Because we found apoprotein contamination of some high-grade commercial albumins, we studied this effect on formation of lipoprotein-like particles during lipolysis of human very low density lipoprotein (VLDL) in vitro. After a 1-hr incubation with purified bovine milk lipoprotein lipase, over 98% VLDL triglyceride was hydrolyzed in the presence of either albumin B (apoprotein-rich) or albumin C (apoprotein-poor), with a weight ratio of albumin to triglyceride of 60 to 1. Lipoproteins of density < 1.019 g/ml ("IDL"), 1.019 to 1.063 g/ml ("LDL"), and 1.063 to 1.21 g/ml ("HDL") were then isolated by ultracentrifugation. Recovery of non-triglyceride VLDL constituents in "IDL" and "LDL" was similar for albumin B or albumin C. "LDL" was the major catabolic product of in vitro VLDL lipolysis independent of the albumin used. The yield of "HDL," however, was 5- to 6-fold greater with albumin B. All lipoproteins produced with albumin B were richer in phospholipid, apoproteins C and A-I, relative to lipoproteins produced in the presence of albumin C. With albumin B, cholesterol/phospholipid molar ratios were <1 in all in vitro produced lipoproteins, but were >1 with albumin C. All these differences can be ascribed to the presence in albumin B of 0.2 mg apoprotein A-I/g albumin and 1.8 mg phospholipid/g albumin; these components were not detected in albumin C. Thus, two thirds of "HDL" recovered with VLDL lipolysis in the presence of albumin B can be accounted for by albumin itself and only one third from constituents of VLDL. Adding equivalent amounts of both apoproteins removed from albumin B and phospholipid to albumin C markedly decreased the disparities in results but addition of each alone did not. These results prove "inert" albumins serve other than as fatty acid and lysolecithin acceptors in in vitro model systems, and do influence formation of lipoproteins during in vitro VLDL catabolism.-Deckelbaum, R. J., T. Olivecrona, and M. Fainaru. The role of different albumin preparations on production of human plasma lipoprotein-like particles in vitro.

Esterified cholesterol transfer (ECT) from high density lipoproteins (HDL) to very low (VLDL) and low density lipoproteins (LDL) may be abnormal in situations at high risk for atherosclerosis. It has been shown to increase in insulin-dependent diabetes and to decrease in non-insulin-dependent diabetes (NIDD). Since the net transfer of esterified cholesterol (EC) results from a bidirectional exchange between HDL and VLDL/LDL, we developed a transfer assay specifically designed to measure the unidirectional transfer of EC from HDL to lipid emulsions according to first-order kinetics. Our results show that in NIDD the rate constant of HDL-dependent ECT is decreased by 30% by comparison with control subjects. Analysis of HDL composition revealed that, in both groups, HDL-dependent ECT was positively correlated with the free cholesterol/phospholipid ratio (r = 0.94; P < 0.001) and negatively correlated with the triglyceride/EC ratio (r = -0.85; P < 0.001). It is concluded that, besides the known defect of acceptor lipoproteins, the abnormality of ECT in NIDD is also caused by a decreased ability of HDL to act as an EC donor, presumably because of a change in composition. In addition, our work shows that the amount of EC lost by HDL during the reaction transfer is counterbalanced by a reciprocal equimolar transfer of triglycerides.

Apolipoprotein (apo) E is a multifunctional protein that can act as a ligand for lipoprotein receptors. The receptor-mediated clearance of the triglyceride-rich lipoproteins (TRL) chylomicrons and VLDL from plasma is, in part, dependent on apo E. Enrichment of VLDL with apo E is thought to enhance receptor-mediated clearance of VLDL resulting in a low rate of conversion of VLDL to LDL. However, the kinetic mechanism controlling the concentration of apo E in VLDL is not known. We conducted kinetic studies on apo E in the TRL fraction (d < 1.006 g/ml) and apo B-100 in the TRL and LDL (d = 1.019-1.063 g/ml) fractions to assess the kinetic determinants of apo E concentration in TRL and to determine the effects that TRL apo E production and clearance rates have on the production rate of LDL apo B-100. Nineteen males between the ages of 24 and 73 underwent a primed-constant infusion with deuterated leucine tracer in the constantly-fed state. Apo B-100 from TRL and LDL, and apo E from TRL were isolated and their tracer incorporation measured by gas chromatography/mass spectrometry. The residence time and production rates of each protein were determined from the kinetic data using the SAAM II modeling program. The residence time and production rate of TRL apo E were about one-half that of TRL apo B-100 (1.8 +/- 1.0 vs. 2.9 +/- 2.1 h and 14.5 +/- 11.0 vs. 27.6 +/- 17.3 mg/kg per day, respectively). The production rate of TRL apo E was weakly correlated with the production rate of TRL apo B-100 (r = 0.424, P = 0.07). Multiple regression analysis showed that the residence time of TRL apo B-100 and the relative TRL apo E production rate (relative to the TRL apo B100 production rate) were negatively associated with LDL apo B-100 production rate, accounting for 68% of its variability. We conclude that (1) the concentration of apo E in TRL is highly correlated to its production rate, suggesting that production rate regulates the TRL apo E concentration, and (2) individuals with a relatively short TRL apo B-100 residence time and those producing TRL with a relatively low apo E content have the highest LDL apo B-100 production rates.

