Increased esterification of cholesterol and transfer of cholesteryl ester to apo B-containing lipoproteins in Type 2 diabetes: relationship to serum lipoproteins A-I and A-II

Altered Distribution of Unesterified Cholesterol among Lipoprotein Subfractions of Patients with Diabetes Mellitus Type 2

Biomarkers are important tools to improve the early detection of patients at high risk for developing diabetes as well as the stratification of diabetic patients towards risks of complications. In addition to clinical variables, we analyzed 155 metabolic parameters in plasma samples of 51 healthy volunteers and 66 patients with diabetes using nuclear magnetic resonance (NMR) spectrometry. Upon elastic net analysis with lasso regression, we confirmed the independent associations of diabetes with branched-chain amino acids and lactate (both positive) as well as linoleic acid in plasma and HDL diameter (both inverse). In addition, we found the presence of diabetes independently associated with lower concentrations of free cholesterol in plasma but higher concentrations of free cholesterol in small HDL. Compared to plasmas of non-diabetic controls, plasmas of diabetic subjects contained lower absolute and relative concentrations of free cholesterol in all LDL and HDL subclasses except small HDL but higher absolute and relative concentrations of free cholesterol in all VLDL subclasses (except very small VLDL). These disbalances may reflect disturbances in the transfer of free cholesterol from VLDL to HDL during lipolysis and in the transfer of cell-derived cholesterol from small HDL via larger HDL to LDL.

Progressive, Qualitative, and Quantitative Alterations in HDL Lipidome from Healthy Subjects to Patients with Prediabetes and Type 2 Diabetes

Prediabetes is a clinically silent, insulin-resistant state with increased risk for the development of type 2 diabetes (T2D) and cardiovascular disease (CVD). Since glucose homeostasis and lipid metabolism are highly intersected and interrelated, an in-depth characterization of qualitative and quantitative abnormalities in lipoproteins could unravel the metabolic pathways underlying the progression of prediabetes to T2D and also the proneness of these patients to developing premature atherosclerosis. We investigated the HDL lipidome in 40 patients with prediabetes and compared it to that of 40 normoglycemic individuals and 40 patients with established T2D using Nuclear Magnetic Resonance (NMR) spectroscopy. Patients with prediabetes presented significant qualitative and quantitative alterations, potentially atherogenic, in HDL lipidome compared to normoglycemic characterized by higher percentages of free cholesterol and triglycerides, whereas phospholipids were lower. Glycerophospholipids and ether glycerolipids were significantly lower in prediabetic compared to normoglycemic individuals, whereas sphingolipids were significantly higher. In prediabetes, lipids were esterified with saturated rather than unsaturated fatty acids. These changes are qualitatively similar, but quantitatively milder, than those found in patients with T2D. We conclude that the detailed characterization of the HDL lipid profile bears a potential to identify patients with subtle (but still proatherogenic) abnormalities who are at high risk for development of T2D and CVD.

High level of serum cholesteryl ester transfer protein in active hepatitis C virus infection

AIM: To determine the significance of cholesteryl ester transfer protein (CETP) in lipoprotein abnormalities in chronic hepatitis C virus (HCV) infection.

METHODS: We evaluated the significance of the serum concentration of CETP in 110 Japanese patients with chronic HCV infection. Fifty-five patients had active HCV infection, and HCV eradication had been achieved in 55. The role of CETP in serum lipoprotein abnormalities, specifically, in triglyceride (TG) concentrations in the four major classes of lipoproteins, was investigated using Pearson correlations in conjunction with multiple regression analysis and compared them between those with active HCV infection and those in whom eradication had been achieved.

