Non-HDL cholesterol and apolipoprotein B in the dyslipidemic classification of type 2 diabetic patients

OBJECTIVE: To compare non-HDL cholesterol (HDLc) and apolipoprotein B (apoB) in the identification of nonconventional high-risk dyslipidemic phenotypes in type 2 diabetic patients. RESEARCH DESIGN AND METHODS: Total cholesterol and triglycerides, HDLc, LDL cholesterol, non-HDLc, apolipoprotein B (apoB), and LDL size were determined in 122 type 2 diabetic patients (68% male, aged 59.6 +/- 9.7 years, and HbA(1c) 7.5% [range 5.2-16.0]). They were then classified as normo- and hypertriglyceridemic if their triglyceride concentrations were below/above 2.25 mmol/l, as normo/hyper-non-HDLc if non-HDLc concentrations were below/above 4.13 mmol/l, and as normo- and hyperapoB if apoB concentrations were below/above 0.97 g/l. Both classifications were compared (concordance assessed with the kappa index), and low HDLc and LDL phenotype B were identified in each category. RESULTS: A total of 26 patients were hypertriglyceridemic and 96 were normotriglyceridemic. All hypertriglyceridemic subjects had increased non-HDLc, whereas 24 had increased apoB (kappa= 0.95). In the normotriglyceridemic group, 44 had increased non-HDLc, 68 had increased apoB, and 25 of the 52 patients with normal non-HDLc had increased apoB (kappa= 0.587). Low HDLc and LDL phenotype B were similarly distributed into the equivalent categories. CONCLUSIONS: Non-HDLc and apoB are equivalent risk markers in hypertriglyceridemic patients, but apoB identifies additional patients with high-risk dyslipidemic phenotypes in normotriglyceridemic type 2 diabetic patients.     

Pioglitazone reduces atherogenic dense LDL particles in nondiabetic patients with arterial hypertension: a double-blind,placebo-controlled study

OBJECTIVE: The oral antidiabetic agent pioglitazone improves insulin sensitivity and glycemic control and appears to lower atherogenic dense LDL in type 2 diabetes. Insulin resistance may occur frequently in nondiabetic patients with hypertension. This study is the first to report the effect of pioglitazone on LDL subfractions in normolipidemic, nondiabetic patients with arterial hypertension. RESEARCH DESIGN AND METHODS: We performed a monocentric, double-blind, randomized, parallel-group comparison of 45 mg pioglitazone (n = 26) and a placebo (n = 28), each given once daily for 16 weeks. Fifty-four moderately hypertensive patients (LDL cholesterol, 2.8 +/- 0.8 mmol/l; HDL cholesterol, 1.1 +/- 0.3 mmol/l; triglycerides, 1.4 mmol/l (median; range 0.5-7.1) were studied at baseline and on treatment. RESULTS: At baseline, dense LDLs were elevated (apolipoprotein [apo]B in LDL-5 plus LDL-6 >250 mg/l) in 63% of all patients. Sixteen weeks of treatment with pioglitazone did not significantly change triglycerides, total, LDL, and HDL cholesterol. However, pioglitazone reduced dense LDLs by 22% (P = 0.024). The mean diameter of LDL particles increased from 19.83 +/- 0.30 to 20.13 +/- 0.33 nm (P < 0.001 vs. placebo), whereas the mean LDL density decreased from 1.0384 +/- 0.0024 to 1.0371 +/- 0.0024 kg/l (P = 0.005 vs. placebo). The effect of pioglitazone on LDL size and density was independent of fasting triglycerides and HDL cholesterol at baseline and of changes in fasting triglycerides and HDL cholesterol. CONCLUSIONS: The prevalence of atherogenic dense LDL in nondiabetic, hypertensive patients is similar to patients with type 2 diabetes. Pioglitazone significantly reduces dense LDL independent from fasting triglycerides and HDL cholesterol. The antiatherogenic potential of pioglitazone may thus be greater than that expected from its effects on triglycerides, LDL, and HDL cholesterol alone.     

