We investigated the influence of dietary flavonoids on alpha-tocopherol status and LDL peroxidation in rats fed diets enriched in either polyunsaturated fatty acids (PUFA) or monounsaturated fatty acids (MUFA). Diets equalized for alpha-tocopherol concentrations were or were not supplemented with 8 g/kg diet of flavonoids (quercetin + catechin, 2:1). After 4 wk of feeding, plasma lipid concentrations were lower in rats fed PUFA than in those fed MUFA with a significant correlation between plasma alpha-tocopherol and cholesterol concentrations, r = 0.94, P < 0. 0001). Dietary lipids influenced the fatty acid composition of VLDL + LDL more than that of HDL or microsomes. The resistance of VLDL + LDL to copper-induced oxidation was higher in rats fed MUFA than in those fed PUFA as assessed by the lower production of conjugated dienes and thiobarbituric acid reactive substances (TBARS) and by the >100% longer lag time for dienes production. (P < 0.0001). Dietary flavonoids significantly reduced by 22% the amounts of dienes produced during 12 h of oxidation in rats fed diets rich in PUFA and lengthened lag time 43% in those fed MUFA. Microsomes of rats fed MUFA produced approximately 50% less TBARS than those of rats fed PUFA (P < 0.0001) and they contained more alpha-tocopherol in rats fed MUFA than in those fed PUFA with higher values (P < 0. 0001) in both groups supplemented with flavonoids (P < 0.0001). Our findings suggest that the intake of dietary flavonoids is beneficial not only when diets are rich in PUFA but also when they are rich in MUFA. It seems likely that these substances contribute to the antioxidant defense and reduce the consumption of alpha-tocopherol in both lipoproteins and membranes.

Prior moderate exercise reduces plasma triglyceride (TG)-rich lipoprotein concentrations, mainly in the large very low-density lipoprotein (VLDL₁) fraction, but the mechanism responsible is unclear. We investigated the effects of brisk walking on TG-rich lipoprotein kinetics using a novel method. Twelve overweight/obese middle-aged men underwent two kinetic studies, involving infusion of Intralipid to block VLDL₁ catabolism, in random order. On the afternoon prior to infusion, subjects either walked on a treadmill for 2 h at ∼50% maximal oxygen uptake or performed no exercise. Multiple blood samples were taken during and after infusion for separation of Intralipid (S(f) 400) and VLDL₁ (S(f) 60-400). VLDL₁-TG and -apoB production rates were calculated from their linear rises during infusion; fractional catabolic rates (FCR) were calculated by dividing linear rises by fasting concentrations. Intralipid-TG FCR was determined from the postinfusion exponential decay. Exercise reduced fasting VLDL₁-TG concentration by 30% (P = 0.007) and increased TG enrichment of VLDL₁ particles [30% decrease in cholesteryl ester (CE)/TG ratio (P = 0.007); 26% increase in TG/apoB ratio (P = 0.059)]. Exercise also increased VLDL₁-TG, VLDL₁-apoB, and Intralipid-TG FCRs by 82, 146, and 43%, respectively (all P < 0.05), but had no significant effect on VLDL₁-TG or -apoB production rates. The exercise-induced increase in VLDL₁-apoB FCR correlated strongly with the exercise-induced changes in VLDL₁ CE/TG (r = -0.659, r = 0.020) and TG/apoB (r = 0.785, P = 0.002) ratios. Thus, exercise-induced reductions in VLDL₁ concentrations are mediated by increased catabolism, rather than reduced production, which may be facilitated by compositional changes to VLDL₁ particles that increase their affinity for clearance from the circulation.

OBJECTIVE

The metabolic syndrome is characterized by defective hepatic apolipoprotein B-100 (apoB) metabolism. Hepato-intestinal cholesterol metabolism may contribute to this abnormality.

METHODS

We examined the association of cholesterol absorption and synthesis with the kinetics of apoB in 35 obese subjects with the metabolic syndrome. Plasma ratios of campesterol and lathosterol to cholesterol were used to estimate cholesterol absorption and synthesis, respectively. Very-low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), and low-density lipoprotein apoB kinetics were studied using stable isotopy and mass spectrometry. Kinetic parameters were derived using multicompartmental modeling.

RESULTS

Compared with controls, the obese subjects had significantly lower plasma ratios of campesterol, but higher plasma ratios of lathosterol (p < 0.05 in both). This was associated with elevated VLDL-apoB secretion rate (p < 0.05) and delayed fractional catabolism of IDL and low-density lipoprotein-apoB (p < 0.01). In the obese group, plasma ratios of campesterol correlated inversely with VLDL-apoB secretion (r = -0.359, p < 0.05), VLDL-apoB (r = -0.513, p < 0.01) and IDL-apoB (r = -0.511, p < 0.01) pool size, and plasma lathosterol ratio (r = -0.366, p < 0.05). Subjects with low cholesterol absorption had significantly higher VLDL-apoB secretion, VLDL-apoB and IDL-apoB pool size, and plasma lathosterol ratio (p < 0.05 in both) than those with high cholesterol absorption.