RESULTS: The serum CETP levels of patients with active HCV infection were significantly higher than those of patients in whom HCV eradication was achieved (mean ± SD, 2.84 ± 0.69 μg/mL vs 2.40 ± 1.00 μg/mL, P = 0.008). In multiple regression analysis, HCV infection status (active or eradicated) was an independent factor significantly associated with the serum CETP level. TG concentrations in low-density lipoprotein (mean ± SD, 36.25 ± 15.28 μg/mL vs 28.14 ± 9.94 μg/mL, P = 0.001) and high-density lipoprotein (HDL) (mean ± SD, 25.9 ± 7.34 μg/mL vs 17.17 ± 4.82 μg/mL, P < 0.001) were significantly higher in patients with active HCV infection than in those in whom HCV eradication was achieved. The CETP level was strongly correlated with HDL-TG in patients with active HCV infection (R = 0.557, P < 0.001), whereas CETP was not correlated with HDL-TG in patients in whom HCV eradication was achieved (R = -0.079, P = 0.56).

CONCLUSION: Our results indicate that CETP plays a role in abnormalities of lipoprotein metabolism in patients with chronic HCV infection.

HbA1c negatively correlates with LCAT activity in type 2 diabetes

AIMS

Abnormal high-density lipoproteins (HDL) metabolism is a major cardiovascular risk factor in type 2 diabetes mellitus (DM2). Lecithin:cholesterol acyltransferase (LCAT) increases HDL size by transferring 2-acyl groups from lecithin or phosphatidylethanolamine to unesterified cholesterol. The purpose of this study was to determine the independent correlates of LCAT activity in DM2 patients.

METHODS

A total of 45 (male: 20) consecutive adult DM2 patients aging 50.0+/-7.0 years (range: 40-64 years) with a median diabetes duration of 4 years (range: 2-18) were studied. Exclusion criteria were: smoking, positive history of cardiovascular, thyroid, renal or liver disease, pregnancy, treatment with metformin, insulin, lipid lowering drugs, angiotensin-converting enzyme inhibitors, aspirin or antioxidant supplements. Univariate and multivariate analyses were performed.

RESULTS

From a comprehensive list of variables studied, only HbA1c (rho=-0.951) and oxidized LDL (rho=-0.779) had statistically significant correlation with LCAT activity (p<0.001). These two variables were themselves strongly correlated to each other (rho=0.809, p<0.001). To eliminate potential confounding effects, we performed multivariate analysis, where HbA1c emerged as a strong independent predictor of LCAT activity (adjusted OR=-0.928, p<0.001).

CONCLUSIONS

Glycemia-induced glycation of HDL decreases LCAT activity. The fact that HbA1c is an accurate measure of glycation and can therefore reflect glycated HDL levels explains the association found in the present study. In conclusion, HbA1c provides an easy-to-assess, accurate measure of LCAT activity in DM2.

Effect of postprandial lipaemia and Taq 1B polymorphism of the cholesteryl ester transfer protein (CETP) gene on CETP mass, activity, associated lipoproteins and plasma lipids

A large number of studies in recent years have investigated the effects of hyperlipidaemias and diabetes on cholesteryl ester transfer protein (CETP) on neutral lipid transfer activity and plasma lipids. There has been an ongoing debate as to whether CETP is pro- or anti-atherogenic as it provides a mechanism for the transfer of cholesterol from the cardioprotective HDL subfraction to the potentially atherogenic LDL subfraction. This study was designed to investigate whether there was significant variability of CETP mass and activity in a large normolipidaemic population and whether there is an association between CETP and plasma lipoprotein composition. The presence of a known polymorphism of CETP gene (Taq 1B) was investigated to see if there was any association between this polymorphism and CETP mass and activity, and plasma lipids. There was significant (P < 0·0001) increase in CETP mass and activity in plasma postprandially at 6 h. Using multiple stepwise regression analysis there was significant association with fasting CETP mass and activity (β = 0·055; P = 0·002) and triacylglycerol-rich lipoprotein (β = 0·013; P = 0·005) and postprandial CETP mass (β = 0·254; P = 0·007). Repeated-measures analysis showed a strong association between the absence of Taq 1B polymorphism and low CETP mass and elevated HDL- and HDL2-cholesterol and HDL-phospholipid concentrations than did those who were homozygous or heterozygous for the presence of the restriction site.