Elevated remnant-like particle cholesterol and triglyceride levels in diabetic men and women in the Framingham Offspring Study

OBJECTIVE: Remnants of triglyceride-rich lipoproteins are thought to be atherogenic. A new antibody-based assay allows for the isolation of remnant-like particles (RLPs) from plasma or serum, and the subsequent measurement of RLP cholesterol (RLPC) and triglycerides (RLPTGs). We hypothesized that diabetic patients would have higher remnant levels than nondiabetic patients. DESIGN AND METHODS: We compared RLPC and RLPTG levels of diabetic subjects (68 women, 121 men) participating in the Framingham Heart Study with those of nondiabetic subjects (1,499 women, 1,357 men). RESULTS: Mean RLPC values for diabetic women were 106% higher than those for nondiabetic women (0.367 +/- 0.546 mmol/l [14.2 +/- 21.1 mg/dl] vs. 0.179 +/- 0.109 mmol/l [6.9 +/- 4.2 mg/dl]; P < 0.0001), and RLPTG values for diabetic women were 385% higher than those for nondiabetic women (1.089 +/- 2.775 mmol/l [93.1 +/- 245.6 mg/dl] vs. 0.217 +/- 0.235 mmol/l [19.2 +/- 20.8 mg/dl]; P < 0.0001). Similar but less striking differences were observed in diabetic men, who had mean RLPC values 28% higher than those seen in nondiabetic men (0.285 +/- 0.261 mmol/l [11.0 +/- 10.1 mg/dl] vs. 0.223 +/- 0.163 mmol/l [8.6 +/- 6.3 mg/dl]; P < 0.001) and mean RLPTG values 70% higher than those seen in nondiabetic men (0.606 +/- 1.019 mmol/l [53.6 +/- 90.2 mg/dl] vs. 0.357 +/- 0.546 mmol/l [31.6 +/- 48.3 mg/dl]; P < 0.001). Moreover, diabetic men and women had significantly higher total triglycerides and lower HDL cholesterol levels than nondiabetic subjects. CONCLUSIONS: The data indicate that RLP particles are elevated in diabetic subjects. To achieve optimal reduction of risk for cardiovascular disease, treatment of elevated RLP values, along with the control of LDL cholesterol levels, should be considered.     

Establishing cut‐off values for apolipoprotein B and non‐HDL‐C according to LDL‐C values in a South European population

Background: Low‐density lipoprotein cholesterol (LDL‐C) remains the primary target of therapy in most strategies of dyslipidaemia management focused on cardiovascular disease prevention. Different guidelines have identified specific LDL‐C cut‐off points as targets for therapeutic intervention. Many clinical situations characterised by dyslipidaemia and elevated triglycerides are common in our environment and in overall industrialised countries. Thus, lipid goals based only on LDL‐C could misclassify an important percentage of subjects. The objective of the present study was to establish cut‐off point values for apoB and non‐HDL‐C in relation to the identified LDL‐C cut‐off points for cardiovascular risk in a South European population. Methods: We performed a cross‐sectional study including 1501 subjects (770 women and 731 men) between 18 and 80 years of age. Samples were collected after 12–14 h of fasting. Cholesterol, HDL‐C, triglycerides and apoB levels were measured using direct methods. LDL‐C was calculated by the Friedewald formula. Non‐HDL‐C was calculated as total cholesterol minus HDL‐C. Results: The Spearman’s rank correlations between apoB and LDL‐C (r 0.86, p < 0.0001), and between apoB and non‐HDL‐C (r 0.91, p < 0.0001) were both significant. The proposed cut‐off points for apoB, according to LDL‐C goals (70, 100, 130 and 160 mg/dl) in our population are 70, 80, 100 and 115 mg/dl respectively. The proposed cut‐off values for non‐HDL‐C are 100, 120, 150 and 190 mg/dl respectively. Conclusion: The established LDL‐C cut‐off values could not be accurate to estimate cardiovascular risk in subjects with mild hypertriglyceridaemia, as frequently occurs in our Mediterranean population. To take into consideration the burden of atherogenic particles and better classify patients at risk we propose cut‐off values for apoB or the equivalent for non‐HDL‐C. Prospective trials including cardiovascular variables are needed to validate our assumption.     

Lipid and blood pressure treatment goals for type 1 diabetes: 10-year incidence data from the Pittsburgh Epidemiology of Diabetes Complications Study

