1.33) and 0.69 (0.46, 1.03) for cardiovascular, and 0.64 (0.45, 0.91) and 0.65 (0.45, 0.93) for noncardiovascular mortalities, respectively. Results were similar when further adjusted for LDL-C and triglycerides, or with LDL-C and non-high-density lipoprotein cholesterol as exposures.

CONCLUSION

Compared with LDL pattern A, pattern B was significantly associated with reduced all-cause and non-CV mortalities with a trend for lower CV mortality after MI, independent of LDL-C and triglycerides.

Low-density lipoprotein size and cardiovascular risk assessment

A predominance of small, dense low-density lipoproteins (LDL) has been accepted as an emerging cardiovascular risk factor by the National Cholesterol Education Program Adult Treatment Panel III. LDL size seems to be an important predictor of cardiovascular events and progression of coronary heart disease and evidences suggests that both quality (particularly small, dense LDL) and quantity may increase cardiovascular risk. However, other authors have suggested that LDL size measurement does not add information beyond that obtained by measuring LDL concentration, triglyceride levels and HDL concentrations. Therefore, it remains debatable whether to measure LDL particle size in cardiovascular risk assessment and, if so, in which categories of patient. Therapeutic modulation of LDL particle size or number appears beneficial in reducing the risk of cardiovascular events, but no clear causal relationship has been shown, because of confounding factors, including lipid and non-lipid variables. Studies are needed to investigate the clinical significance of LDL size measurements in patients with coronary and non-coronary forms of atherosclerosis; in particular, to test whether LDL size is associated with even higher vascular risk, and whether LDL size modification may contribute to secondary prevention in such patients.

ACAT2 is a target for treatment of coronary heart disease associated with hypercholesterolemia

The inhibition of intracellular cholesterol esterification as a means to prevent atherosclerosis has been considered to have potential for many years. Two different ACAT enzymes were discovered about 7 years ago, and it has become clear that the two enzymes provide separate physiologic functions. Much has been learned from mice with gene deletions for either ACAT1 or ACAT2. Deletion of ACAT2 has consistently been atheroprotective whereas deletion of ACAT1 has been varyingly problematic. ACAT1 functions in converting cellular cholesterol into cholesteryl ester in response to cholesterol abundance inside the cells. In atherosclerotic lesions, where macrophages ingest excess cholesterol, the ability to esterify the newly-acquired cholesterol seems important for cell survival. Inhibition of ACAT1 may bring undesired consequences with destabilization of cellular membrane function upon cholesterol accumulation leading to macrophage cell death. In contrast, ACAT2 is expressed only in hepatocytes and enterocytes, where ACAT1 is silent, and appears to provide cholesteryl esters for transport in lipoproteins. These two cell types have an abundance of additional mechanisms for disposing of cholesterol so that depletion of ACAT2 does not signal apoptosis. At the present time, the bulk of the available data suggest that the strategy seeming to bear the most potential for treatment of coronary heart disease associated with hypercholesterolemia would be to specifically inhibit ACAT2.

Low-density lipoprotein particle number and risk for cardiovascular disease

The key role played by low-density lipoprotein (LDL) particles in the pathogenesis of coronary heart disease (CHD) is well accepted, as is the benefit of lowering LDL in high-risk patients. What remains controversial is whether we are using the best measure(s) of LDL to identify all individuals who would benefit from therapy. Many studies have shown that, at a given level of LDL cholesterol, individuals with predominantly small LDL particles (pattern B) experience greater CHD risk than those with larger-size LDL. However, it is not clear from this observation that small LDL particles are inherently more atherogenic than large ones because, at a given level of LDL cholesterol, individuals with small LDL have more LDL particles in total. The phenotype of small LDL particle size co-segregates with a cluster of metabolic factors, including elevated triglycerides and reduced HDL cholesterol, and in multivariate analyses has generally been found not to be independently associated with CHD risk. In contrast, LDL particle number measured by nuclear magnetic resonance has consistently been shown to be a strong, independent predictor of CHD.