Serum cholesteryl ester transfer protein concentrations are associated with serum levels of total cholesterol, beta-lipoprotein and apoproteins in patients with type 2 diabetes mellitus

OBJECTIVE

To investigate the role of serum cholesterol ester transfer protein (CETP) and the metabolism of various lipids including apoproteins in patients with type 2 diabetes.

MATERIALS AND METHODS

The relationships between serum concentrations of CETP and various lipids and apoproteins were investigated in 193 patients with type 2 diabetes mellitus and 68 age-matched healthy subjects. Serum CETP concentrations were measured by an enzyme-linked immunosorbent assay.

RESULTS

Serum CETP values were lower in diabetic patients than in healthy controls (p < 0.01). Female diabetic patients had significantly higher CETP concentrations than male patients. Serum CETP concentrations exhibited a significant positive correlation with serum concentrations of cholesterol (TC) and beta-lipoproteins in diabetic patients (r = 0.485, p = 0.013). Patients with relatively high serum concentrations of high-density lipoprotein cholesterol (HDL-C) tended to have much lower CETP concentrations than patients with lower HDL-C concentrations. Serum CETP concentrations showed significant positive correlations with those of apoproteins B (Apo B; r = 0.384, p = 0.024) and E (Apo E; r = 0.341, p = 0.035).

CONCLUSION

The data indicate that serum CETP is closely involved in the metabolism of TC, beta-lipoprotein, Apo B and Apo E in type 2 diabetic patients.

Kinetics of prebeta1 HDL and alphaHDL in type II diabetic patients

BACKGROUND

The aim of this study was to analyze the recycling of high density lipoprotein (HDL) in six type II diabetic patients compared with six control subjects by endogenous labelling of apolipoprotein A-I (Apo A-I) with stable isotope Apo A.

MATERIALS AND METHODS

The -I-HDL kinetics were performed by infusion of (5.5.5-(2)H3)-leucine for 14 h. The prebeta1 and alphaHDL were separated by gel filtration fast protein liquid chromatrography system (FPLC). Kinetics of isotopic enrichment of Apo A-I were analyzed with a multi-compartmental model software (SAAM II, SAAM Institute, Seattle, WA).

RESULTS

Plasma Apo A-I concentration was decreased in patients with type II diabetes as a result of a decrease in Apo A-I-alphaHDL (P < 0.05). Diabetic patients were also characterized by an increased relative contribution of Apo A-I in prebeta1 HDL (18.3 +/- 2.8% vs 11.9 +/- 3.7%, P < 0.01). The synthetic rate of prebeta1 HDL was slightly increased in diabetic patients compared with control (NS) and an increase of recycling rate of alpha to prebeta1 HDL was observed (11.67 +/- 3.14 d(-1) vs 7.09 +/- 4.51 d(-1), P < 0.05). The clearance rate of Apo A-I was higher in diabetic patients (P < 0.05 for Apo A-I-prebeta1 HDL and P < 0.005 for Apo A-I-alphaHDL).

CONCLUSION

This study suggests that the usual increase in prebeta1 HDL in type II diabetic patients is mainly related to an increased conversion rate of alpha to prebeta1 HDL.

Pharmacological modulation of cholesteryl ester transfer protein, a new therapeutic target in atherogenic dyslipidemia