OBJECTIVE--Subjects with type 1 diabetes are at high risk for many long-term complications, including early mortality and coronary artery disease (CAD). Few data are available on which to base goal levels for two major risk factors, namely blood pressure and lipid/lipoproteins. The objective of this study was to determine at which levels of LDL and HDL cholesterol, triglycerides, and blood pressure the relative risks of type 1 diabetic complications increase significantly. RESEARCH DESIGN AND METHODS--Observational prospective study of 589 patients with childhood-onset type 1 diabetes (<17 years) aged > or =18 years at baseline; 10-year incidence of mortality, CAD, lower-extremity arterial disease, proliferative retinopathy, distal symmetric polyneuropathy, and overt nephropathy. Relative risks were determined using traditional groupings of blood pressure and lipid/lipoproteins, measured at baseline, using the lowest groupings (<100 mg/dl [2.6 mmol/l] LDL cholesterol, <45 mg/dl [1.1 mmol/l] HDL cholesterol, <100 mg/dl [1.1 mmol/l] triglycerides, <110 mmHg systolic blood pressure, and <80 mmHg diastolic blood pressure) as reference. Adjustments for age, sex, and glycemic control were examined. RESULTS--Driven mainly by strong relationships (RR range 1.8-12.1) with mortality, CAD, and overt nephropathy, suggested goal levels are as follows: LDL cholesterol <100 mg/dl (2.6 mmol/l), HDL cholesterol >45 mg/dl (1.1 mmol/l), triglycerides <150 mg/dl (1.7 mmol/l), systolic blood pressure <120 mmHg, and diastolic blood pressure <80 mmHG: Age, sex, and glycemic control had little influence on these goals. CONCLUSIONS--Although observational in nature, these data strongly support the case for vigorous control of lipid levels and blood pressure in patients with type 1 diabetes.     

Dietary fats do not contribute to hyperlipidemia in children and adolescents with type 1 diabetes

OBJECTIVE: To determine the relative influence of diet, metabolic control, and familial factors on lipids in children with type 1 diabetes and control subjects. RESEARCH DESIGN AND METHODS: We assessed fasting serum cholesterol, LDL cholesterol, HDL cholesterol, triglycerides, lipoprotein(a), apolipoprotein (apo)-A1, and apoB in 79 children and adolescents with type 1 diabetes and 61 age- and sex-matched control subjects, together with dietary intakes using a quantitative food frequency questionnaire. RESULTS: Total cholesterol, LDL cholesterol, apoB, HDL cholesterol, and apoA1 were significantly higher in children with diabetes. Children with diabetes had higher percentage energy intake from complex carbohydrates (P = 0.001) and fiber intake (P = 0.02), and they had lower intake of refined sugar (P < 0.001) and percentage energy from saturated fat (P = 0.045) than control subjects. Total cholesterol (beta = 0.43, P < 0.001), LDL cholesterol (beta = 0.4, P < 0.001), and apoB (beta = 0.32, P = 0.006) correlated independently with HbA(1c) but not dietary intake. HDL cholesterol (beta = 0.24, P = 0.05) and apoA1 (beta = 0.32, P = 0.004) correlated independently with HbA(1c), and HDL cholesterol (beta = -0.34, P = 0.009) correlated with percentage energy intake from complex carbohydrates. Triglycerides correlated independently with percentage energy intake from complex carbohydrates (beta = 0.33, P = 0.01) and insulin dose (beta = 0.26, P = 0.04). Subjects with diabetes and elevated LDL (>3.35 mmol/l, >130 mg/dl), for whom dietary therapy would be recommended, had significantly higher HbA(1c) (P = 0.007), but they had higher intake of complex carbohydrates than subjects with LDL cholesterol <3.35 mmol/l. CONCLUSIONS: Lipid abnormalities remain common in children and adolescents with type 1 diabetes who adhere to current dietary recommendations, and they relate to metabolic control but not dietary intake.     

Lipid values in a rural community

In 1987 the population of a rural community in Tyrol aged 20 to 74 years was screened for plasma lipids (cholesterol, HDL cholesterol and triglycerides). The mean cholesterol value was 205.8 mg/dl (5.31 mml/l) in men and 207.9 mg/dl (5.37 mmol/l) in women. These values seem to be the lowest so far recorded for population-based cholesterol values in Austria. This might be partly explained by an intensive risk factor intervention programme which has been implemented in this community throughout the past ten years. HDL cholesterol was significantly higher in women (63.7 mg/dl or 1.64 mmol/l) than in men (51.1 mg/dl or 1.32 mmol/l). The opposite was true for non-fasting triglycerides, with mean values of 186.3 mg/dl (2.1 mmol/l) in men, and 122.1 mg/dl (1.4 mmol/l) in women.     

Suppression of apolipoprotein B production during treatment of cholesteryl ester storage disease with lovastatin. Implications for regulation of apolipoprotein B synthesis.