CONCLUSIONS

Subjects with the metabolic syndrome have oversecretion of VLDL-apoB and decreased catabolism of apoB-containing particles and low absorption and high synthesis rates of cholesterol. These changes in cholesterol homeostasis may contribute to the kinetic defects in apoB metabolism in the metabolic syndrome.

OBJECTIVE

Because subclinical thyroid dysfunction may be a risk factor for cardiovascular disease, we evaluated the atherosclerosis tendency in subclinical hypothyroid (SCH) patients.

METHODS

Fifty-three subclinical hypothyroid patients (serum thyrotropin [TSH] concentrations >4.12 mU/L) were compared with a control group of 50 euthyroid subjects whose age, sex and body mass indices were similar to the patient group. We tested whether serum TSH concentrations were correlated with plasma total homocysteine concentration (tHcy), low-density lipoprotein cholesterol (LDL-C), very low-density lipoprotein cholesterol (VLDL-C), high-density lipoprotein cholesterol (HDL-C), total cholesterol (TC) and triglycerides (TG).

RESULTS

There was a significant statistical difference between the patient and control groups for normal free T4 (1.02+/-0.17 vs. 0.86+/-0.13, P<.001), TSH (1.64+/-1.02 vs. 6.62+/-2.61, P<.001), TC (185+/-39 vs. 206 +/- 42, P=.01), TG (103+/-54 vs. 132+/-85, P=.04), LDL-C (114+/-33 vs. 127+/-36, P=.04), and TC/HDL-C (3.81+/-106 vs. 4.19+/-1.02, P=.04), respectively. No statistically significant difference was found between the two groups for HDL-C, VLDLC, LDL-C/HDL-C, and tHcy. Serum TSH was significantly correlated with plasma tHcy (r=0.55; P=.001), TC (r=0.52; P=.001), LDL-C (r=0.49; P=.001), TC/HDL-C (r=0.38; P=.002) and LDL-C/HDL-C (r=0.36; P=.004) across all participants.

CONCLUSIONS

Our study suggests that the atherogenicity of SCH is not mediated by hyperhomocysteinemia. Associated hyperlipidemia may explain the observed increased risk of coronary artery disease in patients with SCH.

Hepatocytes express on their surfaces more than one class of receptors capable of mediating the internalization of lipoproteins. However, relatively little is known about the binding characteristics of hepatic receptors for various lipoproteins, about the regulation of the receptors, and about the consequences for intracellular lipid metabolism of uptake of lipoproteins via different classes of receptors. The aim of the present studies was to characterize the binding and degradation of various lipoproteins and their mutual competition for cellular processing. Since these kinds of studies may be more easily carried out in continuous established hepatoma cell lines than in nondividing primary hepatocyte cultures, we examined the lipoprotein receptor functions of a well differentiated rat hepatoma (H-35). Cells were grown to confluence in Eagle's minimal essential medium in 15% newborn calf serum. Medium then was changed to 15% lipoprotein-deficient serum for 44 hr before experiments. External binding of 125I-labeled rat plasma and intestinal lymph lipoproteins was assessed at 4 degrees C. Cellular uptake and degradation were assessed at 37 degrees C. Lipoproteins were isolated by fixed angle or zonal ultracentrifugation or by heparin affinity column chromatography and characterized as to their lipid and apoprotein compositions. Labeled low density (LDL), high density (HDL2), non-apoE-HDL, very low density lipoproteins (VLDL), and chylomicron remnants (CM-R) each manifested specific and saturable binding and degradation by the hepatoma cells. Competition experiments indicated that separate receptors were present for LDL, HDL2, and CM-R. Most of HDL2 appeared to be bound to the non-apoE-HDL receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

OBJECTIVE

To evaluate the accuracy of LDL cholesterol calculated with Friedewald's equation in the assessment of cardiovascular risk in NIDDM patients.

METHODS

The calculation of LDL cholesterol according to Friedewald's formula was compared with the measurement of LDL cholesterol separated by ultracentrifugation in 151 NIDDM patients with fairly good metabolic control (HbA1c < or =10%) and in 405 nondiabetic subjects.

RESULTS

Measured and calculated LDL cholesterol was found to be well correlated in both diabetic (r = 0.95) and nondiabetic (r = 0.97) subjects. Compared with measured LDL cholesterol, the calculated LDL cholesterol differed by>> or =10% in 34% of samples from diabetic patients and in 26% of samples from nondiabetic subjects (chi(2) = 3.885, P < 0.05). The percentage of error increased when the serum triglyceride (TG) level was>> or =200 mg/dl (2.26 mmol/l) and when the ratio of VLDL cholesterol to TG was <0.20 or >0.29 in both groups of subjects. Although the percentage of error from calculated LDL cholesterol was greater in diabetic than in nondiabetic subjects because of the greater prevalence of hypertriglyceridemia in the former group, the misclassification of coronary heart disease risk, according to the cutoff points of the National Cholesterol Education Program (NCEP), was similar in the two groups (25% in diabetic and 22% in nondiabetic subjects). In both groups of patients, the misclassification of coronary heart disease risk was higher when calculation of LDL cholesterol produced values near the cutoff points.