In mediating the transfer of cholesteryl esters (CE) from antiatherogenic high density lipoprotein (HDL) to proatherogenic apolipoprotein (apo)-B-containing lipoprotein particles (including very low density lipoprotein [VLDL], VLDL remnants, intermediate density lipoprotein [IDL], and low density lipoprotein [LDL]), the CE transfer protein (CETP) plays a critical role not only in the reverse cholesterol transport (RCT) pathway but also in the intravascular remodeling and recycling of HDL particles. Dyslipidemic states associated with premature atherosclerotic disease and high cardiovascular risk are characterized by a disequilibrium due to an excess of circulating concentrations of atherogenic lipoproteins relative to those of atheroprotective HDL, thereby favoring arterial cholesterol deposition and enhanced atherogenesis. In such states, CETP activity is elevated and contributes significantly to the cholesterol burden in atherogenic apoB-containing lipoproteins. In reducing the numbers of acceptor particles for HDL-derived CE, both statins (VLDL, VLDL remnants, IDL, and LDL) and fibrates (primarily VLDL and VLDL remnants) act to attenuate potentially proatherogenic CETP activity in dyslipidemic states; simultaneously, CE are preferentially retained in HDL and thereby contribute to elevation in HDL-cholesterol content. Mutations in the CETP gene associated with CETP deficiency are characterized by high HDL-cholesterol levels (>60 mg/dL) and reduced cardiovascular risk. Such findings are consistent with studies of pharmacologically mediated inhibition of CETP in the rabbit, which argue strongly in favor of CETP inhibition as a valid therapeutic approach to delay atherogenesis. Consequently, new organic inhibitors of CETP are under development and present a potent tool for elevation of HDL in dyslipidemias involving low HDL levels and premature coronary artery disease, such as the dyslipidemia of type II diabetes and the metabolic syndrome. The results of clinical trials to evaluate the impact of CETP inhibition on premature atherosclerosis are eagerly awaited.

Alterations in high-density lipoprotein metabolism and reverse cholesterol transport in insulin resistance and type 2 diabetes mellitus: role of lipolytic enzymes, lecithin:cholesterol acyltransferase and lipid transfer proteins

Insulin resistance and type 2 diabetes mellitus are generally accompanied by low HDL cholesterol and high plasma triglycerides, which are major cardiovascular risk factors. This review describes abnormalities in HDL metabolism and reverse cholesterol transport, i.e. the transport of cholesterol from peripheral cells back to the liver for metabolism and biliary excretion, in insulin resistance and type 2 diabetes mellitus. Several enzymes including lipoprotein lipase (LPL), hepatic lipase (HL) and lecithin: cholesterol acyltransferase (LCAT), as well as cholesteryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP), participate in HDL metabolism and remodelling. Lipoprotein lipase hydrolyses lipoprotein triglycerides, thus providing lipids for HDL formation. Hepatic lipase reduces HDL particle size by hydrolysing its triglycerides and phospholipids. A decreased postheparin plasma LPL/HL ratio is a determinant of low HDL2 cholesterol in insulin resistance. The esterification of free cholesterol by LCAT increases HDL particle size. Plasma cholesterol esterification is unaltered or increased in type 2 diabetes mellitus, probably depending on the extent of triglyceride elevation. Subsequent CETP action results in transfer of cholesteryl esters from HDL towards triglyceride-rich lipoproteins, and is involved in decreasing HDL size. An increased plasma cholesteryl ester transfer is frequently observed in insulin-resistant conditions, and is considered to be a determinant of low HDL cholesterol. Phospholipid transfer protein generates small pre beta-HDL particles that are initial acceptors of cell-derived cholesterol. Its activity in plasma is elevated in insulin resistance and type 2 diabetes mellitus in association with high plasma triglycerides and obesity. In insulin resistance, the ability of plasma to promote cellular cholesterol efflux may be maintained consequent to increases in PLTP activity and pre beta-HDL. However, cellular cholesterol efflux to diabetic plasma is probably impaired. Besides, cellular abnormalities that are in part related to impaired actions of ATP binding cassette transporter 1 and scavenger receptor class B type I are likely to result in diminished cellular cholesterol efflux in the diabetic state. Whether hepatic metabolism of HDL-derived cholesterol and subsequent hepatobiliary transport is altered in insulin resistance and type 2 diabetes mellitus is unknown. Specific CETP inhibitors have been developed that exert major HDL cholesterol-raising effects in humans and retard atherosclerosis in animals. As an increased CETP-mediated cholesteryl ester transfer represents a plausible metabolic intermediate between high triglycerides and low HDL cholesterol, studies are warranted to evaluate the effects of these agents in insulin resistance- and diabetes-associated dyslipidaemia.