Cholesteryl ester storage disease (CESD) is characterized by the deficient activity of lysosomal cholesteryl ester (CE) hydrolase, accumulation of LDL-derived CE in lysosomes, and hyperlipidemia. We studied the kinetics of VLDL and LDL apolipoprotein B (apoB), using 125I-VLDL and 131I-LDL, in a 9-yr-old female with CESD and elevated total cholesterol (TC) (271.0 +/- 4.4 mg/dl), triglyceride (TG) (150.0 +/- 7.8 mg/dl), and LDL cholesterol (184.7 +/- 3.4 mg/dl). These studies demonstrated a markedly elevated production rate (PR) of apoB, primarily in LDL, with normal fractional catabolism of apoB in VLDL and LDL. Urine mevalonate levels were elevated, indicative of increased synthesis of endogenous cholesterol. Treatment with lovastatin, a competitive inhibitor of hydroxymethylglutaryl coenzyme A reductase, resulted in significant reductions in TC (196.8 +/- 7.9 mg/dl), TG (100.8 +/- 20.6 mg/dl), and LDL cholesterol (102.0 +/- 10.9 mg/dl). Therapy reduced VLDL apoB PR (5.2 vs. 12.2 mg/kg per d pretreatment) and LDL apoB PR (12.7 vs. 24.2 mg/kg per d pretreatment). Urine mevalonate levels also decreased during therapy. These results indicate that, in CESD, the inability to release free cholesterol from lysosomal CE resulted in elevated synthesis of endogenous cholesterol and increased production of apoB-containing lipoproteins. Lovastatin reduced both the rate of cholesterol synthesis and the secretion of apoB-containing lipoproteins.     

Simvastatin and pravastatin equally improve flow-mediated dilation in males with hypercholesterolemia

BACKGROUND: Both simvastatin and pravastatin have been shown to improve endothelial function in patients with hypercholesterolemia. To our knowledge there has been no comparative study of these two HMG-CoA reductase inhibitors on endothelial dysfunction measured by flow-mediated dilation of the brachial artery in patients with hypercholesterolemia. METHODS: Fourteen middle-aged males with hypercholesterolemia (means +/- SD: total cholesterol 7.03 +/- 0.88 mmol/l, LDL cholesterol 5.02 +/- 0.63 mmol/l, HDL cholesterol 1.3 +/- 0.38 mmol/l and triglycerides 1.47 +/- 0.26 mmol/l) were randomised, after a 6 weeks' run-in phase with AHA step I diet treatment, to 12 weeks' treatment either with simvastatin or pravastatin. Both statins were given in a daily dose of 10 mg for 6 weeks, which was increased to 20 mg daily in patients who did not achieve an LDL-cholesterol goal of < 3.4 mmol/l. Endothelial dysfunction was measured as flow-mediated brachial artery dilation (FMD) using high resolution ultrasound. RESULTS: There were no significant differences between the drugs in reduction of total cholesterol, LDL cholesterol and triglycerides, or elevation of HDL cholesterol. FMD increased in the simvastatin group from 6.8 +/- 3.2 to 12.3 +/- 2.9% (p < 0.03) and in the pravastatin group from 6.3 +/- 4.8 to 13.3 +/- 4.7% (p = 0.001). The improvement in FMD was the same in both groups (p = 0.64) and did not correlate with changes of the lipid parameters measured. CONCLUSIONS: Both simvastatin and pravastatin reduce endothelial dysfunction to the same degree in patients with hypercholesterolemia, independently of changes in lipid parameters.     

High-density lipoproteins in cholesterosis of the gall bladder

The composition of serum high-density lipoproteins (HDL) was studied in 64 patients with polypous cholesterosis (PC). The spectrum of serum lipids in patients with PC was characterized by the lower concentrations of HDL cholesterol (42.0 +/- 2.5 mg/dl; p < 0.05) and higher concentrations of low-density lipoproteins (LDL) cholesterol (169.9 +/- 6.9 mg/dl; p < 0.01) than those in the controls. The decreased HDL cholesterol, or hypoalphacholesterolemia was associated with quantitative changes in HDL phospholipids (PL) (66.48 +/- 3.4; p < 0.01) and with changes in the composition of individual PL by lowering the proportion of lecithin (47.13 +/- 2.19 mg/dl; p < 0.01). It may be suggested that the lower amount of HDL cholesterol is caused by the decreased HDL acception of free cholesterol from the peripheral cell membranes due to the impaired complexation of PL with free cholesterol and associated the altered PL composition of the superficial monolayer of a lipoprotein particle. At the same time the physicochemical changes in Hdl superficial layer are a cause of abnormal free cholesterol esterification and the impaired plunge of esterified cholesterol into the nucleus of a HDL particle, which facilitates the conversion of HDL to LDL and may explain elevated LDL levels in cholesterosis. The findings suggest that serum lipids are involved in the development of cholesterosis.     

Differing associations of lipid and lipoprotein disturbances with the macrovascular and microvascular complications of type 1 diabetes.