Association of the APOLIPOPROTEIN A1/C3/A4/A5 Gene Cluster With Triglyceride Levels and LDL Particle Size in Familial Combined Hyperlipidemia

The APOLIPOPROTEIN ( APO ) A1/C3/A4/A5 gene cluster on chromosome 11 has been hypothesized to be a modifier of plasma triglycerides in FCH. In the present study, we extended previous association analyses of the gene cluster to include APOA5 , a newly discovered member of the cluster. Eight SNPs across the APOA1/C3/A4/A5 gene region were analyzed in 78 FCH probands and their normolipidemic spouses as well as in 27 Dutch FCH families. Of the individual SNPs tested in the case-control panel, the strongest evidence of association was obtained with SNPs in APOA1 ( P =0.001) and APOA5 ( P =0.001). A single haplotype defined by a missense mutation in APOA5 was enriched 3-fold in FCH probands when compared with the normolipidemic spouses ( P =0.001) and a second haplotype was significantly enriched in the spouses ( P =0.001). Family-based tests also indicated significant association of triglyceride levels and LDL particle size with the investigated SNPs of APOC3 and APOA5 . These findings suggest that genetic variation in the APOA1/C3/A4/A5 gene cluster acts as a modifier of plasma triglyceride levels and LDL particle size within FCH families and furthermore indicate that a number of haplotypes may contribute to FCH.

High Carbohydrate and High Monounsaturated Fatty Acid Diets Similarly Affect LDL Electrophoretic Characteristics in Men Who Are Losing Weight

We compared the effects of ad libitum consumption of a defined high complex carbohydrate (CHO) diet (% of energy: CHO, 58.3; fat, 25.8) vs. a defined high monounsaturated fatty acid (MUFA) diet (% of energy: CHO, 44.7; fat, 40.1; MUFA, 22.5) on LDL electrophoretic characteristics. Healthy men [n = 65; age, 37.5 +/- 11.2 (mean +/- SD) y; BMI, 29.2 +/- 4.9 kg/m2] were randomly assigned to one of the two diets that they consumed for 6-7 wk. The high CHO diet significantly reduced body weight (-2%). The diet-induced reduction in plasma LDL cholesterol (C) levels in the high-CHO diet group was due mainly to concurrent reductions in the cholesterol content of small (<25.5 nm, P < 0.01) and medium-sized LDL (25.5-26.0 nm, P = 0.01). The high MUFA diet also reduced body weight, and LDL-C and LDL-apolipoprotein (apo)B levels, which were comparable to those in the high CHO group. The cholesterol levels of small LDL particles tended to be reduced (P = 0.24) in the high MUFA group (-12%), similar to changes in the high CHO group. These results suggest that, when associated with weight loss, ad libitum consumption of high CHO and high MUFA diets may be considered to be equally beneficial for the management of LDL-related atherogenic dyslipidemia. However, the high MUFA diet more favorably affected triglyceride levels, suggesting that it may be preferable to a high CHO diet in cardiovascular disease prevention.

Association between past infection with Chlamydia pneumoniae and body mass index, low-density lipoprotein particle size and fasting insulin

BACKGROUND

Chlamydia pneumoniae infection has been linked to the development of coronary heart disease (CHD), but its relationship to CHD risk factors is less clear.

OBJECTIVE

To determine the relationship between past infection with C. pneumoniae and risk factors for CHD, including body weight amongst subjects with and without CHD.

METHODS

Antibodies to C. pneumoniae and a range of CHD risk factors were determined in 170 subjects, of whom 43 had recent onset angina. Anthropometric, haemodynamic, lipid and metabolic measurements were obtained and related to antibody status in univariate and multivariate analyses.

RESULTS

IgG seropositive (n = 62) did not differ from seronegative subjects in age but were significantly heavier (26.6 +/- 0.4 vs 25.5 +/- 0.3 kg/m2, P = 0.02). The prevalence of seropositivity was similar for subjects with and without CHD and for those with or without hypertension. Subjects with fasting insulin levels greater and those with LDL diameters below the median also had a significantly higher prevalence of seropositivity (45.3 vs 27.3%, P = 0.015 and 45.0 vs 29.4%, P = 0.045 respectively). However in multivariate analysis only body mass index remained significant (P < 0.05). Results were not explained by differences in socioeconomic class.

CONCLUSION

Although the study has failed to find a greater prevalence of antibodies to C. pneumoniae amongst subjects with recent onset angina there were associations with a number of cardiovascular risk factors. An increase in body weight appears to underlie these relationships.

Health outcomes of severely obese type 2 diabetic subjects 1 year after laparoscopic adjustable gastric banding

OBJECTIVE

To prospectively examine the effect of weight loss 1 year after laparoscopic adjustable gastric band surgery on a broad range of health outcomes in 50 diabetic subjects.