Atherogenic role of elevated CE transfer from HDL to VLDL(1) and dense LDL in type 2 diabetes : impact of the degree of triglyceridemia

Plasma cholesteryl ester transfer protein (CETP) facilitates intravascular lipoprotein remodeling by promoting the heteroexchange of neutral lipids. To determine whether the degree of triglyceridemia may influence the CETP-mediated redistribution of HDL CE between atherogenic plasma lipoprotein particles in type 2 diabetes, we evaluated CE mass transfer from HDL to apoB-containing lipoprotein acceptors in the plasma of type 2 diabetes subjects (n=38). In parallel, we investigated the potential relationship between CE transfer and the appearance of an atherogenic dense LDL profile. The diabetic population was divided into 3 subgroups according to fasting plasma triglyceride (TG) levels: group 1 (G1), TG<100 mg/dL; group 2 (G2), 100<TG<200 mg/dL; and group 3 (G3), TG>200 mg/dL. Type 2 diabetes patients displayed an asymmetrical LDL profile in which the dense LDL subfractions predominated. Plasma levels of dense LDL subfractions were strongly positively correlated with those of plasma triglyceride (TG) (r=0.471; P:=0.0003). The rate of CE mass transfer from HDL to apoB-containing lipoproteins was significantly enhanced in G3 compared with G2 or G1 (46.2+/-8.1, 33.6+/-5.3, and 28.2+/-2.7 microg CE transferred. h(-1). mL(-1) in G3, G2, and G1, respectively; P:<0.0001 G3 versus G1, P:=0.0001 G2 versus G1, and P:=0.02 G2 versus G3). The relative capacities of VLDL and LDL to act as acceptors of CE from HDL were distinct between type 2 diabetes subgroups. LDL particles represented the preferential CE acceptor in G1 and accounted for 74% of total CE transferred from HDL. By contrast, in G2 and G3, TG-rich lipoprotein subfractions accounted for 47% and 72% of total CE transferred from HDL, respectively. Moreover, the relative proportion of CE transferred from HDL to VLDL(1) in type 2 diabetes patients increased progressively with increase in plasma TG levels. The VLDL(1) subfraction accounted for 34%, 43%, and 52% of total CE transferred from HDL to TG-rich lipoproteins in patients from G1, G2, and G3, respectively. Finally, dense LDL acquired an average of 45% of total CE transferred from HDL to LDL in type 2 diabetes patients. In conclusion, CETP contributes significantly to the formation of small dense LDL particles in type 2 diabetes by a preferential CE transfer from HDL to small dense LDL, as well as through an indirect mechanism involving an enhanced CE transfer from HDL to VLDL(1), the specific precursors of small dense LDL particles in plasma.

Genetic polymorphisms and activity of cholesterol ester transfer protein (CETP): should we be measuring them?

Cholesteryl ester transfer protein (CETP) is a plasma glycoprotein that mediates the transfer of cholesteryl ester from high density lipoproteins (HDL) to triglyceride-rich lipoproteins in exchange for triglycerides. Several approaches are currently being used in research laboratories to measure its activity and/or mass. However, these assays are not standardized and it is not possible to compare data from different laboratories. Also, we lack enough information to assess the value of this variable as a coronary heart disease (CHD) predictor. Several genetic variants at CETP locus have been identified and they have been generally associated with increased HDL-cholesterol concentrations. However, there is no consensus about the association of this CETP-related increase in HDL-cholesterol and protection against CHD. Nevertheless, the most recent evidence from the common CETP-TaqI-B polymorphism shows that the lower CETP activity associated with the presence of this polymorphism decreases CHD risk in men. Based on this and previous evidence, there has been an interest in the development of CETP inhibitors as a tool to increase HOL-cholesterol, thus reducing CHD risk. However, it should be noted that the evidence about the cardioprotective role of these drugs is not yet available.