Human VLDL, LDL and HDL (very-low-, low-, and high-density lipoproteins) were isolated from plasma by gel permeation chromatography with one pre-ultracentrifugation step. The column effluent was monitored at 280 nm. The cholesterol content of the fractions correlated well with fractions from sequential ultracentrifugation (VLDL, r = 0.839; LDL, r = 0.924; HDL, r = 0.766) or precipitation (LDL, r = 0.975; HDL, r = 0.972) methods. The average triglyceride, phospholipid and protein compositions of the separated lipoprotein fractions were close to those of the ultracentrifugally isolated fractions reported previously. Apolipoproteins A1 and B were determined from fractions to confirm the right distribution between different lipoproteins.

In an attempt to establish relationships between the endocrine and lipid metabolism during pregnancy, the changes in total plasma cholesterol (TPC) and lipoprotein cholesterol that occur during pregnancy in the African green monkey were investigated longitudinally in ten females in relation to the changes in progesterone, estradiol, and fasting insulin concentrations. Respective means for TPC, high-density lipoprotein (HDL) cholesterol, and low-density lipoprotein (LDL) plus very low-density lipoprotein (VLDL) cholesterol were 343 +/- 35, 108 +/- 9, and 235 +/- 36 mg/dL prior to the estimated date of conception in ten females fed a high-fat, high-cholesterol diet. The concentration of these lipids fell to 225 +/- 31, 54 +/- 4, and 168 +/- 29 mg/dL for TPC (P less than 0.001), HDL cholesterol (P less than 0.001), and LDL + VLDL cholesterol (P less than 0.001), respectively, by midpregnancy (84 days). Progesterone concentrations increased during the first 60 days of pregnancy and were negatively correlated with HDL cholesterol concentrations (r = -0.57, P less than 0.02). After reaching their highest mean value, progesterone concentrations then plateaued at lower concentrations until parturition. The decrease in progesterone concentrations was associated with an initial rise in estradiol concentrations, which reached their highest concentrations in late pregnancy and were inversely correlated with HDL-cholesterol concentrations (r = -.32, P less than 0.01). Although glucose concentrations remained steady during gestation, insulin concentrations were elevated compared to postpartum concentrations (P less than 0.05) suggesting that insulin resistance occurred during the pregnancy in this nonhuman primate.(ABSTRACT TRUNCATED AT 250 WORDS)

The aim of the present study was to investigate the applicability of a previously developed method for the analysis of triacylglycerol molecular species to the simultaneous determination of triacylglycerols, diacylglycerols and monoacylglycerols of human very-low-density lipoproteins (VLDL). Ten elderly women were recruited for the study. Blood was obtained in fasting conditions and VLDL were isolated by ultracentrifugation. Neutral lipids were separated by solid-phase extraction and were subsequently injected on a reversed-phase HPLC system, with an elution system composed of acetone in acetonitrile. The method allowed the separation of four monoacylglycerols, 18 diacylglycerols and 24 triacylglycerols, including the resolution of positional isomers of diacylglycerols. Monoacylglycerols were composed of oleic, linoleic, palmitic and stearic acids. The major diacylglycerols were 1,2-dilinoleoyl-glycerol and 1,3-dilinoleoyl-glycerol (14.24+/-1.02 and 17.93+/-1.42%, respectively). The main triacylglycerols quantified were dioleoyl-stearoyl-glycerol (OOS), oleoyl-dipalmitoyl-glycerol (OPP), trilinoleoyl-glycerol (LLL) and linoleoyl-distearoyl-glycerol (LSS), accounting for 11.25+/-2.15, 10.14+/-2.05, 9.35+/-2.30 and 8.56+/-1.56%, respectively. An inverse relationship between polarity and fatty acid disappearance from triacylglycerols (r(2)=0.82, P<0.05) and from diacylglycerols (r(2)=0.93, P<0.01) was discovered. In conclusion, the method allowed, for the first time, the easy, rapid and simultaneous determination in a single chromatogram of triacylglycerol, diacylglycerol and monoacylglycerol molecular species of human VLDL by reversed-phase HPLC.