RESEARCH DESIGN AND METHODS

A total of 50 (17 men, 33 women) of 51 patients with type 2 diabetes, from a total of 500 consecutive patients, were studied preoperatively and again 1 year after surgery.

RESULTS

Preoperative weight and BMI (means +/- SD) were 137 +/- 30 kg and 48.2 +/- 8 kg/m(2), respectively; at 1 year, weight and BMI were 110 +/- 24 kg and 38.7 +/- 6 kg/m(2), respectively. There was significant improvement in all measures of glucose metabolism. Remission of diabetes occurred in 32 patients (64%), and major improvement of glucose control occurred in 13 patients (26%); glucose metabolism was unchanged in 5 patients (10%). HbA(1c) was 7.8 +/- 3.2% preoperatively and 6.2 +/- 2.7% at 1 year (P < 0.001). Remission of diabetes was predicted by greater weight loss and a shorter history of diabetes (pseudo r(2) = 0.44, P < 0.001). Improvement in diabetes was related to increased insulin sensitivity and beta-cell function. Weight loss was associated with significant improvements in fasting triglyceride level, HDL cholesterol level, hypertension, sleep, depression, appearance evaluation, and health-related quality of life. Early complications occurred in 6% of patients (wound infections in 4%, respiratory support in 2%), and late complications occurred in 30% of patients (gastric prolapse in 20%, band erosion in 6%, and tubing leaks in 4%). All late complications were successfully revised surgically.

CONCLUSIONS

Modern laparoscopic weight-loss surgery is effective in managing the broad range of health problems experienced by severely obese individuals with type 2 diabetes. Surgery should be considered as an early intervention.

A disparity between conventional lipid and insulin resistance markers at body mass index levels greater than 34 kg/m(2)

OBJECTIVE

The aim of this study was to examine changes in lipid profile and markers of insulin resistance with increasing body mass index (BMI) in the range 34-77 kg/m(2). In addition we compare the lipid profiles of severely obese patients with those of the Australian community.

SUBJECTS AND METHODS

A total of 572 patients (85% F, 15% M) were assessed prior to gastric restrictive surgery. Conventional lipid profiles and markers of insulin resistance were measured. Lipids were compared with the Australian National Heart Foundation 1989 study (control group).

RESULT

There was no difference in mean total cholesterol levels between the obese group (5.52 mmol/l) and the control group (5.47 mmol/l). The mean total cholesterol levels in the obese group fell with increasing BMI (r=-0.13, P<0.01). Obese subjects had elevated fasting triglyceride levels 1.96 mmol/l (control group, 1.12 mmol/l, P<0.001), but levels did not change with increasing BMI (r=0.0, NS). HDL-C levels were lower, 1.21 mmol/l (control group 1.44 mmol/l, P<0.001), and decreased with increasing BMI (r=-0.20, P<0.01). LDL-C levels were lower in obese men (3.65 mmol/l vs control group 4.17 mmol/l, P<0.01) but not women and levels fell with increasing BMI (r=-0.15, P<0.05). For the obese group, markers of insulin resistance (fasting plasma glucose, HbA1c, fasting plasma insulin and C-peptide) all rose significantly with increasing BMI.

CONCLUSION

Raised total cholesterol is not a co-morbidity of severe obesity. There is a disparity between the conventional lipid measures and insulin resistance measures of the metabolic syndrome with increasing BMI. Conventional lipid measures may be poor indicators of dyslipidaemic risk in the severely obese.

LDL particle size in relation to intima-media thickness and plaque occurrence in the carotid and femoral arteries in patients with hypercholesterolaemia

OBJECTIVES

Small LDL particle size has been shown to be associated with coronary artery disease. However, no previous study has been performed relating LDL particle size to ultrasound measurement of atherosclerosis in hypercholesterolaemic subjects. The main aims of the present study were therefore: (i) to investigate the relationship between intima-media thickness (IMT) of the carotid bulb and LDL particle size in patients with primary hypercholesterolaemia (n = 102) and in matched normocholesterolaemic controls (n = 102); and (ii) to investigate the relationship between plaque occurrence in the carotid and femoral arteries and LDL particle size. LDL particle size was determined by subjecting serum to 2-16% polyacrylamide gradient gel electrophoresis.