OBJECTIVE: Cardiovascular disease (CVD) is increased in patients with type 1 diabetes, but lipid and lipoprotein patterns remain favorable. In contrast, nephropathy is associated with an adverse distribution. We compared the associations and predictive power of lipid and lipoprotein disturbances with these complications. RESEARCH DESIGN AND METHODS: A nested case-control study from the EURODIAB cohort of 140 case subjects with evidence of at least one complication and 84 control subjects with no complications were analyzed. Conventional and unconventional lipid and lipoprotein fractions, including apolipoprotein (apo)-A1, lipoprotein (Lp)-A1, LpA1/A2, apoB, and LDL particle size were measured centrally. RESULTS: CVD was only associated with increased LDL cholesterol (3.6 vs. 3.0 mmol/l, P = 0.02). In contrast, albuminuria was associated with elevated cholesterol, triglyceride, LDL, and apoB and with diminished LDL particle size. No disturbances in HDL and related lipoproteins were noted. In normoalbuminuric patients, CVD was not associated with any significant changes in lipids. CVD in macroalbuminuric patients was associated with increased triglyceride level (2.37 vs. 1.07 mmol/l, P = 0.001; P = 0.02 for CVD/albuminuria interaction) and LDL cholesterol (5.4 vs. 3.3 mmol/l, P = 0.005; P = 0.004 for interaction). Independent associations were observed for total cholesterol and for LDL particle size and albuminuria. CONCLUSIONS: Abnormalities in lipid and lipoprotein disturbances are more closely related to albuminuria than to CVD in patients with type 1 diabetes. Measurement of conventional parameters provide sufficient risk information. ApoB and LDL particle size offer limited extra information. HDL metabolism remains undisturbed in the presence of complications. These changes reflect associations with glycemic control, which is the key to understanding lipid and lipoprotein disturbances.     

A comparison of lipid and glycemic effects of pioglitazone and rosiglitazone in patients with type 2 diabetes and dyslipidemia

OBJECTIVE: Published reports suggest that pioglitazone and rosiglitazone have different effects on lipids in patients with type 2 diabetes. However, these previous studies were either retrospective chart reviews or clinical trials not rigorously controlled for concomitant glucose- and lipid-lowering therapies. This study examines the lipid and glycemic effects of pioglitazone and rosiglitazone. RESEARCH DESIGN AND METHODS: We enrolled subjects with a diagnosis of type 2 diabetes (treated with diet alone or oral monotherapy) and dyslipidemia (not treated with any lipid-lowering agents). After a 4-week placebo washout period, subjects randomly assigned to the pioglitazone arm (n = 400) were treated with 30 mg once daily for 12 weeks followed by 45 mg once daily for an additional 12 weeks, whereas subjects randomly assigned to rosiglitazone (n = 402) were treated with 4 mg once daily followed by 4 mg twice daily for the same intervals. RESULTS: Triglyceride levels were reduced by 51.9 +/- 7.8 mg/dl with pioglitazone, but were increased by 13.1 +/- 7.8 mg/dl with rosiglitazone (P < 0.001 between treatments). Additionally, the increase in HDL cholesterol was greater (5.2 +/- 0.5 vs. 2.4 +/- 0.5 mg/dl; P < 0.001) and the increase in LDL cholesterol was less (12.3 +/- 1.6 vs. 21.3 +/- 1.6 mg/dl; P < 0.001) for pioglitazone compared with rosiglitazone, respectively. LDL particle concentration was reduced with pioglitazone and increased with rosiglitazone (P < 0.001). LDL particle size increased more with pioglitazone (P = 0.005). CONCLUSIONS: Pioglitazone and rosiglitazone have significantly different effects on plasma lipids independent of glycemic control or concomitant lipid-lowering or other antihyperglycemic therapy. Pioglitazone compared with rosiglitazone is associated with significant improvements in triglycerides, HDL cholesterol, LDL particle concentration, and LDL particle size.     

Favorable effects of pioglitazone and metformin compared with gliclazide on lipoprotein subfractions in overweight patients with early type 2 diabetes