Guinea pigs were fed isocaloric diets containing 52% (w/w) carbohydrate, either sucrose or starch, to investigate effects of simple vs. complex carbohydrates on plasma VLDL and HDL metabolism. Plasma cholesterol concentrations were not different between dietary groups while plasma triacylglycerol (TAG) and VLDL cholesterol levels were significantly increased in animals fed the sucrose diet (P < 0.05). Hepatic VLDL TAG secretion rates measured following intravenous injection of Triton WR-1339 were not affected by carbohydrate type whereas the rate of apo B secretion was 1.9-fold higher in sucrose fed animals (P < 0.02). Nascent VLDL from the sucrose group contained less TAG per apo B suggesting that the higher plasma TAG in animals fed simple carbohydrates results from increased secretion of VLDL particles with lower TAG content. Sucrose fed animals exhibited higher concentrations of hepatic free cholesterol (P < 0.01) while hepatic TAG levels and acyl CoA:cholesterol acyltransferase (ACAT) activity were not different between groups. Plasma HDL cholesterol concentrations and composition, and plasma lecithin cholesterol acyltransferase (LCAT) activity were not affected by diet yet there was a positive correlation between HDL cholesteryl ester content and LCAT activities (r = 0.70, P < 0.05). Hepatic membranes from the sucrose group had a higher hepatic HDL binding protein number (Bmax) with no changes in the dissociation constant (Kd). These results suggest that at the same carbohydrate energy intake, simple sugars induce modest changes in HDL metabolism while VLDL metabolism is affected at multiple sites, as indicated by the higher concentrations of hepatic cholesterol, dissociation in the synthesis rates of VLDL components, and compositional changes in nascent and mature VLDL.

Studies have generally suggested a positive association between dyslipidemia and chronic kidney disease, but sparse data are available on the relation of lipids and glomerular filtration rate in patients with normal renal function. We investigated the associations of serum lipids, including total, LDL, HDL, VLDL cholesterol, and triglyceride levels with estimated glomerular filtration rate (eGFR) in type 1 diabetic patients. Study included 313 normoalbuminuric type 1 diabetic patients with normal or mild decrease (eGFR>> 60 mL/min per 1.73 m2) renal function and before any interventions with statins, ACE inhibitors or angiotensin II receptor blockers. eGFR was significantly associated with total, LDL, and HDL cholesterol (r = -0.21, -0.18, and -0.17, respectively, for all p < 0.05). Stratifying serum lipids for degree of eGFR, levels of total, LDL, and HDL cholesterol were inversely related to eGFR, but trends were significant only for total (5.1 vs 5.0 and 4.6 mmol/L) and LDL cholesterol (2.9 vs 2.8 and 2.4 mmol/L). We have detected an association between eGFR and lipid abnormalities in type 1 diabetes in early stages. The study was conducted in patients with no therapeutic intervention. This may suggest that lipid abnormalities may play a role in the pathogenesis of renal impairment in type 1 diabetic patients.

BACKGROUND

The impact of the Mediterranean diet (MedDiet) on high-density lipoprotein (HDL) kinetics has not been studied to date. The objective of this study was therefore to investigate the effect of the MedDiet in the absence of changes in body weight on apolipoprotein (apo) A-I kinetic in men with metabolic syndrome (MetS).

METHODS

Twenty-six men with MetS (NCEP-ATP III) were recruited from the general community. In this fixed sequence study, participants' diet was first standardized to a control diet reflecting current averages in macronutrient intake in North American men, with all foods and beverages provided under isoenergetic conditions for 5 weeks. Participants were then fed an isoenergetic MedDiet over a subsequent period of 5 weeks to maintain their weight constant. During the last week of each diet, participants received a single bolus dose of [5,5,5-2H3] L-leucine and fasting blood samples were collected at predetermined time points. ApoA-I kinetic was determined by multicompartmental modeling using isotopic enrichment data over time. Data were analyses using MIXED models.

RESULTS

The response of HDL-cholesterol (C) to MedDiet was heterogeneous, such that there was no mean change compared with the control diet. Plasma apoA-I concentration (-3.9%) and pool size (-5.3%, both P < 0.05) were significantly lower after MedDiet and apoA-I production rate tended to be reduced (-5.7%, P = 0.07) with no change in apoA-I fractional catabolic rate (FCR, -1.6%, P = 0.64). Participants among whom HDL-C concentrations were increased with MedDiet (responders: mean ∆HDL-C: +9.9 ± 3.2%, N = 11) showed significantly greater reductions in apoA-I FCR and in apoB and very-low-density lipoprotein-triglycerides (VLDL-TG) concentrations (all P < 0.04) than those among whom HDL-C levels were reduced after the MedDiet (non-responders: mean ∆HDL-C: -12.0 ± 3.9%, N = 8). Correlation analysis revealed that only variations in apoA-I FCR (r = -0.48, P = 0.01) and in plasma VLDL-TG (r = -0.45, P = 0.03) concentrations were correlated with the individual HDL-C response to the MedDiet.