CONCLUSIONS

Although accuracy in the estimation of LDL cholesterol is less than ideal, Friedewald's equation seems to be of value in the correct assignment of coronary heart disease risk classes in the great majority of diabetic as well as nondiabetic subjects. Caution must be exercised for subjects in whom calculated LDL cholesterol is close to the cutoff points of the NCEP guidelines.

In a screening investigation in 1982, which included medical history, clinical examination, general laboratory investigation, and quantification of lipids, lipoproteins, and apoproteins A1 and B, 5020 male subjects aged 40 to 59 years took part. All subjects were free of any heart or vascular disease at the basic examination. Of them 40 suffered fatal or nonfatal myocardial infarction (MI) during the first 3-year observation period between January 1982 and December 1984 (incidence cases), the others remained free of heart or vascular diseases (reference group). Comparison with the reference group revealed a strong relationship between MI-incidence rate and LDL cholesterol (correlation coefficient according to univariate regression analysis r = +0.248; P value according to Chi-square test P less than 0.001). The relationship was less strong but significant for age (r = +0.189; P less than 0.001), total serum cholesterol (r = +0.197; P less than 0.001), and apoprotein B (r = +0.195; P less than 0.001). Although statistically significant, the relationships to the MI-incidence rate were comparatively weak for HDL cholesterol (r = -0.09; P less than 0.01), apo-A1 (r = -0.09; P less than 0.01), systolic blood pressure (r = +0.067; P less than 0.05), and blood glucose level (r = +0.066; P less than 0.05). Body mass index, diastolic blood pressure, and plasma levels of uric acid, triglycerides, and VLDL did not exert relevant influences on the MI-incidence rate in our study population.(ABSTRACT TRUNCATED AT 250 WORDS)

The aim of the present study was to investigate the associations between total adiposity, body fat distribution, and plasma lipoprotein levels within groups of women defined on the basis of apolipoprotein E phenotypes, in order to verify whether apoE polymorphism could modify these associations. In women having only apolipoprotein E3 isoforms (n = 24), body fat mass, the waist: hip circumference ratio, and computed tomography-derived total and intra-abdominal fat areas were all positively correlated with very low density lipoprotein (VLDL) and low density lipoprotein (LDL) lipids and apolipoprotein B concentrations. These body fatness variables were also negatively correlated with plasma high density lipoprotein (HDL) cholesterol concentration. These associations were, however, altered in the groups of women carrying either apoE2 or E4 isoforms. Indeed, in women carrying the apoE2 isoform (n = 22), body fatness variables were predominantly associated with VLDL components concentration (0.05 greater than P less than 0.01) and with LDL triglyceride content. No association was found between adiposity and LDL cholesterol or apolipoprotein B levels in these women. In contrast, no relationship was found between total adiposity, regional fat accumulation, and VLDL fraction in women carrying the apolipoprotein E4 isoform (n = 17). In this latter group, computed tomography-measured total abdominal fat accumulation was positively correlated with LDL apolipoprotein B (r = 0.58, P less than 0.05) concentration, whereas intra-abdominal fat accumulation was positively correlated with both LDL cholesterol and apolipoprotein B concentrations (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The physical properties of the core and the surface of five classes of human plasma lipoproteins were investigated using five fluorescent probes. The location of the fluorescence probes in the lipoprotein assembly was determined using collisional quenching and resonance energy transfer. The fluorophores monitor different regions of the lipoproteins, as shown by fluorescence quenching. Diphenylhexatriene (DPH) and methyl trans-parinaric acid (MTPA), which are apolar molecules, are localized mainly in the lipoprotein core. Their distribution into the surface is dependent upon the volume ratio of the hydrophobic part of the envelope and the core. The polar fluorophores, trimethylaminodiphenylhexatriene (TMADPH), hydroxycoumarin (HC) and trans-parinaric acid (TPA) are anchored in the glycerol skeleton region of the surface monolayer with the fluorophore group of HC in the headgroup region of the phospholipids. We determined the temperature-dependent steady-state fluorescence anisotropy (r) of these fluorophores in the four major classes of lipoproteins: VLDL, LDL, HDL2, HDL3 and in abnormal HDL from abetalipoproteinemia patients (HDLab). The hydrophobic probes, DPH and MTPA, reported the r values in the lipoproteins in the following order: LDL greater than HDL2 greater than HDL3 much greater than VLDL. This order correlates with the triglyceride-to-cholesterol ester (TG/CE) ratio in the core of lipoproteins. The polar probes HC, TPA and TMADPH reported the r value in a different order: HDL2, HDL3 greater than or equal to LDL much greater than VLDL. This is compatible with the decreasing order of the protein to lipid ratio in the envelope of these lipoproteins. HDLab was investigated by three fluorescent probes: DPH, TMADPH and HC. The anisotropy of DPH in HDLab was larger than that of either HDL2 or HDL3 in normal donors, probably due to the smaller TG/CE ratio in HDLab. The lower r values reported by HC and TMADPH for HDLab are not fully understood and may be related to other factors such as acyl chains composition. The characterization of lipoproteins by fluorescence depolarization using probes of known location in the lipoprotein assembly is very sensitive and may be used to report deviation from the norm.