OBJECTIVE: To compare effects of different oral hypoglycemic drugs as first-line therapy on lipoprotein subfractions in type 2 diabetes. RESEARCH DESIGN AND METHODS: Sixty overweight type 2 diabetic patients not on lipid-lowering therapy were randomized to metformin, pioglitazone, or gliclazide after a 3-month dietary run-in. Drug doses were uptitrated for 3 months to optimize glycemia and were kept fixed for a further 3 months. LDL subfractions (LDL(1), LDL(2), and LDL(3)) were prepared by density gradient ultracentrifugation at randomization and study end. Triglycerides, cholesterol, total protein, and phospholipids were measured and mass of subfractions calculated. HDL subfractions were prepared by precipitation. The primary end point was change in proportion of LDL as LDL(3). RESULTS: HbA(1c), triglycerides, glucose, and cholesterol were comparable across groups at baseline and over time. LDL(3) mass and the LDL(3)-to-LDL ratio fell with pioglitazone (LDL(3) mass 36.2 to 28.0 mg/dl, P < 0.01; LDL(3)-to-LDL 19.2:13.3%, P < 0.01) and metformin (42.7 to 31.5 mg/dl, P < 0.01; 21.3:16.2%, P < 0.01, respectively) with no change on gliclazide. LDL(3) reductions were associated with reciprocal LDL(1) increases. Changes were independent of BMI, glycemic control, and triglycerides. Total HDL cholesterol increased on pioglitazone (1.28 to 1.36 mmol/l, P = 0.02) but not gliclazide (1.39 to 1.37 mmol/l, P = NS) or metformin (1.26 to 1.18 mmol/l, P = NS), largely due to an HDL(2) increase (0.3 to 0.4 mmol/l, P < 0.05). HDL(3) cholesterol fell on metformin (0.9 to 0.85 mmol/l, P < 0.01). On pioglitazone and metformin, the HDL(2)-to-HDL(3) ratio increased compared with no change on gliclazide. CONCLUSIONS: For the same improvement in glycemic control, pioglitazone and metformin produce favorable changes in HDL and LDL subfractions compared with gliclazide in overweight type 2 diabetic patients. Such changes may be associated with reduced atherosclerosis risk and may inform the choice of initial oral hypoglycemic agent.     

Apolipoprotein(B) identifies dyslipidemic phenotypes associated with cardiovascular risk in normocholesterolemic type 2 diabetic patients.

OBJECTIVE: Apolipoprotein(B) [apo(B)] reflects the total mass of atherogenic particles (VLDL, IDL, and LDL), and its increase is associated with cardiovascular disease independently of LDL cholesterol (LDLc) levels. Apo(B) determination has been recently standardized, but attention to regional reference limits is advisable. Our aim was to analyze the frequency of dyslipidemic phenotypes, including those dependent on increased apo(B) in normocholesterolemic type 2 diabetic patients. RESEARCH DESIGN AND METHODS: A total of 100 consecutively seen type 2 diabetic patients (63 men, 37 women; aged 59 +/- 11 years) were included, after excluding those on lipid-lowering therapy. Apo(B) cutoff (1.1 g/l) was obtained from a group of normolipidemic (47 men, 21 women) control subjects, and LDLc, triglycerides, and HDL cholesterol (HDLc) cutoff points were those from the National Cholesterol Education Program guidelines. LDLc levels were obtained by ultracentrifugation if triglyceride levels were > 3.45 mmol/l; otherwise, they were calculated (Friedwald). Apo(B) levels were measured by immunoturbidimetry. RESULTS: Normocholesterolemia (LDLc < 4.13 mmol/l) appeared in 75 of the 100 patients, of whom 55 were normo- and 20 hypertriglyceridemic. Hyperapolipoprotein(B) [hyperapo(B)] was the most frequent lipid disorder, present in 34 (45%) of the normocholesterolemic patients (22 normo- and 12 hypertriglyceridemic). Low HDLc levels were more prevalent (53%) in patients with hyperapo(B) than in the rest (24%). CONCLUSIONS: Hyperapo(B) was found in almost half of the normocholesterolemic type 2 diabetic patients and was frequently associated with low HDLc levels and hypertriglyceridemia. Thus, given its independent association with cardiovascular disease and that it identifies high-risk phenotypes in normocholesterolemic diabetic patients apo(B) should be used to evaluate the lipidic pattern of these patients.     

Comparison of ultracentrifugation and a precipitation method for high-density lipoprotein cholesterol quantitation in insulin-dependent diabetic patients

We compared sodium phosphotungstic acid and magnesium chloride precipitation method for high-density lipoprotein (HDL) cholesterol quantitation with the ultracentrifugation method in 64 insulin-dependent diabetic patients with plasma triglyceride less than 3 mmol/l. The cholesterol content of HDL after precipitation of very-low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) was 86% +/- 3% of the cholesterol content of HDL (q greater than 1.063) determined after ultracentrifugation at q = 1.063 (1.33 +/- 0.05 mmol/l vs 1.55 +/- 0.06 mmol/l; p less than 0.001). HDL cholesterol determined after precipitation closely correlated to HDL cholesterol determined after ultracentrifugation (r = 0.97; p less than 0.001). The absolute difference between the HDL cholesterol values obtained by the two methods was correlated to HDL cholesterol (ultracentrifugation) (r = 0.75; p less than 0.001), but it was not correlated to VLDL cholesterol, LDL cholesterol, triglyceride, HbA1c, blood glucose or serum albumin. LDL cholesterol calculated by use of Friedewald's formula was 108% +/- 4% of the cholesterol content of LDL (q = 1.019 to 1.063), determined after ultracentrifugation, but the calculated and the ultracentrifugally determined LDL cholesterol values were closely correlated (r = 0.98; p less than 0.001). These results suggest that during sodium phosphotungstic acid and magnesium chloride precipitation of plasma from diabetic patients, a constant fraction of HDL cholesterol is co-precipitated, resulting in a systematic difference in HDL cholesterol quantitation when compared with the ultracentrifugation method.     