CONCLUSIONS

Data from this controlled feeding study suggest that the heterogeneous response of HDL-C to MedDiet, in the absence of important weight loss, is primarily related to individual variations in apoA-I FCR and in plasma VLDL-TG concentrations.

Activities of lipogenic enzymes and plasma very low density lipoprotein (VLDL) concentrations were measured in lines of chickens with large differences in food conversion efficiency (FCE) and body fat. Hepatic activities of malate dehydrogenase [EC 1.1.1.40 (MD)] and ATP citrate lyase [EC 4.1.3.8 (CL)] were correlated with the proportion of both abdominal and total body fat (r = 0.50) but were poorly correlated with gain: food ratio. Activities of MD and CL in plasma were low and variable and were not correlated with any other characteristics. Plasma VLDL concentration was significantly correlated with the proportion of abdominal and total body fat (r = 0.59), and gain: food ratio (r = 0.36).

OBJECTIVE

To determine the effect of cigarette smoking on the activity of cholesteryl ester transfer protein (CETP) and high-density (HDL), low-density (LDL), and very-low-density (VLDL) lipoproteins in insulin-dependent diabetic (IDDM) men with microvascular complications.

METHODS

We performed a case-control study in a referral-based diabetes clinic on a sequential sample of 9 cigarette-smoking and 12 nonsmoking IDDM men with microvascular complications and 12 nonsmoking control men. CETP activity was determined in each serum with an isotope assay with exogenous cholesteryl ester-labeled LDL and HDL. The method is independent of the endogenous lipoprotein present in serum.

RESULTS

The HDL-cholesterol (VLDL and LDL) ratio was lower in the smoking diabetic men than in the other groups (P less than 0.05 vs. the nonsmoking diabetic men and P less than 0.01 vs. the control subjects). CETP activity was 70% higher in the smoking diabetic men than in the control subjects (P less than 0.01) and 30% higher than in the nonsmoking diabetic men (P less than 0.05). The HDL-cholesterol (VLDL and LDL) ratio and the apolipoprotein A-I-B ratio were inversely correlated to CETP activity in the diabetic patients (r = -0.52, P less than 0.02 and r = -0.45, P less than 0.05, respectively).

CONCLUSIONS

CETP activity is increased in cigarette-smoking IDDM men with microvascular complications. High CETP activity may contribute to the unfavorable lipoprotein profile in these patients.

A wide variety of cholesteryl ester-rich apoB-containing lipoproteins undergo an order-disorder transition in the cholesteryl ester core at approximately normal body temperature. The transition occurs over several degrees C with the mid-point being as high as 57 degrees C in some cholesterol-fed animals. The transition mid-point of normal human low density lipoprotein (LDL) appears to vary from as low as 26 degrees C to about body temperature. However, to screen a large population of patients at risk for atheroscerlotic cardiovascular disease (ACD), a rapid method for determining the transition temperature of LDL is needed. Since apoB-containing lipoproteins (VLDL and LDL) are readily precipitated from plasma by dextran sulfate and magnesium sulfate, we have studied the thermal properties of this precipitate using differential scanning calorimetry (DSC). The VLDL-LDL precipitate undergoes a reversible thermal transition similar in transition temperature and enthalpy to the cholesteryl ester transition of isolated pure LDL. The transition is seen with the precipitate from VLDL-free plasma, but no transition is seen when VLDL and LDL have been removed. Cholesteryl ester-rich apoB containing lipoproteins were isolated from a variety of sources (man, cholesterol-fed monkeys, and rabbits) and their transition temperatures compared with the apoB-containing lipoprotein precipitates from the same source. The mid-point of individual transitions varied over a wide range (17-57 degrees C) and the correlation between the pure lipoprotein and the plasma precipitate was strong (r = 0.98, P < 0.001. Thus, DSC of the plasma apoB precipitate may be used as a rapid method of determining the cholesteryl ester transition of LDL and other apoB-containing lipoproteins.-Waugh, D. A., and D. M. Small. Rapid method for determining cholesteryl ester transitions of apoB-containing lipoproteins.