OBJECTIVE

To evaluate the effects of the usual starting and next higher doses of ezetimibe/simvastatin and atorvastatin on the cholesterol content of lipoprotein subclasses in patients with type 2 diabetes and hypercholesterolaemia.

METHODS

This post hoc analysis compared the effects of treatment with ezetimibe/simvastatin 10/20 mg vs. atorvastatin 10 and 20 mg/day and ezetimibe/simvastatin 10/40 mg/day vs. atorvastatin 40 mg/day on the cholesterol content of lipoprotein subclasses in the modified intent-to-treat (mITT) population (n = 1013) and in subgroups of patients with triglyceride (TG) levels <200 mg/dl (n = 600) and>>or=200 mg/dl (2.6 mmol/l) (n = 413).

RESULTS

Ezetimibe/simvastatin significantly reduced low-density lipoprotein cholesterol (LDL-C) subclasses LDL(1)-C, LDL(2)-C and LDL(3)-C; real LDL-C (LDL-C(r)); intermediate-density lipoprotein cholesterol (IDL-C), IDL(1)-C, IDL(2)-C; very low-density lipoprotein cholesterol (VLDL-C), VLDL(3)-C; and remnant-like lipoprotein cholesterol (RLP-C) from baseline more than atorvastatin at all dose comparisons (p < 0.01) in the mITT population. Significant improvements were also observed in high-density lipoprotein cholesterol (HDL-C) subclass HDL(3)-C at the ezetimibe/simvastatin 10/20 mg vs. atorvastatin 20 mg and highest dose comparisons (p < 0.001) and in VLDL(1 + 2)-C at the lowest and highest dose comparisons (p < 0.001). Changes in LDL(4)-C and LDL-C subclass patterns (A, B and I) were comparable for both treatments. Generally, similar results were observed for patients with TG levels <200 and>>or=200 mg/dl (2.3 mmol). For both treatments, notable differences between TG subgroups were that patients with elevated TGs had smaller reductions in LDL(2)-C, slightly smaller decreases in all IDL subclasses and greater decreases in all VLDL-C subclasses than those with lower TG levels. Frequency of pattern B was also reduced more in patients with higher TGs for both treatments.

CONCLUSIONS

Ezetimibe/simvastatin reduced the cholesterol content of most lipoprotein subclasses from baseline with generally similar efficacy in patients with low and high TGs. Despite the different mechanism of action of ezetimibe, the response to ezetimibe/simvastatin and atorvastatin treatment related to these lipoprotein subclasses was generally consistent with the overall effects of these therapies on the major lipid/lipoprotein classes. The clinical significance of these results awaits further study.

Squalene, found in earlier studies in human atherosclerotic plaques, was measured in the serum of postmenopausal women with coronary artery disease (CAD) (n = 25) and randomly chosen age-matched healthy controls (n = 30). The squalene concentrations of the whole population ranged from 37.5 to 115.5 microg/dl, and were higher in serum of the CAD than healthy women (91.4+/-2.6 versus 65.2+/-2.6 microg/dl, P = 0.000), a finding observed also in relation to cholesterol (43.8+/-1.8 versus 32.9+/-1.1 10(2)x mmol/mol of cholesterol, P = 0.000). The squalene concentration was also increased in chylomicrons, VLDL and d>1.006 g/ml lipoproteins, and the proportions to cholesterol in VLDL and d>1.006 g/ml lipoproteins. The respective squalene and cholesterol concentrations were related to each other in serum, VLDL and d>1.006 g/ml lipoproteins (r = 0.52, 0.85 and 0.55, respectively), whereas the correlation with triglycerides was seen only in VLDL (r = 0.84) over the whole population. Besides enhanced intestinal secretion, it remains to be shown whether higher serum squalene in postmenopausal coronary women is due to increased cholesterol synthesis or a defect in squalene conversion to lanosterol.

The effects of lipid lowering therapy (bezafibrate) on plasma lipoproteins was investigated in twelve patients with familial hypercholesterolaemia (type IIA) and eight with familial combined hyperlipidaemia (type IIB). Bezafibrate caused a decrease of plasma cholesterol, plasma triglycerides, plasma apolipoprotein B, VLDL cholesterol and LDL cholesterol and an increase of HDL cholesterol. Post-heparin plasma lipoprotein and hepatic lipase activities increased in both groups (significant only in type IIB). Lipoprotein composition showed the following changes: Increased protein and phospholipids and decreased triglycerides and cholesteryl esters in VLDL. Decreased protein and triglycerides and increased free and esterified cholesterol in LDL. Decreased triglycerides and increased phospholipids in HDL. Cholesteryl ester to protein ratios decreased in VLDL and increased in LDL. The hydrated density of LDL (both groups) and of HDL3 (type IIB) decreased following bezafibrate therapy. These changes were in general similar to those observed in hypertriglyceridaemic patients and could be ascribed, at least in part, to the increase of plasma lipase activities and the decrease of lipid transfer reactions. Comparing the present data with that previously reported, it was found that bezafibrate caused decreased LDL cholesterol in types IIA and IIB but increased levels in type IV. This change was correlated with the initial plasma triglycerides (r = 0.74, P less than 0.0001) and initial plasma LDL cholesterol (r = 0.66, P less than 0.001). It is concluded that varied response of LDL to therapy reflects a complex interaction of metabolic events, including changing rates of VLDL conversion to LDL, lipoprotein compositional changes and effects of therapy on LDL degradation rates.