Atherogenic forms of dyslipidaemia in women with polycystic ovary syndrome

Objective: Dyslipidaemia is very common in patients with polycystic ovary syndrome (PCOS) but, beyond plasma lipids, atherogenic lipoprotein (Lp) and apolipoprotein (apo) alterations are still ill defined. Design: We measured concentrations of apoB, Lp(a) and small, dense low‐density lipoprotein (LDL) in 42 patients with PCOS [age: 28 ± 7 years, body mass index (BMI): 27 ± 5 kg/m²] vs. 37 age‐ and BMI‐matched healthy controls. Methods: Elevated Lp(a) levels considered were those > 30 mg/dl while elevated apoB concentrations were those > 100 g/l. Results: Polycystic ovary syndrome showed increased triglycerides levels (p = 0.0011) and lower high‐density lipoprotein (HDL)‐cholesterol concentrations (p = 0.0131) while total‐ and LDL cholesterol were similar. PCOS also showed smaller LDL size (p = 0.0005), higher levels of total small, dense LDL (p < 0.0001), higher concentrations of Lp(a), as considered as absolute values (p = 0.0143) and log‐transformed (p = 0.0014), while no differences were found in apoB levels. Elevated Lp(a) concentrations were found in 24% of PCOS, while elevated apoB levels were relatively uncommon (14%). Spearman correlation analysis revealed that Lp(a) concentrations were weakly correlated only with HDL‐cholesterol levels (r = ?0.378, p = 0.0431). In addition, 36% of patients with PCOS with normal plasma lipid profile showed elevated levels of Lp(a), apoB or small, dense LDL. Conclusions: Atherogenic Lp abnormalities may be found in one‐third of women with PCOS who have a normal lipid pattern. Future prospective studies are needed to test to which extent such atherogenic forms of dyslipidaemia may contribute to the increased cardiovascular risk in young women with PCOS.     

LDL resistance to oxidation: effects of lipid phenotype, autologous HDL and alanine

BACKGROUND: Although LDL resistance to copper-induced oxidation is a time-honoured method, how it is modulated by the physiologic variability of lipid phenotype and what influences the protective action of homologous HDL and exogenous alanine is still unclear. METHODS: In 159 subjects without severe dyslipidemias, LDL resistance to copper-induced oxidation (lag phase) was measured under standardised conditions, with alanine and with autologous HDL. RESULTS: Lag phase was normally distributed and averaged 68+/-10 min (range: 40-105 min). Both VLDL-triglycerides (37+/-5, 52+/-7, 59+/-7, 53+/-5 mg/dl, p<0.05) and LDL-triglycerides (27+/-2, 27+/-1, 30+/-2, 35+/-3 mg/dl, p<0.01) increased across quartiles of lag phase. The relative LDL enrichment in triglycerides (triglycerides percent or triglycerides/cholesterol ratio) was strongly related to lag phase (r=0.29 and r=0.31, p<0.0005 for both) independently of age, gender, BMI, and presence of diabetes or hypertension. The protective effect of HDL was variable (+42+/-18 min) and largely dependent on the capacity of HDL to resist oxidation (r=0.69, p<0.0001). Alanine induced a rather constant lag phase prolongation (+32+/-7 min) that was weakly related only to baseline lag phase (r=0.17, p<0.05). CONCLUSIONS: Relative triglyceride abundance protects LDL from ex-vivo oxidation, HDL particles protect LDL mainly through substrate dilution and alanine probably through a direct anti-oxidant effect.     