Inefficiency of insulin therapy to correct apolipoprotein A-I metabolic abnormalities in non-insulin-dependent diabetes mellitus

Non-insulin-dependent diabetes mellitus (NIDDM) is associated with low high density lipoprotein (HDL) cholesterol and apoA-I, related to an increased apoA-I fractional catabolic rate. This stable isotope kinetic experiment, using L-[1-(13)C] leucine, was designed to study the effect of insulin therapy on HDL apoA-I and A-II metabolism in poorly controlled NIDDM patients. A kinetic study was performed in five control subjects and in six NIDDM patients before and two months after the introduction of insulin therapy. ApoA-I and A-II were modelled using a monoexponential function. Insulin treatment was able to correct neither the low HDL apoA-I concentration observed in NIDDM patients (1.14+/-0.19 vs. 1.16+/-0. 12 g l(-1) (controls: 1.33+/-0.14)), nor the HDL apoA-I hypercatabolism (0.39+/-0.11 vs. 0.34+/-0.05 pool d(-1), (controls: 0.23+/-0.01, P< 0.01)). HDL apoA-I production rate was increased in NIDDM patients compared to control subjects and was not modified by insulin (0.45+/-0.12 vs. 0.39+/-0.08 g d(-1) l(-1), (controls: 0. 31+/-0.04, P< 0.05)). HDL apoA-II kinetic parameters were initially not significantly different between NIDDM patients and control subjects, and were not modified by insulin. The decreased insulin sensitivity, assessed by the insulin suppressive test, was not modified by insulin therapy in NIDDM patients. HDL apoA-I fractional catabolic rate was significantly correlated to HDL triglyceride/cholesteryl ester and triglyceride/protein ratios, which were significantly higher in NIDDM patients than in controls and were not modified by insulin therapy. The persistence of insulin resistance and of high neutral lipid exchanges between triglyceride rich lipoproteins and HDL in insulin-treated NIDDM patients probably explain the inefficiency of insulin therapy to correct HDL apoA-I metabolic abnormalities.

Reverse cholesterol transport in diabetes mellitus

There are epidemiological data and experimental animal models relating the development of premature atherosclerosis with defects of the reverse cholesterol transport (RCT) system. In this regard, the plasma concentrations of the high density lipoprotein (HDL) subfractions, of cholesteryl ester transfer protein (CETP), as well as the activity of the enzyme lecithin-cholesterol acyl transferase (LCAT) play critical roles. However, there has been plenty of evidence that atherosclerosis in diabetes mellitus (DM) is ascribed to a greater arterial wall cell uptake of modified apoB-containing lipoproteins whereas a primary or predominant defect of the RCT system is still a subject of debate. In other words, in spite of the fact that in DM the composition and rates of metabolism of the HDL particles are greatly altered and display a diminished in vitro efficiency to remove cell cholesterol, definitive in vivo demonstration of the importance of this fact in atherogenesis is lacking. Furthermore, the roles played by LCAT and CETP in RCT in DM are difficult to interpret because the in vitro procedures of measurement utilized have either been inadequate, or inappropriately interpreted. Knock-out or transgenic mice are much needed models to investigate the roles of LCAT, CETP, phospholipid transfer protein (PLTP), and of a CETP inhibitor in the development of atherosclerosis of experimental DM.

Lipoproteins and low-dose estradiol replacement therapy in post-menopausal Type 2 diabetic patients: the effect of addition of norethisterone acetate

AIMS

Low-dose continuous oestrogen/progestogen may increase patient compliance long-term but the cardioprotective effects in diabetes are unknown. The aim of this study was to compare the effect of low-dose oral oestrogen (1 mg, 17-beta-estradiol) treatment with oestrogen (1 mg 17-beta-estradiol) in combination with low-dose (0.5 mg) continuous norethisterone acetate (NETA) on lipoproteins in Type 2 diabetic patients.

METHODS

Thirty-four post-menopausal Type 2 diabetic patients in moderate control (mean haemoglobin A1c 7.7%) who had a serum oestradiol level of < 50 pg/ml were examined over a 6-month period. Serum lipids, and lipoprotein composition of very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL) were measured. Serum lipoprotein(a) was determined by an ELISA method, LDL fatty acids by gas-liquid chromatography and LDL oxidizability by thiobarbituric acid reactive substances (TBARS assay). Cholesteryl ester transfer protein (CETP), and cell cholesterol were measured.