To evaluate factors regulating the concentrations of plasma low density lipoproteins (LDL), apolipoprotein B metabolism was studied in nine Pima Indians (25 +/- 2 yr, 191 +/- 20% ideal wt) with low LDL cholesterol (77 +/- 7 mg/dl) and apoB (60 +/- 4 mg/dl) and in eight age- and weight-matched Caucasians with similar very low density lipoprotein (VLDL) concentrations, but higher LDL (cholesterol = 104 +/- 18; apoB = 82 +/- 10; P less than 0.05). Subjects received autologous 131I-labeled VLDL and 125I-labeled LDL, and specific activities of VLDL-apoB, intermediate density lipoprotein (IDL)-apoB, and LDL-apoB were analyzed using a multicompartmental model. Synthesis of LDL-apoB was similar (1224 +/- 87 mg/d in Pimas vs 1218 +/- 118 mg/d in Caucasians) but in Pimas the fractional catabolic rate (FCR) for LDL-apoB was higher (0.48 +/- 0.02 vs 0.39 +/- 0.04 d-1, P less than 0.05). In the Pimas, a much higher proportion of VLDL-apoB was catabolized without conversion to LDL (47 +/- 3 vs 30 +/- 5%, P less than 0.01). When all subjects were considered together, LDL-apoB concentrations were negatively correlated with both FCR for LDL-apoB (r = -0.79, P less than 0.0001) and the non-LDL pathway (r = -0.43, P less than 0.05). Also, the direct removal (non-LDL) path was correlated with VLDL-apoB production (r = 0.49, P = 0.03), and the direct removal pathway and FCR for LDL-apoB were correlated (r = 0.49, P = 0.03). In conclusion, plasma LDL appear to be regulated by both the catabolism of LDL and the extent of metabolism of VLDL without conversion to LDL; both of these processes may be mediated by the apoB/E receptor, and appear to increase in response to increasing VLDL production.

OBJECTIVE

Etiopathogenesis of cryptogenic cirrhosis (CC) is not yet well established. Up to 20% of non-alcoholic fatty liver disease (NAFLD) may progress to cirrhosis, mostly termed as cryptogenic. Insulin resistance and altered metabolic parameters form a major pathogenic link between NAFLD and CC. CC may thus be actually a metabolic liver disease.

METHODS

Thirty-four patients of CC and 32 patients having cirrhosis due to chronic hepatitis B (Hep B) were assessed in a cross-sectional study in a tertiary hospital for insulin resistance, % β-cell activity, obesity indices, plasma glucose, lipid profiles, and many other parameters.

RESULTS

CC patients had higher homeostasis model assessment (HOMA)-IR compared to Hep B group (P = 0.000016). A positive correlation between IR values and Child-Pugh score among CC patients was found ("r" = 0.87; P < 0.00001). Out of 34 CC patients, 15 (44.1%) had obesity contrary to 6 (18.8%) in the control group (P = 0.0022). Differences were observed in subcutaneous fat (P = 0.0022), intra-abdominal fat (P = 0.0055), waist circumference (P = 0.014), and percentage body fat (P = 0.047) between the two groups. Significant differences were observed in the levels of triglyceride, total cholesterol, and very low density lipoprotein (VLDL).

CONCLUSIONS

Most of the CC patients showed significantly higher prevalence of HOMA-IR, obesity indices, and various parameters of "lipotoxicity" and metabolic syndrome, suggesting that CC may be the long-term consequence of a type of "metabolic liver disease." Further studies are required to evaluate the role of therapeutic interventions to enhance insulin sensitivity in such patients.

BACKGROUND

Plasma and hepatic lipid abnormalities are frequent in hepatitis C infected individuals.

METHODS

Plasma lipid and medical records profiles were prospectively obtained in 130 consecutive individuals seen by a single hepatologist in a university liver disease clinic. The relationships between viral load, genotype, plasma lipid fractions, HDL, LDL particle number and particle size were examined.

RESULTS

Of 130 individuals studied, 74 had hepatitis C while 15 had NAFLD/NASH and 30 had alcohol related liver disease. The LDL particle number and LDL-C levels did not differ between those with and without hepatitis C although the number of small LDL particles was greater in those with hepatitis C infection. The HDL-C and total cholesterol levels were greater in those without hepatitis C than those with hepatitis C (P = 0.009). In contrast, the serum triglyceride level was greater in the hepatitis C viral group (P = 0.013). Importantly, the hepatitis C viral load regardless of the genotype correlated directly with the triglyceride and VLDL levels with r values of 0.73 and 0.84, respectively.