The effect of dietary fat on hepatic microsomal triglyceride transfer protein(MTP) large subunit mRNA levels in the hamster was examined. Increasing the dietary fat concentration from 11.7 energy % to 46.8 energy % caused a 60% increase in hepatic MTP mRNA; this increase was shown to be dose-dependent (r = 0.688 p = 0.0023). MTP mRNA levels correlated significantly with several plasma lipoprotein cholesterol parameters. No significant relationship was observed between MTP mRNA and either plasma or VLDL triglyceride. The nature of the dietary fatty acids also influenced MTP mRNA levels, with trimyristin and tripalmitin enriched diets significantly elevating MTP mRNA relative to diets enriched in triolein and trilinolein.

Triglyceride-rich lipoprotein (TRL) remnants have been strongly implicated in the pathogenesis of atherosclerosis. To further investigate plasma remnant lipoprotein metabolism, we have determined the plasma concentration of apolipoprotein (apo) E (by polyclonal enzyme-linked immunoassay) in remnant-like lipoproteins, isolated by automated gel filtration chromatography as a fraction intermediate in size between VLDL and HDL. In normolipidemic subjects (n = 12), 1.2 +/- 0.11 mg/dL (33 +/- 2%, mean +/- SE) of total plasma apoE was associated with this fraction (termed ISL apoE). In hypercholesterolemic (type IIa, n = 12), hypertriglyceridemic (type IV, n = 12), and mixed hyperlipidemic (type IIb, n = 12) subjects, mean ISL apoE concentrations were 2.1 +/- 0.2, 2.5 +/- 0.2, and 3.8 +/- 0.4 mg/dL, respectively (P < .001 versus normal values) (45 +/- 2%, 32 +/- 2%, and 44 +/- 2% of total). ISL apoE was 8.7 +/- 1.4 mg/dL (42 +/- 3%) in type III dyslipidemic subjects (apoE2/2, n = 8). ISL apoE was positively correlated with plasma triglyceride (r = .41, P < .01), and at any given level of plasma triglyceride, subjects with an apoE2/2 or apoE3/2 phenotype tended to have a higher concentration of ISL apoE (P < .01) than apoE3/3 or E4/3 individuals. ISL apoE was also correlated (P < .001) with total plasma cholesterol (r = .66), TRL cholesterol (r = .49), TRL apoE (r = .47), LDL apoB (r = .42), and LDL+HDL triglyceride (r = .74). These results suggest that (1) a significant proportion of plasma apoE resides within an intermediate-sized remnant-like lipoprotein fraction in both normolipidemic and hyperlipidemic subjects; (2) plasma remnant lipoprotein accumulation is associated with an elevation in ISL apoE concentration; and (3) ISL apoE concentration is significantly correlated with various proatherogenic lipid parameters and may itself be a potentially important atherogenic index.

The purpose of this study was to examine the effects on lipoprotein risk markers for CHD of oestradiol given alone and in combination with the androgenic progestogen, norethisterone. Eighty postmenopausal women were randomly allocated to receive oestradiol (2 mg/day) alone or with continuous norethisterone (1 mg/day). Serum lipoprotein levels, including lipoprotein(a), were monitored during 12 months on treatment in all the women, and in a sub-set of 32 patients cholesterol was measured in the two major density subfractions of LDL. Oestradiol caused a transient rise in triglycerides, a small decrease in LDL cholesterol (significant only at 3 and 6 months, P < 0.05) and a consistent significant increase in HDL cholesterol (16%, P < 0.01). There was a downward trend in lipoprotein(a) levels which did not achieve statistical significance. The combined preparation caused significant, sustained decreases in triglycerides (31%, P < 0.01), total cholesterol (15%, P < 0.001), VLDL (42%, P < 0.01), LDL (9%, P < 0.05) and HDL (11%, P < 0.001). Lipoprotein(a) was also reduced (39%, P < 0.05). In the sub-set of patients in which LDL subfractions were measured, the reduction in LDL induced by oestradiol monotherapy was significant only at the 3-month visit (6%, P < 0.05). This was due to a decrease in the 'light' (1.025 < d < 1.044 g/ml) subfraction (10%, P < 0.05) and resulted in an apparent shift in subfraction distribution towards the 'heavy' (1.044 < d < 1.060 g/ml) subfraction, although there was no absolute increase in the latter. None of these changes was statistically significant at 12 months. Oestradiol/norethisterone caused sustained decreases in both 'light' (15%, P < 0.05) and 'heavy' (29%, P < 0.05) subfractions, with no significant change in the relative amounts. The changes in 'light' and 'heavy' LDL in this group were highly correlated with changes in triglyceride levels (r = -0.57, P < 0.05 and r = 0.82, P < 0.01 respectively). Therefore, at the end of 1 year's treatment with unopposed oestradiol the only statistically significant change was an increase in HDL cholesterol. Addition of norethisterone to the preparation reversed this potentially beneficial change, but favourably influenced triglycerides, VLDL, LDL subfraction profile and lipoprotein(a), which may counteract the adverse effect on HDL.