RESULTS

The results showed that patients with primary hypercholesterolaemia had smaller LDL peak particle size compared with healthy control subjects (P < 0.001 for men, P = 0.006 for women). However, the difference in LDL peak particle size between patients with hypercholesterolaemia and controls disappeared when adjusting for serum triglycerides. There was no association between increasing IMT of the carotid bulb and decreasing LDL peak particle size or between the occurrence of moderate to large plaques in the carotid and femoral arteries and small LDL peak particle size. However, metabolic variables such as serum triglycerides, HDL, blood glucose, body mass index, and also systolic blood pressure were associated with LDL peak particle size.

CONCLUSION

The lack of an association between atherosclerosis, as measured by ultrasound, and small LDL particle size in patients with hypercholesterolaemia implies that other risk factors, such as hypercholesterolaemia and high blood pressure, may overshadow any importance of small LDL particle size.

Omacor in familial combined hyperlipidemia: effects on lipids and low density lipoprotein subclasses

Elevations of plasma cholesterol and/or triglycerides, and the prevalence of small, dense LDL particles remarkably increase coronary risk in patients with familial combined hyperlipidemia (FCHL). A total of 14 FCHL patients were studied, to investigate the ability of Omacor, a drug containing the n-3 fatty acids eicosapentaenoic and docosahexaenoic acid (EPA and DHA), to favorably correct plasma lipid/lipoprotein levels and LDL particle distribution. The patients received four capsules daily of Omacor (providing 3.4 g EPA+DHA per day) or placebo for 8 weeks in a randomized, double-blind, cross-over study. Omacor significantly lowered plasma triglycerides and VLDL-cholesterol levels, by 27 and 18%, respectively. Total cholesterol did not change but LDL-cholesterol and apolipoprotein B (apoB) concentrations increased by 21 and 6%. As expected, LDL particles were small (diameter=24.9+/-0.3 nm) and apoB-rich (LDL-cholesterol/apoB ratio=1.27+/-0.26) in the selected subjects. After Omacor treatment LDL became enriched in cholesterol (LDL-cholesterol/apoB ratio=1.40+/-0.17), mainly cholesteryl esters, indicating accumulation in plasma of more buoyant and core enriched LDL particles. Indeed, the separation of LDL subclasses by rate zonal ultracentrifugation showed an increase of the plasma concentration of IDL and of the more buoyant, fast floating LDL-1 and LDL-2 subclasses after Omacor, with a parallel decrease in the concentration of the denser, slow floating LDL-3 subclass. However, the average LDL size did not change after Omacor (25.0+/-0.3 nm). The resistance of the small LDL pattern to drug-induced modifications implies that a maximal lipid-lowering effect must be achieved to reduce coronary risk in FCHL patients.

Cholesteryl ester enrichment of plasma low-density lipoproteins in hamsters fed cereal-based diets containing cholesterol

Male Syrian hamsters were fed 0.02, 0.03, or 0.05% cholesterol to test the hypothesis that moderate cholesterol intake increases the cholesteryl ester content of the plasma low-density lipoproteins (LDL). Dietary cholesterol levels of 0.02%-0.05% were chosen to reflect typical human intakes of cholesterol. Hamsters were fed ad libitum a cereal-based diet (modified NIH-07 open formula) for 15 weeks. Increasing dietary cholesterol from 0.02% to 0.05% resulted in significantly increased plasma LDL and high-density lipoprotein cholesterol concentration, increased liver cholesterol concentration, and increased total aorta cholesterol content. The cholesteryl ester content of plasma LDL was determined as the molar ratio of cholesteryl ester to apolipoprotein B and to surface lipid (i.e., phospholipid + free cholesterol). Increasing dietary cholesterol from 0.02% to 0.05% resulted in significantly increased cholesteryl ester content of LDL particles. Furthermore, cholesteryl ester content of LDL was directly associated with increased total aorta cholesterol, whereas a linear relationship between plasma LDL cholesterol concentration and aorta cholesterol was not observed. Thus, the data suggest that LDL cholesteryl ester content may be an important atherogenic feature of plasma LDL.

The oxidative stress hypothesis of atherosclerosis: cause or product?