CONCLUSIONS

There are: (1) important differences in lipid classes, number and the size of lipid particles exist between hepatitis C virus infected and noninfected liver disease groups, (2) the serum total triglyceride and the LDL levels correlate significantly with the hepatitis C viral load and, (3) Serum triglyceride level may play an important role in viral replication. These data further suggest that therapies directed at lowering plasma triglyceride levels may enhance the efficacy of current antiviral treatment regimens.

BACKGROUND

Fourier-transform infrared (FT-IR) spectroscopy is a simple and reagent-free physicochemical analysis method, and is a potential alternative to more time-consuming and labor-intensive procedures. In this study, we aimed to use FT-IR spectroscopy to determine serum concentrations of chylomicron-triglyceride (TG) and very low density lipoprotein (VLDL)-TG.

METHODS

We analyzed a chylomicron fraction and VLDL fraction, which had been obtained by ultracentrifugation, to search for wavelengths to designate to each fraction. Then, partial least square (PLS) calibrations were developed using a training set of samples, for which TG concentrations had been determined by conventional procedures. Validation was conducted with another set of samples using the PLS model to predict serum TG concentrations on the basis of the samples' IR spectra. We analyzed a total of 150 samples.

RESULTS

Serum concentrations of chylomicron-TG and VLDL-TG estimated by FT-IR spectroscopy agreed well with those obtained by the reference method (r=0.97 for both lipoprotein fractions). FT-IR spectrometric analysis required 15mul of serum and was completed within 1min.

CONCLUSIONS

Serum chylomicron-TG and VLDL-TG concentrations can be determined with FT-IR spectroscopy. This rapid and simple test may have a great impact on the management of patients with dyslipidemia.

Beta-thromboglobulin (BTG) is a platelet-specific release product. Plasma BTG was significantly increased (p less than 0.01) in 50-year-old, untreated essential hypertensive men (1.22 +/- 0.13 nmol/L, n = 39, mean +/- SE) compared to 50-year-old, healthy normotensive control men (0.82 +/- 0.07 nmol/L, n = 31). Plasma BTG in the hypertensive group correlated significantly with the total serum cholesterol concentration (r = 0.47, p less than 0.01) and with the atherogenic cholesterol fractions low-density lipoprotein (LDL) and very low-density lipoprotein (VLDL) cholesterol (r = 0.50, p less than 0.01). In the normotensive group, no significant correlation was observed between plasma BTG and total serum cholesterol (r = 0.14) or between plasma BTG and LDL + VLDL cholesterol (r = 0.08). Neither was any significant correlation found between plasma BTG and serum high-density lipoprotein (HDL) cholesterol or total triglycerides in either group. Thus, middle-aged men with untreated essential hypertension have an increased blood platelet release reaction related to their concentrations of atherogenic blood lipids. This relationship may be of pathogenetic importance for atherogenesis in hypertension.

50 year old men with moderate, essential hypertension (n = 39) were compared to normotensive males of similar age (n = 31). The hypertensive men were heavier (10 kg in average, p less than 0.01), and had a higher pulse rate (5 beats per minute (p less than 0.05). Plasma beta-thromboglobulin, a marker of platelet release reaction, was 49% higher in the hypertensive group (p less than 0.01). Total cholesterol, LDL + VLDL cholesterol and serum triglycerides were not significantly different between the groups. In the hypertensive group, plasma beta-thromboglobulin concentration correlated significantly with total cholesterol (r = 0.47, p less than 0.01) as well as with LDL + VLDL cholesterol (r = 0.50, p less than 0.01). In the normotensive group no such correlation was found. The results suggest activation of platelets in hypertension, and suggest that in hypertension, even a normal cholesterol concentration may influence platelet function.

OBJECTIVE

The influence of different regional adipose tissue (AT) compartments on insulin resistance and dyslipidaemia may account for variations in risk of diabetes and cardiovascular disease. The purpose of this study was to examine the association of intraperitoneal and posterior subcutaneous abdominal AT with very-low-density lipoprotein apolipoprotein B-100 (VLDL-apoB) kinetics in overweight/obese men.

METHODS

Intraperitoneal, anterior subcutaneous and posterior subcutaneous abdominal AT mass (IPATM, ASAATM and PSAATM respectively) were quantified in 51 overweight/obese men using magnetic resonance imaging. Hepatic secretion of VLDL-apoB was measured using an intravenous infusion of 1-[13C]-leucine. Isotopic enrichment of VLDL-apoB was measured using gas chromatography mass spectrometry and a multicompartmental model used to estimate VLDL-apoB metabolic parameters. Insulin resistance was estimated by homeostasis model assessment (HOMA) score.