OBJECTIVE

To determine the relationship between plasma adiponectin levels and obesity, inflammation, blood lipids and insulin resistance in type 2 diabetics (T2DM) and non-diabetics in a patient population in Trinidad.

METHODS

A cohort study of a total of 126 type 2 diabetic (42 males and 84 females) and 140 (43 males and 97 females) non-diabetic public clinic attendees were assessed between December 2008 and July 2009. Along with clinical history and anthropometry, adiponectin, TNF-α, IL-6, CRP, lipid profile, glucose, and insulin were measured in fasting blood samples and insulin resistance (HOMA-IR) was calculated.

RESULTS

Diabetics had higher (p<0.05) glucose, insulin, HOMA-IR, triglycerides (TG), VLDL and systolic blood pressure than non-diabetics, but lower (p<0.05) HDL and adiponectin levels. Adiponectin levels were lower (p<0.05) in obese than in non-obese individuals regardless of diabetic status. There were significant gender differences in HDL, LDL and TG. Among non-obese persons, adiponectin correlated negatively with triglycerides (r=-0.280; adiponectin), IL-6 (r=-0.216; p<0.005), HOMA-IR (r=-0.373; p=000) and positively correlated with HDL (r=0.355; p=0.000). Diabetic status (p=0.025), TNF-α (p=0.048) and BMI (p=0.027) were identified as useful predictors of adiponectin by multiple linear regression methods. In addition binary logistic regression analysis found glucose (p=0.001) and adiponectin (p=0.047) to be useful indicators of type 2 diabetes.

CONCLUSIONS

Adiponectin decreases with increasing adiposity and insulin resistance. Adiponectin and TNF-α appear to be related to differences in the insulin mediated glucose turnover.

Fast lipoprotein chromatography (FLPC) is a novel method for quantifying lipoproteins. Plasma proteins are separated by fast-flow gel filtration. Lipoproteins are detected by post-column derivatization with an enzymatic cholesterol reagent. FLPC resolves very-low-, low-, and high-density lipoproteins (VLDL, LDL, and HDL, respectively) and completely separates apolipoprotein Al- and apolipoprotein B-containing lipoproteins. CVs for VLDL-cholesterol, LDL-cholesterol, and HDL-cholesterol are 5.8%, 2.0%, and 1.9%, respectively. We compared FLPC with a combined ultracentrifugation and precipitation method and obtained correlation of r = 0.979, 0.978, and 0.933 for VLDL-cholesterol, LDL-cholesterol, and HDL-cholesterol, respectively. Triglyceride concentrations up to 9.00 g/L did not interfere with the quantification of lipoproteins by FLPC. We conclude that FLPC is a precise and reliable method for the analysis of plasma lipoproteins that complements conventional techniques.

OBJECTIVE

Diabetic dyslipidaemia, characterized by hypertriglyceridaemia as a result of elevated serum very-low-density lipoprotein (VLDL) concentrations, contributes to the increased risk of cardiovascular disease (CVD) in type 2 diabetes (T2DM). Proprotein convertase subtilisin/kexin type 9 (PCSK9) may play a role in regulating VLDL metabolism. We investigated the effect of fenofibrate on serum PCSK9 and VLDL particle concentrations in T2DM patients already receiving statin therapy.

METHODS

In a double-blind randomized crossover study, 15 statin-treated T2DM patients (63 +/- 8 years, body mass index (BMI) 29 +/- 3 kg/m(2)) were treated with fenofibrate (145 mg/day) or matching placebo for 12 weeks. Serum PCSK9 concentrations were measured by immunoassay. VLDL particle concentration and size were determined by nuclear magnetic resonance spectroscopy.

RESULTS

Fenofibrate decreased serum triglycerides (-23%), VLDL-triglycerides (-51%), total cholesterol (-11%), LDL-cholesterol (-16%), apolipoprotein B-100 (-16%), apolipoprotein C-III (-20%) and PCSK9 (-13%) concentrations compared with placebo (p < 0.05). Fenofibrate also decreased serum concentrations of large (-45%), medium (-66%) and small VLDL (-67%) particles (p < 0.05), without altering VLDL particle size. Serum PCSK9 reduction correlated with decreases in total (r = 0.526, p = 0.044) and small (r = 0.629, p = 0.021) VLDL particle concentrations.

CONCLUSIONS

Fenofibrate concomitantly decreased serum PCSK9 and VLDL particle concentrations in statin-treated T2DM patients. These findings support a mechanistic link between PCSK9 and VLDL metabolism, possibly through an effect of PSK9 on VLDL receptor degradation.