RESULTS

There was a reduction in serum cholesterol on both treatments but no significant difference between treatment groups. LDL cholesterol decreased by 17% in each group. There was a no significant difference between the groups in serum VLDL or HDL cholesterol or serum triglycerides during the study. The change in lipoprotein(a) during the study was not significantly different between the groups. There was no significant difference in 4 h LDL oxidizability between groups. Although CETP increased with time in both groups there was no significant difference in the change between the groups.

CONCLUSION

In this small study, the addition of continuous low-dose NETA did not reduce the potentially beneficial effects of low-dose 17-beta-estradiol on the progression of atherosclerosis in diabetes.

Improved metabolic control reduces the number of postprandial apolipoprotein B-48-containing particles in type 2 diabetes

Postprandial lipoproteins are raised in diabetes and there is increasing evidence for the atherogenicity of the chylomicron remnant. Increased postprandial cholesteryl ester transfer has also been demonstrated in diabetes and may contribute to the atherogenic lipoprotein profile. The present study examined the effect of improving metabolic control on postprandial lipoproteins in 13 Type 2 diabetic patients. Blood was taken fasting and at 2-h intervals following a high fat, 1100 kcal meal. Patients were brought into good control by intensified dietary advice and oral hyperglycaemic agents or insulin if blood glucose failed to respond. Fasting and postprandial cholesteryl ester transfer protein (CETP) and lecithin:cholesteryl acyltransferase (LCAT) were determined in six patients. Lipoproteins were isolated by sequential ultracentrifugation. Chylomicron and very low density lipoprotein (VLDL) apolipoprotein B-48 and apolipoprotein B-100 were isolated by polyacrylamide gradient gel electrophoresis and quantified by densitometric scanning. CETP and LCAT were determined by an endogenous method which determined cholesterol esterification and transfer between the patients' lipoproteins. There was a significant reduction in postprandial chylomicron apo B-48 (P<0.005), apo B-100 (P<0.0005) and chylomicron cholesterol (P<0.001) following improved diabetic control. The chylomicron lipid/apo B ratio increased with improved control (P<0.01). Postprandial CETP and LCAT were significantly reduced in good control (P<0.01 and P<0.05, respectively) and there were significant changes in HDL composition. The study shows that improvement in metabolic control in Type 2 diabetic patients leads to a reduction in postprandial chylomicron particles and less transfer of cholesterol to apo B-containing lipoproteins.

Plasma cholesteryl ester transfer protein concentration, high-density lipoprotein cholesterol esterification and transfer rates to lighter density lipoproteins in the fasting state and after a test meal are similar in Type II diabetics and normal controls

Rates of ester formation from [3H]cholesterol and of [3H]cholesteryl ester transfer from the HDL-containing plasma fraction to lipoproteins of lighter densities (apo B-containing LP) and plasma cholesteryl ester transfer protein concentration (CETP) were measured in normotriglyceridemic Type II diabetics (n = 11) and normal controls (n = 10) both in the fasting state and 4 h after a standard milk-shake test meal (50g of fat/m of body surface). The percent of [3H]cholesteryl ester synthesis was measured in a plasma [3H]cholesterol-HDL containing preparation incubated for 30 min and the [3H]cholesteryl ester transfer was measured upon precipitation of apo B-containing lipoproteins with dextran sulphate/MgCl2 following a 2 h period of plasma incubation with [3H]cholesteryl ester-HDL. The test meal significantly increased the plasma triglyceride concentration and to a similar extent in diabetics and in normal controls. Both a HDL-[3H]cholesteryl ester synthesis and transfer rates were equally stimulated in diabetics and in controls. When data were expressed by the concentration of plasma triglycerides, cholesteryl ester formation and transfer rates were similar in the alimentary and fasting periods, and when expressed per apo B concentration, cholesteryl ester transfer rates rose during the alimentary period in both diabetics and controls indicating that there was a net gain of cholesteryl ester per apo B lipoprotein. Plasma CETP mass, and neutral lipid transfer activity were similar in diabetics and normal controls demonstrating that the reverse transport of cholesterol through the apo B lipoprotein pathway is not altered in normotriglyceridemic Type II diabetics.