RESULTS

In univariate analysis, IPATM, ASAATM and PSAATM were significantly associated with HOMA score (r = 0.554, 0.425 and 0.440 respectively; p < 0.01). Intraperitoneal abdominal AT mass was also associated with plasma triglycerides (r = 0.292, p < 0.05), VLDL-apoB concentrations (r = 0.407, p < 0.01) and VLDL-apoB secretion (r = 0.390, p < 0.05). Intraperitoneal abdominal AT mass remained significantly associated with VLDL-apoB secretion (r = 0.344, p < 0.05) and HOMA score (r = 0.368, p < 0.01) after adjusting for total body fat. In multiple regression analysis including IPATM, non-esterified fatty acids and age, IPATM was the best predictor of VLDL-apoB secretion (R2 = 17%, p < 0.01) and HOMA score (R2 = 32%, p < 0.001). None of the fat compartments were significantly associated with VLDL-apoB catabolism.

CONCLUSIONS

In overweight/obese men the intraperitoneal AT mass is a better predictor of VLDL-apoB secretion and insulin resistance than either posterior or anterior subcutaneous abdominal AT mass.

Post-prandial (pp) hypertriglyceridaemia (HTG) has an important role in the development of atherosclerosis in Type 2 diabetes. Impaired glucose tolerance (IGT) is associated with an increased risk of atherosclerosis and increased level of fasting triglycerides (TG). The aim of this study was to analyse pp HTG and the composition of TG-rich lipoproteins in carefully selected subjects with IGT in comparison to controls with normal glucose tolerance (NGT). Fifteen men with IGT and 27 men with NGT, aged 44 to 70 yr, were examined. All study participants were non-smokers and had fasting TG <4.6 mmol/l. The subjects underwent an oral glucose tolerance test (75 g glucose) and a lipid-glucose tolerance test (LGTT; 92 g fat, 126 g carbohydrate), that allowed the assessment of lipid and glucose tolerance in one test. HbA1C, plasma glucose and lipids were measured by routine methods. Lipoprotein subfraction analysis of VLDL (VLDLVLDLr after the LGTT using a density gradient ultracentrifugation with a subsequent compositional analysis. No significant difference was found either for fasting or pp TG, or for area under curve (AUC) -TG (12.21 +/- 4.27 mmol/l x 6 hr vs 13.95 +/- 6.74 mmol/l x 6 hr; p>0.05) between the IGT and NGT. A highly significant correlation was found between the fasting TG and the AUC-TG (r=0.925; p<0.01). To avoid bias by differences in fasting plasma TG known to affect lipid tolerance we investigated 11 matched pairs for fasting TG. Also, the matched-pairs evaluation pp TG course did not differ significantly from the IGT and NGT. No significant difference for fasting or pp levels of VLDLVLDLr for the TG content of chylomicron, VLDLVLDLr the percentage of TG in VLDLVLDLroup. In conclusion, IGT subjects with a similar level of fasting TG do not exhibit lipid intolerance. Our data suggest that glucose intolerance should precede lipid intolerance.

We evaluated a new ready to use liquid assay for the homogeneous determination of HDL-cholesterol (HDL-C; Merck, Darmstadt, Germany) in comparison to phosphotungstic acid precipitation and a homogeneous assay, based on sulfated alpha-cyclodextrin and polyethylene glycol-modified enzymes (Roche Diagnostics/Boehringer Mannheim, Germany). The new liquid homogeneous HDL-C assay had inter-assay coefficients' of variation of less than 2.1%. The method is linear up to at least 3.11 mmol/I HDL-C, but even at 4.40 mmol/I the deviation from the expected value is less than 5%. Spinking experiments with low density lipoproteins and very low density lipoproteins proved that the new assay was specific for high density lipoproteins up to cholesterol associated with low density lipoproteins (LDL-C) and very low density lipoproteins (VLDL)-triglyceride concentrations of 18.13 and 22.60 mmol/l, respectively. Free fatty acids above 2mmol/l did not interfere. Icteric samples with bilirubin concentrations between 170 and 400 micromol/l did not show any systematic deviation compared to the precipitation procedure. In addition, serum hemoglobin concentrations up to 7.0 mmol/l and ascorbic acid up to 3000 micromol/l did not interfere with the HDL-C assay. An intermethod comparison including 120 samples revealed good agreement of the liquid HDL-C assay and the precipitation procedure (y = 0.943x + 0.074 mmol/l; r = 0.992). The new homogeneous HDL-C assay is thus precise, comparable and robust. Due to its ease of handling this assay will significantly facilitate attempts to include the differentiation between HDL-C and LDL-C in the routine screening for cardiovascular risk factors and in the monitoring of lipid lowering therapy.

BACKGROUND

There are conflicting reports of plasma lipoprotein lipid content in dogs with diabetes mellitus (DM).