The oxidative stress hypothesis postulates that endogenous free radicals of unknown origin, possibly derived from mural cells, oxidize low density lipoproteins and that oxidation products are allegedly responsible for initiation and progression of atherosclerosis. The thesis fails to explain its topography, site specific severity and the iatrogenic and experimental hemodynamic induction of atherosclerosis under conditions complying with the logic of Koch's postulates. Free radicals are generated by biomechanical scission of macromolecules and polymers, the biophysical mechanism underlying bioengineering fatigue in atherogenesis with oxidative damage a secondary, contributory factor to mural pathology. The plentiful supply of antioxidants negates oxidative stress as the dominant factor in atherogenesis.

Independent effects of Apo E phenotype and plasma triglyceride on lipoprotein particle sizes in the fasting and postprandial states

LDL particle sizes and Apo E phenotypes were determined in 212 subjects of whom 51 had angina. LDL diameter was significantly less in subjects with an epsilon2 allele (24.76+/-0.08 vs 24.94+/-0.02 nm, P=0.02), and this was evident for both E2/E3 (24.77+/-0.09 nm) and E2/E4 (24.69+/-0.08 nm) phenotypes. Although there was a negative relation between LDL diameter and plasma triglyceride, the effect of apo E2 was still evident with adjustment for triglyceride. In multiple regression analysis, the significant determinants of LDL diameter were gender (with females having larger particles than males), body mass index, and the presence (or absence) of E2. HDL particle sizes and compositions were determined on fasting samples and, additionally, 5 and 8 hours after a fat-rich meal for 48 coronary heart disease cases and 49 control subjects. Fasting HDL particle sizes were not related to the presence of E2 but were significantly smaller for subjects possessing an epsilon4 allele (8. 09+/-0.08 vs 8.39+/-0.05 nm, P=0.003) and were negatively related to plasma triglyceride. However, the effect of E4 persisted after adjustment for triglyceride. In a multiple regression analysis, the only significant determinant of fasting HDL diameter was the presence (or absence) of E4 with fasting plasma triglyceride just failing to reach significance (P=0.06). There was a postprandial increase in HDL diameter that was less marked in subjects with coronary heart disease. The postprandial increase in HDL diameter was of sufficient magnitude to result in size reclassification of HDL particles. The influence of E4 was also evident at both postprandial time points. Compositional analysis demonstrated that the increase in HDL diameters postprandially could be attributed to triglyceride enrichment, with an accompanying fall in cholesterol ester content. Phospholipid changes postprandially were biphasic with an initial fall followed by a rise in concentration. The increase in triglyceride content was significantly less in those subjects with angina despite an equivalent rise in plasma triglyceride. The present study demonstrates significant, but different, effects of variation in apo E phenotype on the particle sizes of both HDL and LDL. Such effects were still evident with adjustment for differences in plasma triglyceride and suggests that variation in apo E phenotype exerts effects on lipoprotein particle sizes by mechanisms additional to those dependent on change in plasma triglyceride.

Principal component analysis of proton nuclear magnetic resonance spectra of lipoprotein fractions from patients with coronary heart disease and healthy subjects

Blood plasma was drawn from 12 healthy subjects and 12 patients with coronary heart disease (CHD). The lipoproteins were fractionated by serial ultracentrifugation. The methyl and methylene regions of proton nuclear magnetic resonance (1 H NMR) spectra of the lipoproteins very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL) were analysed by principal component analysis (PCA). Grouping patterns in the score plots and the profiles of the principal components revealed several characteristics of the spectra. LDL subparticle size among the CHD group was consistently skewed against smaller, denser subparticles. This feature was independent of the concentration of LDL cholesterol. Analysis of the LDL spectra by soft independent modelling of class analogy (SIMCA) showed that none of the samples from the CHD group could be assigned as healthy subjects (p < 0.05). We also found that the samples from the healthy subjects were associated with a higher concentration of HDL cholesterol and larger VLDL subparticles. The approach presented, in which PCA is used in combination with NMR spectroscopy, might be implemented in clinical studies to give information about lipoprotein subparticle distribution and lipid content.