Microsomal triglyceride transfer protein polymorphisms and lipoprotein levels in type 2 diabetes

BACKGROUND: Microsomal triglyceride transfer protein (MTP) regulates the assembly of chylomicrons in the intestine and very-low-density lipoprotein (VLDL) in the liver. Common polymorphisms have been described that do not affect lipoproteins in non-diabetic subjects. Their effect in diabetes has not been described in a Caucasian population. AIM: To investigate the association of these three common polymorphisms with lipoproteins in type 2 diabetes. METHODS: Eighty-two patients consumed a high-fat test meal. Chylomicron and VLDL apoB48, apoB100, cholesterol, triglycerides and phospholipids were measured fasting, and at 4 and 6 h postprandially. MTP genotyping was performed by PCR-RFLP. RESULTS: Thirty-three subjects were heterozygous for the -493 G/T substitution. These patients had significantly lower LDL cholesterol (3.0 +/- 0.2 vs. 3.5 +/- 0.1 mmol/l, p < 0.02). In the postprandial period, they had higher levels of apoB48 in the VLDL fraction (4 h, 7.0 +/- 1.4 vs. 2.9 +/- 0.4 microg/ml plasma, p < 0.002; 6 h, 6.4 +/- 1.0 vs. 3.5 +/- 0.5 microg/ml plasma, p < 0.05). In the VLDL fraction there was significantly less cholesterol at 4 and 6 h (p < 0.05). The -400 A/T substitution gave very similar lipoprotein results, but there was significant linkage dysequilibrium between the two polymorphisms. No association was found between the -164 T/C polymorphism and either plasma lipids or the postprandial lipid profile. ApoE genotype was also examined, but did not influence the above results. DISCUSSION: The common -493 G/T MTP polymorphism is associated with changes in VLDL and LDL in Type 2 diabetic patients. The importance of the changes in apoB48-containing small particles requires further investigation. The significantly lower LDL cholesterol suggests that this polymorphism may confer protection against atherosclerosis in type 2 diabetes.     

Lipoproteins and apolipoproteins in young nonobese Arab women with NIDDM treated with insulin

The effects of insulin on the lipid values of nonobese non-insulin-dependent diabetic (NIDDM) Arab women requiring insulin was investigated to find whether these patients have the same coronary artery risk factor related to lipid levels. In this study, 55 NIDDM women on insulin therapy (mean age 28 +/- 8.1 yr and duration of disease 5 +/- 1.2 yr) and 70 control subjects (matched for sex, age, and body mass index) were studied for their plasma levels of lipids, lipoproteins, and apolipoproteins. Concentrations of total cholesterol, very-low-density lipoprotein cholesterol, low-density lipoprotein (LDL) cholesterol, triglyceride (TG), LDL TG, high-density lipoprotein triglyceride (HDL TG), phospholipid, glucose, glycosylated hemoglobin (HbAtc), apolipoprotein B (apoB), LDL-apoB, and apoB/apoAl were significantly elevated in diabetic women compared with control subjects. There was no significant change in the levels of apoAll in plasma and lipoprotein fractions. Concentrations of HDL cholesterol (chol), HDL2-chol, HDL3-chol, plasma apoAl, HDL2-apoAl, HDL3-apoAl, and HDL-apoAl were significantly lower in diabetic women than in control subjects. There was no significant correlation between glucose or HbAtc and most of the lipids, lipoprotein lipids, and apolipoproteins measured. Despite normal body weight and insulin therapy, abnormalities in lipids, lipoprotein lipids, and apoB persisted in NIDDM patients compared with control subjects. Our data may favor an enhanced affinity toward atherosclerosis in these patients.     

Abnormal high density lipoproteins in cerebrotendinous xanthomatosis.

The plasma lipoprotein profiles and high density lipoproteins (HDL) were characterized in patients with the genetic disease cerebrotendinous xanthomatosis (CTX). Abnormalities in the HDL may contribute to their increased atherogenesis and excessive deposits of tissue sterols in the presence of low or low-normal concentrations of plasma cholesterol (165 +/- 25 mg/dl) and low density lipoproteins (LDL). The mean HDL-cholesterol concentration in the CTX plasmas was 14.5 +/- 3.2 mg/dl, about one-third the normal value. The low HDL-cholesterol reflects a low concentration and an abnormal lipid composition of the plasma HDL. Relative to normal HDL, the cholesteryl esters are low, free cholesterol and phospholipids essentially normal, and triglycerides increased. The ratio of apoprotein (apo) to total cholesterol in the HDL of CTX was two to three times greater than normal. In the CTX HDL, the ratio of apoAI to apoAII was high, the proportion of apoC low, and a normally minor form of apoAI increased relative to other forms. The HDL in electron micrographs appeared normal morphologically and in particle size. The abnormalities in lipoprotein distribution profile and composition of the plasma HDL result from metabolic defects that are not understood but may be linked to the genetic defect in bile acid synthesis in CTX. As a consequence, it is probable that the normal functions of the HDL, possibly including modulation of LDL-cholesterol uptake and the removal of excess cholesterol from peripheral tissues, are perturbed significantly in this disease.