OBJECTIVE

To determine lipoprotein lipid content of plasma of dogs with DM by spectrophotometry and ultracentrifugation; to compare lipoprotein lipid content in diabetic and healthy dogs; and to quantify apolipoprotein B-100 (ApoB) in dogs with DM.

METHODS

22 dogs with DM and 9 healthy dogs.

METHODS

Cross-sectional study. Triglyceride (TG), total cholesterol (TC), and high-density lipoprotein cholesterol (HDL-C) concentrations were measured by spectrophotometry. Very low-density lipoprotein cholesterol (VLDL-C) and low-density lipoprotein cholesterol (LDL-C) concentrations were calculated after ultracentrifugation. Non-HDL-C cholesterol was calculated by subtracting HDL-C from TC. ApoB was quantified by ELISA. The Mann-Whitney test was used for comparison of median lipoprotein concentrations, and Spearman's correlation was used to assess associations between ApoB and lipoprotein fractions.

RESULTS

All values are reported in mg/dL. Median TG (122), TC (343.5), HDL-C, (200), VLDL-C, (27) LDL-C (68), non-HDL-C (114), and ApoB (320) were significantly higher in dogs with DM, compared to healthy dogs (57, 197, 168, 12, 16, 31, and 258, respectively, P-values 0.0079, <0.001, 0.029, 0.011, <0.001, <0.001, 0.025, respectively). A significant association was found between ApoB and LDL-C (Spearman's rho = 0.41, P = 0.022) and between ApoB and non-HDL-C (Spearman's rho = 0.40, P = 0.027).

CONCLUSIONS

Dyslipidemia of dogs with DM is characterized by pronounced increases in LDL-C and non-HDL-C concentrations, although all lipoprotein fractions are significantly increased. Knowledge of specific lipoprotein fraction alterations in dogs with DM can enhance treatment options for diabetic dyslipidemia in dogs.

The concentrations and lipoprotein distributions of apolipoprotein E (apoE) in normal human umbilical cord blood plasma were determined. The mean plasma apoE level of 95 neonates was considerably higher than that of 49 normal adults (58.1 vs 35.8 micrograms/ml). This elevation of apoE levels was in striking contrast to the lower than adult levels of cholesterol (72 mg/dl vs 185 mg/dl), triglyceride (37.8 mg/dl vs 97.6 mg/dl), and LDL cholesterol (25 mg/dl vs 110 mg/dl) in neonatal plasma. For the group of 95 neonates, the plasma apoE concentration correlated significantly with total plasma cholesterol concentration (r = 0.60), with LDL cholesterol concentration (r = 0.27) and with HDL cholesterol concentration (r = 0.50). Among the neonates, 87% of plasma apoE was associated with a less dense subfraction of high density lipoprotein compared to a mean of 58% for 30 normal adults. Thus, for neonates, despite hypolipidemia, the absolute concentration of apoE in HDL (50 micrograms/ml) was 2.5 times that of adults (20 micrograms/ml). We speculate that the very low level of neonatal VLDL, providing limited substrate for lipolysis, may result in retarded removal of apoE from plasma and the observed high level of apoE in neonatal HDL. We hypothesize that in the fetus and neonate, as has been demonstrated in abetalipoproteinemia, apoE-rich HDL may functionally substitute for LDL in delivering cholesterol to cells.

Bile salts (BS) have been shown to suppress the secretion of very-low-density lipoprotein-triglyceride (VLDL-TG) in rat and human hepatocytes in vitro. In the present study, we investigated whether the transhepatic BS flux affects VLDL-TG concentration and hepatic VLDL-TG secretion in vivo. In rats, the transhepatic BS flux was quantitatively manipulated by 1-week chronic bile diversion (BD), followed by intraduodenal infusion with taurocholate (TC) or saline for 6 h. In mice, the transhepatic BS flux was manipulated by a 3-week dietary supplementation with TC (0.5 wt.%) or cholestyramine (2 wt.%). In rats, BD followed by saline or TC infusion did not affect plasma triacylglycerol (TG) concentration, hepatic TG production rate or VLDL lipid composition, compared to control rats. In mice supplemented for 3 weeks with TC or cholestyramine, the transhepatic BS flux was increased by 335% and decreased by 48%, respectively, compared to controls. Among the three experimental groups of mice, an inverse relationship between transhepatic BS flux and either plasma TG concentration (R(2)=0.89) or VLDL-TG production rate (R(2)=0.87) was observed, but differences were relatively small. Present data support the concept that BS can reduce VLDL-TG concentration and inhibit hepatic TG secretion in vivo; however, this occurs only at supraphysiological transhepatic BS fluxes in mice.