The fatty acid distribution in low density lipoprotein in diabetes

Atherosclerosis is commonly found in diabetes. There is an association between small dense low density lipoprotein (LDL) phenotype, which is more prevalent in the diabetic state, and atherosclerosis. Small dense LDL is more easily oxidised and it is possible that fatty acid compositional changes, particularly an increase in polyunsaturated fatty acids, could underlie this association. However, there is little information about fatty acids in the different LDL phenotypes in the literature. This study examined LDL subfraction composition in 18 non-insulin-dependent diabetic (NIDDM) patients and 11 control subjects. LDL was isolated and fractionated into LDL 1, 2 and 3 by density gradient ultracentrifugation. NIDDM patients had significantly more fatty acids in all LDL subfractions than control subjects (P<0.01). Palmitic and linoleic acid were significantly greater in all subfractions in the diabetic patients compared to control subjects (P<0.01) and palmitoleic and oleic acids were also greater in LDL1 and LDL2 in diabetic patients (P<0.01). We conclude that in NIDDM fatty acids are increased in all LDL subfractions and this may be the reason for the increased atherosclerosis in diabetes irrespective of phenotype.

Endothelium-dependent relaxation by acetylcholine is impaired in hypertriglyceridemic humans with normal levels of plasma LDL cholesterol

OBJECTIVES

Patients with high triglyceride (of which very low density lipoproteins [VLDL] are the main carriers), but with normal low density lipoprotein (LDL) cholesterol levels, were examined for in vivo endothelium function status.

BACKGROUND

Very low density lipoproteins inhibit endothelium-dependent, but not -independent, vasorelaxation in vitro.

METHODS

Three groups were studied: 1) healthy volunteers (n = 10; triglyceride 1.24+/-0.14 mmol/liter, LDL cholesterol 2.99+/-0.24 mmol/liter); 2) hypertriglyceridemic (n = 11; triglyceride 6.97+/-1.19 mmol/liter, LDL cholesterol 2.17+/-0.2 mmol/liter, p < 0.05); and 3) hypercholesterolemic (n = 10; triglyceride 2.25+/-0.29 mmol/liter, LDL cholesterol 5.61+/-0.54 mmol/liter; p < 0.05) patients. Vasoactive responses to acetylcholine, sodium nitroprusside, noradrenaline, N(G)-monomethyl-L-arginine and postischemic hyperemia were determined using forearm venous occlusion plethysmography.

RESULTS

Responses to acetylcholine (37 microg/min) were significantly dampened both in hypercholesterolemic (% increase in forearm blood flow: 268.2+/-62) and hypertriglyceridemic patients (232.6+/-45.2) when compared with controls (547.8+/-108.9; ANOVA p < 0.05). Responses to sodium nitroprusside (at 1.6 microg/min: controls vs. hypercholesterolemics vs. hypertriglyceridemic: 168.7+/- 25.1 vs. 140.6+/-38.9 vs. 178.5+/-54.5% increase), noradrenaline, N(G)-monomethyl-L-arginine and postischemic hyperemic responses were not different among the groups examined.

CONCLUSIONS

Acetylcholine responses are impaired in patients with pathophysiologic levels of plasma triglycerides but normal plasma levels of LDL cholesterol. The impairment observed was comparable to that obtained in hypercholesterolemic patients. We conclude that impaired responses to acetylcholine normally associated with hypercholesterolemia also occur in hypertriglyceridemia. These findings identify a potential mechanism by which high plasma triglyceride levels may be atherogenic independent of LDL cholesterol levels.

Relationships between protein C, protein S, von Willebrand factor and euglobulin lysis time and cardiovascular risk factors in subjects with and without coronary heart disease

Measures of fibrinolytic and thrombotic function have been examined in 55 subjects with recently identified coronary heart disease, and age and sex matched control subjects. Measurements were particularly directed at factors and processes which could be affected by changes in endothelial function and included the euglobulin lysis time as well as plasma levels of von Willebrand factor (vWF). Plasma levels of protein S and protein C were also measured. Measurements were made before and after a period of 10-min veno-occlusion combined with rhythmic hand exercise. In addition anthropometric, haemodynamic and biochemical measurements (plasma lipids and apolipoproteins, glucose and insulin) were obtained and correlated with the haematological parameters. Protein S and vWF levels were significantly higher, both before and after veno-occlusive exercise, in subjects with CHD than in the asymptomatic controls. Euglobulin lysis times were not significantly different but only shortened on veno-occlusive exercise in those without CHD. Protein S levels were significantly correlated with systolic blood pressure, plasma total cholesterol, plasma triglyceride, plasma phospholipid, plasma fasting glucose and both apolipoprotein A1 and B levels. vWF levels were not significantly related to any of the other variables. Subjects whose pre-exercise euglobulin lysis times exceeded 6 h had significantly higher BMI, plasma total cholesterol, triglyceride, phospholipid, insulin, glucose and apoB concentrations and lower HDL cholesterol than those with lysis in less than 6 h. The findings from this study are consistent with a role for endothelial dysfunction in the production of atherosclerotic vascular disease and may indicate additional, non-haemodynamic, mechanisms for such an association. In addition, the relationship between elevated levels of protein S and CHD does not appear to depend on the demonstrated associations between protein S and a number of other cardiovascular risk factors.