An inherited metabolic disorder in a strain of New Zealand White rabbits, characterized by marked hypercholesterolemia (394 +/- 100 mg/dl), with moderately elevated or normal triglyceride levels is described. Low density lipoprotein (LDL), intermediate density lipoprotein (IDL) and very low density lipoprotein (VLDL) cholesterol levels were increased. VLDL and IDL, and to a lesser extent LDL, had increased free cholesterol and esterified cholesterol content, and triglyceride content was reduced. Kinetic studies with 131I and 125I-labelled rabbit lipoproteins showed a marked increase in production rates of VLDL apo B and LDL apo B. LDL cholesterol levels were directly related to LDL apo B production rate (r = 0.938, p less than 0.001). Both in hypercholesterolemic and normal rabbits injected with labelled VLDL, the specific activity-time curves of VLDL apo B and LDL apo B did not intersect, indicating that LDL apo B was in part derived from sources other than VLDL. No defect was demonstrated in receptor-mediated catabolism of LDL by cultured skin fibroblasts from hyperlipidemic animals. The fractional catabolic rate of LDL apo B was subnormal, but increased when the expanded LDL apo B pool size was reduced by exchange transfusion; the low fractional catabolism may therefore be attributable, at least in part, to saturation of LDL receptors consequent upon the increased pool size of LDL. The hyperlipidemia in this strain of rabbits may be unique in that the underlying mechanism appears to be overproduction of VLDL and LDL.

The aim of this study was to evaluate the effect of sc insulin (INS) compared with sulfonylurea (SUL) therapy, at the same level of blood glucose control, on the low density lipoprotein (LDL) subfraction profile in normolipidemic type 2 diabetic patients. Nine normolipidemic type 2 diabetic men (age, 56+/-3 yr; body mass index, 26.5+/-0.9 kg/m2; mean +/- SEM), after a 3-week wash-out period, were assigned to INS or SUL for 2 months in a randomized cross-over design. Doses were adjusted only during the first month and then were kept constant. At the end of the treatments, hemoglobin A1c, plasma lipids, LDL, and very low density lipoprotein (VLDL) subfraction profiles and plasma postheparin lipoprotein lipase and hepatic lipase (HL) activities were evaluated. Despite glucose control was similar at the end of both periods (hemoglobin A1c, 7.4+/-0.3% vs. 7.0+/-0.2%, INS vs. SUL), INS compared with SUL significantly reduced plasma triglyceride (0.9+/-0.1 vs. 1.1+/-0.1 mmol/L; P < 0.05). Although INS did not affect the LDL concentration, it induced a decrease in both the amount (59.0 = 9.8 vs. 76.1+/-16.8 mg/dL; P = NS) and the proportion (31.2+/-3.0% vs. 38.3+/-3.8%; P < 0.03) of small LDL. Moreover, the decrease in small LDL was positively related to the reduction of large VLDL (r = 0.67; P < 0.04) and HL (r = 0.69, P < 0.05) induced by insulin therapy. In conclusion, sc insulin therapy, independently of glucose control and even in the presence of quite low plasma triglyceride levels, is able to reduce small LDL particles in type 2 diabetic patients. This change is related to decreases in both HL activity and large VLDL particles.

OBJECTIVE

The rate of type II diabetes in African-Americans is reaching epidemic proportions. African-Americans with type II diabetes suffer from more cardiovascular diseases (CVDs) associated with diabetes than the general population. Lower socioeconomic status (SES) and family history are often cited as contributory factors to the premature development of diabetes and CVDs in the general population. However, we are not aware of any study that has examined the relationships between SES and CVD risk factors (i.e., syndrome X) in a genetically enriched African-American population at high risk for type II diabetes.

METHODS

We studied 200 healthy first-degree relatives of African-American patients with type II diabetes (age 25-65 years, mean 42.5 +/- 8.4 years; 42 men, 158 women). Standard oral glucose tolerance test, metabolic, and anthropometric parameters, as well as questionnaires on SES, demographic characteristics, and physical activity, were obtained for each subject. SES was divided into quartiles based on annual income. To assess the impact of insulin on CVD risk, we examined clinical characteristics and metabolic parameters according to quartiles of fasting insulin concentrations.

RESULTS

Clinical characteristics, including mean age, BMI, waist-to-hip ratio (WHR), percentage body fat and lean body mass, and blood pressure were not statistically different among SES quartiles. There were no significant differences in any of the metabolic, blood pressure, lipid and lipoprotein, or anthropometric parameters among SES quartiles. When examined by insulin quartile, BMI, WHR, and body fat content tended to be greatest in the fourth quartile. Similarly, fasting and postprandial serum C-peptide and glucose levels were significantly higher in the fourth quartile. We observed greater levels of very low density lipoprotein (VLDL) cholesterol and triglycerides and lower levels of HDL cholesterol in the fourth compared with the first through third insulin quartiles. Serum cholesterol and LDL cholesterol were not associated with increasing insulin concentration assessed by quartiles. We found similar systolic and diastolic blood pressure, irrespective of insulin quartiles. We found relationships between fasting insulin and systolic blood pressure (r = 0.181, P < 0.05) and triglycerides (r = 0.247, P < 0.01), VLDL cholesterol (r = 0.237, P < 0.01), WHR (r = 0.268, P < 0.005), BMI (r = 0.308, P < 0.001), and percentage of body fat (r = 0.237, P < 0.01).