Biologic markers as predictors of cardiovascular disease

Epidemiologic data obtained over the past 30 years suggest that a number of new biologic markers are associated with increased risk for cardiovascular disease. These include indices related to (1) altered glucose metabolism, particularly insulin resistance; (2) hyperlipidemia; (3) elevated levels of lipoprotein(a) and homocysteine; (4) increased levels of molecules reflecting decreased fibrinolysis and increased activation of the coagulation cascade; (5) elevations in cell adhesion molecules and other markers of endothelial function; and (6) elevations in molecules associated with infection, inflammation, and vascular remodeling. Changes in molecules associated with increased risk usually occur in clusters. This clustering suggests that effective treatment of one marker may have positive effects on multiple markers. Indeed, several studies have demonstrated that therapies designed to reduce hyperlipidemia may also lower the plasma levels of factors associated with increased coagulation and reduced fibrinolysis. Thus, careful assessment of patient risk factors, and the development of therapies directed toward chains of markers associated with increased risk, may significantly alter the course of cardiovascular disease.

Responses to endothelium-dependent agonists in subcutaneous arteries excised from hypercholesterolaemic men

1. Vasomotor function of the vascular endothelium was examined in human subcutaneous arteries excised from 8 hypercholesterolaemic and 7 normolipidaemic subjects. 2. Left gluteal skin biopsies were performed under local anaesthesia. Subcutaneous arteries were isolated and two vessels from each subject mounted in separate myographs. A 20 ml fasting blood sample was taken at the time of the biopsy. 3. Hypercholesterolaemic subjects had either never been treated with lipid lowering therapy or therapy had been stopped at least two weeks before the study (n = 2). At the time of the study total plasma cholesterol levels (control: 4.6+/-0.3 vs hypercholesterolaemic: 8.3+/-0.6 mmol l(-1): P < 0.01) were significantly elevated in hypercholesterolaemic subjects when compared with controls. 4. Full concentration-response curves to the vasoconstrictor noradrenaline and the vasodilators acetylcholine and substance P were constructed. A single point concentration-response to sodium nitroprusside (10 microM) was also obtained. Dilator responses were obtained in vessels pre-constricted with a submaximal concentration of noradrenaline. Vessels were then incubated for 30 min with either L- or D-arginine (10 microM) and the concentration-response curves to the three dilator agonists repeated in the presence of the amino acid. 5. Maximum relaxation responses to acetylcholine (control vs hypercholesterolaemic: 83.3+/-6.1% vs 47.4+/-13.5%; P < 0.05), but not to substance P or sodium nitroprusside, were dampened in the hypercholesterolaemic group when compared with controls. 6. Neither incubation with L-arginine nor D-arginine had any effect on maximum relaxation responses to acetylcholine in either the control group (pre L-arginine vs plus L-arginine: 83.3+/-6.1 vs 82.3+/-5.5%, pre D-arginine vs plus D-arginine: 98.9+/-1.2 vs 98.2+/-1.1%) or the hypercholesterolaemic group (pre L-arginine vs plus L-arginine: 47.4+/-13.5 vs 55.3+/-14.3%, pre D-arginine vs plus D-arginine: 43.3+/-13.6 vs 65.4+/-12.3%). 7. When results from the two study groups were pooled, the strongest predictor of maximum relaxation obtained to acetylcholine was apolipoprotein A1 (r = 0.67; P = 0.001). 8. In conclusion, relaxation responses mediated by the endothelium-dependent agonist acetylcholine, but not by substance P, are impaired in hypercholesterolaemic patients. L-Arginine did not improve the impaired relaxation responses to acetylcholine. We suggest that impaired endothelium-dependent relaxation is specific to acetylcholine and not to an abnormal L-arginine-nitric oxide pathway in subcutaneous arteries excised from this study group.