CONCLUSIONS

The present study demonstrates no SES/income effect on CVD risk factors or syndrome X in African-Americans at high risk for type II diabetes. Clustering of several components of syndrome X was seen in individuals in the highest quartiles compared with the lowest quartiles of insulin in our high-risk African-American population. We conclude that the well-established conventional risk factors for CVD in genetically enriched African-Americans are found only in individuals with the highest insulin levels, independent of SES.

CETP activity, measured as transfer of cholesteryl ester from exogenous HDL to exogenous VLDL and LDL, reflecting CETP mass as determined by ELISA, was documented in three groups of St. Kitts vervet monkeys fed diets enriched in saturated (Sat), monounsaturated (Mono), or n-6 polyunsaturated (Poly) fatty acids. CETP activity was not different when comparing the three dietary fats. However, CETP activity was significantly higher when cholesterol was added to each of the diets. Significant positive associations between CETP activity and VLDL and LDL cholesterol concentrations were found whereas significant negative associations were seen between CETP activity and HDL cholesterol in each of the diet groups. The strength of these associations was highest in the Sat group. Cholesteryl ester (CE) fatty acid composition of lipoproteins varied widely among diet groups, with the more polyunsaturated CE of the Poly group being associated with a higher rate of CE transfer to endogenous acceptor apolipoprotein B-containing lipoproteins. Finally, only the Sat diet group showed significant positive correlations of CETP activity with LDL particle diameter (r = 0.76), cholesteryl ester percentage (r = 0.67), and a strong negative correlation (r = -0.86) with LDL receptor function, estimated as the difference between native and methylated LDL turnover rates. We speculate that strong associations between CETP and LDL metabolism may explain, at least in part, the increased atherogenicity of dietary saturated fat.

To determine whether hydrogenated fat consumption alters triglyceride metabolism and cholesterol esterification rates, 14 women (65-71 years of age) were provided with each of four diets for 5-week periods according to a randomized cross-over design. The experimental diets contained either soybean oil (SO), low trans squeeze (SQM), medium trans tub (TM), or high trans stick (SM) margarines. Triglyceride uptake by adipose tissue was determined by measuring plasma acylation-stimulating protein (ASP), FFA, glucose, and insulin levels, while rates of transfer and esterification rate of newly synthesized cholesterol (ER) were derived by using plasma CETP levels and the deuterium incorporation methodology. Plasma ASP levels were lowest (P < 0.05) in subjects on the SM diet (33.4 +/- 12.7 nM) compared with the SO (48.7 +/- 17.0 nM) and SQM (50.7 +/- 15.7 nM) diets. Conversely, FFA were highest (P < 0.05) on the SM diet (0.86 +/- 0.45 mM) relative to all the other diets. No differences were observed in plasma glucose and insulin levels among diets. A trend toward higher CETP levels after consumption of the SM diet was observed. However, the ER was lowest (P < 0.05) after the SM (0.111 +/- 0.062 g x day(-1)) diet and highest after consumption of the SQM (0.216 +/- 0.123 g x day(-1)) diet. In addition, ASP levels were negatively correlated with FFA (r = -0.63, P < 0.05), LDL cholesterol (r = -0.56, P < 0.05), and TG (r = -0.41, P < 0.05), whereas FFA was positively correlated with apolipoprotein B-containing lipoproteins (r = 0.58 and 0.47, for VLDL and LDL cholesterol, P < 0.05), and negatively correlated with HDL cholesterol (r = -0.51, P < 0.05). The ER was found to positively correlate with HDL cholesterol and HDL2 subfraction (r = 0.53 and 0.45, respectively, P < 0.05). Taken together, these data demonstrate that the alterations in circulating lipid levels, commonly observed with consumption of hydrogenated fat-rich diets, can be explained in part by changes in ASP activity as well as newly synthesized cholesterol ER.

The present study was carried out on 20 female patients diagnosed with acute coronary syndrome (ACS). The control group was composed of 20 healthy female volunteers. Plasma malondialdehyde (MDA) levels and serum zinc (Zn), total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and VLDL-cholesterol, Lp(a), Apo-A1, and Apo-B were determined in all patients and controls. Plasma MDA levels were determined to be significantly high in patients with ACS compared to the controls (1.75+/-0.27 vs 0.8+/-0.43 nmol/mL; p<0.05). On the other hand, Zn levels in patients with ACS were determined to be significantly low compared to the control group (67.9+/-14.8 vs 101.8+/-22.4 mg/dL; p<0.05). There was a statistically significant negative correlation between MDA and Zn levels in patients with ACS (r = -0.678, p<0.05). Other lipid parameters were significantly altered in patients with ACS compared to the controls (p<0.05). In conclusion, Zn and lipid peroxidation levels are important in patients with ACS and they must be monitored during diagnosis and treatment of these patients.